Water quality performance of a batch-type stormwater detention basin.

The objective of this research was to modify an extended detention basin to provide batch treatment of stormwater runoff. An automated valve/controller was developed and placed on the outlet of a detention basin in Austin, Texas, which allowed the water quality volume to be retained in the basin for a preset length of time. The influent and effluent of the modified basin were monitored for total suspended solids (TSS), nutrients, chemical oxygen demand (COD), and total and dissolved metals. Statistically significant removal of total metals, COD, total nitrogen, total phosphorus, and TSS was observed, with a discharge event mean TSS concentration of 7 mg/L and a TSS removal efficiency of 91%. The modified basin has substantially better pollutant removal than conventional extended detention basins and is comparable with that of Austin sand filters, which are a common structural stormwater treatment system in the Austin area. The valve also can be used to isolate hazardous material spills.     

Geochemistry and toxicity of sediment porewater in a salt-impacted urban stormwater detention pond

A comprehensive study was carried out to investigate the impacts of road salts on the benthic compartment of a small urban detention facility, Rouge River Pond. Although the pond is an engineered water body, it is representative of many small urban lakes, ponds and wetlands, which receive road runoff and are probable high impact areas. Specific objectives of the study were to document the porewater chemistry of an aquatic system affected by elevated salt concentrations and to carry out a toxicological assessment of sediment porewater to determine what factors may cause porewater toxicity. The results indicate that the sediment porewater may itself attain high salt concentrations. The computations show that increased chloride levels have important implications on the Cd complexation, augmenting its concentration in porewater. The toxicity tests suggest that the toxicity in porewater is caused by metals or other toxic chemicals, rather than high levels of chloride.     

Spatial and temporal variability of sediment deposition on artificial-lawn traps in a floodplain of the River Elbe

Artificial-lawn mats were used as sediment traps in floodplains to measure sediment input and composition during flood events. To estimate the natural variability, 10 traps were installed during two flood waves at three different morphological units in a meander loop of the River Elbe. The geochemical composition of deposited and suspended matter was compared. The sediment input showed weak correlations with concentration and composition of river water. It also correlated poorly with flood duration and level as well as distance of trap position from the main river. This is due to the high variability of the inundation, different morphological conditions and the variability of sources. The composition of the deposits and the suspended matter in the river water was comparable. Hence, for the investigated river reach, the expected pollution of the floodplain sediments can be derived from the pollution of the suspended matter in the river during the flood wave.     

Spatial variability of arsenic and chromium in the soil water at a former wood preserving site

Contamination of industrial sites by wood preservatives such as chromated copper arsenate (CCA) may pose a serious threat to groundwater quality. The objective of this study was to characterise the spatial variability of As and Cr concentrations in the solid phase and in the soil water at a former wood impregnation plant and to reveal the fundamental transport processes. The soil was sampled down to a depth of 2m. The soil water was extracted in situ from the vadose zone over a period of 10 months at depths of 1 and 1.5m, using large horizontally installed suction tubes. Groundwater was sampled from a depth of 4.5m. Results showed that arsenic and chromium had accumulated in the upper region of the profile and exhibited a high spatial variability (As: 21-621 mg kg(-1); Cr: 74-2872 mg kg(-1)). Concentrations in the soil water were high (mean As 167 microg L(-1); Cr: 62 microg L(-1)) and also showed a distinct spatial variability, covering concentration ranges up to three orders of magnitude. The variability was caused by the severe water-repellency of the surface soil, induced by the concurrent application of creosote wood preservatives, which leads to strong preferential flow as evident from a dye experiment. In contrast to soil water concentrations, only low As concentrations (<12 microg L(-1)) were detected in the groundwater. High Cr concentrations in the groundwater (approx. 300 microg L(-1)), however, illustrated the pronounced mobility of chromium. Our study shows that at sites with a heterogeneous flow system in the vadose zone a disparity between flux-averaged and volume-averaged concentrations may occur, and sampling of soil water might not be adequate for assessing groundwater concentrations. In these cases long-term monitoring of the groundwater appears to be the best strategy for a groundwater risk assessment.     

苏南某市河流水质参数时空变异性研究

以苏南某市区320km2内的河流为研究对象,基于对高锰酸盐指数、NH3-N、TP3个主要水质参数的监测,应用地质统计学的变差函数球状模型和Kriging插值法,对河流有机污染指标、富营养化指标进行了空间插值,用以揭示其时空分布特征及变化趋势,并绘制了时空分布等值线图。结果表明,受不同区域污染物来源的差异、不同河道自身条件的差异和不同水期水生植物、入流水量、河水流动性的差异等因素的影响,研究区河流水质参数呈现出不同的时空变异特征;各水质参数污染均相当严重,尤以富营养化指标氮磷最为显著。     

Accumulated sediments in a detention basin: chemical and microbial hazard assessment linked to hydrological processes

Accumulated sediments in a 32,000-m³ detention basin linked to a separate stormwater system were characterized in order to infer their health hazards. A sampling scheme of 15 points was defined according to the hydrological behaviour of the basin. Physical parameters (particle size and volatile organic matter content) were in the range of those previously reported for stormwater sediments. Chemical analyses on hydrocarbons, PAHs, PCBs and heavy metals showed high pollutant concentrations. Microbiological analyses of these points highlighted the presence of faecal indicator bacteria (Escherichia coli and intestinal enterococci) and actinomycetes of the genus Nocardia. These are indicative of the presence of human pathogens. E. coli and enterococcal numbers in the sediments were higher at the proximity of the low-flow gutter receiving waters from the catchment. These bacteria appeared to persist over time among urban sediments. Samples highly contaminated by hydrocarbons were also shown to be heavily contaminated by these bacteria. These results demonstrated for the first time the presence of Nocardial actinomycetes in such an urban context with concentrations as high as 11,400 cfu g^?1.     

典型污染场地中滴滴涕浓度空间变异性研究

利用经典统计学和地统计学相结合的方法,以某滴滴涕(DDT)粉剂生产企业为例,对污染场地中表层和地下5m处土样DDT浓度的空间变异性进行了研究。结果表明:表层和地下5m处土样DDT浓度经过对数转化后均通过了柯尔莫哥洛夫-斯蜜诺夫检验(K-S检验),能够很好地服从正态分布;表层和地下5m处土样DDT浓度的半变异函数拟合符合高斯模型,决定系数分别为0.8973和0.9348,由空间自相关引起的空间变异性分别占系统总变异性的99.11%和83.12%;用克里格插值法制出的DDT浓度等值线图能直观地反映表层和地下5m处土样DDT浓度的空间分布特征,DDT浓度呈现以原粉生产车间为中心向四周扩散的趋势,地下5m处土样DDT浓度空间分布与表层基本一致。     

Spatial variability of throughfall fluxes in a spruce forest

The spatial variability of throughfall deposition of H(+), Ca(2+), Mg(2+), Na(+), K(+), Cl(-), NO(3)(-), NH(4)(+), O(4)(2-) to a Norway spruce (Picea abies (L.) Karst.) forest was intensively examined during the period October 1986 to October 1987. Large systematic spatial variability of the atmospheric deposition within the forest was observed. The flux of throughfall water was higher away from the trunk compared to the flux close to the trunk. In contrast to this, the deposition of all substances was considerably higher close to the trunk compared to the deposition at the periphery of the canopy. A linear decrease in deposition as a function of the distance from the nearest tree trunk was found. Further, the deposition varied quite dramatically between trees according to their size. The observed spatial variability in throughfall may be due to variabilities in the processes taking part in altering the distribution and composition of the precipitated water as it moves through the canopy. The influence of these processes of precipitation, wash-off, dry deposition and canopy exchange is discussed, and it is found that both increased dry deposition and canopy exchange in the tree tops contribute to the higher solute fluxes found close to the tree trunk.     

Determination of organochlorine pesticide residue in sediment and water from the Densu river basin, Ghana

The distribution of organochlorine pesticides in the aquatic ecosystem from the Densu river revealed varying levels of concentration in water and the sediment samples. Three locations were sampled along the river to evaluate the levels of organochlorine pesticide residue in the river. Sediment and surface water samples were extracted by soxhlet and liquid-liquid extraction respectively and analyzed using Gas Chromatograph coupled with electron capture detector. The detectable organochlorine pesticides were gamma-hexachlorocyclohexane (HCH), delta-hexachlorocyclohexane, heptachlor, aldrin and dieldrin. The other pesticides that were investigated are gamma-chlordane, alpha endosulfan, endosulfan sulfate, p,p′-DDT and its metabolite p,p′-DDE, methoxychlor, endrin and its metabolite endrin aldehyde and endrin ketone. The order of increasing frequency of detection of samples was higher in sediment than water. In sediment, the mean concentration ranged from 0.030 μg kg⁻¹ dry weight (endrin) to 10.98 μg kg⁻¹ dry weight (aldrin). The highest detected concentration of organochlorine in water was endosulfan sulfate with mean concentration of 0.185 μg L⁻¹. Analysis of variance indicated significant differences for most organochlorine pesticide residue in the sediment sampled from the various locations. Some of the levels of organochlorine pesticides detected in water were relatively high compared to guideline values set by World Health Organization and Australia and thus could be harmful if the trend is not checked.     

Spatial and temporal variability of water repellency in a sandy soil contaminated with tar oil and heavy metals

Water repellency can induce preferential flow and thus affect water flow and contaminant transport at hazardous waste sites. Since the spatial patterns of water repellency are mostly unknown, it is problematic to use numerical transport models to predict leachate composition. In this study, the spatial variability of soil water repellency was studied at an industrial site contaminated with tar oil, chromium, copper and arsenic. The persistence of water repellency was assessed by the water drop penetration time (WDPT), and the degree of water repellency was quantified by the ethanol percentage (EP) test. Measurements were made at the soil surface along 3.5-12.1 m long transects at different times between March and October 2002. The spatial variability of WDPT, EP, water content, and organic matter content was quantified by variogram analyses. Both the persistence and the degree of water repellency varied seasonally, with the highest water repellency during the summer months. The correlation lengths of WDPT values ranged between 16 and 406 cm, whereas EP values showed no spatial correlation. For field-moist samples, a critical soil water threshold, below which water repellency prevails, was estimated to be 2.5-4%. For oven dry samples, the WDPT values were dependent on the water content prior to drying. The wide range of correlation lengths and the temporal dynamics of spatial repellency patterns suggest that simulations of solute leaching must consider the spatial and temporal variability of soil hydrophobic properties.     

Spatial and temporal trends in surface water and sediment contamination in the Laurentian Great Lakes

Data from recent sediment and surface water surveys have been collated and mapped to illustrate the spatial distribution of contaminants across the entire Great Lakes basin. Information from historical surveys, together with data from surface water monitoring programs in three major connecting channels, has also been collated in order to evaluate temporal trends. In general, Lakes Superior and Michigan exhibited the lowest levels of sediment contamination while Lake Ontario had the highest. Contaminants such as gamma-HCH (lindane) and dieldrin were ubiquitous in surface waters across the entire basin, which was indicative of atmospheric sources. The distribution of other compounds including hexachlorobenzene, octachlorostyrene and mirex indicated the presence of local sources within the watersheds of the connecting channels. Surficial sediment contamination was found to have decreased markedly since the late 1960s and 1970s. Similarly, surface water contamination decreased over the period 1986-1997 with concentrations of dieldrin, hexachlorobenzene, octachlorostyrene and mirex reduced by over 50%. However, the spatial distributions of both sediment and surface water contamination indicate that further effort is warranted in reducing local sources of contaminants, particularly in Lake Ontario.     

Spatial distribution of trace elements and ecotoxicity of bottom sediments in Rybnik reservoir,Silesian-Poland

Environmental Science and Pollution Research - The aim of study was to integrate chemical analyses and toxicity bioassays in order to assess the environmental risk connected with the presence of...     

Spatial variability in compartmental fate modelling

A new approach is presented which is designed to address the spatial heterogeneity of the environment in compartmental mass balance models of chemical fate in the environment. It rests on the assumption of chemical equilibration within one phase despite prevailing environmental heterogeneity. Composite D- and Z-values are derived from sub-unit specific environmental parameters and are used to solve mass balance equations which can be adopted essentially unchanged from existing compartmental fugacity models. With the resulting common fugacity value for each compartment, sub-unit specific concentrations and process rates can be calculated. The approach is illustrated using the QWASI lake model to calculate the fate of hexachlorobenzene in a hypothetical lake sub-divided in four distinct sub-units. The approach allows the subdivision of each compartment in a large number of sub-units with distinct environmental characteristics without substantially increasing model complexity. This is a necessary condition for linking fugacity models to geographical information systems.     

Degradation in soil and water and ecotoxicity of rimsulfuron and its metabolites.

The degradation and ecotoxicity of sulfonylurea herbicide rimsulfuron and its major metabolites were examined in batch samples of an alluvial sandy loam and in freshwater. An HPLC-DAD method was adapted to simultaneously identify and quantify rimsulfuron and its metabolites, which was successfully validated by GC-MS analysis. In aqueous solutions, pure rimsulfuron was rapidly hydrolyzed into metabolite 1 (N-(4,6-dimethoxypyrimidin-2-yl)-N-(3-(ethylsulfonyl)-2-pyridinylurea)), which itself was transformed into the more stable metabolite 2 (N-((3-(ethylsulfonyl)-2-pyridinyl)-4,6-dimethoxy-2-pyrimidineamine)), with half-life (t(1/2)) values of 2 and 2.5 days, respectively. Hydrolysis was instantaneous under alkaline conditions (pH = 10). In aqueous suspensions of the alluvial soil (pH = 8), formulated rimsulfuron had a half-life of 7 days, whereas that of metabolite 1 was similar to that in water (about 3.5 days). The degradation of the two major metabolites was also studied in soil suspensions with the pure compounds at concentrations ranging from 1 to 10 mg l(-1). The half-life of metabolite 1 ranged from 3.9 to 5 days, close to the previous values. Metabolite 2 was more persistent and its degradation is strongly dependent on the initial concentration (C0): half-life values ranged from 8.1 to 55 days at 2-10 mg l(-1), respectively. These values are higher than those determined from the kinetics of metabolite 1 transformation into metabolite 2 (t(1/2) = 8-19 days). The ecotoxicity of the three chemicals was evaluated through their effect on Daphnia magna and Vibrio fischeri (Microtox bioassay). No effect was observed on D. magna with 24 and 48 h acute toxicity tests. Similarly, no toxic effect was observed with the Microtox test for the three chemicals in the range of concentrations tested that included the field application dose. Thus, being of low persistence and lacking acute toxicity, these chemicals present a low environmental risk. However, chronic effects should be studied in order to confirm the safety of rimsulfuron and its major metabolites.     

Spatial variability of ammonium and nitrate in soils near a poultry farm

This paper assesses the distribution of ammonium (NH4+) and nitrate (NO3-) nitrogen deposition in native bushland soil adjacent to an open ventilated poultry farm. The farm is located in Thirlmere 150 km south west of Sydney, Australia. A total of 104 geographically referenced soil cores were obtained from the study area. Soil pH, electrical conductivity (EC), NH4(+) - and NO3(-)-nitrogen concentrations were analysed for variable trends at three depths, i.e. 0-30, 30-60, and 60-90 cm. Significantly higher concentrations of the two nitrogen forms and EC were observed nearer to the farm in the surface soil samples (0-30 cm). The distribution of NH4+, NO3- and EC were all correlated in surface samples throughout the study area. There was no indication of NH4+ and NO3- leaching within soil profile sampled and it appears that weeds and native vegetation had utilised the accumulated nitrogen. The level of N deposition adjacent to the poultry farm decreased downwind due to dispersion of plume and to the buffering effects from the bushland.     

Aquatic ecotoxicity assessment of a new natural formicide

Background, aim and scope

Agrochemicals could reach aquatic ecosystems and damage ecosystem functionality. Natural formicide could be an alternative to use in comparison with the more toxic formicides available on the market. Thus, the objective of this study was to assess the ecotoxicity of the new natural formicide Macex? with a battery of classical aquatic ecotoxicity tests.

Material and methods

Bacteria (Aliivibrio fischeri), algae (Pseudokirchneriella subcapitata), hydra (Hydra attenuata), daphnids (Daphnia magna), and fish (Danio rerio) tests were performed in accordance with international standardized methodologies.

Results

In the range of formicide concentrations tested (0.03 to 2.0?g?L^?1) EC₅₀ values varied from 0.49 to >2.0?g?L^?1, with P. subcapitata being the most sensitive species and H. attenuata and D. rerio the most tolerant species to this product in aqueous solutions.

Conclusions

This new formicide preparation can be classed as a product of low toxicity compared to the aquatic ecotoxicity of the most common commercialized formicides.     

Computational fluid dynamics modelling of flow and particulate contaminants sedimentation in an urban stormwater detention and settling basin

Sedimentation is a common but complex phenomenon in the urban drainage system. The settling mechanisms involved in detention basins are still not well understood. The lack of knowledge on sediment transport and settling processes in actual detention basins is still an obstacle to the optimization of the design and the management of the stormwater detention basins. In order to well understand the sedimentation processes, in this paper, a new boundary condition as an attempt to represent the sedimentation processes based on particle tracking approach is presented. The proposed boundary condition is based on the assumption that the flow turbulent kinetic energy near the bottom plays an important role on the sedimentation processes. The simulated results show that the proposed boundary condition appears as a potential capability to identify the preferential sediment zones and to predict the trapping efficiency of the basin during storm events.     

Volatilization of contaminants from suspended sediment in a water column during dredging

Remedial dredging of contaminated bed sediments in rivers and lakes results in the suspension of sediment solids in the water column, which can potentially be a source for evaporation of hydrophobic organic compounds (HOCs) associated with the sediment solids. Laboratory experiments were conducted in an oscillating grid chamber to simulate the suspension of contaminated sediments and flux to air from the surface of the water column. A contaminated field sediment from Indiana Harbor Canal (IHC) and a laboratory-inoculated University Lake (UL) sediment, Baton Rouge, LA, were used in the experiments, where water and solids concentration and particle size distribution were measured in addition to contaminant fluxes to air. A transient model that takes into account contaminant desorption from sediment to water and evaporation from the water column was used to simulate water and sediment concentrations and air fluxes from the solids suspension. In experiments with both sediments, the total suspended solids (TSS) concentration and the average particle diameter of the suspended solids decreased with time. As expected, the evaporative losses were higher for compounds with higher vapor pressure and lower hydrophobicity. For the laboratory-inoculated sediment (UL), the water concentrations and air fluxes were high initially and decreased steadily implying that contaminant release to the water column from the suspended solids was rapid, followed by evaporative decay. For the field sediments (IHC), the fluxes and water concentrations increased initially and subsequently decreased steadily. This implied that the initial desorption to water was slow and that perhaps the presence of oil and grease and aging influenced the contaminant release. Comparison of the model and experimental data suggested that a realistic determination of the TSS concentration that can be input into the model was the most critical parameter for predicting air emission rates.     

水源水库沉积物磷的赋存形态及其与间隙水磷的关系

为了探明水源水库沉积物磷的赋存形态及其对水体磷的影响,采用连续提取方法,研究了周村水库沉积物中磷的赋存形态分布特征,并探讨了沉积物各形态磷与总磷、烧失量及间隙水中磷的相关性。结果表明,周村水库内源磷负荷较高,沉积物中TP表现出表层富集的现象,表层沉积物中TP空间分布存在较大差异,上游浅水区为554~563 mg·kg-1,库心附近为424~1 161 mg·kg-1,而坝前深水区高达812~2 969 mg·kg-1。无机磷（IP）是总磷（TP）的主要成分,占TP的79.26%~89.12%,IP主要由铝/铁磷（Al/Fe-P）构成。沉积物中的Al/Fe-P含量很高,具有很大的磷释放潜能。沉积物中各形态磷的浓度垂向分布随深度增加而逐渐降低,其中B、C两点变化最为明显。相关性分析结果表明,间隙水PO43--P与Fe-P存在较好的相关性,说明Fe-P对周村水库沉积物间隙水中PO43--P浓度分布有着重要的影响,周村水库水体季节性分层导致恒温层厌氧情况的发生,Fe-P在厌氧还原条件下释放进入间隙水并向上覆水扩散,进而可能对水体水质产生影响。     

Spatial variability in the degradation rate of isoproturon in soil

Thirty samples of soil were taken at 50-m intersections on a grid pattern over an area of 250 x 200 m within a single field with nominally uniform soil characteristics. Incubations of isoproturon (3-(4-isopropylphenyl)-1,1-dimethylurea) under standard conditions (15 degrees C; -33 kPa soil water potential) indicated considerable variation in degradation rate of the herbicide, with the time to 50% loss (DT50) varying from 6.5 to 30 days. The kinetics of degradation also varied between the sub-samples of soil. In many of them, there was an exponential decline in isoproturon residues; in others, exponential loss was followed by more rapid rates of decline; in a few soil samples, rapid rates of loss began shortly after the start of the incubations. In more detailed studies with soils from a smaller number of sub-sites (20), measurements were again made of isoproturon degradation rate, and the soils were analysed for organic matter content, pH, and nutrient status (N, P, K). Measurements were also made of isoproturon adsorption by the soils and of soil microbial biomass. Patterns of microbial metabolism were assessed using 95 substrates in Biolog GN plates. Soils showing rapid biodegradation were generally of higher pH and contained more available potassium than those showing slower degradation rates. They also had a larger microbial biomass and greater microbial metabolic diversity as determined by substrate utilisation on Biolog GN plates. The implications of the results for the efficacy and environmental behaviour of isoproturon are discussed.