Ecotoxicological risk assessment of a quarry filling with seaport sediments using laboratory freshwater aquatic microcosms

Purpose

In France, contaminated seaport sediments cannot be discharged into the sea according to recent regulation. Hence, they must be managed on land. Among the solutions identified, that of filling terrestrial quarries located in the littoral zone is one of the most promising. However, this requires developing a methodology for ecological risk assessment; which was the aim of the SEDIGEST research program. In the present study, we report the results of toxicological impacts of three sediments on aquatic ecosystems close to a quarry. These results were used to formulate a risk assessment methodology.

Materials and methods

The ecotoxicological approach was based on laboratory microcosm assays applied to leachates obtained from the sediments. The microcosms contained synthetic water and sediment and five pelagic (micro-algae, duckweeds and daphnids) and benthic (chironomids and amphipods) freshwater species. The biota were exposed for 3 weeks to a range of leachate concentrations; metals were monitored in the water column and the effects (i.e. mortality, growth inhibition and midge emergence) were measured.

Results and discussion

The results showed an absence of acute toxicity at concentrations of <10% (v/v) but sublethal effects for concentrations between 1 and 10%. Given the complex nature of the leachates, it was difficult to determine the factors of toxicity. Metals, especially Cu, might have been responsible for some of the effects on the amphipods.

Conclusions

Future quarries filled with seaport sediments might emit pollutants to aquatic ecosystems in their vicinity, and risk assessors should ensure that predicted environmental concentrations of leachates are below the maximum leachate concentration acceptable for the whole ecosystem; for example, by multiplying the concentration safe for the microcosm organisms by a factor of 10.     

Toxicological studies in tropical ecosystems: an ecotoxicological risk assessment of pesticide runoff in South Florida estuarine ecosystems

A multiyear study in the C-111 canal system and associated sites in Florida Bay was undertaken to determine the potential pesticide risk that exists in South Florida. After the examination of extensive pesticide concentration data in surface water, tissues, and semipermeable membrane devices (SPMDs), canal contamination seems to be derived from the extensive agricultural production that drains into the C-111 canal. The results of this study indicate that runoff from agricultural processes led to quantifiable pesticide residues in both canal and bay surface water, which occasionally exceeded current water quality criteria. The major pesticide of concern was endosulfan, which was detected at 100% of the sites sampled. Endosulfan exposure did not cause any acute effects in fish and crustaceans deployed in field bioassays. Chronic effects were observed in copepods, clams, and oysters but could not be attributed to endosulfan exposure. The decision to alter the C-111 canal flow and allow increased freshwater flow into the adjacent Everglades National Park may result in discharges of pesticides into the Everglades. Continued monitoring in this area is needed during this change in flow regime.     

Methodology for land use change scenario assessment for runoff impacts: A case study in a north-western European Loess belt region (Pays de Caux,France)

Changes of agricultural land use often induce changes in hydrological behavior of watersheds. Hence, effective information regarding runoff responses to future land use scenarios provides useful support for decision-making in land use planning and management. The objective of this study is to develop a methodology to assess land use change scenario impacts on runoff at the watershed scale. This objective implies translating qualitative information from scenarios into quantitative input parameters for biophysical models. To do so, qualitative information from scenarios should be quantified and spatialized.     

A model framework for assessing the effects of selenium on aquatic ecosystems

Water, Air, & Soil Pollution - A model framework is being developedto assess the effects of Se toxicity on aquatic ecosystems. The framework integrates several types of model components...     

基于GIS的福建农田氮磷地表径流流失与污染风险评估

为了掌握福建省农田氮磷地表径流流失特征,以福建省的9个地级市为研究边界,通过对其辖区1985—2016年间农田氮、磷化肥施用量的调查,计算农田化肥氮磷的地表径流流失量,并在耦合农田化肥地表径流流失量、降雨和河网密度3个因素的基础上,分析福建省各地级行政区域农田化肥氮磷的污染风险等级,应用地理信息系统(GIS)分析其氮、磷污染的空间分布。结果表明:32年间福建省化肥施用量由4.911×105 t增加到1.239×106t,年均增长3.03%;漳州市氮肥和磷肥的施用强度最大,分别达880.40 kg×hm~(-2)和429.21 kg×hm~(-2);氮磷地表流失量较高的区域主要集中在漳州市,其氮、磷地表流失强度分别达8.71kg×hm~(-2)和1.99kg×hm~(-2)。从氮、磷污染风险等级看,南平市氮、磷肥的流失风险值均最高,分别达63.19%和63.37%,属于高氮磷污染风险区域;厦门市氮、磷肥的流失风险值均最低,分别为0.53%和0.53%,属于低污染风险区域;其他市处于两者之间。可见,漳州市农业发展中应注重氮、磷肥的减量化;南平市则注重对农田氮、磷地表径流流失的风险防范;全省应加大力度发展生态农业,以助力福建省生态文明先行示范区、生态文明试验区的建设。     

面向地表过程模拟的降雨径流模型开发与应用

降雨径流是流域地表过程的主要驱动力,是众多地表模型的基础。该文在充分考虑流域气象及下垫面等要素空间异质性的基础上,提出了一个面向地表过程模拟的、基于DEM的分布式次降雨径流模型。模型将流域离散为栅格计算单元,并按水流特性将栅格划分为坡面单元和河网单元;模型考虑了降雨、植被截流和入渗等产流过程,利用运动波分级汇流的方式进行汇流演算。模型在江西躁口水流域进行了检验和应用。结果表明：该模型模拟的流量过程精度较高;模拟的径流深度及径流搬运力的空间分布符合水文规律。模型结构简洁、参数较少,具有较好的实用价值;为土壤侵蚀及非点源污染等以流路为基础的复杂地表过程研究奠定了基础。     

黄土高原小区径流过程预测模型评价

地表径流是土壤侵蚀和泥沙搬运的主要原动力.径流过程及其特征值是侵蚀模型,特别是侵蚀过程模型中水文模块的重要输入资料,但相对于降雨过程和径流总量资料,径流过程数据十分匮乏.为了对径流过程进行有效模拟,本文利用黄河流域子洲径流试验站团山沟3个小区107场降雨-径流过程观测数据,在小区尺度上对比验证3个仅含有1个参数的简易入渗模型:Ⅰ入渗能力恒定法,即假设入渗能力为1个常值,产流仅发生在降雨强度大于此值的情况;Ⅱ径流系数法,即假设实际入渗率与降雨强度呈正比关系,比例系数为1与径流系数的差值;Ⅲ入渗能力空间变异法,即假设入渗能力存在空间差异,实际入渗率表现为最大入渗率和降雨强度的指数形式.同时,为考查模型在不同时间尺度上的表现,文章分别选取1、6和15 min对数据进行重采样.结果显示:以洪峰流量和有效流量的预测精度作为模型有效性评价指标,相较于径流系数法和入渗能力空间变异法,入渗能力恒定法对黄土高原区径流过程的模拟效果最好,即入渗能力恒定更符合于黄土区实际产流入渗特点;随着过程资料采样时间间隔的增加,模型的模拟精度显著提高,即模型并不依赖于高密度的采样数据.研究结果可为缺乏径流过程资料的地区提供径流过程的计算方法,且有助于定量描述水文过程、土壤侵蚀和泥沙搬运过程.     

Ecotoxicological assessment of the effects of glyphosate and chlorpyrifos in an Argentine soya field

Background, Aim and Scope

Continuous application of pesticides may pollute soils and affect non-target organisms. Soil is a complex ecosystem; its components can modulate the effects of pesticides. Therefore, it is recommended to evaluate the potential environmental risk of these compounds in local conditions. We performed an integrated field-laboratory study on an Argentine soya field sprayed with glyphosate and chlorpyrifos under controlled conditions. Our aim was to compare the sensitivity of a series of endpoints for the assessment of adverse effects of the extensive use of these agrochemicals.

Materials and Methods

A RR soya field in a traditional farming area of Argentina was sprayed with glyphosate (GLY) or chlorpyrifos (CPF) formulations at the commercially recommended rates, according to a randomized complete block design with 3 replicates. In laboratory assays, Eisenia fetida andrei were exposed to soil samples (0–10 cm depth) collected between the rows of soya. Endpoints linked to behavior and biological activity (reproduction, avoidance behavior and bait-lamina tests) and cellular/subcellular assays (Neutral Red Retention Time — NRRT; DNA damage — Comet assay) were tested. Field assays included litterbag and bait-lamina tests. Physico/chemical analyses were performed on soil samples.

Results

GLY reduced cocoon viability, decreasing the number of juveniles. Moreover, earthworms avoided soils treated with GLY. No effects on either reproduction or on avoidance were observed at the very low CPF concentration measured in the soils sampled 10 days after treatment. Both pesticides caused a reduction in the feeding activity under laboratory and field conditions. NRRT was responsive to formulations of CPF and GLY. Comet assay showed significantly increased DNA damage in earthworms exposed to CPF treated soils. No significant differences in DNA migration were observed with GLY treated soils. Litterbag field assay showed no differences between treated and control plots.

Discussion

The ecotoxicological effects of pesticides can be assessed by monitoring the status of communities in real ecosystems or through the use of laboratory toxicity tests. Litterbag field test showed no influence of the treatments on the organic matter breakdown, suggesting a scarce contribution of soil macrofauna. The bait-lamina test, however, seemed to be useful for detecting the effects of GLY and CPF treatments on the activity of the soil fauna. CPF failed to give significant differences with the controls in the reproduction test and the results were not conclusive in the avoidance test. Although the field population density of earthworms could be affected by multiple factors, the effects observed on the reproduction and avoidance tests caused by GLY could contribute to its decrease, with the subsequent loss of their beneficial functions. Biomarkers measuring effects on suborganism level could be useful to predict adverse effects on soil organisms and populations. Among them, NRRT, a lysosomal destabilization biomarker, resulted in demonstrating more sensitivity than the reproduction and avoidance tests. The Comet assay was responsive only to CPF. Since DNA damage can have severe consequences on populations, it could be regarded as an important indicator to be used in the assessment of soil health.

Conclusions

Reproduction and avoidance tests were sensitive indicators of GLY exposure, with the former being more labor intensive. Bait-lamina test was sensitive to both CPF and GLY. NRRT and Comet assays revealed alterations at a subcellular level, and could be considered complementary to the biological activity tests. Because of their simplicity, some of these bioassays seemed to be appropriate pre-screening tests, prior to more extensive and invasive testing.

Recommendations and Perspectives

This study showed deleterious effects of GLY and CPF formulations when applied at the nominal concentrations recommended for soya crops. Further validation is needed before these endpoints could be used as field monitoring tools in Argentine soya soils (ecotoxicological risk assessment — ERA tools).

     

生态毒理学工具在评价石油化工厂区土地耕作适宜性中的运用

The demand for simple and rapid bioassays in ecotoxicological evaluations is of paramount importance in order to speed up environmental monitoring programs. In this study we performed bioassays with lettuce seeds and two species of terrestrial isopods （Armadillidium vulgare and Porcellio dilatatus） for the ecotoxicological assessment of a landfarming soil from a petrochemical complex area. The solubilized content of test soil demonstrated a concentration-response type toxic effect on seed germination rate, and a delay on germination, but showed toxic effect on seedlings wet weight only at the highest concentration. Toxic effects were also observed in mortality rate and avoidance behavior of the two woodlice species. These results demonstrated the sensitiveness of the organisms studied, and highlighted the possibility to use these bioassays in environmental monitoring programs in areas contaminated with fossil fuels.     

Performance assessment and validation of a paramagnetic particle-based enzyme-linked immunosorbent assay for chlorpyrifos in agricultural runoff waters

A commercial magnetic particle-based enzyme-linked immunosorbent assay (ELISA) kit for the insecticide chlorpyrifos [O,O-diethyl-O-(3,5,6-trichloro-2-pyridyl) phosphorothioate] was evaluated for its specificity, precision, and accuracy, its susceptibility to matrix interferences in agricultural and environmental surface waters, and its comparability to a gas chromatographic/flame photometric (GC/FPD) method for the determination of organophosphorus pesticides in natural waters. Repeatability, reproducibility, and accuracy studies show that the kit satisfies current U.S. Environmental Protection Agency criteria for the assessment of analytical methods. Observable matrix effects were found to be present in all of the environmental test waters, with the slopes of calibration curves generated in each of the test matrices deviating from that of the control matrix by as much as 16%. Specificity studies indicate that the chlorpyrifos polyclonal antibody adequately differentiates the target compound from other structurally similar organophosphorus pesticides, with the exception of its methyl analogue. Cross-reactivity with chlorpyrifos-methyl was approximately 37%, while reactivity with diazinon, pyridaphenthion, diclofenthion, bromiphos-ethyl, bromiphos-methyl, pirimiphos-ethyl, and chlorpyrifos oxon ranged from 1.6 to 10.7%. Cross-reactivity with pirimiphos-methyl, 3,5,6-trichloro-2-pyridinol, diethyl phosphate, and diethyl thiophosphate was negligible (<1%). Validation of the paramagnetic particle ELISA format was accomplished using water samples from two monitoring studies that were collected, split, and analyzed directly by ELISA and by GC/FPD. Results of the two analytical methods were then compared using standard t tests, regression analysis, and differences against mean measurement (bias) plots. While the agreement between the two methods was determined to be satisfactory, ELISA exhibits consistent positive bias in environmental matrices. Several preanalysis mitigation steps were suggested that may help moderate bias, but additional study is recommended to explicate the exact factors responsible for its consistent overestimation of results.     

Canopy leaching of cations in Central European forest ecosystems – a regional assessment

The leaching of Ca, Mg, and K from canopies is a major pathway of these cations into forest soils. Our aim was to quantify rates of canopy leaching and to identify driving factors at the regional scale using annual fluxes of bulk precipitation and throughfall from 37 coniferous and deciduous forests of North and Central Europe. Total deposition of Ca, Mg, K, and H⁺ was estimated with Na as an index cation. The median canopy leaching increased in the order: Mg (0.11 kmol_c ha^–1 a^–1) < Ca (0.31 kmol_c ha^–1 a^–1) < K (0.39 kmol_c ha^–1 a^–1). Canopy leaching of Ca and K was positively correlated with the calculated total H⁺ deposition and H⁺ buffered in the canopy, whereas canopy leaching of Mg was not. With contrasting effects, fluxes of SO₄‐S and NH₄‐N in throughfall explained to 64 % (P<0.001) of the Ca canopy leaching. Fluxes of NH₄‐N and Ca were negatively correlated, suggesting that buffering of H⁺ by NH₃ deposition reduced canopy leaching of Ca. Amount of bulk precipitation and SO₄‐S in throughfall were identified as much weaker driving factors for canopy leaching of K (r²=0.28, P<0.01). Our results show that Ca is the dominant cation in buffering the H⁺ input in the canopy. At the regional and annual scale, canopy leaching of Mg appears to be unaffected by H⁺ deposition and H⁺ buffering in the canopy.     

地表糙度与径流水力学参数响应规律模拟

为了明确地表糙度与坡面径流特征及其水力学参数之间的相互作用,通过模拟人工锄耕、人工掏挖、等高耕作和对照组直型坡等4种不同糙度的地表,在室内模拟降雨条件下,对不同糙度坡面上的径流特征和水力学参数(雷诺数、弗劳德数、阻力系数和水流剪切力)以及降雨前后地表糙度的变化进行了测量与计算。结果表明,雨前雨后各措施坡面的地表糙度为:等高耕作人工掏挖人工锄耕直型坡。相同雨强和降雨历时下,不同糙度坡面其径流特征差异显著。初始地表糙度越大的坡面,径流越容易稳定在层流状态;反之,径流越倾向于往紊流发展。对人工锄耕、人工掏挖、等高耕作3种耕作措施来说,在相同雨强和降雨历时下,初始糙度越大的坡面,其断面流量、径流量和产沙量越小。坡面初始地表糙度越大,径流阻力系数也越大,但坡面径流的雷诺数、弗劳德数和径流剪切力则越小,径流对地表糙度具有减小作用,雷诺数和水流剪切力越大,径流对地表糙度的减小作用越弱。研究结果为深入理解坡面地表糙度与其水文特征之间的相互作用提供参考。     

Changes in the composition of sugarcane harvest residues during decomposition as a surface mulch

Many sugarcane crops in northeastern Australia are now harvested without prior burning and large masses of leafy residues are thus available for use as a surface mulch, or for incorporation into the mineral soil. The standing crop biomass of harvest residues at the present study site was estimated at 1583 g/m^-2 on the day of harvest and was followed for 338 days, at which time approximately 19% of the initial mass of residues remained. Decomposition did not depart from simple exponential kinetics. Concentrations of K and Mg declined rapidly with age of the residues. N and Ca initially declined but increased again after 75 days; the increased Ca was attributed to the presence of Ca-enriched earthworm casts. P and C concentrations varied little throughout the study. The C: N ratio started at 170, increased to 240, and subsequently diminished to a minimum of ca. 70. Proximate lignin increased and neutral detergent fibre concentrations decreased with time of decomposition. Decomposition occurred in two phases; an initial phase of rapid leaching was followed by a period of soil mixing resulting from earthworm casting into the decomposing residues.     

Capillary column gas chromatographic determination of trace residues of the herbicide chlorsulfuron in agricultural runoff water

A capillary column gas chromatographic method is described for determining parts-per-trillion (ppt) levels of chlorsulfuron in agricultural runoff water. The water sample is acidified with acetic acid and extracted with methylene chloride. The chlorsulfuron in the extracts derivatized to its monomethyl derivative. After Florisil column cleanup, the methylated chlorsulfuron is determined by electron-capture gas chromatography. Recovery of chlorsulfuron from fortified water samples is greater than 80%. Detection limit of the method is 25 ng chlorsulfuron/L water (25 ppt). There are 2 reaction sites on the chlorsulfuron molecule, both of which are susceptible to methylation leading to monomethyl chlorsulfuron and dimethyl chlorsulfuron. A procedure is described to methylate selectively the sulfonamide nitrogen of chlorsulfuron.     

Foliar washoff potential and simulated surface runoff losses of trifloxysulfuron in cotton

The surface runoff potential of trifloxysulfuron {N-[(4,6-dimethoxy-2-pyrimidinyl)carbamoyl]-3-(2,2,2-trifluoroethoy)-pyridin-2-sulfonamide sodium salt} in cotton (Gossypium hirsutum L.) production systems has not been evaluated. The objectives of this study were to (i) determine sorption/desorption coefficients for trifloxysulfuron; (ii) quantify foliar washoff of trifloxysulfuron when applied to cotton at the five-leaf stage; and (iii) determine the surface runoff potential of trifloxysulfuron when applied to cotton at the five-leaf stage and to bare soil. Freundlich sorption and desorption coefficients were 1.15 and 1.22, respectively. Sorption data indicated that trifloxysulfuron was moderately sorbed to soil and that it will be transported primarily in the dissolved phase of surface runoff. Foliar washoff studies revealed that approximately 91% of trifloxysulfuron applied to cotton at the five-leaf stage was available for washoff 72 h after application. Simulated rainfall (7.5 cm h-1) applied 1 day after herbicide application (7.9 g ha-1) resulted in average concentrations of trifloxysulfuron in surface runoff water of 0.8 microg L-1 for bare plots and 1.3 microg L-1 for cotton plots. Cumulative trifloxysulfuron losses in surface runoff from bare plots and cotton plots were 0.13 and 0.21 g ha-1, respectively. These values correspond to fractional losses of 1.7% for bare plots and 2.7% for cotton plots. Greater runoff losses of trifloxysulfuron from cotton plots were attributed to foliar washoff. Trifloxysulfuron runoff losses may be curtailed if the herbicide is applied early postemergence when canopy coverage is minimal, thereby reducing the potential for foliar washoff.     

西南山区林地空间格局和微地形对坡面地表产流的影响

为明确柏木空间格局和微地形对坡面地表产流的影响,该研究测定了西南山区10个径流小区的柏木空间格局及微地形特征,并观测其降雨和坡面产流过程,利用响应面分析法解析柏木空间格局和微地形对产流特征的影响.结果表明:1)中长历时大雨和中长历时暴雨条件下,地形起伏度、地表粗糙度、径流路径密度、柏木角尺度及柏木密度5个因子均与洪峰流...     

植被过滤带对地表径流中污染物的净化效果

植被过滤带是控制非点源污染的“最佳管理措施”之一。为了探讨植被过滤带在中国西北地区的实际应用,该文作者在陕西小华山水库岸坡地建设了3条不同配置方式的植被过滤带,通过试验测定了植被过滤带对地表径流中几种污染物的净化效果,并分析其影响因素。结果表明,植被过滤带对地表径流中的颗粒态氮、颗粒态磷、总氮、总磷和化学需氧量浓度削减率分别达到82.02%、77.13%、46.05%、73.28%和60.48%以上,负荷削减率分别达到89.98%、87.25%、69.93%、85.11%和77.97%以上,并能有效地削减溶解态氮和溶解态磷的负荷量;自然草地过滤带和沙棘-草本过滤带对地表径流中这几种污染物的削减主要发生在前10 m。过滤带内的植被条件、入流流量和入流污染物浓度是影响过滤带净化效果的重要因素。     

Portable surface plasmon resonance immunosensor for the detection of fluoroquinolone antibiotic residues in milk

An inexpensive and portable surface plasmon resonance (SPR) sensor, SPReeta Evaluation Kit SPR3, has been used to develop a biosensor for the determination of fluoroquinolone antibiotics (FQs) and to demonstrate its performance analyzing FQ residues in milk samples. The SPReeta three-channel gold chips were activated with a mixed self-assembled monolayer (m-SAM) and functionalized with a FQ haptenized protein. Binding of the antibody produced a concentration-dependent increase of the SPR signal as a result of the change in the refraction index. Similarly, the presence of the FQ produced a dose-dependent decrease of the response, which allowed a good limit of detection (LOD) to be obtained (1.0 ± 0.4 μg L(-1) for enrofloxacin in buffer). The response was reproducible in all three channels, on different injections and days, and also between chips. Milk samples could be analyzed after a simple sample treatment involving fat removal by centrifugation and dilution with water. Under these conditions calibration curves were obtained showing that FQ residues can be analyzed in milk samples with an IC(50) value of 26.4 ± 7.2 μg L(-1) and a LOD of 2.0 ± 0.2 μg L(-1) (for enrofloxacin), far below the European Union regulations for this antibiotic family in this matrix. Finally, the paper also demonstrates that the biosensor is able to selectively detect the presence of FQs in milk samples, even in the presence of other antibiotics. Enrofloxacin, ciprofloxacin, and norfloxacin residues were detected in blind samples supplied by Nestle? Co.     

不同植物篱系统对坡耕地农田径流污染物的去除效果

采用人工模拟实验,探讨了四种植物篱系统在不同坡度（5°、10°和20°）、不同污染物进水浓度（低、中、高）下对坡耕地农田径流污染物TN、TP、NH3-N、TOC、COD的去除效果。植物篱系统分别是红叶石楠+小叶女贞+黑麦草（T1）、红叶石楠+小叶女贞（T2）、小叶女贞+黑麦草（T3）、红叶石楠+黑麦草（T4）。结果表明：植物篱系统对污染物的去除率均随坡度的增加而下降,TP、NH3-N、COD尤为明显,当坡度由5°增加到20°时,TP的去除率由52.25%~76.75%降至33.68%~60.34%,NH3-N的去除率由36.84%~68.33%降至34.30%~45.46%,COD的去除率由13.26%~38.69%降至3.15%~26.74%。除NH3-N外,随污染物进水浓度的升高,植物篱对污染物的去除效果越明显,TP的去除率可由33.33%~60.11%升至57.06%~81.44%,TOC的去除率可由-0.84%~2.92%升至9.64%~17.69%, COD的去除率可由-14.75%~11.25%升至20.62%~42.33%。植物篱系统对TN、TP、NH3-N、TOC、COD的去除效果显著优于裸土（对照系统）,在不同坡度下去除率最高分别能由12.81%升至47.02%、34.29%升至76.75%、18.27%升至68.33%、-0.93%升至11.52%、2.31%升至38.69%,在不同污染物进水浓度下分别能由15.57%升至53.05%、37.93%升至81.44%、17.60%升至64.05%、2.92%升至17.69%、-33.40%升至11.25%。总体而言,植物篱系统平均去除效果依次为T1>T4>T3>T2,即红叶石楠+小叶女贞+黑麦草去除效果最佳,这与三种植物的地表覆盖率高、根系发达以及在功能上相互取长补短、协同固定污染物有关。     

Earthworm surface casts affect soil erosion by runoff water and phosphorus transfer in a temperate maize crop

To test the hypothesis that earthworm surface casts contribute to soil erosion and nutrient transfers in a temperate maize crop, two rainfall experiments were set up. One was focused on the erodibility of earthworm casts, the second examined in how casts affect water runoff and nutrient transfers. Casts produced from anecic and endogeic earthworm species were both analyzed. Visual observations in the field showed no cast transport but only cast disintegration and transfers of particles. Erodibility of newly deposited casts was high and differed significantly between age groups. Cast erosion was significantly positively related to initial mass when young but not when old. The paradox is that despite a high cast abundance (25% of the area) and obvious cast erosion, amounts of sediment and nutrient losses (C, N and P) in the runoff were at least twice as high without, than in the presence of, surface casts. Earthworm activities were shown to act as a physical brake for soil erosion by (i) creating a surface roughness with the deposition of surface casts and (ii) reducing water runoff by associated enhanced water percolation. Once the breaking-down point of the physical resistance of casts was reached, all surface casts were quickly disintegrated and finally completely washed away. The amount of particulate phosphorus recovered in water runoff was 34.7 mg P m^{− 2}, while 128.5 mg P m^{− 2} was estimated to have been released from casts. The transfers were found to occur over a short-distance through successive deposition/suspension of soil particles in the water runoff.