土壤重金属污染的生态风险评估分析:个案研究

研究了浙江富阳某乡土壤重金属污染,并应用概率方法评估了土壤重金属的生态风险。结果表明,研究区土壤中Cu、Zn、Pb、Cd污染严重,平均值分别为290、794、205、2.1mg/kg。生态风险评估表明,土壤重金属Cu、Zn、Pb、Cd对生物种类的风险概率分别为30%、53%、15%和5%,而对生态过程的风险概率分别为44%、70%、13%和0.6%。空间分析表明,研究区有一半以上地区土壤Zn污染对生物种类的影响达75%以上。从保护生态受体来说,对研究区重金属污染的土壤进行修复和风险管理时需要优先针对土壤Zn的污染。     

污染场地土壤修复目标值差异探讨 ——以重庆某化工厂遗留场地为例

污染场地土壤修复目标值确定对于土壤污染的修复效果至关重要,也是污染土壤修复工程实践中出现的难点。国家环境保护部已正式发布了《污染场地风险评估技术导则》(HJ25.3—2014),但实际上《土壤环境质量标准》(GB15618—1995)、《展览会用地土壤环境质量评价标准》(HJ350—2007)等土壤环境质量标准仍未修订或废止,导致两种评价方式并行,且两种不同方式确定的修复目标值存在明显差异,为修复工作带来了极大的困难。本文调查了重庆某化工厂遗留场地土壤污染现状,分别通过两种评价方式确定了修复目标值,结果显示,两种评价方法确定的超标最严重污染物均为苯并[a]芘,但风险评估模型计算的和土壤环境质量标准确定的修复目标值存在较大差异,分别为0.041、0.3mg/kg,计算确定的修复目标值低于现有标准规定的适用限值,建议国家尽快修订或出台与风险评估模型相适应的土壤环境质量标准。     

有机化工污染场地修复后的再利用风险评价

为检验污染土壤修复工程的效果,判断修复土地再利用的生态与环境风险,用人体健康风险评价法,依据土壤污染物进入人体的主要途径及可测量的参数,通过评估一块被有机物污染的场地修复前后的风险,度量了不同土地利用方式下多种土壤污染物经各种途径进入并危害人体健康的风险值及总风险。结果表明,不同土地利用方式下,苯、硝基苯、苯胺的总非致癌风险分别由修复工程实施前的4.42～46.10降低到修复后的2.50×10-3～2.61×10-2,总致癌风险则分别由3.06×10-6～7.41×10-6降低到4.75×10-7～1.19×10-6,修复后的土地适宜作为商业服务或工业用地。     

蚯蚓分子生物标志物在土壤氯代苯胺类污染评价中的应用研究

采用紫外分光光度法测定DNA加合物的形成及Western-Blot技术检测蚯蚓热休克蛋白70（HSP70）的表达,研究了蚯蚓DNA加合物和HSP70作为分子生物标志物在土壤氯代苯胺化合物污染评价中的应用。DNA加合实验的结果表明,随着3,4-二氯苯胺浓度的增加（0.77、1.55、3.10 mg.mL-1）,特征吸收峰的位移发生显著改变,交联率呈现负相关;Western-Blot检测结果表明,3,4-二氯苯胺处理后蚯蚓HSP70表达增加,与空白组比较有显著性差异。     

Multi-Block Data Modeling for Characterization of Soil Contamination: A Case Study

Multi-block (heavy metals, pesticides, physico-chemical parameters) data set pertaining to the soils of alluvium region in Indo-Gangetic plains was analyzed using principal component analysis (PCA) and multiple factor analysis (MFA) methods to delineate the contaminated sites and to identify the possible contamination sources in the study region. In normal PCA, the first three factors were dominated mainly by heavy metals, pesticides and physico-chemical variables, respectively, thus identifying samples/sites contaminated with these. The MFA results, due to its unique weighting scheme of variables of different blocks extracted, to more realistic information about the spatial distribution of samples and relationships among the variables. MFA minimized the influence of variables of one single block on the first few components, allowing variables of all blocks equally to share the common MFA space. This resulted in delineating the sites/regions contaminated with variables (Al, Co, Cu, Mn, Ni, Pb, V, Na, SO₄, aldrin, lindane, HCB, HCH, DDT, and endosulfan) of all the blocks, rather than by particular block variables as in case of normal PCA, where, the variables of single block dominate the first factors, suppressing other block variables. MFA which can be considered as a method for standardization of the multi-block variables was successfully applied to the three block data set of soils.     

Chloroform Associated Health Risk Assessment Using Bootstrapping: A Case Study for Limited Drinking Water Samples

Chlorine is the most commonly used disinfectant for watertreatment but when in contact with organic precursors it producestoxic compounds known as trihalomethanes (THMs). Chloroform isthe most commonly occurring THM and constitutes approximately90% of the THM concentration. A study was conducted inNewfoundland for estimating the chloroform content in thedrinking water supplies in Clarenville and St. John's. Thesampling program was conducted in two stages, July and October-November. Higher concentrations of chloroform were observed in Clarenville but in St. John's the concentrations werewithin Health Canada guidelines. The chloroform is a probablehuman carcinogen and is categorised as `B2' by U.S. EnvironmentalProtection Agency (U.S. EPA). The human health risk associatedwith consumption of drinking water was estimated by performingprobabilistic analysis. In the first phase bootstrap simulations(B = 250) were performed to calculate the variability in thedata. The normal distribution was found the best-fitted distribution to chloroform concentration data. For eachbootstrapped run 1000 Monte Carlo Simulations (MCS) wereperformed in the second phase. The cancer risk was estimatedusing dose-response relationship of chloroform. Appropriateprobability density functions (PDFs) were defined subjectivelyfor intake rate, body weight, exposure duration, exposurefrequency and averaging time. The excess lifetime human cancerrisk varied from 0.5 × 10^-4 to 4.0 × 10^-4, and zero to 1.0 × 10^-4 for Clarenvilleand St. John's, respectively. The average cancer risks in Clarenville and St. John's communities were 1.2 × 10^-4 and 2.5 × 10^-5. The estimated probabilitiesof exceedences above 100 ppb (μg L^-1), were 100 and 2.5% for Clarenville and St. John's, respectively which emphasised the need for water treatment. Granular Activated Carbon (GAC) was proposed as one of the potential treatment technology for risk reduction in St. John's community. The treatment efficiency of a proposed technology was assumed uniformly distributed and revised risks were calculated. Theaverage risk in St. John's can be reduced to 8.0 ×10^-6 after treatment.     

Mercury in Small Freshwater Lakes: A Case Study: Lake Velenje, Slovenia

Lake Velenje is located in one of the most polluted regions ofSlovenia, the ?alek Valley. The major source of pollution is the coal-fired thermal power plant in ?o?tanj (?TPP). In the past, dumping of coal ash directly into Lake Velenje and drainage water from the ash disposal site resulted in unique chemical characteristics of the lake water, such as very high pH (10–12) and high concentrations of heavy metals. The introduction of a closed cycle ash transport system in 1995resulted in a very fast recovery of the lake water quality. The aim of our study was to establish the sources, fate and distribution of mercury in Lake Velenje. In order to establishrecent sources of mercury, total mercury and methylmercury concentrations were measured in various environmental samples(lake inflows, outflow, rainwater, sediments, etc.). Total mercury and methylmercury concentrations were measured at thesurface and at different depths to establish mercury cycling, its transport and chemical transformations in the lake. Generalwater quality parameters (such as pH, Eh, O₂, temperature,TDS, conductivity) were also determined. The results show that the major sources of mercury in Lake Velenje are lake inflows and wet deposition. Total mercury andmethylmercury concentrations in the water column are very low (total mercury: 0.2–2.7 ng L^-1; methylmercury: 20–86 pg L^-1) and can be compared to other non-contaminated freshwater lakes. These results suggest that the major form of mercury emitted from thermal power plant stacks is volatile Hg⁰, whichhas no or very little influence on the nearby surroundings, but rather is subject to long-range atmospheric transport.     

基于GIS的农业土壤重金属风险评价研究——以南京市八卦洲为例

农产品产地环境安全受到广泛关注,合理评价农产品产地土壤重金属的风险状况,具有现实和长远意义。以南京市八卦洲农业土壤为例,选取对人体危害较大的As、Cd、Cr、Hg、Pb五种重金属元素,对表层土壤进行采样分析,分别采用传统标准方法、农业部发布的《全国农产品产地土壤重金属安全评估技术规定》(产地评估标准方法)和改进地累积综合指数法对该地区农业土壤重金属风险状况进行评价,运用GIS地统计学方法分析重金属风险等级的分布特征。结果表明:5种重金属元素的平均含量分别为11.0、0.38、92.1、0.08和34.5 mg kg-1,除元素Hg以外,均超过南京市土壤环境背景值。产地评估标准方法表明八卦洲超过80%的耕地无重金属风险,风险区零散分布在八卦洲西南部、南部以及东部地区,Cd和Pb是造成低风险的主要元素;传统标准方法仅显示了Cd元素的超标特征;地累积指数法表明Cd、Cr、Pb三种元素受人为活动影响较大,改进地累积综合指数法表明研究区总体生态状况良好。传统标准方法与产地评估标准方法能共同识别无风险的区域,而产地评估标准方法能更好地评价和划分农业土壤重金属风险区域,建议与改进地累积综合指数法结合使用,共同评估该地区农业土壤重金属风险水平、空间分布以及生态风险特征。     

A Fuzzy-Set Approach for Addressing Uncertainties in Risk Assessment of Hydrocarbon-Contaminated Site

This study presented an integrated approach for evaluating environmental risks associated with hydrocarbon-contaminated sites through incorporation of a multiphase multi-component modeling system within a general risk assessment framework. The uncertainties associated with risk evaluation criteria were emphasized and effectively addressed through the development of a fuzzy-set approach. This development was based on (a) simulation of the fate of the contaminant in the subsurface to calculate contaminant concentrations in groundwater; (b) examination of the excess lifetime cancer risk (ELCR) distributions; (c) quantification of uncertainties in ELCR evaluation criteria using fuzzy membership functions; (d) categorization of the related risk levels into low, low-to-medium, medium, medium-to-high, and high, and (e) assessment of risk levels based on ELCR distribution and fuzzy evaluation criteria. The developed fuzzy risk assessment approach (FRA) was applied to a hydrocarbon-contaminated site in western Canada. Three remediation scenarios with different efficiencies (0, 60, and 90%) and planning periods (10, 20, 40, and 60 years later) were considered, and the spatial and temporal variations of risk values were examined. The temporal variation of membership values for different risk levels at locations of interest was also identified. The FRA is useful for the decision maker to gain insight into the environmental risks by considering uncertainties and to make more realistic remediation decisions.     

Ecological Risk Assessment of Riverine Contamination in the Caspian Sea Basin: A Conceptual Model for Persistent Organochlorinated Compounds

A conceptual model of the ecological risk assessment for persistent organochlorinated compounds (POCs), like DDT, HCH, and PCBs, which contaminate reservoirs and river waters entering into the Caspian Sea is presented. The model can be used to evaluate the toxicity of POCs in these environments. Examples of this model application using POCs monitoring data for water and bottom sediments of different reservoirs and rivers of the Caspian Sea basin are presented.     

Risk Assessment for Toxicity Experiments with Discrete and Continuous Outcomes: A Bayesian Nonparametric Approach

We present a Bayesian nonparametric modeling approach to inference and risk assessment for developmental toxicity studies. The primary objective of these studies is to determine the relationship between the level of exposure to a toxic chemical and the probability of a physiological or biochemical response. We consider a general data setting involving clustered categorical responses on the number of prenatal deaths, the number of live pups, and the number of live malformed pups from each laboratory animal, as well as continuous outcomes (e.g., body weight) on each of the live pups. We utilize mixture modeling to provide flexibility in the functional form of both the multivariate response distribution and the various dose–response curves of interest. The nonparametric model is built from a structured mixture kernel and a dose-dependent Dirichlet process prior for the mixing distribution. The modeling framework enables general inference for the implied dose–response relationships and for dose-dependent correlations between the different endpoints, features which provide practical advances relative to traditional parametric models for developmental toxicology. We use data from a toxicity experiment that investigated the toxic effects of an organic solvent (diethylene glycol dimethyl ether) to demonstrate the range of inferences obtained from the nonparametric mixture model, including comparison with a parametric hierarchical model.Supplementary materials accompanying this paper appear on-line.     

Risk Assessment of Mercury in Alta Floresta. Amazon Basin - Brazil

In the last 15 years gold mining activity has been the main source of the mercury (Hg) emissions into the atmosphere in the Amazon Basin. The first phase of gold production takes place in remote areas. In general the second one happens in the local urban area, where the gold is commercialized and sent to the great economic centers. In the last 3 years, this activity started to decline as a consequence of the high cost of the gold production but in the Municipality of Alta Floresta, the gold trade still plays an important role in the local economy. This paper addresses the assessment of the Hg exposure scenarios and their quantitative risk for inhalation of metallic Hg vapor and for ingestion of total Hg, using indirect exposure measurements, for different age groups of the urban area of Alta Floresta. This work took into account the field study which provided background information, such as characteristics of local and regional environment, Hg concentrations in different environmental media, and the character of the local urban population. The mean levels of Hg in the atmosphere of the urban area ranged from 210 ng/m³ to 880 ng/m³. Alta Floresta has no riverside population and there is a low fish consumption rate of 8 g/d among the general population. However, mercury levels in locally consumed carnivorous fish, ranged from 0.3 to 3.6 mg/kg, depending on the species and on the period of the year. The levels of mercury in soil surrounding the residential areas near the Hg emissions sources, ranged from 0.05 to 4.10 mg/kg. Hg in soil may represent an important source of mercury ingestion for local children up to 4 years of age. The mean Hazard Index estimated for the general adult population was 1.4. For the general population, regarding the number of persons exposed in the urban area, inhalation of metallic Hg vapor is the main route of exposure. The results for water ingestion for all groups are negligible. For families of fishermen the Hazard Index was estimated to be 9.3, with a contribution of 92% from fish ingestion.     

场地土壤污染物归趋、风险评估和修复治理研究进展

随着城市化快速发展与产业结构的调整,“退二进三”政策的实施以及重污染企业地理位置的变迁,使得多数城市产生大量可再利用再开发的场地。当前场地土壤环境污染状况日益严峻,对场地土壤开展污染物来源识别,成因解析和防控管理等已成为场地土壤污染治理修复的研究重点。基于国内外文献,综述了场地土壤污染物迁移转化过程、风险评估、治理修复等研究进展,发现场地中污染物的来源、输送的“源－汇”关系和不同介质/界面间迁移转化机制等环境行为的综合性研究有待进一步深化;风险评估框架与方法仍具有一定的不全面性和不确定性;绿色可持续联合修复技术已成为土壤修复治理的核心。未来需加强场地土壤“多来源、多途径、多介质、多界面、多尺度”环境过程和机理以及“排放来源、输送途径、迁移转化、动态累积”生态风险评估的系统研究,发展绿色可持续修复功能材料和技术,以期为我国本土场地土壤污染防控管理与修复治理提供依据。     

Mercury Contamination Through Fish Consumption: A Model for Predicting and Preventing Hazardous Behaviour on a Community Level

The relationship between the consumption offish containing methylmercury (MeHg) and human MeHg levels has been studied for many years. Although this relationship has been demonstrated and some models have been developed to assess the risks associated with fish consumption, there is still a need for a simple and efficient predicting tool that can be applied to community settings. This paper provides such a practical model developed through empirical evidence using two sources of data. In ideal conditions, models used to identify hazardous behaviour in individuals would be derived from theoretical and clinical models, however, these conditions are often technically difficult to meet. To overcome this problem, a more empirically oriented model has been developed, based on the estimation of personal mercury intake and its comparison to the Tolerable Daily Intake. The theory and methodology of the model development, including technical limitations, are presented first. The methodology is then applied to the real data to create the final model and the results given. Finally, a discussion of the model's accuracy, limitations and usefulness as a community health assessment tool is presented.     

不同污染类型河流沉积物的汞、铅、锌污染特征研究

研究了葫芦岛市3条具有不同污染源类型河流的沉积物中Hg，Pb，Zn的分布特征，应用相关性、富集系数以及首次引人富集系数比（R）来表征不同污染类型河流沉积物重金属间的相对污染程度及来源。结果表明：源于氯碱厂Hg污染的五里河沉积物中Hg，Ph，Zn含量平均值分别超过区域沉积物背景值662，2．21，4．51倍；受锌冶炼厂废水污染的茨山河沉积物中Hg，Ph，Zn含量平均值超过区域沉积物背景值188863．89，123．6倍；受土壤污染的连山河沉积物中Hg，Pb，Zn含量平均值超过区域沉积物背景值10．43，2．50，2．88倍。五里河沉积物中Hg来源与Pb，Zn不同；茨山河沉积物中Hg，Pb，Zn来自于同一污染源。     

A Quantum Statistical Approach to Remediation Effect of Humic Substances

Among various remediation factors, dissolved organic matter including humic substances (HS) has substantial effect on environmental contamination significantly changing the contaminant??s degradation, bioavailability, reactivity, and immobilization. However, the effects strongly depend on HS concentrations and their aromaticity index (AI). To understand underlying phenomena of remediation action of HS, which is revealed to occur within a definite interval of HS concentrations in water solution, a quantum statistical approach is supposed. Developing this approach, a model of protons as Fermi particles in humic substances was advanced for the first time and applied to describe transformations of HS molecules, i.e., multipoles into micelle structures, which in turn provide for mediating effects in water. Sufficiently high concentration of micelle granules in water solution exists if the concentration of HS lies within a definite interval. It was demonstrated applying a grand canonical Gibbs distribution method to a statistical ensemble of HS particles. Our approach allows for understanding and quantifying some biological and physiological processes connected with mediating action of HS, as for example the reversible red cell aggregation influenced by HS, adsorption of HS particles by cancer cells, and effect of HS on human resistibility to inflammatory processes of different kinds. Application of our results to water systems may be helpful to optimize waste processing and disposal.     

Remediation of Cadmium Pollution in Soils by Different Amendments: A Column Study

Abstract

A column study was conducted to determine the effect of city compost, lime, gypsum, and phosphate on cadmium (Cd) mobility in three well‐recognized benchmark soils of India [viz., (Islamnagar) Vertisol, (Amarpur) Inceptisol, and (Khala) Alfisol]. Columns made of PVC were filled with soil treated with different treatment doses [viz., 0.5% city compost, 1% city compost, 2% city compost, 2.5 t lime/ha, 5 t lime/ha, 2.5 t lime/ha+0.5% city compost, 2.5 t gypsum/ha, 2.5 t gypsum/ha+0.5% city compost, and 100 kg P₂O₅/ha as potassium phosphate (KH₂PO₄). The columns were leached with 100 mg L^?1 Cd under saturated condition. The amount of water moving through the soils was measured as the pore volume. A delayed breakthrough curve (BTC) of Cd in the presence of lime has been observed in all the studied benchmark soil series. Among the treatments, lime application reduced the movement of Cd from surface soil to lower depth of soil to a large extent resulted in 9, 25, and 45% more retention of Cd in surface soil of the Islamnagar, Amarpur, and Khala series respectively. Explanation for reduced Cd mobility in limed soil can be derived from pH changes of soils. In comparison to control soil, phosphate application caused 6, 21, and 30% more retention of Cd in surface soil in the Islamnagar, Amarpur, and Khala series, respectively. Combined application of lime and city compost reduced the movement of Cd in the soil profile. It appears that organic matter controls the sorption of Cd in soils. The amount of Cd sorbed increased with increasing organic carbon content, but gypsum application may leach Cd beyond the root‐zone depth. A rapid breakthrough curve was observed under gypsum‐treated soils. Retardation factor revealed that a somewhat lower degree of Cd retention occurred in the Khala series, which might possibly be attributed to less clay content and low pH. Overall, the column study indicated that total Cd accumulation occurred up to depths of 5–7.5 cm, 7.5–10 cm, and 10–15 cm in soils of Islamnagar, Amarpur, and Khala series, respectively.     

Remediation of Nitrate-Nitrogen Contaminated Groundwater by a Heterotrophic-Autotrophic Denitrification Approach in an Aerobic Environment

A novel heterotrophic-autotrophic denitrification (HAD) approach supported by mixing granulated spongy iron, methanol, and mixed bacteria was proposed for the remediation of nitrate-nitrogen (NO₃-N) contaminated groundwater in a dissolved oxygen (DO)-rich environment. The HAD process involves biological deoxygenation, chemical reduction (CR) of NO₃-N and DO, heterotrophic denitrification (HD), and autotrophic denitrification (AD). Batch experiments were performed to: (1) investigate deoxygenation capacities of HAD; (2) determine the contributions of AD, HD, and CR to the overall NO₃-N removal in the HAD; and (3) evaluate the effects of environmental parameters on the HAD. There were 174, 205, and 2,437?min needed to completely reduce DO by the HAD, spongy iron-based CR, and by the mixed bacteria, respectively. The HAD depended on abiotic and biotic effects to remove DO. CR played a dominant role in deoxygenation in the HAD. After 5?days, approximately 100, 63.0, 20.1, and 9.7?% of the initial NO₃-N was removed in the HAD, HD, AD + CR, and CR incubations, respectively. CR, HD, and AD all contributed to the overall NO₃-N removal in the HAD. HD was the most important NO₃-N degradation mechanism in the HAD. There existed symbiotic, synergistic, and promotive effects of CR, HD, and AD within the HAD. The decrease in NO₃-N and the production of nitrite-nitrogen (NO₂-N) and ammonium-nitrogen (NH₄-N) in the HAD were closely related to the C to N weight ratio. The C to N ratio of 3.75:1 was optimal for complete denitrification. Denitrification rate at 27.5°C was 1.36 times higher than at 15.0°C.     

土壤重金属污染现状与修复技术研究进展

阐述了土壤重金属污染物的来源和重金属污染土壤修复技术研究现状,分析了各种修复技术的优缺点、实用性与发展动态,为土壤重金属污染综合治理与修复提出了新的思路。