铅锌冶炼厂周边重金属的空间分布及生态风险评价

以关中西部某铅锌厂周边农田为对象,研究了厂区周边土壤中7种重金属含量的水平及垂直分布特征,用Lars Hakanson潜在生态危害指数对重金属的危害程度进行了评价.研究表明,厂区周围土壤中重金属在水平分布上具有局部高度富集的特征.以厂区为中心,重金属水平分布主要在西北-东南方向上,地势低的土壤中重金属含量明显较高;重金属在垂直分布上主要富集在0～ 25 cm的表层土壤中,且随着深度的进一步增加,土壤中重金属浓度变化幅度减弱,基本趋于稳定.厂区周边Cd和Hg污染水平为重度污染,Pb污染水平为中度污染,潜在生态危害程度为重度.     

江苏省城市垃圾焚烧电厂烟气中重金属排放研究

通过对江苏省现有垃圾焚烧电厂进行资料统计,分析了江苏省目前垃圾焚烧电厂规模及分布情况。选择典型垃圾焚烧电厂烟气进行现场采样监测,对垃圾焚烧电厂烟气中重金属铅、汞、镉含量进行分析。根据垃圾焚烧电厂相关信息,结合烟气中重金属含量及相关参数,估算江苏省垃圾焚烧电厂3种重金属年排放量,其中铅为2 010.50kg/a,汞为9.16kg/a,镉为424.63kg/a。根据垃圾焚烧电厂区域分布状况,引入地学模型,对垃圾焚烧电厂重金属区域分布特征进行了分析,结果显示江苏省东部明显高于西部,苏南高于苏北地区,其中苏南地区重金属排放量最大,铅、汞、镉分别占到垃圾焚烧排放总量的48%、51%、60%。通过重金属地学分析和数据统计,确定了江苏省垃圾焚烧重金属排放重点防控区域为苏南地区。     

四川省某铅锌矿尾矿库周边环境重金属污染特征

对四川省某铅锌尾矿库周边土壤、地表水和地下水中的重金属含量及其相关性进行了研究。结果表明:(1)尾矿库周边土壤中Pb、Zn、Cd、As分别为19.8~187.0、11.6~249.0、0.01~3.44、2.6~9.3mg/kg。土壤中重金属元素都存在一定的相关性,Pb与Zn相关系数为0.951,达到极显著相关。(2)尾矿库周边土壤并未受到大面积的重金属污染,综合污染指数平均值为0.98,而选矿厂废水排放至尾矿库的明渠、尾矿库渗滤液排水沟附近土壤污染达到中污染水平。(3)尾矿库尾砂堆积处两翼地下水中有一定Pb污染,推断因为尾砂深度堆积与地下水直接接触。(4)含高浓度硫酸盐的尾矿库废水携重金属沿尾矿库重力坝下渗,对尾矿库渗滤液排放口下游区土壤、地下水造成了重金属和硫酸盐污染。     

钢丝绳产业区废水重金属对土壤与蔬菜的影响及生态风险评价

选取钢丝绳产业区某较发达的一乡镇为研究区域，对其周边土壤及蔬菜的污染状况进行调查和实验研究，结果表明：（1）钢丝绳产业区废水重金属对附近土壤并未产生较大污染，蔬菜重金属元素锌的安全率为100％，铅仅为55％。（2）钢丝绳产业区叶类蔬菜中铅的含量最高，豆类蔬菜中却是锌的含量最高，根茎类蔬菜中铅和锌的含量均较低。     

四川某金属制品厂周边土壤重金属分布特征及污染评价

为考察四川某金属制品厂对周边土壤的重金属污染情况,对厂区周边不同方位、不同距离土壤进行取样,测定土样中Zn、Cr、Pb含量,应用单因子污染指数法和内梅罗综合指数法评价土壤环境质量,并运用Hakanson潜在生态危害指数法评估该区域土壤潜在生态风险。结果表明,厂区周边土壤Zn、Cr质量浓度平均值超过成都市土壤背景值,土样中Zn、Cr、Pb超标率分别为58.7%、94.1%、18.3%;0~10cm表层土样Zn质量浓度显著高于10~20cm亚表层土样,两土层Cr、Pb浓度没有显著差异;3种重金属在土壤中迁移能力为CrPbZn,风向不是影响土壤重金属分布的主要因素;研究区域土壤Zn、Cr处于轻度污染水平,总体处于中度污染水平;研究区3种重金属的潜在生态风险程度依次为PbCrZn,整体处于轻度综合潜在生态风险水平。     

铜陵某富硫尾矿库周边土壤重金属污染特征及风险评价

铜陵某尾矿库堆积大量富硫尾矿,为研究其氧化状况及对周边土壤的污染情况,在尾矿库和周边采集尾矿及土壤样品,测试分析尾矿及土壤样品典型重金属(Hg、As、Cr、Cd、Pb、Zn)含量和赋存形态,并基于单因子污染指数法和内梅罗综合污染指数法对土壤污染状况进行了评价。结果表明:(1)尾矿中Fe_2O_3平均占比达到38.08%(质量分数,下同),S平均占比达到5.34%;(2)尾矿库周边土壤中Cd、As、Zn、Hg严重超标,分别为《土壤环境质量农用地土壤污染风险管控标准(试行)》(GB 15618—2018)风险筛选值的6.3、3.7、1.8、1.5倍;(3)土壤中重金属主要以残渣态形式存在,但Cd、Hg、Zn的非残渣态平均占比均达到25%以上,生物有效性较高,对周边环境存在潜在危害;(4)两种污染指数法评价结果表明,尾矿库周边土壤以Cd、As、Zn污染为主,该富硫尾矿库已对周边环境造成重度污染。     

铜绿山矿区菜地土壤重金属污染特征

以铜绿山矿区菜地为研究对象,测定了土壤和蔬菜中Cu、Zn、Pb、Cd 4种重金属的含量,分析了土壤-蔬菜体系重金属的污染特征和蔬菜对重金属的富集能力。结果表明:矿区菜地土壤中重金属Cu、Zn、Pb、Cd的污染因子分别为10.63、1.12、1.10、0.06,表明Cu污染非常严重,Zn、Pb属轻度污染,Cd无污染;参考《食品中污染物限量》(GB 2762—2017)、《食品中铜限量卫生标准》(GB 15199—94)以及《食品中锌限量卫生标准》(GB 13106—91),蔬菜中Cu、Zn污染较严重且具有普遍性;蔬菜中Cd含量虽均未超出食品安全限值,但明显高于蔬菜根部土壤中的Cd含量;叶菜类、根茎类蔬菜中Pb均未超标,瓜果类蔬菜中Pb超标;蔬菜可食部位对重金属的富集能力为CdZnCuPb;蔬菜中重金属含量与土壤重金属含量总体表现出较弱的相关性,表明蔬菜中重金属的积累不完全决定于土壤重金属的含量,还与土壤中重金属的生物有效性、环境行为及其他环境因素有关。     

吉林省电厂周边农田土壤中多环芳烃含量特征及风险评价

为探究吉林省电厂周边农田土壤中多环芳烃(PAHs)残留情况,选取了4座燃煤电厂,对其周边农田土壤中3种低环PAHs(萘(NAP)、菲(PHE)、蒽(ANT))和苯并(a)芘(BaP)进行了含量特征、污染水平、潜在风险及来源分析。结果表明:NAP、PHE、ANT和BaP均有检出,3种低环PAHs中ANT占比最高,与国内其他典型污染源周边农田相比,处于较低水平;综合质量基准法和质量标准法两种生态风险评价方法可知,电厂周边农田土壤生态风险水平较低;通过健康风险评价可知,BaP的致癌风险处于可接受范围,NAP、PHE和ANT不存在非致癌风险;电厂周边的农田土壤中PAHs主要来源于化石燃料、木材以及高分子化合物的燃烧。     

洛阳郊区蔬菜基地土壤中重金属污染现状调查与评价

为研究洛阳郊区蔬菜基地土壤重金属污染现状,采集了洛阳郊区3个主要蔬菜基地的15个土壤样品,分析了土壤中重金属镉、汞、砷、铅、铬、铜、锌、镍的含量,并采用单项污染指数和综合污染指数进行评价。结果表明,3个蔬菜基地土壤中8种重金属含量均未超标,土壤中重金属单项污染指数和综合污染指数均小于1.0。在3个蔬菜基地中,北郊和东郊基地土壤中重金属的综合污染指数分别为0.52和0.60,均小于0.7,处于清洁(安全)水平,而西郊基地土壤中重金属的综合污染指数为0.78处于尚清洁(警戒限)水平。     

云浮硫铁矿矿区土壤重金属含量的空间分布

对云浮硫铁矿矿区及其周边土壤中Cu、Zn、Pb、Cd、Cr和Ni等元素含量进行了测定分析,利用地统计学方法研究了6种重金属的空间结构与分布特征。结果表明,6种重金属元素平均含量都超出当地土壤元素背景值;结构性因素对Cd、Cu、Zn的空间变异起着较显著的主导作用,而随机性因素对其空间变异的影响是较弱以及不显著的;Pb和Cr表现为具有中等程度的空间相关性,随机效应与结构效应相近;土壤中Cd、Cr、Cu与矿石加工企业以及矿渣的堆放密切相关,Zn的污染主要来源于农业施肥,Ni的含量除了受企业的影响外,农业施肥对重金属污染的影响也是不可忽略的。Pb含量的增加主要是由于矿石的开采造成。     

Effect of new soil metal immobilizing agents on metal toxicity to terrestrial invertebrates

Application of 5% (w:w) novel metal immobilizing agent reduced the water soluble, the calcium chloride extracted as well as the pore water concentration of zinc in soils from Maatheide, a metal contaminated site in the northeast of Belgium. Addition of the metal immobilizing agents also eliminated acute toxicity to the potworm Enchytraeus albidus and the earthworm Eisenia fetida and chronic toxicity to the springtail Folsomia candida. Cocoon production by E. fetida, however, was still adversely affected. These differences may be explained by the species dependent routes of metal uptake: F. candida is probably mainly exposed via pore water while in E. fetida dietary exposure is probably also important. From these results it is clear that organisms with different exposure routes should be used simultaneously to assess the environmental risk of metal contaminated soils.     

Modelling trace metal partitioning in forest floors of northern soils near metal smelters

Trace metal (TM) mobility and toxicity varies with changing soil conditions. Geochemical models can account for the influence of soil characteristics on TM behaviour. We tested the effectiveness of the Stockholm humic model (SHM), and the NICA-Donnan model (NDM) to estimate partitioning coefficients (logKd) in 26 forest floor horizons of podzolic soils enriched in trace metals from deposition by metal smelters. We wanted to know if a consistent approach could be applied to model metal partitioning in forest floors without optimizing each individual soil. When optimized, the SHM reproduced the partitioning of Cd, Cu and Zn but not Pb. It was necessary to revise the affinity constants for the NDM to simultaneously simulate the partitioning of the four metals. Revised affinity constants for the NDM model based on a fixed definition of soil organic carbon, i.e., a fixed ratio of fulvic and humic acids per unit carbon, reproduced metal partitioning more effectively in an independent data set of 16 soils than the use of generic affinity constants available for these models. From the perspective of the applicability of these models to risk assessment, this result suggests geochemical models using affinity constants that have been verified and/or modified against multiple soils from a region can provide good estimates of metal partitioning on a regional scale.     

Strategies of heavy metal uptake by three plant species growing near a metal smelter

Some higher plant species have developed heavy metal tolerance strategies which enable them to survive and reproduce in highly metal-contaminated soils. We have investigated such heavy metal uptake and accumulation strategies of two absolute metallophyte species (Armeria maritima ssp. halleri and Cardaminopsis halleri) and one pseudometallophyte (Agrostis tenuis) growing near a former metal smelter. Samples of plant parts and soil were analysed for Zn, Cd, Pb, and Cu. In soil, there were two dominant types of metal concentration gradients with depth. Under the absolute metallophytes, extremely high metal contents were measured in the surficial Ah horizon, followed by a strong decrease in the underlying soil horizons (L(11) and L(12)). Under the pseudometallophyte, metal concentrations in the Ah horizon were much lower and fewer differences were observed in metal concentrations among the Ah, L(11), and L(12) horizons. The concentrations of Zn, Cd, Pb, and Cu in Agrostis tenuis roots were greater than concentrations in leaves, indicating significant metal immobilisation by the roots. For C. halleri, Zn and Cd concentrations in leaves were >20,000 and >100 mg kg(-1), respectively, indicating hyperaccumulation of these elements. Armeria maritima ssp. halleri exhibited root concentrations of Pb and Cu that were 20 and 88 times greater, respectively, than those in green leaves, suggesting an exclusion strategy by metal immobilisation in roots. However, Zn, Cd, Pb, and Cu concentrations in brown leaves of Armeria maritima ssp. halleri were 3-8 times greater than in green leaves, suggesting a second strategy, i.e. detoxification mechanism by leaf fall.     

Phytostabilization of a metal contaminated sandy soil. II: Influence of compost and/or inorganic metal immobilizing soil amendments on metal leaching

A lysimeter approach (under natural climatologic conditions) was used to evaluate the effect of four metal immobilizing soil treatments [compost (C), compost+cyclonic ashes (C+CA), compost+cyclonic ashes+steel shots (C+CA+SS)) and cyclonic ashes+steel shots (CA+SS)] on metal leaching through an industrially contaminated soil. All treatments decreased Zn and Cd leaching. Strongest reductions occurred after CA+SS and C+CA+SS treatments (Zn: -99.0% and -99.2% respectively; Cd: -97.2% and -98.3% respectively). Copper and Pb leaching increased after C (17 and >30 times for Cu and Pb respectively) and C+CA treatment (4.4 and >3.7 times for Cu and Pb respectively). C+CA+SS or CA+SS addition did not increase Cu leaching; the effect on Pb leaching was not completely clear. Our results demonstrate that attention should be paid to Cu and Pb leaching when organic matter additions are considered for phytostabilization of metal contaminated soils.     

Heavy metal accumulation in Halimione portulacoides: intra- and extra-cellular metal binding sites

Salt marsh plants can sequestrate and inherently tolerate high metal concentrations found in salt marsh sediments. This work intended to understand the Halimione portulacoides (L.) Aellen strategies to prevent metal toxicity, by investigating the metal location in different plant organs and in the cell. A sequential extraction was performed on leaves, stems and roots of H. portulacoides in order to determine and compare the metal (Zn, Pb, Co, Cd, Ni and Cu) concentration in several fractions of the plant material (ethanolic, aqueous, proteic, pectic, polissacaridic, lenhinic and cellulosic). This study shows that all plant organs of H. portulacoides mostly retain metals in the cell wall (65% is the average for all studied metals stored in the root cell wall, 55% in the stems and 53% in the leaves), and the metal content in the intracellular compartment is much lower (21% in roots, 25% in stems and 32% in leaves). High levels of heavy metal in the sedimentary environment do not cause toxicity to H. portulacoides, because H. portulacoides immobilizes them in different cell compartments (cell wall+proteic fraction+intracellular) outside key metabolic sites.     

Remediation of heavy metal polluted sediment by suspension and solid-bed leaching: estimate of metal removal efficiency

Remediation of heavy metal polluted sediment by extracting the metals with sulfuric acid can be performed as follows: abiotic suspension leaching, microbial suspension leaching, abiotic solid-bed leaching, and microbial solid-bed leaching. Abiotic leaching means that the acid is directly added, while microbial leaching means that the acid is generated from sulfur by microbes (bioleaching). These four principles were compared to each other with special emphasis on the effectiveness of metal solubilization and metal removal by subsequent washing. Abiotic suspension leaching was fastest, but suspending the solids exhibits some disadvantages (low solid content, costly reactors, permanent input of energy, high water consumption, special equipment required for solid separation, large amounts of waste water, sediment properties hinder reuse), which prevent suspension leaching in practice. Abiotic solid-bed leaching implies the supply of acid by percolating water which proceeds slowly due to a limited bed permeability. Microbial solid-bed leaching means the generation of acid within the bed and has been proven to be the only principle applicable to practice. Metal removal from leached sediment requires washing with water. Washing of solid beds was much more effective than washing of suspended sediment. The kinetics of metal removal from solid beds 0.3, 0.6 or 1.2m in height were similar; when using a percolation flow of 20lm(-2)h(-1), the removal of 98% of the mobile metals lasted 57-61h and required 8.5, 4.2 or 2.3lkg(-1) water. This means, the higher the solid bed, the lower the sediment-mass-specific demand for time and water.     

锑矿区土壤重金属污染及优势植物对重金属的富集特征

通过野外调查采样,分析了冷水江锑矿区4个采样点土壤和优势植物中重金属含量,以及矿区生长的5种优势植物对Sb、As、Cd、Pb、Cu和Zn的的吸收与富集能力及其富集特性。结果表明,矿区土壤中6种重金属元素的平均含量均超出湖南省土壤背景值和全国土壤背景值,土壤受Sb污染最严重,其次是Cd、As的污染。5种优势植物淡竹叶、苎麻、芒草、狗尾草和白背叶体内Sb、As的含量都超过正常范围,具有修复矿区土壤Sb、As污染的潜力。其中苎麻对Sb的富集系数和转运系数均大于1,满足Sb超富集植物的基本特征,可作为生态恢复的先锋植物;芒草对Cd的富集系数和转运系数都大于1,对重金属有较强的耐性,作为重金属污染的修复植物具有较好的应用前景。