Influence of prefreezing on heavy metal concentrations in Bluegill sunfish

Concern for possible changes in tissue metal concentrations due to freezing of fish specimens prior to analysis prompted this investigation. Bluegill sunfish (Lepomis macrochirus) were collected from a Virginia stream and prepared for analysis of zinc, cadmium and lead concentrations either fresh or after 1, 7, and 70 days of freezing. Intact specimens as well as bone and liver tissue were then analyzed. Zinc concentrations displayed a statistically significant (P < 0.05) negative trend with duration of freezing in whole-body, liver and bone samples. Lead and cadmium concentrations showed no consistent pattern which could be related to length of the freezing period in any of the tissues analyzed. However, median concentrations of zinc, cadmium and lead were 10–30% lower in prefrozen sunfish (aggregated over freezing periods) than in sunfish which were analyzed fresh in seven of the eight tissue-metal combinations examined. These results indicate that freezing of sunfish prior to sample preparation can depress metal concentrations in both tissues and whole fish. Programs to monitor heavy metal contamination in sunfish and other fishes may incur bias unless specimens are prepared for analysis fresh or all samples experience equivalent freezing regimes.     

Pb(II)、Cu(II)、Cd(II)在黄土上二元竞争吸附特性研究

铅、铜、镉是3种具有代表性的重金属污染物,可用于模拟多重离子复合污染情况。研究了离子浓度、土水比等因素对3种元素在黄土上二元竞争吸附特性的影响。等温吸附模型Langmuir、Freundlich和D-R模型都能在一定程度上解释Pb(II)-Cu(II)、Pb(II)-Cd(II)、Cu(II)-Cd(II)在黄土上的竞争吸附性能。黄土对Pb(II)、Cu(II)、Cd(II)的选择顺序为Pb(II)>Cu(II)>Cd(II)。相比单一吸附,黄土对每种离子的吸附容量均有不同程度的下降。溶液的初始浓度越大,3种离子在单位黄土上的最大吸附量也随之增大,吸附效率随之降低;适当增大土水比可提高离子的去除效率。试验结果为黄土作为防污屏障和污水处理材料提供了依据。     

海滩含水层中海潮引起的地下水位波动

本文应用有限单元模型MARUN,考察了海滩含水层中海潮引起的地下水位波动。模型的控制方程在空间上用三角单元离散,时间积分上用修正的皮卡迭代法。以一个典型海滩含水层为例,模拟结果表明地下水位的模拟值与观测值基本一致。通过模型参数校正,该海滩被识别为具有两层结构,即由高渗透性的表层和低渗透性的下层组成,低渗透性的下层使得地下水位位于两层交界面之上。对未受人工扰动的原始海滩中地下水水位进行模拟,结果表明坑的开挖对于地下水位几乎没有影响。     

Risk factors contributing to microbiological contamination of shallow groundwater in Kampala,Uganda

A study of water quality variation in shallow protected springs in Kampala was undertaken over a 12-month period to assess the causes of microbiological contamination. The microbiological quality of water was assessed using thermotolerant coliforms and faecal streptococci. Sanitary inspections and hazard assessments were undertaken to identify faecal sources (hazards), contaminant pathways and contributory factors. Data were collected on rainfall and population as additional factors potentially exerting an influence on microbiological quality. Initial analysis of the data showed a significant relationship between median level of contamination and rainfall, in particular to short-term rainfall events. Total sanitary risk score showed a significant relationship with median level of contamination, but population density may be a confounding factor. The raw microbiological data were transformed into five water quality targets: <1 and < or =10 cfu 100ml(-1) for faecal streptococci; and <1, < or =10 and < or=50 cfu 100 ml(-1) for thermotolerant coliforms. The presence of individual risk factors as well as variables for rainfall and population density were analysed with respect to failure to meet these water quality targets using contingency tables. Logistic regression models were developed for each of the five water quality targets. The analysis strongly suggested that there is rapid recharge of the springs after rainfall and this leads to microbiological contamination. On-site sanitation was less important than other sources of faecal matter, which was consistent with a low sanitation coverage in the study area. The study suggested that improving sanitary completion and local environmental hygiene was more important than controlling on-site sanitation in improving the quality of these springs.     

南四湖流域平原区浅层地下水氮污染特征

本文在对浅层地下水"三氮"迁移转化原理和"三氮"污染控制因素进行分析的基础上,阐明了南四湖流域平原区浅层地下水"三氮"含量分布规律,并分析了形成原因。从区域分布看,NO3-N含量呈现湖东山前冲洪积平原区高于湖西冲积湖积平原区的特点;NO2-N含量虽然较低,但含量大于0.01mg/L的地段主要分布于南四湖沿岸和山前冲洪积平原部分地区;NH4-N绝大部分地区未检出。浅层地下水"三氮"含量的上述分布规律与非饱和带的岩性组成、地下水位埋深、农田灌溉方式、土壤含水量等密切相关。最后针对研究区浅层地下水氮污染的特点提出了"三氮"污染防治对策。     

Fuel-grade ethanol transport and impacts to groundwater in a pilot-scale aquifer tank

Fuel-grade ethanol (76L of E95, 95%v/v ethanol, 5%v/v hydrocarbon mixture as a denaturant) was released at the water table in an 8150-L continuous-flow tank packed with fine-grain masonry sand. Ethanol, which is buoyant and hygroscopic, quickly migrated upwards and spread laterally in the capillary zone. Horizontal migration of ethanol occurred through a shallow thin layer with minimal vertical dispersion, and was one order of magnitude slower than the preceding bromide tracer. Dyes, one hydrophobic (Sudan-IV) and one hydrophilic (Fluorescein) provided evidence that the fuel hydrocarbons phase separated from the E95 mixture as ethanol was diluted by pore water and its cosolvent effect was diminished. Most of the added ethanol (98%) was recovered in the effluent wells that captured the flow through the high water content regions above the water table. Complementary bench-scale 2-D visualization experiments with E95 confirmed hydrocarbon phase separation, residual NAPL formation and migration within the capillary fringe. These results corroborate previous bench-scale studies showing that ethanol has high affinity for vadose-zone pore water and can migrate through the capillary zone. The pilot-scale tank experiment provides the first hydrocarbon and ethanol concentration measurements (and thus, quantification of impacts to groundwater quality) from a subsurface spill of E95 in a well-characterized system with a well-defined source. It also provides the first quantitative near-field-scale evidence that capillarity can significantly retard the vertical dispersion and horizontal advection of ethanol. Such effects could be important determinants of the extent of ethanol migration and longevity as well as groundwater impacts.     

Temperature-induced impacts on groundwater quality and arsenic mobility in anoxic aquifer sediments used for both drinking water and shallow geothermal energy production

Aquifers used for the production of drinking water are increasingly being used for the generation of shallow geothermal energy. This causes temperature perturbations far beyond the natural variations in aquifers and the effects of these temperature variations on groundwater quality, in particular trace elements, have not been investigated. Here, we report the results of column experiments to assess the impacts of temperature variations (5°C, 11°C, 25°C and 60°C) on groundwater quality in anoxic reactive unconsolidated sandy sediments derived from an aquifer system widely used for drinking water production in the Netherlands. Our results showed that at 5 °C no effects on water quality were observed compared to the reference of 11°C (in situ temperature). At 25°C, As concentrations were significantly increased and at 60 °C, significant increases were observed pH and DOC, P, K, Si, As, Mo, V, B, and F concentrations. These elements should therefore be considered for water quality monitoring programs of shallow geothermal energy projects. No consistent temperature effects were observed on Na, Ca, Mg, Sr, Fe, Mn, Al, Ba, Co, Cu, Ni, Pb, Zn, Eu, Ho, Sb, Sc, Yb, Ga, La, and Th concentrations, all of which were present in the sediment. The temperature-induced chemical effects were probably caused by (incongruent) dissolution of silicate minerals (K and Si), desorption from, and potentially reductive dissolution of, iron oxides (As, B, Mo, V, and possibly P and DOC), and mineralisation of sedimentary organic matter (DOC and P).     

北京市土壤重金属污染研究

为调查研究北京市一些重点功能区的土壤重金属污染状况,在朝阳、海淀、石景山、通州、怀柔、顺义区等典型的耕地、林地、菜地、工业区、交通区、旅游区选择采集了10个土壤样本。对各样点土壤的pH值、有机质含量、速效P、速效K、全N、全P、全K以及重金属元素Cr、Cd、Pb、Zn的含量进行了测定。采用单项污染指数法和内梅罗综合污染指数法来评价土壤重金属污染程度,并针对北京市不同功能区的土壤重金属污染状况,提出了相应的防治措施与对策。     

Environmental crisis in Bhilai,an industrial complex of Madhya Pradesh,India

The emergence of Bhilai on the industrial scene of India and its growth and development as an industrial complex are a significant landmark in the history of industrialization of the country. In our paper an attempt is made to identify the emerging environmental problems associated with the infra‐structural facilities of the study area, a backward and neglected poverty stricken part of the country. In the area, air, water and noise pollution arise from the emissions of the iron and steel plants. There is no provision for sewage and water disposal. Industrial waste is another serious problem for the complex, e.g. slags from the steel furnaces. Bhilai also suffers from slums and overcrowding. Bearing these facts in view, some suitable suggestions for the proper environmental planning of the area are made.     

Redox pathways in a petroleum contaminated shallow sandy aquifer: Iron and sulfate reductions

A comprehensive hydro-geochemical characterization was carried out in a petroleum-contaminated shallow sandy aquifer in South Africa. The results indicate the presence of a BTEX (benzene, toluene, ethylbenzene, and xylene) plume that has moved, although only slightly, along the regional hydraulic gradient from the spill site. Associated with the contaminant plume, spatial distribution pattern of terminal electron acceptors and metabolites indicates simultaneous occurrence of nitrate, manganese, iron and sulfate reductions resulting in overlapping redox zones within the aquifer. From the measured concentration of metabolic by-products, sulfate and iron reductions seem to be the dominant metabolic pathways, though. Incubation experiments conducted with hydrocarbon contaminated aquifer sediments and inherent microbial assemblages provide a sulfate reduction rate of 4272 nmol cm(-3) day(-1) and 96 nmol cm(-3) day(-1) for winter and summer, respectively. As oppose to this, iron reduction dominates in summer with measured respiration rate of 1414 nmol cm(-3) day(-1). In winter iron reduction was measured to be only 24 nmol cm(-3) day(-1). Based on the dissimilatory iron and sulfate reduction rate measurements, we predict that at the aquifer site, intrinsic BTEX oxidation is primarily occurring in winter and is coupled to sulfate reduction. Although widespread in the aquifer, the contribution of iron reduction for the removal of aromatic monocyclic hydrocarbons is relatively minor.     

Analytical solution for steady-state groundwater inflow into a drained circular tunnel in a semi-infinite aquifer: A revisit

This study deals with the comparison of existing analytical solutions for the steady-state groundwater inflow into a drained circular tunnel in a semi-infinite aquifer. Two different boundary conditions (one for zero water pressure and the other for a constant total head) along the tunnel circumference, used in the existing solutions, are mentioned. Simple closed-form analytical solutions are re-derived within a common theoretical framework for two different boundary conditions by using the conformal mapping technique. The water inflow predictions are compared to investigate the difference among the solutions. The correct use of the boundary condition along the tunnel circumference in a shallow drained circular tunnel is emphasized.     

Delivery and impact bypass in a karst aquifer with high phosphorus source and pathway potential

Conduit and other karstic flows to aquifers, connecting agricultural soils and farming activities, are considered to be the main hydrological mechanisms that transfer phosphorus from the land surface to the groundwater body of a karstified aquifer. In this study, soil source and pathway components of the phosphorus (P) transfer continuum were defined at a high spatial resolution; field-by-field soil P status and mapping of all surface karst features was undertaken in a > 30 km² spring contributing zone. Additionally, P delivery and water discharge was monitored in the emergent spring at a sub-hourly basis for over 12 months. Despite moderate to intensive agriculture, varying soil P status with a high proportion of elevated soil P concentrations and a high karstic connectivity potential, background P concentrations in the emergent groundwater were low and indicative of being insufficient to increase the surface water P status of receiving surface waters. However, episodic P transfers via the conduit system increased the P concentrations in the spring during storm events (but not >0.035 mg total reactive P L⁻¹) and this process is similar to other catchments where the predominant transfer is via episodic, surface flow pathways; but with high buffering potential over karst due to delayed and attenuated runoff. These data suggest that the current definitions of risk and vulnerability for P delivery to receiving surface waters should be re-evaluated as high source risk need not necessarily result in a water quality impact. Also, inclusion of conduit flows from sparse water quality data in these systems may over-emphasise their influence on the overall status of the groundwater body.     

Comparative study of the Cd. Cu and Pb determination by AAS and by ICP-AES in river water : Application to a mediterranean river (Congost river, Catalonia, Spain)

The accuracy, precision, detection limit and rapidity in the determination of Cd, Cu and Pb in river water by AAS determination, previous extraction with APDC-MIBK system, is compared with direct determination method ICP-AES. Both methods show a similar detection limit and an analogous accuracy by the addition standard method. With a calibration curve only ICP-AES presents good accuracy, this technique is advantageous in long term precision and requires minimum sample preparation. The sample stability at different temperature conservation is studied. Finally both methods are applied to the determination of Cd, Cu and Pb in Congost river water.     

Distribution and transport of sediment-bound metal contaminants in the rio grande de tarcoles, costa rica (Central America)

A reconnaissance survey of the extent of metal contamination in the Rio Grande de Tarcoles river system of Costa Rica indicated high levels of chromium (Cr) in the fine-grain bed sediments (<60 μm) of tributaries downstream from leather tanneries (50–83 times Cr background or 3000–5000 μg/g). In the main channel of the river downstream of the San Jose urban area, Cr contamination in sediments was 4–6 times background and remained relatively constant over 50 km to the mouth of the river. Sediments from a mangrove swamp at the river mouth had Cr levels 2–3 times above background. Similar patterns of dilution were observed for lead (Pb) and zinc (Zn) sediment contamination, although the contamination levels were lower. The high affinity of Cr towards particulate phases, probably as Cr(III), allows the use of Cr contamination levels for delineating regions of deposition of fine-grained sediments and dilution of particle associated contaminants during transport and deposition.     

一种金属屋面体系在厂房改建施工中的应用

由于旧工业厂房建设年代较为久远,规范标准及施工水平与现在相比均有较大差距。在将旧工业厂房改建为民用建筑过程中,采用的方案既要符合现行的设计、施工规范标准,又要保证改建的施工工艺具有安全性和可操作性,满足工程的使用功能。结合已经成功运用的工程实例,在原厂房结构的基础上,采用一种金属屋面体系对屋面进行改建,解决了工业厂房屋面改建的难题,不仅保证了屋面的使用功能,而且延续厂房的工业气息,体现了较高的工艺水平,在类似项目中有较高的推广价值。     

The deposition of lead,cadmium, zinc and copper from motor traffic on brachiaria enimi and soil along a major bombo road in Kampala city

The soil and whole plants of Brachiaria enimi were collected beside a major road (Bombo road) and digested with a mixture of concentrated nitric acid, and perchloric acid. The analysis of the soil digests show that lead, cadmium, zinc and copper contents are high close to the road and decrease with distance from the road edge. Also the Pb, Cd, Zn and Cu concentrations in soil fall off rapidly with increasing distance from the road edge, in agreement with previous investigations. The major traffic effect is mainly limited to the surface soil and to a narrow zone within 40 m of the road. Therefore, land use for vegetable production or for livestock foraging should be avoided in a strip of this width.     

Modeling the impact of sea-spray on particle concentrations in a coastal city

With the worlds population becoming increasingly focused on coastal locations there is a need to better understand the interactions between anthropogenic emissions and marine atmospheres. Herein an atmospheric chemistry-transport model is used to assess the impacts of sea-spray chemistry on the particle composition in and downwind of a coastal city--Vancouver, British Columbia. It is shown that the model can reasonably represent the average features of the gas phase and particle climate relative to in situ measurements. It is further demonstrated that reactions in/on sea-spray affect the entire particle ensemble and particularly the size distribution of particle nitrate, but that the importance of these heterogeneous reactions is critically dependent on both the initial vertical profile of sea spray and the sea-spray source functions. The results emphasize the need for improved understanding of sea spray production and dispersion and further that model analyses of air quality in coastal cities conducted without inclusion of sea-spray interactions may yield mis-leading results in terms of emission sensitivities of particle composition and concentrations.     

Determination and speciation of copper and lead in sediments of a Mediterranean river (River Tenes, Catalonia, Spain)

Total concentrations of Cu and Pb and the speciation of these metals in sediments of the River Tenes are studied in order to establish the extent to which they are polluted and their capacity of remobilization. Five samples taken along the river were analyzed, major components of the sediments were studied using XRF and total Pb and Cu content were determined by AAS. In order to test the accuracy of the digestion methods used (triacid attack with nitric, perchloric and hydrofluoric acids or diacic attack with nitric and hydrochloric acids) for the determination of total trace metal, a standard reference material was also analyzed. Triacid attack is proposed to obtain good results. The results show a highly polluted area (1556 mg kg⁻¹ Cu and 1555 mg kg⁻¹ Pb) in the last sampling site analyzed. For metal speciation, the sequential scheme of Tessier et al. was used. From the results obtained, it can be concluded that Cu content in non-residual fraction is bonded mainly to organic matter, whereas non-residual Pb is mainly associated to iron and manganese oxides.     

Migration and speciation of lead in a river system heavily polluted from a smelter

Anodic stripping voltammetry was used for the study of the migration and speciation of lead in surface waters affected by atmospheric deposits around a smelter, by ore mining and urban runoff. Three physiocochemical forms of lead were distinguished: dissolved-labile (Pb²⁺, PbOH⁺ and PbCO₃), dissolved-bound (colloids or strong complexes) and particulate (retained by 0.40 μm membrane filter). Labile forms represented a very significant part of lead input from the washout of the atmospheric deposits, whereas most of lead from urban runoff and ore mining was in particulate or bound forms. Rather large stability of high concentrations of the labile forms of lead in the waters was found. It has been concluded that the precipitation of sparingly soluble lead compounds is not a primary factor controlling the concentration of dissolved lead in stream waters. The migration and speciation of lead was strongly affected by water flow rate. With increasing water flow rate, the concentration of particulate and labile lead increased whereas the concentration of bound forms decreased. Most of the lead was carried downstream in a small river during high water flow rate, but sedimented in a larger river. Rapid removal of lead by sedimentation occurred during low streamflow conditions.     

Indoor and outdoor air concentrations of BTEX and determinants in a cohort of one-year old children in Valencia, Spain

BTEX is the commonly used term for a group of toxic compounds (benzene, toluene, ethyl benzene, ortho-xylene and meta- and para-xylene), some of which, most notably benzene, are known carcinogens. The aim of this study is to measure the BTEX levels both inside and outside the homes of 352 one-year old children from the Valencia cohort of the INMA study (Spain) and to analyze the determinants of these levels. Passive samplers were used to measure BTEX levels during a 15 day period and a questionnaire was administered to gather information on potentially associated factors (sociodemographics, residential conditions, and lifestyle). The average concentrations of benzene, toluene, ethyl benzene, ortho-xylene, and meta- and para-xylene were 0.9, 3.6, 0.6, 0.6, and 1.0 μg/m³, respectively. On average, the indoor levels of all the compounds were approximately 2.5 times higher than those observed outdoors. Factors associated with higher BTEX concentrations inside the home were being the child of a mother of non-Spanish origin, living in a house that had been painted within the last year, living in an apartment, and not having air conditioning. Higher outdoor concentrations of BTEX depend on the residence being situated in a more urban zone, being located within the city limits, having living in a building with more than one story, residing in an area with a greater frequency of traffic, and the season of the year in which the sample was taken. The data thus obtained provide helpful information not only for implementing measures to reduce exposure to these pollutants, but also for evaluating the relation between such exposure and possible health risks for the children in the cohort.