Eroded Soil Particles Research Articles

Flow field analysis and particle erosion of tunnel‐slope systems under coupling between runoff and fast (slow) seepage

AbstractThe presence of particles on the surface of a tunnel slope renders it susceptible to erosion by water flow, which is a major cause of soil and water loss. In this study, a nonlinear mathematical model and a mechanical equilibrium model are developed to investigate the distribution of flow fields and particle motion characteristics of tunnel slopes, respectively. The mathematical model of flow fields comprises three parts: a runoff region, a highly permeable soil layer, and a weakly permeable soil layer. The Navier‒Stokes equation controls fluid motion in the runoff region, while the Brinkman‐extended Darcy equation governs fast and slow seepage in the highly and weakly permeable soil layers, respectively. Analytical solutions are derived for the velocity profile and shear stress expression of the model flow field under the boundary condition of continuous transition of velocity and stress at the fluid‒solid interface. The shear stress distribution shows that the shear stress at the tunnel‐slope surface is the largest, followed by the shear stress of the soil interface, indicating that particles in these two locations are most vulnerable to erosion. A mechanical equilibrium model of sliding and rolling of single particles is established at the fluid‒solid interface, and the safety factor of particle motion (sliding and rolling) is derived. Sensitivity analysis shows that by increasing the runoff depth, slope angle, and soil permeability, the erosion of soil particles will be aggravated on the tunnel‐slope surface, but by increasing the particle diameter, particle‐specific gravity, and particle stacking angle, the erosion resistance ability of the tunnel‐slope surface particles will be enhanced. This study can serve as a reference for the analysis of surface soil and water loss in tunnel‐slope systems.

Soil structure and glyphosate fate under no-till management in the Pampa region. II. Glyphosate and AMPA persistence and spatial distribution in the long-term. A conceptual model

Glyphosate and AMPA were measured in a no-tilled (NT) soil and in the runoff resulting from the rain simulation carried out after 270 days of the application of the herbicide. Glyphosate concentration was in low values in runoff water but was not detected in the soil. In contrast, AMPA was found only in soil samples (same LOD/LOQ for both molecules). These intriguing results, on the one hand have led us to develop a conceptual model explaining the dynamics of glyphosate in NT soils with strongly developed platy structures resulting from this soil management, and, on the other hand, to underline the requirement of certain methodological precautions when analyzing properties of such stratified surface horizons. In our model, glyphosate was mostly degraded into AMPA although a small part remained adsorbed and trapped in the plates in the upper soil layer. In the field test, platy aggregates were destroyed by the raindrop impacts, glyphosate was washed off and transported in solution or bound to eroded soil particles. Glyphosate was not detected in soil analysis mainly due to the reduced volume of the surface plates in the total sample and, to a lesser extent, some loss of surface soil material during samples preparation due to its high content of roots and plant debris. In contrast, AMPA leached preferentially and became trapped in the micropores of the dense layer. Therefore, its absence in the runoff and its relatively high proportion in the soil would be due to its accumulation and preservation in the lower portion of the A horizon. The long persistence of AMPA would be explained not only by its physical occlusion in small pores preventing microbial accessibility, but also by a low diffusivity of oxygen and water restricting biotic and abiotic degradation processes. It is suggested that an integrative approach considering both the physical behaviour and the architecture of the soil at different scales in the laboratory and in the field, can contribute to understanding the fate of glyphosate and other agrochemicals in NT soils.

Flow-3D Analysis on the Scour Characteristics of Artificial Reef-Installed Soils with Various Particle Sizes

Artificial reef-installed seabeds may have significantly different scouring patterns depending on the ground conditions, such as the soil particle size, even though the flow velocity and water depth are similar. In this study, the scour characteristics of the ground were determined using Flow-3D to evaluate the geotechnical stability of artificial reefs installed on various seabeds, such as sand, silt, and clay. The analysis results indicated that the smaller the particle size of the soil, the larger the amount of scour that occurs around the artificial reef and the longer it takes to reach an equilibrium state. However, eroded soil particles were deposited on the rear part of the artificial reef as the soil particle size increased. The maximum scour depth and average particle size showed a non-linear relationship. In particular, the maximum scour depth increased significantly in fine-grained soils.

Modeling of erosion processes in open channels

Objective. The aim of the study is to model erosion processes in open channels.Method. A stochastic approach is applied to the calculation of parameters and the construction of models of individual stages of the erosion process: disruption, weighing and transport of eroded soil particles by a turbulent flow. Result. A technique has been developed for predicting the general erosion of riverbeds and canals, composed of homogeneous and heterogeneous non-cohesive soils. Approbation of the developed technique on the material of laboratory and field studies confirmed its satisfactory accuracy in a wide range of hydraulic conditions and soil granulometric compositions. Conclusion. The principles of developing a model of erosion processes in open channels, the modular structure of the calculation algorithms and programs compiled on its basis, allow us to continuously improve the methods for calculating individual parameters of the erosion process and make adjustments to the corresponding modules of algorithms.

Transport and fate of antibiotics in a typical aqua-agricultural catchment explained by rainfall events: Implications for catchment management

Antibiotics receive many concerns since their negative environmental impacts are being revealed, especially in aqua-agricultural areas. Rainfall events are responsible for transferring excess contaminants to receiving waters. However, the understanding of antibiotics transport and fate responding to rainfall events was constrained by limited event-based data and lacking integrated consideration of dissolved and particulate forms. We developed an intensive monitoring strategy to capture responses of fourteen antibiotics to different types of rainfall events and inter-event low flow periods. Pollutant-rich suspended particles, as high as 1471 ng/g, were found in low flow periods while the very heavy rainfall events and consecutive rainfall events stimulated the release of antibiotics from eroded soil particles to river water. Therefore, these rainfall events drove radical increase of dissolved antibiotic concentration up to 592 ng/L and total flux up to 25.0 g/d. Sulfonamides were particularly sensitive to rainfall events because of their residues in manure-applied agricultural lands. Transport dynamics of most antibiotics were accretion whereas only clarithromycin exhibited a dilution pattern by concentration-discharge relationships. Aquaculture ponds were inferred to significantly contribute tetracycline, oxytetracycline, and clarithromycin. Conventional contaminants were compared to discriminate potential sources of antibiotics and imply effective catchment management. The results provided novel insights into event-based drivers and dynamics of antibiotics and could lead to appropriate management strategy.

How agricultural management practices affect nitrogen transportation and redistribution under the drying-rewetting process of loessial sloping lands?

Nitrogen (N) is one of the most common macronutrients applied to soil to promote crop productivity, but no more information can be found in the effect of different management practices on the surface pathways of N loss in the process of drying-rewetting alternation. In this study, the laboratory intermittent rainstorms were adopted to quantify the mechanism and implication of agricultural interventions on slope runoff N fractions. Results indicate that: (i) The threshold ranges of sediment yield rate under 0% and 3% biochar vegetated slopes are generally smaller than that of bare slope while 6% biochar is just the opposite, but all of them increased with increased rainfall intensity. Horizontal ridge and vegetation strips show good performance on reducing sediment and fixing N under 0–3% biochar application, but the sediment and N loss increased dramatically when the biochar application increased from 3% to 6%. (ii) N loss can be aggravated from P3 (conventional flat planting + 3% biochar) to H6 (horizontal ridge planting + 6% biochar) on 10° bare slope and 120 mm·h-1 heavy rainstorm due to the drying-wetting cycle and the redistribution of eroded soil particles, but N loss on 10° vegetated slopes experienced overall significant decreases because vegetation combined with horizontal ridge or appropriate biochar curtail erosion and retain sediment. (iii) The hydrological pathways transporting various N fractions vary with different management practices. e.g., the particulate fractions in H6 of vegetated slope is 90.29% while 44.88% in bare slope under 120 mm·h-1, indicating biochar in excessive application would increase the loss of particulate nutrients under heavy rainstorms even with vegetation and horizontal ridge. The results will be helpful to parameterize from a lower scale or disaggregate from a higher scale in the runoff nutrient management of agroecological systems of the Loess Plateau.

Seasonal effect of land use management on gill histopathology of Barbel and Douro Nase in a Portuguese watershed

The Vilariça River (located in the northeast of Portugal) is inserted in an agricultural basin and it was chosen to replace the spawning grounds for fish, that was lost due to the construction of dams in the Sabor River. Thus, it is essential to study the effect of agricultural practices on water quality and in the health status of fish. The barbel (Luciobarbus bocagei) and Douro nase (Pseudochondrostoma duriense) were the selected species and the work was developed in two seasons (Summer 2016 and Winter 2017). For that, the histopathological changes of fish gill were used as biomarkers, through a semi-quantitative approach that considers the injuries severity. And the water quality assessment criteria followed the methodologies proposed for classifying the status of surface water bodies from Portugal. The current study showed severe histopathological changes in both species and both seasons, and the water was classified as polluted and extremely polluted in Summer and Winter respectively. The pollution in Summer was due to high temperatures, low dissolved oxygen and major concentration of As and Mn, and in Winter is due to the high concentration of Total Suspended Solids, nitrites and Cd. The increase of values of physico-chemical parameters on the water was caused by the less streamflow and excessive agricultural fertilization in Summer which arrive the river by irrigation, and by the erosion of soil particles with heavy metals associated in Winter. Also, the canonical analysis showed that physico-chemical parameters concentrations in Summer justify the major prevalence of aneurism in barbel and exudate in nase and Winter the major prevalence of hypertrophy in barbel. In conclusion, the study showed that the gill injuries of barbel and Douro nase was correlated with the water quality and it is influenced by seasonal agricultural practices and the flow regime.

Numerical modelling of internal erosion during hydrate dissociation based on multiphase mixture theory

SummaryIt has been reported that sand production, which is a simultaneous production of soil particles along with gas and water into a production well, forced to terminate the operation during the world's first offshore methane production test from hydrate‐bearing sediments in the Eastern Nankai Tough. The sand production is induced by internal erosion, which is the detachment and migration of soil particles from soil skeleton due to seepage flow. The inflow of the eroded soil particles into the production well leads to damage of the production devices. In the present study, a numerical model to predict the chemo‐thermo‐mechanically coupled behavior including internal erosion during hydrate dissociation has been formulated based on the multiphase mixture theory. In the proposed model, the internal erosion is expressed as mass transition of soil particles from soil skeleton to the fluidized soil particles. Since the internal erosion is considered to depend on the soil particle size, mass of soil particles are divided into several groups that have different representative particle diameters, and the constitutive equations for the onset condition and the mass transition rate of the internal erosion are formulated for each group. Also, transportation of soil particles in the liquid phase is formulated for each particle size group in the proposed model. Finally, a simulation of the methane gas production from the hydrate‐bearing sediment by depressurization method is presented, and the internal erosion and the dissociation behavior are discussed.

Land use strongly influences soil organic carbon and bacterial community export in runoff in tropical uplands‐

AbstractRapid development and associated land‐use change have resulted in increased soil erosion and widespread land degradation in tropical ecosystems. Precipitation‐induced soil erosion causes the export of soil organic carbon (SOC) and the associated bacterial community affecting soil quality and functioning. We assessed the transfer of SOC and soil bacterial diversity and functions in surface water runoff from different land uses: Teak with and without understory (TW and TWO, respectively) and upland rice (UR) in a tropical, upland catchment during a simulated rain event. Total suspended sediment (TSS) concentration was higher in TWO (1.23 ± 0.21 g L−1) than in TW (0.37 ± 0.16 g L−1) and UR (0.44 ± 0.2 g L−1), whereas dissolved organic carbon (DOC) concentration was lower under TWO (3.8 ± 0.7 mg L−1) than under TW or UR (13.4 ± 7.5 and 9.57 ± 4.8 mg L−1, respectively). Runoff from TWO harboured the highest proportion of bacterial taxa common to soil (27% and 29.5%) as compared with TW (22.8% and 13%) and UR (17.3% and 7%) for both particle attached and free‐living fractions, respectively. Bacterial community export in surface runoff was driven by changes in DOC and TSS, suggesting that eroded soil particles simultaneously carry organic carbon and attached bacterial taxa in surface runoff. Consequently, the export of soil functional groups relating to organic carbon degradation and nitrogen cycle was higher under TWO than in TW or UR. Our results underline that teak plantations with unsustainable practices such as the removal of understory degrades soil functions and accelerates land degradation through soil erosion and surface runoff on the long term.

NO EROSION CRITERION FOR GRANULAR FILTERS BASED ON CONSTRICTION SIZE – AN EXPERIMENTAL STUDY

Filters are provided in embankments in order to arrest the eroded soil particles that are carried by the seepage water .Current design method of graded filters was developed by Terzaghi which is based on the particle size distribution of the filter material and the base material. This paper presents an attempt to develop filter design criteria in relation to constriction size in gravel filters. It is an alternative approach from the conventional filter design criteria of Terzaghi, which is based on the particle size distribution of the filter media and base material. In his study a criterion for filter to prevent erosion is proposed based on the constriction size distribution of the filter media. The proposed constriction size-based criterion, C10/d95 2 directly compares the controlling constriction size (C10) with the specific representative base size (d95) defines the effectiveness of filters, hence it is a more effective method compared to the Terzaghi criterion (D15 /d85<5) which is based purely on particle size. This ratio explains the behavior of filters more clearly and is proved by a number of tests on various base-filter combinations. When compared to Terzaghi criteria, constriction size distribution criterion proves to be more effective.

Experimental investigation of interfacial erosion on culvert-soil interface in earth dams

The erosion of soil particles within a dam, by water that seeps through the dam, is one of the most common causes of failure in levees and earth dams. This phenomenon can be more complex and dangerous when interacting with internally affiliated structures, such as water-supply culverts, due to the potential development of seepage channels through the weak interfaces. However, the erosion in this particular case has not been thoroughly investigated. In this paper, therefore, a seepage apparatus is designed to simulate and investigate the progressive failure mechanism of interfacial erosion on the culvert-soil interface of earth dams. This further leads to a detailed investigation of the threshold and failure hydraulic gradients of interfacial erosion by accounting for the influence of two critical geotechnical factors, i.e., the degree of compaction and the clay content. Furthermore, numerical analyses are carried out to reproduce the seepage-induced interface stress-displacement behaviour, as a supplement to the experimental investigations. Finally, emphasis is placed on studying the protective effects of two typical mitigation measures (the filter layer and impermeable rings) against interfacial erosion. The main conclusions can be drawn as follows: (1) The interfacial erosion in the unprotected cases shows a three-stage progressive failure as the hydraulic gradient increases, i.e., the stable, transition and failure stages, while that of the protected cases shows a four-stage failure, i.e., the stable, transition, hardening and failure stages. (2) The threshold and failure hydraulic gradients of interfacial erosion are found to be in the ranges of 0.771–1.467 and 0.974–1.994, respectively, for the investigated cases. (3) The critical hydraulic gradients are seen to be in a nonlinear relation with the degree of compaction or the clay content. (4) The experimental results show the effective protective effects of employing the two mitigation measures against interfacial erosion by blocking the formed seepage channels. The research provides critical references for the safety assessment of embankment dams when considering interfacial erosion failures at culvert-soil interfaces.

Monitoring and Assessment of Water Retention Measures in Agricultural Land

One of the most interesting events, from the environmental impact point of view, is the huge storm rainfall at which soil degradation processes occur. In Slovakia, agricultural areas with a higher slope have been recently increasingly denudated by water erosion processes. Areas having regular problems with muddy floods and denudation of soil particles have been currently identified. This phenomenon has long-term adverse consequences in the agricultural landscape, especially the decline in soil fertility, the influence on soil type and the reduction of depth of the soil profile. In the case of storm rainfall or long-term precipitation, soil particles are being transported and deposited at the foot of the slope, but in many cases the large amounts of sediment are transported by water in the form of muddy floods, while putting settlements and industrial zones at risk, along with contamination and clogging of watercourses and water reservoirs. These unfavourable phenomena may be prevented by appropriate management and application of technical measures, such as water level ditches, erosion-control weirs, terraces and others. The study deals with determination of the soil loss and denudation of soil particles caused by water erosion, as well as with determination of the volume of the surface runoff created by the regional torrential rains in the area of the village of Sobotište. The research is based on the analysis of flood and erosion-control measures implemented in this area. Monitoring of these level ditches for protection against muddy floods has been carried out since 2015 using UAV technology and terrestrial laser scanning. Monitoring is aimed on determination of the volume of the ditch, changes in its capacity and shape in each year. The study evaluates both the effectiveness of these measures to reduce the surface runoff as well as the amount of eroded soil particles depending on climatological conditions. The results of the research point to the good efficiency of these measures; however, in conjunction with belt crops cultivation they could form a comprehensive flood and erosion-control protection to eliminate the muddy floods and protect the settlements from surrounding slopes.

A mathematical model of reservoir sediment quality prediction based on land-use and erosion processes in watershed

The aim of this paper is to propose a mathematical model for determining of total nitrogen (N) and phosphorus (P) content in eroded soil particles with emphasis on prediction of bottom sediment quality in reservoirs. The adsorbed nutrient concentrations are calculated using the Universal Soil Loss Equation (USLE) extended by the determination of the average soil nutrient concentration in top soils. The average annual vegetation and management factor is divided into five periods of the cropping cycle. For selected plants, the average plant nutrient uptake divided into five cropping periods is also proposed. The average nutrient concentrations in eroded soil particles in adsorbed form are modified by sediment enrichment ratio to obtain the total nutrient content in transported soil particles. The model was designed for the conditions of north-eastern Slovakia. The study was carried out in the agricultural basin of the small water reservoir Klusov.

Reduction of soil erosion and mercury losses in agroforestry systems compared to forests and cultivated fields in the Brazilian Amazon

In addition to causing physical degradation and nutrient depletion, erosion of cultivated soils in the Amazon affects aquatic ecosystems through the release of natural soil mercury (Hg) towards lakes and rivers. While traditional agriculture is generally cited as being among the main causes of soil erosion, agroforestry practices are increasingly appreciated for soil conservation. This study was carried out in family farms of the rural Tapajós region (Brazil) and aimed at evaluating soil erosion and associated Hg release for three land uses. Soils, runoff water and eroded sediments were collected at three sites representing a land cover gradient: a recently burnt short-cycle cropping system (SCC), a 2-year-old agroforestry system (AFS) and a mature forest (F). At each site, two PVC soil erosion plots (each composed of three 2 × 5 m isolated subplots) were implemented on steep and moderate slopes respectively. Sampling was done after each of the 20 rain events that occurred during a 1-month study period, in the peak of the 2011 rain season. Runoff volume and rate, as well as eroded soil particles with their Hg and cation concentrations were determined. Total Hg and cation losses were then calculated for each subplot. Erosion processes were dominated by land use type over rainfall or soil slope. Eroded soil particles, as well as the amount of Hg and cations (CaMgK) mobilized at the AFS site were similar to those at the F site, but significantly lower than those at the SCC site (p < 0.0001). Erosion reduction at the AFS site was mainly attributed to the ground cover plants characterizing the recently established system. Moreover, edaphic change throughout AFS and F soil profiles differed from the SCC site. At the latter site, losses of fine particles and Hg were enhanced towards soil surface, while they were less pronounced at the other sites. This study shows that agroforestry systems, even in their early stages of implementation, are characterized by low erosion levels resembling those of local forest environments, thus contributing to the maintenance of soil integrity and to the reduction of Hg and nutrient mobility.

Monsoon Driven Plankton Variation in Trincomalee Coastal Waters

Ecosystem dynamics and nutrient inputs to the coastal water bodies are directly coupled with seasonal fresh water plume formation at marine environment and affect wide range of bio-geochemical and physical processes of coastal waters. Trincomalee Bay and adjacent coastal waters are such a distinctive ecosystem which is frequently subjected to alter its biogeo-chemical processes and cycles by Mahaweli River water discharges with plenty of agrochemicals and organic particulate matters. Present study was conducted in June 2010 to December 2011 in order to monitor both phytoplankton and zooplankton variations with relation to monsoonal driven physico-chemical parameters covering full monsoon cycle, (North-East, South-West, First and Second inter monsoons). Sixteen (16) sampling sites representing three distinctive regions (bay, mouth, and offshore) of Trincomalee coastal waters were subjected for sub surface, (1m depth) sampling (temperature, salinity, nutrients, dissolved oxygen, total suspended solids and plankton), with total area of 450 km2. According to the results, mean phytoplankton abundance varied between 2989-148670 individuals l-1during four monsoons while maximum and minimum numbers were recorded during North East monsoon at Mahaweli River mouth and second inter monsoon at offshore. The highest abundance (7.73×105 individuals l-1) was observed in bay area while the lowest abundance (492 individuals l-1) was recorded in offeshore during North East monsoon. Phytoplankton population was dominated by diatoms (100%) in bay area during North East monsoon while offshore waters invaded by dinoflagellates (40%) during same season. Phytoplankton abundance was positively correlated with nutrients [Nitrate-N (r=0.51) Nitrite-N (r=0.34) and phosphate-P (r=0.40) and Silicate-Si (r=0.54)] and negatively correlated with salinity (r=-0.86). There was no significant varaition between phytoplankton abundance and other oceanographic parameters such as temperature, dissolved oxygen and total suspended solids (P>0.05). Maximum zooplankton (34683 individuals m-3) was observed near Mahaweli River discharge points during North East monsoon while minimum (327 individuals m-3) recorded at offshore canyon area during 2nd inter monsoon. Here, Calanoids dominated the zooplankton population while abundance was positively correlated with silicate (r=0.43), phosphate (r=0.47) and phytoplankton abundance (r=0.59). Salinity impacted negatively (r=-0.52) on zooplankton population while the highest number of groups were found in Koddiyar Bay which is subjected to change in water quality with Mahaweli River discharge. Thus, phytoplankton and zooplankton were maximum at bay during North East monsoon and closely correlated with maximum nutrient concentration carried by Mahaweli run off enriched with eroded soil particles during North East monsoon. Keywords: Phytoplankton, Zooplankton, Nutrients, River discharge

Sources and mechanisms of nitrate and orthophosphate transport in urban stormwater runoff from residential catchments

Nutrients export from residential catchments contributes to water quality impairment in urban water bodies. We investigated the concentrations, transport mechanisms, and sources of nitrate-nitrogen (NO3–N) and orthophosphate-phosphorus (PO4–P) in urban stormwater runoff generated in residential catchments in Tampa Bay, Florida, United States. Street runoff samples, collected over 21 storm events, were supplemented with rainfall and roof runoff samples from six representative residential catchments. Samples were analyzed for N and P forms, N and oxygen (O) isotopes of nitrate (δ18O–NO3− and δ15N–NO3−), and δ18O and hydrogen (δD) isotopes of water (H2O). We found that the main NO3–N source in street runoff was atmospheric deposition (range: 35–64%), followed by chemical N fertilizers (range: 1–39%), and soil and organic N (range: 7–33%), whereas PO4–P in the street runoff likely originated from erosion of soil particles and mineralization from organic materials (leaves, grass clippings). The variability in the sources and concentrations of NO3–N and PO4–P across catchments is attributed to different development designs and patterns, use of various fill materials during land development, and landscaping practices. This data can be useful to develop strategies to offset the impacts of urban development (e.g., designs and patterns resulting in variable impervious areas) and management (e.g., fertilizer use, landscaping practices) on NO3–N and PO4–P transport in urban residential catchments.

Soil Chemistry Patterns In An Edaphic Endemism Hotspot: The Pebble Plains of the San Bernardino Mountains, California

Abstract Pebble plains are a unique edaphic environment known only from the high valleys of the San Bernardino Mountains, California. The pebble plains have long been celebrated for the high vascular plant diversity they support, including at least six taxa endemic to the San Bernardino Mountains. Past research has shown that pebble plains soils differ most notably from nearby non-pebble plains soils in terms of their high clay content and loose, stony structure, especially in their upper-most horizon and on the soil surface. The stony upper horizon is probably the result of frost-heaving and erosion of soil particles by wind; the resulting accumulation of stone fragments at the soil surface is what inspired the name “pebble plains.” The combined effects of a friable, rocky surface, heavy lower horizons, frost heaving, high solar insolation, and desiccating winds are thought to limit recruitment of shrubs and trees and foster the persistence of a unique pebble plains flora consisting of herbaceous annuals...

Applying the USLE Family of Models at the Sparacia (South Italy) Experimental Site

AbstractSoil erosion is a key process to understand the land degradation, and modelling of soil erosion will help to understand the process and to foresee its impacts. The applicability of the Universal Soil Loss Equation (USLE) at event scale is affected by the fact that USLE rainfall erosivity factor does not take into account runoff explicitly. USLE‐M and USLE‐MM, including the effect of runoff in the event rainfall–runoff erosivity factor, are characterized by a better capacity to predict event soil loss. The specific objectives of this paper were (i) to determine the suitable parameterization of USLE, USLE‐M and USLE‐MM by using the dataseries of Sparacia experimental site and (ii) to evaluate their performances at both event and annual scale. The measurements allowed to establish the relationships for calculating the factors of USLE, USLE‐M and USLE‐MM usable at the Sparacia experimental area. At first, for slope‐length values greater than 33 m, the calibration of USLE model at event scale pointed out that sediment delivery processes, that is processes involving deposition of the transported eroded soil particles, occur. The analysis showed that USLE and USLE‐M tend to overestimate low event soil losses, while for USLE‐MM, this tendency is less pronounced. However, the USLE‐MM performed better than USLE and USLE‐M and was able to reproduce better than other two models the highest soil loss values that are the most interesting from a practical point of view. The results obtained at annual scale were generally consistent with those obtained at event scale. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Use pattern of pesticides and their predicted mobility into shallow groundwater and surface water bodies of paddy lands in Mahaweli river basin in Sri Lanka

ABSTRACTPesticides applied on agricultural lands reach groundwater by leaching, and move to offsite water bodies by direct runoff, erosion and spray drift. Therefore, an assessment of the mobility of pesticides in water resources is important to safeguard such resources. Mobility of pesticides on agricultural lands of Mahaweli river basin in Sri Lanka has not been reported to date. In this context, the mobility potential of 32 pesticides on surface water and groundwater was assessed by widely used pesticide risk indicators, such as Attenuation Factor (AF) index and the Pesticide Impact Rating Index (PIRI) with some modifications. Four surface water bodies having greater than 20% land use of the catchment under agriculture, and shallow groundwater table at 3.0 m depth were selected for the risk assessment. According to AF, carbofuran, quinclorac and thiamethoxam are three most leachable pesticides having AF values 1.44 × 10−2, 1.87 × 10−3 and 5.70 × 10−4, respectively. Using PIRI, offsite movement of pesticides by direct runoff was found to be greater than with the erosion of soil particles for the study area. Carbofuran and quinclorac are most mobile pesticides by direct runoff with runoff fractions of 0.01 and 0.08, respectively, at the studied area. Thiamethoxam and novaluron are the most mobile pesticides by erosion with erosion factions of 1.02 × 10−4 and 1.05 × 10−4, respectively. Expected pesticide residue levels in both surface and groundwater were predicted to remain below the USEPA health advisory levels, except for carbofuran, indicating that pesticide pollution is unlikely to exceed the available health guidelines in the Mahaweli river basin in Sri Lanka.

Erratum to: Suspended solids in freshwater systems: characterisation model describing potential impacts on aquatic biota

Purpose High concentration of suspended solids (SS)—fine fraction of eroded soil particles—reaching lotic environments and remaining in suspension by turbulence can be a significant stressor affecting the biodiversity of these aquatic systems. However, a method to assess the potential effects caused by SS on freshwater species in the life cycle impact assessment (LCIA) phase still remains a gap. This study develops a method to derive endpoint characterisation factors, based on a fate and effect model, addressing the direct potential effects of SS in the potential loss of aquatic invertebrate or algae and macrophyte species.