High natural erosion rates are the backdrop for enhanced anthropogenic soil erosion in the Middle Hills of Nepal

Science.gov (United States)

West, A. J.; Arnold, M.; Aumaître, G.; Bourlès, D. L.; Keddadouche, K.; Bickle, M.; Ojha, T.

2014-08-01

Although agriculturally accelerated soil erosion is implicated in the unsustainable environmental degradation of mountain environments, such as in the Himalaya, the effects of land use can be difficult to quantify in many mountain settings because of the high and variable natural background rates of erosion. In this study, we present new long-term denudation rates, derived from cosmogenic 10Be analysis of quartz in river sediment from the Likhu Khola, a small agricultural river basin in the Middle Hills of central Nepal. Calculated long-term denudation rates, which reflect background natural erosion processes over 1000+ years prior to agricultural intensification, are similar to present-day sediment yields and to soil loss rates from terraces that are well-maintained. Similarity in short- and long-term catchment-wide erosion rates for the Likhu is consistent with data from elsewhere in the Nepal Middle Hills, but contrasts with the very large increases in short-term erosion rates seen in agricultural catchments in other steep mountain settings. Our results suggest that the large sediment fluxes exported from the Likhu and other Middle Hills rivers in the Himalaya are derived in large part from natural processes, rather than from soil erosion as a result of agricultural activity. Because of the high natural background rates, simple comparison of short- and long-term rates may not reveal unsustainable soil degradation, particularly if much of the catchment-scale erosion flux derives from mass wasting. Correcting for the mass wasting contribution in the Likhu implies minimum catchment-averaged soil production rates of ~0.25-0.35 mm yr-1. The deficit between these production rates and soil losses suggests that terraced agriculture in the Likhu may not be associated with a large systematic soil deficit, at least when terraces are well maintained, but that poorly managed terraces, forest and scrubland may lead to rapid depletion of soil resources.

Contrasting Modern and 10Be- derived erosion rates for the Southern Betic Cordillera, Spain

Science.gov (United States)

Bellin, N.; Vanacker, V.; Kubik, P.

2012-04-01

In Europe, Southeast Spain was identified as one of the regions with major treat of desertification in the context of future land use and climate change. During the last years, significant progress has been made to understand spatial patterns of modern erosion rates in these semi-arid degraded environments. Numerous European projects have contributed to the collection of modern erosion data at different spatial scales for Southeast Spain. However, these data are rarely analysed in the context of long-term changes in vegetation, climate and human occupation. In this paper, we present Modern and Holocene denudation rates for small river basins (1 to 10 km2) located in the Spanish Betic Cordillera. Long-term erosion data were derived from cosmogenic nuclide analyses of river-borne sediment. Modern erosion data were quantified through analysis of sediment deposition volumes behind check dams, and represent average erosion rates over the last 10 to 40 years. Modern erosion rates are surprisingly low (mean erosion rate = 0.048 mm y-1; n=36). They indicate that the steep, sparsely vegetated hillslopes in the Betic Cordillera cannot directly be associated with high erosion rates. 10Be -derived erosion rates integrate over the last 37500 to 3500 years, and are roughly of the same magnitude. They range from 0.013 to 0.243 mm y-1 (mean denudation rate = 0.062 mm y-1 ± 0.054; n=20). Our data suggest that the modern erosion rates are similar to the long-term erosion rates in this area. This result is in contrast with the numerous reports on human-accelerated modern erosion rates for Southeast Spain. Interestingly, our new data on long-term erosion rates show a clear spatial pattern, with higher erosion rates in the Sierra Cabrera and lower erosion rates in Sierra de las Estancias, and Sierra Torrecilla. Preliminary geomorphometric analyses suggest that the spatial variation that we observe in long-term erosion rates is related to the gradient in uplift rates of the Betic

77 FR 51706 - Gross Combination Weight Rating (GCWR); Definition

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2012-08-27

... [Docket No. FMCSA-2012-0156] RIN 2126-AB53 Gross Combination Weight Rating (GCWR); Definition AGENCY... combination weight rating'' (GCWR) in our regulations. The definition currently prescribes how the GCWR is... comment, if submitted on behalf of an association, business, labor union, etc.). You may review a Privacy...

Enhancing rates of erosion and uplift through glacial perturbations

Science.gov (United States)

Norton, Kevin; Schlunegger, Fritz; Abbühl, Luca

2010-05-01

Research over the past decade has shown that the pattern of modern rock uplift in the Swiss Alps correlates with both long-term (thermochronometers) and short-term (cosmogenic nuclide-derived denudation rates, sediment loads, lake fills) measures of erosion. This correlation has been attributed alternately to isostatic causes (compensation to erosion and/or glacial unloading) and tectonic forces (ongoing collision and partial delamination). Of these potential driving forces, only isostatic compensation to erosion fits all available structural, geodetic, and flexural models. We explore this uplift-erosion relationship by analyzing river channel steepness for Alpine rivers. Zones of oversteepening, and hence enhanced stream power, are associated with glacial erosion and deposition during LGM and earlier glaciations, resulting in the focusing of erosion into the inner gorges which connect hanging tributary valleys to the main glacial trunk valley. These inner gorges are transient zones in which fluvial and hillslope processes are in the process of re-adjusting this glacially perturbed landscape. Bedrock properties also play a major role in the response time of these adjustments. Glacially generated knickzones are located within 5 km of the trunk stream in the Rhone valley where resistant lithologies dominate (gneiss), whereas the knickzones have migrated as much as 10 km or further in the less resistant rocks (buendnerschists) of the Rhine valley. We suggest that the rock uplift pattern is controlled by surface denudation as set by the glacial-interglacial history of the Alps. Rapid, focused erosion results in rapid rock uplift rates in the Central Swiss Alps, where glaciers were most active. An interesting ramification of this reasoning is that in the absence of glacial perturbation, both rock uplift rates and denudation rates would be substantially lower in this isostatically compensated mountain belt.

Slow Long-Term Erosion Rates of Banks Peninsula, New Zealand

Science.gov (United States)

Dudunake, T.; Nichols, K. K.; Pugsley, E.; Nelson, S.; Colton, J.

2017-12-01

Banks Peninsula, located south of Christchurch, New Zealand, is composed of a multi-aged complex of volcanic centers. The oldest, Lyttelton Volcano is 12 to 10 Ma, and 350 km3. The largest volcano, Akaroa Volcano, is 9 to 8 Ma and 1200 km3. Both of these volcanoes have large embayments (Lyttelton Harbour and Akaroa Harbour) that connect the central volcano (the location of the former volcanic summits) to the ocean. The other eruptive centers, Mt. Herbert ( 9.5 to 8 Ma) and Diamond Harbor (7 to 5.8 Ma), have not eroded to sea level. We used inferred original surfaces and present day topography to calculate the volume of rock eroded from river valleys draining the flanks of Lyttelton (n=11) and Akaroa (n=26) volcanoes and from the large embayments that penetrate the eroding Lyttelton (n=8) and Akaroa (n=25) volcanoes. We used the youngest age of the eruptions as the start of erosion (Lyttelton = 10 Ma and Akaroa = 8 Ma) to determine erosion rates. Preliminary data suggest average erosion rates of 8.2 ± 2.4 m/My (averaged over 10 Ma) on the flanks of Lyttelton Volcano and 12 ± 5.1 m/My (averaged over 8 Ma) on the flanks of Akaroa Volcano. Dating control and formation processes of Lyttelton Harbour and Akaroa Harbour are poorly constrained. The youngest lava flows, Diamond Harbor, are 5.7 Ma and flow into the Lyttelton Harbour embayment. Using endmembers of embayment age for Lyttelton Harbour (10 Ma to 5.7 Ma) the erosion rates range between 18 ± 5.8 m/My and 31 ± 10 m/My. Similarly, the hillslopes of Akaroa Harbour have slow erosion rates (based on endmember ages of 8 Ma and 5.7 Ma) and range between 22 ± 18 and 31 ± 25 m/My. Even the fastest erosion rates on Banks Peninsula are an order of magnitude slower than the erosion rates of other basalt volcanoes in the world's oceans. Using a similar methodology, Tahiti is eroding between 1200 and 2700 m/Ma (Hildenbrand et al., 2008). Other erosion rates, based on sediment yields and water chemistry for La Reunion (400

77 FR 65497 - Gross Combination Weight Rating (GCWR); Definition

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2012-10-29

... [Docket No. FMCSA-2012-0156] RIN 2126-AB53 Gross Combination Weight Rating (GCWR); Definition AGENCY... combination weight rating'' (GCWR) in 49 CFR parts 383 and 390. The DFR would have taken effect on October 26... submitted on behalf of an association, business, labor union, etc.). You may review a Privacy Act notice...

Effects of land use change on soil gross nitrogen transformation rates in subtropical acid soils of Southwest China.

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Xu, Yongbo; Xu, Zhihong

2015-07-01

Land use change affects soil gross nitrogen (N) transformations, but such information is particularly lacking under subtropical conditions. A study was carried out to investigate the potential gross N transformation rates in forest and agricultural (converted from the forest) soils in subtropical China. The simultaneously occurring gross N transformations in soil were quantified by a (15)N tracing study under aerobic conditions. The results showed that change of land use types substantially altered most gross N transformation rates. The gross ammonification and nitrification rates were significantly higher in the agricultural soils than in the forest soils, while the reverse was true for the gross N immobilization rates. The higher total carbon (C) concentrations and C / N ratio in the forest soils relative to the agricultural soils were related to the greater gross N immobilization rates in the forest soils. The lower gross ammonification combined with negligible gross nitrification rates, but much higher gross N immobilization rates in the forest soils than in the agricultural soils suggest that this may be a mechanism to effectively conserve available mineral N in the forest soils through increasing microbial biomass N, the relatively labile organic N. The greater gross nitrification rates and lower gross N immobilization rates in the agricultural soils suggest that conversion of forests to agricultural soils may exert more negative effects on the environment by N loss through NO3 (-) leaching or denitrification (when conditions for denitrification exist).

Measurement of erosion rate by absorption spectroscopy in a Hall thruster

International Nuclear Information System (INIS)

Yamamoto, Naoji; Yokota, Shigeru; Matsui, Makoto; Komurasaki, Kimiya; Arakawa, Yoshihiro

2005-01-01

The erosion rate of a Hall thruster was estimated with the objective of building a real-time erosion rate monitoring system using a 1 kW class anode layer type Hall thruster. This system aids the understanding of the tradeoff between lifetime and performance. To estimate the flux of the sputtered wall material, the number density of the sputtered iron was measured by laser absorption spectroscopy using an absorption line from ground atomic iron at 371.9935 nm. An ultravioletAl x In y Ga (1-x-y) N diode laser was used as the probe. The estimated number density of iron was 1.1x10 16 m -3 , which is reasonable when compared with that measured by duration erosion tests. The relation between estimated erosion rate and magnetic flux density also agreed with that measured by duration erosion tests

Comparing Background and Recent Erosion Rates in Degraded Areas of Southeastern Brazil

Science.gov (United States)

Fernandes, N.; Bierman, P. R.; Sosa-Gonzalez, V.; Rood, D. H.; Fontes, R. L.; Santos, A. C.; Godoy, J. M.; Bhering, S.

2014-12-01

Soil erosion is a major problem in northwestern Rio de Janeiro State where, during the last three centuries, major land-use changes took place, associated with the replacement of the original rainforest by agriculture and grazing. The combination of steep hillslopes, erodible soils, sparse vegetation, natural and human-induced fires, as well as downslope ploughing, led to an increase in surface runoff and surface erosion on soil-mantled hillslopes; together, these actions and responses caused a decline in soil productivity. In order to estimate changes in erosion rates over time, we compared erosion rates measured at different spatial and temporal scales, both background (natural) and short-term (human-induced during last few decades). Background long-term erosion rates were measured using in-situ produced cosmogenic 10Be in the sand fraction quartz of active river channel sediment in four basins in the northwestern portion of Rio de Janeiro State. In these basins, average annual precipitation varies from 1,200 to 1,300 mm, while drainage areas vary from 15 to 7,200 km2. Short-term erosion rates were measured in one of these basins from fallout 210Pb in soil samples collected along a hillslope transect located in an abandoned agriculture field. In this transect, 190 undisturbed soil samples (three replicates) were collected from the surface to 0.50 m depth (5 cm vertical intervals) in six soil pits. 10Be average background, basin-wide, erosion rates in the area are ~ 13 m/My; over the last decades, time-integrated (210Pb) average hillslope erosion rates are around 1450 m/Myr, with maximum values at the steepest portion of convex hillslopes of about 2000 m/Myr. These results suggest that recent hillslope erosion rates are about 2 orders of magnitude above background rates of sediment generation integrated over many millennia. This unsustainable rate of soil loss has severely decreased soil productivity eventually leading to the abandonment of farming activities in

Reassessment of soil erosion on the Chinese loess plateau: were rates overestimated?

Science.gov (United States)

Zhao, Jianlin; Govers, Gerard

2014-05-01

Several studies have estimated regional soil erosion rates (rill and interrill erosion) on the Chinese loess plateau using an erosion model such as the RUSLE (e.g. Fu et al., 2011; Sun et al., 2013). However, the question may be asked whether such estimates are realistic: studies have shown that the use of models for large areas may lead to significant overestimations (Quinton et al., 2010). In this study, soil erosion rates on the Chinese loess plateau were reevaluated by using field measured soil erosion data from erosion plots (216 plots and 1380 plot years) in combination with a careful extrapolation procedure. Data analysis showed that the relationship between slope and erosion rate on arable land could be well described by erosion-slope relationships reported in the literature (Nearing, 1997). The increase of average erosion rate with slope length was clearly degressive, as could be expected from earlier research. However, for plots with permanent vegetation (grassland, shrub, forest) no relationship was found between erosion rates and slope gradient and/or slope length. This is important, as it implies that spatial variations of erosion on permanently vegetated areas cannot be modeled using topographical functions derived from observations on arable land. Application of relationships developed for arable land will lead to a significant overestimation of soil erosion rates. Based on our analysis we estimate the total soil erosion rate in the Chinese Loess plateau averages ca. 6.78 t ha-1 yr-1 for the whole loess plateau, resulting in a total sediment mobilisation of ca. 0.38 Gt yr-1. Erosion rates on arable land average ca. 15.10 t ha-1 yr-1. These estimates are 2 to 3 times lower than previously published estimates. The main reason why previous estimates are likely to be too high is that the values of (R)USLE parameters such as K, P and LS factor were overestimated. Overestimations of the K factor are due to the reliance of nomograph calculations, resulting

High natural erosion rates are the backdrop for present-day soil erosion in the agricultural Middle Hills of Nepal

Science.gov (United States)

West, A. J.; Arnold, M.; AumaItre, G.; Bourles, D. L.; Keddadouche, K.; Bickle, M.; Ojha, T.

2015-07-01

Although agriculturally accelerated soil erosion is implicated in the unsustainable environmental degradation of mountain environments, such as in the Himalaya, the effects of land use can be challenging to quantify in many mountain settings because of the high and variable natural background rates of erosion. In this study, we present new long-term denudation rates, derived from cosmogenic 10Be analysis of quartz in river sediment from the Likhu Khola, a small agricultural river basin in the Middle Hills of central Nepal. Calculated long-term denudation rates, which reflect background natural erosion processes over 1000+ years prior to agricultural intensification, are similar to present-day sediment yields and to soil loss rates from terraces that are well maintained. Similarity in short- and long-term catchment-wide erosion rates for the Likhu is consistent with data from elsewhere in the Nepal Middle Hills but contrasts with the very large increases in short-term erosion rates seen in agricultural catchments in other steep mountain settings. Our results suggest that the large sediment fluxes exported from the Likhu and other Middle Hills rivers in the Himalaya are derived in large part from natural processes, rather than from soil erosion as a result of agricultural activity. Catchment-scale erosional fluxes may be similar over short and long timescales if both are dominated by mass wasting sources such as gullies, landslides, and debris flows (e.g., as is evident in the landslide-dominated Khudi Khola of the Nepal High Himalaya, based on compiled data). As a consequence, simple comparison of catchment-scale fluxes will not necessarily pinpoint land use effects on soils where these are only a small part of the total erosion budget, unless rates of mass wasting are also considered. Estimates of the mass wasting contribution to erosion in the Likhu imply catchment-averaged soil production rates on the order of ~ 0.25-0.35 mm yr-1, though rates of mass wasting are

Metabolic rate and gross efficiency at high work rates in world class and national level sprint skiers.

Science.gov (United States)

Sandbakk, Øyvind; Holmberg, Hans-Christer; Leirdal, Stig; Ettema, Gertjan

2010-06-01

The present study investigated metabolic rate (MR) and gross efficiency (GE) at moderate and high work rates, and the relationships to gross kinematics and physical characteristics in elite cross-country skiers. Eight world class (WC) and eight national level (NL) male sprint cross-country skiers performed three 5-min stages using the skating G3 technique, whilst roller skiing on a treadmill. GE was calculated by dividing work rate by MR. Work rate was calculated as the sum of power against gravity and frictional rolling forces. MR was calculated using gas exchange and blood lactate values. Gross kinematics, i.e. cycle length (CL) and cycle rate (CR) were measured by video analysis. Furthermore, the skiers were tested for time to exhaustion (TTE), peak oxygen uptake (VO(2peak)), and maximal speed (V(max)) on the treadmill, and maximal strength in the laboratory. Individual performance level in sprint skating was determined by FIS points. WC skiers did not differ in aerobic MR, but showed lower anaerobic MR and higher GE than NL skiers at a given speed (all P higher V(max) and TTE (all P better technique and to technique-specific power.

Quantification of short-term erosion rates using the cosmogenic radionuclide 7Be

International Nuclear Information System (INIS)

Jha, Abhinand

2012-12-01

The fallout radionuclides 137 Cs, 210 Pb ex are used widely for obtaining quantitative information on soil erosion and sediment redistribution rates within agricultural landscapes, over several spatial and temporal scales, and they are frequently seen to represent a valuable complement to conventional soil erosion measurement techniques. However, measurements of these radionuclides provide estimates of medium term (i.e. 40-100 years) soil erosion rates. The shorter-term perspective provided by the 7 Be method has the potential to estimate soil erosion rates associated with individual events or short periods. The 7 Be method has become increasingly relevant in an environment impacted by climate change, changing land use and other human activities. The present work establishes a mathematical model based on the physical processes of molecular diffusion and radioactive decay, to study the vertical behaviour of 7 Be in soils. This model was further used to quantify erosion rates for 12 individual erosional events over a period of two years at our study site in Muencheberg, Germany. The scope of the model was explored analytically as well as numerically for Pulselike fallout initial condition, zero concentration initial condition and exponential distribution initial condition. The model was fitted to more than 15 depth distributions and the resulting model parameter, effective diffusion coefficient D, is evaluated. In general diffusion coefficients estimated were of the order of 10 -12 -10 -13 m 2 s -1 for loamy to sandy soil types. Diffusion coefficients estimated for our study site were about 10 -13 m 2 s -1 . The soil analyses indicate that the diffusion coefficient D is not merely a fitting parameter, but is related to the physico-chemical properties of radionuclide transport in soils. The erosion rates estimated at tilled and no-till plots at our study site were between -2 and 0.3±0.5 kg m -2 -2.0±1.4 kg m -2 respectively. The magnitude of erosion rates estimated

Erosion and erosion-corrosion

International Nuclear Information System (INIS)

Isomoto, Yoshinori

2008-01-01

It is very difficult to interpret the technical term of erosion-corrosion' which is sometimes encountered in piping systems of power plants, because of complicated mechanisms and several confusing definitions of erosion-corrosion phenomena. 'FAC (flow accelerated corrosion)' is recently introduced as wall thinning of materials in power plant systems, as a representative of 'erosion-corrosion'. FAC is, however, not necessarily well understood and compared with erosion-corrosion. This paper describes firstly the origin, definition and fundamental understandings of erosion and erosion-corrosion, in order to reconsider and reconfirm the phenomena of erosion, erosion-corrosion and FAC. Next, typical mapping of erosion, corrosion, erosion-corrosion and FAC are introduced in flow velocity and environmental corrosiveness axes. The concept of damage rate in erosion-corrosion is finally discussed, connecting dissolution rate, mass transfer of metal ions in a metal oxide film and film growth. (author)

Testing the control of mineral supply rates on chemical erosion in the Klamath Mountains

Science.gov (United States)

West, N.; Ferrier, K.

2017-12-01

The relationship between rates of chemical erosion and mineral supply is central to many problems in Earth science, including the role of tectonics in the global carbon cycle, nutrient supply to soils and streams via soil production, and lithologic controls on landscape evolution. We aim to test the relationship between mineral supply rates and chemical erosion in the forested uplands of the Klamath mountains, along a latitudinal transect of granodioritic plutons that spans an expected gradient in mineral supply rates associated with the geodynamic response to the migration of the Mendocino Triple Junction. We present 10Be-derived erosion rates and Zr-derived chemical depletion factors, as well as bulk soil and rock geochemistry on 10 ridgetops along the transect to test hypotheses about supply-limited and kinetically-limited chemical erosion. Previous studies in this area, comparing basin-averaged erosion rates and modeled uplift rates, suggest this region may be adjusted to an approximate steady state. Our preliminary results suggest that chemical erosion at these sites is influenced by both mineral supply rates and dissolution kinetics.

ESTIMATION OF THE WANDA GLACIER (SOUTH SHETLANDS SEDIMENT EROSION RATE USING NUMERICAL MODELLING

Directory of Open Access Journals (Sweden)

Kátia Kellem Rosa

2013-09-01

Full Text Available Glacial sediment yield results from glacial erosion and is influenced by several factors including glacial retreat rate, ice flow velocity and thermal regime. This paper estimates the contemporary subglacial erosion rate and sediment yield of Wanda Glacier (King George Island, South Shetlands. This work also examines basal sediment evacuation mechanisms by runoff and glacial erosion processes during the subglacial transport. This is small temperate glacier that has seen retreating for the last decades. In this work, we examine basal sediment evacuation mechanisms by runoff and analyze glacial erosion processes occurring during subglacial transport. The glacial erosion rate at Wanda Glacier, estimated using a numerical model that consider sediment evacuated to outlet streams, ice flow velocity, ice thickness and glacier area, is 1.1 ton m yr-1.

The influence of basal-ice debris on patterns and rates of glacial erosion

Science.gov (United States)

Ugelvig, Sofie V.; Egholm, David L.

2018-05-01

Glaciers have played a key role for shaping much of Earth's high topography during the cold periods of the Late Cenozoic. However, despite of their distinct influence on landscapes, the mechanisms of glacial erosion, and the properties that determine their rate of operation, are still poorly understood. Theoretical models of subglacial erosion generally highlight the influence of basal sliding in setting the pace of erosion, but they also point to a strong influence of other subglacial properties, such as effective bed pressure and basal-ice debris concentration. The latter properties are, however, not easily measured in existing glaciers, and hence their influence cannot readily be confirmed by observations. In order to better connect theoretical models for erosion to measurable properties in glaciers, we used computational landscape evolution experiments to study the expected influence of basal-ice debris concentration for subglacial abrasion at the scale of glaciers. The computational experiments couple the two erosion processes of quarrying and abrasion, and furthermore integrate the flow of ice and transport of debris within the ice, thus allowing for the study of dynamic feedbacks between subglacial erosion and systematic glacier-scale variations in basal-ice debris concentration. The experiments explored several physics-based models for glacial erosion, in combination with different models for basal sliding to elucidate the relationship between sliding speed, erosion rate and basal-ice debris concentration. The results demonstrate how differences in debris concentration can explain large variations in measured rates. The experiments also provide a simple explanation for the observed dependence of glacier-averaged rate of erosion on glacier size: that large glacier uplands feed more debris into their lower-elevation parts, thereby strengthening their erosive power.

Soil Production and Erosion Rates and Processes in Mountainous Landscapes

Science.gov (United States)

Heimsath, A. M.; DiBiase, R. A.; Whipple, K. X.

2012-12-01

We focus here on high-relief, steeply sloped landscapes from the Nepal Himalaya to the San Gabriels of California that are typically thought to be at a critical threshold of soil cover. Observations reveal that, instead, there are significant areas mantled with soil that fit the conceptual framework of a physically mobile layer derived from the underlying parent material with some locally-derived organic content. The extent and persistence of such soils depends on the long-term balance between soil production and erosion despite the perceived discrepancy between high erosion and low soil production rates. We present cosmogenic Be-10-derived soil production and erosion rates that show that soil production increases with catchment-averaged erosion, suggesting a feedback that enhances soil-cover persistence, even in threshold landscapes. Soil production rates do decline systematically with increasing soil thickness, but hint at the potential for separate soil production functions for different erosional regimes. We also show that a process transistion to landslide-dominated erosion results in thinner, patchier soils and rockier topography, but find that there is no sudden transition to bedrock landscapes. Our landslide modeling is combined with a detailed quantification of bedrock exposure for these steep, mountainous landscapes. We also draw an important conclusion connecting the physical processes producing and transporting soil and the chemical processes weathering the parent material by measuring parent material strength across three different field settings. We observe that parent material strength increases with overlying soil thickness and, therefore, the weathered extent of the saprolite. Soil production rates, thus, decrease with increasing parent material competence. These observation highlight the importance of quantifying hillslope hydrologic processes where such multi-facted measurements are made.

Anthropogenic control on geomorphic process rates: can we slow down the erosion rates? (Geomorphology Outstanding Young Scientist Award & Penck Lecture)

Science.gov (United States)

Vanacker, V.

2012-04-01

The surface of the Earth is changing rapidly, largely in response to anthropogenic perturbation. Direct anthropogenic disturbance of natural environments may be much larger in many places than the (projected) indirect effects of climate change. There is now large evidence that humans have significantly altered geomorphic process rates, mainly through changes in vegetation composition, density and cover. While much attention has been given to the impact of vegetation degradation on geomorphic process rates, I suggest that the pathway of restoration is equally important to investigate. First, vegetation recovery after crop abandonment has a rapid and drastic impact on geomorphic process rates. Our data from degraded catchments in the tropical Andes show that erosion rates can be reduced by up to 100 times when increasing the protective vegetation cover. During vegetation restoration, the combined effects of the reduction in surface runoff, sediment production and hydrological connectivity are stronger than the individual effects together. Therefore, changes in erosion and sedimentation during restoration are not simply the reverse of those observed during degradation. Second, anthropogenic perturbation causes a profound but often temporary change in geomorphic process rates. Reconstruction of soil erosion rates in Spain shows us that modern erosion rates in well-vegetated areas are similar to long-term rates, despite evidence of strong pulses in historical erosion rates after vegetation clearance and agriculture. The soil vegetation system might be resilient to short pulses of accelerated erosion (and deposition), as there might exist a dynamic coupling between soil erosion and production also in degraded environments.

Integrating river incision rates over timescales in the Ecuadorian Andes: from uplift history to current erosion rates

Science.gov (United States)

Campforts, Benjamin; Govers, Gerard; Vanacker, Veerle; Tenorio, Gustavo

2013-04-01

River profile development is studied at different timescales, from the response to uplift over millions of years over steady state erosion rates over millennia to the response to a single event, such as a major landslide. At present, few attempts have been made to compare data obtained over various timescales. Therefore we do not know to what extent data and model results are compatible: do long-term river profile development models yield erosion rates that are compatible with information obtained over shorter time spans, both in terms of absolute rates and spatial patterns or not? Such comparisons could provide crucial insights into the nature of river development and allow us to assess the confidence we may have when predicting river response at different timescales (e.g. Kirchner et al., 2001). A major issue hampering such comparison is the uncertainty involved in the calibration of long-term river profile development models. Furthermore, calibration data on different timescales are rarely available for a specific region. In this research, we set up a river profile development model similar to the one used by Roberts & White (2010) and successfully calibrated it for the northern Ecuadorian Andes using detailed uplift and sedimentological data. Subsequently we used the calibrated model to simulate river profile development in the southern Ecuadorian Andes. The calibrated model allows to reconstruct the Andean uplift history in southern Ecuador, which is characterized by a very strong uplift phase during the last 5 My. Erosion rates derived from the modeled river incision rates were then compared with 10Be derived basin-wide erosion rates for a series of basins within the study area. We found that the model-inferred erosion rates for the last millennia are broadly compatible with the cosmogenic derived denudation rates, both in terms of absolute erosion rates as well as in terms of their spatial distribution. Hence, a relatively simple river profile development

In-situ real time measurements of net erosion rates of copper during hydrogen plasma exposure

Science.gov (United States)

Kesler, Leigh; Wright, Graham; Peterson, Ethan; Whyte, Dennis

2013-10-01

In order to properly understand the dynamics of net erosion/deposition in fusion reactors, such as tokamaks, a diagnostic measuring the real time rates of net erosion/deposition during plasma exposure is necessary. The DIONISOS experiment produces real time measurements of net erosion/deposition by using Rutherford backscattering spectroscopy (RBS) ion beam analysis simultaneously with plasma exposure from a helicon plasma source. This in-situ method improves on ex-situ weight loss measurements by allowing measurement of possible synergistic effects of high ion implantation rates and net erosion rate and by giving a real time response to changes in plasma parameters. Previous work has validated this new technique for measuring copper (Cu) erosion from helium (He) plasma ion bombardment. This technique is now extended to measure copper erosion due to deuterium and hydrogen plasma ion exposure. Targets used were a 1.5 μm Cu layer on an aluminum substrate. Cu layer thickness is tracked in real time using 1.2 MeV proton RBS. Measured erosion rates will be compared to results from literature and He erosion rates. Supported by US DoE award DE-SC00-02060.

Charge-exchange wall physical erosion rates for a proposed INTOR/FED limiter

International Nuclear Information System (INIS)

Heifetz, D.; Schmidt, J.; Ulrickson, M.; Post, D.

1983-01-01

We have analyzed power deposition and physical erosion rates on the first wall and limiter due to charge-exchange neutrals in a proposed pump limiter design for the INTOR/FED tokamak. Plasma conditions were modeled using the one-dimensional plasma transport code baldur. Neutral transport was modeled using a two-dimensional, multispecies Monte Carlo algorithm. No chemical erosion or wall redeposition processes were included. Two possible plasma discharges with different edge densities and temperatures were modeled, a regime with T/sub e/ approx.300 eV and napprox.5 x 10 12 cm - 3 , and a hotter, less dense edge regime produced with pellet fueling. We found that the erosion of the stainless steel vacuum vessel wall was highly localized in each case to the two points just beyond the limiter tips, and to the point directly across from the neutralizer plate, with peak erosion rates approx.2 cm/yr, assuming a 40% duty cycle. The erosion of a carbon limiter, neglecting redeposition and chemical erosion, varied in the two cases from 1.6--4 cm/yr, for the same duty cycle. The hotter, less dense discharge produced less sputtering. However achieving truly tolerable physical sputtering rates may require a very low edge temperature, plasma

Rate estimates for lateral bedrock erosion based on radiocarbon ages, Duck River, Tennessee

International Nuclear Information System (INIS)

Brakenridge, G.R.

1985-01-01

Rates of bedrock erosion in ingrown meandering rivers can be inferred from the location of buried relict flood-plain and river-bank surfaces, associated paleosols, and radiocarbon dates. Two independent methods are used to evaluate the long-term rates of limestone bedrock erosion by the Duck River. Radiocarbon dates on samples retrieved from buried Holocene flood-plain and bank surfaces indicate lateral migration of the river bank at average rates of 0.6-1.9 m/100 yr. Such rates agree with lateral bedrock cliff erosion rates of 0.5-1.4 m/100 yr, as determined from a comparison of late Pleistocene and modern bedrock cliff and terrace scarp positions. These results show that lateral bedrock erosion by this river could have occurred coevally with flood-plain and terrace formation and that the resulting evolution of valley meander bends carved into bedrock is similar in many respects to that of channel meanders cut into alluvium. 11 references, 5 figures

Quantification of short-term erosion rates using the cosmogenic radionuclide {sup 7}Be

Energy Technology Data Exchange (ETDEWEB)

Jha, Abhinand

2012-12-15

The fallout radionuclides {sup 137}Cs, {sup 210}Pb{sub ex} are used widely for obtaining quantitative information on soil erosion and sediment redistribution rates within agricultural landscapes, over several spatial and temporal scales, and they are frequently seen to represent a valuable complement to conventional soil erosion measurement techniques. However, measurements of these radionuclides provide estimates of medium term (i.e. 40-100 years) soil erosion rates. The shorter-term perspective provided by the {sup 7}Be method has the potential to estimate soil erosion rates associated with individual events or short periods. The {sup 7}Be method has become increasingly relevant in an environment impacted by climate change, changing land use and other human activities. The present work establishes a mathematical model based on the physical processes of molecular diffusion and radioactive decay, to study the vertical behaviour of {sup 7}Be in soils. This model was further used to quantify erosion rates for 12 individual erosional events over a period of two years at our study site in Muencheberg, Germany. The scope of the model was explored analytically as well as numerically for Pulselike fallout initial condition, zero concentration initial condition and exponential distribution initial condition. The model was fitted to more than 15 depth distributions and the resulting model parameter, effective diffusion coefficient D, is evaluated. In general diffusion coefficients estimated were of the order of 10{sup -12}-10{sup -13} m{sup 2} s{sup -1} for loamy to sandy soil types. Diffusion coefficients estimated for our study site were about 10{sup -13} m{sup 2}s{sup -1}. The soil analyses indicate that the diffusion coefficient D is not merely a fitting parameter, but is related to the physico-chemical properties of radionuclide transport in soils. The erosion rates estimated at tilled and no-till plots at our study site were between <0.001-4.7{+-}0.4 kg m{sup -2} and

ESTIMATION OF THE WANDA GLACIER (SOUTH SHETLANDS) SEDIMENT EROSION RATE USING NUMERICAL MODELLING

OpenAIRE

Kátia Kellem Rosa; Rosemary Vieira; Jefferson Cardia Simões

2013-01-01

Glacial sediment yield results from glacial erosion and is influenced by several factors including glacial retreat rate, ice flow velocity and thermal regime. This paper estimates the contemporary subglacial erosion rate and sediment yield of Wanda Glacier (King George Island, South Shetlands). This work also examines basal sediment evacuation mechanisms by runoff and glacial erosion processes during the subglacial transport. This is small temperate glacier that has seen retreating for the l...

A 30000 yr record of erosion rates from cosmogenic 10Be in middle European river terraces

NARCIS (Netherlands)

Schaller, M.; Blanckenburg, von F.; Veldkamp, A.; Tebbens, L.A.; Hovius, N.; Kubik, P.W.

2002-01-01

Cosmogenic 10Be in river-borne quartz sand records a time-integrated erosion rate representative of an entire drainage basin. When sequestered in a terrace of known age, paleo-erosion rates may be recovered from the nuclide content of the terrace material. Paleo-erosion rates between 30 and 80

Erosion rates across space and timescales from a multi-proxy study of rivers of eastern Taiwan

Science.gov (United States)

Fellin, Maria Giuditta; Chen, Chia-Yu; Willett, Sean D.; Christl, Marcus; Chen, Yue-Gau

2017-10-01

We derive erosion rates from detrital zircon fission-track ages and cosmogenic nuclide concentrations from sediments from the modern rivers of eastern Taiwan in order to investigate how surface erosional processes vary in space and time across the young arc-continent collisional orogen of Taiwan. Taiwan is characterized by rapid rates of exhumation, a fluvial and landslide-dominated landscape, high seismicity, high relief and frequent typhoons. The obliquity between the convergence direction and the trend of the plate boundary provides a gradient in uplift and variations in longevity of orogenic activity with a young, immature orogen in the south, a mature orogen in central and northern Taiwan, and perhaps even the cessation of orogeny in the far north. The modern zircon fission-track detrital record is consistent with basement ages that show that much of the orogen is eroding at high rates with basin-wide mean zircon fission-track cooling ages as young as 0.9 Ma. The erosion rates derived from concentrations of cosmogenic nuclides (10Be) provide erosion rates averaged over much shorter timescales, but these two proxies provide estimates of erosion rates that are within error of each other across most of the collisional belt. Erosion rates are lowest in the immature zone of the orogen (Taiwan, and increase to values ≥ 4 km/Ma in central Taiwan. Geomorphic indices, in particular channel steepness, are also correlated with erosion rates, suggesting that fluvial erosion is the dominant exhumation process and that landscape evolution is reacting primarily to tectonic forcing, fast enough to keep the landscape in a state of quasi-equilibrium where erosion rates and rock uplift rates are nearly equal. We find no measurable effects due to rock erodibility or precipitation rate, but if these parameters co-vary with tectonic uplift rate, our data could not resolve the influence of each.

Experimental comparison of cavitation erosion rates of different steels used in hydraulic turbines

International Nuclear Information System (INIS)

Ton-That, L

2010-01-01

The prediction of cavitation erosion rates has an important role in order to evaluate the exact life of components in fluid machineries. Hydro-Quebec has studied this phenomenon for several years, in particular in hydraulic turbine runners, to try to understand the different degradation mechanisms related to this phenomenon. This paper presents part of this work. In this study, we carried out experimental erosion tests to compare different steels used in actual hydraulic turbine runners (carbon steels, austenitic and martensitic stainless steels) to high strength steels in terms of cavitation erosion resistance. The results for these different classes of steels are presented. The tests have been performed in a cavitating liquid jet apparatus according to the ASTM G134-95 standard to simulate the flow conditions. The mass loss has been followed during the exposure time. The maximum depth of erosion, the mean depth of erosion, and the mean depth erosion rate are determined. As a result we found that ASTM-A514 high strength steels present excellent cavitation erosion resistance properties. The cavitation eroded surface is followed by optical profilometry technique. Determination of mechanical properties and examinations of the eroded surfaces of the samples have also been carried out in order to identify the erosion mechanisms involved in the degradation of these kinds of materials.

Evaluation of rate of swelling and erosion of verapamil (VRP) sustained-release matrix tablets.

Science.gov (United States)

Khamanga, Sandile M; Walker, Roderick B

2006-01-01

Tablets manufactured in-house were compared to a marketed sustained-release product of verapamil to investigate the rate of hydration, erosion, and drug-release mechanism by measuring the wet and subsequent dry weights of the products. Swelling and erosion rates depended on the polymer and granulating fluid used, which ultimately pointed to their permeability characteristics. Erosion rate of the marketed product was highest, which suggests that the gel layer that formed around these tablets was weak as opposed to the robust and resistant layers of test products. Anomalous and near zero-order transport mechanisms were dominant in tests and commercial product, respectively.

Effects of landforms on the erosion rate in a small watershed by the 137Cs tracing method

International Nuclear Information System (INIS)

Li Mian; Yao Wenyi; Li Zhanbin; Liu Puling; Shen Zhenzhou

2010-01-01

It's very important to analyze and evaluate quantitatively the effects of landforms on soil erosion for the prevention and treatment of soil loss in a small watershed. The objective of this study was to evaluate the effects of landform factors on erosion rate by the 137 Cs tracing method in a small watershed in the Purple Hilly Area of China. The erosion rates under different slope lengths, slope gradients and slope aspects were estimated in Xiangshuitan watershed in the Purple Hilly Area in Sichuan Basin by the 137 Cs tracing method. The results showed that the erosion rate decreased exponentially with downslope distance, and it increased with increasing slope gradient during the scope of 5 deg. - 16 deg. The slope aspect had great impact on the erosion rate, and the hillside on the sunny slope had larger erosion rate than that on the shady slope, particularly for the farmland.

Covariation of climate and long-term erosion rates acrossa steep rainfall gradient on the Hawaiian island of Kaua'i

Science.gov (United States)

Ken Ferrier,; J. Taylor Perron,; Sujoy Mukhopadhyay,; Matt Rosener,; Stock, Jonathan; Slosberg, Michelle; Kimberly L. Huppert,

2013-01-01

Erosion of volcanic ocean islands creates dramatic landscapes, modulates Earth’s carbon cycle, and delivers sediment to coasts and reefs. Because many volcanic islands have large climate gradients and minimal variations in lithology and tectonic history, they are excellent natural laboratories for studying climatic effects on the evolution of topography. Despite concerns that modern sediment fluxes to island coasts may exceed long-term fluxes, little is known about how erosion rates and processes vary across island interiors, how erosion rates are influenced by the strong climate gradients on many islands, and how modern island erosion rates compare to long-term rates. Here, we present new measurements of erosion rates over 5 yr to 5 m.y. timescales on the Hawaiian island of Kaua‘i, across which mean annual precipitation ranges from 0.5 to 9.5 m/yr. Eroded rock volumes from basins across Kaua‘i indicate that million-year-scale erosion rates are correlated with modern mean annual precipitation and range from 8 to 335 t km–2 yr–1. In Kaua‘i’s Hanalei River basin, 3He concentrations in detrital olivines imply millennial-scale erosion rates of >126 to >390 t km–2 yr–1 from olivine-bearing hillslopes, while fluvial suspended sediment fluxes measured from 2004 to 2009 plus estimates of chemical and bed-load fluxes imply basin-averaged erosion rates of 545 ± 128 t km–2 yr–1. Mapping of landslide scars in satellite imagery of the Hanalei basin from 2004 and 2010 implies landslide-driven erosion rates of 30–47 t km–2 yr–1. These measurements imply that modern erosion rates in the Hanalei basin are no more than 2.3 ± 0.6 times faster than millennial-scale erosion rates, and, to the extent that modern precipitation patterns resemble long-term patterns, they are consistent with a link between precipitation rates and long-term erosion rates.

An assessment for the erosion rate of DEMO first wall

Science.gov (United States)

Tokar, M. Z.

2018-01-01

In a fusion reactor a significant fraction of plasma particles lost from the confined volume will reach the vessel wall. The recombination of these charged species, electrons and ions of hydrogen isotopes, is a source of neutral molecules and atoms, recycling back into the plasma. Here they participate, in particular, in charge-exchange (c-x) collisions with the plasma ions and, as a result, atoms of high energies with chaotically oriented velocities are generated. A significant fraction of these hot neutrals will hit the wall, leading, as well as the outflowing fuel and impurity ions, to its erosion, limiting the reactor operation time. The rate of the wall erosion in DEMO is assessed by applying a one-dimensional model which takes into account the transport of charged and neutral species across the flux surfaces in the main part of the scrape-off layer, beyond the X-point vicinity and divertor, and by considering the shift of the centers of flux surfaces, their elongation and triangularity. Atoms generated by c-x of recycling neutrals are modeled kinetically to define firmly their energy spectrum, being of particular importance for the erosion assessment. It is demonstrated the erosion rate of the DEMO wall armor of tungsten will have a pronounced ballooning character with a significant maximum of 0.3 mm per full power year at the low field side, decreasing with an increase in the anomalous perpendicular transport in the ‘far’ SOL or the plasma density at the separatrix.

Constraining local subglacial bedrock erosion rates with cosmogenic nuclides

Science.gov (United States)

Wirsig, Christian; Ivy-Ochs, Susan; Christl, Marcus; Reitner, Jürgen; Reindl, Martin; Bichler, Mathias; Vockenhuber, Christof; Akcar, Naki; Schlüchter, Christian

2014-05-01

The constant buildup of cosmogenic nuclides, most prominently 10Be, in exposed rock surfaces is routinely employed for dating various landforms such as landslides or glacial moraines. One fundamental assumption is that no cosmogenic nuclides were initially present in the rock, before the event to be dated. In the context of glacially formed landscapes it is commonly assumed that subglacial erosion of at least a few meters of bedrock during the period of ice coverage is sufficient to remove any previously accumulated nuclides, since the production of 10Be ceases at a depth of 2-3 m. Insufficient subglacial erosion leads to overestimation of surface exposure ages. If the time since the retreat of the glacier is known, however, a discordant concentration of cosmogenic nuclides delivers information about the depth of subglacial erosion. Here we present data from proglacial bedrock at two sites in the Alps. Goldbergkees in the Hohe Tauern National Park in Austria and Gruebengletscher in the Grimsel Pass area in Switzerland. Samples were taken inside as well as outside of the glaciers' Little Ice Age extent. Measured nuclide concentrations are analyzed with the help of a MATLAB model simulating periods of exposure or glacial cover of user-definable length and erosion rates.

Beta-decay rate and beta-delayed neutron emission probability of improved gross theory

Science.gov (United States)

Koura, Hiroyuki

2014-09-01

A theoretical study has been carried out on beta-decay rate and beta-delayed neutron emission probability. The gross theory of the beta decay is based on an idea of the sum rule of the beta-decay strength function, and has succeeded in describing beta-decay half-lives of nuclei overall nuclear mass region. The gross theory includes not only the allowed transition as the Fermi and the Gamow-Teller, but also the first-forbidden transition. In this work, some improvements are introduced as the nuclear shell correction on nuclear level densities and the nuclear deformation for nuclear strength functions, those effects were not included in the original gross theory. The shell energy and the nuclear deformation for unmeasured nuclei are adopted from the KTUY nuclear mass formula, which is based on the spherical-basis method. Considering the properties of the integrated Fermi function, we can roughly categorized energy region of excited-state of a daughter nucleus into three regions: a highly-excited energy region, which fully affect a delayed neutron probability, a middle energy region, which is estimated to contribute the decay heat, and a region neighboring the ground-state, which determines the beta-decay rate. Some results will be given in the presentation. A theoretical study has been carried out on beta-decay rate and beta-delayed neutron emission probability. The gross theory of the beta decay is based on an idea of the sum rule of the beta-decay strength function, and has succeeded in describing beta-decay half-lives of nuclei overall nuclear mass region. The gross theory includes not only the allowed transition as the Fermi and the Gamow-Teller, but also the first-forbidden transition. In this work, some improvements are introduced as the nuclear shell correction on nuclear level densities and the nuclear deformation for nuclear strength functions, those effects were not included in the original gross theory. The shell energy and the nuclear deformation for

Effects of landforms on the erosion rate in a small watershed by the {sup 137}Cs tracing method

Energy Technology Data Exchange (ETDEWEB)

Li Mian, E-mail: hnli-mian@163.co [Yellow River Institute of Hydraulic Research, Key Laboratory of Sediment Research of Yellow River of Ministry of Water Resources, Zhengzhou, Henan 450003 (China); Yao Wenyi [Yellow River Institute of Hydraulic Research, Key Laboratory of Sediment Research of Yellow River of Ministry of Water Resources, Zhengzhou, Henan 450003 (China); Li Zhanbin [Xi' an University of Technology, Xi' an, Shaanxi 710048 (China); Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling, Shaanxi 712100 (China); Liu Puling [Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling, Shaanxi 712100 (China); Shen Zhenzhou [Yellow River Institute of Hydraulic Research, Key Laboratory of Sediment Research of Yellow River of Ministry of Water Resources, Zhengzhou, Henan 450003 (China)

2010-05-15

It's very important to analyze and evaluate quantitatively the effects of landforms on soil erosion for the prevention and treatment of soil loss in a small watershed. The objective of this study was to evaluate the effects of landform factors on erosion rate by the {sup 137}Cs tracing method in a small watershed in the Purple Hilly Area of China. The erosion rates under different slope lengths, slope gradients and slope aspects were estimated in Xiangshuitan watershed in the Purple Hilly Area in Sichuan Basin by the {sup 137}Cs tracing method. The results showed that the erosion rate decreased exponentially with downslope distance, and it increased with increasing slope gradient during the scope of 5 deg. - 16 deg. The slope aspect had great impact on the erosion rate, and the hillside on the sunny slope had larger erosion rate than that on the shady slope, particularly for the farmland.

Modeling the fluid/soil interface erosion in the Hole Erosion Test

Directory of Open Access Journals (Sweden)

Kissi B.

2012-07-01

Full Text Available Soil erosion is a complex phenomenon which yields at its final stage to insidious fluid leakages under the hydraulic infrastructures known as piping and which are the main cause of their rupture. The Hole Erosion Test is commonly used to quantify the rate of piping erosion. In this work, The Hole Erosion Test is modelled by using Fluent software package. The aim is to predict the erosion rate of soil during the hole erosion test. The renormalization group theory – based k–ε turbulence model equations are used. This modelling makes it possible describing the effect of the clay concentration in flowing water on erosion. Unlike the usual one dimensional models, the proposed modelling shows that erosion is not uniform erosion along the hole length. In particular, the concentration of clay is found to increase noticeably the erosion rate.

Comparing erosion rates in burnt forests and agricultural fields for a mountain catchment in NW Iberia

Science.gov (United States)

Nunes, João Pedro; Marisa Santos, Juliana; Bernard-Jannin, Léonard; Keizer, Jan Jacob

2013-04-01

A large part of northwestern Iberia is nowadays covered by commercial forest plantations of eucalypts and maritime pines, which have partly replaced traditional agricultural land-uses. The humid Mediterranean climate, with mild wet winters and warm dry summers, creates favorable conditions for the occurrence of frequent and recurrent forest fires. Erosion rates in recently burnt areas have been the subject of numerous studies; however, there is still a lack of information on their relevance when compared with agricultural erosion rates, impairing a comprehensive assessment of the role of forests for soil protection. This study focuses on Macieira de Alcoba, head-water catchment in the Caramulo Mountain Range, north-central Portugal, with a mixture of agricultural fields (mostly a rotation between winter pastures and summer cereals) on the lower slopes and forest plantations (mostly eucalypts) on the upper slopes. Agricultural erosion in this catchment has been monitored since 2010; a forest fire in 2011 presented an opportunity to compare post-fire and agricultural erosion rates at nearby sites with comparable soil and climatic conditions. Erosion rates were monitored between 2010 and 2013 by repeated surveys of visible erosion features and, in particular, by mapping and measuring rills and gullies after important rainfall events. During the 2011/2012 hydrological year, erosion rates in the burnt forest were two orders of magnitude above those in agricultural fields, amounting to 17.6 and. 0.1 Mg ha-1, respectively. Rills were widespread in the burnt area, while in the agricultural area they were limited to a small number of fields with higher slope; these particular fields experienced an erosion rate of 2.3 Mg ha-1, still one order of magnitude lower than at the burnt forest site. The timing of the erosion features was also quite distinct for the burnt area and the agricultural fields. During the first nine months after the fire, rill formation was not observed in

NM Gross Receipts Baseline

Data.gov (United States)

Earth Data Analysis Center, University of New Mexico — This layer represents boundaries for New Mexico's gross receipts tax districts as identified on the "Gross Receipts Tax Rate Schedule" published by the Taxation and...

Assessing soil erosion rates for a large catchment in the Central Highlands of Vietnam using fallout radionuclides

International Nuclear Information System (INIS)

Phan Son Hai; Nguyen Thanh Binh; Nguyen Minh Dao; Nguyen Thi Huong Lan; Nguyen Thi Mui; Le Xuan Thang; Phan Quang Trung; Trinh Cong Tu; Tran Tien Dung

2014-01-01

Fallout radionuclides Be-7 and Cs-137 were applied to assess soil erosion rates for a 270.5 km 2 catchment with a variety of slope (from 0 o to more than 45 o , crops or vegetation (natural forest, artificial forest, perennial crops, annual crops) and a variety of tillage and soil conservation measures. Soil erosion rates were estimated at 90 areas within the catchment. Each sampling area has at least one feature of the slope, rainfall, crops, farming practice different from others. Soil erosion rates in this region depend significantly on the slope, crops and farming techniques. Averaging over crops, soil erosion rates by slopes 0 - 5 o , 5 - 15 o , 15 - 25 o and 25 - 35 o are 5.0, 12.8, 18.9 and 21.3 t.ha -1 .y -1 , respectively. Forest land has the least soil erosion rates, ranging between 0.5 t.ha -1 .y -1 and 14 t.ha -1 .y -1 depending on the slope. Annual crops land has the highest soil erosion rates, ranging between 6 t.ha -1 .y -1 and 42 t.ha -1 .y -1 when slope varies from < 5 o to 32 o . Perennial crop land has soil erosion rates in the range of 5 t.ha -1 .y -1 and 39 t.ha -1 .y -1 . In areas with the same slope, the soil erosion rate is the highest for cashew plantations, lower for mulberry field and the lowest for tea or coffee plantations. Soil erosion has resulted in losing a significant quantity of plant nutrients such as OM, N, P 2 O 5 and K 2 O every year. Generally, lost nutrient quantities due to soil erosion are proportional to erosion rates. Some areas of annual crop land lost a large amount of nutrients every year, up to 1435 kg OM, 79 kg N, 54 kg P 2 O 5 and 36 kg K 2 O. Similarly, perennial crop lands in this region could lost up to 1736 kg OM, 91 kg N, 66 kg P 2 O 5 and 40 kg K 2 O every year. Owing to soil erosion, the catchment has lost about 211200 tons of surface soil per year during last 50 years, corresponding to the rate of 7.8 t.ha -1 .y -1 . This amount of eroded soil was deposited in drainage of the catchment and in reservoirs

Quantifying modern erosion rates and river-sediment contamination in the Bolivian Andes

Science.gov (United States)

Vezzoli, Giovanni; Ghielmi, Giacomo; Mondaca, Gonzalo; Resentini, Alberto; Villarroel, Elena Katia; Padoan, Marta; Gentile, Paolo

2013-08-01

We use petrographic, mineralogical and geochemical data on modern river sediments of the Tupiza basin in the Bolivian Andes to investigate the relationships among human activity, heavy-metal contamination of sediments and modern erosion rates in mountain fluvial systems. Forward mixing model was used to quantify the relative contributions from each main tributary to total sediment load of the Tupiza River. The absolute sediment load was estimated by using the Pacific Southwest Inter Agency Committee model (PSIAC, 1968) after two years of geological field surveys (2009; 2010), together with data obtained from the Instituto Nacional del Agua public authority (INA, 2007), and suspended-load data from Aalto et al. (2006). Our results indicate that the sediment yield in the drainage basin is 910 ± 752 ton/km2year and the mean erosion rate is 0.40 ± 0.33 mm/year. These values compare well with erosion rates measured by Insel et al. (2010) using 10Be cosmogenic radionuclide concentrations in Bolivian river sediments. More than 40% of the Tupiza river load is produced in the upper part of the catchment, where highly tectonized and weathered rocks are exposed and coupled with sporadic land cover and intense human activity (mines). In the Rio Chilco basin strong erosion of upland valleys produce an increase of erosion (˜10 mm/year) and the influx of large amounts of sediment by mass wasting processes. The main floodplain of the Tupiza catchment represents a significant storage site for the heavy metals (˜657 ton/year). Fluvial sediments contain zinc, lead, vanadium, chromium, arsenic and nickel. Since the residence time of these contaminants in the alluvial plain may be more than 100 years, they may represent a potential source of pollution for human health.

Increase in the rate and uniformity of coastline erosion in Arctic Alaska

Science.gov (United States)

Jones, Benjamin M.; Arp, C.D.; Jorgenson, M.T.; Hinkel, Kenneth M.; Schmutz, J.A.; Flint, P.L.

2009-01-01

Analysis of a 60 km segment of the Alaskan Beaufort Sea coast using a time-series of aerial photography revealed that mean annual erosion rates increased from 6.8 m a-1 (1955 to 1979), to 8.7 m a-1 (1979 to 2002), to 13.6 m a-1 (2002 to 2007). We also observed that spatial patterns of erosion have become more uniform across shoreline types with different degrees of ice-richness. Further, during the remainder of the 2007 ice-free season 25 m of erosion occurred locally, in the absence of a westerly storm event. Concurrent arctic changes potentially responsible for this shift in the rate and pattern of land loss include declining sea ice extent, increasing summertime sea surface temperature, rising sea-level, and increases in storm power and corresponding wave action. Taken together, these factors may be leading to a new regime of ocean-land interactions that are repositioning and reshaping the Arctic coastline. Copyright 2009 by the American Geophysical Union.

Spatial Patterns of Long-Term Erosion Rates Beneath the Marine West Antarctic Ice Sheet: Insights into the Physics of Continental Scale Glacial Erosion from a Comparison with the Ice-Velocity Field

Science.gov (United States)

Howat, I. M.; Tulaczyk, S.; Mac Gregor, K.; Joughin, I.

2001-12-01

As part of the effort to build quantitative models of glacial erosion and sedimentation, it is particularly important to construct scaled relations between erosion, transport, and sedimentation rates and appropriate glaciological variables (e.g., ice velocity). Recent acquisition of bed topography and ice velocity data for the marine West Antarctic Ice Sheet (WAIS)[Joughin et al., 1999; Lythe et al., in press] provides an unprecedented opportunity to investigate continental-scale patterns of glacial erosion and their relationship to the ice velocity field. Utilizing this data, we construct a map of estimated long-term erosion rates beneath the WAIS. In order to calculate long-term erosion rates from the available data, we assume that: (1) the ice sheet has been present for ~5 mill. years, (2) the initial topography beneath the WAIS was that of a typical ( ~200 m.b.s.l.) continental shelf, and (3) the present topography is near local isostatic equilibrium (Airy type). The map of long-term erosion rates constructed in this fashion shows an intriguing pattern of relatively high rates (of the order of 0.1 mm/yr) concentrated beneath modern ice stream tributaries (ice velocity ~100 m/yr), but much lower erosion rates (of the order of 0.01 mm/yr) beneath both the modern fast-moving ice streams ( ~400 m/yr.) and the slow-moving parts of the ice sheet ( ~10 m/yr). This lack of clear correlation between the estimated erosion rates and ice velocity is somewhat unexpected given that both observational and theoretical studies have shown that bedrock erosion rates beneath mountain glaciers can often be calculated by multiplying the basal sliding velocity by a constant (typically of the order of ~10^-4)(Humphrey and Raymond, 1993 and Mac Gregor et al., 2000). We obtain an improved match between estimated erosion rates and bed topography by calculating erosion rates using horizontal gradients within the ice velocity field rather than the magnitude of ice velocity, as consistent

Uranium, thorium, gross alpha and gross beta assessment in fountain waters in towns of the Iron Quadrangle, Brazil

International Nuclear Information System (INIS)

Ferreira, Claudia A.; Palmieri, Helena E.L.; Menezes, Maria Angela de B.C.; Chaves, Renata D.A.; Dalmazio, Ilza

2013-01-01

The Iron Quadrangle region is known worldwide for its diversity, both ores and rock types, which record a long and important period of Earth's history. For thousands of years erosive processes have exposed ancient rocks, Archean and Proterozoic, in this region. The concentration of uranium, thorium, gross alpha and gross beta activities has been assessed in 34 fountains water samples collected from different towns in the Iron Quadrangle. The results obtained were compared to values established by CONAMA nº 396/2008 and Decree nº 2914/2011 by the Ministry of Health. For Th in water consumption there is no value established in the Brazilian legislation and the concentrations in all samples were lower than 0.01 μg L -1 . For uranium, the values ranged from less than 0.002 to 0.61 μg L -1 , and all results were lower than the value allowed of 15 μg L -1 and 30 μg L -1 established by the legislations above, respectively. The results for the radiation levels of gross alpha and gross beta activity in some fountains waters were slightly above the limits (0.5 Bq L -1 and 1.0 Bq L -1 ) established by CONAMA nº 396/2008 and Decreet nº 2914/2011, respectively. (author)

Establishment of the relationship between 137Cs loss and soil erosion rates

International Nuclear Information System (INIS)

Phan Son Hai

2003-01-01

The key stages involved in the use of 137 Cs in soil erosion assessment is presented. The method have been successfully applied in pilot scale. These main stages can be summarized as follows: 1/ selection of reference sites next to the study site and establishment of a reference fallout inventory for the study site; 2/measurement of the current spatial distribution of 137 Cs inventory; 3/ evaluation of the pattern of 137 Cs redistribution at the study site; 4/ development of a calibration relationship between 137 CS loss and gain and rate of soil erosion; 5/ estimation of soil redistribution rates using the calibration relationship. (PSH)

Estimating the erosion and deposition rates in a small watershed by the 137Cs tracing method

International Nuclear Information System (INIS)

Li Mian; Li Zhanbin; Yao Wenyi; Liu Puling

2009-01-01

Understanding the erosion and deposition rates in a small watershed is important for designing soil and water conservation measures. The objective of this study is to estimate the net soil loss and gain at points with various land use types and landform positions in a small watershed in the Sichuan Hilly Basin of China by the 137 Cs tracing technique. Among various land use types, the order of erosion rate was bare rock > sloping cultivated land > forest land. The paddy field and Caotu (a kind of cultivated land located at the foot of hills) were depositional areas. The erosion rate under different landform was in this order: hillside > saddle > hilltop. The footslope and the valley were depositional areas. The 137 Cs technique was shown to provide an effective means of documenting the spatial distribution of soil erosion and deposition within the small watershed

Measurement of Gross Alpha and Beta Emission Rates from Ceramic Tiles

International Nuclear Information System (INIS)

Wudthicharoonpun, Piyasak; Chankow, Nares

2007-08-01

Full text: Ceramic tiles normally used to cover floors and walls contain naturally occurring radioactive elements i.e. potassium-40, uranium, thorium and their daughters from raw materials. Thus, radioactivity was dependent upon source of raw materials and the amount used. The objective of this research was to measure gross alpha and beta emission rates to be used as a database for safety assessment and for selection of rooms to measure radioactive radon-222 gas

Gross N transformation rates after application of household compost or domestic sewage sludge to agricultural soil

DEFF Research Database (Denmark)

Ambus, P.; Kure, L.K.; Jensen, E.S.

2002-01-01

Gross N mineralization and immobilization was examined in soil amended with compost and sewage sludge on seven occasions during a year using N-15 pool dilution and enrichment techniques. Gross N mineralization was initially stimulated with both wastes and accelerated through the first 112 days...... of incubation, peaking at 5 mg N.kg(-1).d(-1) with compost compared with 4 mg N.kg(-1).d(-1) in control and sludge-treated soil. The magnitudes of mineralization rates exceeded those of immobilization by on average 6.3 ( compost) and 11.4 ( sludge) times, leading to a persistent net N mineralization cumulating...... up to 160 mg N.kg(-1) soil(compost) and 54 mg N.kg(-1) soil (sludge) over the season from May to November. The numerical model FLUAZ comprehensively predicted rates of gross mineralization and immobilization. Sludge exhibited an early season N-release, whereas compost released only 10% of the N...

Determination of Redistribution of Erosion/Deposition Rate in Cultivated Area Using 137Cs Technique

International Nuclear Information System (INIS)

Nita Suhartini; Syamsul Abbas RAS; Barokah A; Ali Arman L

2004-01-01

The aim of the research is to determine the rate of redistribution of erosion/deposition in cultivated area. The application of 137 Cs technique was carried out at cultivated area in Bojong - Ciawi, with slope less than 10 o and slope length of about 2 km. A reference site was selected at the top of the slope, and this site is flat, open and covered with grass. Two sites in the cultivated area were selected as study site namely LU-I ( 15 x 25 ) m with the distance of 1000 m from the top, and LU-II (17.5 x 20) m with the distance of 1300 m from the top. Sampling of soil at reference site was done by using scraper (20 x 50) cm, while sampling at study site by using core sampling (di = 7 cm). Soil samples were brought to the laboratorium for preparation and analysis of 137 Cs content. Preparation are including of drying, weighing the total dry, sieving and crushing. Analysis of 137 Cs content was done using multi channel analyzer (MCA) that connected to high purity germanium (HPGe), at 661 keV, and the minimum counting time of 16 hours. To estimate the erosion/deposit rate, two mathematical model were used, namely Proportional Model (PM) and Mass Balance Model 1 (MBM1). The result for application of 137 Cs technique showed that MBM1 gives somewhat higher value for deposit rate and somewhat lower value for erosion than PM. Land use - I (LU-I) of Bojong - Ciawi was suffering from erosion with the erosion rate from 1 t/(ha.y) to 13 t/(ha.y), and LU-II has deposit rate from 1 t/(ha.y) to 50 t/(ha.y). (author)

Soil erosion evaluation in a small watershed in Brazil through 137Cs fallout redistribution analysis and conventional models

International Nuclear Information System (INIS)

Bacchi, O.O.S.; Reichard, K.; Sparovek, G.; Ranieri, S.B.L.

2000-01-01

An investigation of rates and patterns of soil erosion on agricultural land cultivated with sugarcane was undertaken using the 137 Cs technique, USLE (Universal Soil Loss Equation) and WEPP (Water Erosion Prediction Project) model. The study was carried out on a representative catchment of a small watershed of the Piracicaba river basin, State of Sao Paulo, Brazil, called Ceveiro watershed, well known for its severe soil degradation caused by erosion. The results from the 137 Cs technique indicate that most part of the studied area (94%) are eroded at erosion rates that go up to 59 Mg ha -1 y -1 , with a weighted average rate of 23 Mg ha -1 y -1 . The weighted average rate of infield deposition and sediment retrieval that occurs in only 6% of the total area was estimated to be around 12 Mg ha -1 y -1 . These values led to very high net soil loss from the field, with rates of the order of 21 Mg ha -1 y -1 , which represents a sediment delivery ratio of 97%. A linear correlation between soil erosion rate estimated by the 137 Cs technique and the amount of available K in the top soil layer (0-20 cm) was observed. Based on this correlation the estimated amounts of net and gross K loss in the grid area due to soil erosion were of 0.2 and 1.52 kg ha -1 y -1 , respectively. The erosion rate estimated by USLE was 39 Mg ha -1 y -1 and by WEPP model 16.5 Mg ha -1 y -1 with a sediment delivery of 12.4 Mg ha -1 y -1 (75%). The results are a confirmation that the soil conservation practices adopted in the area are very poor and can explain the high siltation level of water reservoirs in the watershed. (author) [pt

Quantifying coastal erosion rates using anatomical change in exposed tree roots at Porquerolles Island (Var, France).

Science.gov (United States)

Morel, Pauline; Corona, Christophe; Lopez-Saez, Jérôme; Rovéra, Georges; Dewez, Thomas; Stoffel, Markus; Berger, Frédéric

2017-04-01

Rocky coasts are the most common type of ocean-land contacts and can be found in all types of morphogenetic environments. Most work on rocky environments focused on the impacts of modern sea level rise on cliff stability derived from sequential surveys, direct measurements or erosional features in anthropogenic structures. Studies mainly focused on rapid erosion so that little is known about erosion rates of the French Mediterranean coastal area. Using anatomical reactions in roots, has been successfully used in various environments in the past to quantify continuous denudation rates, mostly in relation with gullying processes (Vandekerckhove, 2001; Malik, 2008), aerial (or sheet) (Bodoque et al., 2005; Lopez Saez et al., 2011; Lucia et al., 2011), river bank (Malik, 2006; Hitz et al., 2008a; Stoffel et al., 2012), or lake shore (Fantucci, 2007) erosion, but never so far on coastal cliffs environment. This study aims at exploring the potential of dendrogeomorphic approach to quantify multidecadal changes in coastal environments on Porquerolles Island (Var, France). We sampled 56 discs from Pinus halepensis Mill. roots on former alluvial deposits eroded by present day sea level (escarpments of a few meter in height) and on sandy-gravelly cliffs. We were able to dates erosion pulses as well as changes in cliff geometry with annual resolution over 30-40 years showing an average erosion rate of 2.1 cm yr-1. Our results are consistent with those found in the study of Giuliano (2015) on Mediterranean coastal environment. This contribution therefore demonstrates that dendrogeomorphic analyses of roots clearly have significant potential and are a powerful tool for the quantification of multidecadal cliff retreats rates in areas where measurements of past erosion is lacking. References: Bodoque J, Díez-Herrero A, Martín-Duque J, Rubiales J, Godfrey A, Pedraza J, Carrasco R, Sanz M. 2005. Sheet erosion rates determined by using dendrogeomorphological analysis of exposed

Centennial- to millennial-scale hard rock erosion rates deduced from luminescence-depth profiles

NARCIS (Netherlands)

Sohbati, Reza; Liu, Jinfeng; Jain, Mayank; Murray, Andrew; Egholm, David; Paris, Richard; Guralnik, Benny

2018-01-01

The measurement of erosion and weathering rates in different geomorphic settings and over diverse temporal and spatial scales is fundamental to the quantification of rates and patterns of earth surface processes. A knowledge of the rates of these surface processes helps one to decipher their

Erosion rates and landscape evolution of the lowlands of the Upper Paraguay river basin (Brazil) from cosmogenic 10Be

Science.gov (United States)

Pupim, Fabiano do Nascimento; Bierman, Paul R.; Assine, Mario Luis; Rood, Dylan H.; Silva, Aguinaldo; Merino, Eder Renato

2015-04-01

The importance of Earth's low sloping areas in regard to global erosion and sediment fluxes has been widely and vigorously debated. It is a crucial area of research to elucidate geologically meaningful rates of land-surface change and thus the speed of element cycling on Earth. However, there are large portions of Earth where erosion rates have not been well or extensively measured, for example, the tropical lowlands. The Cuiabana lowlands are an extensive low-altitude and low-relief dissected metamorphic terrain situated in the Upper Paraguay river basin, central-west Brazil. Besides exposures of highly variable dissected metamorphic rocks, flat residual lateritic caps related to a Late Cenozoic planation surface dominate interfluves of the Cuiabana lowlands. The timescale over which the lowlands evolved and the planation surface developed, and the rate at which they have been modified by erosion, are poorly known. Here, we present measurements of in situ produced cosmogenic 10Be in outcropping metamorphic bedrock and clastic-lateritic caps to quantify rates of erosion of the surface and associated landforms in order to better understand the Quaternary landscape evolution of these lowlands. Overall, slow erosion rates (mean 10 m/Ma) suggest a stable tectonic environment in these lowlands. Erosion rates vary widely between different lithologies (range 0.57 to 28.3 m/Ma) consistent with differential erosion driving regional landform evolution. The lowest erosion rates are associated with the low-relief area (irregular plains), where clastic-laterite (mean 0.67 m/Ma) and quartzite (mean 2.6 m/Ma) crop out, whereas the highest erosion rates are associated with dissection of residual hills, dominated by metasandstone (mean 11.6 m/Ma) and phyllite (mean 27.6 m/Ma). These data imply that the Cuiabana lowland is comprised of two dominant landform sets with distinct and different dynamics. Because the planation surface (mostly lowlands) is lowering and losing mass more

Uranium, thorium, gross alpha and gross beta assessment in fountain waters in towns of the Iron Quadrangle, Brazil

Energy Technology Data Exchange (ETDEWEB)

Ferreira, Claudia A.; Palmieri, Helena E.L.; Menezes, Maria Angela de B.C.; Chaves, Renata D.A.; Dalmazio, Ilza, E-mail: cferreiraquimica@yahoo.com.br, E-mail: help@cdtn.br, E-mail: menezes@cdtn.br, E-mail: rda@cdtn.br, E-mail: id@cdtn.br [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)

2013-07-01

The Iron Quadrangle region is known worldwide for its diversity, both ores and rock types, which record a long and important period of Earth's history. For thousands of years erosive processes have exposed ancient rocks, Archean and Proterozoic, in this region. The concentration of uranium, thorium, gross alpha and gross beta activities has been assessed in 34 fountains water samples collected from different towns in the Iron Quadrangle. The results obtained were compared to values established by CONAMA nº 396/2008 and Decree nº 2914/2011 by the Ministry of Health. For Th in water consumption there is no value established in the Brazilian legislation and the concentrations in all samples were lower than 0.01 μg L{sup -1}. For uranium, the values ranged from less than 0.002 to 0.61 μg L{sup -1}, and all results were lower than the value allowed of 15 μg L{sup -1} and 30 μg L{sup -1} established by the legislations above, respectively. The results for the radiation levels of gross alpha and gross beta activity in some fountains waters were slightly above the limits (0.5 Bq L{sup -1} and 1.0 Bq L{sup -1}) established by CONAMA nº 396/2008 and Decreet nº 2914/2011, respectively. (author)

Effect of Impact Angle on the Erosion Rate of Coherent Granular Soil, with a Chernozemic Soil as an Example

Science.gov (United States)

Larionov, G. A.; Bushueva, O. G.; Gorobets, A. V.; Dobrovol'skaya, N. G.; Kiryukhina, Z. P.; Krasnov, S. F.; Kobylchenko Kuksina, L. V.; Litvin, L. F.; Sudnitsyn, I. I.

2018-02-01

It has been shown in experiments in a hydraulic flume with a knee-shaped bend that the rate of soil erosion more than doubles at the flow impact angles to the channel side from 0° to 50°. At higher channel bends, the experiment could not be performed because of backwater. Results of erosion by water stream approaching the sample surface at angles between 2° and 90° are reported. It has been found that the maximum erosion rate is observed at flow impact angles of about 45°, and the minimum rate at 90°. The minimum soil erosion rate is five times lower than the maximum erosion rate. This is due to the difference in the rate of free water penetration into the upper soil layer, and the impact of the hydrodynamic pressure, which is maximum at the impact angle of 90°. The penetration of water into the interaggregate space results in the breaking of bonds between aggregates, which is the main condition for the capture of particles by the flow.

Analysis of C-MOD molybdenum divertor erosion and code/data comparison

Energy Technology Data Exchange (ETDEWEB)

Brooks, J.N., E-mail: brooksjn@purdue.edu [Purdue University, West Lafayette, IN (United States); Allain, J.P. [Purdue University, West Lafayette, IN (United States); Whyte, D.G.; Ochoukov, R.; Lipschultz, B. [Massachusetts Institute of Technology, Cambridge, MA (United States)

2011-08-01

We analyze an important 15 year old Alcator C-MOD study of campaign-integrated molybdenum divertor erosion in which the measured net erosion was significantly higher ({approx}X3) than originally predicted by a simple model . We perform full process sputtering erosion/redeposition computational analysis including the effect of a possible RF induced sheath. The simulations show that most sputtered Mo atoms are ionized close to the surface and strongly redeposited, via Lorentz force motion and collisional friction with the high density incoming plasma. The predicted gross erosion profile is a reasonable match to MoI influx data, however, the critically important net erosion comparison with post-exposure Mo tile analysis is poor, with {approx}X10 higher peak erosion measured than computed. An RF sheath increases predicted erosion by {approx}45%, thus being significant but not fundamental. We plan future analysis.

Constraining Quaternary ice covers and erosion rates using cosmogenic 26Al/10Be nuclide concentrations

Science.gov (United States)

Knudsen, Mads Faurschou; Egholm, David Lundbek

2018-02-01

Paired cosmogenic nuclides are often used to constrain the exposure/burial history of landforms repeatedly covered by ice during the Quaternary, including tors, high-elevation surfaces, and steep alpine summits in the circum-Arctic regions. The approach generally exploits the different production rates and half-lives of 10Be and 26Al to infer past exposure/burial histories. However, the two-stage minimum-limiting exposure and burial model regularly used to interpret the nuclides ignores the effect of variable erosion rates, which potentially may bias the interpretation. In this study, we use a Monte Carlo model approach to investigate systematically how the exposure/burial and erosion history, including variable erosion and the timing of erosion events, influence concentrations of 10Be and 26Al. The results show that low 26Al/10Be ratios are not uniquely associated with prolonged burial under ice, but may as well reflect ice covers that were limited to the coldest part of the late Pleistocene combined with recent exhumation of the sample, e.g. due to glacial plucking during the last glacial period. As an example, we simulate published 26Al/10Be data from Svalbard and show that it is possible that the steep alpine summits experienced ice-free conditions during large parts of the late Pleistocene and varying amounts of glacial erosion. This scenario, which contrasts with the original interpretation of more-or-less continuous burial under non-erosive ice over the last ∼1 Myr, thus challenge the conventional interpretation of such data. On the other hand, high 26Al/10Be ratios do not necessarily reflect limited burial under ice, which is the common interpretation of high ratios. In fact, high 26Al/10Be ratios may also reflect extensive burial under ice, combined with a change from burial under erosive ice, which brought the sample close to the surface, to burial under non-erosive ice at some point during the mid-Pleistocene. Importantly, by allowing for variable

Estimating the erosion and deposition rates in a small watershed by the {sup 137}Cs tracing method

Energy Technology Data Exchange (ETDEWEB)

Li Mian [Yellow River Institute of Hydraulic Research, Key Laboratory of Sediment Research of Yellow River of Ministry of Water Resources, Zhengzhou, Henan 450003 (China)], E-mail: hnli-mian@163.com; Li Zhanbin [Xi' an University of Technology, Xi' an, Shaanxi 710048 (China); Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling, Shaanxi 712100 (China); Yao Wenyi [Yellow River Institute of Hydraulic Research, Key Laboratory of Sediment Research of Yellow River of Ministry of Water Resources, Zhengzhou, Henan 450003 (China); Liu Puling [Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling, Shaanxi 712100 (China)

2009-02-15

Understanding the erosion and deposition rates in a small watershed is important for designing soil and water conservation measures. The objective of this study is to estimate the net soil loss and gain at points with various land use types and landform positions in a small watershed in the Sichuan Hilly Basin of China by the {sup 137}Cs tracing technique. Among various land use types, the order of erosion rate was bare rock > sloping cultivated land > forest land. The paddy field and Caotu (a kind of cultivated land located at the foot of hills) were depositional areas. The erosion rate under different landform was in this order: hillside > saddle > hilltop. The footslope and the valley were depositional areas. The {sup 137}Cs technique was shown to provide an effective means of documenting the spatial distribution of soil erosion and deposition within the small watershed.

Nutrient and Organic Carbon Losses, Enrichment Rate, and Cost of Water Erosion

Directory of Open Access Journals (Sweden)

Ildegardis Bertol

Full Text Available ABSTRACT Soil erosion from water causes loss of nutrients and organic carbon, enriches the environment outside the erosion site, and results in costs. The no-tillage system generates increased nutrient and C content in the topsoil and, although it controls erosion, it can produce a more enriched runoff than in the conventional tillage system. This study was conducted in a Humic Cambisol in natural rainfall from 1997 to 2012 to quantify the contents and total losses of nutrients and organic C in soil runoff, and to calculate the enrichment rates and the cost of these losses. The treatments evaluated were: a soil with a crop, consisting of conventional tillage with one plowing + two harrowings (CT, minimum tillage with one chisel plowing + one harrowing (MT, and no tillage (NT; and b bare soil: one plowing + two harrowings (BS. In CT, MT, and NT, black oat, soybean, vetch, corn, turnip, and black beans were cultivated. Over the 15 years, 15.5 Mg ha-1 of limestone, 525 kg ha-1 of N (urea, 1,302 kg ha-1 of P2O5 (triple superphosphate, and 1,075 kg ha-1 of K2O (potassium chloride were used in the soil. The P, K, Ca, Mg, and organic C contents in the soil were determined and also the P, K, Ca, and Mg sediments in the runoff water. From these contents, the total losses, the enrichment rates (ER, and financial losses were calculated. The NT increased the P, K, and organic C contents in the topsoil. The nutrients and organic C content in the runoff from NT was greater than from CT, showing that NT was not a fully conservationist practice for soil. The linear model y = a + bx fit the data within the level of significance (p≤0.01 when the values of P, K, and organic C in the sediments from erosion were related to those values in the soil surface layer. The nutrient and organic C contents were higher in the sediments from erosion than in the soil where the erosion originated, generating values of ER>1 for P, K, and organic C. The value of the total losses

Developing an Erosion Rate Map for Myanmar Using USLE, GIS and Remote Sensing

Science.gov (United States)

Emtehani, Sobhan; Rutten, Martine

2017-04-01

Predicting erosion and estimating sediment loads in rivers are of major tasks in water resources system planning and management. In Myanmar erosion and collapse of river banks is common during the rainy season and riverine communities are frequently forced to relocate as their homes are dangerously close to the disintegrating river banks (Mann 2013). Myanmar is one of climatically most diverse countries located in Southeast Asia, where sheet, rill, and gully erosion affect crop yields as well as livelihood strategies of many people (Htwe, Brinkmann et al. 2015). In Myanmar, soil erosion measurement and monitoring approaches are increasingly important for land management planning to effectively avoid erosion and soil degradation, but such monitoring is limited by the availability of data and budgetary constraints. Therefore, spatial modeling approaches using GIS and remote sensing techniques play an important role for rapid risk assessments (Htwe 2016). In this study ''Model Builder'' tool in ArcGIS was used to create a model which generates an erosion rate map using Universal Soil Loss Equation (USLE). USLE is the product of five factors: rainfall erosivity factor (R), soil erodibility factor (K), slope length and steepness factor (LS), crop management factor (C), and support practice factor (P). Input data files for this model were acquired from online open source databases. Precipitation data was downloaded from Tropical Rainfall Measuring Mission (TRMM) for calculation of R factor. The resolution of TRMM data is very coarse (0.25 degree × 0.25 degree), therefore it was spatially downscaled by developing a relation between TRMM and Normalized Difference Vegetation Index (NDVI) using regression analysis method. Soil maps depicting percentages of sand, clay and silt were obtained from soilgrids website for calculation of K factor. Digital Elevation Model (DEM) with resolution of 90 meters was taken from Shuttle Radar Topography Mission (SRTM) for calculation of LS

Simulating CRN derived erosion rates in a transient Andean catchment using the TTLEM model

Science.gov (United States)

Campforts, Benjamin; Vanacker, Veerle; Herman, Frédéric; Schwanghart, Wolfgang; Tenrorio Poma, Gustavo; Govers, Gerard

2017-04-01

Assessing the impact of mountain building and erosion on the earth surface is key to reconstruct and predict terrestrial landscape evolution. Landscape evolution models (LEMs) are an essential tool in this research effort as they allow to integrate our growing understanding of physical processes governing erosion and transport of mass across the surface. The recent development of several LEMs opens up new areas of research in landscape evolution. Here, we want to seize this opportunity by answering a fundamental research question: does a model designed to simulate landscape evolution over geological timescales allows to simulate spatially varying erosion rates at a millennial timescale? We selected the highly transient Paute catchment in the Southeastern Ecuadorian Andes as a study area. We found that our model (TTLEM) is capable to better explain the spatial patterns of ca. 30 Cosmogenic Radio Nuclide (CRN) derived catchment wide erosion rates in comparison to a classical, statistical approach. Thus, the use of process-based landscape evolution models may not only be of great help to understand long-term landscape evolution but also in understanding spatial and temporal variations in sediment fluxes at the millennial time scale.

Erosion-corrosion synergistics in the low erosion regime

International Nuclear Information System (INIS)

Corey, R.G.; Sethi, V.K.

1986-01-01

Many engineering alloys display good high temperature corrosion resistance. However, when they are used in corrosive environments where they are subjected to erosion also, the corrosion resistance has been adversely affected. The phenomenon known as erosion-corrosion is complex and requires detailed investigation of how the erosion and corrosion kinetics interact and compete. At the Kentucky Center for Energy Research Laboratory, an erosion-corrosion tester was used to perform erosion-oxidation tests on 2 1/4 Cr-1 Mo steel at 500-600 0 C using alumina abrasive at low velocities. The erosion-oxidation rate data and morphology of exposed surfaces are consistent with oxide chipping and fracturing being the mode of material loss

Impacts of the post-fire erosion processes compared with the agricultural erosion rates for a mountain catchment in NW Iberia

Science.gov (United States)

Marisa Santos, Juliana; Nunes, João Pedro; Bernard-Jannin, Léonard; Gonzalez Pelayo, Oscar; Keizer, Jan Jacob

2014-05-01

after forest fires. The last forest fire in August 2011 burned 10% of the total area in the north-west part of the catchment. Post-fire management operations 9 month after the fire (clear-cutting and deep plowing operations) and after plantation of "Quercus robur" left the soil exposed, and relatively mild rainstorms led to large amounts of soil loss, including a large amount of rills and other erosion features. This constituted an opportunity to compare these erosion rates with the ones observed in agricultural fields for similar edapho-climatic conditions, and also observe distinct timing of erosion occurrence which was linked with different periods when soils are exposed. This communication presents the assessment of the impact of this fire on soil erosion rates, where results indicate that soil losses after soil preparation for forest replanting might be equivalent, in long-term, to soil losses in agricultural fields.

Numerical simulation of mud erosion rate in sand-mud alternate layer and comparison with experiment

Science.gov (United States)

Yoshida, T.; Yamaguchi, T.; Oyama, H.; Sato, T.

2015-12-01

For gas production from methane hydrates in sand-mud alternate layers, depressurization method is expected as feasible. After methane hydrate is dissociated, gas and water flow in pore space. There is a concern about the erosion of mud surface and it may result in flow blockage that disturbs the gas production. As a part of a Japanese National hydrate research program (MH21, funded by METI), we developed a numerical simulation of water-induced mud erosion in pore-scale sand-mud domains to model such mud erosion. The size of which is of the order of 100 micro meter. Water flow is simulated using a lattice Boltzmann method (LBM) and mud surface is treated as solid boundary with arbitrary shape, which changes with time. Periodic boundary condition is adopted at the domain boundaries, except for the surface of mud layers and the upper side. Shear stress acting on the mud surface is calculated using a momentum-exchange method. Mud layer is eroded when the shear stress exceeds a threshold coined a critical shear stress. In this study, we compared the simulated mud erosion rate with experimental data acquired from an experiment using artificial sand-mud core. As a result, the simulated erosion rate agrees well with that of the experiment.

Estimation of water erosion rates using RUSLE3D in Alicante province (Spain)

OpenAIRE

Garcia Rodríguez, Jose Luis; Giménez Suárez, Martín Cruz; Arraiza Bermudez-Cañete, Maria Paz

2015-01-01

The purpose of this study was the estimation of current and potential water erosion rates in Alicante Province using RUSLE3D (Revised Universal Soil Loss Equation-3D) model with Geographical Information System (GIS) support by request from the Valencia Waste Energy Use. RUSLE3D uses a new methodology for topographic factor estimation (LS factor) based on the impact of flow convergence allowing better assessment of sediment distribution detached by water erosion. In RUSLE3D equation, the effec...

Comprehensive assessment of soil erosion risk for better land use planning in river basins: Case study of the Upper Blue Nile River.

Science.gov (United States)

Haregeweyn, Nigussie; Tsunekawa, Atsushi; Poesen, Jean; Tsubo, Mitsuru; Meshesha, Derege Tsegaye; Fenta, Ayele Almaw; Nyssen, Jan; Adgo, Enyew

2017-01-01

In the drought-prone Upper Blue Nile River (UBNR) basin of Ethiopia, soil erosion by water results in significant consequences that also affect downstream countries. However, there have been limited comprehensive studies of this and other basins with diverse agroecologies. We analyzed the variability of gross soil loss and sediment yield rates under present and expected future conditions using a newly devised methodological framework. The results showed that the basin generates an average soil loss rate of 27.5tha -1 yr -1 and a gross soil loss of ca. 473Mtyr -1 , of which, at least 10% comes from gully erosion and 26.7% leaves Ethiopia. In a factor analysis, variation in agroecology (average factor score=1.32) and slope (1.28) were the two factors most responsible for this high spatial variability. About 39% of the basin area is experiencing severe to very severe (>30tha -1 yr -1 ) soil erosion risk, which is strongly linked to population density. Severe or very severe soil erosion affects the largest proportion of land in three subbasins of the UBNR basin: Blue Nile 4 (53.9%), Blue Nile 3 (45.1%), and Jema Shet (42.5%). If appropriate soil and water conservation practices targeted ca. 77.3% of the area with moderate to severe erosion (>15tha -1 yr -1 ), the total soil loss from the basin could be reduced by ca. 52%. Our methodological framework identified the potential risk for soil erosion in large-scale zones, and with a more sophisticated model and input data of higher spatial and temporal resolution, results could be specified locally within these risk zones. Accurate assessment of soil erosion in the UBNR basin would support sustainable use of the basin's land resources and possibly open up prospects for cooperation in the Eastern Nile region. Copyright © 2016 Office national des forêts. Published by Elsevier B.V. All rights reserved.

Understanding erosion rates in the Himalayan orogen: A case study from the Arun Valley

Science.gov (United States)

Olen, Stephanie M.; Bookhagen, Bodo; Hoffmann, Bernd; Sachse, Dirk; Adhikari, D. P.; Strecker, Manfred R.

2015-10-01

Understanding the rates and pattern of erosion is a key aspect of deciphering the impacts of climate and tectonics on landscape evolution. Denudation rates derived from terrestrial cosmogenic nuclides (TCNs) are commonly used to quantify erosion and bridge tectonic (Myr) and climatic (up to several kiloyears) time scales. However, how the processes of erosion in active orogens are ultimately reflected in 10Be TCN samples remains a topic of discussion. We investigate this problem in the Arun Valley of eastern Nepal with 34 new 10Be-derived catchment-mean denudation rates. The Arun Valley is characterized by steep north-south gradients in topography and climate. Locally, denudation rates increase northward, from <0.2 mm yr-1 to ~1.5 mm yr-1 in tributary samples, while main stem samples appear to increase downstream from ~0.2 mm yr-1 at the border with Tibet to 0.91 mm yr-1 in the foreland. Denudation rates most strongly correlate with normalized channel steepness (R2 = 0.67), which has been commonly interpreted to indicate tectonic activity. Significant downstream decrease of 10Be concentration in the main stem Arun suggests that upstream sediment grains are fining to the point that they are operationally excluded from the processed sample. This results in 10Be concentrations and denudation rates that do not uniformly represent the upstream catchment area. We observe strong impacts on 10Be concentrations from local, nonfluvial geomorphic processes, such as glaciation and landsliding coinciding with areas of peak rainfall rates, pointing toward climatic modulation of predominantly tectonically driven denudation rates.

Influence of liquid temperature and flow rate on enamel erosion and surface softening.

Science.gov (United States)

Eisenburger, M; Addy, M

2003-11-01

Enamel erosion and softening are based on chemical processes which could be influenced by many factors including temperature and acid flow rate. Knowledge of the influence of these variables could have relevance to research experiments and clinical outcomes. Both parameters were investigated using an ultrasonication and profilometry method to assess erosion depth and surface softening of enamel. The influence of temperature was studied by eroding polished human enamel samples at 4, 20, 35 or 50 degrees C for 2 h. Secondly, different liquid flow conditions were established by varying acid agitation. Additionally, a slow laminar flow and a jet of citric acid, to simulate drinking through a straw, were applied to specimens. Erosion depth increased significantly with acid temperature from 11.0 microm at 4 degrees C to 35.8 microm at 50 degrees C. Surface softening increased much more slowly and plateaued at 2.9 microm to 3.5 microm after 35 degrees C. A strong dependence of erosion on liquid flow was revealed. In unstirred conditions only 8.6 microm erosion occurred, which increased to 22.2 microm with slow stirring and 40.9 microm with fast stirring. Surface softening did not increase correspondingly with its largest extent at slow stirring at 3.4 microm.The implication of these data are: first, the conditions for erosion experiments in vitro or in situ need to be specified for reliable comparisons between studies. Secondly, erosion of teeth by soft drinks are likely to be influenced both by the temperature of the drink and individual drinking habits.

Ultrasonic Measurement of Erosion/corrosion Rates in Industrial Piping Systems

Science.gov (United States)

Sinclair, A. N.; Safavi, V.; Honarvar, F.

2011-06-01

Industrial piping systems that carry aggressive corrosion or erosion agents may suffer from a gradual wall thickness reduction that eventually threatens pipe integrity. Thinning rates could be estimated from the very small change in wall thickness values measured by conventional ultrasound over a time span of at least a few months. However, measurements performed over shorter time spans would yield no useful information—minor signal distortions originating from grain noise and ultrasonic equipment imperfections prevent a meaningful estimate of the minuscule reduction in echo travel time. Using a Model-Based Estimation (MBE) technique, a signal processing scheme has been developed that enables the echo signals from the pipe wall to be separated from the noise. This was implemented in a laboratory experimental program, featuring accelerated erosion/corrosion on the inner wall of a test pipe. The result was a reduction in the uncertainty in the wall thinning rate by a factor of four. This improvement enables a more rapid response by system operators to a change in plant conditions that could pose a pipe integrity problem. It also enables a rapid evaluation of the effectiveness of new corrosion inhibiting agents under plant operating conditions.

Hillslope-channel coupling in a steep Hawaiian catchment accelerates erosion rates over 100-fold

Science.gov (United States)

Stock, J. D.; Hanshaw, M. N.; Rosener, M.; Schmidt, K. M.; Brooks, B. A.; Tribble, G.; Jacobi, J.

2009-12-01

In tropical watersheds, hillslope changes are producing increasing amounts of fine sediment that can be quickly carried to reefs by channels. Suspended sediment concentrations off the reefs of Molokai, Hawaii, chronically exceed a toxic level of 10 mg/L, threatening reef ecosystems. We hypothesize that historic conversion of watersheds from soil creep to overland flow erosion increased both magnitude and frequency of sediment flooding adjacent reefs. We combined surficial and ecological mapping, hillslope and stream gages, and novel sensors to locate, quantify and model the generation of fine sediments polluting the Molokai reef. Ecological and geomorphic mapping from LiDAR and multi-spectral imagery located a subset of overland flow areas with vegetation cover below a threshold value preventing erosion. Here, feral goat grazing exposed cohesive volcanic soils whose low matrix hydraulic conductivities (1-20 mm/hour) promote Horton overland flow erosion. We instrumented steep, barren hillslopes with soil moisture sensors, overland flow meters, Parshall flumes, ISCO sediment samplers, and a rain gage and conducted repeat Tripod LiDAR and infiltration tests. To characterize soil resistance here and elsewhere to overland flow erosion, we deployed a Cohesive Strength Meter (CSM) to simulate the stresses of flowing water. At the 13.5 km 2 watershed mouth we used a USGS stream gage and ISCO sediment sampler to estimate total load. Over 2 years, storms triggered overland flow during rainfall intensities above 10-15 mm/hr. Overland flow meters indicate such flows can be up to 3 cm deep, with a tendency to deepen downslope. CSM tests indicate that these depths are insufficient to erode soils where vegetation is dense, but far above threshold values of 2-3 mm depth for bare soil erosion. Sediment ratings curves for both hillslope and downstream catchment gages show strong clock-wise hysteresis during the first intense storms in the Fall, becoming linear later in the rainy

NM Gross Receipts January - June 2012

Data.gov (United States)

Earth Data Analysis Center, University of New Mexico — This layer represents boundaries for New Mexico's gross receipts tax districts as identified on the "Gross Receipts Tax Rate Schedule" published by the Taxation and...

NM Gross Receipts July - December 2013

Data.gov (United States)

Earth Data Analysis Center, University of New Mexico — This layer represents boundaries for New Mexico's gross receipts tax districts as identified on the "Gross Receipts Tax Rate Schedule" published by the Taxation and...

NM Gross Receipts January - June 2014

Data.gov (United States)

Earth Data Analysis Center, University of New Mexico — This layer represents boundaries for New Mexico's gross receipts tax districts as identified on the "Gross Receipts Tax Rate Schedule" published by the Taxation and...

NM Gross Receipts July - December 2012

Data.gov (United States)

Earth Data Analysis Center, University of New Mexico — This layer represents boundaries for New Mexico's gross receipts tax districts as identified on the "Gross Receipts Tax Rate Schedule" published by the Taxation and...

NM Gross Receipts January - June 2013

Data.gov (United States)

Earth Data Analysis Center, University of New Mexico — This layer represents boundaries for New Mexico's gross receipts tax districts as identified on the "Gross Receipts Tax Rate Schedule" published by the Taxation and...

NM Gross Receipts January - June 2011

Data.gov (United States)

Earth Data Analysis Center, University of New Mexico — This layer represents boundaries for New Mexico's gross receipts tax districts as identified on the "Gross Receipts Tax Rate Schedule" published by the Taxation and...

Modeling erosion of unsaturated compacted bentonite by groundwater flow; pinhole erosion test case

International Nuclear Information System (INIS)

Laurila, T.; Sane, P.; Olin, M.; Koskinen, K.

2012-01-01

swelling rate to erosion rate. Expressing eroded mass as a function of time as M(t) ∝ tβ. we note that for non-swelling material the wall shear -based erosion model gives β = 0,5. We find this limit in our model by suppressing swelling, and we observe that β increases when ratio of swelling to erosion increases, approaching values β ≅ 1 for strong swelling. It follows that the long term erosion of backfill and buffer materials are expected to differ, with erosion rates in the more compact buffer dropping slower. The result also suggests that the lower the initial erosion, the longer one can expect that rate to be maintained. We solve the model in cylindrically symmetric coordinates using COMSOL Multiphysics software, and fit parameters to match pinhole experiments on MX-80 bentonite with different salinities of the water inflow. Significant scatter within the experimental data makes it difficult to definitively validate models. Figure 1 shows erosion behavior in the model at the limit of vanishing swelling, and contrasts it to the highly-swelling case. Observations from the pinhole experiments, as well as from down-scaled piping erosion tests, show that erosion rates in buffer material don't drop significantly in time, suggesting a consistent with high swelling. In the larger piping erosion tests a seemingly steady state in the erosion rate is reached for an extended amount of time. The effects of scatter are reduced using statistical analysis of this state. An important experimental finding of unsaturated erosion is that larger salinities lead to larger erosion rates, in contrast to saturated erosion where the opposite has been observed. We expect this effect to be due to the processes of saturation, suction and permeability. Future work aims to model the dominant processes in this effect, as pertains to Posiva reference conditions for the Olkiluoto site, without going to the full complexity of (T)HM modeling, such as the Barcelona expansible model

A survey of gross alpha and gross beta activity in soil samples in Kinta District, Perak, Malaysia

International Nuclear Information System (INIS)

Lee, Siak Kuan; Wagiran, Husin; Ramli, Ahmad Termizi

2014-01-01

The objective of this study was to determine the gross alpha and gross beta activity concentrations from the different soil types found in the Kinta District, Perak, Malaysia. A total of 128 soil samples were collected and their dose rates were measured 1 m above the ground. Gross alpha and gross beta activity measurements were carried out using gas flow proportional counter, Tennelec Series 5 LB5500 Automatic Low Background Counting System. The alpha activity concentration ranged from 15 to 9634 Bq kg -1 with a mean value of 1558±121 Bq kg -1 . The beta activity concentration ranged from 142 to 6173 Bq kg -1 with a mean value of 1112±32 Bq kg -1 . High alpha and beta activity concentrations are from the same soil type. The results of the analysis show a strong correlation between the gross alpha activity concentration and dose rate (R = 0.92). The data obtained can be used as a database for each soil type. (authors)

Quantifying Soil Erosion and Deposition Rates in Tea Plantation Area, Cameron Highlands, Malaysia Using 137Cs

International Nuclear Information System (INIS)

Zaini Hamzah; Che Yasmin Amirudin; Ahmad Saat; Ahmad Saat; Ab Khalik Wood

2014-01-01

The soil erosion and deposition in the hilly area is a great concern for the planters. In this study, the tea plantation was chosen to quantify the rates of soil erosion and deposition for it will provide information on the improvement of soil conditions and cost reduction of fertilizer consumption. The aims of this research are to determine the rate of soil erosion and deposition using environmental radionuclide, 137 Cs. Soil profile samples were collected by using scrapper plate and two cores soil sample were collected in the undisturbed forests area nearby. The 137 Cs activity concentration was measured using low background coaxial hyper pure germanium detector gamma spectrometer based on 137 Cs gamma energy peak at 661.66 keV. The highest erosion rate using Proportional Models and Mass Balance Model 1 was found in point HE top area which is 52.39 t ha -1 yr -1 and 95.53 t ha -1 yr -1 respectively while the lowest at location HF top which is 4.78 t ha -1 yr -1 and 4.97 t ha -1 yr -1 . The deposition rate was higher in HF center which is 216.82 t ha -1 yr -1 and 97.51 t ha -1 yr -1 and the lowest at HE center which is 0.05 t ha -1 yr -1 for both models used. (author)

The Influence of Cultivation System on Distribution Profile Of 137cs and Erosion / Deposition Rate

Directory of Open Access Journals (Sweden)

Nita Suhartini

2016-05-01

Full Text Available 137Cs radiogenic content in the soil can be used to estimate the rate of erosion and deposition in an area occurring since 1950’s, by comparing the content of the 137Cs in observed site with those in a stable reference site. This experiment aimed to investigate the influence of cultivation type on distribution profile of 137Cs and distribution of erosion and deposition rate in cultivated area. A study site was small cultivated area with slope steepness <10o and length 2 km located in Bojong – Ciawi. For this purpose, the top of a slope was chosen for reference site and three plot sites were selected namely Land Use I that using simple cultivation, Land Use II that using simple cultivation with ridge and furrow, and Land Use III using machine cultivation. The results showed that cultivation could make a movement of 137Cs to the deeper layer and ridges and furrows cultivation system could minimized an erosion process. The net erosion and deposition for land Use I, II and III were -25 t/ha/yr , 24 t/ha/yr and -58 t/ha/yr, respectively.

Assessment of soil erosion and deposition rates in a Moroccan agricultural field using fallout 137Cs and 210Pbex

International Nuclear Information System (INIS)

Benmansour, M.; Mabit, L.; Nouira, A.; Moussadek, R.; Bouksirate, H.; Duchemin, M.; Benkdad, A.

2013-01-01

In Morocco land degradation – mainly caused by soil erosion – is one of the most serious agroenvironmental threats encountered. However, only limited data are available on the actual magnitude of soil erosion. The study site investigated was an agricultural field located in Marchouch (6°42′ W, 33° 47′ N) at 68 km south east from Rabat. This work demonstrates the potential of the combined use of 137 Cs, 210 Pb ex as radioisotopic soil tracers to estimate mid and long term erosion and deposition rates under Mediterranean agricultural areas. The net soil erosion rates obtained were comparable, 14.3 t ha −1 yr −1 and 12.1 ha −1 yr −1 for 137 Cs and 210 Pb ex respectively, resulting in a similar sediment delivery ratio of about 92%. Soil redistribution patterns of the study field were established using a simple spatialisation approach. The resulting maps generated by the use of both radionuclides were similar, indicating that the soil erosion processes has not changed significantly over the last 100 years. Over the previous 10 year period, the additional results provided by the test of the prediction model RUSLE 2 provided results of the same order of magnitude. Based on the 137 Cs dataset established, the contribution of the tillage erosion impact has been evaluated with the Mass Balance Model 3 and compared to the result obtained with the Mass Balance Model 2. The findings highlighted that water erosion is the leading process in this Moroccan cultivated field, tillage erosion under the experimental condition being the main translocation process within the site without a significant and major impact on the net erosion. - Highlights: ► Net erosion rates estimated by 137 Cs and 210 Pb ex techniques were found comparable. ► The water erosion is the leading process in this Moroccan cultivated field. ► Soil erosion process has not changed significantly over the last 100 years. ► The prediction model RUSLE 2 provided results of the same order of

Small crater modification on Meridiani Planum and implications for erosion rates and climate change on Mars

Science.gov (United States)

Golombek, M.P.; Warner, N.H.; Ganti, V.; Lamb, M.P.; Parker, T.J.; Fergason, Robin L.; Sullivan, R.

2014-01-01

A morphometric and morphologic catalog of ~100 small craters imaged by the Opportunity rover over the 33.5 km traverse between Eagle and Endeavour craters on Meridiani Planum shows craters in six stages of degradation that range from fresh and blocky to eroded and shallow depressions ringed by planed off rim blocks. The age of each morphologic class from Mars over ~100 Myr and 3 Gyr timescales from the Amazonian and Hesperian are of order <0.01 m/Myr, which is 3–4 orders of magnitude slower than typical terrestrial rates. Erosion rates during the Middle-Late Noachian averaged over ~250 Myr, and ~700 Myr intervals are around 1 m/Myr, comparable to slow terrestrial erosion rates calculated over similar timescales. This argues for a wet climate before ~3 Ga in which liquid water was the erosional agent, followed by a dry environment dominated by slow eolian erosion.

Analysis of gross error rates in operation of commercial nuclear power stations

International Nuclear Information System (INIS)

Joos, D.W.; Sabri, Z.A.; Husseiny, A.A.

1979-01-01

Experience in operation of US commercial nuclear power plants is reviewed over a 25-month period. The reports accumulated in that period on events of human error and component failure are examined to evaluate gross operator error rates. The impact of such errors on plant operation and safety is examined through the use of proper taxonomies of error, tasks and failures. Four categories of human errors are considered; namely, operator, maintenance, installation and administrative. The computed error rates are used to examine appropriate operator models for evaluation of operator reliability. Human error rates are found to be significant to a varying degree in both BWR and PWR. This emphasizes the import of considering human factors in safety and reliability analysis of nuclear systems. The results also indicate that human errors, and especially operator errors, do indeed follow the exponential reliability model. (Auth.)

Impact of life expectancy, literacy rate, opened unemployment rate and gross domestic regional income per capita on poverty in the districts/city in Central Sulawesi Province

Science.gov (United States)

Tombolotutu, A. D.; Djirimu, M. A.; Lutfi, M.; Anggadini, F.

2018-05-01

Research was conducted in several districts/city in Central Sulawesi Province in order to determine the effect of life expectancy, literacy rate, opened unemployment rate, and gross domestic regional income per capita on poverty at the districts/city in the province. The analysis used is Panel Data Regression. The results show that first, life expectancy and gross domestic regional income have a negative and significant impact on the poverty level in the districts/city in the Province. Second, the opened unemployment rate has a positive and significant effect on the poverty level in the districts/city in the province. Third, literacy rates show a positive effect and insignificant effect on the poverty level in the districts/city in the Province of Central Sulawesi. Fourth, these four variables simultaneously affect the poverty in the districts/city in Central Sulawesi

Application of the 137Cs determination to evaluate the erosion rates in cultivated soils in the west part of Cuba

International Nuclear Information System (INIS)

Gil Castillo, Reinaldo; Peralta Vital, Jose Luis; Carrazana Gonzalez, Jorge; Riverol Rosquet, Mario; Penna Valenti, Fermin; Cabrera Calcedo, Eduardo

2004-01-01

The paper shows the experience in the application of 137Cs technique to estimate the erosion rates in cultivated soils (Ultisol) in the west part of the country, and the validation of the technique results by comparison against the results from traditional methods (watershed segments). The proportional, the simplified balance of mass and the balance of mass models were used to calculate the erosion rates, for three segments. In the evaluated area, have been obtained erosion rates from 3.5 to 7.1 t/ha/y for the segment I, from 5.17 to 10.3 t/ha/y for the segment III and from 2.3 to 17 t/ha/y for the segment IX. The conclusions are, the 137Cs technique is reliable for the estimation of erosion rates in the evaluated soil and the mass balance model obtained the nearest values to the estimated by watershed segments

Modulation of the erosion rate of an uplifting landscape by long-term climate change: An experimental investigation

Science.gov (United States)

Moussirou, Bérangé; Bonnet, Stéphane

2018-02-01

Whether or not climatic variations play a major role in setting the erosion rate of continental landscapes is a key factor in demonstrating the influence of climate on the tectonic evolution of mountain belts and understanding how clastic deposits preserved in sedimentary basins may record climatic variations. Here, we investigate how a change in precipitation influences the erosional dynamics of laboratory-scale landscapes that evolved under a combination of uplift and rainfall forcings. We consider here the impact of a decrease in the precipitation rate of finite duration on the erosive response of a landscape forced by a constant uplift and initially at a steady state (SS1). We performed several experiments with the same amplitude but different durations of precipitation decrease (Tp). We observe that the decrease in precipitation induces a phase of surface uplift of landscapes to a new steady state condition (SS2); however, the details of the uplift histories (timing, rate) differ between the experiments according to Tp. We also observe a decrease in the erosion rate induced by the precipitation change; however, the timing and amplitude of this decrease vary according to Tp, defining a delayed and damped erosion signal. Our data show that the landscape response to precipitation change is dictated by a critical water-to-rock ratio (ratio of precipitation over uplift) that likely corresponds to a geomorphic threshold. Our study suggests that variations in precipitation that occur at a geological time scale (> 106 years) may have a weak impact on the erosion of landscapes and on the delivery of siliciclastic material to large rivers and sedimentary basins.

Erosivity, surface runoff, and soil erosion estimation using GIS-coupled runoff-erosion model in the Mamuaba catchment, Brazil.

Science.gov (United States)

Marques da Silva, Richarde; Guimarães Santos, Celso Augusto; Carneiro de Lima Silva, Valeriano; Pereira e Silva, Leonardo

2013-11-01

This study evaluates erosivity, surface runoff generation, and soil erosion rates for Mamuaba catchment, sub-catchment of Gramame River basin (Brazil) by using the ArcView Soil and Water Assessment Tool (AvSWAT) model. Calibration and validation of the model was performed on monthly basis, and it could simulate surface runoff and soil erosion to a good level of accuracy. Daily rainfall data between 1969 and 1989 from six rain gauges were used, and the monthly rainfall erosivity of each station was computed for all the studied years. In order to evaluate the calibration and validation of the model, monthly runoff data between January 1978 and April 1982 from one runoff gauge were used as well. The estimated soil loss rates were also realistic when compared to what can be observed in the field and to results from previous studies around of catchment. The long-term average soil loss was estimated at 9.4 t ha(-1) year(-1); most of the area of the catchment (60%) was predicted to suffer from a low- to moderate-erosion risk (soil erosion was estimated to exceed > 12 t ha(-1) year(-1). Expectedly, estimated soil loss was significantly correlated with measured rainfall and simulated surface runoff. Based on the estimated soil loss rates, the catchment was divided into four priority categories (low, moderate, high and very high) for conservation intervention. The study demonstrates that the AvSWAT model provides a useful tool for soil erosion assessment from catchments and facilitates the planning for a sustainable land management in northeastern Brazil.

Extracting information on the spatial variability in erosion rate stored in detrital cooling age distributions in river sands

Science.gov (United States)

Braun, Jean; Gemignani, Lorenzo; van der Beek, Peter

2018-03-01

One of the main purposes of detrital thermochronology is to provide constraints on the regional-scale exhumation rate and its spatial variability in actively eroding mountain ranges. Procedures that use cooling age distributions coupled with hypsometry and thermal models have been developed in order to extract quantitative estimates of erosion rate and its spatial distribution, assuming steady state between tectonic uplift and erosion. This hypothesis precludes the use of these procedures to assess the likely transient response of mountain belts to changes in tectonic or climatic forcing. Other methods are based on an a priori knowledge of the in situ distribution of ages to interpret the detrital age distributions. In this paper, we describe a simple method that, using the observed detrital mineral age distributions collected along a river, allows us to extract information about the relative distribution of erosion rates in an eroding catchment without relying on a steady-state assumption, the value of thermal parameters or an a priori knowledge of in situ age distributions. The model is based on a relatively low number of parameters describing lithological variability among the various sub-catchments and their sizes and only uses the raw ages. The method we propose is tested against synthetic age distributions to demonstrate its accuracy and the optimum conditions for it use. In order to illustrate the method, we invert age distributions collected along the main trunk of the Tsangpo-Siang-Brahmaputra river system in the eastern Himalaya. From the inversion of the cooling age distributions we predict present-day erosion rates of the catchments along the Tsangpo-Siang-Brahmaputra river system, as well as some of its tributaries. We show that detrital age distributions contain dual information about present-day erosion rate, i.e., from the predicted distribution of surface ages within each catchment and from the relative contribution of any given catchment to the

Extracting information on the spatial variability in erosion rate stored in detrital cooling age distributions in river sands

Directory of Open Access Journals (Sweden)

J. Braun

2018-03-01

Full Text Available One of the main purposes of detrital thermochronology is to provide constraints on the regional-scale exhumation rate and its spatial variability in actively eroding mountain ranges. Procedures that use cooling age distributions coupled with hypsometry and thermal models have been developed in order to extract quantitative estimates of erosion rate and its spatial distribution, assuming steady state between tectonic uplift and erosion. This hypothesis precludes the use of these procedures to assess the likely transient response of mountain belts to changes in tectonic or climatic forcing. Other methods are based on an a priori knowledge of the in situ distribution of ages to interpret the detrital age distributions. In this paper, we describe a simple method that, using the observed detrital mineral age distributions collected along a river, allows us to extract information about the relative distribution of erosion rates in an eroding catchment without relying on a steady-state assumption, the value of thermal parameters or an a priori knowledge of in situ age distributions. The model is based on a relatively low number of parameters describing lithological variability among the various sub-catchments and their sizes and only uses the raw ages. The method we propose is tested against synthetic age distributions to demonstrate its accuracy and the optimum conditions for it use. In order to illustrate the method, we invert age distributions collected along the main trunk of the Tsangpo–Siang–Brahmaputra river system in the eastern Himalaya. From the inversion of the cooling age distributions we predict present-day erosion rates of the catchments along the Tsangpo–Siang–Brahmaputra river system, as well as some of its tributaries. We show that detrital age distributions contain dual information about present-day erosion rate, i.e., from the predicted distribution of surface ages within each catchment and from the relative contribution of

Contributions of solar-wind induced potential sputtering to the lunar surface erosion rate and it's exosphere

Science.gov (United States)

Alnussirat, S. T.; Barghouty, A. F.; Edmunson, J. E.; Sabra, M. S.; Rickman, D. L.

2018-04-01

Sputtering of lunar regolith by solar-wind protons and heavy ions with kinetic energies of about 1 keV/amu is an important erosive process that affects the lunar surface and exosphere. It plays an important role in changing the chemical composition and thickness of the surface layer, and in introducing material into the exosphere. Kinetic sputtering is well modeled and understood, but understanding of mechanisms of potential sputtering has lagged behind. In this study we differentiate the contributions of potential sputtering from the standard (kinetic) sputtering in changing the chemical composition and erosion rate of the lunar surface. Also we study the contribution of potential sputtering in developing the lunar exosphere. Our results show that potential sputtering enhances the total characteristic sputtering erosion rate by about 44%, and reduces sputtering time scales by the same amount. Potential sputtering also introduces more material into the lunar exosphere.

OEDGE modeling of outer wall erosion in NSTX and the effect of changes in neutral pressure

Energy Technology Data Exchange (ETDEWEB)

Nichols, J.H., E-mail: jnichols@pppl.gov; Jaworski, M.A.; Kaita, R.; Abrams, T.; Skinner, C.H.; Stotler, D.P.

2015-08-15

Gross erosion from the outer wall is expected to be a major source of impurities for high power fusion devices due to the low redeposition fraction. Scaling studies of sputtering from the all-carbon outer wall of NSTX are reported. It is found that wall erosion decreases with divertor plasma pressure in low/mid temperature regimes, due to increasing divertor neutral opacity. Wall erosion is found to consistently decrease with reduced recycling coefficient, with outer target recycling providing the largest contribution. Upper and lower bounds are calculated for the increase in wall erosion due to a low-field-side gas puff.

The influence of incline and speed on work rate, gross efficiency and kinematics of roller ski skating.

Science.gov (United States)

Sandbakk, Øyvind; Ettema, Gertjan; Holmberg, Hans-Christer

2012-08-01

During competitions, elite cross-country skiers produce higher external work rates on uphill than on flat terrain. However, it is not presently known whether this reflects solely higher energy expenditure. Furthermore, the kinematic factors associated with these higher rates of uphill work have not yet been examined. Therefore, in the present investigation the work rate and associated kinematic parameters at similar metabolic rates during roller ski skating on flat and uphill terrains have been compared. Seven elite male skiers performed six 5-min sub-maximal exercise bouts at the same low, moderate and high metabolic rates on 2 and 8% inclines, while roller skiing on a treadmill employing the G3 skating technique. The work rate was calculated as work against gravity and friction, whereas the energetic equivalent of VO(2) was taken as the metabolic rate. Gross efficiency was defined as work rate divided by metabolic rate. Kinematic parameters were analyzed in three dimensions. At the same metabolic rate, the work rate, cycle rate, work per cycle and relative duration of propulsive phases during a cycle of movement were all higher on the 8% than on the 2% incline at all speeds (all P < 0.05). At similar work rates, gross efficiency was greater on the 8% incline (P < 0.05). In conclusion, these elite skiers consistently demonstrated higher work rates on the 8% incline. To achieve the higher work rates on the steeper incline, these elite skiers employed higher cycle rates and performed more work per cycle, in association with a longer relative propulsive phase.

Protection from erosion following wildfire

Science.gov (United States)

Peter R. Robichaud; William J. Elliot

2006-01-01

Erosion in the first year after a wildfire can be up to three orders of magnitude greater than the erosion from undisturbed forests. To mitigate potential postfire erosion, various erosion control treatments are applied on highly erodible areas with downstream resources in need of protection. Because postfire erosion rates generally decline by an order of magnitude for...

Soil Erosion and Agricultural Sustainability

Science.gov (United States)

Montgomery, D. R.

2009-04-01

Data drawn from a global compilation of studies support the long articulated contention that erosion rates from conventionally plowed agricultural fields greatly exceed rates of soil production, erosion under native vegetation, and long-term geological erosion. Whereas data compiled from around the world show that soil erosion under conventional agriculture exceeds both rates of soil production and geological erosion rates by up to several orders of magnitude, similar global distributions of soil production and geological erosion rates suggest an approximate balance. Net soil erosion rates in conventionally plowed fields on the order of 1 mm/yr can erode typical hillslope soil profiles over centuries to millennia, time-scales comparable to the longevity of major civilizations. Well-documented episodes of soil loss associated with agricultural activities date back to the introduction of erosive agricultural methods in regions around the world, and stratigraphic records of accelerated anthropogenic soil erosion have been recovered from lake, fluvial, and colluvial stratigraphy, as well as truncation of soil stratigraphy (such as truncated A horizons). A broad convergence in the results from studies based on various approaches employed to study ancient soil loss and rates of downstream sedimentation implies that widespread soil loss has accompanied human agricultural intensification in examples drawn from around the world. While a broad range of factors, including climate variability and society-specific social and economic contexts — such as wars or colonial relationships — all naturally influence the longevity of human societies, the ongoing loss of topsoil inferred from studies of soil erosion rates in conventional agricultural systems has obvious long-term implications for agricultural sustainability. Consequently, modern agriculture — and therefore global society — faces a fundamental question over the upcoming centuries. Can an agricultural system

Buffer erosion in dilute groundwater

International Nuclear Information System (INIS)

Schatz, T.; Kanerva, N.; Martikainen, J.; Sane, P.; Olin, M.; Seppaelae, A.; Koskinen, K.

2013-08-01

One scenario of interest for repository safety assessment involves the loss of bentonite buffer material in contact with dilute groundwater flowing through a transmissive fracture interface. In order to examine the extrusion/erosion behavior of bentonite buffer material under such circumstances, a series of experiments were performed in a flow-through, 1 mm aperture, artificial fracture system. These experiments covered a range of solution chemistry (salt concentration and composition), material composition (sodium montmorillonite and admixtures with calcium montmorillonite), and flow velocity conditions. No erosion was observed for sodium montmorillonite against solution compositions from 0.5 g/L to 10 g/L NaCl. No erosion was observed for 50/50 calcium/sodium montmorillonite against 0.5 g/L NaCl. Erosion was observed for both sodium montmorillonite and 50/50 calcium/sodium montmorillonite against solution compositions ≤ 0.25 g/L NaCl. The calculated erosion rates for the tests with the highest levels of measured erosion, i.e., the tests run under the most dilute conditions (ionic strength (IS) < ∼1 mM), were well-correlated to flow velocity, whereas the calculated erosion rates for the tests with lower levels of measured erosion, i.e., the tests run under somewhat less dilute conditions (∼1 mM < IS < ∼4 mM), were not similarly correlated indicating that material and solution composition can significantly affect erosion rates. In every experiment, both erosive and non-erosive, emplaced buffer material extruded into the fracture and was observed to be impermeable to water flowing in the fracture effectively forming an extended diffusive barrier around the intersecting fracture/buffer interface. Additionally, a model which was developed previously to predict the rate of erosion of bentonite buffer material in low ionic strength water in rock fracture environments was applied to three different cases: sodium montmorillonite expansion in a vertical tube, a

Centennial- to millennial-scale hard rock erosion rates deduced from luminescence-depth profiles

DEFF Research Database (Denmark)

Sohbati, Reza; Liu, Jinfeng; Jain, Mayank

2018-01-01

to quantify hard rock erosion rates at centennial to millennial timescales. Here we propose a novel technique, based on the solar bleaching of luminescence signals with depth into rock surfaces, to bridge this analytical gap. We apply our technique to glacial and landslide boulders in the Eastern Pamirs...

Effects of oil on the rate and trajectory of Louisiana marsh shoreline erosion

International Nuclear Information System (INIS)

McClenachan, Giovanna; Eugene Turner, R; Tweel, Andrew W

2013-01-01

Oil can have long-term detrimental effects on marsh plant health, both above- and belowground. However, there are few data available that quantify the accelerated rate of erosion that oil may cause to marshes and the trajectory of change. Between November 2010 and August 2012, we collected data on shoreline erosion, soil strength, per cent cover of Spartina alterniflora, and marsh edge overhang at 30 closely spaced low oil and high oil sites in Bay Batiste, Louisiana. Surface oil samples were taken one meter into the marsh in February 2011. All high oiled sites in Bay Batiste were contaminated with Macondo 252 oil (oil from the Deepwater Horizon oil spill, 20 April–15 July 2010). The results suggest that there is a threshold where soil parameters change dramatically with a relatively small increase in oil concentration in the soil. Heavy oiling weakens the soil, creating a deeper undercut of the upper 50 cm of the marsh edge, and causing an accelerated rate of erosion that cascades along the shoreline. Our results demonstrate that it could take at least 2 yr to document the effects heavy oiling has had on the marsh shoreline. The presence of aboveground vegetation alone may not be an appropriate indicator of recovery. (letter)

Comparison of soil erosion and deposition rates using radiocesium, RUSLE, and buried soils in dolines in East Tennessee

International Nuclear Information System (INIS)

Turnage, K.M.; Lee, S.Y.; Foss, J.E.; Kim, K.H.; Larsen, I.L.

1997-01-01

Three dolines (sinkholes), each representing different land uses (crop, grass, and forest) in a karst area in East Tennesse, were selected to determine soil erosional and depositional rates. Three methods were used to estimate the rates: fallout radiocesium ( 137 Cs) redistribution, buried surface soil horizons (Ab horizon), and the revised universal soil loss equation (RUSLE). When 137 Cs redistribution was examined, the average soil erosion rates were calculated to be 27 t ha -1 yr -1 at the cropland, 3 t ha -1 yr -1 at the grassland, and 2 t ha -1 yr -1 at the forest. By comparison, cropland erosion rate of 2.6 t ha -1 yr -1 , a grassland rate of 0.6 t ha -1 yr -1 , and a forest rate of 0.2 t ha -1 yr -1 were estimated by RUSLE. The 137 Cs method expressed higher rates than RUSLE because RUSLE tends to overestimate low erosion rates and does not account for deposition. The buried surface horizons method resulted in deposition rates that were 8 t ha -1 yr -1 (during 480 yr) at the cropland, 12 t ha -1 yr -1 (during 980 yr) at the grassland, and 4 t ha -1 yr -1 (during 101 yr) at the forest site. By examining 137 Cs redistribution, soil deposition rates were found to be 23 t ha -1 yr -1 at the cropland, 20 t ha -1 yr -1 at the grassland, and 16 t ha -1 yr -1 at the forest site. The variability in deposition rates was accounted for by temporal differences; 137 Cs expressed deposition during the last 38 yr, whereas Ab horizons represented deposition during hundreds of years. In most cases, land used affected both erosion and deposition rates - the highest rates of soil redistribution usually representing the cropland and the lowest, the forest. When this was not true, differences in the rates were attributed to differences in the size, shape, and closure of the dolines. (orig.)

Quantifying accelerated soil erosion through ecological site-based assessments of wind and water erosion

Science.gov (United States)

This work explores how organising soil erosion assessments using established groupings of similar soils (ecological sites) can inform systems for managing accelerated soil erosion. We evaluated aeolian sediment transport and fluvial erosion rates for five ecological sites in southern New Mexico, USA...

Assessment of soil erosion and deposition rates in a Moroccan agricultural field using fallout 137Cs and 210Pbex.

Science.gov (United States)

Benmansour, M; Mabit, L; Nouira, A; Moussadek, R; Bouksirate, H; Duchemin, M; Benkdad, A

2013-01-01

In Morocco land degradation - mainly caused by soil erosion - is one of the most serious agroenvironmental threats encountered. However, only limited data are available on the actual magnitude of soil erosion. The study site investigated was an agricultural field located in Marchouch (6°42' W, 33° 47' N) at 68 km south east from Rabat. This work demonstrates the potential of the combined use of (137)Cs, (210)Pb(ex) as radioisotopic soil tracers to estimate mid and long term erosion and deposition rates under Mediterranean agricultural areas. The net soil erosion rates obtained were comparable, 14.3 t ha(-1) yr(-1) and 12.1 ha(-1) yr(-1) for (137)Cs and (210)Pb(ex) respectively, resulting in a similar sediment delivery ratio of about 92%. Soil redistribution patterns of the study field were established using a simple spatialisation approach. The resulting maps generated by the use of both radionuclides were similar, indicating that the soil erosion processes has not changed significantly over the last 100 years. Over the previous 10 year period, the additional results provided by the test of the prediction model RUSLE 2 provided results of the same order of magnitude. Based on the (137)Cs dataset established, the contribution of the tillage erosion impact has been evaluated with the Mass Balance Model 3 and compared to the result obtained with the Mass Balance Model 2. The findings highlighted that water erosion is the leading process in this Moroccan cultivated field, tillage erosion under the experimental condition being the main translocation process within the site without a significant and major impact on the net erosion. Copyright © 2012 Elsevier Ltd. All rights reserved.

Gross Domestic Savings and Gross Capital: what Matters to Their Formation in an Era of Economic Recession in Nigeria?

Directory of Open Access Journals (Sweden)

Success Abusomwan

2017-09-01

Full Text Available The objective of this study is to empirically investigate the long run and short run dynamic impact of interest rate and output on gross domestic savings and gross capital formation in Nigeria. Literatures, both theoretical and empirical, suggest that the rate of interest and output are the key factors influencing savings and investments. A review of factors influencing interest rates and output in Nigeria is necessitated by the recent economic downturns in Nigeria that has resulted in tight monetary policy which some commentators regard as inimical to growth. Employing Ordinary Least Squares, Co-integration, Error Correction Mechanism and Granger Causality econometric techniques on a data spanning 1981 to 2014 of the Nigerian economy sourced from the World Development Index, it was found that changes in output explains the long run and short run dynamic behaviour of gross domestic savings and gross capital formation which were used as proxies for savings and investment respectively. Whereas, a bi-causality was established between output and investment, causality flowed from output to savings in Nigeria. The research also found that interest rate is not a significant determinant of savings and investment in Nigeria in both long run and short run. It is therefore recommended that to enhance investment in a period of economic downturn in Nigeria, aggregate demand should be boosted to enhance output through vigorous pursuit of fiscal policy while implementing contractionary monetary policy to address inflationary pressures created by the increase in demand. Domestic savings will improve and gross capital formation will be sustained.

Soil erosion and sedimentation rates in a small eutrophic lake in southern Chile estimated by 210Pb isotope analysis

International Nuclear Information System (INIS)

Cisternas, M.; Urrutia, R.; Araneda, A.; Debels, P.; Rios, F.

1999-01-01

The purpose of this research is to study the effects of historical land use patterns on soil erosion within the San Pedro Lake watershed (Concepcion, VIII Region, Chile). To this end, a geochronological reconstruction of the last 50 years was accomplished by 210 Pb isotope and photo-interpretation analysis through the use of GIS. The erosion rate has varied from 0.40 t ha -1 y -1 in 1955 to 0.86 t ha -1 y -1 in 1994. The decrease in native forest was closely coupled with the increase in exotic forestry. The Total Change, meaning the land use change without considering each typology, shows a constant trend indicating a greater degree of anthropogenic intervention. As opposed to the expected, there is no relationship between land use typologies and erosion rates, however it is possible to recognise some degree of dependency between Total Change and erosion values. It is concluded that over the last 50 years the soil erosion processes in the San Pedro Lake watershed may have been more regulated more by land use changes than by land use typologies themselves. (author)

Determining the rates and drivers of headwall erosion within glaciated catchments in the NW Himalaya

Science.gov (United States)

Orr, E.; Owen, L. A.; Saha, S.; Caffee, M. W.

2017-12-01

Rates of headwall erosion are defined for fourteen glaciated catchments in the NW Himalaya by measuring 10Be terrestrial cosmogenic nuclide concentrations in supraglacial debris. The investigated catchments are located throughout three broad climatic zones, which include the Lesser Himalaya (rainfall >1000 mm a-1), Greater Himalaya (500-1000 mm a-1) and Transhimalaya (arid catchments that are occupied by sub-polar glaciers, suggesting that there are additional controls upon periglacial domain landscape change. Other factors and catchment-specific dynamics influencing these landscapes include, temperature, surface processes, topography, valley morphology, geologic setting and glacial history. Defining rates of headwall erosion is one of the first steps to understanding the nature of sediment production and transfer within high-altitude glaciated catchments, and highlights the importance of periglacial rockfall processes in landscape evolution.

7 CFR 1424.7 - Gross payable units.

Science.gov (United States)

2010-01-01

... payments (APP), and base production payments (BPP). Repayment rates shall be based on previous payment... 50 gallons of net production increase. (2) For BPP, which will be made on production not eligible for... biodiesel production gross payable units. (3) Adding the APP and BPP to determine biodiesel gross payable...

In-situ buildup of cosmogenic isotopes at the earth's surface: measurement of erosion rates and exposure times

International Nuclear Information System (INIS)

Fifield, L.K.; Allan, G.L.; Stone, J.O.H.; Evans, J.M.; Cresswell, R.G.; Ophel, T.R.

1993-01-01

Cosmic rays produce a number of nuclides in rocks that can be used to determine the geomorphic history of surfaces. The most useful are the radioactive isotopes 10 Be (t 1/2 = 1.5Ma), 26 Al (0.7Ma) and 36 Cl (0.3Ma). Within the top 2m of the surface, these are produced principally by fast neutrons. At greater depths, production is dominated by the capture of negative muons. Measurements of a single nuclide produced in situ can be used to determine total exposure times or erosion rates. The use of multiple nuclides with different half-lives makes it possible to determine more complex histories, such as exposures interrupted by periods of burial. At the ANU, all three of the isotopes above are being used to study a variety of problems in geomorphology and paleoclimatology, although to date, most of the work has concentrated on 36 Cl. The accumulation of cosmogenic 36 Cl in calcite (CaCO 3 ) provides a means of measuring erosion rates on limestone surfaces. Sensitivity is achieved over a wide range of erosion rates due to the high production rate of 36 Cl in calcite (typically greater than 30 atoms/g/yr) and a detection limit of ca. 5000 atoms/g attainable with the ANU AMS system. The method is simplified by the predominance of Ca reactions (principally spallation) over other sources of 36 Cl in calcite, and the ease of sample preparation. This presentation discuss the results of measurements of 36 Cl in calcite from limestone samples from Australia and Papua New Guinea. Erosion rates derived from these measurements range from 3 microns per year (Australia) to over 200 microns per year in the New Guinea highlands. 3 refs

The effect of wet-dry weathering on the rate of bedrock river channel erosion by saltating gravel

Science.gov (United States)

Inoue, Takuya; Yamaguchi, Satomi; Nelson, Jonathan M.

2017-01-01

Previous work has shown that the bedrock erosion rate E because of collisions of saltating bedload can be expressed by E = βqb(1-Pc), where qb is the sediment transport rate, Pc is the extent of alluvial cover, and β is the abrasion coefficient. However, the dependence of the abrasion coefficient on the physical characteristics of the bedrock material is poorly known, and in particular, the effects of wet-dry weathering on the saltation-abrasion bedrock incision has not been specifically characterized. Observation suggests that the typical wet-dry cycling of exposed bedrock in river beds gives rise to cracks and voids that are likely to alter the incision rate of the material when subjected to impacts of moving sediment. In this study, flume experiments are performed to develop an understanding of how wet-dry cycling affects the rock tensile strength and the bedrock erosion rate. To represent the physical effects of weathering, boring cores taken from natural bedrock channel are exposed to artificial wet-dry cycles. The experimental results suggest the following: (1) the abrasion coefficient for fresh bedrock is estimated by β = 1.0 × 10− 4σT− 2(d/ksb)0.5, where σT is the tensile strength, d is the diameter of colliding gravel, and ksb is the hydraulic roughness height of bedrock; (2) the tensile strength of the bedrock decreases exponentially as a result of repeated wet-dry cycles, σT/σT0 = exp (-CTNWa0/σT0), where σT0 is the initial tensile strength, Wa0 is the initial normalized rate of water absorption., N is the number of wet-dry cycles, and CT is a constant; (3) the erosion rate of fresh bedrock depends on the inverse of the square of tensile strength, but the erosion rate of weathered bedrock depends on the − 1.5 power of tensile strength.

Scenario Studies on Effects of Soil Infiltration Rates, Land Slope, and Furrow Irrigation Characteristics on Furrow Irrigation-Induced Erosion.

Science.gov (United States)

Dibal, Jibrin M; Ramalan, A A; Mudiare, O J; Igbadun, H E

2014-01-01

Furrow irrigation proceeds under several soil-water-furrow hydraulics interaction dynamics. The soil erosion consequences from such interactions in furrow irrigation in Samaru had remained uncertain. A furrow irrigation-induced erosion (FIIE) model was used to simulate the potential severity of soil erosion in irrigated furrows due to interactive effects of infiltration rates, land slope, and some furrow irrigation characteristics under different scenarios. The furrow irrigation characteristics considered were furrow lengths, widths, and stream sizes. The model itself was developed using the dimensional analysis approach. The scenarios studied were the interactive effects of furrow lengths, furrow widths, and slopes steepness; infiltration rates and furrow lengths; and stream sizes, furrow lengths, and slopes steepness on potential furrow irrigation-induced erosion, respectively. The severity of FIIE was found to relate somewhat linearly with slope and stream size, and inversely with furrow lengths and furrow width. The worst soil erosion (378.05 t/ha/yr) was found as a result of the interactive effects of 0.65 m furrow width, 50 m furrow length, and 0.25% slope steepness; and the least soil erosion (0.013 t/ha/yr) was induced by the combined effects of 0.5 l/s, 200 m furrow length, and 0.05% slope steepness. Evidently considering longer furrows in furrow irrigation designs would be a better alternative of averting excessive FIIE.

On researching erosion-corrosion wear in pipelines: the rate and residual lifetime estimation

International Nuclear Information System (INIS)

Baranenko, V.I.; Yanchenko, Yu.A.; Gulina, O.M.; Dokukin, D.A.

2010-01-01

To base the normative document on calculation of pipelines erosive-corrosive wear (ECW) rate and residual lifetime this research of ECW regularities for pearlitic steel NPP pipelines was performed. The estimates of control data treatment statistical procedures efficiency were presented. The influence of the scheme of piping control on the ECW rate and residual lifetime estimation results was demonstrated. The simplified scheme is valid only in case of complete information. It's usage under data uncertainties leads to essential residual lifetime overstating [ru

The comparison of various approach to evaluation erosion risks and design control erosion measures

Science.gov (United States)

Kapicka, Jiri

2015-04-01

In the present is in the Czech Republic one methodology how to compute and compare erosion risks. This methodology contain also method to design erosion control measures. The base of this methodology is Universal Soil Loss Equation (USLE) and their result long-term average annual rate of erosion (G). This methodology is used for landscape planners. Data and statistics from database of erosion events in the Czech Republic shows that many troubles and damages are from local episodes of erosion events. An extent of these events and theirs impact are conditional to local precipitation events, current plant phase and soil conditions. These erosion events can do troubles and damages on agriculture land, municipally property and hydro components and even in a location is from point of view long-term average annual rate of erosion in good conditions. Other way how to compute and compare erosion risks is episodes approach. In this paper is presented the compare of various approach to compute erosion risks. The comparison was computed to locality from database of erosion events on agricultural land in the Czech Republic where have been records two erosion events. The study area is a simple agriculture land without any barriers that can have high influence to water flow and soil sediment transport. The computation of erosion risks (for all methodology) was based on laboratory analysis of soil samples which was sampled on study area. Results of the methodology USLE, MUSLE and results from mathematical model Erosion 3D have been compared. Variances of the results in space distribution of the places with highest soil erosion where compared and discussed. Other part presents variances of design control erosion measures where their design was done on based different methodology. The results shows variance of computed erosion risks which was done by different methodology. These variances can start discussion about different approach how compute and evaluate erosion risks in areas

Crust behavior and erosion rate prediction of EPR sacrificial material impinged by core melt jet

Energy Technology Data Exchange (ETDEWEB)

Li, Gen; Liu, Ming, E-mail: ming.liu@mail.xjtu.edu.cn; Wang, Jinshi; Chong, Daotong; Yan, Junjie

2017-04-01

Highlights: • A numerical code was developed to analyze melt jet-concrete interaction in the frame of MPS method. • Crust and ablated concrete layer at UO{sub 2}-ZrO{sub 2} melt and concrete interface periodically developed and collapsed. • Concrete surface temperature fluctuated around a low temperature and ablation temperature. • Concrete erosion by Fe-Zr melt jet was significantly faster than that by UO{sub 2}-ZrO{sub 2} melt jet. - Abstract: Sacrificial material is a special ferro-siliceous concrete, designed in the ex-vessel core melt stabilization system of European Pressurized water Reactor (EPR). Given a localized break of RPV lower head, the melt directly impinges onto the dry concrete in form of compact jet. The concrete erosion behavior influences the failure of melt plug, and further affects melt spreading. In this study, a numerical code was developed in the frame of Moving Particle Semi-implicit (MPS) method, to analyze the crust behavior and erosion rate of sacrificial concrete, impinged by prototypic melt jet. In validation of numerical modeling, the time-dependent erosion depth and erosion configuration matched well with the experimental data. Sensitivity study of sacrificial concrete erosion indicates that the crust and ablated concrete layer presented at UO{sub 2}-ZrO{sub 2} melt and concrete interface, whereas no crust could be found in the interaction of Fe-Zr melt with concrete. The crust went through stabilization-fracture-reformation periodic process, accompanied with accumulating and collapsing of molten concrete layer. The concrete surface temperature fluctuated around a low temperature and ablation temperature. It increased as the concrete surface layer was heated to melting, and dropped down when the cold concrete was revealed. The erosion progression was fast in the conditions of small jet diameter and large concrete inclination angle, and it was significantly faster in the erosion by metallic melt jet than by oxidic melt jet.

STUDY OF RAINFALL RATES AND EROSIVE PROCESSES AT THE URBAN AREA OF SÃO LUÍS – MA

Directory of Open Access Journals (Sweden)

Antonio José Teixeira Guerra

2005-05-01

Full Text Available The study of the rain rates is here highlighted, in order to understand the mechanisms that generate the starting point of the erosive processes. The precipitation varies spatially not only in local and regional levels, due to mechanisms that generate rains, but also in short distances, due to the control of local variations, such as winds and constructions. In this way, the precipitations should be measured in different points of the study area, depending on the interest of the study and scale of analysis.The erosive process caused by rainfall covers almost the whole terrestrial surface, especially in tropical areas where the total rainfall is higher than in other regions of the planet. Besides that, the rain only falls on specific seasons in several areas, which worsens the erosion. The process tends to accelerate as the deforestation for wood exploitation and/or agricultural production takes place, once the soils become unprotected without the vegetal cover, so that the rains affect the surface of the grounds directly (GUERRA, 1999.This work presents the results of the monitoring of erosive processes along more than three years of studies at the urban area of São Luís City, relating rainfall rates to gullies evolution, an important instrument for the control and recovery of large-scale erosive processes.

Effect of temperate climate tree species on gross ammonification, gross nitrification and N2O formation

Science.gov (United States)

Brüggemann, N.; Rosenkranz, P.; Papen, H.; Butterbach-Bahl, K.

2003-04-01

Microbial nitrogen turnover processes in the soil, like ammonification, nitrification and denitrification, play an important role in the formation of nitrous oxide (N2O): (i) ammonification, because it releases nitrogen from organic material in the form of ammonium (NH4+), which in turn can serve as substrate for nitrification; (ii) nitrification itself (i.e. the turnover of NH4+ to nitrate, NO3-), during which nitric oxide (NO) and N2O can be released as by-products at varying ratios; (iii) denitrification, in which NO3- serves as electron acceptor and is converted to molecular nitrogen (N2) via NO and N2O as intermediates, that can also be partially lost to the atmosphere. Temperate forest soils are a substantial source of atmospheric N2O contributing up to 10% to the total atmospheric N2O budget. However, this figure is afflicted with a huge uncertainty due to a number of factors governing the soil N2O formation, consumption, release and uptake, which are not fully understood at present. To one of these factors belongs the influence of the tree species on nitrogen turnover processes in the soil and the formation of N trace gases related with them. The aim of the present work was to analyse this tree species effect for the temperate climate region. For this purpose the effect of five different temperate tree species, having the same age and growing on the same soil in direct vicinity to each other, on gross ammonification and gross nitrification as well as on N2O formation was investigated. The trees (common beech, Fagus sylvatica; pedunculate oak, Quercus robur; Norway spruce, Picea abies; Japanese larch, Larix leptolepis; mountain pine, Pinus mugo) were part of a species trial in Western Jutland, Denmark, established in 1965 on a former sandy heathland. Samples from the soil under these five tree species were taken in spring and in summer 2002, respectively, differentiating between organic layer and mineral soil. The gross rates of ammonification as well of

A simplified 137Cs transport model for estimating erosion rates in undisturbed soil

International Nuclear Information System (INIS)

Zhang Xinbao; Long Yi; He Xiubin; Fu Jiexiong; Zhang Yunqi

2008-01-01

137 Cs is an artificial radionuclide with a half-life of 30.12 years which released into the environment as a result of atmospheric testing of thermo-nuclear weapons primarily during the period of 1950s-1970s with the maximum rate of 137 Cs fallout from atmosphere in 1963. 137 Cs fallout is strongly and rapidly adsorbed by fine particles in the surface horizons of the soil, when it falls down on the ground mostly with precipitation. Its subsequent redistribution is associated with movements of the soil or sediment particles. The 137 Cs nuclide tracing technique has been used for assessment of soil losses for both undisturbed and cultivated soils. For undisturbed soils, a simple profile-shape model was developed in 1990 to describe the 137 Cs depth distribution in profile, where the maximum 137 Cs occurs in the surface horizon and it exponentially decreases with depth. The model implied that the total 137 Cs fallout amount deposited on the earth surface in 1963 and the 137 Cs profile shape has not changed with time. The model has been widely used for assessment of soil losses on undisturbed land. However, temporal variations of 137 Cs depth distribution in undisturbed soils after its deposition on the ground due to downward transport processes are not considered in the previous simple profile-shape model. Thus, the soil losses are overestimated by the model. On the base of the erosion assessment model developed by Walling, D.E., He, Q. [1999. Improved models for estimating soil erosion rates from cesium-137 measurements. Journal of Environmental Quality 28, 611-622], we discuss the 137 Cs transport process in the eroded soil profile and make some simplification to the model, develop a method to estimate the soil erosion rate more expediently. To compare the soil erosion rates calculated by the simple profile-shape model and the simple transport model, the soil losses related to different 137 Cs loss proportions of the reference inventory at the Kaixian site of the

Using "1"3"7Cs measurements to estimate soil erosion rates in the Pčinja and South Morava River Basins, southeastern Serbia

International Nuclear Information System (INIS)

Petrović, Jelena; Dragović, Snežana; Dragović, Ranko; Đorđević, Milan; Đokić, Mrđan; Zlatković, Bojan; Walling, Desmond

2016-01-01

The need for reliable assessments of soil erosion rates in Serbia has directed attention to the potential for using "1"3"7Cs measurements to derive estimates of soil redistribution rates. Since, to date, this approach has not been applied in southeastern Serbia, a reconnaissance study was undertaken to confirm its viability. The need to take account of the occurrence of substantial Chernobyl fallout was seen as a potential problem. Samples for "1"3"7Cs measurement were collected from a zone of uncultivated soils in the watersheds of Pčinja and South Morava Rivers, an area with known high soil erosion rates. Two theoretical conversion models, the profile distribution (PD) model and diffusion and migration (D&M) model were used to derive estimates of soil erosion and deposition rates from the "1"3"7Cs measurements. The estimates of soil redistribution rates derived by using the PD and D&M models were found to differ substantially and this difference was ascribed to the assumptions of the simpler PD model that cause it to overestimate rates of soil loss. The results provided by the D&M model were judged to more reliable. - Highlights: • The "1"3"7Cs measurements are employed to estimate the soil erosion and deposition rates in southeastern Serbia. • Estimates of annual soil loss by profile distribution (PD) and diffusion and migration (D&M) models differ significantly. • Differences were ascribed to the assumptions of the simpler PD model which cause it to overestimate rates of soil loss. • The study confirmed the potential for using "1"3"7Cs measurements to estimate soil erosion rates in Serbia.

Interactions between land-use history and earthworms control gross rates of soil methane production in an overwintering pasture

Czech Academy of Sciences Publication Activity Database

Bradley, R.L.; Chroňáková, Alica; Elhottová, Dana; Šimek, Miloslav

2012-01-01

Roč. 53, October (2012), s. 64-71 ISSN 0038-0717 R&D Projects: GA ČR GA526/09/1570 Institutional support: RVO:60077344 Keywords : earthworms * gross methane transformation rates * isotope dilution * land-use history Subject RIV: EH - Ecology, Behaviour Impact factor: 3.654, year: 2012

The contribution of mulches to control high soil erosion rates in vineyards in Eastern Spain

Science.gov (United States)

Cerdà, Artemi; Jordán, Antonio; Zavala, Lorena; José Marqués, María; Novara, Agata

2014-05-01

Soil erosion take place in degraded ecosystem where the lack of vegetation, drought, erodible parent material and deforestation take place (Borelli et al., 2013; Haregeweyn et al., 2013; Zhao et al., 2013). Agriculture management developed new landscapes (Ore and Bruins, 2012) and use to trigger non-sustainable soil erosion rates (Zema et al., 2012). High erosion rates were measured in agriculture land (Cerdà et al., 2009), but it is also possible to develop managements that will control the soil and water losses, such as organic amendments (Marqués et al., 2005), plant cover (Marqués et al., 2007) and geotextiles (Giménez Morera et al., 2010). The most successful management to restore the structural stability and the biological activity of the agriculture soil has been the organic mulches (García Orenes et al; 2009; 2010; 2012). The straw mulch is also very successful on bare fire affected soil (Robichaud et al., 2013a; 2013b), which also contributes to a more stable soil moisture content (García-Moreno et al., 2013). The objective of this research is to determine the impact of two mulches: wheat straw and chipped branches, on the soil erosion rates in a rainfed vineyard in Eastern Spain. The research site is located in the Les Alcusses Valley within the Moixent municipality. The Mean annual temperature is 13 ºC, and the mean annual rainfall 455 mm. Soil are sandy loam, and are developed at the foot-slope of a Cretaceous limestone range, the Serra Grossa range. The soils use to be ploughed and the features of soil erosion are found after each thunderstorm. Rills are removed by ploughing. Thirty rainfall simulation experiments were carried out in summer 2011 during the summer drought period. The simulated rainfall lasted during 1 hour at a 45 mmh-1 intensity on 1 m2 plots (Cerdà and Doerr, 2010; Cerdà and Jurgensen 2011). Ten experiments were carried out on the control plots (ploughed), 10 on straw mulch covered plots, and 10 on chipped branches covered

Experimental study of the cavitation erosion in centrifugal pump impeller

International Nuclear Information System (INIS)

Rayan, M.A.

1985-01-01

Research on cavitation damage scale effects show that the damage rate is increased with size and velocity. It seems that for constant velocity there is no clear trend for the variation of erosion with cavitation number. Research on the time effects on damage rate show similarity between cavitation and impingement erosion. The cumulative weight loss versus time curve is of a ''S'' shaped type characterized by an incubation period followed by a period of increasing erosion rate, then a maximum erosion rate, and finally a period of decreasing erosion rate. The objective of this investigation is to present a prototype cavitation erosion experiment in order to clarify the time dependency of the erosive wear

Using (137)Cs measurements to estimate soil erosion rates in the Pčinja and South Morava River Basins, southeastern Serbia.

Science.gov (United States)

Petrović, Jelena; Dragović, Snežana; Dragović, Ranko; Đorđević, Milan; Đokić, Mrđan; Zlatković, Bojan; Walling, Desmond

2016-07-01

The need for reliable assessments of soil erosion rates in Serbia has directed attention to the potential for using (137)Cs measurements to derive estimates of soil redistribution rates. Since, to date, this approach has not been applied in southeastern Serbia, a reconnaissance study was undertaken to confirm its viability. The need to take account of the occurrence of substantial Chernobyl fallout was seen as a potential problem. Samples for (137)Cs measurement were collected from a zone of uncultivated soils in the watersheds of Pčinja and South Morava Rivers, an area with known high soil erosion rates. Two theoretical conversion models, the profile distribution (PD) model and diffusion and migration (D&M) model were used to derive estimates of soil erosion and deposition rates from the (137)Cs measurements. The estimates of soil redistribution rates derived by using the PD and D&M models were found to differ substantially and this difference was ascribed to the assumptions of the simpler PD model that cause it to overestimate rates of soil loss. The results provided by the D&M model were judged to more reliable. Copyright © 2016 Elsevier Ltd. All rights reserved.

Modeling soil erosion in a watershed

OpenAIRE

Lanuza, R.

1999-01-01

Most erosion models have been developed based on a plot scale and have limited application to a watershed due to the differences in aerial scale. In order to address this limitation, a GIS-assisted methodology for modeling soil erosion was developed using PCRaster to predict the rate of soil erosion at watershed level; identify the location of erosion prone areas; and analyze the impact of landuse changes on soil erosion. The general methodology of desktop modeling or soil erosion at watershe...

Spatial bedrock erosion distribution in a natural gorge

Science.gov (United States)

Beer, A. R.; Turowski, J. M.; Kirchner, J. W.

2015-12-01

Quantitative analysis of morphological evolution both in terrestrial and planetary landscapes is of increasing interest in the geosciences. In mountainous regions, bedrock channel formation as a consequence of the interaction of uplift and erosion processes is fundamental for the entire surface evolution. Hence, the accurate description of bedrock channel development is important for landscape modelling. To verify existing concepts developed in the lab and to analyse how in situ channel erosion rates depend on the interrelations of discharge, sediment transport and topography, there is a need of highly resolved topographic field data. We analyse bedrock erosion over two years in a bedrock gorge downstream of the Gorner glacier above the town of Zermatt, Switzerland. At the study site, the Gornera stream cuts through a roche moutonnée in serpentine rock of 25m length, 5m width and 8m depth. We surveyed bedrock erosion rates using repeat terrestrial laser scanning (TLS) with an average point spacing of 5mm. Bedrock erosion rates in direction of the individual surface normals were studied directly on the scanned point clouds applying the M3C2 algorithm (Lague et al., 2013, ISPRS). The surveyed erosion patterns were compared to a simple stream erosivity visualisation obtained from painted bedrock sections at the study location. Spatially distributed erosion rates on bedrock surfaces based on millions of scan points allow deduction of millimeter-scale mean annual values of lateral erosion, incision and downstream erosion on protruding streambed surfaces. The erosion rate on a specific surface point is shown to depend on the position of this surface point in the channel's cross section, its height above the streambed and its spatial orientation to the streamflow. Abrasion by impacting bedload was likely the spatially dominant erosion process, as confirmed by the observed patterns along the painted bedrock sections. However, a single plucking event accounted for the half

In-situ buildup of cosmogenic isotopes at the earth`s surface: measurement of erosion rates and exposure times

Energy Technology Data Exchange (ETDEWEB)

Fifield, L K; Allan, G L; Stone, J O.H.; Evans, J M; Cresswell, R G; Ophel, T R [Australian National Univ., Canberra, ACT (Australia)

1994-12-31

Cosmic rays produce a number of nuclides in rocks that can be used to determine the geomorphic history of surfaces. The most useful are the radioactive isotopes {sup 10}Be (t{sub 1/2} = 1.5Ma), {sup 26}Al (0.7Ma) and {sup 36}Cl (0.3Ma). Within the top 2m of the surface, these are produced principally by fast neutrons. At greater depths, production is dominated by the capture of negative muons. Measurements of a single nuclide produced in situ can be used to determine total exposure times or erosion rates. The use of multiple nuclides with different half-lives makes it possible to determine more complex histories, such as exposures interrupted by periods of burial. At the ANU, all three of the isotopes above are being used to study a variety of problems in geomorphology and paleoclimatology, although to date, most of the work has concentrated on {sup 36}Cl. The accumulation of cosmogenic {sup 36}Cl in calcite (CaCO{sub 3}) provides a means of measuring erosion rates on limestone surfaces. Sensitivity is achieved over a wide range of erosion rates due to the high production rate of {sup 36}Cl in calcite (typically greater than 30 atoms/g/yr) and a detection limit of ca. 5000 atoms/g attainable with the ANU AMS system. The method is simplified by the predominance of Ca reactions (principally spallation) over other sources of {sup 36}Cl in calcite, and the ease of sample preparation. This presentation discuss the results of measurements of {sup 36}Cl in calcite from limestone samples from Australia and Papua New Guinea. Erosion rates derived from these measurements range from 3 microns per year (Australia) to over 200 microns per year in the New Guinea highlands. 3 refs.

In-situ buildup of cosmogenic isotopes at the earth`s surface: measurement of erosion rates and exposure times

Energy Technology Data Exchange (ETDEWEB)

Fifield, L.K.; Allan, G.L.; Stone, J.O.H.; Evans, J.M.; Cresswell, R.G.; Ophel, T.R. [Australian National Univ., Canberra, ACT (Australia)

1993-12-31

Cosmic rays produce a number of nuclides in rocks that can be used to determine the geomorphic history of surfaces. The most useful are the radioactive isotopes {sup 10}Be (t{sub 1/2} = 1.5Ma), {sup 26}Al (0.7Ma) and {sup 36}Cl (0.3Ma). Within the top 2m of the surface, these are produced principally by fast neutrons. At greater depths, production is dominated by the capture of negative muons. Measurements of a single nuclide produced in situ can be used to determine total exposure times or erosion rates. The use of multiple nuclides with different half-lives makes it possible to determine more complex histories, such as exposures interrupted by periods of burial. At the ANU, all three of the isotopes above are being used to study a variety of problems in geomorphology and paleoclimatology, although to date, most of the work has concentrated on {sup 36}Cl. The accumulation of cosmogenic {sup 36}Cl in calcite (CaCO{sub 3}) provides a means of measuring erosion rates on limestone surfaces. Sensitivity is achieved over a wide range of erosion rates due to the high production rate of {sup 36}Cl in calcite (typically greater than 30 atoms/g/yr) and a detection limit of ca. 5000 atoms/g attainable with the ANU AMS system. The method is simplified by the predominance of Ca reactions (principally spallation) over other sources of {sup 36}Cl in calcite, and the ease of sample preparation. This presentation discuss the results of measurements of {sup 36}Cl in calcite from limestone samples from Australia and Papua New Guinea. Erosion rates derived from these measurements range from 3 microns per year (Australia) to over 200 microns per year in the New Guinea highlands. 3 refs.

Soil movements and surface erosion rates on rocky slopes in the mountain areas of the karst region of Southwest China

Science.gov (United States)

Zhang, X. B.; Bai, X. Y.; Long, Y.

2012-04-01

The karst region of Southwest China with an area of 54 × 104 km2 is one of the largest karst areas in the world and experiences subtropical climate. Hill-depressions are common landforms in the mountain areas of this region. Downslope soil movement on the ground by surface water erosion and soil sinking into underground holes by creeping or pipe erosion are mayor types of soil movements on rocky carbonate slopes. The 137Cs technique was used to date the sediment deposits in six karst depressions, to estimate average surface erosion rates on slopes from their catchments. The estimates of soil loss rates obtained from this study evidenced considerable variability. A value of 1.0 t km-2 year-1 was obtained for a catchment under original dense karst forest, but the erosion rates ranged between 19.3 t km-2 year-1 and 48.7 t km-2 year-1 in four catchments under secondary forest or grasses, where the original forest cover had been removed in the Ming and Qing dynasties, several hundred years ago. The highest rate of 1643 t km-2 year-1 was obtained for a catchment underlain by clayey carbonate rocks, where the soil cover was thicker and more extensive than in the other catchments and extensive land reclamation for cultivation had occurred during the period 1979-1981, immediately after the Cultural Revolution.

Fundamental study on cavitation erosion in liquid metal. Effect of liquid parameter on cavitation erosion in liquid metals (Joint research)

International Nuclear Information System (INIS)

Hattori, Shuji; Kurachi, Hiroaki; Inoue, Fumitaka; Watashi, Katsumi; Tsukimori, Kazuyuki; Yada, Hiroki; Hashimoto, Takashi

2009-02-01

Cavitation erosion, which possibly occurs on the surfaces of fluid machineries and components contacting flowing liquid and causes sponge-like damage on the material surface, is important problem, since it may become the cause of performance deduction, life shortening, noise, vibration of mechanical components and moreover failure of machine. Research on cavitation erosion in liquid metal is very important to confirm the safety of fast breeder reactor using sodium coolant and to avoid serious damage of the target vessel of spallation neutron source containing liquid-mercury. But the research on cavitation erosion in liquid metal has been hardly performed because of its specially in comparison with that in water. In this study, a cavitation erosion test apparatus was developed to carry out the erosion tests in low-temperature liquid metals. Cavitation erosion tests were carried out in liquid lead-bismuth alloy and in deionized water. We discuss the effect of liquid parameters and temperature effects on the erosion rate. We reach to the following conclusions. The erosion rate was evaluated in terms of a relative temperature which was defind as the percentage between freezing and boiling points. At 14degC relative temperature, the erosion rate is 10 times in lead-bismuth alloy, and 2 to 5 times in sodium, compared with that in deionized water. At 14degC relative temperature, the erosion rate can be evaluated in terms of the following parameter. 1 / (1/ρ L /C L +1/ρ S C S )√ρ L . Where ρ is the material density and c is the velocity of sound, L and S denote liquid and solid. In the relative temperature between 14 and 30degC, the temperature dependence on the erosion rate is due to the increase in vapor pressure. (author)

Erosion characteristics and horizontal variability for small erosion depths in the Sacramento-San Joaquin River Delta, California, USA

Science.gov (United States)

Schoellhamer, David H.; Manning, Andrew J.; Work, Paul A.

2017-01-01

Erodibility of cohesive sediment in the Sacramento-San Joaquin River Delta (Delta) was investigated with an erosion microcosm. Erosion depths in the Delta and in the microcosm were estimated to be about one floc diameter over a range of shear stresses and times comparable to half of a typical tidal cycle. Using the conventional assumption of horizontally homogeneous bed sediment, data from 27 of 34 microcosm experiments indicate that the erosion rate coefficient increased as eroded mass increased, contrary to theory. We believe that small erosion depths, erosion rate coefficient deviation from theory, and visual observation of horizontally varying biota and texture at the sediment surface indicate that erosion cannot solely be a function of depth but must also vary horizontally. We test this hypothesis by developing a simple numerical model that includes horizontal heterogeneity, use it to develop an artificial time series of suspended-sediment concentration (SSC) in an erosion microcosm, then analyze that time series assuming horizontal homogeneity. A shear vane was used to estimate that the horizontal standard deviation of critical shear stress was about 30% of the mean value at a site in the Delta. The numerical model of the erosion microcosm included a normal distribution of initial critical shear stress, a linear increase in critical shear stress with eroded mass, an exponential decrease of erosion rate coefficient with eroded mass, and a stepped increase in applied shear stress. The maximum SSC for each step increased gradually, thus confounding identification of a single well-defined critical shear stress as encountered with the empirical data. Analysis of the artificial SSC time series with the assumption of a homogeneous bed reproduced the original profile of critical shear stress, but the erosion rate coefficient increased with eroded mass, similar to the empirical data. Thus, the numerical experiment confirms the small-depth erosion hypothesis. A linear

Definition of tolerable soil erosion values

Directory of Open Access Journals (Sweden)

G. Sparovek

1997-09-01

Full Text Available Although the criteria for defining erosion tolerance are well established, the limits generally used are not consistent with natural, economical and technological conditions. Rates greater than soil formation can be accepted only until a minimum of soil depth is reached, provided that they are not associated with environmental hazard or productivity losses. A sequence of equations is presented to calculate erosion tolerance rates through time. The selection of equation parameters permits the definition of erosion tolerance rates in agreement with environmental, social and technical needs. The soil depth change that is related to irreversible soil degradation can be calculated. The definition of soil erosion tolerance according to these equations can be used as a guideline for sustainable land use planning and is compatible with expert systems.

Sediment budget for Murder Creek, Georgia, USA, from Pu239+240 - determined soil erosion rates

Science.gov (United States)

Stubblefield, A. P.; Matissoff, G.; Ketterer, M. E.; Whiting, P. J.

2005-12-01

Soil inventories of the radionuclides Cs137 and Pb210 have been used in a variety of environments as indicators for erosion and depositional processes. Development of sediment budgets for entire watersheds from radionuclide data has been somewhat constrained because limited sample numbers may not adequately characterize the wide range of geomorphic conditions and land uses found in heterogeneous environments. The measurement of Pu239+240 shows great potential for developing quantitative watershed sediment budgets. With inductively-coupled plasma mass spectrometry, hundreds of samples may be processed in dramatically shorter times than the gamma spectrometry method used for Cs137 or alpha spectrometry method used for Pb210. We collected surface soil samples from Murder Creek in the Piedmont region of Georgia, USA, to compare Pu239+240 inventories with Cs137 and Pb210 inventories for a range of land uses in a predominantly forested watershed. Excellent correlations were found for radionuclide inventories (r2 =0.88, n = 38) and high resolution (4 mm) depth profiles. The second objective was to generate a sediment budget using the full Pu239+240 dataset (n = 309). Average Pu239+240 inventories were 70.0 Bq/m2 for hardwood forest, 60.0 Bq/m2 for pine plantation, 65.1 Bq/m2 for pine forest, 66.7 Bq/m2 for row crop agriculture and 67.9 Bq/m2 for pasture. The sediment budget will be constructed by converting inventories into site-specific erosion rates. Erosion rates will be scaled up to the watershed scale using GIS coverages of land use, soil, slope, and slope position. Results will be compared with Murder Creek sediment budgets in the scientific literature generated from RUSLE erosion modeling, USGS monitoring networks and reservoir sedimentation.

Effect of water content nitrogen gross mineralization and immobilization

International Nuclear Information System (INIS)

Videla C, Ximena; Parada, Ana Maria; Nario M, Adriana; Pino N, Ines; Hood, Rebeca

2005-01-01

The decomposition of organic matter in soil, and the accompanying mineralization and immobilization of inorganic N, are key processes in the soil plant cycle. It is hypothesized that moisture regime may also play an important role on these processes. Two laboratory studies were carried out to investigate the effect of moisture regime on gross mineralization and immobilization of N, in and Ultisol soil, which was incubated at 25 o C, under two moisture regimes, field capacity (CC) (40% w/w) and 85% of field capacity (34% w/w): Using mirror image 15 N isotope dilution techniques, it was possible to determine gross nitrification and mineralization rates. The rates of gross mineralization and nitrification rate in this soil was extremely rapid and efficient, specially with 85% CC. The N transformations varied with moisture regime (author)

Ecological site-based assessments of wind and water erosion: informing accelerated soil erosion management in rangelands

Science.gov (United States)

Webb, Nicholas P.; Herrick, Jeffrey E.; Duniway, Michael C.

2014-01-01

Accelerated soil erosion occurs when anthropogenic processes modify soil, vegetation or climatic conditions causing erosion rates at a location to exceed their natural variability. Identifying where and when accelerated erosion occurs is a critical first step toward its effective management. Here we explore how erosion assessments structured in the context of ecological sites (a land classification based on soils, landscape setting and ecological potential) and their vegetation states (plant assemblages that may change due to management) can inform systems for reducing accelerated soil erosion in rangelands. We evaluated aeolian horizontal sediment flux and fluvial sediment erosion rates for five ecological sites in southern New Mexico, USA, using monitoring data and rangeland-specific wind and water erosion models. Across the ecological sites, plots in shrub-encroached and shrub-dominated vegetation states were consistently susceptible to aeolian sediment flux and fluvial sediment erosion. Both processes were found to be highly variable for grassland and grass-succulent states across the ecological sites at the plot scale (0.25 Ha). We identify vegetation thresholds that define cover levels below which rapid (exponential) increases in aeolian sediment flux and fluvial sediment erosion occur across the ecological sites and vegetation states. Aeolian sediment flux and fluvial erosion in the study area can be effectively controlled when bare ground cover is 100 cm in length is less than ~35%. Land use and management activities that alter cover levels such that they cross thresholds, and/or drive vegetation state changes, may increase the susceptibility of areas to erosion. Land use impacts that are constrained within the range of natural variability should not result in accelerated soil erosion. Evaluating land condition against the erosion thresholds identified here will enable identification of areas susceptible to accelerated soil erosion and the development of

Ecological site‐based assessments of wind and water erosion: informing accelerated soil erosion management in rangelands.

Science.gov (United States)

Webb, Nicholas P; Herrick, Jeffrey E; Duniway, Michael C

Accelerated soil erosion occurs when anthropogenic processes modify soil, vegetation, or climatic conditions causing erosion rates at a location to exceed their natural variability. Identifying where and when accelerated erosion occurs is a critical first step toward its effective management. Here we explored how erosion assessments structured in the context of ecological sites (a land classification based on soils, landscape setting, and ecological potential) and their vegetation states (plant assemblages that may change due to management) can inform systems for reducing accelerated soil erosion in rangelands. We evaluated aeolian horizontal sediment flux and fluvial sediment erosion rates for five ecological sites in southern New Mexico, USA, using monitoring data and rangeland-specific wind and water erosion models. Across the ecological sites, plots in shrub-encroached and shrub-dominated vegetation states were consistently susceptible to aeolian sediment flux and fluvial sediment erosion. Both processes were found to be highly variable for grassland and grass–succulent states across the ecological sites at the plot scale (0.25 ha). We identified vegetation thresholds that define cover levels below which rapid (exponential) increases in aeolian sediment flux and fluvial sediment erosion occur across the ecological sites and vegetation states. Aeolian sediment flux and fluvial erosion in the study area could be effectively controlled when bare ground cover was 100 cm in length was less than ∼35%. Land use and management activities that alter cover levels such that they cross thresholds, and/or drive vegetation state changes, may increase the susceptibility of areas to erosion. Land use impacts that are constrained within the range of natural variability should not result in accelerated soil erosion. Evaluating land condition against the erosion thresholds identified here will enable identification of areas susceptible to accelerated soil erosion and the

Detecting Anthropogenic Disturbance on Weathering and Erosion Processes

Science.gov (United States)

Vanacker, V.; Schoonejans, J.; Bellin, N.; Ameijeiras-Mariño, Y.; Opfergelt, S.; Christl, M.

2014-12-01

Anthropogenic disturbance of natural vegetation can profoundly alter the physical, chemical and biological processes within soils. Rapid removal of topsoil during intense farming can result in an imbalance between soil production through chemical weathering and physical erosion, with direct implications on local biogeochemical cycling. However, the feedback mechanisms between soil erosion, chemical weathering and biogeochemical cycling in response to anthropogenic forcing are not yet fully understood. In this paper, we analyze dynamic soil properties for a rapidly changing anthropogenic landscape in the Spanish Betic Cordillera; and focus on the coupling between physical erosion, soil production and soil chemical weathering. Modern erosion rates were quantified through analysis of sediment deposition volumes behind check dams, and represent catchment-average erosion rates over the last 10 to 50 years. Soil production rates are derived from in-situ produced 10Be nuclide concentrations, and represent long-term flux rates. In each catchment, soil chemical weathering intensities were calculated for two soil-regolith profiles. Although Southeast Spain is commonly reported as the European region that is most affected by land degradation, modern erosion rates are low (140 t ha-1 yr-1). About 50 % of the catchments are losing soils at a rate of less than 60 t km-2 yr-1. Our data show that modern erosion rates are roughly of the same magnitude as the long-term or cosmogenically-derived erosion rates in the Betic Cordillera. Soils developed on weathered metamorphic rocks have no well-developed profile characteristics, and are generally thin and stony. Nevertheless, soil chemical weathering intensities are high; and question the occurrence of past soil truncation.

Reduction Potato s hydric soil erosion using space technology

Science.gov (United States)

Guyot, E.; Rios, V.; Zelaya, D.; Rios, E.; Lepen, F.; Padilla, P.; Soria, F.

The potato's crop has an econ omic importance in Tucuman's agricultural PBI (Gross Product Income) because its rank is fourth(4°). Production's potato area is a breakable agro system; its geographic location is in Pedemonte's agro-ecological region so is essential to handle hydric erosion. Therefore, the aim of this work is improve crop's potato irrigation management through satellite information merge with farm's practices. The space technology consented to obtain Digital Model Soil using both unique differential and dual frequency GPS signals and total station. The irrigation practices were carried out due to irrigation management (FAO) and satellite imagine software (ENVI). Preliminary results of this experience allowed to follow the crop's growing through multitemporal study; reprogramming farm's irrigation practices intended for manage reduction hydric erosion and heighten economically its productivity for the next period

Sediment and Cavitation Erosion Studies through Dam Tunnels

Directory of Open Access Journals (Sweden)

Muhammad Abid

2016-01-01

Full Text Available This paper presents results of sediment and cavitation erosion through Tunnel 2 and Tunnel 3 of Tarbela Dam in Pakistan. Main bend and main branch of Tunnel 2 and outlet 1 and outlet 3 of Tunnel 3 are concluded to be critical for cavitation and sediment erosion. Studies are also performed for increased sediments flow rate, concluding 5 kg/sec as the critical value for sudden increase in erosion rate density. Erosion rate is concluded to be the function of sediment flow rate and head condition. Particulate mass presently observed is reasonably low, hence presently not affecting the velocity and the flow field.

Effect of mechanical properties on erosion resistance of ductile materials

Science.gov (United States)

Levin, Boris Feliksovih

Solid particle erosion (SPE) resistance of ductile Fe, Ni, and Co-based alloys as well as commercially pure Ni and Cu was studied. A model for SPE behavior of ductile materials is presented. The model incorporates the mechanical properties of the materials at the deformation conditions associated with SPE process, as well as the evolution of these properties during the erosion induced deformation. An erosion parameter was formulated based on consideration of the energy loss during erosion, and incorporates the material's hardness and toughness at high strain rates. The erosion model predicts that materials combining high hardness and toughness can exhibit good erosion resistance. To measure mechanical properties of materials, high strain rate compression tests using Hopkinson bar technique were conducted at strain rates similar to those during erosion. From these tests, failure strength and strain during erosion were estimated and used to calculate toughness of the materials. The proposed erosion parameter shows good correlation with experimentally measured erosion rates for all tested materials. To analyze subsurface deformation during erosion, microhardness and nanoindentation tests were performed on the cross-sections of the eroded materials and the size of the plastically deformed zone and the increase in materials hardness due to erosion were determined. A nanoindentation method was developed to estimate the restitution coefficient within plastically deformed regions of the eroded samples which provides a measure of the rebounding ability of a material during particle impact. An increase in hardness near the eroded surface led to an increase in restitution coefficient. Also, the stress rates imposed below the eroded surface were comparable to those measured during high strain-rate compression tests (10sp3-10sp4 ssp{-1}). A new parameter, "area under the microhardness curve" was developed that represents the ability of a material to absorb impact energy. By

A study of erosion rates on salt diapir surfaces in the Zagros Mountains, SE Iran

Czech Academy of Sciences Publication Activity Database

Bruthans, J.; Asadi, N.; Filippi, Michal; Wilhelm, Z.; Zare, M.

2008-01-01

Roč. 53, č. 5 (2008), s. 1079-1089 ISSN 0943-0105 R&D Projects: GA AV ČR(CZ) KJB301110501 Institutional research plan: CEZ:AV0Z30130516 Keywords : salt diapir * weathering residuum * erosion rate Subject RIV: DB - Geology ; Mineralogy Impact factor: 1.026, year: 2008

Evaluation of free i-applications for tertiary level gross anatomy education

Directory of Open Access Journals (Sweden)

Matthew F. Pollard

2012-04-01

Full Text Available BackgroundThe use of electronic resources in education, including i-applications used on portable handheld devices, is increasing. Apple® handheld devices are popular, with free applications the most prevalent download form. Many gross anatomy i-applications are available, however no information on the quality of free anatomy products is available. Rating such products could therefore guide product recommendations.AimTo evaluate the quality and range of free iPod® applications that are applicable for tertiary level gross anatomy education.MethodsA search of the iTunes® Application Store with keywords anatomy, free, medical, functional, clinical, gross, and human was performed, with inclusion based on free applications containing human gross anatomy usable for tertiary education purposes. Application specification was noted; each was trialled independently and rated for usability, specification, academic level, and quality (image and programme.ResultsSixty-three applications were identified and eleven met inclusion criteria. Two provided gross anatomy of the entire body, nine examined specific regions or systems. Five were judged introductory in academic level, five intermediate, and one advanced. One application was rated low quality, and four excellent. None were considered difficult to use (six easy, five medium. Application size ranged between 1.2MB and 229MB (mean 27MB.ConclusionsThere are few free i-applications for learning gross anatomy and most concentrate on individual body systems, with the academic level and usability of all products well rated. Results suggest some free I-applications could be suitable adjuncts for gross anatomy education at both an undergraduate and graduate level.

Developments of regional gross domestic product and the unemployment rate in Romania during 2000 - 2012

Directory of Open Access Journals (Sweden)

Schonauer (Sacală Corina

2015-12-01

Full Text Available Economic development of territorial units can be characterized by measuring the ability of producing goods and services and by measuring labor force in the area. The capacity of producing goods and services is measured by calculating the gross domestic product indicator. This article presents a comparative analysis of the evolution of regional GDP and the ILO unemployment rate at the level of the eight regions in Romania for a period of 13 years. The presented data come from the National Institute of Statistics of Romania.

Using 7Be to document soil erosion on the weed plots

International Nuclear Information System (INIS)

Zhang Bo; Zhang Fengbao; Yang Mingyi

2013-01-01

Be tracing technology was applied to document soil erosion on the bare plot and weed plot, and compae soil erosion rate with the calculated rate. Results indicated that vegetation cover had obvious effect on the estimate of soil erosion rate on the weed plot using 7 Be measurement. Therefore, a factor of vegetation had been introduced into the Walling's model of converting 7 Be activity to soil erosion rate for estimating soil erosion rate on the weed slope surface. It was found that the soil erosion rates calculated by modified model were well close to the measured values on the weed plot, which illustrated that the modified model could be well used to estimate the rates of soil loss on the weed slope surface. These findings provide effective means for further study on the relationship between vegetation cover and soil erosion. (authors)

Effects of Bank Vegetation and Incision on Erosion Rates in an Urban Stream

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Emily Arnold

2018-04-01

Full Text Available Changing land-use associated with urbanization has resulted in shifts in riparian assemblages, stream hydraulics, and sediment dynamics leading to the degradation of waterways. To combat degradation, restoration and management of riparian zones is becoming increasingly common. However, the relationship between flora, especially the influence of invasive species, on sediment dynamics is poorly understood. Bank erosion and turbidity were monitored in the Tookany Creek and its tributary Mill Run in the greater Philadelphia, PA region. To evaluate the influence of the invasive species Reynoutria japonica (Japanese knotweed on erosion, reaches were chosen based on their riparian vegetation and degree of incision. Bank pins and turbidity loggers were used to estimate sediment erosion. Erosion calculations based on bank pins suggest greater erosion in reaches dominated by knotweed than those dominated by trees. For a 9.5-month monitoring period, there was 29 cm more erosion on banks that were also incised, and 9 cm more erosion in banks with little incision. Turbidity responses to storm events were also higher (77 vs. 54 NTU (nephelometric turbidity unit in reaches with knotweed, although this increase was found when the reach dominated by knotweed was also incised. Thus, this study linked knotweed to increased erosion using multiple methods.

Dynamics of soil organic carbon and microbial biomass carbon in relation to water erosion and tillage erosion.

Science.gov (United States)

Xiaojun, Nie; Jianhui, Zhang; Zhengan, Su

2013-01-01

Dynamics of soil organic carbon (SOC) are associated with soil erosion, yet there is a shortage of research concerning the relationship between soil erosion, SOC, and especially microbial biomass carbon (MBC). In this paper, we selected two typical slope landscapes including gentle and steep slopes from the Sichuan Basin, China, and used the (137)Cs technique to determine the effects of water erosion and tillage erosion on the dynamics of SOC and MBC. Soil samples for the determination of (137)Cs, SOC, MBC and soil particle-size fractions were collected on two types of contrasting hillslopes. (137)Cs data revealed that soil loss occurred at upper slope positions of the two landscapes and soil accumulation at the lower slope positions. Soil erosion rates as well as distribution patterns of the erosion is the major process of soil redistribution in the gentle slope landscape, while tillage erosion acts as the dominant process of soil redistribution in the steep slope landscape. In gentle slope landscapes, both SOC and MBC contents increased downslope and these distribution patterns were closely linked to soil redistribution rates. In steep slope landscapes, only SOC contents increased downslope, dependent on soil redistribution. It is noticeable that MBC/SOC ratios were significantly lower in gentle slope landscapes than in steep slope landscapes, implying that water erosion has a negative effect on the microbial biomass compared with tillage erosion. It is suggested that MBC dynamics are closely associated with soil redistribution by water erosion but independent of that by tillage erosion, while SOC dynamics are influenced by soil redistribution by both water erosion and tillage erosion.

Decreasing soil erosion rates with evolving land-use techniques in a central European catchment

Science.gov (United States)

Larsen, Annegret; Heckmann, Tobias; Hans-Rudolf, Bork; Alexander, Fuelling

2015-04-01

Agricultural societies around the world have caused accelerated soil erosion. Soil erosion and a decrease in soil fertility may also have caused the abandonment of entire landscapes and the collapse of civilizations. In central Europe, Medieval land-use is thought to have lead to the largest loss of top soil in history, which in turn lead to a malnutrition of the population and abandonment of agricultural land. However, this might be only part of the picture, as people are also able to adapt to changing environmental conditions, including the type of land-use they adopt. Within a catchment in the central European mountain belt, we were able to distinguish the evolution between three main types of land-use techniques between ~ 900 AD and 1950 AD: horticulture, agriculture and shifting cultivation. We were able to relate these techniques with different soil erosion rates, which differ by an order of magnitude, ranging from 0.83 ± 0.09 mm/yr to 1.62 ± 0.17 mm/yr. Using high-resolution surface data and chrono-stratigraphical methods in combination with soil charcoal analysis, we were able to reconstruct past land-use techniques on a local scale. This illustrates that less erosive and more sustainable techniques were developed through time, and hypothesize that people were able to adapt to the less favorable environmental conditions by changing the cultivation techniques. Although cultural adaptation to changing environmental conditions has been extensively discussed, this study is able to quantitatively demonstrate improved soil management with evolving land-use in central Europe.

Tectonic controls of Holocene erosion in a glaciated orogen

OpenAIRE

Adams, Byron A.; Ehlers, Todd A.

2018-01-01

Recent work has highlighted a strong, worldwide, glacial impact of orogen erosion rates over the last 2 Ma. While it may be assumed that glaciers increased erosion rates when active, the degree to which past glaciations influence Holocene erosion rates through the adjustment of topography is not known. In this study, we investigate the influence of long-term tectonic and post-glacial topographic controls on erosion in a glaciated orogen, the Olympic Mountains, USA. We present 14 new 10Be and ...

Towards quantifying long-term erosion rates in the Campine Basin, NE Belgium

Science.gov (United States)

Beerten, Koen; Vanacker, Veerle

2016-04-01

The Campine Basin, NE Belgium, is situated between the uplifting Ardennes Massif and rapidly subsiding Roer Valley Graben. It contains a thick series of marine, estuarine and continental Neogene and Quaternary sediments, locally more than 300 m. As a result of relief inversion during the Quaternary, the Campine Plateau is nowadays a distinct morphological feature in this basin. Its surface elevation dips from 100 m in the south to 30 m in the north over a distance of about 60 km, which is the result of differential uplift. The Campine Plateau is covered by Early and Middle Pleistocene erosion-resistant fluvial sediments from the Rhine and Meuse and can thus be regarded as a fluvial terrace. The age of deposition and time of abandonment of the terrace have not yet been resolved by direct numerical dating. In this study, we apply the cosmogenic radionuclide (CRN) profiling technique that, in ideal circumstances, allows one to constrain the exposure age, burial age and amount of post-depositional erosion of the landform. Samples were taken from a 3.5 m deep cross-section in coarse river sands that were deposited by the river Rhine, and now situated at an altitude of about 50 m (a.s.l.). Nine of them were prepared for CRN measurements according to state-of-the-art techniques. The in-situ 10Be concentration of the samples was determined using accelerator mass spectrometry (ETH, Zurich). The in-situ 10Be concentrations are 1.5x10e5 atoms/g for the uppermost sample (at 0.3 m depth) and 0.9x10e5 at/g for the lowermost sample (at 3.1 m depth), yielding an estimated 0.6x10e5 at/g of radionuclide accumulation following sediment deposition. Using forward modelling, we solved for the exposure duration and erosion rate that best fit the measured in-situ 10Be depth profile data, nuclide inheritance and their associated analytical uncertainties. Model optimisation is here based on the sum of chi-squared between the measured and modelled 10Be concentrations. When taking previous

Erosion reasons and rate on accumulative Polish dune coast caused by the January 2012 storm surge

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Tomasz A. Łabuz

2014-03-01

Full Text Available The Polish coast is a non-tidal area; its shores are affected mainly by autumn-winter storm surges. Those of 6 and 14 January 2012 are representative of the forces driving the erosion of normally accumulative sections of coastal dunes, monitored by the author since 1997. The sea level maximum during these two storm surges reached 1.2 to 1.5 m amsl along the Polish coast. Land forms up to 3 m amsl were inundated. Beaches and low parts of the coast up to this height were rebuilt by sea waves attacking the coast for almost 12 days. Quantitative analyses of the morphological dynamics of the coastal dunes are presented for 57 profiles located along the coast. Only those accumulative sections of the Polish coast are analysed where sand accumulation did occur and led to new foredune development. The mean rate of dune erosion was 2.5 m3 per square metre with an average toe retreat of 1.4 m. Erosion understood as dune retreat was greater when a beach was lower (correlation coefficient 0.8. Dune erosion did not occur on coasts with beaches higher than 3.2 m or on lower ones covered by embryo dunes.

First Report of Coccidiosis and Gizzard Erosion in a Zebra Finch (Taeniopygia guttata of Iran

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Moini, M.

2012-06-01

Full Text Available Coccidiosis and gizzard erosion are rare conditions in cage bird. A male zebra finch was presented with a history of watery diarrhea, anorexia, ruffled feathers, weight loss, and lethargy and died finally. Gross necropsy revealed small areas of erosions and hemorrhages on the gizzard wall. The intestine was oedematous. The spleen appeared pale and small. The testes were asymmetric.Histologically, necrosis of mucosal layer with infiltration of inflammatory cells observed in cecum. Eimeria stages were detected in the enterocytes. In Gizzard, hemorrhage and ulceration of mucosal layer with infiltration of polymorphonuclear cells in to the underlying mucosa were seen. In hepatic tissue, mild focal necrosis with mononuclear cells infiltration was seen. The disease was diagnosed as coccidiosis and gizzard erosion.

The use of 137Cs to establish longer-term soil erosion rates on footpaths in the UK.

Science.gov (United States)

Rodway-Dyer, S J; Walling, D E

2010-10-01

There is increasing awareness of the damage caused to valuable and often unique sensitive habitats by people pressure as degradation causes a loss of plant species, disturbance to wildlife, on-site and off-site impacts of soil movement and loss, and visual destruction of pristine environments. This research developed a new perspective on the problem of recreational induced environmental degradation by assessing the physical aspects of soil erosion using the fallout radionuclide caesium-137 ((137)Cs). Temporal sampling problems have not successfully been overcome by traditional research methods monitoring footpath erosion and, to date, the (137)Cs technique has not been used to estimate longer-term soil erosion in regard to sensitive recreational habitats. The research was based on-sites within Dartmoor National Park (DNP) and the South West Coast Path (SWCP) in south-west England. (137)Cs inventories were reduced on the paths relative to the reference inventory (control), indicating loss of soil from the path areas. The Profile Distribution Model estimated longer-term erosion rates (ca. 40 years) based on the (137)Cs data and showed that the combined mean soil loss for all the sites on 'paths' was 1.41 kg m(-2) yr(-1) whereas the combined 'off path' soil loss was 0.79 kg m(-2) yr(-1), where natural (non-recreational) soil redistribution processes occur. Recreational pressure was shown to increase erosion in the long-term, as greater soil erosion occurred on the paths, especially where there was higher visitor pressure. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

Rate and cost of soil erosion in Monkayo, Compostela Valley Province Philippines

Directory of Open Access Journals (Sweden)

Sunshine G. Paulin

2016-01-01

Full Text Available Soil erosion is a major agricultural and environmental problem in the Philippines that is primarily caused by rainfall under upland, subsistence rainfed farming. The study sought to compare the degree of erosion as influenced by different upland tillage systems using soil erosion plots and MUSLE model, and estimate the cost of soil erosion in Monkayo, Compostela Valley. The erosion plots were laid on a 31.45 percent slope with a seasonal rainfall intensity of 2,314 mm. Corn (Zea mays L. planted through conventional tillage generated a mean soil loss of 2.64 t/ha/cropping, which is higher than the reduced tillage with a mean of 1.20 t/ha/cropping. The weighted on-site soil loss was 12 percent lower than the obtained soil erosion using the modified Universal Soil Loss Equation that is 2.97 t/ha. The study developed equations to estimate soil loss (t/ha per seasonal rainfall on three tillage systems using linear regression analysis which are: (1 E= -0.0031+0.0003R, (2 E= -0.0406+0.0011R, and (3 E=0.2249+0.0034R in corn grown on undisturbed land with natural vegetation, corn grown on bare soil through dibble method and corn planted through conventional planting system, respectively. On-site cost of erosion ranged from Php 1,473.42/ha/cropping to Php 1,938.81/ha/cropping. The amount of soil eroded can be attributed to the higher erositivity of rains, higher erodibility of the soil surface, and the poor soil cover.

Pressure and velocity dependence of flow-type cavitation erosion

CSIR Research Space (South Africa)

Auret, JG

1993-12-01

Full Text Available Previous results on the influence of water pressure and velocity on flow-type cavitations erosion, i.e. an increase in erosion rate with increasing velocity and peaking of erosion rate as a function of pressure, were confirmed by measurements with a...

Review of denudation processes and quantification of weathering and erosion rates at a 0.1 to 1 Ma time scale

Energy Technology Data Exchange (ETDEWEB)

Olvmo, Mats (Univ. of Goeteborg, Goeteborg (Sweden). Dept. of Earth Sciences)

2010-06-15

The Forsmark and Laxemar areas are quite similar from a geomorphological point of view. Both sites are situated within intact parts of the Sub-Cambrian Peneplain with extremely low relief. The peneplain is considered to be intact at both sites, i.e. the present relief is quite close to the original surface of this old denudation surface. The total amount of glacial erosion up to present is estimated to be relatively low at both sites (less than 10 m on average), but may have been quite important for stripping of old regolith, especially along fracture zones. This is most obvious in the vicinity of the Forsmark site where the dissected coastline 15 km south of the site is interpreted as a result of glacial erosion along old fracture zones. Therefore, from a strict glacial erosion perspective the Laxemar site is somewhat better than Forsmark. However, given the presented long-term denudation up to present, the expected amount of glacial erosion during a future glacial cycle, if similar to the last glacial cycle, is probably very limited for both sites, in the order of 2-5 m. Excluding glacial erosion, the long-term denudation rates of the two sites is fairly low as a consequence of the very low relief and the proximity to base level. The figures estimated for the long term denudation rates are in agreement with reports of denudation rates in shield areas and lie within the range 0 to 10 m/Ma for both sites. A scenario with a five-fold increase of relief that could be the effect of tectonic uplift, in a time perspective considerably longer than the coming 100,000 years, does not significantly change the picture. Even if the local relief is raised to above 100 m at both sites the estimated non-glacial denudation is very low. However, it should be noted that the effect of a relief change on the glacial system is not included in the calculations. Again, such a change on the pattern of glacial erosion would be more pronounced in the Forsmark area, since the coastline is

Review of denudation processes and quantification of weathering and erosion rates at a 0.1 to 1 Ma time scale

International Nuclear Information System (INIS)

Olvmo, Mats

2010-06-01

The Forsmark and Laxemar areas are quite similar from a geomorphological point of view. Both sites are situated within intact parts of the Sub-Cambrian Peneplain with extremely low relief. The peneplain is considered to be intact at both sites, i.e. the present relief is quite close to the original surface of this old denudation surface. The total amount of glacial erosion up to present is estimated to be relatively low at both sites (less than 10 m on average), but may have been quite important for stripping of old regolith, especially along fracture zones. This is most obvious in the vicinity of the Forsmark site where the dissected coastline 15 km south of the site is interpreted as a result of glacial erosion along old fracture zones. Therefore, from a strict glacial erosion perspective the Laxemar site is somewhat better than Forsmark. However, given the presented long-term denudation up to present, the expected amount of glacial erosion during a future glacial cycle, if similar to the last glacial cycle, is probably very limited for both sites, in the order of 2-5 m. Excluding glacial erosion, the long-term denudation rates of the two sites is fairly low as a consequence of the very low relief and the proximity to base level. The figures estimated for the long term denudation rates are in agreement with reports of denudation rates in shield areas and lie within the range 0 to 10 m/Ma for both sites. A scenario with a five-fold increase of relief that could be the effect of tectonic uplift, in a time perspective considerably longer than the coming 100,000 years, does not significantly change the picture. Even if the local relief is raised to above 100 m at both sites the estimated non-glacial denudation is very low. However, it should be noted that the effect of a relief change on the glacial system is not included in the calculations. Again, such a change on the pattern of glacial erosion would be more pronounced in the Forsmark area, since the coastline is

Saliva composition in three selected groups with normal stimulated salivary flow rates, but yet major differences in caries experience and dental erosion.

Science.gov (United States)

Bardow, Allan; Lykkeaa, Joan; Qvist, Vibeke; Ekstrand, Kim; Twetman, Svante; Fiehn, Niels-Erik

2014-08-01

It was hypothesized that, by comparing matched subjects with major differences in these dental diseases, but yet normal saliva flow rates, it would be possible to obtain data on the effect of saliva composition on dental disease isolated from the effect of the flow rate. Thus, the aim of the study was to compare the major physicochemical characteristics of stimulated whole saliva in three groups of 85 subjects, each with normal saliva flow rates and at least 24 remaining teeth. A group with very little dental disease (healthy), a group with dental erosion (erosion) and a group with very high caries experience (caries) were chosen. Furthermore, the aim was to determine whether differences among groups could also be found on an individual level. Although it was not possible to retrieve three groups whose members were completely identical, the present study points in the direction that, on a group level, subjects with very little dental disease seemed to have a more favorable physicochemical saliva composition with respect to higher calcium, phosphate, bicarbonate, pH, degree of saturation with respect to hydroxyapatite and a lower critical pH (p dental erosion (p dental caries and erosion in single individuals.

PENGKLASTERAN EROSI DI SUB DAS NGRANCAH KULONROGO (Soil Erosion Rates Clustering of Ngrancah Sub Watershed, Kulon Progo

Directory of Open Access Journals (Sweden)

Ambar Kusumandari

2012-03-01

Full Text Available ABSTRAK Penelitian ini dilakukan di Sub DAS Ngrancah yang merupakan daerah tangkapan air Waduk Sermo. Luas wilayah penelitian ini sekitar 2.200 ha. Mayoritas lahan di Sub DAS Ngrancah tergolong kritis yang ditunjukkan oleh tingginya tingkat erosi. Dengan demikian, wilayah ini sangat mendesak untuk dapat dikelola dengan benar agar degradasi lahan dapat dihambat. Untuk memprediksi erosi, diterapkan Model USLE, dengan rumus: A = RKLSCP. Wilayah studi dapat dipilahkan menjadi 77 unit lahan. Sampel tanah diambil dari seluruh unit lahan, demikian pula pengamatan lereng, vegetasi, dan penerapan konservasi tanah. Untuk menganalisis data digunakan analisis kluster. Hasil penelitian menunjukkan bahwa tingkat erosi bervariasi dari yang paling rendah sebesar 2,54 ton/ha/th sampai dengan yang tertinggi sebesar 489,30 ton/ha/th. Sekitar 68% wilayah studi termasuk dalam kelas erosi sedang dan sekitar 15% wilayah studi termasuk dalam kelas erosi tinggi. Pengklasteran unit lahan secara statistik menunjukkan bahwa pada jarak klaster terpendek terbentuk 8 klaster tingkat erosi. Uji diskriminan menunjukkan bahwa faktor K (erodibilitas dan P (praktek konservasi tanah dan air merupakan faktor yang paling dominan untuk terbentuknya klaster-klaster tersebut. Hasil penelitian ini diharapkan bermanfaat dalam merancang teknik konservasi tanah dan air untuk menangani erosi di Sub DAS Ngrancah. ABSTRACT The research was carried out at Ngrancah Sub Watershed which is located at the upper area of Sermo Dam and covers an area of almost 2.200 hectares.  The area is mostly critical showed by the high rates of erosion, so, it is  urgently required to manage properly in order to combat  land degradation. In this research, to study the erosion rates of the area, the USLE method was used, i.e. A = RxKxLSxCxP. The area was devided into 77 land units and the soil samples were taken from each land units as well as the observation of slopes, vegetation and soil conservation practices

Reduction of potatos due to hydric soil erosion using space technology

Science.gov (United States)

Guyot, E. C.; Ríos, V. H.; Zelaya, D. K.; Soria, F.; Ríos, E.; Padilla, P.

The potato's crop is in the fourth ranking of economic importance in the agricultural Gross Income of Tucuman. The geographical location of its production area makes essential the handling of the hydric soil erosion problems. The purpose of this work is to improve potato crop irrigation management using space information combined with farm practice. The field measurements were carried out using Wide Area Differential Global Position Systems FUGRO OMNISTAR, total station, and double frequency Global Position Systems. The crop irrigation was pursued through scheduling irrigation's software whose input comes from satellites of the Matutinal Constellation (LandSat 7, SACC and TERRA). The preliminary results allowed reprograming the irrigation practices for the new crop's campaign in order to decrease hydric soil erosion.

Characterizing Low-Z erosion and deposition in the DIII-D divertor using aluminum

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C.P. Chrobak

2017-08-01

Full Text Available We present measurements and modeling of aluminum erosion and redeposition experiments in separate helium and deuterium low power, low density L-mode plasmas at the outer divertor strike point of DIII-D to provide a low-Z material benchmark dataset for tokamak erosion-deposition modeling codes. Coatings of Al ∼100nm thick were applied to ideal (smooth and realistic (rough surfaces and exposed to repeat plasma discharges using the DiMES probe. Redeposition in all cases was primarily in the downstream toroidal field direction, evident from both in-situ spectroscopic and post-mortem non-spectroscopic measurements. The gross Al erosion yield was estimated from film thickness change measurements of small area samples, and was found to be ∼40–70% of the expected erosion yield based on theoretical physical sputtering yields after including sputtering by a 1–3% carbon impurity. The multi-step redeposition and re-erosion process, and hence the measured net erosion yield and material migration patterns, were found to be influenced by the surface roughness and/or porosity. A time-dependent model of material migration accounting for deposit accumulation in hidden areas was developed to reproduce the measurements in these experiments and determine a redeposition probability distribution function for sputtered atoms.

[Calculation of soil water erosion modulus based on RUSLE and its assessment under support of artificial neural network].

Science.gov (United States)

Li, Yuhuan; Wang, Jing; Zhang, Jixian

2006-06-01

With Hengshan County of Shanxi Province in the North Loess Plateau as an example, and by using ETM + and remote sensing data and RUSLE module, this paper quantitatively derived the soil and water loss in loess hilly region based on "3S" technology, and assessed the derivation results under the support of artificial neural network. The results showed that the annual average erosion modulus of Hengshan County was 103.23 t x hm(-2), and the gross erosion loss per year was 4. 38 x 10(7) t. The erosion was increased from northwest to southeast, and varied significantly with topographic position. A slight erosion or no erosion happened in walled basin, flat-headed mountain ridges and sandy area, which always suffered from dropping erosion, while strip erosion often happened on the upslope of mountain ridge and mountaintop flat. Moderate rill erosion always occurred on the middle and down slope of mountain ridge and mountaintop flat, and weighty rushing erosion occurred on the steep ravine and brink. The RUSLE model and artificial neural network technique were feasible and could be propagandized for drainage areas control and preserved practice.

Controls on gross fluxes of nitrous oxide and methane from an active agricultural ecosystem

Science.gov (United States)

Yang, W. H.; Silver, W. L.

2013-12-01

Agricultural soils can be a significant source of greenhouse gas emissions. Most research on the dynamics of these gases measure net fluxes across the soil-atmosphere interface. This approach limits our ability to determine driving variables because production and consumption processes occur simultaneously, and may be controlled by different factors. We used the trace gas stable isotope pool dilution technique to simultaneously measure field rates of gross production and consumption of N2O and CH4 during the growing season in a corn field located in the Sacramento-San Joaquin Delta, California. We also measured net nitrogen (N) mineralization and nitrification rates, soil temperature, soil moisture, and soil carbon dioxide (CO2) emissions to explore their role as drivers of greenhouse gas fluxes. Across five sampling dates spanning from seeding to senescence, net N2O fluxes ranged from 0 - 4.5 mg N m-2 d-1 and averaged 1.6 × 0.2 mg N m-2 d-1 (n = 112). Gross N2O production ranged from 0.09 - 6.6 mg N m-2 d-1 and gross N2O reduction rates ranged from 0.00 - 0.95 mg N m-2 d-1. The N2O yield averaged 0.68 × 0.02 (n = 40). At peak growth (days after seeding 59 and 94), 89 % of the variability in gross N2O production rates was predicted by the combination of soil moisture, soil temperature, net N mineralization, and CO2 emissions (n = 15, p seeding 11, 24, and 171), gross N2O production was most strongly correlated with soil temperature (R2 = 0.20, n = 24, p = 0.03), and gross N2O reduction rates were best predicted by CO2 emissions (R2 = 0.80, n =24, p production in 36 out of 37 measurements. Gross CH4 production reached as high as 5.4 mg C m-2 d-1 with rates trending higher throughout the growing season. Gross CH4 production rates were marginally significantly higher in rows than in inter-rows (p = 0.10). Gross CH4 oxidation did not differ significantly among sampling dates (Figure 2b), averaging 1.1 × 0.2 mg C m-2 d-1 across all measurements (n = 37). However

[US Geological Survey research in radioactive waste disposal, fiscal year 1980:] Tectonics, seismicity, volcanism, and erosion rates in the southern Great Basin

International Nuclear Information System (INIS)

Carr, W.J.; Rogers, A.M.

1982-01-01

The objective is to assess the potential for faulting, damaging earthquakes, recurrence of volcanism, and local acceleration of erosion in parts of the southern Great Basin. The following approaches are being used: (1) investigating the rate, intensity, and distribution of faulting during approximately the last 25 m.y., with emphasis on the last 10 m.y.; (2) monitoring and interpreting present seismicity; (3) studying the history of volcanism; and (4) evaluating past rates of erosion and deposition. Progress is reported

The determination of the national background radioactivity of gross alpha and gross beta in water samples at the PUSPATI site and its neutrons

International Nuclear Information System (INIS)

Rahman, M.T.A.

1983-01-01

The determination of the natural background radioactivity in water samples has been made at the PUSPATI site and its environs. The study was performed in January 1981 until June 1981. Samples of river, rain and tap water are periodically collected and analyzed in order to determine gross alpha and gross beta activity. In general, the total radioactivity of water is considerably low. The mean concentration of gross alpha in river water and tap water samples are 1.2 +- 0.1 and 0.2 +- 0.1 pCi/ respectively. The level of gross alpha in rain water is however, below the background rate of the detector. The mean concentration of gross beta in river water, tap water and rain water samples are 4.2 +- 0.6, 1.6 +- 0.3, and 1.9 +- 0.3 pCi/ respectively. (author)

Sand transport, erosion and granular electrification

DEFF Research Database (Denmark)

Merrison, J.P.

2012-01-01

is expanding our current understanding and outline the areas of advancement needed in the future. Presentation is made of current models for wind driven detachment/entrainment and the transport rates of sand and dust, including the effects of contact induced grain electrification. This ubiquitous phenomenon...... can affect grain transport through the generation of intense electric fields and processes of electrostatic assembly. Importantly the transport of sand is characterized by saltation, which is known to be an active process for erosion and therefore a source for dust and sand formation. Using novel...... erosion simulation techniques the link between grain transport rates and erosion rates has been quantified. Furthermore this can be linked to production rates for dust and has been associated with chemical and mineral alteration through a process of mechanical activation of fractured surfaces. This work...

High rate of vaginal erosions associated with the mentor ObTape.

Science.gov (United States)

Yamada, Brian S; Govier, Fred E; Stefanovic, Ksenija B; Kobashi, Kathleen C

2006-08-01

The transobturator tape method is a newer surgical technique for the treatment of stress urinary incontinence. Limited data exist related to complications with this approach or the types of mesh products used. We report our experience with vaginal erosions associated with the Mentor ObTape and American Medical Systems Monarc transobturator slings. Beginning in December 2003 selected female patients with anatomic urinary incontinence were prospectively followed after placement of the Mentor ObTape. Beginning in January 2004 we also began using the American Medical Systems Monarc in similar patients. Patients were admitted overnight after surgery, discharged on oral antibiotics, and seen in the clinic at 6 weeks postoperatively. A total of 67 patients have undergone placement of the Mentor ObTape and 9 of those patients (13.4%) have had vaginal extrusions of the sling. Eight patients reported a history of persistent vaginal discharge. One patient presented initially to an outside facility with a left thigh abscess tracking to the left inguinal incision site. Each patient was taken back to the operating room for mesh removal. A total of 56 patients have undergone placement of the AMS Monarc and none have had any vaginal erosions. Our high rate of vaginal extrusion using the ObTape has led us to discontinue the use of this product in our institution. Continued followup of all of these patients will be of critical importance.

Gross National Happiness

DEFF Research Database (Denmark)

Giri, Krishna Prasad; Kjær-Rasmussen, Lone Krogh

This paper investigates practices related to the ideology of infusing Gross National Happiness (GNH) into school curriculum, the effectiveness of the meditation and mind training and the implication of GNH for school environment. It also explores how GNH ambience has been managed and practiced...... of Gross National Happiness and Educating for Gross National happiness....

THE INFLUENCE OF CONVERSION MODEL CHOICE FOR EROSION RATE ESTIMATION AND THE SENSITIVITY OF THE RESULTS TO CHANGES IN THE MODEL PARAMETER

Directory of Open Access Journals (Sweden)

Nita Suhartini

2010-06-01

Full Text Available A study of soil erosion rates had been done on a slightly and long slope of cultivated area in Ciawi - Bogor, using 137Cs technique. The objective of the present study was to evaluate the applicability of the 137Cs technique in obtaining spatially distributed information of soil redistribution at small catchment. This paper reports the result of the choice of conversion model for erosion rate estimates and the sensitive of the changes in the model parameter. For this purpose, small site was selected, namely landuse I (LU-I. The top of a slope was chosen as a reference site. The erosion/deposit rate of individual sampling points was estimated using the conversion models, namely Proportional Model (PM, Mass Balance Model 1 (MBM1 and Mass Balance Model 2 (MBM2. A comparison of the conversion models showed that the lowest value is obtained by the PM. The MBM1 gave values closer to MBM2, but MBM2 gave a reliable values. In this study, a sensitivity analysis suggest that the conversion models are sensitive to changes in parameters that depend on the site conditions, but insensitive to changes in  parameters that interact to the onset of 137Cs fallout input.   Keywords: soil erosion, environmental radioisotope, cesium

Soil erosion in Slovene Istria

Directory of Open Access Journals (Sweden)

Matjaž Mikoš

2009-12-01

Full Text Available From the end of nineties of the 20th century, intense hydrologic and geomorphologic research is taking place in the Slovene Istria. As a part of this research also studies on soil erosion were undertaken in the period from 2005 to 2008. The field measurements were under taken onclosed 1m2 large erosion plots under three different land uses (on bare soils in an olive grove, on an overgrown meadow, in a forest, placed south of the Marezige village in the Rokava River basin.We show weekly measurements of surface erosion (interrill erosion for the period of 13 months (the end of March 2005 – the end of April 2006, as well as monthly and seasonal averages together with selected linear statistical correlations between soil erosion and weather parameters.From May 2005 to April 2006 the interrill erosion on bare soils in an olive grove with an inclination of 5.5° amounted to 9013 g/m2 (90 t/ha that corresponds to surface lowering rate of 8.5 mm/yr; on an overgrown meadow with an inclination of 9.4° it amounted to 168 g/m2 (1,68 t/ha that corresponds to surface lowering rate of 0.16 mm//yr; and in a forest with an inclination of 7.8° it amounted to 391 g/m2 (3,91 t/ha and in a forest with an inclination of 21.4° it amounted to 415 g/m2 (4,15 t/ha, respectively, that corresponds to surface lowering rate of 0.4 mm/yr.

A Method Validation for Determination of Gross Alpha and Gross Beta in Water Sample Using Low Background Gross Alpha/ Beta Counting System

International Nuclear Information System (INIS)

Zal Uyun Wan Mahmood; Norfaizal Mohamed; Nita Salina Abu Bakar

2016-01-01

Method validation (MV) for the measurement of gross alpha and gross beta activity in water (drinking, mineral and environmental) samples using Low Background Gross Alpha/ Beta Counting System was performed to characterize precision, accuracy and reliable results. The main objective of this assignment is to ensure that both the instrument and method always good performed and resulting accuracy and reliable results. Generally, almost the results of estimated RSD, z-score and U_s_c_o_r_e were reliable which are recorded as ≤30 %, less than 2 and less than 1.5, respectively. Minimum Detected Activity (MDA) was estimated based on the counting time of 100 minutes and present background counting value of gross alpha (0.01 - 0.35 cpm) and gross beta (0.50 - 2.18 cpm). Estimated Detection Limit (DL) was 0.1 Bq/ L for gross alpha and 0.2 Bq/ L for gross beta and expended uncertainty was relatively small of 9.77 % for gross alpha and 10.57 % for gross beta. Align with that, background counting for gross alpha and gross beta was ranged of 0.01 - 0.35 cpm and 0.50 - 2.18 cpm, respectively. While, sample volume was set at minimum of 500 mL and maximum of 2000 mL. These proven the accuracy and precision result that are generated from developed method/ technique is satisfactory and method is recommended to be used. Therefore, it can be concluded that the MV found no doubtful on the ability of the developed method. The test result showed the method is suitable for all types of water samples which are contained several radionuclides and elements as well as any impurities that interfere the measurement analysis of gross alpha and gross beta. (author)

Effectiveness of conservation agriculture practices on soil erosion processes in semi-arid areas of Zimbabwe

Science.gov (United States)

Chikwari, Emmanuel; Mhaka, Luke; Gwandu, Tariro; Chipangura, Tafadzwa; Misi Manyanga, Amos; Sabastian Matsenyengwa, Nyasha; Rabesiranana, Naivo; Mabit, Lionel

2016-04-01

- The application of fallout radionuclides (FRNs) in soil erosion and redistribution studies has gained popularity since the late 1980s. In Zimbabwe, soil erosion research was mostly based on conventional methods which included the use of erosion plots for quantitative measurements and erosion models for predicting soil losses. Only limited investigation to explore the possibility of using Caesium-137 (Cs-137) has been reported in the early 1990s for undisturbed and cultivated lands in Zimbabwe. In this study, the Cs-137 technique was applied to assess the impact of soil conservation practices on soil losses and to develop strategies and support effective policies that help farmers in Zimbabwe for sustainable land management. The study was carried out at the Makoholi research station 30 km north of the Masvingo region which is located 260 km south of Harare. The area is semi-arid and the study site comprises coarse loamy sands, gleyic lixisols. The conservation agriculture (CA) practices used within the area since 1988 include (i) direct seeding (DS) with mulch, (ii) CA basins with mulch, and (iii) 18 years direct seeding, left fallow for seven years and turned into conventional tillage since 2012 (DS/F/C). The Cs-137 reference inventory was established at 214 ± 16 Bq/m2. The mean inventories for DS, CA basins and DS/F/C were 195, 190 and 214 Bq/m2 respectively. Using the conversion Mass Balance Model 2 on the Cs-137 data obtained along transects for each of the practices, gross erosion rates were found to be 7.5, 7.3 and 2.6 t/ha/yr for direct seeding, CA basins and the DS/F/C while the net erosion rates were found to be 3.8, 4.6 and 0 t/ha/yr respectively. Sediment delivery ratios were 50%, 63% and 2% in the respective order. These preliminary results showed the effectiveness of DS over CA basins in erosion control. The efficiency of fallowing in controlling excessive soil loss was significant in the plot that started as DS for 18 years but left fallow for 7

Bank erosion along the dam-regulated lower Roanoke River, North Carolina

Science.gov (United States)

Hupp, C.R.; Schenk, E.R.; Richter, J.M.; Peet, Robert K.; Townsend, Phil A.

2009-01-01

Dam construction and its impact on downstream fluvial processes may substantially alter ambient bank stability and erosion. Three high dams (completed between 1953 and 1963) were built along the Piedmont portion of the Roanoke River, North Carolina; just downstream the lower part of the river flows across largely unconsolidated Coastal Plain deposits. To document bank erosion rates along the lower Roanoke River, >700 bank-erosion pins were installed along 66 bank transects. Additionally, discrete measurements of channel bathymetry, turbidity, and presence or absence of mass wasting were documented along the entire study reach (153 km). A bank-erosion- floodplain-deposition sediment budget was estimated for the lower river. Bank toe erosion related to consistently high low-flow stages may play a large role in increased mid- and upper-bank erosion. Present bank-erosion rates are relatively high and are greatest along the middle reaches (mean 63 mm/yr) and on lower parts of the bank on all reaches. Erosion rates were likely higher along upstream reaches than present erosion rates, such that erosion-rate maxima have since migrated downstream. Mass wasting and turbidity also peak along the middle reaches; floodplain sedimentation systematically increases downstream in the study reach. The lower Roanoke River isnet depositional (on floodplain) with a surplus of ??2,800,000 m3yr. Results suggest that unmeasured erosion, particularly mass wasting, may partly explain this surplus and should be part of sediment budgets downstream of dams. ?? 2009 The Geological Society of America.

Extremely low long-term erosion rates around the Gamburtsev Mountains in interior East Antarctica

Science.gov (United States)

Cox, S. E.; Thomson, S. N.; Reiners, P. W.; Hemming, S. R.; van de Flierdt, T.

2010-11-01

The high elevation and rugged relief (>3 km) of the Gamburtsev Subglacial Mountains (GSM) have long been considered enigmatic. Orogenesis normally occurs near plate boundaries, not cratonic interiors, and large-scale tectonic activity last occurred in East Antarctica during the Pan-African (480-600 Ma). We sampled detrital apatite from Eocene sands in Prydz Bay at the terminus of the Lambert Graben, which drained a large pre-glacial basin including the northern Gamburtsev Mountains. Apatite fission-track and (U-Th)/He cooling ages constrain bedrock erosion rates throughout the catchment. We double-dated apatites to resolve individual cooling histories. Erosion was very slow, averaging 0.01-0.02 km/Myr for >250 Myr, supporting the preservation of high elevation in interior East Antarctica since at least the cessation of Permian rifting. Long-term topographic preservation lends credence to postulated high-elevation mountain ice caps in East Antarctica since at least the Cretaceous and to the idea that cold-based glaciation can preserve tectonically inactive topography.

Experiments on Erosion of Mud from the Danish Wadden Sea

DEFF Research Database (Denmark)

Johansen, C.; Larsen, Torben; Petersen, O.

1994-01-01

Experiments on erosion and consolidation of natural cohesive sediments from the harbour of Esbjerg located in the Danish Watten Sea were conducted using a rotating annular flume. The objective of the paper is to describe the erosion rate of deposited beds and relate the erosion rate...

The barley straw residues avoid high erosion rates in persimmon plantations. Eastern Spain

Science.gov (United States)

Cerdà, Artemi; González Pelayo, Óscar; Giménez-Morera, Antonio; Jordán, Antonio; Novara, Agata; Pereira, Paulo; Mataix-Solera, Jorge

2015-04-01

World persimmon production is 4 Millions tones and China produce more than 80 % of the total world yield. Korea and Japan are the second and the third producers respectively with 0.4 and 0.2 millions tones, and all three Asian countries concentrate more than 95 % of the world production. Spain produce less than 0.1 million tones but there is a sudden increase in new plantations due to the high prices and the new marked developed in Europe, Brazil and Arabic countries. The new chemically managed and highly mechanized plantations in Eastern Spain are using high doses of herbicides and the lack of vegetation is triggering high erosion rates. This paper aims to contribute with information about the soil losses on this new persimmon plantations and to develop strategies to reduce the soil and water losses. A 15 years old plantation of persimmon (Dyospirus lotus) was selected in Eastern Spain (Canals Municipality, La Costera District) to measure the soil losses on No-Tillage bare (herbicide treatments) management and on barley straw covered plots. The straw cover was applied 3 days before the expereriments at at doses that cover more than 50 % of the soil surface using 75 gr of straw per m2. Rainfall simulations under 55 mm h-1 rainfall intensity during one hour on 0.25 m2 plots were carried out on plots paired plots: bare and covered with straw. The measurements were carried out during July 2014 on paired plots, under very dry soil moisture contents ranging from 4.65 to 7.87 %. The results show that the 3% cover of vegetation of the control plots moved to more than 60% due to the application of the straw. This induced a delayed ponding (from 60 to 309 seconds) and surface runoff (from 262 to 815 seconds) and runoff outlet (418 to 1221 seconds). The runoff coefficients moved from 60 % in the control plots to 29 % in the straw covered and the runoff sediment concentration was dramatically reduced from 11 to 1 g l-1. The total soil losses were higher that 1 Kg per plot in

Determination of gross alpha and gross beta in soil around repository facility at Bukit Kledang, Perak, Malaysia

Science.gov (United States)

Adziz, Mohd Izwan Abdul; Siong, Khoo Kok

2018-04-01

Recently, the Long Term Storage Facility (LTSF) in Bukit Kledang, Perak, Malaysia, has been upgraded to repository facility upon the completion of decontamination and decommissioning (D&D) process. Thorium waste and contaminated material that may contain some minor amounts of thorium hydroxide were disposed in this facility. This study is conducted to determine the concentrations of gross alpha and gross beta radioactivities in soil samples collected around the repository facility. A total of 12 soil samples were collected consisting 10 samples from around the facility and 2 samples from selected residential area near the facility. In addition, the respective dose rates were measured 5 cm and 1 m above the ground by using survey meter with Geiger Muller (GM) detector and Sodium Iodide (NaI) detector. Soil samples were collected using hand auger and then were taken back to the laboratory for further analysis. Samples were cleaned, dried, pulverized and sieved prior to analysis. Gross alpha and gross beta activity measurements were carried out using gas flow proportional counter, Canberra Series 5 XLB - Automatic Low Background Alpha and Beta Counting System. The obtained results show that, the gross alpha and gross beta activity concentration ranged from 1.55 to 5.34 Bq/g with a mean value of 3.47 ± 0.09 Bq/g and 1.64 to 5.78 Bq/g with a mean value of 3.49 ± 0.09 Bq/g, respectively. These results can be used as an additional data to represent terrestrial radioactivity baseline data for Malaysia environment. This estimation will also serve as baseline for detection of any future related activities of contamination especially around the repository facility area.

Corneal erosions, bacterial contamination of contact lenses, and microbial keratitis.

Science.gov (United States)

Willcox, Mark D P; Naduvilath, Thomas J; Vaddavalli, Pravin K; Holden, Brien A; Ozkan, Jerome; Zhu, Hua

2010-11-01

To estimate the rate of corneal erosion coupled with gram-negative bacterial contamination of contact lenses and compare this with the rate of microbial keratitis (MK) with contact lenses. The rate of corneal erosion and contact lens contamination by gram-negative bacteria were calculated from several prospective trials. These rates were used to calculate the theoretical rate of corneal erosion happening at the same time as wearing a contact lens contaminated with gram-negative bacteria. This theoretical rate was then compared with the rates of MK reported in various epidemiological and clinical trials. Corneal erosions were more frequent during extended wear (0.6-2.6% of visits) compared with daily wear (0.01-0.05% of visits). No corneal erosions were observed for lenses worn on a daily disposable basis. Contamination rates for lenses worn on a daily disposable basis were the lowest (2.4%), whereas they were the highest for low Dk lenses worn on an extended wear basis (7.1%). The estimated rate of corneal erosions occurring at the same time as wearing lenses contaminated with gram-negative bacteria was the lowest during daily wear of low Dk lenses (1.56/10,000 [95% CI: 0.23-10.57]) and the highest during extended wear of high Dk lenses (38.55/10,000 [95% CI: 24.77-60.04]). These rates were similar in magnitude to the rates reported for MK of different hydrogel lenses worn on differing wear schedules. The coincidence of corneal erosions during lens wear with gram-negative bacterial contamination of lenses may account for the relative incidence of MK during lens wear with different lens materials and modes of use.

The influence of material hardness on liquid droplet impingement erosion

International Nuclear Information System (INIS)

Fujisawa, Nobuyuki; Yamagata, Takayuki; Takano, Shotaro; Saito, Kengo; Morita, Ryo; Fujiwara, Kazutoshi; Inada, Fumio

2015-01-01

Highlights: • Liquid droplet impingement erosion is studied for various metal materials. • Average power dependency on droplet velocity is found as 7. • Power dependency on Vickers hardness is found as −4.5. • An empirical formula is constructed for erosion rates of metal materials. • Predicted erosion rate is well correlated with experiment within a factor of 1.5. - Abstract: This paper describes the experimental study on the liquid droplet impingement erosion of metal materials to understand the influence of material hardness on the erosion rate. The experiment is carried out using a water spray jet apparatus with a condition of relatively thin liquid film thickness. The metal materials tested are pure aluminum, aluminum alloy, brass, mild steel, carbon steel and stainless steel. The liquid droplets considered are 30 ± 5 μm in volume average diameter of water, which is the same order of droplet diameter in the actual pipeline in nuclear/fossil power plants. In order to understand the influence of material hardness on the liquid droplet impingement erosion, the scanning electron microscope (SEM) observation on the eroded surface and the measurement of erosion rate are carried out in the terminal stage of erosion. The experimental results indicate that the erosion rates are expressed by the droplet velocity, volume flux, Vickers hardness and the liquid film thickness, which are fundamentals of the liquid droplet impingement erosion. The empirical formula shows that the power index for droplet velocity dependency is found to be 7 with a scattering from 5 to 9 depending on the materials, while the power index for Vickers hardness dependency is found as −4.5

The influence of material hardness on liquid droplet impingement erosion

Energy Technology Data Exchange (ETDEWEB)

Fujisawa, Nobuyuki, E-mail: fujisawa@eng.niigata-u.ac.jp [Visualization Research Center, Niigata University, 8050, Ikarashi 2-Nocho, Nishi-ku, Niigata 950-2181 (Japan); Yamagata, Takayuki, E-mail: yamagata@eng.niigata-u.ac.jp [Visualization Research Center, Niigata University, 8050, Ikarashi 2-Nocho, Nishi-ku, Niigata 950-2181 (Japan); Takano, Shotaro; Saito, Kengo [Graduate School of Science and Technology, Niigata University, 8050, Ikarashi 2-Nocho, Nishi-ku, Niigata 950-2181 (Japan); Morita, Ryo; Fujiwara, Kazutoshi; Inada, Fumio [Central Research Institute of Electric Power Industry, 2-11-1, Iwatokita, Komae, Tokyo 201-8511 (Japan)

2015-07-15

Highlights: • Liquid droplet impingement erosion is studied for various metal materials. • Average power dependency on droplet velocity is found as 7. • Power dependency on Vickers hardness is found as −4.5. • An empirical formula is constructed for erosion rates of metal materials. • Predicted erosion rate is well correlated with experiment within a factor of 1.5. - Abstract: This paper describes the experimental study on the liquid droplet impingement erosion of metal materials to understand the influence of material hardness on the erosion rate. The experiment is carried out using a water spray jet apparatus with a condition of relatively thin liquid film thickness. The metal materials tested are pure aluminum, aluminum alloy, brass, mild steel, carbon steel and stainless steel. The liquid droplets considered are 30 ± 5 μm in volume average diameter of water, which is the same order of droplet diameter in the actual pipeline in nuclear/fossil power plants. In order to understand the influence of material hardness on the liquid droplet impingement erosion, the scanning electron microscope (SEM) observation on the eroded surface and the measurement of erosion rate are carried out in the terminal stage of erosion. The experimental results indicate that the erosion rates are expressed by the droplet velocity, volume flux, Vickers hardness and the liquid film thickness, which are fundamentals of the liquid droplet impingement erosion. The empirical formula shows that the power index for droplet velocity dependency is found to be 7 with a scattering from 5 to 9 depending on the materials, while the power index for Vickers hardness dependency is found as −4.5.

IN SITU MEASUREMENT OF BEDROCK EROSION

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D. H. Rieke-Zapp

2012-07-01

Full Text Available While long term erosion rates of bedrock material may be estimated by dating methods, current day erosion rates are – if at all available – based on rough estimates or on point measurements. Precise quantification of short term erosion rates are required to improve our understanding of short term processes, for input in landscape evolution models, as well as for studying the mechanics and efficiency of different erosion processes in varying geomorphological settings. Typical current day erosion rates in the European Alps range from sub-millimetre to several millimetres per year depending on the dominant erosion processes. The level of surveying accuracy required for recurring sub-millimetre to millimetre measurements in the field is demanding. A novel surveying setup for in-situ measurement of bedrock erosion was tested recently in three different locations in Switzerland. Natural bedrock was investigated in the Gornera gorge close to Zermatt. Further on, bedrock samples were installed in exposed locations in the Erlenbach research watershed close to Einsiedeln, and in the Illgraben debris flow channel, located in the Canton Schwyz and Valais, respectively. A twofold measurement approach was chosen for all locations. For the first setup control points providing an absolute reference frame for recurrent measurements were embedded close to the area of interest. Close range photogrammetry was applied to measure surface changes on the bedrock samples. The precision for surface measurements in the field was 0.1 mm (1 σ and thus suitable for the application. The equipment needed for the surveys can easily be carried to the field. At one field site a structured light scanner was used along with the photogrammetric setup. Although the current generation of structured light scanners appeared less suitable for field application, data acquisition was much faster and checking the data for completeness in the field was straight forward. The latest

In Situ Measurement of Bedrock Erosion

Science.gov (United States)

Rieke-Zapp, D. H.; Beer, A.; Turowski, J. M.; Campana, L.

2012-07-01

While long term erosion rates of bedrock material may be estimated by dating methods, current day erosion rates are - if at all available - based on rough estimates or on point measurements. Precise quantification of short term erosion rates are required to improve our understanding of short term processes, for input in landscape evolution models, as well as for studying the mechanics and efficiency of different erosion processes in varying geomorphological settings. Typical current day erosion rates in the European Alps range from sub-millimetre to several millimetres per year depending on the dominant erosion processes. The level of surveying accuracy required for recurring sub-millimetre to millimetre measurements in the field is demanding. A novel surveying setup for in-situ measurement of bedrock erosion was tested recently in three different locations in Switzerland. Natural bedrock was investigated in the Gornera gorge close to Zermatt. Further on, bedrock samples were installed in exposed locations in the Erlenbach research watershed close to Einsiedeln, and in the Illgraben debris flow channel, located in the Canton Schwyz and Valais, respectively. A twofold measurement approach was chosen for all locations. For the first setup control points providing an absolute reference frame for recurrent measurements were embedded close to the area of interest. Close range photogrammetry was applied to measure surface changes on the bedrock samples. The precision for surface measurements in the field was 0.1 mm (1 σ) and thus suitable for the application. The equipment needed for the surveys can easily be carried to the field. At one field site a structured light scanner was used along with the photogrammetric setup. Although the current generation of structured light scanners appeared less suitable for field application, data acquisition was much faster and checking the data for completeness in the field was straight forward. The latest generation of compact

Extent of Cropland and Related Soil Erosion Risk in Rwanda

Directory of Open Access Journals (Sweden)

Fidele Karamage

2016-06-01

Full Text Available Land conversion to cropland is one of the major causes of severe soil erosion in Africa. This study assesses the current cropland extent and the related soil erosion risk in Rwanda, a country that experienced the most rapid population growth and cropland expansion in Africa over the last decade. The land cover land use (LCLU map of Rwanda in 2015 was developed using Landsat-8 imagery. Based on the obtained LCLU map and the spatial datasets of precipitation, soil properties and elevation, the soil erosion rate of Rwanda was assessed at 30-m spatial resolution, using the Revised Universal Soil Loss Equation (RUSLE model. According to the results, the mean soil erosion rate was 250 t·ha−1·a−1 over the entire country, with a total soil loss rate of approximately 595 million tons per year. The mean soil erosion rate over cropland, which occupied 56% of the national land area, was estimated at 421 t·ha−1·a−1 and was responsible for about 95% of the national soil loss. About 24% of the croplands in Rwanda had a soil erosion rate larger than 300 t·ha−1·a−1, indicating their unsuitability for cultivation. With a mean soil erosion rate of 1642 t·ha−1·a−1, these unsuitable croplands were responsible for 90% of the national soil loss. Most of the unsuitable croplands are distributed in the Congo Nile Ridge, Volcanic Range mountain areas in the west and the Buberuka highlands in the north, regions characterized by steep slopes (>30% and strong rainfall. Soil conservation practices, such as the terracing cultivation method, are paramount to preserve the soil. According to our assessment, terracing alone could reduce the mean cropland soil erosion rate and the national soil loss by 79% and 75%, respectively. After terracing, only a small proportion of 7.6% of the current croplands would still be exposed to extreme soil erosion with a rate >300 t·ha−1·a−1. These irremediable cropland areas should be returned to mountain forest to

Solid particle erosion of polymers and composites

Science.gov (United States)

Friedrich, K.; Almajid, A. A.

2014-05-01

After a general introduction to the subject of solid particle erosion of polymers and composites, the presentation focusses more specifically on the behavior of unidirectional carbon fiber (CF) reinforced polyetheretherketone (PEEK) composites under such loadings, using different impact conditions and erodents. The data were analyzed on the basis of a newly defined specific erosive wear rate, allowing a better comparison of erosion data achieved under various testing conditions. Characteristic wear mechanisms of the CF/PEEK composites consisted of fiber fracture, matrix cutting and plastic matrix deformation, the relative contribution of which depended on the impingement angles and the CF orientation. The highest wear rates were measured for impingement angles between 45 and 60°. Using abrasion resistant neat polymer films (in this case PEEK or thermoplastic polyurethane (TPU) ones) on the surface of a harder substrate (e.g. a CF/PEEK composite plate) resulted in much lower specific erosive wear rates. The use of such polymeric films can be considered as a possible method to protect composite surfaces from damage caused by minor impacts and erosion. In fact, they are nowadays already successfully applied as protections for wind energy rotor blades.

Gross domestic product growth rates as confined Lévy flights: Towards a unifying theory of economic growth rate fluctuations

Science.gov (United States)

Lera, Sandro Claudio; Sornette, Didier

2018-01-01

A model that combines economic growth rate fluctuations at the microscopic and macroscopic levels is presented. At the microscopic level, firms are growing at different rates while also being exposed to idiosyncratic shocks at the firm and sector levels. We describe such fluctuations as independent Lévy-stable fluctuations, varying over multiple orders of magnitude. These fluctuations are aggregated and measured at the macroscopic level in averaged economic output quantities such as GDP. A fundamental question is thereby to what extent individual firm size fluctuations can have a noticeable impact on the overall economy. We argue that this question can be answered by considering the Lévy fluctuations as embedded in a steep confining potential well, ensuring nonlinear mean-reversal behavior, without having to rely on microscopic details of the system. The steepness of the potential well directly controls the extent to which idiosyncratic shocks to firms and sectors are damped at the level of the economy. Additionally, the theory naturally accounts for business cycles, represented in terms of a bimodal economic output distribution and thus connects two so far unrelated fields in economics. By analyzing 200 years of U.S. gross domestic product growth rates, we find that the model is in good agreement with the data.

Using cosmogenic isotopes to measure basin-scale rates of erosion

International Nuclear Information System (INIS)

Bierman, P.R.; Steig, E.

1992-01-01

The authors present a new and different approach to interpreting the abundance of in situ-produced cosmogenic nuclides such as 36 Cl, 26 Al, and 10 Be. Unlike most existing models, which are appropriate for evaluating isotope concentrations on bedrock surfaces, this model can be used to interpret isotope concentration in fluvial sediment. Because sediment is a mixture of material derived from the entire drainage basin, measured isotope abundances can be used to estimate spatially-averaged rates of erosion and sediment transport. Their approach has the potential to provide geomorphologists with a relatively simple but powerful means by which to constrain rates of landscape evolution. The model considers the flux of cosmogenic isotopes into and out of various reservoirs. Implicit in model development are the assumptions that a geomorphic steady-state has been reached and that sampled sediment is spatially and temporally representative of all sediment leaving the basin. Each year, the impinging cosmic-ray flux produces a certain quantity of cosmogenic isotopes in the rock and soil of a drainage basin. For a basin in steady state, the outgoing isotope flux is also constant. They solve for the rate of mass loss as a function of isotope abundance in the sediment, the cosmic ray attenuation length, the isotope half life, and the effective isotope production rate. There are only a few published measurements of cosmogenic isotope abundance in sediment. They calculated model denudation rates for sediment samples from Zaire and central Texas. The denudation rates they calculated appear reasonable and are similar to those they have measured directly on granite landforms in Georgia and southeastern California and those calculated for the Appalachian Piedmont

Erosion products in disruption simulation experiments

International Nuclear Information System (INIS)

Safronov, V.; Arkhipov, N.; Bakhtin, V.; Barsuk, V.; Kurkin, S.; Mironova, E.; Toporkov, D.; Vasenin, S.; Zhitlukhin, A.; Arkhipov, I.; Werle, H.; Wuerz, H.

1998-01-01

Erosion of divertor materials under tokamak disruption event presents a serious problem of ITER technology. Erosion restricts the divertor lifetime and leads to production of redeposited layers of the material retaining large amount of tritium, which is a major safety issue for future fusion reactor. Since ITER disruptive heat loads are not achievable in existing tokamaks, material erosion is studied in special simulation experiments. Till now the simulation experiments have focused mainly on investigation of shielding effect and measurement of erosion rate. In the present work the properties of eroded and redeposited graphite are studied under condition typical for hard ITER disruption. (author)

Measurement of gross alpha and gross beta activity concentrations in human tooth

International Nuclear Information System (INIS)

Soeguet, Omer; Aydin, Mehmet Fatih; Kuecuekoender, Erdal; Zorer, Ozlem Selcuk; Dogru, Mahmut

2010-01-01

The gross alpha and gross beta activity concentrations were measured in human tooth taken from 3 to 6 age-groups to 40 and over ones. Accumulated teeth samples are investigated in two groups as under and above 18 years. The gross alpha and beta radioactivity of human tooth samples was measured by using a gas-flow proportional counter (PIC-MPC 9604-α/β counter). In tooth samples, for female age-groups, the obtained results show that the mean gross alpha and gross beta activity concentrations varied between 0.534-0.203 and 0.010-0.453 Bq g -1 and the same concentrations for male age-groups varied between 0.009-1.168 and 0.071-0.204 Bq g -1 , respectively.

Erosion of the first wall of Tokamaks

International Nuclear Information System (INIS)

Guseva, M.I.; Ionova, E.S.; Martynenko, Yu.V.

1980-01-01

An estimate of the rate of erosion of the wall due to sputtering and blistering requires knowledge of the fluxes and energies of the particles which go from the plasma to the wall, of the sputtering coefficients S, and of the erosion coefficients S* for blistering. The overall erosion coefficient is equal to the sum of the sputtering coefficient and the erosion coefficient for blistering. Here the T-20 Tokamak is examined as an example of a large-scale Tokamak. 18 refs

Decadal-scale variation in dune erosion and accretion rates: An investigation of the significance of changing storm tide frequency and magnitude on the Sefton coast, UK

Science.gov (United States)

Pye, K.; Blott, S. J.

2008-12-01

Monitoring of frontal dune erosion and accretion on the Sefton coast in northwest England over the past 50 years has revealed significant spatial and temporal variations. Previous work has shown that the spatial variations primarily reflect longshore differences in beach and nearshore morphology, energy regime and sediment budget, but the causes of temporal variations have not previously been studied in detail. This paper presents the results of work carried out to test the hypothesis that a major cause of temporal variation is changes in the frequency and magnitude of storms, surges and resulting high tides. Dune toe erosion/accretion records dating from 1958 have been compared with tide gauge records at Liverpool and Heysham. Relatively high dune erosion rates at Formby Point 1958-1968 were associated with a relatively large number of storm tides. Slower erosion at Formby, and relatively rapid accretion in areas to the north and south, occurred during the 1970's and 1980's when there were relatively few major storm tides. After 1990 rates of dune erosion at Formby increased again, and dunes to the north and south experienced slower accretion. During this period high storm tides have been more frequent, and the annual number of hours with water levels above the critical level for dune erosion has increased significantly. An increase in the rate of mean sea-level rise at both Liverpool and Heysham is evident since 1990, but we conclude that this factor is of less importance than the occurrence of extreme high tides and wave action associated with storms. The incidence of extreme high tides shows an identifiable relationship with the lunar nodal tidal cycle, but the evidence indicates that meteorological forcing has also had a significant effect. Storms and surges in the eastern Irish Sea are associated with Atlantic depressions whose direction and rate of movement have a strong influence on wind speeds, wave energy and the height of surge tides. However

Evaluating the Impacts of Climate Change on Soil Erosion Rates in Central Mexico

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Santos Martínez-Santiago

2017-07-01

Full Text Available Although water-eroded soil (WES resulting from human activities has been recognized as the leading global cause of land degradation, the soil erosion risks from climate change are not clear. Studies have reported that WES is the second most significant cause of soil loss in Mexico, and its future trajectory has not been sufficiently evaluated. The aims of this study are to 1 determine the impacts of climate change on WES and its distribution for the State of Aguascalientes, Mexico, and to 2 compare the present and future soil loss rates for the study unit (SU. The State of Aguascalientes is located in the “Region del Bajio.” The impact of climate change on WES was evaluated using the near-future divided world scenario (A2 presented in the IPCC Fourth Assessment Report. Daily temperature and precipitation data from 18 weather stations were downscaled to model historic laminar water erosion (HLWE and changes therein in the A2 near-future scenario for 2010–2039 (LWEScA2. Due to future changes in mean annual rainfall (MAR levels, a change in the LWEScA2 of between 1.6 and 8.9% could result in average soil losses up to 475.4 t ha-1 yr-1, representing a loss of slightly more than a 30-mm layer of mountain soil per year. The risk zones, classified as class 4 for LWE, are located to western of the State in part of municipalities of Calvillo, Jesus María, San José de Gracia y Cosio, where there are typical hills and falls with soil very sensitive to rain erosion.

Soil carbon and nitrogen erosion in forested catchments: implications for erosion-induced terrestrial carbon sequestration

Science.gov (United States)

E. M. Stacy; S. C. Hart; C. T. Hunsaker; D. W. Johnson; A. A. Berhe

2015-01-01

Lateral movement of organic matter (OM) due to erosion is now considered an important flux term in terrestrial carbon (C) and nitrogen (N) budgets, yet most published studies on the role of erosion focus on agricultural or grassland ecosystems. To date, little information is available on the rate and nature of OM eroded from forest ecosystems. We present annual...

Erosion of buffer caused by groundwater leakages

International Nuclear Information System (INIS)

Autio, J.; Hanana, K.; Punkkinen, O.; Koskinen, K.; Olin, M.

2010-01-01

at a total mass of 1-10 g per litre of accumulated water flow. The erosion rates were observed to depend on several different parameters such as salinity, flow rate, length of flow path and type of bentonite and, therefore, the present results, which are based on limited types of bentonite, flow rates and salinities, are regarded as preliminary only. Erosion test have been carried out to simulate the erosion with different types of experimental set-ups using different flow rates and salinities. The actual flow rate, Q(t), depends on the opening of the flow channel, pressure difference between inlet and outlet together with the length of the flow channel. The complete phenomenological modelling of these subtle phenomena is going on and it will probably take few years before those results can be used directly for erosion modelling. The mass of the eroded material within a channel was estimated in the first phase of work using a 1-D erosion model. In this model the mass of eroded material was considered in terms of concentration of eroded solids, c, in a predefined volume of fluid. The change of concentration in time is considered to depend on advection of solids to and from the volume in question by fluid flow, change of radius, R(z,t), entrainment of material and gravitational settling. Entrainment, σ(z,t) is modelled using a power law function combined with a Heaviside step function to reflect threshold shear stress for the onset of entrainment. In the current version the gravity term, G(z,t), lumps various effects like buoyancy, Soret and Magnus effects. The results of work imply that the physical and theoretical model developed can simulate the clear dependency of erosion rate on flow rate, salinity and time. (authors)

Runoff erosion

OpenAIRE

Evelpidou, Niki (Ed.); Cordier, Stephane (Ed.); Merino, Agustin (Ed.); Figueiredo, Tomás de (Ed.); Centeri, Csaba (Ed.)

2013-01-01

Table of Contents PART I – THEORY OF RUNOFF EROSION CHAPTER 1 - RUNOFF EROSION – THE MECHANISMS CHAPTER 2 - LARGE SCALE APPROACHES OF RUNOFF EROSION CHAPTER 3 - MEASURING PRESENT RUNOFF EROSION CHAPTER 4 - MODELLING RUNOFF EROSION CHAPTER 5 - RUNOFF EROSION AND HUMAN SOCIETIES: THE INFLUENCE OF LAND USE AND MANAGEMENT PRACTICES ON SOIL EROSION PART II - CASE STUDIES CASE STUDIES – INTRODUCTION: RUNOFF EROSION IN MEDITERRANEAN AREA CASE STUDY 1: Soil Erosion Risk...

Plot-slope soil erosion using 7Be measurement and rill fractal dimension

International Nuclear Information System (INIS)

Zhang Fengbao; Yang Mingyi

2010-01-01

In this study, we intended to use 7 Be measurement and fractal theory to quantify soil erosion process on slope. The results showed that contribution rate of inter rill erosion was more than that of rill erosion during early stage of rainfall. When it rained, contribution rate of rill erosion began to be higher than inter rill erosion and become the main part of erosion during medium stage of rainfall. The trend of contribution rate of inter rill erosion was growing and the rill erosion was lowering during late stage of rainfall. Rill fractal dimension on the plot slope was almost growing larger during rainfall,growing quickly during early stage of rainfall and slowly during the late stage. Correlations was positive between rill fractal dimension and total erosion amount, also positive between rill fractal dimension and rill erosion. The correlations was positive between rill fractal dimension variation and total erosion amount, also was positive between rill fractal dimension variation and rill erosion amount. The best correlation was observed between rill fractal dimension and rill erosion amount. These results indicated that the rill fractal dimension on the plot slope could represent the development process of rill,the complex degree of rill and the variation of soil erosion intensity on the entire slope. (authors)

Catchment-wide weathering and erosion rates of mafic, ultramafic, and granitic rock from cosmogenic meteoric 10Be/9Be ratios

Science.gov (United States)

Dannhaus, N.; Wittmann, H.; Krám, P.; Christl, M.; von Blanckenburg, F.

2018-02-01

Quantifying rates of weathering and erosion of mafic rocks is essential for estimating changes to the oceans alkalinity budget that plays a significant role in regulating atmospheric CO2 levels. In this study, we present catchment-wide rates of weathering, erosion, and denudation measured with cosmogenic nuclides in mafic and ultramafic rock. We use the ratio of the meteoric cosmogenic nuclide 10Be, deposited from the atmosphere onto the weathering zone, to stable 9Be, a trace metal released by silicate weathering. We tested this approach in stream sediment and water from three upland forested catchments in the north-west Czech Republic. The catchments are underlain by felsic (granite), mafic (amphibolite) and ultramafic (serpentinite) lithologies. Due to acid rain deposition in the 20th century, the waters in the granite catchment exhibit acidic pH, whereas waters in the mafic catchments exhibit neutral to alkaline pH values due to their acid buffering capability. The atmospheric depositional 10Be flux is estimated to be balanced with the streams' dissolved and particulate meteoric 10Be export flux to within a factor of two. We suggest a correlation method to derive bedrock Be concentrations, required as an input parameter, which are highly heterogeneous in these small catchments. Derived Earth surface metrics comprise (1) Denudation rates calculated from the 10Be/9Be ratio of the "reactive" Be (meaning sorbed to mineral surfaces) range between 110 and 185 t km-2 y-1 (40 and 70 mm ky-1). These rates are similar to denudation rates we obtained from in situ-cosmogenic 10Be in quartz minerals present in the bedrock or in quartz veins in the felsic and the mafic catchment. (2) The degree of weathering, calculated from the fraction of 9Be released from primary minerals as a new proxy, is about 40-50% in the mafic catchments, and 10% in the granitic catchment. Lastly, (3) erosion rates were calculated from 10Be concentrations in river sediment and corrected for sorting

Assessment of soil erosion sensitivity and post-timber-harvesting erosion response in a mountain environment of Central Italy

Science.gov (United States)

Borrelli, Pasquale; Schütt, Brigitta

2014-01-01

This study aimed to assess the effects of forest management on the occurrence of accelerated soil erosion by water. The study site is located in a mountainous area of the Italian Central Apennines. Here, forest harvesting is a widespread forestry activity and is mainly performed on the moderate to steep slopes of the highlands. Through modeling operations based on data on soil properties and direct monitoring of changes in the post-forest-harvesting soil surface level at the hillslope scale, we show that the observed site became prone to soil erosion after human intervention. Indeed, the measured mean soil erosion rate of 49 t ha- 1 yr- 1 for the harvested watershed is about 21 times higher than the rate measured in its neighboring undisturbed forested watershed (2.3 t ha- 1 yr- 1). The erosive response is greatly aggravated by exposing the just-harvested forest, with very limited herbaceous plant cover, to the aggressive attack of the heaviest annual rainfall without adopting any conservation practices. The erosivity of the storms during the first four months of field measurements was 1571 MJ mm h- 1 ha- 1 in total (i.e., from September to December 2008). At the end of the experiment (16 months), 18.8%, 26.1% and 55.1% of the erosion monitoring sites in the harvested watershed recorded variations equal or greater than 0-5, 5-10 and > 10 mm, respectively. This study also provides a quantification of Italian forestland surfaces with the same pedo-lithological characteristics exploited for wood supply. Within a period of ten years (2002-2011), about 9891 ha of coppice forest changes were identified and their potential soil erosion rates modeled.

The erosive potential of candy sprays

NARCIS (Netherlands)

Gambon, D.L.; Brand, H.S.; Nieuw Amerongen, A.V.

2009-01-01

Objective To determine the erosive potential of seven different commercially available candy sprays in vitro and in vivo. Material and methods The erosive potential was determined in vitro by measuring the pH and neutralisable acidity. The salivary pH and flow rate were measured in healthy

Ionizing radiation sensitivity and the rate of gross chromosomal rearrangement in yeast

International Nuclear Information System (INIS)

Brown, J.A.; Brown, M.

2003-01-01

Full text: Many of the genes conferring resistance to DNA damage in the yeast Saccharomyces cerevisiae have been identified. The systematic deletion of every open reading frame presents the opportunity to make great strides in determining the physiological role of many genes whose function has remained elusive. The ability to discriminate among all of the strains carrying unique non-essential gene deletions in a pool has allowed us to screen for novel genes required for survival to ionizing radiation. Many of these genes have not yet been characterized. A possible role for these genes could be in the initial sensing of the double strand break introduced by ionizing radiation, the cell cycle arrest permitting the cell time for the repair process, or directly in the repair. A consequence of a failure of any of these functions could result in an increase in mutation rate as well the more detrimental gross chromosomal rearrangement (GCR). We tested the hypothesis that any gene which when deleted caused an increase in ionizing radiation sensitivity would also demonstrate an increase in mutation rate and GCR. This turned out not to be the case with many having no significant increase and one in particular which caused a significant decrease in GCR. Data on several of the more intriguing genes will be presented

Erosion of soil organic carbon: implications for carbon sequestration

Science.gov (United States)

Van Oost, Kristof; Van Hemelryck, Hendrik; Harden, Jennifer W.; McPherson, B.J.; Sundquist, E.T.

2009-01-01

Agricultural activities have substantially increased rates of soil erosion and deposition, and these processes have a significant impact on carbon (C) mineralization and burial. Here, we present a synthesis of erosion effects on carbon dynamics and discuss the implications of soil erosion for carbon sequestration strategies. We demonstrate that for a range of data-based parameters from the literature, soil erosion results in increased C storage onto land, an effect that is heterogeneous on the landscape and is variable on various timescales. We argue that the magnitude of the erosion term and soil carbon residence time, both strongly influenced by soil management, largely control the strength of the erosion-induced sink. In order to evaluate fully the effects of soil management strategies that promote carbon sequestration, a full carbon account must be made that considers the impact of erosion-enhanced disequilibrium between carbon inputs and decomposition, including effects on net primary productivity and decomposition rates.

Erosion of Earthen Levees by Wave Action

Science.gov (United States)

Ozeren, Y.; Wren, D. G.; Reba, M. L.

2016-02-01

Earthen levees of aquaculture and irrigation reservoirs in the United States often experience significant erosion due to wind-generated waves. Typically constructed using local soils, unprotected levees are subjected to rapid erosion and retreat due to wind generated waves and surface runoff. Only a limited amount of published work addresses the erosion rates for unprotected levees, and producers who rely on irrigation reservoirs need an economic basis for selecting a protection method for vulnerable levees. This, in turn, means that a relationship between wave energy and erosion of cohesive soils is needed. In this study, laboratory experiments were carried out in order to quantify wave induced levee erosion and retreat. A model erodible bank was packed using a soil consisting of approximately 14% sand, 73% silt, and 13% clay in a 20.6 m long 0.7 m wide and 1.2 m deep wave tank at the USDA-ARS, National Sedimentation Laboratory in Oxford MS. The geometry of the levee face was monitored by digital camera and the waves were measured by means of 6 capacitance wave staffs. Relationships were established between levee erosion, edge and retreat rates, and incident wave energy.

Erosion and its rate on an accumulative Polish dune coast: the effects of the January 2012 storm surge

Directory of Open Access Journals (Sweden)

Tomasz A. Łabuz

2014-01-01

Full Text Available The Polish coast is a non-tidal area; its shores are affected mainly by autumn-winter storm surges. Those of 6 and 14 January 2012 are representative of the forces driving the erosion of normally accumulative sections of coastal dunes, monitored by the author since 1997. The sea level maximum during these two storm surges reached 1.2 to 1.5 m amsl along the Polish coast. Land forms up to 3 m amsl were inundated. Beaches and low parts of the coast up to this height were rebuilt by sea waves attacking the coast for almost 12 days. Quantitative analyses of the morphological dynamics of the coastal dunes are presented for 57 profiles located along the coast. Only those accumulative sections of the Polish coast are analysed where sand accumulation did occur and led to new foredune development. The mean rate of dune erosion was 2.5 m3 per square metre with an average toe retreat of 1.4 m. Erosion understood as dune retreat was greater when a beach was lower (correlation coefficient 0.8. Dune erosion did not occur on coasts with beaches higher than 3.2 m or on lower ones covered by embryo dunes.

Volumetric measurement of river bank erosion from sequential historical aerial photography

Science.gov (United States)

Spiekermann, Raphael; Betts, Harley; Dymond, John; Basher, Les

2017-11-01

Understanding of the relative contribution of bank erosion to sediment budgets in New Zealand is limited. Few measurements of bank erosion rates exist, and this is a major limitation to the development of a locally calibrated model of bank erosion. The New Zealand sediment budget model, SedNetNZ, predicts bank erosion based on preliminary data, and this study aims to underpin the development of an improved model for bank erosion. Photogrammetric techniques and LiDAR were used to collect data on bank erosion rates for five different river reaches, ranging from 3 to 14 km in length, in the Kaipara Catchment, Northland, New Zealand. Changing river channel planform between the 1950s and 2015 was assessed using four to five well-spaced dates of historical aerial photographs. Changes in planform were combined with bank height, to calculate erosion and accretion volumes which were compared with SedNetNZ modelled estimates. Erosion and accretion is relatively evenly balanced in the study sites. The largest difference in terms of relative proportions of erosion and accretion are found along the Tangowahine River (13.4 km reach length), where 492,000 m3 of sediment eroded between 1956 and 2015 compared to 364,000 m3 of accretion. Lateral migration rates (erosion) for the five river reaches range between 0.14 m yr- 1 and 0.21 m yr- 1 and are comparable with those measured by previous assessments in New Zealand. The migration rates in channel widths per year for the three larger rivers (stream order 5-6) range between 0.4% and 0.8% of channel width per year. In contrast, the smaller streams (stream order 3-4) are retreating more rapidly, with width-averaged rates of 1.7% and 3.0%. Current SedNetNZ modelling tends to underestimate the bank height and greatly overestimates the migration rate.

Long-term predictive capability of erosion models

Science.gov (United States)

Veerabhadra, P.; Buckley, D. H.

1983-01-01

A brief overview of long-term cavitation and liquid impingement erosion and modeling methods proposed by different investigators, including the curve-fit approach is presented. A table was prepared to highlight the number of variables necessary for each model in order to compute the erosion-versus-time curves. A power law relation based on the average erosion rate is suggested which may solve several modeling problems.

The control of divertor carbon erosion/redeposition in the DIII-D tokamak

International Nuclear Information System (INIS)

Whyte, D.G.; West, W.P.; Wong, C.P.C.

2001-01-01

The DIII-D tokamak has demonstrated an operational scenario where the graphite-covered divertor is free of net erosion. Reduction of divertor carbon erosion is accomplished using a low temperature (detached) divertor plasma that eliminates physical sputtering. Likewise, the carbon source rate arising from chemical erosion is found to be very low in the detached divertor. Near strikepoint regions, the rate of carbon deposition is ∼3 cm/burn-year, with a corresponding hydrogenic codeposition rate >1kg/m 2 /burn-year; rates both problematic for steady-state fusion reactors. The carbon net deposition rate in the divertor is consistent with carbon arriving from the core plasma region. Carbon influx from the main wall is measured to be relatively large in the high-density detached regime and is of sufficient magnitude to account for the deposition rate in the divertor. Divertor redeposition is therefore determined by non-divertor erosion and transport. Despite the success in reducing divertor erosion on DIII-D with detachment, no significant reduction is found in the core plasma carbon density, illustrating the importance of non-divertor erosion and the complex coupling between erosion/redeposition and impurity plasma transport. (author)

Parameters Affecting the Erosive Burning of Solid Rocket Motor

Directory of Open Access Journals (Sweden)

Abdelaziz Almostafa

2018-01-01

Full Text Available Increasing the velocity of gases inside solid rocket motors with low port-to-throat area ratios, leading to increased occurrence and severity of burning rate augmentation due to flow of propellant products across burning propellant surfaces (erosive burning, erosive burning of high energy composite propellant was investigated to supply rocket motor design criteria and to supplement knowledge of combustion phenomena, pressure, burning rate and high velocity of gases all of these are parameters affect on erosive burning. Investigate the phenomena of the erosive burning by using the 2’inch rocket motor and modified one. Different tests applied to fulfil all the parameters that calculated out from the experiments and by studying the pressure time curve and erosive burning phenomena.

Evaluation of Spatial-Temporal Variation of Soil Detachment Rate Potential in Rill Erosion, Case study: Doshmanziari Rainfed Lands, Fars province

Directory of Open Access Journals (Sweden)

H. Karimi

2017-01-01

Full Text Available Introduction: Soil erosion by water is one of the most widespread forms of land degradation and it has caused many undesirable consequences in last decades. On steep slopes, rill erosion is the most important type of erosion, which produces sediment and rill flow. It can be also considered as a vehicle for transporting soil particles detached from upland areas. Recent studies indicate that soil detachment rates are significantly influenced by land use. It is also known that there is a major difference between detachment rates of disturbed and natural soils (Zhang et al., 2003. Plowing rills especially in steep slopes increases sediment production. Sun et al. (2013 reported that the contribution of rill erosion in hill slope lands in china was more than 70%, which was approximately 50% of total soil erosion. In addition, measured soil loss is statistically related to hydraulic indicators such as slope, water depth, flow velocity, flow shear stress and stream power (Knapen et al., 2007. This study aims to evaluate the effects of hydraulic variables (shear stress and stream power on spatial-temporal soil detachment rate. The focus is on the plowing rills in hillslope areas under wheat dry farming cultivation. Materials and Methods: The study area is located in hilly slopes with the slope of 22.56% under dry farming wheat cultivation at 60 km of west of Shiraz, Iran. Top-down conventional plowing was carried out in order to create 10 meters furrows. Slope and cross sections of rills were measured throughout the experiment at 1 m intervals by rill-meter. Water was added to the top of the rills for 10 minutes and inflow rates were 10, 15 and 20 L min-1. Hydraulic parameters such as shear stress and stream power were calculated measuring rill morphology and water depth. Flow velocity and hydraulic radius along the different rill experiments were also calculated. Sediment concentrations were measured in three equal regular time and distance intervals

Polymers Erosion and Contamination Experiment Being Developed

Science.gov (United States)

deGroh, Kim K.; Banks, Bruce A.; Barney-Barton, Elyse A.; Sechkar, Edward; Hunt, Patricia

1999-01-01

The Polymers Erosion and Contamination Experiment (PEACE) is currently being developed at the NASA Lewis Research Center by the Electro-Physics Branch in conjunction with students and faculty from Hathaway Brown School in Cleveland. The experiment is a Get Away Special Canister shuttle flight experiment sponsored by the American Chemical Society. The two goals of this experiment are (1) to measure ram atomic oxygen erosion rates of approximately 40 polymers that have potential use in space applications and (2) to validate a method for identifying sources of silicone contamination that occur in the shuttle bay. Equipment to be used in this flight experiment is shown in the schematic diagram. Spacecraft materials subjected to attack by atomic oxygen in the space environment experience significant degradation over the span of a typical mission. Therefore, learning the rates of atomic oxygen erosion of a wide variety of polymers would be of great benefit to future missions. PEACE will use two independent techniques to determine the atomic oxygen erosion rates of polymers. Large (1-in.-diameter) samples will be used for obtaining mass loss. Preflight and postflight dehydrated masses will be obtained, and the mass lost during flight will be determined. Small (0.5-in.-diameter) samples will be protected with isolated particles (such as NaCl crystals) and then exposed to the space environment. After flight, the protective particles will be removed (washed off) and atomic force microscopy (AFM) will be used to measure the erosion depth from protected mesas. Erosion depth measurements are more sensitive than traditional mass measurements and are very useful for materials with low erosion yields or with very low fluence missions.

Influence of soil erosion on CO2 exchange within the CarboZALF manipulation experiment

Science.gov (United States)

Hoffmann, Mathias; Augustin, Jürgen; Sommer, Michael

2014-05-01

Agriculture in the hummocky ground moraine landscape of NE-Germany is characterized by an increase in energy crop cultivation, like maize or sorghum. Both enhance lateral C fluxes by erosion and induce feedbacks on C dynamics of agroecosystems as a result of the time limited land cover and the vigorous crop growth. However, the actual impact of these phenomena on the CO2-sink/-source function of agricultural landscapes, is still not clear. Therefore we established the interdisciplinary project 'CarboZALF' in 2009. In our field experiment CarboZALF-D we are monitoring CO2 fluxes for soil-plant systems, which cover all landscape relevant soil states in respect to erosion and deposition, like Albic Cutanic Luvisol, Calcic Cutanic Luvisol, Calcaric Regosol and Endogleyic Colluvic Regosol. Furthermore, we induced erosion / deposition in a manipulation experiment. Automated chamber systems (2.5 m, basal area 1 m2, transparent) are placed at the manipulated sites as well as at one site neither influenced by erosion, nor by deposition. CO2 flux modelling of high temporal resolution includes ecosystem respiration (Reco), gross primary productivity (GPP) and net ecosystem exchange (NEE) based on parallel and continuous measurements of the CO2 exchange, soil and air temperatures as well as photosynthetic active radiation (PAR). Modelling includes gap filling which is needed in case of chamber malfunctions and abrupt disturbances by farming practice. In our presentation we would like to show results of the CO2 exchange measurements for one year. Differences are most pronounced between the non-eroded and the colluvial soil: The Endogleyic Colluvic Regosol showed higher flux rates for Reco and NEE compared to the Albic Cutanic Luvisol. The eroded soil (Calcic Cutanic Luvisol) demonstrated CO2fluxes intermediate between the non-affected and depositional site. Site-specific consequences for the soil C stocks will be also discussed in the presentation.

Predicting the Rate of River Bank Erosion Caused by Large Wood Log

Science.gov (United States)

Zhang, N.; Rutherfurd, I.; Ghisalberti, M.

2016-12-01

When a single tree falls into a river channel, flow is deflected and accelerated between the tree roots and the bank face, increasing shear stress and scouring the bank. The scallop shaped erosion increases the diversity of the channel morphology, but also causes concern for adjacent landholders. Concern about increased bank erosion is one of the main reasons for large wood to still be removed from channels in SE Australia. Further, the hydraulic effect of many logs in the channel can reduce overall bank erosion rates. Although both phenomena have been described before, this research develops a hydraulic model that estimates their magnitude, and tests and calibrates this model with flume and field measurements, with logs with various configurations and sizes. Specifically, the model estimates the change in excess shear stress on the bank associated . The model addresses the effect of the log angle, distance from bank, and log size and flow condition by solving the mass continuity and energy conservation between the cross section at the approaching flow and contracted flow. Then, we evaluate our model against flume experiment preformed with semi-realistic log models to represent logs in different sizes and decay stages by comparing the measured and simulated velocity increase in the gap between the log and the bank. The log angle, distance from bank, and flow condition are systemically varied for each log model during the experiment. Final, the calibrated model is compared with the field data collected in anabranching channels of Murray River in SE Australia where there are abundant instream logs and regulated and consistent high flow for irrigation. Preliminary results suggest that a log can significantly increase the shear stress on the bank, especially when it positions perpendicular to the flow. The shear stress increases with the log angle in a rising curve (The log angle is the angle between log trunk and flow direction. 0o means log is parallel to flow with

Preliminary assessment of the potential for using cesium-137 technique to estimate rates of soil erosion on cultivated land in La Victoria I, Camaguey province of cuba

International Nuclear Information System (INIS)

Brigido, F.O.; Gandarilla Benitez, J.E.

1999-01-01

Despite a growing awareness that erosion on cultivated land in Cuba is a potential hazard to long term productivity, there is still only limited information on the rates involved, particularly long term values. The potential for using the radionuclide Caesium-137 as an environmental tracer to indicate sources of soil erosion on cultivated soils in La Victoria catchment is introduced. Use of Caesium-137 measurements to estimate rates of erosion and deposition is founded on comparison of the Caesium-137 inventories at individual sampling points with a reference inventory representing the local Caesium fallout input and thus the inventory to be expected at the site experiencing neither erosion nor deposition. Two models for converting Caesium-137 measurements to estimates of soil redistribution rates on studied site have been used, the Proportional Model and Mass Balance Model. Using the first one net soil erosion was calculated to be 17.6 t. Ha 1 - .year 1 - . Estimates of soil loss using a Mass Balance Model (Simplified Model 1 and Model 2) were found to be 30.2 and 30.6 t. Ha 1 - .year 1 - ,respectively. Preliminary results suggest that Caesium-137 technique may be of considerable value in assembling data on the rates and spatial distribution of soil loss and a reliable tool for developing of soil conservation program

Dynamic Analysis of Soil Erosion in Songhua River Watershed

Science.gov (United States)

Zhang, Yujuan; Li, Xiuhai; Wang, Qiang; Liu, Jiang; Liang, Xin; Li, Dan; Ni, Chundi; Liu, Yan

2018-01-01

In this paper, based on RS and GIS technology and Revised Universal Soil Loss Equation (RUSLE), the soil erosion dynamic changes during the two periods of 1990 and 2010 in Bin County was analyzed by using the Landsat TM data of the two periods, so as to reveal the soil erosion spatial distribution pattern and spatial and temporal dynamic evolution rule in the region. The results showed that: the overall patterns of soil erosion were basically the same in both periods, mainly featuring slight erosion and mild erosion, with the area proportions of 80.68% and 74.71% respectively. The slight and extremely intensive erosion changing rates showed a narrowing trend; mild, moderate and intensive erosion was increasing, with a trend of increased soil erosion; mild and intensive erosion were developing towards moderate erosion and moderate and extremely intensive erosion were progressing towards intensive erosion.

Synergistic erosion/corrosion of superalloys in PFB coal combustor effluent

Science.gov (United States)

Benford, S. M.; Zellars, G. R.; Lowell, C. E.

1981-01-01

Two Ni-based superalloys were exposed to the high velocity effluent of a pressurized fluidized bed coal combustor. Targets were 15 cm diameter rotors operating at 40,000 rpm and small flat plate specimens. Above an erosion rate threshold, the targets were eroded to bare metal. The presence of accelerated oxidation at lower erosion rates suggests erosion/corrosion synergism. Various mechanisms which may contribute to the observed oxide growth enhancement include erosive removal of protective oxide layers, oxide and subsurface cracking, and chemical interaction with sulfur in the gas and deposits through damaged surface layers.

Simulation of erosion by a particulate airflow through a ventilator

Science.gov (United States)

Ghenaiet, A.

2015-08-01

Particulate flows are a serious problem in air ventilation systems, leading to erosion of rotor blades and aerodynamic performance degradation. This paper presents the numerical results of sand particle trajectories and erosion patterns in an axial ventilator and the subsequent blade deterioration. The flow field was solved separately by using the code CFX- TASCflow. The Lagrangian approach for the solid particles tracking implemented in our inhouse code considers particle and eddy interaction, particle size distribution, particle rebounds and near walls effects. The assessment of erosion wear is based on the impact frequency and local values of erosion rate. Particle trajectories and erosion simulation revealed distinctive zones of impacts with high rates of erosion mainly on the blade pressure side, whereas the suction side is eroded around the leading edge.

Tectonic control of erosion in the southern Central Andes

Science.gov (United States)

Val, Pedro; Venerdini, Agostina L.; Ouimet, William; Alvarado, Patricia; Hoke, Gregory D.

2018-01-01

Landscape evolution modeling and global compilations of exhumation data indicate that a wetter climate, mainly through orographic rainfall, can govern the spatial distribution of erosion rates and crustal strain across an orogenic wedge. However, detecting this link is not straightforward since these relationships can be modulated by tectonic forcing and/or obscured by heavy-tailed frequencies of catchment discharge. This study combines new and published along-strike average rates of catchment erosion constrained by 10Be and river-gauge data in the Central Andes between 28°S and 36°S. These data reveal a nearly identical latitudinal pattern in erosion rates on both sides of the range, reaching a maximum of 0.27 mm/a near 34°S. Collectively, data on topographic and fluvial relief, variability of rainfall and discharge, and crustal seismicity suggest that the along-strike pattern of erosion rates in the southern Central Andes is largely independent of climate, but closely relates to the N-S distribution of shallow crustal seismicity and diachronous surface uplift. The consistently high erosion rates on either side of the orogen near 34°S imply that climate plays a secondary role in the mass flux through an orogenic wedge where the perturbation to base level is similar on both sides.

Erosion Pressure on the Danish Coasts

DEFF Research Database (Denmark)

Sørensen, Carlo Sass; Sørensen, Per; Kroon, Aart

Coastlines around the world are receding due to coastal erosion.With rising sea levels and a potential climatic deterioration due to climate change, erosion rates are likely to increase at many locations in the future.Together with the current preference of people to settle near or directly...... by the ocean, coastal erosion issues become increasingly more important to the human values at risk. Along many Danish coastlines, hard structures already act as coastal protection in the form of groins, breakwaters, revetments etc. These eroding coasts however still lack sand and where the public, in general......, neglects the need for sand replenishment i.e. in the form of repeated sand nourishments. Here we present a conceptual model and method for dividing coastal erosion into acute and chronic erosion pressure, respectively. We focus on the model use for management and climate change adaptation purposes...

Detection of soil erosion within pinyon-juniper woodlands using Thematic Mapper (TM) data

Science.gov (United States)

Price, Kevin P.

1993-01-01

Multispectral measurements collected by Landsat Thematic Mapper (TM) were correlated with field measurements, direct soil loss estimates, and Universal Soil Loss Equation (USLE) estimates to determine the sensitivity of TM data to varying degrees of soil erosion in pinyon-juniper woodland in central Utah. TM data were also evaluated as a predictor of the USLE Crop Management C factor for pinyon-juniper woodlands. TM spectral data were consistently better predictors of soil erosion factors than any combination of field factors. TM data were more sensitive to vegetation variations than the USLE C factor. USLE estimates showed low annual rates of erosion which varied little among the study sites. Direct measurements of rate of soil loss using the SEDIMENT (Soil Erosion DIrect measureMENT) technique, indicated high and varying rates of soil loss among the sites since tree establishment. Erosion estimates from the USLE and SEDIMENT methods suggest that erosion rates have been severe in the past, but because significant amounts of soil have already been eroded, and the surface is now armored by rock debris, present erosion rates are lower. Indicators of accelerated erosion were still present on all sites, however, suggesting that the USLE underestimated erosion within the study area.

Can control of soil erosion mitigate water pollution by sediments?

Science.gov (United States)

Rickson, R J

2014-01-15

The detrimental impact of sediment and associated pollutants on water quality is widely acknowledged, with many watercourses in the UK failing to meet the standard of 'good ecological status'. Catchment sediment budgets show that hill slope erosion processes can be significant sources of waterborne sediment, with rates of erosion likely to increase given predicted future weather patterns. However, linking on-site erosion rates with off-site impacts is complicated because of the limited data on soil erosion rates in the UK and the dynamic nature of the source-pathway-receptor continuum over space and time. Even so, soil erosion control measures are designed to reduce sediment production (source) and mobilisation/transport (pathway) on hill slopes, with consequent mitigation of pollution incidents in watercourses (receptors). The purpose of this paper is to review the scientific evidence of the effectiveness of erosion control measures used in the UK to reduce sediment loads of hill slope origin in watercourses. Although over 73 soil erosion mitigation measures have been identified from the literature, empirical data on erosion control effectiveness are limited. Baseline comparisons for the 18 measures where data do exist reveal erosion control effectiveness is highly variable over time and between study locations. Given the limitations of the evidence base in terms of geographical coverage and duration of monitoring, performance of the different measures cannot be extrapolated to other areas. This uncertainty in effectiveness has implications for implementing erosion/sediment risk reduction policies, where quantified targets are stipulated, as is the case in the EU Freshwater Fish and draft Soil Framework Directives. Also, demonstrating technical effectiveness of erosion control measures alone will not encourage uptake by land managers: quantifying the costs and benefits of adopting erosion mitigation is equally important, but these are uncertain and difficult to

A "1"3"7Cs erosion model with moving boundary

International Nuclear Information System (INIS)

Yin, Chuan; Ji, Hongbing

2015-01-01

A novel quantitative model of the relationship between diffused concentration changes and erosion rates using assessment of soil losses was developed. It derived from the analysis of surface soil "1"3"7Cs flux variation under persistent erosion effect and based on the principle of geochemistry kinetics moving boundary. The new moving boundary model improves the basic simplified transport model (Zhang et al., 2008), and mainly applies to uniform rainfall areas which show a long-time soil erosion. The simulation results for this kind of erosion show under a long-time soil erosion, the influence of "1"3"7Cs concentration will decrease exponentially with increasing depth. Using the new model fit to the measured "1"3"7Cs depth distribution data in Zunyi site, Guizhou Province, China which has typical uniform rainfall provided a good fit with R"2 = 0.92. To compare the soil erosion rates calculated by the simple transport model and the new model, we take the Kaixian reference profile as example. The soil losses estimated by the previous simplified transport model are greater than those estimated by the new moving boundary model, which is consistent with our expectations. - Highlights: • The diffused moving boundary principle analysing "1"3"7Cs flux variation. • The new erosion model applies to uniform rainfall areas. • The erosion effect on "1"3"7Cs will decrease exponentially with increasing depth. • The new model provides two methods of calculating erosion rate.

Nozzle erosion characterization and minimization for high-pressure rocket motor applications

Science.gov (United States)

Evans, Brian

Understanding of the processes that cause nozzle throat erosion and developing methods for mitigation of erosion rate can allow higher operating pressures for advanced rocket motors. However, erosion of the nozzle throat region, which is a strong function of operating pressure, must be controlled to realize the performance gains of higher operating pressures. The objective of this work was the study the nozzle erosion rates at a broad range of pressures from 7 to 34.5 MPa (1,000 to 5,000 psia) using two different rocket motors. The first is an instrumented solidpropellant motor (ISPM), which uses two baseline solid propellants; one is a non-metallized propellant called Propellant S and the other is a metallized propellant called Propellant M. The second test rig is a non-metallized solid-propellant rocket motor simulator (RMS). The RMS is a gas rocket with the ability to vary the combustion-product species composition by systematically varying the flow rates of gaseous reactants. Several reactant mixtures were utilized in the study to determine the relative importance of different oxidizing species (such as H2O, OH, and CO2). Both test rigs are equipped with a windowed nozzle section for real-time X-ray radiography diagnostics of the instantaneous throat variations for deducing the instantaneous erosion rates. The nozzle test section for both motors can also incorporate a nozzle boundary-layer control system (NBLCS) as a means of nozzle erosion mitigation. The effectiveness of the NBLCS at preventing nozzle throat erosion was demonstrated for both the RMS and the ISPM motors at chamber pressures up to 34 MPa (4930 psia). All tests conducted with the NBLCS showed signs of coning of the propellant surface, leading to increased mass burning rate and resultant chamber pressure. Two correlations were developed for the nozzle erosion rates from solid propellant testing, one for metallized propellant and one for non-metallized propellants. The non-metallized propellant

Effect of flow velocity on erosion-corrosion behaviour of QSn6 alloy

Science.gov (United States)

Huang, Weijiu; Zhou, Yongtao; Wang, Zhenguo; Li, Zhijun; Zheng, Ziqing

2018-05-01

The erosion-corrosion behaviour of QSn6 alloy used as propellers in marine environment was evaluated by erosion-corrosion experiments with/without cathodic protection, electrochemical tests and scanning electron microscope (SEM) observations. The analysis was focused on the effect of flow velocity. The dynamic polarization curves showed that the corrosion rate of the QSn6 alloy increased as the flow velocity increased, due to the protective surface film removal at higher velocities. The lowest corrosion current densities of 1.26 × 10‑4 A cm‑2 was obtained at the flow velocity of 7 m s‑1. Because of the higher particle kinetic energies at higher flow velocity, the mass loss rate of the QSn6 alloy increased as the flow velocity increased. The mass loss rate with cathodic protection was lower than that without cathodic protection under the same conditions. Also, the lowest mass loss rate of 0.7 g m‑2 · h‑1 was acquired at the flow velocity of 7 m s‑1 with cathodic protection. However, the increase rate of corrosion rate and mass loss were decreased with increasing the flow velocity. Through observation the SEM morphologies of the worn surfaces, the main wear mechanism was ploughing with/without cathodic protection. The removal rates of the QSn6 alloy increased as the flow velocity increased in both pure erosion and erosion-corrosion, whereas the erosion and corrosion intensified each other. At the flow velocity of 7 m s‑1, the synergy rate (ΔW) exceeded by 5 times the erosion rate (Wwear). Through establishment and observation the erosion-corrosion mechanism map, the erosion-corrosion was the dominant regime in the study due to the contribution of erosion on the mass loss rate exceeded the corrosion contribution. The QSn6 alloy with cathodic protection is feasible as propellers, there are higher security at lower flow velocity, such as the flow velocity of 7 m s‑1 in the paper.

Potential for erosion corrosion of SRS high level waste tanks

International Nuclear Information System (INIS)

Zapp, P.E.

1994-01-01

SRS high-level radioactive waste tanks will not experience erosion corrosion to any significant degree during slurry pump operations. Erosion corrosion in carbon steel structures at reported pump discharge velocities is dominated by electrochemical (corrosion) processes. Interruption of those processes, as by the addition of corrosion inhibitors, sharply reduces the rate of metal loss from erosion corrosion. The well-inhibited SRS waste tanks have a near-zero general corrosion rate, and therefore will be essentially immune to erosion corrosion. The experimental data on carbon steel erosion corrosion most relevant to SRS operations was obtained at the Hanford Site on simulated Purex waste. A metal loss rate of 2.4 mils per year was measured at a temperature of 102 C and a slurry velocity comparable to calculated SRS slurry velocities on ground specimens of the same carbon steel used in SRS waste tanks. Based on these data and the much lower expected temperatures, the metal loss rate of SRS tanks under waste removal and processing conditions should be insignificant, i.e. less than 1 mil per year

Identification of soil erosion risk areas for conservation planning in different states of India.

Science.gov (United States)

Sharda, V N; Mandal, Debashis; Ojasvi, P R

2013-03-01

Assessment of soil erosion risks, especially in the developing countries, is a challenging task mainly due to non-availability or insufficiency of relevant data. In this paper, the soil erosion risks have been estimated by integrating the spatial data on potential erosion rates and soil loss tolerance limits for conservation planning at state level in India. The erosion risk classes have been prioritized based upon the difference between the prevailing erosion rates and the permissible erosion limits. The analysis revealed that about 50% of total geographical area (TGA) of India, falling in five priority erosion risk classes, requires different intensity of conservation measures though about 91% area suffers from potential erosion rates varying from 40 t ha(-1) yr(-1). Statewise analysis indicated that Andhra Pradesh, Maharashtra and Rajasthan share about 75% of total area under priority Class 1 (6.4 M ha) though they account for only 19.4% of the total area (36.2 M ha) under very severe potential erosion rate category (> 40 t ha(-1)yr(-1)). It was observed that about 75% of total geographical area (TGA) in the states of Bihar, Gujarat, Haryana, Kerala and Punjab does not require any specific soil conservation measure as the potential erosion rates are well within the tolerance limits. The developed methodology can be successfully employed for prioritization of erosion risk areas at watershed, region or country level.

Effect of hard second-phase particles on the erosion resistance of model alloys

International Nuclear Information System (INIS)

Kosel, T.H.; Aptekar, S.S.

1986-01-01

The dependence of erosion rate on second phase volume fraction (SPVF) has been studied for Cu/Al/sub 2/O/sub 3/ and Cu/WC(W/sub 2/C) model alloys produced by pressing and sintering. The intention was to investigate the reasons for the poor contribution to erosion resistance made by large hard second phase particles (SPP) in other studies. The results show that for Cu/Al/sub 2/O/sub 3/ alloys, the erosion rate generally increased with SPVF, demonstrating a negative contribution to erosion resistance. This occurred despite the fact that the measured erosion rate of monolithic Al/sub 2/O/sub 3/ was lower by one to two orders of magnitude than that of the pure matrix. Changing from severe erosion with large erodent particles at high velocity to mild conditions with small erodent at low velocity caused a change from depression of the SPPs to protrusion from the surface, with some improvement of the relative erosion resistance compared to the pure matrix. For Cu/WC(W/sub 2/C) alloys, changing from severe to mild erosion conditions caused a change from an increase of erosion with SPVF to a decrease. The results are discussed in terms of the increased microfracture of the unsupported edges of the second phase particles compared to a flat single-phase surface. This edge is consistent with the results, and explains observations not predicted by existing theories for erosion of single-phase materials. A model is introduced which predicts a new averaging law for the erosion rate of a two-phase alloy in terms of erosion rates of its constituent phases

Soil erosion in a man-made landscape: the Mediterranean

Science.gov (United States)

Cerdà, A.; Ruiz Sinoga, J. D.; Cammeraat, L. H.

2012-04-01

Mediterranean-type ecosystems are characterised by a seasonally contrasted distribution of precipitation, by the coincidence of the driest and hottest season in summer, by an often-mountainous terrain, and by a long history of intense human occupation, especially around the Mediterranean Sea. The history of the Mediterranean lands is the history of human impacts on the soil system, and soil erosion is the most intense and widespread impact on this land where high intensity and uneven rainfall is found. A review of the soil erosion rates measured in the Mediterranean basin will be shown. The measurements done by means of erosion pins, topographical measurements, rainfall simulators, Gerlach collectors in open or close plots, watershed/basin measurements, reservoirs siltation and historical data will be shown. A review of the soil erosion models applied in the Mediterranean will be shown. The tentative approach done until October 2011 show that the soil erosion rates on Mediterranean type ecosystems are not as high as was supposed by the pioneers in the 70's. And this is probably due to the fact that the soils are very shallow and sediments are not available after millennia of high erosion rates. This is related to the large amount of rock fragments are covering the soil, and the rock outcrops that are found in the upper slope trams and the summits. Soil erosion in the Mediterranean is seasonal due to the rainfall concentration in winter, and highly variable within years as the high intensity rainfall events control the sediment production. Natural vegetation is adapted to the Mediterranean environmental conditions, and they are efficient to control the soil losses. An example are the forest fire that increase the soil losses but this is a temporal change as after 2-4 years the soil erosion rates are similar to the pre-fire period. Agriculture lands are the source of sediments although the highest erosion rates are found in badland areas that cover a small part of

Solid Particle Erosion of Date Palm Leaf Fiber Reinforced Polyvinyl Alcohol Composites

Directory of Open Access Journals (Sweden)

Jyoti R. Mohanty

2014-01-01

Full Text Available Solid particle erosion behavior of short date palm leaf (DPL fiber reinforced polyvinyl alcohol (PVA composite has been studied using silica sand particles (200 ± 50 μm as an erodent at different impingement angles (15–90° and impact velocities (48–109 m/s. The influence of fiber content (wt% of DPL fiber on erosion rate of PVA/DPL composite has also been investigated. The neat PVA shows maximum erosion rate at 30° impingement angle whereas PVA/DPL composites exhibit maximum erosion rate at 45° impingement angle irrespective of fiber loading showing semiductile behavior. The erosion efficiency of PVA and its composites varies from 0.735 to 16.289% for different impact velocities studied. The eroded surfaces were observed under scanning electron microscope (SEM to understand the erosion mechanism.

Evaluation of gross radioactivity in foodstuffs

International Nuclear Information System (INIS)

Zorer, Oezlem Selcuk; Oeter, Cigdem

2015-01-01

The paper presents the results of radiological investigations of food products sampled in the summer and fall of 2011 and 2012 in different parts of Van, Turkey. Gross radioactivity measurements in food products were evaluated. Food items were divided into eight groups: (1) water, (2) fish, (3) cheese products, (4) fruits, (5) vegetables, (6) herbs, (7) walnut and (8) rock salt. The levels of the gross alpha and gross beta radioactivity in all food samples varied widely ranging from 0.070 to 10.885 Bq/g and from 0.132 to 48.285 Bq/g on dry mass basis, respectively. In one sample, gross alpha and gross beta activity concentrations were found to be relatively high according to the other samples and in all samples, the gross alpha radioactivity was measured lower than the gross beta radioactivity. The gross α and gross β activities were measured by using α/β counter of the multi-detector low background system (PIC MPC-9604).

Evaluation of gross radioactivity in foodstuffs

Energy Technology Data Exchange (ETDEWEB)

Zorer, Oezlem Selcuk; Oeter, Cigdem [Yuzuncu Yil Univ., Van (Turkey). Dept. of Chemistry

2015-05-15

The paper presents the results of radiological investigations of food products sampled in the summer and fall of 2011 and 2012 in different parts of Van, Turkey. Gross radioactivity measurements in food products were evaluated. Food items were divided into eight groups: (1) water, (2) fish, (3) cheese products, (4) fruits, (5) vegetables, (6) herbs, (7) walnut and (8) rock salt. The levels of the gross alpha and gross beta radioactivity in all food samples varied widely ranging from 0.070 to 10.885 Bq/g and from 0.132 to 48.285 Bq/g on dry mass basis, respectively. In one sample, gross alpha and gross beta activity concentrations were found to be relatively high according to the other samples and in all samples, the gross alpha radioactivity was measured lower than the gross beta radioactivity. The gross α and gross β activities were measured by using α/β counter of the multi-detector low background system (PIC MPC-9604).

Cavitation erosion - scale effect and model investigations

Science.gov (United States)

Geiger, F.; Rutschmann, P.

2015-12-01

The experimental works presented in here contribute to the clarification of erosive effects of hydrodynamic cavitation. Comprehensive cavitation erosion test series were conducted for transient cloud cavitation in the shear layer of prismatic bodies. The erosion pattern and erosion rates were determined with a mineral based volume loss technique and with a metal based pit count system competitively. The results clarified the underlying scale effects and revealed a strong non-linear material dependency, which indicated significantly different damage processes for both material types. Furthermore, the size and dynamics of the cavitation clouds have been assessed by optical detection. The fluctuations of the cloud sizes showed a maximum value for those cavitation numbers related to maximum erosive aggressiveness. The finding suggests the suitability of a model approach which relates the erosion process to cavitation cloud dynamics. An enhanced experimental setup is projected to further clarify these issues.

Estimation and Forecasting the Gross Domestic Product´s Growth Rate in Ecuador: a Short-term Vision

Directory of Open Access Journals (Sweden)

Yadier Alberto Torres−Sánchez

2016-12-01

Full Text Available Ecuador is the seventh largest economy in Latin America. From 2000 to 2012, the country has been expanding at an average rate of 1,15 % on a quarter over quarter basis, mostly due to a rise in exports. Ecuador´s economy is highly dependent on oil exports. In order to reach its full growth potential, the country needs to reduce its dependence on oil revenue; increase the tax base; achieve political stability and reduce the levels of poverty and inequality. The main objective of this research is specifically marked in estimate and forecast the Gross Domestic Product´s Growth Rate in Ecuador, applying for this Box – Jenkins´ Methodology for ARIMA models. It was obtained a forecast of 3,96 % approximately, that represents a logical result according with the time series.

Estimation and Forecasting the Gross Domestic Product´s Growth Rate in Ecuador: a Short-term Vision

Directory of Open Access Journals (Sweden)

Yadier Alberto Torres−Sánchez

2017-01-01

Full Text Available Ecuador is the seventh largest economy in Latin America. From 2000 to 2012, the country has been expanding at an average rate of 1,15 % on a quarter over quarter basis, mostly due to a rise in exports. Ecuador´s economy is highly dependent on oil exports. In order to reach its full growth potential, the country needs to reduce its dependence on oil revenue; increase the tax base; achieve political stability and reduce the levels of poverty and inequality. The main objective of this research is specifically marked in estimate and forecast the Gross Domestic Product´s Growth Rate in Ecuador, applying for this Box – Jenkins´ Methodology for ARIMA models. It was obtained a forecast of 3,96 % approximately, that represents a logical result according with the time series.

Thermal erosion of a permafrost coastline: Improving process-based models using time-lapse photography

Science.gov (United States)

Wobus, C.; Anderson, R.; Overeem, I.; Matell, N.; Clow, G.; Urban, F.

2011-01-01

Coastal erosion rates locally exceeding 30 m y-1 have been documented along Alaska's Beaufort Sea coastline, and a number of studies suggest that these erosion rates have accelerated as a result of climate change. However, a lack of direct observational evidence has limited our progress in quantifying the specific processes that connect climate change to coastal erosion rates in the Arctic. In particular, while longer ice-free periods are likely to lead to both warmer surface waters and longer fetch, the relative roles of thermal and mechanical (wave) erosion in driving coastal retreat have not been comprehensively quantified. We focus on a permafrost coastline in the northern National Petroleum Reserve-Alaska (NPR-A), where coastal erosion rates have averaged 10-15 m y-1 over two years of direct monitoring. We take advantage of these extraordinary rates of coastal erosion to observe and quantify coastal erosion directly via time-lapse photography in combination with meteorological observations. Our observations indicate that the erosion of these bluffs is largely thermally driven, but that surface winds play a crucial role in exposing the frozen bluffs to the radiatively warmed seawater that drives melting of interstitial ice. To first order, erosion in this setting can be modeled using formulations developed to describe iceberg deterioration in the open ocean. These simple models provide a conceptual framework for evaluating how climate-induced changes in thermal and wave energy might influence future erosion rates in this setting.

Requirement of radiochemical recovery determination for gross alpha and gross beta estimation in drinking water

International Nuclear Information System (INIS)

Raveendran, Nanda; Rao, D.D.; Hegde, A.G.

2010-01-01

Presence of radionuclides in drinking water which emits Alpha and Beta particles are the potential sources of internal exposure in drinking water. Gross alpha and gross beta determination in drinking water and packaged drinking water (PDW) as per BIS (Bureau of Indian standards) standards is discussed here. The methods have been tested to account for losses in the radiochemical procedures using radionuclides such as 137 Cs, 90 Sr, 226 Ra, 239 Pu, 243 Am, 232 U. The methods have also been validated in an IAEA proficiency test conducted during 2009. Monitoring of gross alpha and gross beta activity observed in drinking water/packaged drinking water from various states of India were within the limits set by BIS. Average radiochemical recoveries of 84% and 63% were obtained for gross α and gross β respectively. (author)

Designing a national soil erosion monitoring network for England and Wales

Science.gov (United States)

Lark, Murray; Rawlins, Barry; Anderson, Karen; Evans, Martin; Farrow, Luke; Glendell, Miriam; James, Mike; Rickson, Jane; Quine, Timothy; Quinton, John; Brazier, Richard

2014-05-01

Although soil erosion is recognised as a significant threat to sustainable land use and may be a priority for action in any forthcoming EU Soil Framework Directive, those responsible for setting national policy with respect to erosion are constrained by a lack of robust, representative, data at large spatial scales. This reflects the process-orientated nature of much soil erosion research. Recognising this limitation, The UK Department for Environment, Food and Rural Affairs (Defra) established a project to pilot a cost-effective framework for monitoring of soil erosion in England and Wales (E&W). The pilot will compare different soil erosion monitoring methods at a site scale and provide statistical information for the final design of the full national monitoring network that will: provide unbiased estimates of the spatial mean of soil erosion rate across E&W (tonnes ha-1 yr-1) for each of three land-use classes - arable and horticultural grassland upland and semi-natural habitats quantify the uncertainty of these estimates with confidence intervals. Probability (design-based) sampling provides most efficient unbiased estimates of spatial means. In this study, a 16 hectare area (a square of 400 x 400 m) positioned at the centre of a 1-km grid cell, selected at random from mapped land use across E&W, provided the sampling support for measurement of erosion rates, with at least 94% of the support area corresponding to the target land use classes. Very small or zero erosion rates likely to be encountered at many sites reduce the sampling efficiency and make it difficult to compare different methods of soil erosion monitoring. Therefore, to increase the proportion of samples with larger erosion rates without biasing our estimates, we increased the inclusion probability density in areas where the erosion rate is likely to be large by using stratified random sampling. First, each sampling domain (land use class in E&W) was divided into strata; e.g. two sub

Electrode erosion in arc discharges at atmospheric pressure

Science.gov (United States)

Hardy, T. L.

1985-01-01

An experimental investigation was performed in an effort to measure and increase lifetime of electrodes in an arcjet thruster. The electrode erosion of various anode and cathode materials was measured after tests in an atmospheric pressure nitrogen arc discharge at powers less than 1 kW. A free-burning arc configuration and a constricted arc configuration were used to test the materials. Lanthanum hexboride and thoriated tungsten had low cathode erosion rates while thoriated tungsten and pure tungsten had the lowest anode erosion rates of the materials tested. Anode cooling, reverse gas flow, an external magnetic fields were all found to reduce electrode mass loss.

A comparison of methods in estimating soil water erosion

Directory of Open Access Journals (Sweden)

Marisela Pando Moreno

2012-02-01

Full Text Available A comparison between direct field measurements and predictions of soil water erosion using two variant; (FAO and R/2 index of the Revised Universal Soil Loss Equation (RUSLE was carried out in a microcatchment o 22.32 km2 in Northeastern Mexico. Direct field measurements were based on a geomorphologic classification of the area; while environmental units were defined for applying the equation. Environmental units were later grouped withir geomorphologic units to compare results. For the basin as a whole, erosion rates from FAO index were statistical!; equal to those measured on the field, while values obtained from the R/2 index were statistically different from the res and overestimated erosion. However, when comparing among geomorphologic units, erosion appeared overestimate! in steep units and underestimated in more flat areas. The most remarkable differences on erosion rates, between th( direct and FAO methods, were for those units where gullies have developed, fn these cases, erosion was underestimated by FAO index. Hence, it is suggested that a weighted factor for presence of gullies should be developed and included in RUSLE equation.

Protection of uranium tailings impoundments against overland erosion

International Nuclear Information System (INIS)

Walters, W.H.; Skaggs, R.L.

1986-01-01

This study investigates the problems involved in designing protection methods to prevent erosion of a uranium tailings impoundment cover from rainfall and runoff (overland flow) processes. The study addresses the side slopes and top surface as separate elements. The side slopes are more subject to gully erosion and require absolute protection such as that provided by rock riprap. The flatter top surface needs much less protection (vegetation/rock combinations) but some estimate of erosion rates are needed to compare alternatives. A literature review indicated that, currently, procedures are not available for the design of rock riprap to prevent gully erosion. Therefore, rock protection on the side slope will have to be based upon engineering judgment determined by the particular site conditions. The Manning-kinetic equations (velocity and depth of runoff) were investigated as a possible aid to the design of gully erosion protection. Guidelines are suggested for the use of rock riprap to prevent gully erosion. Three mathematical models were used to compute erosion rates for the top surface of a hypothetical tailings impoundment. The results recommend that one or possibly both of the regression models could be used to evaluate preliminary protection designs for the top surface. A physical process simulation model should be used for the final design. 30 refs., 13 figs., 16 tabs

The Arctic Coastal Erosion Problem

Energy Technology Data Exchange (ETDEWEB)

Frederick, Jennifer M. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Thomas, Matthew Anthony [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Bull, Diana L. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Jones, Craig A. [Integral Consulting Inc., San Francisco, CA (United States); Roberts, Jesse D. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

2016-09-01

Permafrost-dominated coastlines in the Arctic are rapidly disappearing. Arctic coastal erosion rates in the United States have doubled since the middle of the twentieth century and appear to be accelerating. Positive erosion trends have been observed for highly-variable geomorphic conditions across the entire Arctic, suggesting a major (human-timescale) shift in coastal landscape evolution. Unfortunately, irreversible coastal land loss in this region poses a threat to native, industrial, scientific, and military communities. The Arctic coastline is vast, spanning more than 100,000 km across eight nations, ten percent of which is overseen by the United States. Much of area is inaccessible by all-season roads. People and infrastructure, therefore, are commonly located near the coast. The impact of the Arctic coastal erosion problem is widespread. Homes are being lost. Residents are being dispersed and their villages relocated. Shoreline fuel storage and delivery systems are at greater risk. The U.S. Department of Energy (DOE) and Sandia National Laboratories (SNL) operate research facilities along some of the most rapidly eroding sections of coast in the world. The U.S. Department of Defense (DOD) is struggling to fortify coastal radar sites, operated to ensure national sovereignty in the air, against the erosion problem. Rapid alterations to the Arctic coastline are facilitated by oceanographic and geomorphic perturbations associated with climate change. Sea ice extent is declining, sea level is rising, sea water temperature is increasing, and permafrost state is changing. The polar orientation of the Arctic exacerbates the magnitude and rate of the environmental forcings that facilitate coastal land area loss. The fundamental mechanics of these processes are understood; their non-linear combination poses an extreme hazard. Tools to accurately predict Arctic coastal erosion do not exist. To obtain an accurate predictive model, a coupling of the influences of

Using REE tracers to measure sheet erosion changing to rill erosion

International Nuclear Information System (INIS)

Liu Puling; Xue Yazhou; Song Wei; Wang Mingyi; Ju Tongjun

2004-01-01

Rare Earth Elements (REE) tracer method was used to study sheet erosion changing to rill erosion on slope land. By placing different rare earth elements of different soil depth across a slope in an indoor plot, two simulated rainfalls were applied to study the change of erosion type and the rill erosion process. The results indicate that the main erosion type is sheet erosion at the beginning of the rainfalls, and serious erosion happens after rill erosion appears. Accumulated sheet and rill erosion amounts increase with the rainfalls time. The percentage of sheet erosion amount decreases and rill erosion percentage increases with time. At the end of the rainfalls, the total rill erosion amounts are 4-5 times more than sheet erosion. In this paper, a new REE tracer method was used to quantitatively distinguish sheet and rill erosion amounts. The new REE tracer method should be useful to future studying of erosion processes on slope lands. (authors)

Estimates of soil erosion using cesium-137 tracer models.

Science.gov (United States)

Saç, M M; Uğur, A; Yener, G; Ozden, B

2008-01-01

The soil erosion was studied by 137Cs technique in Yatagan basin in Western Turkey, where there exist intensive agricultural activities. This region is subject to serious soil loss problems and yet there is not any erosion data towards soil management and control guidelines. During the soil survey studies, the soil profiles were examined carefully to select the reference points. The soil samples were collected from the slope facets in three different study areas (Kirtas, Peynirli and Kayisalan Hills). Three different models were applied for erosion rate calculations in undisturbed and cultivated sites. The profile distribution model (PDM) was used for undisturbed soils, while proportional model (PM) and simplified mass balance model (SMBM) were used for cultivated soils. The mean annual erosion rates found using PDM in undisturbed soils were 15 t ha(-1) year(-1) at the Peynirli Hill and 27 t ha(-1) year(-1) at the Kirtas Hill. With the PM and SMBM in cultivated soils at Kayişalan, the mean annual erosion rates were obtained to be 65 and 116 t ha(-1) year(-1), respectively. The results of 137Cs technique were compared with the results of the Universal Soil Loss Equation (USLE).

Use of Magnetic Parameters to Asses Soil Erosion Rates on Agricultural Site

Science.gov (United States)

Petrovsky, E.; Kapicka, A.; Dlouha, S.; Jaksik, O.; Grison, H.; Kodesova, R.

2014-12-01

A detailed field study on a small test site of agricultural land situated in loess region in Southern Moravia (Czech Republic) and laboratory analyses were carried out in order to test the applicability of magnetic methods in assessing soil erosion. Haplic Chernozem, the original dominant soil unit in the area, is nowadays progressively transformed into different soil units along with intense soil erosion. As a result, an extremely diversified soil cover structure has developed due to the erosion. The site was characterized by a flat upper part while the middle part, formed by a substantive side valley, is steeper. We carried out field measurements of magnetic susceptibility on a regular grid, resulting in 101 data points. The bulk soil material for laboratory investigation was gathered from all the grid points. Values of the magnetic susceptibility are spatially distributed depending on the terrain. Higher values were measured in the flat upper part (where the original top horizon remained). The lowest values of were obtained on the steep valley sides. Here the original topsoil was eroded and mixed by tillage with the soil substrate (loess). A soil profile unaffected by erosion was investigated in detail. The vertical distribution of magnetic susceptibility along this "virgin" profile was measured in laboratory on the samples collected with 2-cm spacing. The undisturbed profile shows several soil horizons. Horizons Ac and A show a slight increase in magnetic susceptibility up to a depth of about 70 cm. Horizon A/Ck is characterized by a decrease in susceptibility, and the underlying C horizon (h > 103 cm) has a very low value of magnetic susceptibility. The differences between the values of susceptibility in the undisturbed soil profile and the magnetic signal after uniform mixing the soil material as a result of tillage and erosion are fundamental for the estimation of soil loss in the studied test field. Using the uneroded profile from the studied locality as a

75 FR 9257 - SBA Lender Risk Rating System

Science.gov (United States)

2010-03-01

... Liquidation Rate; 3. Gross Delinquency Rate; 4. Gross Past-Due Rate; 5. Six (6) Month Net Flow Indicator; 6.... The statistical analysis performed showed that incorporating the Portfolio Size/Age component improved...) Month Delinquency Rate; 3. Gross Delinquency Rate; 4. Gross Past-Due Rate; 5. Average Small Business...

CFD Based Erosion Modelling of Abrasive Waterjet Nozzle using Discrete Phase Method

International Nuclear Information System (INIS)

Kamarudin, Naqib Hakim; Prasada Rao, A K; Azhari, Azmir

2016-01-01

In Abrasive Waterjet (AWJ) machining, the nozzle is the most critical component that influences the performance, precision and economy. Exposure to a high speed jet and abrasives makes it susceptible to wear erosion which requires for frequent replacement. The present works attempts to simulate the erosion of the nozzle wall using computational fluid dynamics. The erosion rate of the nozzle was simulated under different operating conditions. The simulation was carried out in several steps which is flow modelling, particle tracking and erosion rate calculation. Discrete Phase Method (DPM) and K-ε turbulence model was used for the simulation. Result shows that different operating conditions affect the erosion rate as well as the flow interaction of water, air and abrasives. The simulation results correlates well with past work. (paper)

Monitoring of gross alpha, gross beta and tritium activities in portuguese drinking waters

International Nuclear Information System (INIS)

Lopes, I.; Madruga, M.J.; Ferrador, G.O.; Sequeira, M.M.; Oliveira, E.J.; Gomes, A.R.; Rodrigues, F.D.; Carvalho, F.P.

2006-01-01

The gross beta and tritium activities in the forty Portuguese drinking waters analyzed using the ISO standard methods (Portuguese Guidelines) are below the guidance levels proposed in the Portuguese Drinking Water Quality Guidelines. In what concerns the gross alpha activity only 18% exceeded the recommended level. In general, it can be concluded that the ingestion of these drinking waters does not create a radiological hazard to the human consumption, however, more detailed analyses will be necessary mainly the determinations of the individual alpha emitters radionuclide concentrations. The minimum gross alpha and gross beta detectable activities by L.S.C. methodology are higher than for the proportional counting technique (ISO method). Higher concentration factors will be needed to reach lower required detection limits. (authors)

CFD evaluation of erosion rate around a bridge near a sand dune

Science.gov (United States)

He, Wei; Huang, Ning; Dun, Hongchao; Wang, Wenbo

2017-04-01

This study performs a series of simulations through solving the Navier-Stokes equations and the RNG k-ε turbulence model to investigate the wind erosion rates around a bridge in a desert area with sand dunes. The digital elevation model of sand dunes and the bridge model are obtained respectively from hypsographic map and construction drawings. Through combining them into the CFD software of Fluent the simulation zone was formed. The data of wind speed obtained from field observation is fitted into a logarithm format, which was imported into Fluent model as a inlet wind speed condition. Then, the effect of Dun-Go railway on wind-blown sand movement of the neighbouring environment is simulated. The results exhibit that affected by both the sand dune and bridge, the flow field is in a complex condition. It is also shown that the bridge in upstream of the sand dune will not increase the sand transport rate intensively, but change both wind velocity gradient and turbulence kinetic energy over surface of sand dune. On the other hand, when the bridge is built downstream the sand dune, simulation results show that sand deposition rate would be decreased in reference region downstream the pier.

Erosion testing of hard materials and coatings

Energy Technology Data Exchange (ETDEWEB)

Hawk, Jeffrey A.

2005-04-29

Erosion is the process by which unconstrained particles, usually hard, impact a surface, creating damage that leads to material removal and component failure. These particles are usually very small and entrained in fluid of some type, typically air. The damage that occurs as a result of erosion depends on the size of the particles, their physical characteristics, the velocity of the particle/fluid stream, and their angle of impact on the surface of interest. This talk will discuss the basics of jet erosion testing of hard materials, composites and coatings. The standard test methods will be discussed as well as alternative approaches to determining the erosion rate of materials. The damage that occurs will be characterized in genera1 terms, and examples will be presented for the erosion behavior of hard materials and coatings (both thick and thin).

Numerical study of impact erosion of multiple solid particle

Science.gov (United States)

Zheng, Chao; Liu, Yonghong; Chen, Cheng; Qin, Jie; Ji, Renjie; Cai, Baoping

2017-11-01

Material erosion caused by continuous particle impingement during hydraulic fracturing results in significant economic loss and increased production risks. The erosion process is complex and has not been clearly explained through physical experiments. To address this problem, a multiple particle model in a 3D configuration was proposed to investigate the dynamic erosion process. This approach can significantly reduce experiment costs. The numerical model considered material damping and elastic-plastic material behavior of target material. The effects of impact parameters on erosion characteristics, such as plastic deformation, contact time, and energy loss rate, were investigated. Based on comprehensive studies, the dynamic erosion mechanism and geometry evolution of eroded crater was obtained. These findings can provide a detailed erosion process of target material and insights into the material erosion caused by multiple particle impingement.

Using Cesium-137 technique to study the characteristics of different aspect of soil erosion in the Wind-water Erosion Crisscross Region on Loess Plateau of China

International Nuclear Information System (INIS)

Li Mian; Li Zhanbin; Liu Puling; Yao Wenyi

2005-01-01

The most serious soil erosion on Loess Plateau exists in the Wind-water Erosion Crisscross Region. In the past 20 years, the types and intensity of soil erosion and its temporal and spatial distribution were studied, but studies on the difference of soil erosion between slope aspects and slope positions in this area have no report. However, it is very important to analyze and evaluate quantitatively the characteristics of different aspects and positions of soil loss for the prevention and treatment of soil erosion in this area. The spatial pattern of net soil loss on 4 downslope transects in four aspects (east, west, south and north) on a typical Mao (round loess mound) in Liudaogou catchment in Wind-water Erosion Crisscross Region was measured in 2000 using the resident cesium-137 deficit technique. The purposes of this investigation were undertaken to determine whether or not 137 Cs measurement would give a useful indication of the extent of soil loss and their characteristics from cultivated hillsides in different slope aspect and slope position in the study area. The results showed that the difference of soil erosion in different aspect was significant and the erosion rate was in this order: north>east>south>west. Compared with other areas, the difference of erosion rate between north hillside and south hillside was on the contrary, and the possible explanations could be the effect of wind erosion. Also, the percentage of wind erosion was estimated to be at least larger than 18% of total soil loss by comparing the difference of erosion amount in south hillside and north hillside. The erosion rates on different slope positions in all aspects were also different, the highest net soil loss occurred in the lower slope position, and the upper and middle slope positions were slight. The general trend of net soil loss on sloping surface was to increase in fluctuation with increasing downslope distance

Using Cesium-137 technique to study the characteristics of different aspect of soil erosion in the Wind-water Erosion Crisscross Region on Loess Plateau of China

Energy Technology Data Exchange (ETDEWEB)

Li Mian E-mail: hnli-mian@163.com; Li Zhanbin; Liu Puling; Yao Wenyi

2005-01-01

The most serious soil erosion on Loess Plateau exists in the Wind-water Erosion Crisscross Region. In the past 20 years, the types and intensity of soil erosion and its temporal and spatial distribution were studied, but studies on the difference of soil erosion between slope aspects and slope positions in this area have no report. However, it is very important to analyze and evaluate quantitatively the characteristics of different aspects and positions of soil loss for the prevention and treatment of soil erosion in this area. The spatial pattern of net soil loss on 4 downslope transects in four aspects (east, west, south and north) on a typical Mao (round loess mound) in Liudaogou catchment in Wind-water Erosion Crisscross Region was measured in 2000 using the resident cesium-137 deficit technique. The purposes of this investigation were undertaken to determine whether or not {sup 137}Cs measurement would give a useful indication of the extent of soil loss and their characteristics from cultivated hillsides in different slope aspect and slope position in the study area. The results showed that the difference of soil erosion in different aspect was significant and the erosion rate was in this order: north>east>south>west. Compared with other areas, the difference of erosion rate between north hillside and south hillside was on the contrary, and the possible explanations could be the effect of wind erosion. Also, the percentage of wind erosion was estimated to be at least larger than 18% of total soil loss by comparing the difference of erosion amount in south hillside and north hillside. The erosion rates on different slope positions in all aspects were also different, the highest net soil loss occurred in the lower slope position, and the upper and middle slope positions were slight. The general trend of net soil loss on sloping surface was to increase in fluctuation with increasing downslope distance.

Estimation of inhalation doses from airborne releases using gross monitors

International Nuclear Information System (INIS)

Goldstein, N.P.

1978-01-01

Monitoring programs at most nuclear facilities involve continuous gross measurements supplemented by periodic isotopic analyses of release samples. The isotopic measurements are required to accurately assess the potential dose from the various effluent streams, but in between these measurements, one depends on the gross monitors to provide approximate indications of the dose. The effluent streams release a variety of nuclides, each with its own dose factor. This means that the relationship between the counting rate in a gross monitor and the potential dose of the effluent being monitored will depend on the isotopic composition of this release. If this composition changes, then the dose indicated by the gross monitor (calibrated for the original group of isotopes) may be significantly in error. The problem of indicating inhalation doses from gross monitoring of airborne releases is considered. In order for this type of monitor to accurately indicate dose, regardless of the isotopic makeup of a release, the analysis shows that its response to each isotope should be proportional to the dose factor of that isotope. These ideas are applied to the monitoring of air particulates using gross beta and gross gamma monitors. The study shows that the former more closely satisfies this condition and as a result, satisfactorily indicates the actual dose from reactor effluents, as determined from detailed isotopic data published in the literature. On the other hand, the gross gamma monitor, with its poorer fit to the condition, provided less than satisfactory accuracy in its dose estimates. In addition, a variety of other mathematical response functions were considered but their dose estimation capabilities were not much better than the straight beta response. The study shows that reasonably accurate dose estimates can be made using properly selected gross monitors, but that significant errors can result with improper ones. (author)

The delicate balance between soil production and erosion, and its role on landscape evolution

Energy Technology Data Exchange (ETDEWEB)

Dosseto, A., E-mail: tonyd@uow.edu.au [GeoQuEST Research Centre, School of Earth and Environmental Sciences, University of Wollongong. Wollongong, NSW (Australia); Buss, Heather [US Geological Survey. Menlo Park, CA (United States); Suresh, P.O. [Department of Environment and Geography, Macquarie University. North Ryde, NSW (Australia)

2011-06-15

Highlights: > The uranium-series isotope composition of regolith material can be used to determine the soil residence time. > Soil residence times up to 30 and 90 kyr are calculated for Frogs Hollow and Bisley, respectively. > Production rates are relatively similar for granitic and shale lithologies, but much higher over volcanic parent rock. > Soil production matches erosion in soil-mantled landscapes, demonstrating quantitatively that this type of landscape results from a balance between these two processes > Soil production is up to two orders of magnitude slower than erosion in cultivated areas. - Abstract: The diversity in landscapes at the Earth's surface is the result, amongst other things, of the balance (or imbalance) between soil production and erosion. While erosion rates are well constrained, it is only recently that we have been able to quantify rates of soil production. Uranium-series isotopes have been useful to provide such estimates independently of erosion rates. In this study, new U-series isotope are presented data from weathering profiles developed over andesitic parent rock in Puerto Rico, and granitic bedrock in southeastern Australia. The site in Australia is located on a highland plateau, neighbouring a retreating escarpment where soil production rates between 10 and 50 mm/kyr have been determined. The results show that production rates are invariant in these two regions of Australia with values between 15 and 25 mm/kyr for the new site. Andesitic soils show much faster rates, about 200 mm/kyr. Overall, soil production rates determined with U-series isotopes range between 10 and 200 mm/kyr. This is comparable to erosion rates in soil-mantled landscapes, but faster than erosion in cratonic areas and slower than in alpine regions and cultivated areas. This suggests that soil-mantled landscapes maintain soil because they can: there is a balance between production and erosion. Similarly, thick weathering profiles develop in cratonic areas

Coastal erosion management in Accra: Combining local knowledge and empirical research

Directory of Open Access Journals (Sweden)

Kwasi Appeaning Addo

2016-11-01

Full Text Available Coastal erosion along the Accra coast has become a chronic phenomenon that threatens both life and property. The issue has assumed a centre stage of national debate in recent times because of its impact on the coastal communities. Lack of reliable geospatial data hinders effective scientific investigations into the changing trends in the shoreline position. However, knowledge about coastal erosion, by the local people, and how far the shoreline has migrated inland over time is high in the coastal communities in Accra. This opens a new chapter in coastal erosion research to include local knowledge of the local settlers in developing sustainable coastal management. This article adopted a scientific approach to estimate rate of erosion and tested the results against perceived erosion trend by the local settlers. The study used a 1974 digital topographic map and 1996 aerial photographs. The end point rate statistical method in DSAS was used to compute the rates of change. The short-term rate of change for the 22-year period under study was estimated as -0.91 m/annum ± 0.49 m/annum. It was revealed that about 79% of the shoreline is eroding, while the remaining 21% is either stabilised or accreting. It emerged, from semi-structured interviews with inhabitants in the Accra coastal communities, that an average of about 30 m of coastal lands are perceived to have been lost to erosion for a period of about 20 years. This translates to a historic rate of change of about 1.5 m/year, which corroborates the results of the scientific study. Again this study has established that the local knowledge of the inhabitants, about coastal erosion, can serve as reliable information under scarcity of scientific data for coastal erosion analyses in developing countries.

Erosion and deposition in a field/forest system estimated using cesium-137 activity

International Nuclear Information System (INIS)

Lowrance, R.; McIntyre, S.; Lance, C.

1988-01-01

Soil erosion and deposition were estimated using Cs-137 activity within a 7.25-ha field/forest system in the southeastern coastal plain. Sol eroded from the field was deposited both in the riparian forest ecosystem and in downslope areas of the field. Total activity, depth to peak activity, and depth to zero activity increased downslope from field to stream. Erosion and deposition rates, estimated by changes in activity per unit area from a reference undisturbed forest site, showed that about twice as much total deposition had taken place as total erosion. Excess deposition was attributed to deposition from the upstream portions of the watershed. Erosion and deposition rates estimated with this method were about 63 and 256 Mg/ha/yr, respectively. Erosion and deposition rates estimated by two different calculation techniques were nearly identical. These rates were considerably higher than rates estimated in an earlier study. The rates may be overestimated because the differential rates of Cs-137 movement on clay particles were not considered. The riparian ecosystem acted as a very efficient sediment trap. 19 refs., 5 figs., 3 tabs

Review of erosion dynamics along the major N-S climatic gradient in Chile and perspectives

Science.gov (United States)

Carretier, S.; Tolorza, V.; Regard, V.; Aguilar, G.; Bermúdez, M. A.; Martinod, J.; Guyot, J.-L.; Hérail, G.; Riquelme, R.

2018-01-01

Chile is an elongated country, running in a north-south direction for more than 30° along a subduction zone. Its climate is progressively wetter and colder from north to south. This particular geography has been used positively by a growing number of studies to better understand the relationships between erosion processes and climate, land use, slope, tectonics, volcanism, etc. Here we review the erosion rates, factors, and dynamics over millennial to daily periods reported in the literature. In addition, 21 new catchment mean erosion rates (suspended sediment and 10Be) are provided, and previous suspended sediment-derived erosion rates are updated. A total of 485 local and catchment mean erosion rates are reported. Erosion rates vary between some of the smallest values on earth (10-5 mm/a) to moderate values ≤0.5 mm/a compared to other active ranges. This review highlights strong limitations concerning the quantification of local erosion factors because of uncertainties in sampling point location, slope and rainfall data. For the mean erosion rates E for the millennial and decennial catchments, a model of the form E ∝ S/ [1 - (S/0.6)2] Rα with α = [0.3,0.8] accounts for 40 to 70% of the erosion variance, confirming a primary role of slope S compared to precipitation rate R over this time scale. Over the long-term, this review points to the long (5 to >10 Ma) response time of rivers to surface uplift in north-central arid Chile. Over millennia, data provide evidence for the progressive contribution of extreme erosion events to millennial averages for drier climates, as well as the link between glacier erosion and glacier sliding velocity. In this period of time, a discrepancy exists between the long-term offshore sedimentological record and continental decennial or millennial erosion data, for which no single explanation appears. Still, little information is available concerning the magnitude of variation of millennial erosion rates. Over centuries, data

Soil erosion assessment - Mind the gap

Science.gov (United States)

Kim, Jongho; Ivanov, Valeriy Y.; Fatichi, Simone

2016-12-01

Accurate assessment of erosion rates remains an elusive problem because soil loss is strongly nonunique with respect to the main drivers. In addressing the mechanistic causes of erosion responses, we discriminate between macroscale effects of external factors - long studied and referred to as "geomorphic external variability", and microscale effects, introduced as "geomorphic internal variability." The latter source of erosion variations represents the knowledge gap, an overlooked but vital element of geomorphic response, significantly impacting the low predictability skill of deterministic models at field-catchment scales. This is corroborated with experiments using a comprehensive physical model that dynamically updates the soil mass and particle composition. As complete knowledge of microscale conditions for arbitrary location and time is infeasible, we propose that new predictive frameworks of soil erosion should embed stochastic components in deterministic assessments of external and internal types of geomorphic variability.

Sustainable agriculture, soil management and erosion from prehistoric times to 2100

Science.gov (United States)

Vanwalleghem, Tom; Gómez, Jose Alfonso; Infante Amate, Juan; González Molina, Manuel; Fernández, David Soto; Guzmán, Gema; Vanderlinden, Karl; Laguna, Ana; Giráldez, Juan Vicente

2015-04-01

The rational use of soil requires the selection of management practices to take profit of the beneficial functions of plant growth, water and nutrient storage, and pollutants removal by filtering and decomposition without altering its properties. However, the first evidence of important and widespread erosion peaks can generally be found with the arrival of the first farmers all over the world. In areas with a long land-use history such as the Mediterranean, clear signs indicating the advanced degradation status of the landscape, such as heavily truncated soils, are visible throughout. Soil conservation practices are then aimed at reducing erosion to geological rates, in equilibrium with long-term soil formation rates, while maximizing agricultural production. The adoption of such practices in most areas of the world are as old as the earliest soil erosion episodes themselves. This work firstly reviews historical evidence linking soil management and soil erosion intensity, with examples from N Europe and the Mediterranean. In particular, work by the authors in olive orchards will be presented that shows how significant variations in soil erosion rates between could be linked to the historical soil management. The potential of historical documents for calibrating a soil erosion model is shown as the model, in this case RUSLE-based and combining tillage and water erosion, adequately represents the measured erosion rate dynamics. Secondly, results from present-day, long-term farm experiments in the EU are reviewed to evaluate the effect of different soil management practices on physical soil properties, such as bulk density, penetration resistance, aggregate stability, runoff coefficient or sediment yield. Finally, we reflect upon model and field data that indicate how future global climate change is expected to affect soil management and erosion and how the examples used above hold clues about sustainable historical management practices that can be used successfully

Estimating soil erosion risk and evaluating erosion control measures for soil conservation planning at Koga watershed in the highlands of Ethiopia

Science.gov (United States)

Molla, Tegegne; Sisheber, Biniam

2017-01-01

Soil erosion is one of the major factors affecting sustainability of agricultural production in Ethiopia. The objective of this paper is to estimate soil erosion using the universal soil loss equation (RUSLE) model and to evaluate soil conservation practices in a data-scarce watershed region. For this purpose, soil data, rainfall, erosion control practices, satellite images and topographic maps were collected to determine the RUSLE factors. In addition, measurements of randomly selected soil and water conservation structures were done at three sub-watersheds (Asanat, Debreyakob and Rim). This study was conducted in Koga watershed at upper part of the Blue Nile basin which is affected by high soil erosion rates. The area is characterized by undulating topography caused by intensive agricultural practices with poor soil conservation practices. The soil loss rates were determined and conservation strategies have been evaluated under different slope classes and land uses. The results showed that the watershed is affected by high soil erosion rates (on average 42 t ha-1 yr-1), greater than the maximum tolerable soil loss (18 t ha-1 yr-1). The highest soil loss (456 t ha-1 yr-1) estimated from the upper watershed occurred on cultivated lands of steep slopes. As a result, soil erosion is mainly aggravated by land-use conflicts and topographic factors and the rugged topographic land forms of the area. The study also demonstrated that the contribution of existing soil conservation structures to erosion control is very small due to incorrect design and poor management. About 35 % out of the existing structures can reduce soil loss significantly since they were constructed correctly. Most of the existing structures were demolished due to the sediment overload, vulnerability to livestock damage and intense rainfall. Therefore, appropriate and standardized soil and water conservation measures for different erosion-prone land uses and land forms need to be implemented in Koga

Viewpoint: Sustainability of piñon-juniper ecosystems - A unifying perspective of soil erosion thresholds

Science.gov (United States)

Davenport, David W.; Breshears, D.D.; Wilcox, B.P.; Allen, Craig D.

1998-01-01

Many pinon-juniper ecosystem in the western U.S. are subject to accelerated erosion while others are undergoing little or no erosion. Controversy has developed over whether invading or encroaching pinon and juniper species are inherently harmful to rangeland ecosystems. We developed a conceptual model of soil erosion in pinon-jumper ecosystems that is consistent with both sides of the controversy and suggests that the diverse perspectives on this issue arise from threshold effects operating under very different site conditions. Soil erosion rate can be viewed as a function of (1) site erosion potential (SEP), determined by climate, geomorphology and soil erodibility; and (2) ground cover. Site erosion potential and cove act synergistically to determine soil erosion rates, as evident even from simple USLE predictions of erosion. In pinon-juniper ecosystem with high SEP, the erosion rate is highly sensitive to ground cover and can cross a threshold so that erosion increases dramatically in response to a small decrease in cover. The sensitivity of erosion rate to SEP and cover can be visualized as a cusp catastrophe surface on which changes may occur rapidly and irreversibly. The mechanisms associated with a rapid shift from low to high erosion rate can be illustrated using percolation theory to incorporate spatial, temporal, and scale-dependent patterns of water storage capacity on a hillslope. Percolation theory demonstrates how hillslope runoff can undergo a threshold response to a minor change in storage capacity. Our conceptual model suggests that pinion and juniper contribute to accelerated erosion only under a limited range of site conditions which, however, may exist over large areas.

Erosion-Oxidation Response of Boiler Grade Steels: A Mathematical Investigation

Directory of Open Access Journals (Sweden)

S. K. Das

2008-01-01

Full Text Available A ductile erosion model embodying the mechanisms of erosion involving cutting wear and repeated plastic deformation has been developed to predict erosion rates of boiler grade steels. The issue of erosion-oxidation interaction has also been addressed to further predict the mass loss resulted from this composite mechanism. A deterministic formalism for the kinetics of oxide-scale growth and a probabilistic approach to characterize the material loss are employed to describe simultaneous actions of high-temperature oxidation and mechanical erosion. The model predictions are in good agreement with the published data.

Erosion of a grooved surface caused by impact of particle-laden flow

Science.gov (United States)

Jung, Sohyun; Yang, Eunjin; Kim, Ho-Young

2016-11-01

Solid erosion can be a life-limiting process for mechanical elements in erosive environments, thus it is of practical importance in many industries such as construction, mining, and coal conversion. Erosion caused by particle-laden flow occurs through diverse mechanisms, such as cutting, plastic deformation, brittle fracture, fatigue and melting, depending on particle velocity, total particle mass and impingement angle. Among a variety of attempts to lessen erosion, here we investigate the effectiveness of millimeter-sized grooves on the surface. By experimentally measuring the erosion rates of smooth and triangular-grooved surfaces under various impingement angles, we find that erosion can be significantly reduced within a finite range of impingement angles. We show that such erosion resistance is attributed to the swirls of air within grooves and the differences in erosive strength of normal and slanted impact. In particular, erosion is mitigated when we increase the effective area under normal impact causing plastic deformation and fracture while decreasing the area under slanted impact that cuts the surface to a large degree. Our quantitative model for the erosion rate of grooved surfaces considering the foregoing effects agrees with the measurement results.

Holocene versus modern catchment erosion rates at 300 MW Baspa II hydroelectric power plant (India, NW Himalaya)

Science.gov (United States)

Draganits, Erich; Gier, Susanne; Hofmann, Christa-Ch.; Janda, Christoph; Bookhagen, Bodo; Grasemann, Bernhard

2014-08-01

300 MW Baspa II is India's largest private hydroelectric facility, located at the Baspa River which is an important left-hand tributary to the Sutlej River in the NW Himalaya (India). In this valley the Sangla palaeo-lake has been dammed around 8200 yr BP behind a rock-avalanche dam and Baspa II is located exactly on top of this palaeo-lake. This special location represents a very rare possibility to evaluate the short-term, river load and hydrological parameters measured during the planning and operational stages of Baspa II with the long-term parameters gained from the palaeo-lake sediments from the catchment. Sedimentological and geomorphological investigations of the lacustrine sediments have been used to reconstruct environmental changes during >2500 years of its existence. The Mid-Holocene erosion rates of the Baspa catchment estimated from the volume and duration of deposition of the exposed lake sediments are at 0.7-1.0 mm yr-1, almost identical with the modern erosion rates calculated from river gauge data from Baspa II. Several charcoal layers and charcoal pieces from the uppermost palaeo-lake levels around 5000 cal yr BP might be related to woodland clearance and they possibly represent one of the oldest evidences for human presence in the Baspa Valley during Neolithic time.

The positive impact of European subsidies on soil erosion rates in orange plantations

Science.gov (United States)

Keesstra, Saskia; Jordán, Antonio; Novara, Agata; Taguas, Tani; Pereira, Paulo; Brevik, Eric C.; Cerdà, Artemi

2017-04-01

Soil erosion in orchards and vineyards has been found non-sustainable due to bare soils due to the use of herbicides and tillage (Novara et al., 2011; Taguas et al., 2015; Ochoa et al., 2016; Rodrigo Comino et al., 2016a; 2016b; 2016c). Citrus plantations in sloping terrains are also non-sustainable from the soil erosion point of view due high erosion rates and the damage caused on infra-structures (Cerdà et al., 2009; 2009b; Cerdà et al., 2011; Pereira et al., 2015). This is not uncommon in Mediterranean type Ecosystems (Cerdà et al., 2010) but there is a need to reduce the soil and water losses to achieve sustainability (Brevik et al., 2015; Keesstra et al., 2016). The use of mulches, geotextiles, catch crops, and vegetation was found to be very successful as a sustainable strategy to reduce the soil losses (Giménez Morera et al., 2010; Mwango et al., 2016; Nawaz et al., 2016; Nishigaki et al., 2016; Prosdocimi et al., 2016). Nowadays, chipped branches are applied in orchards and vineyards because of European subsidies; however little scientific data is available on the impact of the chipped branches mulch on soil erosion. In an orange plantation in Eastern Valencia, at the L'Alcoleja experimental station the impact of these chipped branches was tested under 45 mm h-1 rainfall simulations on laboratory plots of 0.5 m2 under with different covers of chipped branches. The results show that with a cover of 20 % with chipped branches soil erosion reduces by 78 %. Acknowledgements The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement 603498 (RECARE project) and the CGL2013- 47862-C2-1-R and CGL2016-75178-C2-2-R national research projects. References Brevik, E. C., Cerdà, A., Mataix-Solera, J., Pereg, L., Quinton, J. N., Six, J., and Van Oost, K. 2015. The interdisciplinary nature of SOIL, SOIL, 1, 117-129, doi:10.5194/soil-1-117-2015, Cerdà, A. and M. F. Jurgensen

Slurry erosion induced surface nanocrystallization of bulk metallic glass

Science.gov (United States)

Ji, Xiulin; Wu, Jili; Pi, Jinghong; Cheng, Jiangbo; Shan, Yiping; Zhang, Yingtao

2018-05-01

Microstructure evolution and phase transformation of metallic glasses (MGs) could occur under heating condition or mechanical deformation. The cross-section of as-cast Zr55Cu30Ni5Al10 MG rod was impacted by the solid particles when subjected to erosion in slurry flow. The surface microstructure was observed by XRD before and after slurry erosion. And the stress-driven de-vitrification increases with the increase of erosion time. A microstructure evolution layer with 1-2 μm thickness was formed on the topmost eroded surface. And a short range atomic ordering prevails in the microstructure evolution layer with crystalline size around 2-3 nm embedded in the amorphous matrix. The XPS analysis reveals that most of the metal elements in the MG surface, except for Cu, were oxidized. And a composite layer with ZrO2 and Al2O3 phases were formed in the topmost surface after slurry erosion. The cooling rate during solidification of MG has a strong influence on the slurry erosion induced nanocrystallization. And a lower cooling rate favors the surface nanocrystallization because of lower activation energy and thermo-stability. Finally, the slurry erosion induced surface nanocrystallization and microstructure evolution result in surface hardening and strengthening. Moreover, the microstructure evolution mechanisms were discussed and it is related to the cooling rate of solidification and the impact-induced temperature rise, as well as the combined effects of the impact-induced plastic flow, inter-diffusion and oxidation of the metal elements.

Determination of gross gamma and gross beta activities in liquid effluent samples. Phase I

International Nuclear Information System (INIS)

Curtis, K.E.; Sood, S.P.

1985-08-01

Several inadequacies in the presently used procedures for gross gamma and gross beta measurements in aqueous wastes have been identified. Both the presence of suspended particulate activity and the use of cesium-137 as a calibration standard can cause gross gamma measurements to overestimate the actual activity in the sample. At the same time, sample preparation for the determination of gross beta activities causes large losses of radioiodine before the measurement step and the presence of solid material can cause a serious decrease in the beta counting efficiency. A combination of these errors could result in large discrepancies between the results obtained by the two measurement methods. Improved procedures are required to overcome these problems

Comparison of Inconel 625 and Inconel 600 in resistance to cavitation erosion and jet impingement erosion

International Nuclear Information System (INIS)

Hu, H.X.; Zheng, Y.G.; Qin, C.P.

2010-01-01

Liquid droplet erosion (LDE), which often occurs in bellows made of nickel-based alloys, threatens the security operation of the nuclear power plant. As the candidate materials of the bellows, Inconel 600 and Inconel 625 were both tested for resistance to cavitation erosion (CE) and jet impingement erosion (JIE) through vibratory cavitation equipment and a jet apparatus for erosion-corrosion. Cumulative mass loss vs. exposure time was used to evaluate the erosion rate of the two alloys. The surface and cross-sectional morphologies before and after the erosion tests were observed by scanning electron microscopy (SEM), the inclusions were analyzed by an energy dispersive spectroscopy (EDS), and the surface roughness was also measured by surface roughness tester to illustrate the evolution of erosion process. The results show that the cumulative mass loss of CE of Inconel 625 is about 1/6 that of Inconel 600 and the CE incubation period of the Inconel 625 is 4 times as long as that of the Inconel 600. The micro-morphology evolution of CE process illustrates that the twinning and hardness of the Inconel 625 plays a significant role in CE. In addition, the cumulative mass loss of JIE of Inconel 625 is about 2/3 that of Inconel 600 at impacting angle of 90 o , and almost equal to that of the Inconel 600 at impacting angle of 30 o . Overall, the resistance to CE and JIE of Inconel 625 is much superior to that of Inconel 600.

Improvement of gross theory of beta-decay for application to nuclear data

Science.gov (United States)

Koura, Hiroyuki; Yoshida, Tadashi; Tachibana, Takahiro; Chiba, Satoshi

2017-09-01

A theoretical study of β decay and delayed neutron has been carried out with a global β-decay model, the gross theory. The gross theory is based on a consideration of the sum rule of the β-strength function, and gives reasonable results of β-decay rates and delayed neutron in the entire nuclear mass region. In a fissioning nucleus, neutrons are produced by β decay of neutron-rich fission fragments from actinides known as delayed neutrons. The average number of delayed neutrons is estimated based on the sum of the β-delayed neutron-emission probabilities multiplied by the cumulative fission yield for each nucleus. Such a behavior is important to manipulate nuclear reactors, and when we adopt some new high-burn-up reactors, properties of minor actinides will play an important roll in the system, but these data have not been sufficient. We re-analyze and improve the gross theory. For example, we considered the parity of neutrons and protons at the Fermi surface, and treat a suppression for the allowed transitions in the framework of the gross theory. By using the improved gross theory, underestimated half-lives in the neutron-rich indium isotopes and neighboring region increase, and consequently follow experimental trend. The ability of reproduction (and also prediction) of the β-decay rates, delayed-neutron emission probabilities is discussed. With this work, we have described the development of a programming code of the gross theory of β-decay including the improved parts. After preparation finished, this code can be released for the nuclear data community.

The Erosion of Frozen Argon by Swift Helium Ions

DEFF Research Database (Denmark)

Besenbacher, F.; Bøttiger, Jørgen; Graversen, O.

1981-01-01

The temperature, energy, and thickness dependence of the erosion rates of frozen argon films when irradiated with 0.1–3 MeV helium ions have been measured. The erosion yields Y are much too high to be explained by the concentional collisional cascade-sputtering theory and are furthermore unequivo......The temperature, energy, and thickness dependence of the erosion rates of frozen argon films when irradiated with 0.1–3 MeV helium ions have been measured. The erosion yields Y are much too high to be explained by the concentional collisional cascade-sputtering theory and are furthermore...... unequivocally associated with electronic processes generated by the bombarding particle. In the present energy region, it is found that Y scales approximately as the electronic stopping power squared, depends on the charge state of the incoming helium ions, and perhaps more important, is independent...

The similarity of river evolution at the initial stage of channel erosion

Science.gov (United States)

Lin, Jiun-Chuan

2014-05-01

The study deals with a comparison study of two types of rocks at the initial stage of channel erosion in Taiwan. It is interesting that channel erosion at different types of rocks shows some similarity. There are two types of rocks: sandstone at Ta-an River, central Taiwan where river channel erosion from the nick point because of earthquake uplifting and mud rock at Tainan, southern Taiwan where rill erosion on a flat surface after artificial engineering. These two situations are both at the beginning stage of channel erosion, there are some similar landform appeared on channels. However the rate of erosion and magnitude of erosion are different. According to the using of photogrammetry method to reconstruct archive imageries and field surveying by total station and 3D scanner at different stages. The incision rate is high both at the Ta-an River and the bank erosion and it is even more obvious at mud rock area because of erodibility of mud rock. The results show that bank erosion and incision both are obvious processes. Bank erosion made channel into meander. The bank erosion cause slope in a asymmetric channel profile. The incision process will start at the site where land is relatively uplifted. This paper demonstrates such similarity and landform characters.

In-Situ Measurement of Hall Thruster Erosion Using a Fiber Optic Regression Probe

Science.gov (United States)

Polzin, Kurt; Korman, Valentin

2009-01-01

One potential life-limiting mechanism in a Hall thruster is the erosion of the ceramic material comprising the discharge channel. This is especially true for missions that require long thrusting periods and can be problematic for lifetime qualification, especially when attempting to qualify a thruster by analysis rather than a test lasting the full duration of the mission. In addition to lifetime, several analytical and numerical models include electrode erosion as a mechanism contributing to enhanced transport properties. However, there is still a great deal of dispute over the importance of erosion to transport in Hall thrusters. The capability to perform an in-situ measurement of discharge channel erosion is useful in addressing both the lifetime and transport concerns. An in-situ measurement would allow for real-time data regarding the erosion rates at different operating points, providing a quick method for empirically anchoring any analysis geared towards lifetime qualification. Erosion rate data over a thruster s operating envelope would also be useful in the modeling of the detailed physics inside the discharge chamber. There are many different sensors and techniques that have been employed to quantify discharge channel erosion in Hall thrusters. Snapshots of the wear pattern can be obtained at regular shutdown intervals using laser profilometry. Many non-intrusive techniques of varying complexity and sensitivity have been employed to detect the time-varying presence of erosion products in the thruster plume. These include the use quartz crystal microbalances, emission spectroscopy, laser induced flourescence, and cavity ring-down spectroscopy. While these techniques can provide a very accurate picture of the level of eroded material in the thruster plume, it is more difficult to use them to determine the location from which the material was eroded. Furthermore, none of the methods cited provide a true in-situ measure of erosion at the channel surface while

Use of cesium-137 methodology in the evaluation of superficial erosive processes

International Nuclear Information System (INIS)

Andrello, Avacir Casanova; Appoloni, Carlos Roberto; Guimaraes, Maria de Fatima; Nascimento Filho, Virgilio Franco do

2003-01-01

Superficial erosion is one of the main soil degradation agents and erosion rates estimations for different edaphic climate conditions for the conventional models, as USLE and RUSLE, are expensive and time-consuming. The use of cesium- 137 anthropogenic radionuclide is a new methodology that has been much studied and its application in the erosion soil evaluation has grown in countries as USA, UK, Australia and others. A brief narration of this methodology is being presented, as the development of the equations utilized for the erosion rates quantification through the cesium- 137 measurements. Two watersheds studied in Brazil have shown that the cesium- 137 methodology was practicable and coherent with the survey in field for applications in erosion studies. (author)

A terminological matter: paragenesis, antigravitative erosion or antigravitational erosion ?

Directory of Open Access Journals (Sweden)

Pasini G.

2009-07-01

Full Text Available In the speleological literature three terms are utilized to designate the “ascending erosion”: paragenesis (= paragénésis, coined in1968, antigravitative erosion (= erosione antigravitativa, coined in 1966 and antigravitational erosion (wrong English translation ofthe Italian term erosione antigravitativa, utilized later on. The term paragenesis should be abandoned because of the priority of theterm erosione antigravitativa - on the ground of the “law of priority” – and because of its ambiguous etimology. On the other hand,the term antigravitational erosion should be forsaken in favour of the term antigravitative erosion, given the meaning that the termsgravitation and gravity have in Physics. Therefore, to designate the phenomenon of the “ascending erosion” there would be nothingleft but the term antigravitative erosion.The antigravitative erosion process and its recognizability are illustrated.Examples of caves with evident antigravitative erosion phenomena, developed in different karstifiable rocks and in several partsof the world, are given.It is recalled that the antigravitative erosion is a phenomenon well-known since 1942 and widely proven and supported, and that it isrelatively easy – in many cases - to recognize the antigravitative origin of karstic passages.It is stressed that the antigravitative erosion is an important phenomenon, exclusive of the karstic caves and unique in nature.

Gross alpha and gross beta determination in surface and groundwater water by liquid scintillation counting (LSC)

International Nuclear Information System (INIS)

Faria, Ligia S.; Moreira, Rubens M.

2013-01-01

The present study has used 40 samples of groundwater and surface water collected at four different sites along the period of one year in Brumadinho and Nova Lima, two municipalities in the State of Minas Gerais, Brazil, as part of a more extensive study aiming at determination of the natural radioactivity in the water used for domestic use. These two sites are inside an Environmental Protection Area is located in a region of very intensive iron ore exploration. In addition of mineral resources, the region has a geological characteristic that includes quartzitic conglomerates associated with uranium. Radioactivity levels were determined via liquid scintillation counting (LSC), a fast and high counting efficiency method that can be advantageously employed to determine gross alpha and gross beta activity in liquid samples. Previously to gross alpha and gross beta counting the samples were acidified with concentrated HNO 3 in the field. The technique involved a pre-concentration of the sample to obtain a low detection limit. Specific details of the employed methodology are commented. The results showed that concentrations of gross alpha natural activity and gross beta values ranged from less than the detection limit of the equipment (0.03 Bq.L -1 ) to 0.275 ± 0.05 Bq.L -1 for gross alpha. As regards gross beta, all samples were below the limit of detection. (author)

Ways of TPP and NPP powerful steam turbine blade erosion decreasing in low flow rate regimes

International Nuclear Information System (INIS)

Khrabrov, P.V.; Khaimov, V.A.; Matveenko, V.A.

1986-01-01

A systematized approach to the problem of efficient cooling of flow passage and exhaust parts of TPP and NPP steam turbines and prevention of erosion wear of inlet and outlet edges of operating blades is presented. Methods for LP casing cooling and sources of erosion-hazard moisture as well as the main technological and design measures to decrease the erosion of blades are determined

Three Gorges Reservoir Area: soil erosion under natural condition vs. soil erosion under current land use

Science.gov (United States)

Schönbrodt, Sarah; Behrens, Thorsten; Scholten, Thomas

2010-05-01

Xiangjiaba site (mean 640.1 t ha-1 a-1) the maximum soil erosion of 1,115.4 t ha-1 a-1 under natural conditions is negligible lower. Compared to these erosion rates the mean soil loss under current land use is considerably lower (Xiangxi Catchment: mean 161.5 t ha-1 a-1; Backwater area: mean 166.3 t ha-1 a-1; Quyuan: mean 211.2 t ha-1 a-1; Xiangjiaba: mean 158.6 t ha-1 a-1). However, soil loss of maximum 2,662.2 t ha-1 a-1 for Xiangxi Catchment, 2,397.9 t ha-1 a-1 for the backwater area, 1,689.9 t ha-1 a-1 for Quyuan site, and 957.1 t ha-1 a-1 for Xiangjiaba site are also potentially possible. According to the Chinese Soil Erosion Rate Standard (cf. Xu et al., 2008) almost 44 % of the area of the Xiangxi Catchment show extreme (> 80 t ha-1 a-1) soil erosion which mainly occur in the backwater area. Our results show that the Xiangxi Catchment is already highly prone to soil erosion under natural conditions. In places, the current land use in the mountainous relief of the Xiangxi Catchment still increases the potential soil erosion to an extreme high level. However, mean potential soil loss rates under current land use lie under those due to the natural disposition. This is due to the fact that the natural disposition to soil erosion does not consider the complete topography factor (LS factor), that effects the potential soil loss (R² = 0.77) by the human-influenced erosive slope length through farmland terraces. Moreover, our results indicate an urgent need of proper management and conservation decisions in order to reduce soil erosion against the background of a high land use dynamic in a region with low carrying capacity (Beattie, 2002). Literature Beattie, J. (2002): Dam Building, Dissent, And Development: The Emergence Of The Three Gorges Project. New Zealand Journal of Asian Studies, Vol. 4(1): 138-158. Behrens, T., Schmidt, K. and Scholten, T. (2008). An approach to remove uncertainties in nominal environmental covariates and soil class maps. In: Hartemink, A. E., Mc

Erosion of heat-treated AISI 4140 steel

Energy Technology Data Exchange (ETDEWEB)

Goretta, K.C. (Materials and Components Tech. Div., Argonne National Lab., IL (United States)); Thompson, A.C. (Materials and Components Tech. Div., Argonne National Lab., IL (United States)); Routbort, J.L. (Materials Science Div., Argonne National Lab., IL (United States))

1993-03-15

Solid-particle erosion was studied on AISI 4140 steel heat treated to have a Vickers hardness (Hv) of 288-650 kg mm[sup -2]. The experiments were conducted in vacuum with 143 [mu]m Al[sub 2]O[sub 3] abrasive impacting at 50-100 m s[sup -1] at an angle of 30 or 90 . Erosion rates were nearly independent of hardness for Hv[<=]365 kg mm[sup -2], but increased with hardness for Hv>365 kg mm[sup -2]. The improved erosion resistances of the softer alloys were attributed to increased ductilities. (orig.). Letter-to-the-editor

Activity level of gross α and gross β in airborne aerosol samples around the Qinshan NPP

International Nuclear Information System (INIS)

Chen Bin; Ye Jida; Chen Qianyuan; Wu Xiaofei; Song Weili; Wang Hongfeng

2007-01-01

The monitoring results of gross α and gross 13 activity from 2001 to 2005 for environmental airborne aerosol samples around the Qinshan NPP base are presented in this paper. A total of 170 aerosol samples were collected from monitoring sites of Caichenmen village, Qinlian village, Xiajiawan village and Yangliucun village around the Qinshan NPP base. The measured specific activity of gross α and gross β are in the range of 0.02-0.38 mBq/m 3 and 0.10-1.81 mBq/m 3 , respectively, with an average of 0.11 mBq/m 3 and 0.45mBq/m 3 , respectively. They are lower than the average of 0.15 mBq/m 3 and 0.52 mBq/m 3 , of reference site at Hangzhou City. It is indicated that the specific activity of gross α and gross β for environmental aerosol samples around the Qinshan NPP base had not been increased in normal operating conditions of the NPP. (authors)

Bentonite erosion. Final report

Energy Technology Data Exchange (ETDEWEB)

Birgersson, Martin; Boergesson, Lennart; Hedstroem, Magnus; Karnland, Ola; Nilsson, Ulf (Clay Technology AB, Lund (Sweden))

2009-12-15

Low saline water may reach KBS-3 repository depth, e.g. during periods of glaciation. Under such aqueous conditions, the montmorillonite part of the bentonite buffer might transform into a sol and thereby be transported away with flowing water in fractures. The primary aim with this report is to improve the understanding of the basic principles for this possible montmorillonite particle release. The report includes experimental and theoretical work performed at Clay Technology. Natural bentonite and ion-exchanged purified montmorillonite from three different geographical origins, Wyoming (U.S.), Milos (Greece) and Kutch (India) have been studied. Experimental and/or theoretical investigations have been performed with respect to: - Free swelling ability; - Rheological properties; - Rate of bentonite loss into fractures; - Filtering; - Ion exchange; - Sol formation ability; - Ion diffusion; - Mass loss due to erosion. The performed erosion experiments show that erosion does not occur in a mixed calcium/sodium montmorillonite with at least 20% calcium in exchange positions, when the external solution contains above 4 mM charge equivalents. This result is in agreement with the presented conceptual view of sol formation and measured equilibrium properties in mixed calcium/sodium montmorillonite. The findings imply that the buffer will be stable for non-glacial conditions. However, erosion due to sol formation cannot be ruled out for glacial conditions.

Bentonite erosion. Final report

International Nuclear Information System (INIS)

Birgersson, Martin; Boergesson, Lennart; Hedstroem, Magnus; Karnland, Ola; Nilsson, Ulf

2009-12-01

Low saline water may reach KBS-3 repository depth, e.g. during periods of glaciation. Under such aqueous conditions, the montmorillonite part of the bentonite buffer might transform into a sol and thereby be transported away with flowing water in fractures. The primary aim with this report is to improve the understanding of the basic principles for this possible montmorillonite particle release. The report includes experimental and theoretical work performed at Clay Technology. Natural bentonite and ion-exchanged purified montmorillonite from three different geographical origins, Wyoming (U.S.), Milos (Greece) and Kutch (India) have been studied. Experimental and/or theoretical investigations have been performed with respect to: - Free swelling ability; - Rheological properties; - Rate of bentonite loss into fractures; - Filtering; - Ion exchange; - Sol formation ability; - Ion diffusion; - Mass loss due to erosion. The performed erosion experiments show that erosion does not occur in a mixed calcium/sodium montmorillonite with at least 20% calcium in exchange positions, when the external solution contains above 4 mM charge equivalents. This result is in agreement with the presented conceptual view of sol formation and measured equilibrium properties in mixed calcium/sodium montmorillonite. The findings imply that the buffer will be stable for non-glacial conditions. However, erosion due to sol formation cannot be ruled out for glacial conditions.

Uncertainty in soil carbon accounting due to unrecognized soil erosion.

Science.gov (United States)

Sanderman, Jonathan; Chappell, Adrian

2013-01-01

The movement of soil organic carbon (SOC) during erosion and deposition events represents a major perturbation to the terrestrial carbon cycle. Despite the recognized impact soil redistribution can have on the carbon cycle, few major carbon accounting models currently allow for soil mass flux. Here, we modified a commonly used SOC model to include a soil redistribution term and then applied it to scenarios which explore the implications of unrecognized erosion and deposition for SOC accounting. We show that models that assume a static landscape may be calibrated incorrectly as erosion of SOC is hidden within the decay constants. This implicit inclusion of erosion then limits the predictive capacity of these models when applied to sites with different soil redistribution histories. Decay constants were found to be 15-50% slower when an erosion rate of 15 t soil ha(-1)  yr(-1) was explicitly included in the SOC model calibration. Static models cannot account for SOC change resulting from agricultural management practices focused on reducing erosion rates. Without accounting for soil redistribution, a soil sampling scheme which uses a fixed depth to support model development can create large errors in actual and relative changes in SOC stocks. When modest levels of erosion were ignored, the combined uncertainty in carbon sequestration rates was 0.3-1.0 t CO2  ha(-1)  yr(-1) . This range is similar to expected sequestration rates for many management options aimed at increasing SOC levels. It is evident from these analyses that explicit recognition of soil redistribution is critical to the success of a carbon monitoring or trading scheme which seeks to credit agricultural activities. © 2012 Blackwell Publishing Ltd.

Bank erosion of navigation canals in the western and central Gulf of Mexico

Science.gov (United States)

Thatcher, Cindy A.; Hartley, Stephen B.; Wilson, Scott A.

2011-01-01

Erosion of navigation canal banks is a direct cause of land loss, but there has been little quantitative analysis to determine why certain major canals exhibit faster widening rates (indicative of erosion) than others in the coastal zones of Texas, Louisiana, Mississippi, and Alabama. We hypothesize that navigation canals exhibit varying rates of erosion based on soil properties of the embankment substrate, vegetation type, geologic region (derived from digital versions of state geologic maps), and the presence or absence of canal bank armaments (that is, rock rip-rap, concrete bulkheads, or other shoreline protection structures). The first objective of this project was to map the shoreline position and substrate along both banks of the navigation canals, which were digitized from 3 different time periods of aerial photography spanning the years of 1978/79 to 2005/06. The second objective was to quantify the erosion rates of the navigation canals in the study area and to determine whether differences in erosion rates are related to embankment substrate, vegetation type, geologic region, or soil type. To measure changes in shoreline position over time, transects spaced at 50-m (164-ft) intervals were intersected with shorelines from all three time periods, and an annual rate of change was calculated for each transect. Mean annual rates of shoreline change ranged from 1.75 m/year (5.74 ft/year) on the west side of the Atchafalaya River, La., where there was shoreline advancement or canal narrowing, to -3.29 m/year (-10.79 ft/year) on the south side of the Theodore Ship Channel, Ala., where there was shoreline retreat or erosion. Statistical analysis indicated that there were significant differences in shoreline retreat rates according to geologic region and marsh vegetation type, and a weak relationship with soil organic content. This information can be used to better estimate future land loss rates associated with navigation canals and to prioritize the location of

The new energy management policy: Indonesian PSC-gross-split applied on steam flooding project

Science.gov (United States)

Irham, S.; Julyus, P.

2018-01-01

“SIPY” oil field has been producing oil using steam flooding technology since 1992 under the PSC-Cost-Recovery policy. In 2021, the contract will be finished, and a new agreement must be submitted to the Indonesian government. There are two applied fiscal policies on oil and gas management: PSC-Cost-Recovery and PSC-Gross-Split (introduced in 2017 as the new energy management plan). The contractor must choose between PSC-Cost-Recovery and PSC-Gross-split which makes more profit. The aim of this research is to determine the best oil and gas contract policy for the contractor. The methods are calculating contractor cash flow and comparing the Profitability Indexes. The results of this study are (1) Net Present Values for the PSC-Cost-Recovery and the PSC-Gross-Split are 15 MMUS and 61 MMUS, respectively; and (2) Internal Rate of Return values for the PSC-Cost-Recovery and PSC-Gross-Split are 10% and 11%, respectively. The conclusion is that the Net Present Value and Internal Rate of Return of PSC-Gross-Split are greater than those of PSC-Cost-Recovery, but in Pay Out Time of PSC-Gross-split is longer than Pay Out Time in PSC-Cost-Recovery. Thus, the new energy management policy will be more attractive than PSC-Cost-Recovery.

Comparison of Inconel 625 and Inconel 600 in resistance to cavitation erosion and jet impingement erosion

Energy Technology Data Exchange (ETDEWEB)

Hu, H.X. [State Key Laboratory for Corrosion and Protection, Institute of Metal Research, Chinese Academy of Science, 62 Wencui Road, Shenyang 110016 (China); Zheng, Y.G., E-mail: ygzheng@imr.ac.c [State Key Laboratory for Corrosion and Protection, Institute of Metal Research, Chinese Academy of Science, 62 Wencui Road, Shenyang 110016 (China); Qin, C.P. [State Key Laboratory for Corrosion and Protection, Institute of Metal Research, Chinese Academy of Science, 62 Wencui Road, Shenyang 110016 (China)

2010-10-15

Liquid droplet erosion (LDE), which often occurs in bellows made of nickel-based alloys, threatens the security operation of the nuclear power plant. As the candidate materials of the bellows, Inconel 600 and Inconel 625 were both tested for resistance to cavitation erosion (CE) and jet impingement erosion (JIE) through vibratory cavitation equipment and a jet apparatus for erosion-corrosion. Cumulative mass loss vs. exposure time was used to evaluate the erosion rate of the two alloys. The surface and cross-sectional morphologies before and after the erosion tests were observed by scanning electron microscopy (SEM), the inclusions were analyzed by an energy dispersive spectroscopy (EDS), and the surface roughness was also measured by surface roughness tester to illustrate the evolution of erosion process. The results show that the cumulative mass loss of CE of Inconel 625 is about 1/6 that of Inconel 600 and the CE incubation period of the Inconel 625 is 4 times as long as that of the Inconel 600. The micro-morphology evolution of CE process illustrates that the twinning and hardness of the Inconel 625 plays a significant role in CE. In addition, the cumulative mass loss of JIE of Inconel 625 is about 2/3 that of Inconel 600 at impacting angle of 90{sup o}, and almost equal to that of the Inconel 600 at impacting angle of 30{sup o}. Overall, the resistance to CE and JIE of Inconel 625 is much superior to that of Inconel 600.

Sand mining impacts on long-term dune erosion in southern Monterey Bay

Science.gov (United States)

Thornton, E.B.; Sallenger, Abby; Sesto, Juan Conforto; Egley, L.; McGee, Timothy; Parsons, Rost

2006-01-01

Southern Monterey Bay was the most intensively mined shoreline (with sand removed directly from the surf zone) in the U.S. during the period from 1906 until 1990, when the mines were closed following hypotheses that the mining caused coastal erosion. It is estimated that the yearly averaged amount of mined sand between 1940 and 1984 was 128,000 m3/yr, which is approximately 50% of the yearly average dune volume loss during this period. To assess the impact of sand mining, erosion rates along an 18 km range of shoreline during the times of intensive sand mining (1940–1990) are compared with the rates after sand mining ceased (1990–2004). Most of the shoreline is composed of unconsolidated sand with extensive sand dunes rising up to a height of 46 m, vulnerable to the erosive forces of storm waves. Erosion is defined here as a recession of the top edge of the dune. Recession was determined using stereo-photogrammetry, and LIDAR and GPS surveys. Long-term erosion rates vary from about 0.5 m/yr at Monterey to 1.5 m/yr in the middle of the range, and then decrease northward. Erosion events are episodic and occur when storm waves and high tides coincide, allowing swash to undercut the dune and resulting in permanent recession. Erosion appears to be correlated with the occurrence of El Niños. The calculated volume loss of the dune in southern Monterey Bay during the 1997–98 El Niño winter was 1,820,000 m3, which is almost seven times the historical annual mean dune erosion of 270,000 m3/yr. The alongshore variation in recession rates appears to be a function of the alongshore gradient in mean wave energy and depletions by sand mining. After cessation of sand mining in 1990, the erosion rates decreased at locations in the southern end of the bay but have not significantly changed at other locations.

Experiment of cavitation erosion at the exit of a long orifice

Energy Technology Data Exchange (ETDEWEB)

Yagi, Yoshinori; Murase, Michio [Inst. of Nuclear Safety System Inc., Mihama, Fukui (Japan)

2002-09-01

We performed experiments to clarify mechanism of cavitation erosion and to predict cavitation erosion rate at the exit of a long orifice equipped at the chemical and volume control system in a pressurized water reactor (PWR). In order to find this mechanism, we used a high speed video camera. As the result, we observed bubble collapses near the exit of the orifice when flow condition was oscillating. So the bubble collapses due to the oscillation might cause the first stage erosion at the exit of the orifice. Using the orifice which had the cone-shaped exit, we observed that bubbles collapsed near the exit and then they collapsed at the upstream like a chain reaction. So this bubble collapse mechanism could be explained as follows: shock wave was generated by the bubble collapse near the exit, then it propagated upwards, consequently it caused the bubble collapse at the upstream. And we predicted erosion rate by evaluating the effect of the velocity and comparing the erosion resistance between the test speciment (aluminum) and the plant material (stainless steel) by means of vibratory tests. We compared the predicted erosion rate with that of the average value estimated from plant investigation, then we examined the applicability of these method to the plant evaluations. (author)

Advances in modeling soil erosion after disturbance on rangelands

Science.gov (United States)

Research has been undertaken to develop process based models that predict soil erosion rate after disturbance on rangelands. In these models soil detachment is predicted as a combination of multiple erosion processes, rain splash and thin sheet flow (splash and sheet) detachment and concentrated flo...

Projected climate change impacts in rainfall erosivity over Brazil

Science.gov (United States)

Climate change projections and historical analyses have shown alterations in global precipitation dynamics, and therefore, it is also expected that there will be associated changes to soil erosion rates. The impacts of climate change on soil erosion may bring serious economic, social, and environmen...

Density Development During Erosion Experiments of Cohesive Sediments

DEFF Research Database (Denmark)

Johansen, Claus; Larsen, Torben

1998-01-01

The density development during erosion experiments was investigated. The calculation of the erosion rate requires the knowledge of the density profile with respect to the consolidation time(Parchure, 1984). At present, the basic assumption in the calculations is that the density profile is achiev...... in order to obtail time invariant sediment properties during the experiments....

An Analytical Model for Basin-scale Glacier Erosion as a Function of Climate and Topography

Science.gov (United States)

Jaffrey, M.; Hallet, B.

2017-12-01

Knowledge about glacier erosion has advanced considerably over the last few decades with the emergence of a firm mechanistic understanding of abrasion and quarrying, the growing sophistication of complex numerical models of glacial erosion and the evolution of glacial landforms, and the increase in data from field studies of erosion rates. Interest in glacial erosion has also intensified and diversified substantially as it is increasingly recognized as a key process affecting the heights of mountains, the overall evolution of mountain belts, and the coupling of climate, erosion, and tectonics. Yet, the general controls of glacier erosion rates have not been addressed theoretically, and the large range of published basin-scale erosion rates, covering more than 3 orders of magnitude, remains poorly understood. To help gain insight into glacier erosion rates at the scale of glacier basins, the only scale for which extensive data exist, we develop analytically a simple budget of the total mechanical energy per unit time, the power, dissipated by a steady state glacier in sliding, S, and viscous deformation, V. We hypothesize that the power for the work of erosion derives solely from S and that the basin wide erosion rate scales with S averaged over the basin. We solve the power budget directly in terms of climatic and topographic parameters, showing explicitly that the source of power to drive both S and V is the gravitational power supplied by the net snow accumulation (mass balance). The budget leads to the simple metric φ=mbΔz2 for the basin average of S with Δz being the glacier basin relief and mb the gradient of the mass balance with elevation. The dependence of φ on the square of the relief arises from both the mass balance's and potential energy's linear increases with elevation. We validate φ using results from a comprehensive field study of erosion rates paired with glaciological data along a transect extending from Southern Patagonia to the Antarctic

[Effect of prescribed burning on grassland nitrogen gross mineralization and nitrification].

Science.gov (United States)

Li, Yuzhong; Zhu, Tingcheng; Li, Jiandong; Zhou, Daowei

2003-02-01

The seasonal dynamics of nitrogen gross mineralization, nitrification, and mineral nitrogen consumption rates in burned and unburned Leymus chinensis grasslands were studied with 15N pool dilution technique. The results indicated that the gross mineralization and nitrification rates in burned area were higher than those in unburned area in April and May, and lower than those in unburned area in September. NH4(+)-N consumption rates were higher than unburned area in April and May, and lower in September. NO3(-)-N consumption rates were higher than control in April and May, and lower than control in July and September. The NH4(+)-N concentrations were higher in burned area in April, May and July, and no difference in September. NO3(-)-N concentrations were no difference between burned and unburned areas in April and May, and higher in burned areas in July and September.

Numerical modelling of concentrated leak erosion during Hole Erosion Tests

OpenAIRE

Mercier, F.; Bonelli, S.; Golay, F.; Anselmet, F.; Philippe, P.; Borghi, R.

2015-01-01

This study focuses on the numerical modelling of concentrated leak erosion of a cohesive soil by a turbulent flow in axisymmetrical geometry, with application to the Hole Erosion Test (HET). The numerical model is based on adaptive remeshing of the water/soil interface to ensure accurate description of the mechanical phenomena occurring near the soil/water interface. The erosion law governing the interface motion is based on two erosion parameters: the critical shear stress and the erosion co...

In situ estimation of erosion and deposition thresholds by Acoustic Doppler Velocimeter (ADV)

DEFF Research Database (Denmark)

Andersen, T.J.; Fredsøe, Jørgen; Pejrup, M.

2007-01-01

Field-based estimations of bed shear stress have been made using SonTek/YSI 10 MHz ADVs (Acoustic Doppler Velocimeter) at the Kongsmark mudflat, Danish Wadden Sea, in order to test if it was possible to estimate erosion and deposition thresholds in situ by use of unidirectional tidal and orbital...... (wave) currents. The results were promising and erosion thresholds were in the same range as those observed in EROMES erosion experiments carried out at the same site. Similarly, the short-term erosion rates which could be calculated matched closely those obtained with EROMES, and were in the same range...... as those published for a large annular flume (Sea Carousel) from another fine-grained site. This indicates that the erosion rates obtained with those two erosion-instruments are reasonable estimates of the actual erosion taking place under natural tidal current and waves. One advantage of the use of ADVs...

Parameters Affecting the Erosive Burning of Solid Rocket Motor

OpenAIRE

Abdelaziz Almostafa; Guozhu Liang; Elsayed Anwer

2018-01-01

Increasing the velocity of gases inside solid rocket motors with low port-to-throat area ratios, leading to increased occurrence and severity of burning rate augmentation due to flow of propellant products across burning propellant surfaces (erosive burning), erosive burning of high energy composite propellant was investigated to supply rocket motor design criteria and to supplement knowledge of combustion phenomena, pressure, burning rate and high velocity of gases all of these are parameter...

PERGERAKAN HARGA SAHAM AKIBAT PERUBAHAN NILAI TUKAR, INFLASI, TINGKAT BUNGA, DAN GROSS DOMESTIC PRODUCT

Directory of Open Access Journals (Sweden)

Shinta Heru Satoto

2017-03-01

Full Text Available The purposes of this study were to provide an empirical evidence of the influence of macroeconomic variablesand the time varying volatility phenomena on stock price. This research used manufactured firms that list onIndonesian Capital Market on 2009 until 2011 periods for the sampel. This research also used several macroeconomicsvariables such as exchange rate, inflation, BI rate, and Gross Domestic Product. The empirical resultshowed that exchange rate, BI rate, and Gross Domestic Product influenced stock price. The result also showedthat time varying volatility was happenend on stock price fluctuation. This result indicated that Indonesianstock price have high volatility on 2009 til 2011 periods

Sediment contributions from floodplains and legacy sediments to Piedmont streams of Baltimore County, Maryland

Science.gov (United States)

Donovan, Mitchell; Miller, Andrew; Baker, Matthew; Gellis, Allen

2015-04-01

Disparity between watershed erosion rates and downstream sediment delivery has remained an important theme in geomorphology for many decades, with the role of floodplains in sediment storage as a common focus. In the Piedmont Province of the eastern USA, upland deforestation and agricultural land use following European settlement led to accumulation of thick packages of overbank sediment in valley bottoms, commonly referred to as legacy deposits. Previous authors have argued that legacy deposits represent a potentially important source of modern sediment loads following remobilization by lateral migration and progressive channel widening. This paper seeks to quantify (1) rates of sediment remobilization from Baltimore County floodplains by channel migration and bank erosion, (2) proportions of streambank sediment derived from legacy deposits, and (3) potential contribution of net streambank erosion and legacy sediments to downstream sediment yield within the Mid-Atlantic Piedmont. We calculated measurable gross erosion and deposition rates within the fluvial corridor along 40 valley segments from 18 watersheds with drainage areas between 0.18 and 155 km2 in Baltimore County, Maryland. We compared stream channel and floodplain morphology from lidar-based digital elevation data collected in 2005 with channel positions recorded on 1:2400 scale topographic maps from 1959-1961 in order to quantify 44-46 years of channel change. Sediment bulk density and particle size distributions were characterized from streambank and channel deposit samples and used for volume to mass conversions and for comparison with other sediment sources. Average annual lateral migration rates ranged from 0.04 to 0.19 m/y, which represented an annual migration of 2.5% (0.9-4.4%) channel width across all study segments, suggesting that channel dimensions may be used as reasonable predictors of bank erosion rates. Gross bank erosion rates varied from 43 to 310 Mg/km/y (median = 114) and were

26 CFR 1.61-1 - Gross income.

Science.gov (United States)

2010-04-01

... 26 Internal Revenue 2 2010-04-01 2010-04-01 false Gross income. 1.61-1 Section 1.61-1 Internal Revenue INTERNAL REVENUE SERVICE, DEPARTMENT OF THE TREASURY (CONTINUED) INCOME TAX (CONTINUED) INCOME TAXES (CONTINUED) Definition of Gross Income, Adjusted Gross Income, and Taxable Income § 1.61-1 Gross...

Impacts of shoreline erosion on coastal ecosystems in Songkhla Province

Directory of Open Access Journals (Sweden)

Nipaporn Chusrinuan

2009-07-01

Full Text Available Songkhla Province is located on the eastern coast of the southern Thai Peninsula, bordering the Gulf of Thailand for approximately 107 km. Most of the basin’s foreshores have been extensively developed for housing, tourism and shrimp farming. The beaches are under deteriorating impacts, often causing sediment transport which leads to an unnaturally high erosion rate. This natural phenomenon is considered to be a critical problem in the coastal areas affected by the hazard of coastal infrastructure and reduced beach esthetics for recreation. In this study, shoreline changes were compared between 1975 and 2006 using aerial photographs and Landsat imageries using Geographic Information System (GIS. The results revealed that 18.5 km2 of the coastal areas were altered during the period. Of this, 17.3 km2 suffered erosion and 1.2 km2were subjected to accretion. The most significant changes occurred between 1975-2006. Shoreline erosion was found at Ban Paktrae, Ranot District, with an average erosion rate of 5.3 m/year, while accretion occurred at Laem Samila, MuangSongkhla District with an average accretion rate of 2.04 m/year. The occurrences of shoreline erosion have contributed to the degradation of coastal soil and water quality, destruction of beach and mangrove forests, loss of human settlements and livelihood.These processes have led to deterioration of the quality of life of the residents. Prevention and mitigation measures to lessen economic and social impacts due to shoreline erosion are discussed.

Use of 7Be to document soil erosion associated with a short period of extreme rainfall

International Nuclear Information System (INIS)

Sepulveda, A.; Schuller, P.; Walling, D.E.; Castillo, A.

2008-01-01

Intensification and expansion of agricultural production since the 1970s have increased soil erosion problems in south-central Chile. Quantitative information on soil loss is needed for erosion risk assessment and to establish the effectiveness of improved land management practices. Since information from traditional sources, such as erosion plots, is limited, attention has been directed to the use of environmental radionuclides for documenting erosion rates. Cs-137 has been successfully utilised for this purpose, but only provides information on medium-term erosion rates. There is also a need to document event-related soil erosion. This paper outlines the basis for using 7 Be measurements to document short-term erosion and reports its successful use for quantifying the erosion that occurred within an arable field, as a result of a period of heavy rainfall (400 mm in 27 days) occurring in May 2005. The study field had been under a no-till, no-burning system for 18 years, but immediately prior to the period of heavy rainfall the harvest residues were burnt. The erosion recorded therefore reflected both the extreme nature of the rainfall and the effects of the burning in increasing surface runoff and erosion. The sampled area corresponded to that used previously by the authors to document the medium-term erosion rates associated with both conventional tillage and the subsequent switch to a no-till system. Comparisons between the erosion documented for the period of heavy rainfall in 2005 with these medium-term erosion rates permits some tentative conclusions regarding the importance of extreme events and the impact of burning in increasing the erosion associated with the no-till system

Progress of nuclide tracing technique in the study of soil erosion in recent decade

International Nuclear Information System (INIS)

Liu Gang; Yang Mingyi; Liu Puling; Tian Junliang

2007-01-01

In the last decade nuclide tracing technique has been widely employed in the investigation of soil erosion, which makes the studies of soil erosion into a new and rapid development period. This paper tried to review the recent progress of using 137 Cs, 210 Pb ex , 7 Be, composite tracers and REE-INAA in soil erosion rate, sedimentation rate, sediment source and soil erosion processes study, and also the existing research results. The trends for future development and questions are also discussed. (authors)

Validating the use of 137Cs and 210Pbex measurements to estimate rates of soil loss from cultivated land in southern Italy.

Science.gov (United States)

Porto, Paolo; Walling, Des E

2012-04-01

Soil erosion represents an important threat to the long-term sustainability of agriculture and forestry in many areas of the world, including southern Italy. Numerous models and prediction procedures have been developed to estimate rates of soil loss and soil redistribution, based on the local topography, hydrometeorology, soil type and land management. However, there remains an important need for empirical measurements to provide a basis for validating and calibrating such models and prediction procedures as well as to support specific investigations and experiments. In this context, erosion plots provide useful information on gross rates of soil loss, but are unable to document the efficiency of the onward transfer of the eroded sediment within a field and towards the stream system, and thus net rates of soil loss from larger areas. The use of environmental radionuclides, particularly caesium-137 ((137)Cs) and excess lead-210 ((210)Pb(ex)), as a means of estimating rates of soil erosion and deposition has attracted increasing attention in recent years and the approach has now been recognised as possessing several important advantages. In order to provide further confirmation of the validity of the estimates of longer-term erosion and soil redistribution rates provided by (137)Cs and (210)Pb(ex) measurements, there is a need for studies aimed explicitly at validating the results obtained. In this context, the authors directed attention to the potential offered by a set of small erosion plots located near Reggio Calabria in southern Italy, for validating estimates of soil loss provided by (137)Cs and (210)Pb(ex) measurements. A preliminary assessment suggested that, notwithstanding the limitations and constraints involved, a worthwhile investigation aimed at validating the use of (137)Cs and (210)Pb(ex) measurements to estimate rates of soil loss from cultivated land could be undertaken. The results demonstrate a close consistency between the measured rates of soil

Formulating Fine to Medium Sand Erosion for Suspended Sediment Transport Models

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François Dufois

2015-08-01

Full Text Available The capacity of an advection/diffusion model to predict sand transport under varying wave and current conditions is evaluated. The horizontal sand transport rate is computed by vertical integration of the suspended sediment flux. A correction procedure for the near-bed concentration is proposed so that model results are independent of the vertical resolution. The method can thus be implemented in regional models with operational applications. Simulating equilibrium sand transport rates, when erosion and deposition are balanced, requires a new empirical erosion law that involves the non-dimensional excess shear stress and a parameter that depends on the size of the sand grain. Comparison with several datasets and sediment transport formulae demonstrated the model’s capacity to simulate sand transport rates for a large range of current and wave conditions and sand diameters in the range 100–500 μm. Measured transport rates were predicted within a factor two in 67% of cases with current only and in 35% of cases with both waves and current. In comparison with the results obtained by Camenen and Larroudé (2003, who provided the same indicators for several practical transport rate formulations (whose means are respectively 72% and 37%, the proposed approach gives reasonable results. Before fitting a new erosion law to our model, classical erosion rate formulations were tested but led to poor comparisons with expected sediment transport rates. We suggest that classical erosion laws should be used with care in advection/diffusion models similar to ours, and that at least a full validation procedure for transport rates involving a range of sand diameters and hydrodynamic conditions should be carried out.

Simultaneous acid exposure and erosive particle wear of thermoset coatings

DEFF Research Database (Denmark)

Møller, Victor Buhl; Dam-Johansen, Kim; Frankær, Sarah Maria

2018-01-01

, similar to the erosion/corrosion-type phenomena found in metals. A vinyl ester-based coating was the most resistant to the simultaneous erosive/acidic exposure, with a maximum polishing rate of 3.24±0.61 μm/week, while novolac epoxy and polyurethane coatings showed high polishing rates of 11.7±1.50 and 13.4±0......Handling acidic chemicals is a challenge in the chemical industry, requiring a careful choice of contact material. Certain thermoset organic coatings are applicable in low pH environments, but when particulate erosion is also present the performance demand is increased. This is the case in, e...

137Cs profiles in erosion plots with different soil cultivation

International Nuclear Information System (INIS)

Andrello, A.C.; Appoloni, C.R.; Cassol, E.A.; Melquiades, F.L.

2006-01-01

Cesium-137 methodology has been successfully used to assess soil erosion. Seven erosion plots were sampled to determine the 137 Cs profile and to assess the erosion rates. Cesium-137 profile for native pasture plot showed an exponential decline below 5 cm depth, with little 137 Cs activity in the superficial layer (0-5 cm). Cesium-137 profile for wheat-soybean rotation plot in conventional tillage showed a uniform distribution with depth. For this plot, the soil loss occurs more in middle than upper and lower level. Cesium-137 profile for wheat-soybean rotation and wheat-maize rotation plots in no-tillage showed a similar result to the native pasture, with a minimum soil loss in the superficial layer. Cesium-137 profile for bare soil and cultivated pasture plots are similar, with a soil erosion rate of 229 t ha -1 year -1 . In the plots with a conventional tillage a greater soil loss occur in middle than upper and lower level. In no-tillage cultivation plots occurs soil loss in lower level, but no sign of soil loss neither gain in the upper level is observed. Cesium-137 methodology is a good tool to assess soil erosion and the 137 Cs profile gives a possibility to understand the soil erosion behavior in erosion plots. (author)

Extreme soil erosion rates in citrus slope plantations and control strategies. A literature review

Science.gov (United States)

Cerdà, Artemi; Ángel González Peñaloza, Félix; Pereira, Paulo; Reyes Ruiz Gallardo, José; García Orenes, Fuensanta; Burguet, María

2013-04-01

Soil Erosion is a natural process that shapes the Earth. Due to the impact of agriculture, soil erosion rates increase, landforms show gullies and rills, and soils are depleted. In the Mediterranean, wheat, olive and vineyards were the main agriculture products, but new plantations are being found in sloping terrain due to the drip-irrigation. This new strategy results in the removal of the traditional terraces in order to make suitable for mechanization the agriculture plantation. Citrus is a clear example of the impact of the new chemical agriculture with a high investment in herbicides, pesticides, mechanisation, land levelling and drip computer controlled irrigation systems. The new plantation of citrus orchards is found in the Mediterranean, but also in California, Florida, China and Brazil. Chile, Argentina, and South Africa are other producers that are moving to an industrial production of citrus. This paper shows how the citrus plantations are found as one of the most aggressive plantation due to the increase in soil erosion, and how we can apply successful control strategies. The research into the high erosion rates of citrus orchard built on the slopes are mainly found in China (Wu et al., 1997; Xu et al., 2010; Wang et al., 2011; Wu et al., 2011; Liu et al., 2011; Lü et al., 2011; Xu et al., 2012) and in the Mediterranean (Cerdà and Jurgensen, 2008; 2009; Cerdà et al., 2009a; 2009b; Cerdà et al., 2011; 2012) Most of the research done devoted to the measurements of the soil losses but also some research is done related to the soil properties (Lu et al., 1997; Lü et al., 2012; Xu et al., 2012) and the impact of cover crops to reduce the soil losses (Lavigne et al., 2012; Le Bellec et al., 2012) and the use of residues such as dried citrus peel in order to reduce the soil losses. There are 116 million tonnes of citrus produced yearly, and this affects a large surface of the best land. The citrus orchards are moving from flood irrigated to drip

Fractional Bhatnagar-Gross-Krook kinetic equation

Science.gov (United States)

Goychuk, Igor

2017-11-01

The linear Boltzmann equation (LBE) approach is generalized to describe fractional superdiffusive transport of the Lévy walk type in external force fields. The time distribution between scattering events is assumed to have a finite mean value and infinite variance. It is completely characterized by the two scattering rates, one fractional and a normal one, which defines also the mean scattering rate. We formulate a general fractional LBE approach and exemplify it with a particularly simple case of the Bohm and Gross scattering integral leading to a fractional generalization of the Bhatnagar, Gross and Krook (BGK) kinetic equation. Here, at each scattering event the particle velocity is completely randomized and takes a value from equilibrium Maxwell distribution at a given fixed temperature. We show that the retardation effects are indispensable even in the limit of infinite mean scattering rate and argue that this novel fractional kinetic equation provides a viable alternative to the fractional Kramers-Fokker-Planck (KFP) equation by Barkai and Silbey and its generalization by Friedrich et al. based on the picture of divergent mean time between scattering events. The case of divergent mean time is also discussed at length and compared with the earlier results obtained within the fractional KFP. Also a phenomenological fractional BGK equation without retardation effects is proposed in the limit of infinite scattering rates. It cannot be, however, rigorously derived from a scattering model, being rather clever postulated. It this respect, this retardationless equation is similar to the fractional KFP by Barkai and Silbey. However, it corresponds to the opposite, much more physical limit and, therefore, also presents a viable alternative.

Is Snow Gliding a Major Soil Erosion Agent in Steep Alpine Areas?

International Nuclear Information System (INIS)

Meusburger, K.; Walter, A.; Alewell, C.; Leitinger, G.; Mabit, L.; Mueller, M.H.

2015-01-01

Snow cover is a key hydrological characteristic of mountain areas. Nevertheless, a majority of studies focused on quantifying rates of soil erosion and sediment transport in steep mountain areas has largely neglected the role of snow cover on soil erosion rates (Stanchi et al., 2014). Soil erosion studies have focused almost exclusively on the snow-free periods even though it is well known that wet avalanches can yield enormous erosive forces (Freppaz et al., 2010; Korup and Rixen, 2014). This raises the question whether annual snow cover and particularly the slow movement of snow packages over the soil surface, termed ‘‘snow gliding’’, contribute significantly to the total soil loss in these areas. Three different approaches to estimate soil erosion rates were used to address this question. These include (1) the anthropogenic soil tracer 137 Cs, (2) the Revised Universal Soil Loss Equation (RUSLE), and (3) direct sediment yield measurements of snow glide deposits. The fallout radionuclide 137 Cs integrates total soil loss due to all erosion agents involved, the RUSLE model is suitable to estimate soil loss by water erosion and the sediment yield measurements yield represents a direct estimate of soil removal by snow gliding. Moreover, cumulative snow glide distance was measured for 14 sites and modelled for the surrounding area with the Spatial Snow Glide Model (Leitinger et al., 2008)

Divertor tungsten tiles erosion in the region of the castellated gaps

Energy Technology Data Exchange (ETDEWEB)

Hu, Wanpeng, E-mail: wangdez@dlut.edu.cn; Sang, Chaofeng; Sun, Zhenyue; Wang, Dezhen

2016-11-01

Highlights: • Simulation of the tungsten tiles erosion by different impurities in the divertor gap region is done by using a 2d3v Particle-In-Cell code. • High-Z impurity causes the largest erosion rate on W tile. • The peak physical sputtering erosion rate locates at the plasma-facing corners. - Abstract: Erosion of tungsten (W) is a very important issue for the future fusion device. The castellated divertor makes it more complicated due to complex geometry of the gap between the tiles. In this work, the plasma behaviors and resulting W tile erosion in the divertor tile gap region are studied by using a two dimension-in-space and three dimension-in-velocity (2d3 v) Particle-In-Cell (PIC) code. Deuterium ions (D{sup +}) and electrons are traced self-consistently in the simulation to provide the plasma background. Since there are lots of impurities, which may make a great impact on the tile erosion, in the divertor region to radiate the power, the erosion of W tile by different species are thus considered. The contributions of deuterium and impurities: Li, C, Ne, and Ar, to the W erosion, are studied under EAST conditions to show a straightforward insight. It is observed that the physical sputtering of W tile by impurities is much higher than that by the D ions, and the peak erosion region locates at the plasma-facing corners.

Wind-Driven Erosion and Exposure Potential at Mars 2020 Rover Candidate-Landing Sites

Science.gov (United States)

Chojnacki, Matthew; Banks, Maria; Urso, Anna

2018-01-01

Aeolian processes have likely been the predominant geomorphic agent for most of Mars’ history and have the potential to produce relatively young exposure ages for geologic units. Thus, identifying local evidence for aeolian erosion is highly relevant to the selection of landing sites for future missions, such as the Mars 2020 Rover mission that aims to explore astrobiologically relevant ancient environments. Here we investigate wind-driven activity at eight Mars 2020 candidate-landing sites to constrain erosion potential at these locations. To demonstrate our methods, we found that contemporary dune-derived abrasion rates were in agreement with rover-derived exhumation rates at Gale crater and could be employed elsewhere. The Holden crater candidate site was interpreted to have low contemporary erosion rates, based on the presence of a thick sand coverage of static ripples. Active ripples at the Eberswalde and southwest Melas sites may account for local erosion and the dearth of small craters. Moderate-flux regional dunes near Mawrth Vallis were deemed unrepresentative of the candidate site, which is interpreted to currently be experiencing low levels of erosion. The Nili Fossae site displayed the most unambiguous evidence for local sand transport and erosion, likely yielding relatively young exposure ages. The downselected Jezero crater and northeast Syrtis sites had high-flux neighboring dunes and exhibited substantial evidence for sediment pathways across their ellipses. Both sites had relatively high estimated abrasion rates, which would yield young exposure ages. The downselected Columbia Hills site lacked evidence for sand movement, and contemporary local erosion rates are estimated to be relatively low. PMID:29568719

Wind-Driven Erosion and Exposure Potential at Mars 2020 Rover Candidate-Landing Sites

Science.gov (United States)

Chojnacki, Matthew; Banks, Maria; Urso, Anna

2018-02-01

Aeolian processes have likely been the predominant geomorphic agent for most of Mars' history and have the potential to produce relatively young exposure ages for geologic units. Thus, identifying local evidence for aeolian erosion is highly relevant to the selection of landing sites for future missions, such as the Mars 2020 Rover mission that aims to explore astrobiologically relevant ancient environments. Here we investigate wind-driven activity at eight Mars 2020 candidate-landing sites to constrain erosion potential at these locations. To demonstrate our methods, we found that contemporary dune-derived abrasion rates were in agreement with rover-derived exhumation rates at Gale crater and could be employed elsewhere. The Holden crater candidate site was interpreted to have low contemporary erosion rates, based on the presence of a thick sand coverage of static ripples. Active ripples at the Eberswalde and southwest Melas sites may account for local erosion and the dearth of small craters. Moderate-flux regional dunes near Mawrth Vallis were deemed unrepresentative of the candidate site, which is interpreted to currently be experiencing low levels of erosion. The Nili Fossae site displayed the most unambiguous evidence for local sand transport and erosion, likely yielding relatively young exposure ages. The downselected Jezero crater and northeast Syrtis sites had high-flux neighboring dunes and exhibited substantial evidence for sediment pathways across their ellipses. Both sites had relatively high estimated abrasion rates, which would yield young exposure ages. The downselected Columbia Hills site lacked evidence for sand movement, and contemporary local erosion rates are estimated to be relatively low.

Influence of perforation erosion on multiple growing hydraulic fractures in multi-stage fracturing

Directory of Open Access Journals (Sweden)

Yongming Li

2018-02-01

Full Text Available In multi-stage hydraulic fracturing, the limited-entry method is widely used to promote uniform growth of multiple fractures. However, this method's effectiveness may be lost because the perforations will be eroded gradually during the fracturing period. In order to study the influence of perforation erosion on multiple growing hydraulic fractures, we combined the solid–fluid coupled model of hydraulic fracture growth with an empirical model of perforation erosion to implement numerical simulation. The simulations show clearly that the erosion of perforation will significantly deteriorate the non-uniform growth of multiple fractures. Based on the numerical model, we also studied the influences of proppant concentration and injection rates on perforation erosion in multi-stage hydraulic fracturing. The results indicate that the initial erosion rates become higher with the rising proppant concentration, but the growth of multiple hydraulic fractures is not sensitive to the varied proppant concentration. In addition, higher injection rates are beneficial significantly to the limited-entry design, leading to more uniform growth of fractures. Thus, in multi-stage hydraulic fracturing enough high injection rates are proposed to keep uniform growths. Keywords: Unconventional oil and gas reservoir, Horizontal well, Perforation friction, Perforation erosion, Multi-stage hydraulic fracturing, Numerical simulation, Mathematic model, Uniform growth of fractures

Assessment of soil erosion vulnerability in the heavily populated and ecologically fragile communities in Motozintla de Mendoza, Chiapas, Mexico

Science.gov (United States)

González-Morales, Selene B.; Mayer, Alex; Ramírez-Marcial, Neptalí

2018-06-01

Variability in physical rates and local knowledge of soil erosion was assessed across six rural communities in the Sierra Madre del Sur, Chiapas, Mexico. The average erosion rate estimated using the RUSLE model is 274 t ha-1 yr-1, with the estimated erosion rates ranging from 28 to 717 t ha-1 yr-1. These very high erosion rates are associated with high rainfall erosivity (17 000 MJ mm ha-1 h-1 yr-1) and steep slopes (mean slope = 67 %). Many of the highest soil erosion rates are found in communities that are dominated by forestland, but where most of the tree cover has been removed. Conversely, lower erosion rates are often found where corn is cultivated for most of the year. According to the results of the soil erosion KAP (knowledge, attitude and practices) survey, awareness of the concept of soil erosion was reasonably high in all of the communities, but awareness of the causes of erosion was considerably lower. More than half of respondents believed that reforestation is a viable option for reducing soil erosion, but only a third of respondents were currently implementing reforestation practices. Another third of the respondents indicated that they were not following any soil conservation practices. Respondents indicated that adoption of government reforestation efforts have been hindered by the need to clear their land to sell forest products or cultivate corn. Respondents also mentioned the difficulties involved with obtaining favorable tree stocks for reforestation. The KAP results were used to assess the overall level of motivation to solve soil erosion problems by compiling negative responses. The relationship between the magnitude of the soil erosion problem and the capacity to reduce soil erosion is inconsistent across the communities. One community, Barrio Vicente Guerrero, had the highest average negative response rate and the second highest soil erosion rate, indicating that this community is particularly vulnerable.

Infra Red Aerial Photograph Interpretation for Soil Erosion at Wuryantoro, Wonogiri

Directory of Open Access Journals (Sweden)

S Suharjo

2016-07-01

Full Text Available Collecting data of soil erosion hazard terrestrially needs much time, high cost, and large energy. Therefore it is needed appropriate technology in addition to terrestrially decreasing necessity of time, cost and energy. Aerial photograph is picture of earth surface, which shape and place similar to condition on earth surface. Using aerial photograph in this research is expected to be able to take account for erosion factors. This research is conducted in Kecamatan Wuryantoro Kabupaten Wonogiri. Research method that used is aerial photograph interpretation with land unit approach. Amounts of soil lost are approached with USLE formula. Aerial photograph that used in this research is aerial photograph coloured infrared with 1:10.000 in scale and 1991 in year of taking photography. The result shows that using aerial photograph is very useful in supporting soil erosion rate calculation. Erosion rate at research area is 0.0968 ton/ha/year to 100.4344 ton/ha/year. This number is included in class of light erosion hazard (

Paleo erosion rates and climate shifts recorded by Quaternary cut-and-fill sequences in the Pisco valley, central Peru

Science.gov (United States)

Bekaddour, Toufik; Schlunegger, Fritz; Vogel, Hendrik; Delunel, Romain; Norton, Kevin P.; Akçar, Naki; Kubik, Peter

2014-03-01

Fluvial cut-and-fill sequences have frequently been reported from various sites on Earth. Nevertheless, the information about the past erosional regime and hydrological conditions have not yet been adequately deciphered from these archives. The Quaternary terrace sequences in the Pisco valley, located at ca. 13°S, offer a manifestation of an orbitally-driven cyclicity in terrace construction where phases of sediment accumulation have been related to the Minchin (48-36 ka) and Tauca (26-15 ka) lake level highstands on the Altiplano. Here, we present a 10Be-based sediment budget for the cut-and-fill terrace sequences in this valley to quantify the orbitally forced changes in precipitation and erosion. We find that the Minchin period was characterized by an erosional pulse along the Pacific coast where denudation rates reached values as high as 600±80 mm/ka for a relatively short time span lasting a few thousands of years. This contrasts to the younger pluvial periods and the modern situation when 10Be-based sediment budgets register nearly zero erosion at the Pacific coast. We relate these contrasts to different erosional conditions between the modern and the Minchin time. First, the sediment budget infers a precipitation pattern that matches with the modern climate ca. 1000 km farther north, where highly erratic and extreme El Niño-related precipitation results in fast erosion and flooding along the coast. Second, the formation of a thick terrace sequence requires sufficient material on catchment hillslopes to be stripped off by erosion. This was most likely the case immediately before the start of the Minchin period, because this erosional epoch was preceded by a >50 ka-long time span with poorly erosive climate conditions, allowing for sufficient regolith to build up on the hillslopes. Finally, this study suggests a strong control of orbitally and ice sheet forced latitudinal shifts of the ITCZ on the erosional gradients and sediment production on the western

Use of cesium-137 to assess soil erosion rates under soybean, coffee and pasture

International Nuclear Information System (INIS)

Andrello, A.C.; Appoloni, C.R.; Guimaraes, M.F.

2003-01-01

The methodology cesium-137 was used to assess soil erosion and deposition rates in a small watershed with varied crops, at 23 deg 16' S and 51 deg 17' W, in a district of Cambe, Parana State, Brazil. A theoretical equation which considers soil loss or gain directly proportional to the cesium-137 redistribution was utilized in this study. In the watershed, soil redistribution was assessed by transect sampling, and the regional input of cesium-137 by radioactive rainfall determined based on samples from a point in the native forest. Most sampled pasture points presented soil loss, as well as the points in the soybean area under conventional tillage, while in the coffee crop there was neither soil loss nor gain. (author)

Reduction in soil loss from erosion-susceptible soils amended with humic substances from oxidized coal

International Nuclear Information System (INIS)

Piccolo, A.; Pietramellara, G.; Mbagwu, J.S.C.

1997-01-01

Soils that pose high risk of erosion require amendment with either natural or synthetic soil conditioners to reduce soil loss hazards. The objective of this study was to evaluate the potential of using coal-derived humic substances (as soil conditioners) to reduce runoff erosion on erosion-susceptible soils. Surface samples of severely degraded soils from Principina in Tuscany and Bovolone in Venice in Italy were used to assess the effects of five rates (0, 0.05, 0.01, 0.50 and 1.00 g/kg) of humic acids (HA) on soil loss and other hydrological parameters. The results showed that amending erosion-susceptible soils with low rates of coal-derived humic substances is a potentially effective soil management practice for reducing erosion rates

The amount of glacial erosion of the bedrock

International Nuclear Information System (INIS)

Paasse, Tore

2004-11-01

The purpose of this study is to estimate an upper bound for the average erosion of fresh bedrock that can reasonably be expected during a glacial period or a single glaciation. The study is based on the assumption that classic sediments, formed by Scandinavian ice erosion during the Quaternary period, still exist within the formerly glaciated area or its periphery. The volume of these sediments thus constitutes the maximum average glacial erosion of bedrock within this area. This volume is calculated by estimating the thickness of the minerogenic Quaternary from well data in Sweden and Denmark and from seismic measurements in adjacent sea areas. The average thickness of the Quaternary deposits and other reogolith in the investigated area was estimated to 16 m. Assuming that the whole volume is the result of glacial erosion of fresh bedrock this corresponds to 12 m depth. However, a great part of the sediments may consist of glacially redistributed Tertiary regolith. As the amount of Tertiary regolith is uncertain the estimated maximum average glacial erosion rate in fresh bedrock is uncertain, and assuming that the total sediment volume is the result of glacial erosion leads to an overestimation of the glacial erosion depth. Considering this, the average glacial erosion during a full glacial period has been estimated to between 0.2 m and 4 m. If the extremes in the made assumptions are excluded the glacial erosion during a glacial cycle can be estimated to about 1 m

The amount of glacial erosion of the bedrock

Energy Technology Data Exchange (ETDEWEB)

Paasse, Tore [Geological Survey of Sweden, Uppsala (Sweden)

2004-11-01

The purpose of this study is to estimate an upper bound for the average erosion of fresh bedrock that can reasonably be expected during a glacial period or a single glaciation. The study is based on the assumption that classic sediments, formed by Scandinavian ice erosion during the Quaternary period, still exist within the formerly glaciated area or its periphery. The volume of these sediments thus constitutes the maximum average glacial erosion of bedrock within this area. This volume is calculated by estimating the thickness of the minerogenic Quaternary from well data in Sweden and Denmark and from seismic measurements in adjacent sea areas. The average thickness of the Quaternary deposits and other reogolith in the investigated area was estimated to 16 m. Assuming that the whole volume is the result of glacial erosion of fresh bedrock this corresponds to 12 m depth. However, a great part of the sediments may consist of glacially redistributed Tertiary regolith. As the amount of Tertiary regolith is uncertain the estimated maximum average glacial erosion rate in fresh bedrock is uncertain, and assuming that the total sediment volume is the result of glacial erosion leads to an overestimation of the glacial erosion depth. Considering this, the average glacial erosion during a full glacial period has been estimated to between 0.2 m and 4 m. If the extremes in the made assumptions are excluded the glacial erosion during a glacial cycle can be estimated to about 1 m.

Numerical and experimental investigations on cavitation erosion

Science.gov (United States)

Fortes Patella, R.; Archer, A.; Flageul, C.

2012-11-01

A method is proposed to predict cavitation damage from cavitating flow simulations. For this purpose, a numerical process coupling cavitating flow simulations and erosion models was developed and applied to a two-dimensional (2D) hydrofoil tested at TUD (Darmstadt University of Technology, Germany) [1] and to a NACA 65012 tested at LMH-EPFL (Lausanne Polytechnic School) [2]. Cavitation erosion tests (pitting tests) were carried out and a 3D laser profilometry was used to analyze surfaces damaged by cavitation [3]. The method allows evaluating the pit characteristics, and mainly the volume damage rates. The paper describes the developed erosion model, the technique of cavitation damage measurement and presents some comparisons between experimental results and numerical damage predictions. The extent of cavitation erosion was correctly estimated in both hydrofoil geometries. The simulated qualitative influence of flow velocity, sigma value and gas content on cavitation damage agreed well with experimental observations.

Estimating the gross budget of applied nitrogen and phosphorus in tea plantations

Directory of Open Access Journals (Sweden)

Chi-Feng Chen

2016-05-01

Full Text Available To increase crop yield, high fertilizer application rates have generally been used. The residual fertilizers potentially become a source of diffused pollution, and degrade soil and water quality. Such nonpoint source pollution is a major threat to reservoir eutrophication. The best management practices (BMPs are usually used to prevent eutrophication; however, the environmental distribution of the applied fertilizers has not been understood properly. This could lead to a biased assessment of the rational quantity of nitrogen and phosphorous applied and the selection of BMPs. A field investigation of 32 plantations and 4 forests in the Feitsui Reservoir watershed, Taiwan, was conducted. Storm runoff water and soils were sampled, and a mass balance was used to demonstrate the gross nutrient budget. The results showed that when applying fertilizers of 2700 kg ha−1 in tea plantations only 18.3% of applied nitrogen and 5.5% of applied phosphorus were utilized by tea plants. Less than 5% of applied phosphorus was released in storm runoff, and more than 90% remained in the field. Approximately 30% of the nitrogen was lost through storm runoff, and 52% was stored in the soil mass. Therefore, reducing fertilizer application was recommended as the principal BMP, and collecting and treating storm runoff was suggested for controlling nitrogen pollution. The current management of soil erosion is an efficient measure for controlling phosphorus pollution.

A Mechanistic Model of Waterfall Plunge Pool Erosion into Bedrock

Science.gov (United States)

Scheingross, Joel S.; Lamb, Michael P.

2017-11-01

Landscapes often respond to changes in climate and tectonics through the formation and upstream propagation of knickzones composed of waterfalls. Little work has been done on the mechanics of waterfall erosion, and instead most landscape-scale models neglect waterfalls or use rules for river erosion, such as stream power, that may not be applicable to waterfalls. Here we develop a physically based model to predict waterfall plunge pool erosion into rock by abrasion from particle impacts and test the model against flume experiments. Both the model and experiments show that evolving plunge pools have initially high vertical erosion rates due to energetic particle impacts, and erosion slows and eventually ceases as pools deepen and deposition protects the pool floor from further erosion. Lateral erosion can continue after deposition on the pool floor, but it occurs at slow rates that become negligible as pools widen. Our work points to the importance of vertical drilling of successive plunge pools to drive upstream knickzone propagation in homogenous rock, rather than the classic mechanism of headwall undercutting. For a series of vertically drilling waterfalls, we find that upstream knickzone propagation is faster under higher combined water and sediment fluxes and for knickzones composed of many waterfalls that are closely spaced. Our model differs significantly from stream-power-based erosion rules in that steeper knickzones can retreat faster or more slowly depending on the number and spacing of waterfalls within a knickzone, which has implications for interpreting climatic and tectonic history through analysis of river longitudinal profiles.

Managing dental erosion.

Science.gov (United States)

Curtis, Donald A; Jayanetti, Jay; Chu, Raymond; Staninec, Michal

2012-01-01

The clinical signs of dental erosion are initially subtle, yet often progress because the patient remains asymptomatic, unaware and uninformed. Erosion typically works synergistically with abrasion and attrition to cause loss of tooth structure, making diagnosis and management complex. The purpose of this article is to outline clinical examples of patients with dental erosion that highlight the strategy of early identification, patient education and conservative restorative management. Dental erosion is defined as the pathologic chronic loss of dental hard tissues as a result of the chemical influence of exogenous or endogenous acids without bacterial involvement. Like caries or periodontal disease, erosion has a multifactorial etiology and requires a thorough history and examination for diagnosis. It also requires patient understanding and compliance for improved outcomes. Erosion can affect the loss of tooth structure in isolation of other cofactors, but most often works in synergy with abrasion and attrition in the loss of tooth structure (Table 1). Although erosion is thought to be an underlying etiology of dentin sensitivity, erosion and loss of tooth structure often occurs with few symptoms. The purpose of this article is threefold: first, to outline existing barriers that may limit early management of dental erosion. Second, to review the clinical assessment required to establish a diagnosis of erosion. And third, to outline clinical examples that review options to restore lost tooth structure. The authors have included illustrations they hope will be used to improve patient understanding and motivation in the early management of dental erosion.

Modelling of environmental and climatic problems: Wind and water erosion

International Nuclear Information System (INIS)

Aslan, Z.

2004-01-01

Magnitude of wind and water erosion mainly depend on wind velocity, rainfall rate, slope and soil characteristics. The main purpose of this lecture is to define the role of small, meso and large scale phenomena (local and synoptic fluctuations) on water and wind erosion. These lecture notes present some results on wind speed simulation and seasonal fluctuations of water deficit for the selected station in different erosion risque and transition regions of Turkey. (author)

Soil erosion rates caused by wind and saltating sand stresses in a wind tunnel

International Nuclear Information System (INIS)

Ligotke, M.W.

1993-02-01

Wind erosion tests were performed in a wind tunnel in support of the development of long-term protective barriers to cap stabilized waste sites at the Hanford Site. Controlled wind and saltating sand erosive stresses were applied to physical models of barrier surface layers to simulate worst-case eolian erosive stresses. The goal of these tests was to provide information useful to the design and evaluation of the surface layer composition of an arid-region waste site barrier concept that incorporates a deep fine-soil reservoir. A surface layer composition is needed that will form an armor resistant to eolian erosion during periods of extreme dry climatic conditions, especially when such conditions result in the elimination or reduction of vegetation by water deprivation or wildfire. Because of the life span required of Hanford waste barriers, it is important that additional work follow these wind tunnel studies. A modeling effort is planned to aid the interpretation of test results with respect to the suitability of pea gravel to protect the finite-soil reservoir during long periods of climatic stress. It is additionally recommended that wind tunnel tests be continued and field data be obtained at prototype or actual barrier sites. Results wig contribute to barrier design efforts and provide confidence in the design of long-term waste site caps for and regions

Assessment of mercury erosion by surface water in Wanshan mercury mining area.

Science.gov (United States)

Dai, ZhiHui; Feng, Xinbin; Zhang, Chao; Shang, Lihai; Qiu, Guangle

2013-08-01

Soil erosion is a main cause of land degradation, and in its accelerated form is also one of the most serious ecological environmental problems. Moreover, there are few studies on migration of mercury (Hg) induced by soil erosion in seriously Hg-polluted districts. This paper selected Wanshan Hg mining area, SW China as the study area. Revised universal soil loss equation (RUSLE) and Geographic information system (GIS) methods were applied to calculate soil and Hg erosion and to classify soil erosion intensity. Our results show that the soil erosion rate can reach up to 600,884tkm(-2)yr(-1). Surfaces associated with very slight and extremely severe erosion include 76.6% of the entire land in Wanshan. Furthermore, the cumulative erosion rates in the area impacted by extremely severe erosion make up 90.5% of the total. On an annual basis, Hg surface erosion load was predicted to be 505kgyr(-1) and the corresponding mean migration flux of Hg was estimated to be 3.02kgkm(-2)yr(-1). The erosion loads of Hg resulting from farmland and meadow soil were 175 and 319kgyr(-1) respectively, which were enhanced compared to other landscape types due to the fact that they are generally located in the steep zones associated with significant reclamation. Contributing to establish a mass balance of Hg in Wanshan Hg mining area, this study supplies a dependable scientific basis for controlling soil and water erosion in the local ecosystems. Land use change is the most effective way for reducing Hg erosion load in Wanshan mining area. Copyright © 2013 Elsevier Inc. All rights reserved.

Ash particle erosion on steam boiler convective section

Energy Technology Data Exchange (ETDEWEB)

Meuronen, V

1998-12-31

, diameter loss and wall thickness loss measurements of the test sleeves were taken. Erosion wear as a function of flow conditions, tube material and tube construction was analysed by single-variable linear regression analysis. In developing the erosion wear calculation equations, multi-variable linear regression analysis was used. In the staggered tube bank, erosion wear had a maximum value in a tube row 2 and a local maximum in row 5. In rows 3, 4 and 6, the erosion rate was low. On the other hand, in the in-line tube bank the minimum erosion rate occurred in tube row 2 and in further rows the erosion had an increasing value, so that in a six row tube bank, the maximum value occurred in row 6. (orig.) 37 refs.

Lifespan of mountain ranges scaled by feedbacks between landsliding and erosion by rivers.

Science.gov (United States)

Egholm, David L; Knudsen, Mads F; Sandiford, Mike

2013-06-27

An important challenge in geomorphology is the reconciliation of the high fluvial incision rates observed in tectonically active mountain ranges with the long-term preservation of significant mountain-range relief in ancient, tectonically inactive orogenic belts. River bedrock erosion and sediment transport are widely recognized to be the principal controls on the lifespan of mountain ranges. But the factors controlling the rate of erosion and the reasons why they seem to vary significantly as a function of tectonic activity remain controversial. Here we use computational simulations to show that the key to understanding variations in the rate of erosion between tectonically active and inactive mountain ranges may relate to a bidirectional coupling between bedrock river incision and landslides. Whereas fluvial incision steepens surrounding hillslopes and increases landslide frequency, landsliding affects fluvial erosion rates in two fundamentally distinct ways. On the one hand, large landslides overwhelm the river transport capacity and cause upstream build up of sediment that protects the river bed from further erosion. On the other hand, in delivering abrasive agents to the streams, landslides help accelerate fluvial erosion. Our models illustrate how this coupling has fundamentally different implications for rates of fluvial incision in active and inactive mountain ranges. The coupling therefore provides a plausible physical explanation for the preservation of significant mountain-range relief in old orogenic belts, up to several hundred million years after tectonic activity has effectively ceased.

Soft drinks and in vitro dental erosion.

Science.gov (United States)

Gravelle, Brent L; Hagen Ii, Ted W; Mayhew, Susan L; Crumpton, Brooks; Sanders, Tyler; Horne, Victoria

2015-01-01

The purpose of this investigation was to determine to what extent the in vitro exposure of healthy teeth to various commonly consumed carbonated soft drinks may precipitate dental erosion. Forty-two healthy, extracted, previously unerupted human molars were weighed prior to, during, and after suspension in various sugared and diet or zero-calorie carbonated beverages for 20 days; the specimens were stored at room temperature while being stirred at 275 rpm. The percentage decrease in tooth weight from before to after exposure represented the weight loss due to enamel erosion; values in the experimental groups varied from 3.22% to 44.52% after 20 days' exposure. Data were subjected to analysis of variance and post hoc Scheffe testing at a level of α = 0.05. Nonsugared drinks (diet and zero-calorie) as a whole were more erosive than sugared beverages. A significant positive correlation was found between the amount of titratable acid and percentage of tooth erosion, while a significant negative correlation was revealed between the beverage pH and percentage of tooth erosion. No significant correlations were found between calcium or phosphate ion concentrations and the amount of erosion. It appears that enamel erosion is dependent on not only the beverage flow rate, pH, and amount of titratable acid, but also whether the soft drink is of the diet or zero-calorie variety, which reflects the type of artificial sweetener present.

Comparison of erosion and erosion control works in Macedonia, Serbia and Bulgaria

Directory of Open Access Journals (Sweden)

Ivan Blinkov

2013-12-01

Natural conditions in the Balkan countries contribute to the appearance of various erosion forms and the intensity of the erosion processes. Over the history of these countries, people who settled this region used the available natural resources to fill their needs (tree cutting, incorrect plugging, overgrazing, which contributed to soil erosion. Organized erosion control works in the Balkans started in the beginning of the 20th century (1905 in Bulgaria. The highest intensity of erosion control works were carried out during the period 1945 – 1990. Various erosion control works were launched. Bulgaria had a large anti-erosion afforestation, almost 1 million ha. Bulgaria's ecological river restoration approach has been in use for almost 50 years. Serbia contributed significant erosion and torrent control works on hilly agricultural areas. Specific screen barrages and afforestation on extremely dry areas are characteristic in Macedonia. A common characteristic for all countries is a high decrease in erosion control works in the last 20 years.

Erosion-corrosion

International Nuclear Information System (INIS)

Aghili, B.

1999-05-01

A literature study on erosion-corrosion of pipings in the nuclear industry was performed. Occurred incidents are reviewed, and the mechanism driving the erosion-corrosion is described. Factors that influence the effect in negative or positive direction are treated, as well as programs for control and inspection. Finally, examples of failures from databases on erosion-corrosion are given in an attachment

CFD simulations of flow erosion and flow-induced deformation of needle valve: Effects of operation, structure and fluid parameters

Energy Technology Data Exchange (ETDEWEB)

Zhu, Hongjun, E-mail: ticky863@126.com [State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, Sichuan (China); State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu 610065, Sichuan (China); Pan, Qian; Zhang, Wenli; Feng, Guang; Li, Xue [State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, Sichuan (China)

2014-07-01

Highlights: • A combined FSI–CFD and DPM computational method is used to investigate flow erosion and deformation of needle valve. • The numerical model is validated with the comparison of measured and predicted erosion rate. • Effects of operation, structure and fluid parameters on flow erosion and flow-induced deformation are discussed. • Particle diameter has the most significant effect on flow erosion. • Inlet rate has the most obvious effect on flow-induced deformation. - Abstract: A three-dimensional fluid–structure interaction (FSI) computational model coupling with a combined continuum and discrete model has been used to predict the flow erosion rate and flow-induced deformation of needle valve. Comparisons with measured data demonstrate good agreement with the predictions of erosion rate. The flow field distribution of gas-particle flow and the erosion rate and deformation of valve core are captured under different operating and structural conditions with different fluid parameters. The effects of inlet velocity, valve opening and inlet valve channel size, particle concentration, particle diameter and particle phase components are discussed in detail. The results indicate that valve tip has the most severe erosion and deformation, and flow field, erosion rate and deformation of valve are all sensitive to inlet condition changes, structural changes and fluid properties changes. The effect of particle diameter on erosion is the most significant, while the influence of inlet rate on deformation is the greatest one.

AERO: A Decision Support Tool for Wind Erosion Assessment in Rangelands and Croplands

Science.gov (United States)

Galloza, M.; Webb, N.; Herrick, J.

2015-12-01

Wind erosion is a key driver of global land degradation, with on- and off-site impacts on agricultural production, air quality, ecosystem services and climate. Measuring rates of wind erosion and dust emission across land use and land cover types is important for quantifying the impacts and identifying and testing practical management options. This process can be assisted by the application of predictive models, which can be a powerful tool for land management agencies. The Aeolian EROsion (AERO) model, a wind erosion and dust emission model interface provides access by non-expert land managers to a sophisticated wind erosion decision-support tool. AERO incorporates land surface processes and sediment transport equations from existing wind erosion models and was designed for application with available national long-term monitoring datasets (e.g. USDI BLM Assessment, Inventory and Monitoring, USDA NRCS Natural Resources Inventory) and monitoring protocols. Ongoing AERO model calibration and validation are supported by geographically diverse data on wind erosion rates and land surface conditions collected by the new National Wind Erosion Research Network. Here we present the new AERO interface, describe parameterization of the underpinning wind erosion model, and provide a summary of the model applications across agricultural lands and rangelands in the United States.

Soil erosion evolution and spatial correlation analysis in a typical karst geomorphology using RUSLE with GIS

Science.gov (United States)

Zeng, Cheng; Wang, Shijie; Bai, Xiaoyong; Li, Yangbing; Tian, Yichao; Li, Yue; Wu, Luhua; Luo, Guangjie

2017-07-01

Although some scholars have studied soil erosion in karst landforms, analyses of the spatial and temporal evolution of soil erosion and correlation analyses with spatial elements have been insufficient. The lack of research has led to an inaccurate assessment of environmental effects, especially in the mountainous area of Wuling in China. Soil erosion and rocky desertification in this area influence the survival and sustainability of a population of 0.22 billion people. This paper analyzes the spatiotemporal evolution of soil erosion and explores its relationship with rocky desertification using GIS technology and the revised universal soil loss equation (RUSLE). Furthermore, this paper analyzes the relationship between soil erosion and major natural elements in southern China. The results are as follows: (1) from 2000 to 2013, the proportion of the area experiencing micro-erosion and mild erosion was at increasing risk in contrast to areas where moderate and high erosion are decreasing. The area changes in this time sequence reflect moderate to high levels of erosion tending to convert into micro-erosion and mild erosion. (2) The soil erosion area on the slope, at 15-35°, accounted for 60.59 % of the total erosion area, and the corresponding soil erosion accounted for 40.44 %. (3) The annual erosion rate in the karst region decreased much faster than in the non-karst region. Soil erosion in all of the rock outcrop areas indicates an improving trend, and dynamic changes in soil erosion significantly differ among the various lithological distribution belts. (4) The soil erosion rate decreased in the rocky desertification regions, to below moderate levels, but increased in the severe rocky desertification areas. The temporal and spatial variations in soil erosion gradually decreased in the study area. Differences in the spatial distribution between lithology and rocky desertification induced extensive soil loss. As rocky desertification became worse, the erosion

Soil erosion evolution and spatial correlation analysis in a typical karst geomorphology using RUSLE with GIS

Directory of Open Access Journals (Sweden)

C. Zeng

2017-07-01

Full Text Available Although some scholars have studied soil erosion in karst landforms, analyses of the spatial and temporal evolution of soil erosion and correlation analyses with spatial elements have been insufficient. The lack of research has led to an inaccurate assessment of environmental effects, especially in the mountainous area of Wuling in China. Soil erosion and rocky desertification in this area influence the survival and sustainability of a population of 0.22 billion people. This paper analyzes the spatiotemporal evolution of soil erosion and explores its relationship with rocky desertification using GIS technology and the revised universal soil loss equation (RUSLE. Furthermore, this paper analyzes the relationship between soil erosion and major natural elements in southern China. The results are as follows: (1 from 2000 to 2013, the proportion of the area experiencing micro-erosion and mild erosion was at increasing risk in contrast to areas where moderate and high erosion are decreasing. The area changes in this time sequence reflect moderate to high levels of erosion tending to convert into micro-erosion and mild erosion. (2 The soil erosion area on the slope, at 15–35°, accounted for 60.59 % of the total erosion area, and the corresponding soil erosion accounted for 40.44 %. (3 The annual erosion rate in the karst region decreased much faster than in the non-karst region. Soil erosion in all of the rock outcrop areas indicates an improving trend, and dynamic changes in soil erosion significantly differ among the various lithological distribution belts. (4 The soil erosion rate decreased in the rocky desertification regions, to below moderate levels, but increased in the severe rocky desertification areas. The temporal and spatial variations in soil erosion gradually decreased in the study area. Differences in the spatial distribution between lithology and rocky desertification induced extensive soil loss. As rocky desertification

A field experiment on the controls of sediment transport on bedrock erosion

Science.gov (United States)

Beer, A. R.; Turowski, J. M.; Fritschi, B.; Rieke-Zapp, D.; Campana, L.; Lavé, J.

2012-12-01

The earth`s surface is naturally shaped by interactions of physical and chemical processes. In mountainous regions with steep topography river incision fundamentally controls the geomorphic evolution of the whole landscape. There, erosion of exposed bedrock sections by fluvial sediment transport is an important mechanism forming mountain river channels. The links between bedload transport and bedrock erosion has been firmly established using laboratory experiments. However, there are only few field datasets linking discharge, sediment transport, impact energy and erosion that can be used for process understanding and model evaluation. To fill this gap, a new measuring setup has been commissioned to raise an appropriate simultaneous dataset of hydraulics, sediment transport and bedrock erosion at high temporal and spatial resolution. Two natural stone slabs were installed flush with the streambed of the Erlenbach, a gauged stream in the Swiss Pre-Alps. They are mounted upon force sensors recording vertical pressure und downstream shear caused by passing sediment particles. The sediment transport rates can be assessed using geophone plates and an automated moving basket system taking short-term sediment samples. These devices are located directly downstream of the stone slabs. Bedrock erosion rates are measured continuously with erosion sensors at sub-millimeter accuracy at three points on each slab. In addition, the whole slab topography is surveyed with photogrammetry and a structured-light 3D scanner after individual flood events. Since the installation in 2011, slab bedrock erosion has been observed during several transport events. We discuss the relation between hydraulics, bedload transport, resulting pressure forces on the stone slabs and erosion rates. The aim of the study is the derivation of an empirical process law for fluvial bedrock erosion driven by moving sediment particles.

Simulation of erosion in drilling tools for oil and gas industry

Energy Technology Data Exchange (ETDEWEB)

Arefi, B.; Settari, A. [Calgary Univ., AB (Canada); Angman, P. [Tesco Corp., Calgary, AB (Canada)

2004-07-01

Erosion in oil well drilling tools is a form of wear which occurs when fluid containing solid particles impacts a solid surface. The intensity of erosion is generally measured as the rate of material removal from the surface, and is expressed as E{sub r}, the weight of material removed by unit weight of impacting particles. Erosion can also be reduced by tool improvement and modification, thereby extending the life of drilling tools. To date, no attempt has been made to model the erosion phenomenon in drilling tools. This paper presents a newly developed erosion simulator which is the first design tool for the drilling industry. This work demonstrates that erosion can be simulated. A model was developed to calibrate the erosion coefficients for drilling tool conditions. The mechanism of erosion can be controlled by the impact velocity and angle. Algorithms were developed for transient simulation of the erosion of any surface in 2-dimensional geometry. The Erosion Simulator has been validated and calibrated against data provided by TESCO Corporation's casing drilling tools. The model has been shown to successfully predict and minimize erosion by modifying the tool geometry and metallurgy. 21 refs., 1 tab., 15 figs.

Estimates of soil erosion and deposition of cultivated soil of Nakhla watershed, Morocco, using 137Cs technique and calibration models

International Nuclear Information System (INIS)

Bouhlassa, S.; Moukhchane, M.; Aiachi, A.

2000-01-01

Despite the effective threat of erosion, for soil preservation and productivity in Morocco, there is still only limited information on rates of soil loss involved. This study is aimed to establish long-term erosion rates on cultivated land in the Nakhla watershed located in the north of the country, using 137 Cs technique. Two sampling strategies were adopted. The first is aimed at establishing areal estimates of erosion, whereas the second, based on a transect approach, intends to determine point erosion. Twenty-one cultivated sites and seven undisturbed sites apparently not affected by erosion or deposition were sampled to 35 cm depth. Nine cores were collected along the transect of 149 m length. The assessment of erosion rates with models varying in complexity from the simple Proportional Model to more complex Mass Balance Models which attempts to include the processes controlling the redistribution of 137 Cs in soil, enables us to demonstrate the significance of soil erosion problem on cultivated land. Erosion rates rises up to 50 t ha -1 yr -1 . The 137 Cs derived erosion rates provide a reliable representation of water erosion pattern in the area, and indicate the importance of tillage process on the redistribution of 137 Cs in soil. For aggrading sites a Constant Rate Supply (CRS) Model had been adapted and introduced to estimate easily the depositional rate. (author) [fr

Mechanisms of erosion in miocene clays from the Tudela formation (Bardenas Reales, Navarra, Spain); Mecanismos de erosion en arcillas miocenas de la Formacion Tudela (Bardenas Reales, Navarra, Espana)

Energy Technology Data Exchange (ETDEWEB)

Marin, C.; Desir, G.

2009-07-01

In Bardenas Reales area (located in the central-western part of the Ebro Depression) several erosion rates have been measured along the last years. The mean annual erosion rates are of 32 Tm/Ha/yr. Due to semiarid conditions, precipitation is irregularly distributed along the year with maximums on spring and autumn when the great erosion is produced. There are intensity and quality thresholds below which erosion does not take place. In Bardenas Reales some erosion processes act (mud slides and armoured mud balls among others). Mud slides are mobilised on spring when the sediment have reached its plastic limit and could slide due to heavy rains. Armored mud balls are produced by the enhancement of popcorn cracks that individualize clays cores which are rounded by water. The same kind of strong precipitation that mobilised mud slides is the responsible of armoured mud balls destruction because the conditions to its maintenance are very limited. (Author) 9 refs.

Using 10Be erosion rates and fluvial channel morphology to constrain fault throw rates in the southwestern Sacramento River Valley, California, USA

Science.gov (United States)

Cyr, A. J.

2013-12-01

The Sacramento - San Joaquin River Delta, California, USA, is a critical region for California water resources, agriculture, and threatened or endangered species. This landscape is affected by an extensive set of levees that enclose artificial islands created for agricultural use. In addition to their importance for sustaining agriculture, this levee system also supports extensive transport and power transmission infrastructure and urban/suburban development. These levees are susceptible to damage from even moderate ground shaking by either a large earthquake on one of the high-activity faults in the nearby San Francisco Bay region, or even a moderate earthquake on one of the low-activity faults in the Delta region itself. However, despite this danger the earthquake hazards in this region are poorly constrained due to our lack of understanding of faults in and near the Delta region. As part of an effort to better constrain the seismic hazard associated with known, but poorly constrained, faults in the region, a geomorphic analysis of the Dunnigan Hills, northwest of Woodland, CA, is being combined with cosmogenic 10Be catchment-averaged erosion rates. The Dunnigan Hills are a low-relief (maximum elevation 87 m) landscape generated by fault-bend folding above the west-vergent Sweitzer reverse fault that soles into a blind east-vergent reverse fault. These faults have been imaged by seismic reflection data, and local microseismicity indicates that this system is actively propagating to the east. However, the throw rates on the faults in this system remain unconstrained, despite the potential for significant shaking such as that experienced in the nearby April, 1892 earthquake sequence between Winters and Vacaville, Ca, ~25 km to the south, which has been estimated at magnitude 6.0 or greater. Geomorphic and cosmogenic 10Be analyses from 12 catchments draining the eastern flank of the Dunnigan Hills will be used to infer vertical rock uplift rates to better constrain

Interventions to improve gross motor performance in children with neurodevelopmental disorders: a meta-analysis.

Science.gov (United States)

Lucas, Barbara R; Elliott, Elizabeth J; Coggan, Sarah; Pinto, Rafael Z; Jirikowic, Tracy; McCoy, Sarah Westcott; Latimer, Jane

2016-11-29

Gross motor skills are fundamental to childhood development. The effectiveness of current physical therapy options for children with mild to moderate gross motor disorders is unknown. The aim of this study was to systematically review the literature to investigate the effectiveness of conservative interventions to improve gross motor performance in children with a range of neurodevelopmental disorders. A systematic review with meta-analysis was conducted. MEDLINE, EMBASE, AMED, CINAHL, PsycINFO, PEDro, Cochrane Collaboration, Google Scholar databases and clinical trial registries were searched. Published randomised controlled trials including children 3 to ≤18 years with (i) Developmental Coordination Disorder (DCD) or Cerebral Palsy (CP) (Gross Motor Function Classification System Level 1) or Developmental Delay or Minimal Acquired Brain Injury or Prematurity (gross motor outcomes obtained using a standardised assessment tool. Meta-analysis was performed to determine the pooled effect of intervention on gross motor function. Methodological quality and strength of meta-analysis recommendations were evaluated using PEDro and the GRADE approach respectively. Of 2513 papers, 9 met inclusion criteria including children with CP (n = 2) or DCD (n = 7) receiving 11 different interventions. Only two of 9 trials showed an effect for treatment. Using the least conservative trial outcomes a large beneficial effect of intervention was shown (SMD:-0.8; 95% CI:-1.1 to -0.5) with "very low quality" GRADE ratings. Using the most conservative trial outcomes there is no treatment effect (SMD:-0.1; 95% CI:-0.3 to 0.2) with "low quality" GRADE ratings. Study limitations included the small number and poor quality of the available trials. Although we found that some interventions with a task-orientated framework can improve gross motor outcomes in children with DCD or CP, these findings are limited by the very low quality of the available evidence. High quality intervention

[Research progress on wind erosion control with polyacrylamide (PAM).

Science.gov (United States)

Li, Yuan Yuan; Wang, Zhan Li

2016-03-01

Soil wind erosion is one of the main reasons for soil degradation in the northwest region of China. Polyacrylamide (PAM), as an efficient soil amendment, has gained extensive attention in recent years since it is effective in improving the structure of surface soil due to its special physical and chemical properties. This paper introduced the physical and chemical properties of PAM, reviewed the effects of PAM on soil wind erosion amount and threshold wind velocity, as well as the effect differences of PAM in soil wind erosion control under conditions of various methods and doses. Its effect was proved by comparing with other materials in detail. Furthermore, we analyzed the mecha-nism of wind erosion control with PAM according to its influence on soil physical characteristics. Comprehensive analysis showed that, although some problems existed in wind erosion control with (PAM), PAM as a sand fixation agent, can not only enhance the capacity of the soil resis-tance to wind erosion, but also improve soil physical properties to form better soil conditions. Besides, we proposed that combination of PAM and plant growth would increase the survival rate of plants greatly, control soil wind erosion in wind-erosive areas, and improve the quality of the ecological environment construction. Thus, PAM has practically important significance and wide application prospect in controlling soil wind erosion.

Spatial distribution of water erosion risk in a watershed with eucalyptus and Atlantic Forest

Directory of Open Access Journals (Sweden)

Junior Cesar Avanzi

2013-10-01

Full Text Available The process of water erosion occurs in watersheds throughout the world and it is strongly affected by anthropogenic influences. Thus, the knowledge of these processes is extremely necessary for planning of conservation efforts. This study was performed in an experimental forested watershed in order to predict the average potential annual soil loss by water erosion using the Universal Soil Loss Equation (USLE and a Geographic Information System (GIS, and then compared with soil loss tolerance. All the USLE factors were generated in a distributed approach employing a GIS tool. The layers were multiplied in the GIS framework in order to predict soil erosion rates. Results showed that the average soil loss was 6.2 Mg ha-1 yr-1. Relative to soil loss tolerance, 83% of the area had an erosion rate lesser than the tolerable value. According to soil loss classes, 49% of the watershed had erosion less than 2.5 Mg ha-1 yr-1. However, about 8.7% of the watershed had erosion rates greater than 15 Mg ha-1 yr-1, being mainly related to Plinthosol soil class and roads, thus requiring special attention for the improvement of sustainable management practices for such areas. Eucalyptus cultivation was found to have soil loss greater than Atlantic Forest. Thus, an effort should be made to bring the erosion rates closer to the native forest. Implementation of the USLE model in a GIS framework was found to be a simple and useful tool for predicting the spatial variation of soil erosion risk and identifying critical areas for conservation efforts.

Erosion of lithium coatings on TZM molybdenum and graphite during high-flux plasma bombardment

NARCIS (Netherlands)

Abrams, T.; Jaworski, M. A.; Kaita, R.; Stotler, D. P.; De Temmerman, G.; Morgan, T. W.; van den Berg, M. A.; van der Meiden, H. J.

2014-01-01

Abstract The rate at which Li films will erode under plasma bombardment in the NSTX-U divertor is currently unknown. It is important to characterize this erosion rate so that the coatings can be replenished before they are completely depleted. An empirical formula for the Li erosion rate as a

Target fabrication using laser and spark erosion machining

International Nuclear Information System (INIS)

Clement, X.; Coudeville, A.; Eyharts, P.; Perrine, J.P.; Rouillard, R.

1982-01-01

Fabrication of laser fusion targets requires a number of special techniques. We have developed both laser and spark erosion machining to produce minute parts of complex targets. A high repetition rate YAG laser at double frequency is used to etch various materials. For example, marks or patterns are often necessary on structured or advanced targets. The laser is also used to thin down plastic coated stalks. A spark erosion system has proved to be a versatile tool and we describe current fabrication processes like cutting, drilling, and ultra precise machining. Spark erosion has interesting features for target fabrication: it is a highly controllable and reproducible technique as well as relatively inexpensive

Effects of traditional land transactions on soil erosion and land degradation

OpenAIRE

Leduka, R.C.

1998-01-01

A research report on the effects of traditional land transactions on soil erosion and land degradation in Lesotho. This report focuses on the land transactions in Lesotho and how these transaction affect the growing erosion rates of the soil.

Innovative procedure for the determination of gross-alpha/gross-beta activities in drinking water

International Nuclear Information System (INIS)

Wisser, S.; Frenzel, E.; Dittmer, M.

2006-01-01

An alternative sample preparation method for the determination of gross-alpha/beta activity concentrations in drinking water is introduced in this paper. After the freeze-drying of tap water samples, determination by liquid scintillation counting can be applied utilizing alpha/beta separation. It has been shown that there is no adsorption or loss of solid radionuclides during the freeze-drying procedure. However, the samples have to be measured quickly after the preparation since the ingrowth of daughter isotopes negatively effects the measurement. The limits of detection for gross-alpha and gross-beta activity are in the range 25-210 mBq/l, respectively, for a measurement time of only 8-9 h

Study of corrosive-erosive wear behaviour of Al6061/albite composites

International Nuclear Information System (INIS)

Sharma, S.C.; Krishna, M.; Murthy, H.N. Narasimha; Tarachandra, R.; Satyamoorthy, M.; Bhattacharyya, D.

2006-01-01

This investigation analyses the influence of dispersed alumina particles on the wear behaviour of the Al/albite composites in a corrosive environment. The composites were prepared by modified pressure die-casting technique. The corrosive-erosive wear experiments were carried out on a proprietary corrosion-erosion wear tester to study the wear characteristics of the composites. The slurry was made up of water and alumina (size: 90-150 μm, proportion: 0-30 wt.%), while H 2 SO 4 (0.01, 0.1 and 1N) was added to create the corrosive conditions. Experiments were arranged to test the relationships among the corrosive-erosive wear rate, concentrations of H 2 SO 4 and alumina in the slurry, weight percent of albite in the composite, erosion speed and distance. Wear rate varies marginally at low speeds but sharply increases at higher speeds. The corrosive wear rate logarithmically increased with the increasing concentration of the corrosive medium. The effect of abrasive particles and corrosion medium on the wear behaviour of the composite is explained experimentally, theoretically and using scanning electron microscopy

Validating the Rett Syndrome Gross Motor Scale

DEFF Research Database (Denmark)

Downs, Jenny; Stahlhut, Michelle; Wong, Kingsley

2016-01-01

.93-0.98). The standard error of measurement for the total score was 2 points and we would be 95% confident that a change 4 points in the 45-point scale would be greater than within-subject measurement error. The Rett Syndrome Gross Motor Scale could be an appropriate measure of gross motor skills in clinical practice......Rett syndrome is a pervasive neurodevelopmental disorder associated with a pathogenic mutation on the MECP2 gene. Impaired movement is a fundamental component and the Rett Syndrome Gross Motor Scale was developed to measure gross motor abilities in this population. The current study investigated...... the validity and reliability of the Rett Syndrome Gross Motor Scale. Video data showing gross motor abilities supplemented with parent report data was collected for 255 girls and women registered with the Australian Rett Syndrome Database, and the factor structure and relationships between motor scores, age...

Soil erosion and its control in Chile - An overview

International Nuclear Information System (INIS)

Ellies, A.

2000-01-01

Accelerate erosion in Chile is a consequence from land use that degrade soil such as compaction, loss of organic matter and soil structure. The erosion is favored by the very hilly landscape of the country that increases erosivity index and the high erodibility given by an elevated annual rate of rainfall with irregular distribution. Several experiences have demonstrated that adequate crop management and crop rotations can minimize erosion. The most effective control is achieved conserving and improving soil structure with management systems that include regular use of soil-improving crops, return of crop residues and tillage practices, thus avoiding unnecessary breakdown soil or compacted soil structure. Conservation tillage increased organic matter levels improving stabile soil structure, aeration and infiltration. (author) [es

EVALUATION OF SOIL EROSION IN REGHIN HILLS USING THE USLE METHOD

Directory of Open Access Journals (Sweden)

J. SZILAGYI

2016-03-01

Full Text Available Soil erosion is one of the main causes of degradation of large areas of agricultural land, causing great economic loss by removing fertile soil. The Universal Soil Loss Equation (USLE predicts the long term average annual rate of erosion on a field slope based on rainfall pattern, soil type, topography, crop system and management practices but does not however predict the soil loss resulting from gully erosion.

Water erosion of dystrophic Red Latosols (Oxisols

Directory of Open Access Journals (Sweden)

Joaquim Ernesto Bernardes Ayer

2015-06-01

Full Text Available In their natural state, Latosols (Oxisols present great stability and resistance to erosion, being the most abundant and used soils for farming and cattle raising activities in southern Minas Gerais State, Brazil. However, along the last one hundred years, they have been submitted to intensive cultivation and managements which favor water erosion. This study aimed to estimate the water erosion rates of dystrophic Red Latosols from the Revised Universal Soil Loss Equation, compared with the soil loss tolerance limits, and assess the impact on water erosion of the managements more common in the region, by alternative conservation management simulation. Soil loss tolerance limits ranged from 8.94 Mg ha-1 year-1 to 9.99 Mg ha-1 year-1, with the study area presenting a susceptibility of soil loss of 23.86 Mg year-1, with an average rate of 8.40 Mg ha-1 year-1, corresponding to 34.80 % of the area with values above the soil loss tolerance limit. The biggest annual losses occur in areas with use and management of eucalyptus grown downhill (30.67 Mg ha-1 year-1 and pasture under continuous occupancy (11.10 Mg ha-1 year-1. However, when the average loss per type of use is considered, the areas more susceptible to water erosion are those with potato and eucalyptus crops, grown downhill, and those in bare soil. Nevertheless, in the simulated conservation management scenario, the average losses would be drastically reduced (8.40 Mg ha-1 year-1 to 2.84 Mg ha-1 year-1 and only 4.00 % of the area with soil loss would remain above the tolerance limits.

Surface biosolids application: effects on infiltration, erosion, and soil organic carbon in Chihuahuan Desert grasslands and shrublands.

Science.gov (United States)

Moffet, C A; Zartman, R E; Wester, D B; Sosebee, R E

2005-01-01

Land application of biosolids is a beneficial-use practice whose ecological effects depend in part on hydrological effects. Biosolids were surface-applied to square 0.5-m2 plots at four rates (0, 7, 34, and 90 dry Mg ha(-1)) on each of three soil-cover combinations in Chihuahuan Desert grassland and shrubland. Infiltration and erosion were measured during two seasons for three biosolids post-application ages. Infiltration was measured during eight periods of a 30-min simulated rain. Biosolids application affected infiltration rate, cumulative infiltration, and erosion. Infiltration increased with increasing biosolids application rate. Application of biosolids at 90 dry Mg ha(-1) increased steady-state infiltration rate by 1.9 to 7.9 cm h(-1). Most of the measured differences in runoff among biosolids application rates were too large to be the result of interception losses and/or increased hydraulic gradient due to increased roughness. Soil erosion was reduced by the application of biosolids; however, the extent of reduction in erosion depended on the initial erodibility of the site. Typically, the greatest marginal reductions in erosion were achieved at the lower biosolids application rates (7 and 34 dry Mg ha(-1)); the difference in erosion between 34 and 90 dry Mg ha(-1) biosolids application rates was not significant. Surface application of biosolids has important hydrological consequences on runoff and soil erosion in desert grasslands that depend on the rate of biosolids applied, and the site and biosolids characteristics.

Gastroesophageal reflux is not associated with dental erosion in children.

Science.gov (United States)

Wild, Yvette K; Heyman, Melvin B; Vittinghoff, Eric; Dalal, Deepal H; Wojcicki, Janet M; Clark, Ann L; Rechmann, Beate; Rechmann, Peter

2011-11-01

Dental erosion is a complication of gastroesophageal reflux (GER) in adults; in children, it is not clear if GER has a role in dental pathologic conditions. Dietary intake, oral hygiene, high bacterial load, and decreased salivary flow might contribute independently to GER development or dental erosion, but their potential involvement in dental erosion from GER is not understood. We investigated the prevalence of dental erosion among children with and without GER symptoms, and whether salivary flow rate or bacterial load contribute to location-specific dental erosion. We performed a cross-sectional study of 59 children (ages, 9-17 y) with symptoms of GER and 20 asymptomatic children (controls); all completed a questionnaire on dietary exposure. Permanent teeth were examined for erosion into dentin, erosion locations, and affected surfaces. The dentist was not aware of GER status, and the gastroenterologist was not aware of dental status. Stimulated salivary flow was measured and salivary bacterial load was calculated for total bacteria, Streptococcus mutans, and Lactobacilli. Controlling for age, dietary intake, and oral hygiene, there was no association between GER symptoms and dental erosion by tooth location or affected surface. Salivary flow did not correlate with GER symptoms or erosion. Erosion location and surface were independent of total bacteria and levels of Streptococcus mutans and Lactobacilli. Location-specific dental erosion is not associated with GER, salivary flow, or bacterial load. Prospective studies are required to determine the pathogenesis of GER-associated dental erosion and the relationship between dental caries to GER and dental erosion. Copyright © 2011 AGA Institute. Published by Elsevier Inc. All rights reserved.

Regional shoreline change and coastal erosion hazards in Arctic Alaska

Science.gov (United States)

Gibbs, Ann E.; Richmond, Bruce M.; Erikson, Li H.; Harden, E. Lynne; Wallendorf, Louise

2011-01-01

Historical shoreline positions along the mainland Beaufort Sea coast of Alaska were digitized and analyzed to determine the long-term rate of change. Average shoreline change rates and ranges from 1947 to the mid-2000s were determined every 50 meters between Barrow and Demarcation Point, at the U.S.-Canadian border. Results show that shoreline change rates are highly variable along the coast, with an average regional shoreline change rate of-2.0 m/yr and localized rates of up to -19 m/yr. The highest erosion rates were observed at headlands, points, and associated with breached thermokarst lakes. Areas of accretion were limited, and generally associated with spit extension and minor beach accretion. In general, erosion rates increase from east to west, with overall higher rates east of Harrison Bay.

Sensitivity of mountain ecosystems to human-accelerated soil erosion. Contrasting geomorphic response between tropical and semi-arid ecosystems.

Science.gov (United States)

Vanacker, Veerle; Bellin, Nicolas; Schoonejans, Jerome; Molina, Armando; Kubik, Peter W.

2014-05-01

Human-induced land cover changes are causing important adverse effects on the ecological services rendered by mountain ecosystems, and the number of case-studies of the impact of humans on soil erosion and sediment yield has mounted rapidly. A modelling framework that is specifically adapted to mountain environments is currently lacking. Most studies make use of general river basin models that were originally parameterized and calibrated for temperate, low relief landscapes. Transposing these modelling concepts directly to steep environments with shallow and stony soils often leads to unrealistic model predictions, as model input parameters are rarely calibrated for the range of environmental conditions found in mountain regions. Here, we present a conceptual model that evaluates erosion regulation as a function of human disturbances in vegetation cover. The basic idea behind this model is that soil erosion mechanisms are independent of human impact, but that the frequency-magnitude distributions of erosion rates change as a response to human disturbances. Pre-disturbance (or natural) erosion rates are derived from in-situ produced 10Be concentrations in river sediment, while post-disturbance (or modern) erosion rates are derived from sedimentation rates in small catchments. In its simplicity, the model uses vegetation cover change as a proxy of human disturbance in a given vegetation system. The model is then calibrated with field measurements from two mountainous sites with strongly different vegetation dynamics, climatic and geological settings: the Tropical Andes, and the Spanish Betic Cordillera. Natural erosion processes are important in mountainous sites, and natural erosion benchmarks are primordial to assess human-induced changes in erosion rates. While the Spanish Betic Cordillera is commonly characterized as a degraded landscape, there is no significant change in erosion due to human disturbance for uncultivated sites. The opposite is true for the

Sediment contributions from floodplains and legacy sediments to Piedmont streams of Baltimore County, Maryland

Science.gov (United States)

Donovan, Mitchell; Miller, Andrew; Baker, Matthew; Gellis, Allen C.

2015-01-01

Disparity between watershed erosion rates and downstream sediment delivery has remained an important theme in geomorphology for many decades, with the role of floodplains in sediment storage as a common focus. In the Piedmont Province of the eastern USA, upland deforestation and agricultural land use following European settlement led to accumulation of thick packages of overbank sediment in valley bottoms, commonly referred to as legacy deposits. Previous authors have argued that legacy deposits represent a potentially important source of modern sediment loads following remobilization by lateral migration and progressive channel widening. This paper seeks to quantify (1) rates of sediment remobilization from Baltimore County floodplains by channel migration and bank erosion, (2) proportions of streambank sediment derived from legacy deposits, and (3) potential contribution of net streambank erosion and legacy sediments to downstream sediment yield within the Mid-Atlantic Piedmont.We calculated measurable gross erosion and deposition rates within the fluvial corridor along 40 valley segments from 18 watersheds with drainage areas between 0.18 and 155 km2 in Baltimore County, Maryland. We compared stream channel and floodplain morphology from lidar-based digital elevation data collected in 2005 with channel positions recorded on 1:2400 scale topographic maps from 1959–1961 in order to quantify 44–46 years of channel change. Sediment bulk density and particle size distributions were characterized from streambank and channel deposit samples and used for volume to mass conversions and for comparison with other sediment sources.Average annual lateral migration rates ranged from 0.04 to 0.19 m/y, which represented an annual migration of 2.5% (0.9–4.4%) channel width across all study segments, suggesting that channel dimensions may be used as reasonable predictors of bank erosion rates. Gross bank erosion rates varied from 43 to 310 Mg/km/y (median = 114) and

Validating the use of 137Cs and 210Pbex measurements to estimate rates of soil loss from cultivated land in southern Italy

International Nuclear Information System (INIS)

Porto, Paolo; Walling, Des E.

2012-01-01

Soil erosion represents an important threat to the long-term sustainability of agriculture and forestry in many areas of the world, including southern Italy. Numerous models and prediction procedures have been developed to estimate rates of soil loss and soil redistribution, based on the local topography, hydrometeorology, soil type and land management. However, there remains an important need for empirical measurements to provide a basis for validating and calibrating such models and prediction procedures as well as to support specific investigations and experiments. In this context, erosion plots provide useful information on gross rates of soil loss, but are unable to document the efficiency of the onward transfer of the eroded sediment within a field and towards the stream system, and thus net rates of soil loss from larger areas. The use of environmental radionuclides, particularly caesium-137 ( 137 Cs) and excess lead-210 ( 210 Pb ex ), as a means of estimating rates of soil erosion and deposition has attracted increasing attention in recent years and the approach has now been recognised as possessing several important advantages. In order to provide further confirmation of the validity of the estimates of longer-term erosion and soil redistribution rates provided by 137 Cs and 210 Pb ex measurements, there is a need for studies aimed explicitly at validating the results obtained. In this context, the authors directed attention to the potential offered by a set of small erosion plots located near Reggio Calabria in southern Italy, for validating estimates of soil loss provided by 137 Cs and 210 Pb ex measurements. A preliminary assessment suggested that, notwithstanding the limitations and constraints involved, a worthwhile investigation aimed at validating the use of 137 Cs and 210 Pb ex measurements to estimate rates of soil loss from cultivated land could be undertaken. The results demonstrate a close consistency between the measured rates of soil loss and