Runoff Samples Research Articles

Elucidation of contamination sources for poly- and perfluoroalkyl substances (PFASs) on Svalbard (Norwegian Arctic).

A combination of local (i.e. firefighting training facilities) and remote sources (i.e. long-range transport) is assumed to be responsible for the occurrence of per- and polyfluoroalkyl substances (PFASs) in Svalbard (Norwegian Arctic). However, no systematic elucidation of local PFASs sources has been conducted yet. Therefore, a survey was performed aiming at identifying local PFAS pollution sources on the island of Spitsbergen (Svalbard, Norway). Soil, freshwater (lake, draining rivers), seawater, meltwater run-off, surface snow and coastal sediment samples were collected from Longyearbyen (Norwegian mining town), Ny-Ålesund (research facility) and the Lake Linnévatnet area (background site) during several campaigns (2014-2016) and analysed for 14 individual target PFASs. For background site (Linnévatnet area, sampling during April to June 2015), ΣPFAS levels ranged from 0.4 to 4ng/L in surface lake water (n = 20). PFAS in meltwater from the contributing glaciers showed similar concentrations (~ 4ng/L, n = 2). The short-chain perfluorobutanoate (PFBA) was predominant in lake water (60-80% of the ΣPFASs), meltwater (20-30%) and run-off water (40%). Long-range transport is assumed to be the major PFAS source. In Longyearbyen, five water samples (i.e. 2 seawater, 3 run-off) were collected near the local firefighting training site (FFTS) in November 2014 and June 2015, respectively. The highest PFAS levels were found in FFTS meltwater run-off (118ng/L). Perfluorooctane sulfonic acid (PFOS) was the most abundant compound in the FFTS meltwater run-off (53-58% PFASs). At the research station Ny-Ålesund, seawater (n = 6), soil (n = 9) and freshwater (n = 10) were collected in June 2016. Low ΣPFAS concentrations were determined for seawater (5-6ng/L), whereas high ΣPFAS concentrations were found in run-off water (113-119ng/L) and soil (211-800ng/g dry weight (dw)) collected close to the local FFTS. In addition, high ΣPFAS levels (127ng/L) were also found in freshwater from lake Solvatnet close to former sewage treatment facility. Overall, at both FFTS-affected sites (soil, water), PFOS was the most abundant compound (60-69% of ΣPFASs). FFTS and landfill locations were identified as major PFAS sources for Svalbard settlements.

Evaluation of heavy metal contamination in roadside deposited sediments and road surface runoff: a case study

An exploratory study was carried out to reveal the impact of heavy metal concentration on roadside sediments and road surface runoff along the National Highway NH-2 Delhi–Kolkata, India. The study was carried out during the monsoon season to reveal the impact of heavy metal concentration on the roadside along the National Highway NH-2 Delhi–Kolkata, India. This study presents the heavy metal concentration observed on the deposited sediment and surface runoff. Eighteen sediment and surface runoff samples were collected during the monsoon from nine different locations and were analyzed for the residual concentration using atomic absorption spectroscopy. The experimental results showed that the concentrations of heavy metals were very high for the following sampling points: ADDA more at Asansol (S8) and Ranisayer at Raniganj (S9). To calculate analytical results, and to detect the possible pollution sources of heavy metal correlation analysis and for principal component analysis, agglomeration schedule of cluster analysis was applied to the data matrix. The geo-accumulation index (Igeo) and enrichment factor analysis revealed the major sources of contamination, viz. lithology, traffic volume, and industry and road construction. The present study is essential in the regional aspect where the heavy metal pollution provokes and causes health issues to the residents. This study could also be beneficial to similar scenario seen elsewhere in the world.

Application of Vegetative Buffer Strips Under Natural Rainfall to Conserve Soil and Water

Abstract Soil erosion is one of the most serious environmental issues in the world. The use of vegetative buffer strips is an effective strategy to reduce surface water pollutions as well as soil erosion. The present research has been conducted with aim to study the efficiency of buffer strips in runoff volume and sediment control using experimental plots. In this regard, twelve experimental plots with the dimensions of 1 m × 10 m were provided, and runoff samples were collected monthly to measure runoff volume and sediment. Vetiver grass and tall fescue were used as the plant species of the studied vegetative buffer strips. It was found that, vegetative buffer strips reduced the runoff volume up to 97% and sediment concentration up to 96%. Vetiver grass showed a high efficiency in runoff and sediment control; but, the maximum efficiency is achieved when this species is used along with a plant similar to the tall fescue in terms of density and uniformity. Also, periodic cutting the plants and cleaning the buffer strips can be considered as effective strategies to prevent vegetative buffer strips acting as the source of sediment.

Effect of environmental pollution on susceptibility of sesquioxide-rich soils to water erosion

This work assessed the impact of environmental pollution on soils susceptibility to water erosion within South-eastern Nigeria. Sources of pollutants which could possibly affect the chemical composition of runoff; hence its pH, were first determined by remote sensing and field observations. Rain and runoff water samples collected within the study area were analysed for its physicochemical compositions. Soil samples were also collected and analysed for their geotechnical properties, and chemical composition of their fine fractions. An empirical method was then employed to determine the effect of change in chemical composition of runoff on the susceptibility of the studied soil to water erosion. This was achieved by conducting soil aggregate slaking, dispersion and dissolution tests on aqueous solutions of varying pH. Results from the experiment shows that the fine particle fractions of the soils are chiefly composed of sesquioxides. The slaking of these sesquioxide-cemented soils is not affected by the variations in pH of the solutions, but rather by the plasticity index of the soils. However, dispersion and dissolution of the soil samples where dependent on variations in the pH of the solutions. It was therefore concluded that environmental pollution has the potential of increasing runoff erosivity.

Mercury speciation and distribution in a glacierized mountain environment and their relevance to environmental risks in the inland Tibetan Plateau

Glacierized mountain environments can preserve and release mercury (Hg) and play an important role in regional Hg biogeochemical cycling. However, the behavior of Hg in glacierized mountain environments and its environmental risks remain poorly constrained. In this research, glacier meltwater, runoff and wetland water were sampled in Zhadang-Qugaqie basin (ZQB), a typical glacierized mountain environment in the inland Tibetan Plateau, to investigate Hg distribution and its relevance to environmental risks. The total mercury (THg) concentrations ranged from 0.82 to 6.98ng·L−1, and non-parametric pairwise multiple comparisons of the THg concentrations among the three different water samples showed that the THg concentrations were comparable. The total methylmercury (TMeHg) concentrations ranged from 0.041 to 0.115ng·L−1, and non-parametric pairwise multiple comparisons of the TMeHg concentrations showed a significant difference. Both the THg and MeHg concentrations of water samples from the ZQB were comparable to those of other remote areas, indicating that Hg concentrations in the ZQB watershed are equivalent to the global background level. Particulate Hg was the predominant form of Hg in all runoff samples, and was significantly correlated with the total suspended particle (TSP) and not correlated with the dissolved organic carbon (DOC) concentration. The distribution of mercury in the wetland water differed from that of the other water samples. THg exhibited a significant correlation with DOC as well as TMeHg, whereas neither THg nor TMeHg was associated with TSP. Based on the above findings and the results from previous work, we propose a conceptual model illustrating the four Hg distribution zones in glacierized environments. We highlight that wetlands may enhance the potential hazards of Hg released from melting glaciers, making them a vital zone for investigating the environmental effects of Hg in glacierized environments and beyond.

Spatial-temporal variations of dissolved organic nitrogen molecular composition in agricultural runoff water

Leaching of dissolved organic nitrogen (DON) has been reported as a pathway of N loss from agriculture, but the molecular composition of DON in agricultural water is poorly understood. Runoff water samples were collected from citrus grove furrows (CGF), ditches (CGD) and pasture ditches (PD) in four seasons. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) was used to investigate molecular composition of DON. Chemodiversity index of DON had spatiotemporal variations, while the molecular composition of total DON showed minimal variations, except for PD in November. Lignin derivatives constituted 61% of the total DON compounds. Relative abundance of aliphatic compounds, char and condensed aromatics of unique DON compounds varied spatiotemporally and had a significant correlation with DON concentration. Aromaticity index decreased from CGF to connected CGD, implying that photodegradation is possibly the dominant process that alters molecular composition of aquatic DON during the transport. Significant differences in unique DON composition between CGD and PD indicates that fertilization and land use affect DON composition. The information on molecular characterization of DON should be useful for tracking DON source and developing technologies to remove DON in the agricultural runoff water.

Evaluating the Water Quality Benefits of a Bioswale in Brunswick County, North Carolina (NC), USA

Standard roadside vegetated swales often do not provide consistent pollutant removal. To increase infiltration and pollutant removal, bioswales are designed with an underlying soil media and an underdrain. However, there are little data on the ability of these stormwater control measures (SCMs) to reduce pollutant concentrations. A bioswale treating road runoff was monitored, with volume-proportional, composite stormwater runoff samples taken for the inlet, overflow, and underdrain outflow. Samples were tested for total suspended solids (TSS), total volatile suspended solids (VSS), enterococcus, E. coli, and turbidity. Underdrain flow was significantly cleaner than untreated road runoff for all monitored pollutants. As expected, the water quality of overflow was not significantly improved, since little to no interaction with soils occurred for this portion of the water balance. However, overflow bacteria concentrations were similar to those from the underdrain perhaps due to a first flush of bacteria which was treated by the soil media. For all sampling locations, enterococci concentrations were always higher than the USEPA geometric mean recommendation of 35 Most Probable Number (MPN)/100 mL, but there were events where the fecal coliform concentrations was below the USEPA’s 200 MPN/100 mL limit. A reduction in TSS concentration was seen for both overflow and underdrain flow, and only the underdrain effluent concentrations were below the North Carolina’s high quality water limit of 20 mg/L. Comparing results herein to standard swales, the bioswale has the potential to provide greater treatment and become a popular tool.

Removal of metals from industrial wastewater and urban runoff by mineral and bio-based sorbents

The study was performed to evaluate chemically modified biosorbents, hydrochloric acid treated peat (HCl-P) and citric acid treated sawdust (Citric acid-SD) for their metal removal capacity from dilute industrial wastewater and urban runoff and compare their efficiency with that of commercially available mineral sorbents (AQM PalPower M10 and AQM PalPower T5M5 magnetite). Batch and column experiments were conducted using real water samples to assess the sorbents' metal sorption capacity. AQM PalPower M10 (consisting mainly of magnesium, iron and silicon oxides) exhibited excellent Zn removal from both industrial wastewater and spiked runoff water samples even at low dosages (0.1 g/L and 0.05 g/L, respectively). The high degree of Zn removal was associated with the release of hydroxyl ions from the sorbent and subsequent precipitation of zinc hydroxide. The biosorbents removed Ni and Cr better than AQM PalPower M10 from industrial wastewater and performed well in removing Cr and Cu from spiked runoff water, although at higher dosages (0.3–0.75 g/L). The main mechanism of sorption by biosorbents was ion exchange. The sorbents required a short contact time to reach equilibrium (15–30 min) in both tested water samples. AQM PalPower T5M5 magnetite was the worst performing sorbent, leaching Zn into both industrial and runoff water and Ni into runoff water. Column tests revealed that both HCl-P and AQM PalPower M10 were able to remove metals, although some leaching was witnessed, especially As from AQM PalPower M10. The low hydraulic conductivity observed for HCl-P may restrict the possibilities of using such small particle size peat material in a filter-type passive system.

Transfer of perfluorooctanesulfonate (PFOS), decabrominated diphenyl ether (BDE-209) and Dechlorane Plus (DP) from biosolid-amended soils to leachate and runoff water

Environmental contextThe potential of pollutants to migrate from biosolids must be considered when assessing the environmental risk associated with the application of biosolids in agriculture. We conducted semi-field tests simulating natural conditions to determine the leaching and runoff capacity of emerging organic contaminants following fortification and application of municipal biosolids. We demonstrate the transfer of pollutants from biosolid-amended soil to leachate and runoff water generated by natural rainfall. AbstractAnthropogenic perfluoroalkyl substances, PFASs, and halogenated flame retardants, HFRs, have been detected in different environmental compartments. In order to determine the fate of these compounds in the soil–water system, a semi-field simulated runoff experiment was conducted following the application of municipal organic waste. Therefore, the application of four biosolids was carried out. The biosolids were fortified with perfluorooctanesulfonate (PFOS; ~1 mg PFOS per kg biosolid), decabromodiphenyl ether (c-decaBDE; ~10 mg kg−1) and Dechlorane Plus (DP; ~0.26 mg kg−1) commercial mixtures and were applied to soil packed in 15 runoff-leaching trays (2.5 × 2 × 0.05 m). These trays were designed to collect the leachate and runoff water generated by natural rainfall. PFASs and HFRs were detected in leachate and runoff water from several rainfall events from November 2011 to May 2012 (a first rainfall event of 10.5 × 10−3 m, a second event of 16.0 × 10−3 m and a third pool event with a cumulative amount of 113.1 × 10−3 m) occurring after the initial biosolid application. The total mass distribution calculated in water samples showed a higher content in runoff samples (PFOS, 91 ± 2 %; BDE-209, 76 ± 17 %; DP, 83 ± 14 %). The order of the loamy sand soil affinity for PFOS, BDE-209 and DP was as follows: PFOS < BDE-209 ≤ DP, which was predicted, either from the compounds’ water solubility, the octanol-water partition coefficient (Kow) or the organic carbon-water partition coefficient (Koc). The calculated leaching potential (Lp) index or the Groundwater Ubiquity Score (GUS), which are based on these Kocs, revealed the reverse order of potential transport to surface and groundwater respectively.

Assessment of runoff water quality for an integrated best management practice system in an agricultural watershed

To better understand, implement, and integrate best management practices (BMPs) in agricultural watersheds, critical information on their effectiveness is required. A representative agricultural watershed, Beasley Lake, was used to compare runoff water quality draining through an integrated system of BMPs from row crop cultivated subdrainages as part of the national Conservation Effects Assessment Project (CEAP). From 2011 to 2014, runoff samples were collected across three subdrainages representing two integrated BMPs and three subdrainages representing row crop cultivation. Best management practice sites studied were two vegetated drainage ditches (east [EDV] and west [WDV]) that subsequently flowed into a vegetated sedimentation pond (SP). A suite of critical water quality parameters were assessed and included total suspended solids (TSS), total phosphorus (TP), total nitrogen (TN), nitrate-nitrogen (NO₃-N), ammonium-nitrogen (NH₄-N), and orthophosphate-phosphorus (PO₄-P). During the four-year study period, integrated BMPs were effective at mitigating TSS runoff loads relative to row crop, but less effective at mitigating nutrient runoff loads. Runoff from WDV and SP were only moderately effective in mitigating nutrients in runoff with only TN and TP consistently reduced relative to row crop. Effectiveness of BMPs were primarily a result of the amount of area in tillage practices and crops planted relative to BMP within subdrainage basin area. Decreasing tillage:BMP and/or crop:BMP area ratios produced a subsequent decrease in runoff loads with the exception of NH₄-N and PO₄-P.

放牧制度对草地产流产沙及氮磷流失的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 放牧制度对草地产流产沙及氮磷流失的影响 DOI: 10.5846/stxb201611222378 作者: 作者单位: 内蒙古农业大学水利与土木建筑工程学院,内蒙古农业大学水利与土木建筑工程学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（51339002，51409288，51509133，51569019，51669022）；内蒙古农业大学优秀青年科学基金项目（2014XYQ-10）；高等学校博士学科点专项科研基金项目（20131515120005） Characteristics of sediment content and phosphorus and nitrogen loss in surface runoff from different grazing grasslands Author: Affiliation: Inner Mongolia Agricultural University,Inner Mongolia Agricultural University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:研究不同放牧制度草场水土流失过程，对草原生态环境保护和治理具有重要的理论意义。以内蒙古呼伦贝尔草原不同放牧草场为研究对象，设置选取三种放牧制度草场（自由放牧、轮牧、休牧），采用人工模拟降雨的方法进行0.74mm/min和1.5mm/min雨强的降雨模拟试验，测定径流量，含沙量，径流和泥沙中总氮，总磷浓度，并探讨植被截留对径流的影响规律。结果表明：植被截留对减少降雨径流具有明显的作用，休牧草场径流系数减小最多，自由放牧草场减小最少，产沙量显示为自由放牧草场 > 轮牧草场 > 休牧草场。降雨强度对径流中的氮磷浓度影响显著，自由放牧草场总氮浓度和休牧草场总磷浓度受雨强影响最大，氮磷流失过程浓度变化曲线更符合幂函数分布。休牧草场泥沙氮含量和泥沙磷含量均为最高，自由放牧草场与休牧草场的总氮富集率基本相等且均大于轮牧草场，总磷富集率为自由放牧 > 休牧 > 轮牧，三种放牧草场氮磷和泥沙流失主要影响因素为径流量和含沙量。因此，适当的将呼伦贝尔草原自由放牧草场向休牧和轮牧草场转变，将有利于减少草场水土营养元素流失及草原生态可持续发展。 Abstract:Soil erosion is an important cause of grassland soil fertility loss and ecosystem degradation. The process of and degree of damage caused by soil and water loss will differ under different grazing systems because of different vegetation coverage rates, and this information is also important to instruct practices and governance polices for ecological and environment protection in the grasslands. The study area, the Hulunbuir grassland, located in the Inner Mongolia region of north China, is dominated by sandy soil and has been subject to grassland degradation and loss of area. In this area, we used different stocking rates to select three grazing system-free grazing, rotation grazing, and no-grazing systems-and then chose one grazing grassland in each system. We collected soil samples, and investigated vegetation growth conditions in all three grazing systems. We also assessed soil total phosphorus and total nitrogen. We uses a rainfall simulator to simulate two rainfall intensities-0.74 mm/min and 1.50 mm/min. Each rainfall intensity in the same grazing pasture two rainfall experiment. In each simulated rainfall experiment, we collected all the runoff in order to test runoff volume. When the rainfall began, we collected runoff samples every 3 min for a total of eight times. We tested runoff, sediments, total phosphorus, and total nitrogen of each runoff sample, and assessed the mechanism of phosphorus and nitrogen loss via rainfall runoff. The result shows that the stocking rates had important effects on reducing surface runoff and sediment between different grazing grassland types. The no-grazing system had the most reclining function and free grazing grassland had the least. With respect to silt content in runoff, free grazing was the least effective system and no-grazing the most effective, suggesting that no-grazing grassland would best reduce soil erosion. Tolerance of rainfall intensity differed under different vegetation coverage. The runoff coefficient was reduced 25.0%-45.7% for the no-grazing grassland under the two rainfall intensities; that of the rotation grazing grassland was reduced 13.2%-20.2%; and the free grazing grassland was reduced 7.5%-12.4%. Runoff nitrate concentrations were influenced significantly by rainfall intensity under the free grazing grassland (nitrogen loss significantly affected) and no-grazing grassland (phosphorus loss significantly affected). Moreover, the nitrogen and phosphorus loss curve followed a power function distribution. Soil and nutrient loss were mainly controlled by runoff volume and silt content in all three grazing systems. The nitrogen and phosphorus loss in sediment were highest under the no-grazing grassland. The rotation grazing system had the lowest enrichment rate. The greatest loss of nitrogen and phosphorus was observed in the free grazing grassland. Nitrogen in sediment first increased and then decreased with increasing grazing intensity. The distribution of phosphorus loss in sediment was contrary to that for nitrogen in the three grazing types. Enrichment was observed in the loss of both nitrogen and phosphorus in runoff. The free grazing grassland had the most significant effects on the main influences. Accordingly, these results could provide vital baseline information for choosing grazing methods and grassland management practices and could facilitate the reduction of nitrate runoff losses and encourage the development of adaptable grazing methods. 参考文献 相似文献 引证文献

Investigation of potential toxic effects of construction waste runoff collected from illegal dumping site using brine shrimp and zebrafish models

Urbanization results in the increment of construction waste, which eventually contaminate the surrounding environment and affects the ecosystem. This study aimed to investigate the potential toxic effects of construction waste runoff collected from an illegal construction waste dumping site, Kampung Sungai Pelong, Malaysia by using brine shrimp (Artemia sp.) and zebrqfish (Danio rerio). The runoff sample collected in January 2018 proceeded with the physicochemical test, heavy metal analysis and bio-toxicity study. Several physicochemical properties (BOD, TSS, NH3JV and NO3-) and heavy metal content (Cu>Cd>Ni>As>Pb>Cr>Hg) of runoff had values significantly exceeding the respective Class IIA Malaysia National Water Quality Standards. No mortality and abnormal swimming behaviour were observed for brine shrimp acute assay, but severely damage appendages and pigmentation were evident. In the zebrqfish sub-acute assay, no constant trend of mortality was observed, but abnormal swimming pattern and alterations in gill tissue (cell vacuolation and clubbed tips). The results signify the potential eco-toxicity caused by construction waste runoff and urge the need for long-term toxicity study and strict legislative actions by the local authority.

Effect of uncertainties on probabilistic-based design capacity of hydrosystems

Hydrosystems engineering designs involve analysis of hydrometric data (e.g., rainfall, floods) and use of hydrologic/hydraulic models, all of which contribute various degrees of uncertainty to the design process. Uncertainties in hydrosystem designs can be generally categorized into aleatory and epistemic types. The former arises from the natural randomness of hydrologic processes whereas the latter are due to knowledge deficiency in model formulation and model parameter specification. This study shows that the presence of epistemic uncertainties induces uncertainty in determining the design capacity. Hence, the designer needs to quantify the uncertainty features of design capacity to determine the capacity with a stipulated performance reliability under the design condition. Using detention basin design as an example, the study illustrates a methodological framework by considering aleatory uncertainty from rainfall and epistemic uncertainties from the runoff coefficient, curve number, and sampling error in design rainfall magnitude. The effects of including different items of uncertainty and performance reliability on the design detention capacity are examined. A numerical example shows that the mean value of the design capacity of the detention basin increases with the design return period and this relation is found to be practically the same regardless of the uncertainty types considered. The standard deviation associated with the design capacity, when subject to epistemic uncertainty, increases with both design frequency and items of epistemic uncertainty involved. It is found that the epistemic uncertainty due to sampling error in rainfall quantiles should not be ignored. Even with a sample size of 80 (relatively large for a hydrologic application) the inclusion of sampling error in rainfall quantiles resulted in a standard deviation about 2.5 times higher than that considering only the uncertainty of the runoff coefficient and curve number. Furthermore, the presence of epistemic uncertainties in the design would result in under-estimation of the annual failure probability of the hydrosystem and has a discounting effect on the anticipated design return period.

Spatial glyphosate and AMPA redistribution on the soil surface driven by sediment transport processes - A flume experiment.

This study investigates the influence of small-scale sediment transport on glyphosate and AMPA redistribution on the soil surface and on their off-site transport during water erosion events. Both a smooth surface (T1) and a surface with "seeding lines on the contour" (T2) were tested in a rainfall simulation experiment using soil flumes (1 × 0.5 m) with a 5% slope. A dose of 178 mg m-2 of a glyphosate-based formulation (CLINIC®) was applied on the upper 0.2 m of the flumes. Four 15-min rainfall events (RE) with 30-min interval in between and a total rainfall intensity of 30 mm h-1 were applied. Runoff samples were collected after each RE in a collector at the flume outlet. At the end of the four REs, soil and sediment samples were collected in the application area and in four 20 cm-segments downslope of the application area. Samples were collected according to the following visually distinguished soil surface groups: light sedimentation (LS), dark sedimentation (DS), background and aggregates. Results showed that runoff, suspended sediment and associated glyphosate and AMPA off-site transport were significantly lower in T2 than in T1. Glyphosate and AMPA off-site deposition was higher for T2 than for T1, and their contents on the soil surface decreased with increasing distance from the application area for all soil surface groups and in both treatments. The LS and DS groups presented the highest glyphosate and AMPA contents, but the background group contributed the most to the downslope off-site deposition. Glyphosate and AMPA off-target particle-bound transport was 9.4% (T1) and 17.8% (T2) of the applied amount, while water-dissolved transport was 2.8% (T1) and 0.5% (T2). Particle size and organic matter influenced the mobility of glyphosate and AMPA to off-target areas. These results indicate that the pollution risk of terrestrial and aquatic environments through runoff and deposition can be considerable.

Prediction of hydrographs and flow-duration curves in almost ungauged catchments: Which runoff measurements are most informative for model calibration?

Applications of runoff models usually rely on long and continuous runoff time series for model calibration. However, many catchments around the world are ungauged and estimating runoff for these catchments is challenging. One approach is to perform a few runoff measurements in a previously fully ungauged catchment and to constrain a runoff model by these measurements. In this study we investigated the value of such individual runoff measurements when taken at strategic points in time for applying a bucket-type runoff model (HBV) in ungauged catchments. Based on the assumption that a limited number of runoff measurements can be taken, we sought the optimal sampling strategy (i.e. when to measure the streamflow) to obtain the most informative data for constraining the runoff model. We used twenty gauged catchments across the eastern US, made the assumption that these catchments were ungauged, and applied different runoff sampling strategies. All tested strategies consisted of twelve runoff measurements within one year and ranged from simply using monthly flow maxima to a more complex selection of observation times. In each case the twelve runoff measurements were used to select 100 best parameter sets using a Monte Carlo calibration approach. Runoff simulations using these ‘informed’ parameter sets were then evaluated for an independent validation period in terms of the Nash-Sutcliffe efficiency of the hydrograph and the mean absolute relative error of the flow-duration curve. Model performance measures were normalized by relating them to an upper and a lower benchmark representing a well-informed and an uninformed model calibration. The hydrographs were best simulated with strategies including high runoff magnitudes as opposed to the flow-duration curves that were generally better estimated with strategies that captured low and mean flows. The choice of a sampling strategy covering the full range of runoff magnitudes enabled hydrograph and flow-duration curve simulations close to a well-informed model calibration. The differences among such strategies covering the full range of runoff magnitudes were small indicating that the exact choice of a strategy might be less crucial. Our study corroborates the information value of a small number of strategically selected runoff measurements for simulating runoff with a bucket-type runoff model in almost ungauged catchments.

Subtype analysis of zoonotic pathogen Cryptosporidium skunk genotype

Cryptosporidium skunk genotype is a zoonotic pathogen commonly identified in surface water. Thus far, no subtyping tool exists for characterizing its transmission in humans and animals and transport in environment. In this study, a subtyping tool based on the 60kDa glycoprotein (gp60) gene previously developed for Cryptosporidium chipmunk genotype I was used in the characterization of Cryptosporidium skunk genotype in animal and storm runoff samples from a watershed in New York. Altogether, 17 positive samples from this watershed and 5 human and animal specimens from other areas were analyzed. We identified 14 subtypes of Cryptosporidium skunk genotype, 11 of which were seen in the watershed. In phylogenetic analysis, these subtypes belonged to 4 subtype families (XVIa, XVIb, XVIc, and XVId). No host-adapted subtypes were identified and the two subtypes in humans were genetically similar to some in raccoons, otters, and storm runoff samples from the watershed. The characteristics of gp60 protein sequences of the Cryptosporidium skunk genotype are similar to those of other Cryptosporidium species, but only its XVIb subtype family has a putative furin cleavage site. This subtyping tool might be useful in characterizing Cryptosporidium skunk genotype in clinical and environmental samples.

Mineral-leaching chemical transport with runoff and sediment from severely eroded rare-earth tailings in southern China

Abstract. Rare-earth mining has led to severe soil erosion in southern China. Furthermore, the presence of the mineral-leaching chemical ammonium sulfate in runoff and sediment poses a serious environmental threat to downstream water bodies. In this paper, the characteristics of mineral-leaching chemicals in surface soil samples collected in the field were studied. In addition, NH4+ and SO42− transport via soil erosion was monitored using runoff and sediment samples collected during natural rainfall processes. The results demonstrated that the NH4+ contents in the surface sediment deposits increased from the top of the heap (6.56 mg kg−1) to the gully (8.23 mg kg−1) and outside the tailing heap (13.03 mg kg−1). The contents of SO42− in the different locations of the tailing heaps ranged from 27.71 to 40.33 mg kg−1. During typical rainfall events, the absorbed NH4+ concentrations (2.05, 1.26 mg L−1) in runoff were significantly higher than the dissolved concentrations (0.93, 1.04 mg L−1), while the absorbed SO42− concentrations (2.87, 1.92 mg L−1) were significantly lower than the dissolved concentrations (6.55, 7.51 mg L−1). The dissolved NH4+ and SO42− concentrations in runoff displayed an exponentially decreasing tendency with increasing transport distance (Y = 1. 02 ⋅ exp( − 0. 00312X); Y = 3. 34 ⋅ exp( − 0. 0185X)). No clear trend with increasing distance was observed for the absorbed NH4+ and SO42− contents in transported sediment. The NH4+ and SO42− contents had positive correlations with the silt and clay ratio in transported sediment but negative correlations with the sand ratio. These results provide a better understanding of the transport processes and can be used to develop equations to predict the transport of mineral-leaching chemicals in rare-earth tailings, which can provide a scientific foundation for erosion control and soil management in rare-earth tailing regions in southern China.

Significance of wetlands for sediment and nutrient reduction in Lake Tana Sub-Basin, Upper Blue Nile Basin, Ethiopia

Sedimentation from agricultural fields and seasonal eutrophication from non-point source inorganic nutrients (N, P and OM) on the lakes and reservoirs are the main problems in the Tana sub-basin, Ethiopia. The objective of this study was to quantify the amount of suspended sediment concentration and sediment fixed nutrients in the wetland. Two wetlands were selected purposefully to quantify how much sediment and nutrient trapped by the wetlands and 26 runoff events were sampled for each wetland at inlet and outlet points. All runoff samples were filtered by a filter paper and measured after air dried using sensitive balance to determine sediment amount in g/L. Only 10 representative samples were subjected to nutrient analysis in the laboratory. Averagely, 7 g/L (86%) and 3 g/L (80%) suspended sediment was absorbed by wetlands in site 2 and site 1 respectively. Regarding to nutrient loss, 53, 50 and 49% nitrogen, phosphorus and organic matter (OM) was absorbed by wetland in site 2 respectively. Whereas, it was 33, 29 and 31% in site 1. Thus, wetlands have crucial role to catch suspended sediment load and associated nutrients entering into downstream reservoirs and lakes.

Effects of soil surface roughness on interrill erosion processes and sediment particle size distribution

Soil surface roughness significantly impacts runoff and erosion under rainfall. Few previous studies on runoff generation focused on the effects of soil surface roughness on the sediment particle size distribution (PSD), which greatly affects interrill erosion and sedimentation processes. To address this issue, a rainfall-simulation experiment was conducted with treatments that included two different initial soil surface roughnesses and two rainfall intensities. Soil surface roughness was determined by using photogrammetric method. For each simulated event, runoff and sediment samples were collected at different experimental times. The effective (undispersed) PSD of each sediment sample and the ultimate (after dispersion) PSD were used to investigate the detachment and transport mechanisms involved in sediment movement. The results show that soil surface roughness significantly delayed runoff initiation, but had no significant effect on the steady runoff rate. However, a significant difference in the soil loss rate was observed between the smooth and rough soil surfaces. Sediments from smooth soil surfaces were more depleted in clay-size particles, but more enriched in sand-size particles than those from rough soil surfaces, suggesting that erosion was less selective on smooth than on rough soil surfaces. The ratio of different sizes of transported sediment to the soil matrix indicates that most of the clay was eroded in the form of aggregates, silt-size particles were transported mainly as primary particles, and sand-size particles were predominantly aggregates of finer particles. Soil surface roughness has a crucial effect on the sediment size distribution and erosion processes. Significant differences of the enrichment ratios for the effective PSD and the ultimate PSD were observed under the two soil surface roughness treatments. These findings demonstrate that we should consider each particle size separately rather than use only the total sediment discharge in assessing and modeling interrill erosion processes.

Effect of Vegetative Buffer Strips on Herbicide Runoff From a Nontilled Soil

Buffer strips can reduce herbicide runoff from cultivated fields due to the ability of vegetation to impede the flow of surface runoff, promote infiltration, and adsorb herbicides. Conservation agriculture has many environmental advantages, but the transition phase from a conventional to a conservation system is a critical period, especially for surface runoff. In 2015, a field in Italy that was transitioning from conventional to conservation agriculture was tested to analyze the efficacy of different types of buffer strips in reducing the runoff of three herbicides compared with no-buffer plots. At each runoff event, water volume was measured and terbuthylazine, metolachlor, and mesotrione concentrations were determined. Buffer strips were able to reduce the number of runoff events by 63% to 83%. The runoff volumes were significantly reduced in the presence of buffer strips, whereas no differences were found between different types of buffer strips. Among herbicides, mesotrione was not detected in runoff water samples. The highest losses of terbuthylazine and metolachlor were from plots without buffer strips during the first three runoff events. All types of buffer strips significantly reduced the total losses of terbuthylazine and metolachlor in the monitored runoff events, with a reduction of more than 99%. This study confirmed that buffer strips are a very effective mitigation system against surface water pollution by herbicides, even in agronomic situations that promote runoff.