金矿污染河流的水体和沉积物中重金属分布特征及生态风险评价

金矿开采导致严重的水体和沉积物重金属污染。采用电感耦合等离子体质谱仪(ICP/MS)分析了金矿开采区河道32个采样点的水体和表层沉积物样品,研究了水样的溶解态及颗粒态重金属(As、Pb、Cd、Cr、Cu、Zn)组成;通过分步化学提取法研究了各重金属在沉积物中的地球化学形态组成,利用地累积指数法和潜在生态风险指数法评价了河流沉积物中重金属污染状况。结果表明:水体中Cu、Zn、As主要以溶解态存在,Pb、Cr、Cd以颗粒态为主。水体中重金属元素形态分布主要受点源污染排放影响。沉积物中,Cd浓度较低;As、Zn主要以氧化物结合态、有机物结合态和残渣态存在;Pb、Cr、Cu以有机物结合态和残渣态为主。结合地累积指数和潜在生态风险指数分析表明,Cd和Cu为主要的风险元素。     

北运河沉积物/水界面上重金属迁移转化规律

分析测定了6种元素(Cr、Co、Mn、Cu、Pb、Zn)在北运河水系10个采样点水体和表层沉积物中的含量和形态分布,利用SPSS 19.0统计软件对重金属在不同形态中的含量进行相关性分析。结果显示,北运河下游重金属污染程度高于上游;Cr、Cu、Pb、Zn在底泥可提取态中所占比例相当高,多数采样点都超过10.0%。所研究的重金属多数在底泥Fe-Mn结合态与悬浮物、可交换态、硫化物和有机质结合态均存在相关性;Mn是北运河地化循环中最为活跃的元素。     

生物沥滤过程中城市污泥Zn、Cu的形态转化

利用80L SBR进行了生物沥滤城市污泥实验,探讨了污泥胞外聚合物中重金属的含量变化,并对重金属Zn、Cu各化学形态之间的转化情况进行了分析.结果表明,整个生物沥滤过程中,污泥胞外聚合物中Zn和Cu含量先上升后下降,反应结束后,分布于胞外聚合物结合态中的Zn和Cu占其污泥胞外聚合物内总量的比例最高可达39.95％、58.77％.污泥胞外聚合物中松散结合态对Zn、Cu的吸附能力均强于紧密结合态;原污泥中Zn、Cu分别主要以铁锰氧化物结合态和硫化物及有机结合态存在,沥滤结束后,污泥中Zn和Cu均以残渣态存在.     

粉煤灰对猪粪堆肥重金属形态及浸出特性的影响

本研究以猪粪为原料,粉煤灰为钝化剂进行好氧堆肥,通过Tessier连续提取法与pH-依赖性浸出实验,研究粉煤灰对堆肥前后重金属形态及不同pH条件下重金属的浸出特性的影响。结果表明,粉煤灰对Zn的钝化效果较Cu更为显著,与原料相比Zn的残渣态增幅为18.97%。堆肥的浸出实验表现出很强的pH依赖性,Cu、Zn和DOM的浸出浓度在中性条件下(pH 6~8)低,在酸性(pH6)和碱性(pH8)环境中高。在pH为3~9的范围内,添加粉煤灰的实验组中Cu和Zn的浸出浓度低于对照组。因此,添加粉煤灰可降低堆肥重金属的浸出风险。     

基于生物淋滤的城市污泥重金属溶出及形态迁移

利用生物淋滤法处理城市污泥,以生物淋滤过程中pH、ORP(氧化还原电位)变化以及重金属(Zn、Cu、Cd)溶出率为指标,考察淋滤菌接种比例、初始pH、淋滤时间对生物淋滤的影响,并分析了生物淋滤前后,重金属形态变化以及重金属的生物有效性和迁移性。结果表明富集筛选的嗜酸性氧化亚铁硫杆菌(A.f)可有效溶出污泥中的重金属。生物淋滤最佳条件为:初始pH=4.00,淋滤菌接种比例30%,重金属Zn,Cu,Cd在第10天的整体处理效果最优,溶出率分别达到75.30%、50.40%和74.44%。BCR形态分析表明:原污泥中Zn,Cu,Cd主要以弱酸提取态、可还原态和氧化态存在,残渣态较少;生物淋滤之后,3种重金属弱酸提取态、可还原态和氧化态含量有不同程度降低,其中,可还原态含量降低最为显著,残渣态基本无变化,并且淋滤后污泥中重金属氧化态及残渣态所占比例较淋滤前高,污泥稳定性得到提升。生物淋滤可以通过减少污泥中重金属含量和改变重金属形态降低其生物有效性和迁移性。     

废弃等离子显示屏玻璃中重金属化学形态分布

通过BCR3步和BCR4步连续提取法,对等离子体显示屏玻璃中重金属的化学形态进行研究。结果表明,BCR3步连续提取法对废弃等离子体显示屏玻璃中重金属的提取比BCR4步连续提取法更稳定。废弃等离子体显示屏玻璃中Zn、Cu和Ag化学形态分布存在差异。BCR3步和BCR4步连续提取法均认为Ag以残渣态为主要赋存形态,对环境影响比较小;Cu的可交换与弱酸可溶态或交换态和碳酸盐结合态含量较少,潜在的环境风险也比较小;BCR3步和BCR4步连续提取法对Zn的形态分布结果评价不一致,BCR3步连续提取法表明Zn主要以可交换与弱酸可溶态为主,对环境影响较大,而BCR4步连续提取法结果认为Zn是以铁锰氧化态为主要存在形态。     

燃烧条件对灰渣中重金属元素形态的影响

根据改进了的BCR连续提取法,重金属元素形态分为酸可提取态、氧化物结合态、有机物结合态和残渣态,实验研究了不同燃烧温度、空气流量和燃烧气氛对燃煤重金属(Cr、Mn、Ni、Cu、Zn、As、Cd和Pb)的形态分布和挥发特性的影响规律。结果表明:在原煤和灰渣中,各重金属元素均主要以稳定的残渣态存在;8种重金属元素的挥发性难易程度顺序为Pb、Cd、ZnAs、Cr、Ni、CuMn;燃烧温度从650℃升至1 050℃过程中,各重金属元素4种存在形态的逸出率逐渐升高,逸出率最低增大幅度为20%,最高达60%;随空气流量的增大,重金属元素的有机物结合态和残渣态加速分解和挥发,各重金属元素的逸出率不断增大;除元素Mn和Ni较易于在贫氧气氛中挥发外,元素Cr、Cu、Zn、As、Cd和Pb均在富氧气氛中比较易于挥发气化。     

环境因子对南水北调泵站调节池沉积物氮释放特征的影响研究

为考察环境因子对南水北调泵站调节池沉积物氮释放的影响，通过模拟实验分析在不同温度、pH和DO条件下沉积物总氮和氨氮释放情况，并采用连续分级提取法分析释放前后沉积物可转化态氮(TTN)中不同形态氮的变化情况。结果表明：随温度升高氮释放强度增加，30℃时氨氮和总氮释放强度分别是10℃时的2.17、1.98倍；温度为10℃时离子交换态氮(IEF-N)为氮释放的主要贡献形态，温度为20℃和30℃时弱酸可提取态氮(WAEF-N)为氮释放的主要贡献形态。中性条件(pH=7.0)沉积物氮释放强度最低，酸性条件(pH=5.0)氮释放强度高于碱性条件(pH=9.0),IEF-N为酸性、碱性、中性条件下氮释放的主要贡献形态。DO为4.0 mg/L时氨氮和总氮释放强度分别是DO为9.0 mg/L时的1.32、1.42倍；DO为4.0 mg/L时IEF-N为氮释放的主要贡献形态，DO为9.0 mg/L时WAEF-N更易释放。     

氧化亚铁硫杆菌对电子垃圾焚烧迹地重金属形态的影响

采用生物淋滤法处理电子垃圾焚烧迹地重金属严重污染的土壤。所用氧化亚铁硫杆菌是从矿坑废水中通过一系列培养、分离和纯化得到。实验结果表明，生物淋滤法可以有效地去除土壤中重金属Cu、Ph和Zn，去除率的大小顺序为Zn〉Cu〉Pb；采用五步连续提取法分析处理前后土壤中重金属的存在形态，结果表明，通过氧化亚铁硫杆菌处理受重金属污染的土壤，可以促使易移动的重金属结合态的溶解（可交换态、碳酸盐结合态和Fe—Mn氧化物结合态），并使难移动的重金属结合态向易移动的重金属结合态转变。     

高温堆肥与蚯蚓堆肥对城市污泥重金属形态的影响

采用高温堆肥和蚯蚓堆肥工艺，研究了城市污泥与锯末、粉煤灰或磷矿粉按不同比例混合堆肥前后重金属（Cu、Pb、Zn、Cd和As）交换态、碳酸盐结合态、铁锰氧化物结合态、有机结合态和残留态的变化。研究表明：高温堆肥和蚯蚓堆肥前后各试验污泥的重金属形态和含量呈现出不同的变化，都可以降低污泥中交换态Cu、Pb、Zn、Cd和As的含量；对于Cu和Pb，高温堆肥优于蚯蚓堆肥；对于Zn、Cd和As，蚯蚓堆肥优于高温堆肥。2种堆肥方式中，粉煤灰用量为10%的钝化效果优于20%，磷矿粉的钝化效果同粉煤灰一样。     

北运河表层沉积物对重金属Cu、Pb、Zn的吸附

首先分析了北运河6个采样点表层沉积物中重金属含量及相关基本特征。通过实验室模拟实验,利用分配系数Kd评价沉积物对重金属Cu、Pb、Zn的吸附特性,进一步考察了水体pH变化和有机质对重金属在北运河沉积物上吸附的影响。结果表明,沉积物中重金属的含量顺序为Zn>Cu>Pb,去除有机质后,沉积物对重金属的吸附能力显著降低,但各采样点中的重金属含量,沉积物对重金属吸附能力,以及沉积物中的有机质含量并没有明显相关性,这可能是因为不同采样点中有机质种类与结构不同导致的。总之,北运河沉积物对Pb有很强的吸附能力,其次是Cu和Zn,而且,Cu、Zn、Pb的吸附量随着pH的升高逐渐增大,水体pH值对于Zn的吸附影响更大。     

Accumulation and distribution of heavy metals in the grey mangrove,Avicennia marina (Forsk)Vierh: biological indication potential

The accumulative partitioning of the heavy metals Cu, Pb and Zn in the grey mangrove, Avicennia marina, were studied under field conditions. Copper and Pb were accumulated in root tissue to levels higher than surrounding sediment levels. Zinc was accumulated to levels reflecting sediment concentrations. Strong linear relationships existed for all metals in sediments with metals in root tissue. Accumulation of Cu in leaf tissue followed a linear relationship at lower sediment concentrations, with an exclusion or saturation mechanism at higher sediment concentrations. Lead showed little mobility to leaf tissue. Zn showed restricted accumulation in leaf tissue, which correlated with sediment concentrations. Decreases in sediment pH were found to increase Zn accumulation to root tissue. Increasing concentrations of Pb and Zn in sediments resulted in a greater accumulation of Pb to both root and leaf tissue. A. marina roots may be employed as a biological indicator of environmental exposure of Cu, Pb and Zn and leaves for Zn, with temporal monitoring.     

Copper amendments and soil ph affect distribution of different chemical forms of metals and their uptake by Swingle citrumelo seedlings

Abstract

This study was conducted to evaluate the effects of various rates of Copper (Cu) amendments (as CuSO₄.5H₂O at either 0, 25, 50, 100, 200, or 400 mg Cu kg^‐1) to soils with different pH values on the distribution of various chemical forms of Zinc (Zn), Iron (Fe), Manganese (Mn), and Aluminum (Al) in soils and their uptake by Swingle citrumelo citrus rootstock seedlings. The soils included Myakka fine sand (pH 5.70), Candler fine sand (pH 6.45), and Oldsmar fine sand (pH 8.16). The chemical forms of metals evaluated in this study included exchangeable, sorbed, organically bound, precipitated, and residual forms. An increase in Cu rates, lowered the pH in the Myakka and Candler fine sands, but not in the Oldsmar fine sand. This, in turn, resulted in an increase in the proportion of the readily soluble forms (the exchangeable + sorbed forms) of Zn and Mn, and decreased that of Fe in the Myakka and Candler fine sands. In those two soils, the organically bound forms of Zn, Fe, and Mn decreased with an increase in Cu rates. However, the proportion of readily soluble forms was not significantly influenced by increasing Cu rates in the Oldsmar fine sand. The total content of Zn, Fe, and Mn in citrus roots and that of Zn and Fe in the leaves, significantly decreased with an increase in Cu rates in the Myakka and Candler fine sands. In the Oldsmar fine sand, Cu rates through the entire range had no significant effects on the total contents of Zn, Fe, and Mn in the leaves or in the roots of Swingle citrumelo rootstock seedlings.     

Effects of bacterial activities on the release of heavy metals from contaminated dredged sediments

The potential impact of indigenous bacterial processes on the release of heavy metals from dredged sediment deposits was investigated. Batch re-suspension experiments were conducted in order to investigate the release of Zn, Cd, Cu and Pb from a polluted anoxic sediment submitted to oxidative perturbations. The concentrations of heavy metals, sulphate and dissolved organic carbon (DOC) were periodically recorded, and cell counts were performed to follow the evolution of several bacterial species. The specific effects of microbial processes were quantified by performing re-suspension assays on sterilised samples. Moreover, the effect of an initial acidification of the system was studied. The results showed that metal release was mainly due to oxidation of sulphide minerals contained in the sediment. Sulphur-oxidising bacteria such as Acidithiobacillus thiooxidans were identified to play a major role in the process, by enhancing the oxidation kinetic. However, the acid production resulting from these reactions was almost totally buffered by the dissolution of the calcite present in the sediment. Copper was released to a lesser extent, and a strong association with organic matter was observed. Lead was not observed in solution, because of its low solubility at neutral conditions and of its re-adsorption on the solid phase. The initial acidification of the system resulted in an faster growth of the acidophilic A. thiooxidans. A subsequent pH drop originating from microbial processes was then observed during the first stages of the experiment. As a consequence, drastic increases in metal (Zn, Cd) release were observed.     

Leaching behaviour of Cd, Cu, Pb and Zn in surface soils derived from dredged sediments

Leaching of heavy metals from land-disposed dredged sediment spoils is a potential environmental hazard. The leaching behavior of Cd, Cu, Pb and Zn in surface soils sampled from abandoned dredged sediment disposal sites was assessed. Using simple mass-balance calculations, the significance of the leaching test results with respect to metal migration into underlying clean soil was appraised. The potential leachability, defined as the amounts released at constant pH 4, decreased in the order (% of total contents): Zn (58%) approximately equal to Cd (49%)>Cu (5%) approximately equal to Pb (2%). The kinetics of metal release were determined in a cascade shaking test using de-mineralized water acidified to pH 4 (HNO(3)). Metal concentrations in the leachates were low and metal migration was, assuming uniform convective flow, predicted to be of no environmental concern. It is emphasized that any long-term prediction of metal migration is uncertain.     

Metal contamination and solid phase partitioning of metals in urban roadside sediments

This study was undertaken to assess the anthropogenic impact on metal concentrations of urban roadside sediments (N = 633) in Seoul city, Korea and to estimate the potential mobility of selected metals (Zn, Cu, Pb, Cr, Ni, and Cd) using sequential extraction. Comparison of metal concentrations in roadside sediments with mean background values in sediments collected from first- or second-order streams in Korea shows that Zn, Cu and Pb are most affected by anthropogenic inputs. The 206Pb/207Pb ratios of roadside sediments (range = 1.1419-1.1681; mean 1.1576 +/- 0.0068) suggest that Pb is mainly derived from industrial sources rather than from leaded gasoline. A five-step sequential extraction of roadside sediments showed that Zn, Cd and to a lesser degree Ni occur predominantly in the carbonate bound fraction, while Pb is highest in the reducible fraction, Cu in the organic fraction, and Cr in the residual fraction. It was found that the concentrations in the readily available exchangeable fraction were generally low for most metals examined, except for Ni whose exchangeable fraction was appreciable (average 15.2%). Considering the proportion of metals bound to the exchangeable and carbonate fractions, the comparative mobility of metals probably decreases in the order of Zn > Ni > Cd > Pb > Cu > Cr. As potential changes of redox state and pH may remobilize the metals bound to carbonates, reducible, and/or organic matter, and may release and flush them through drain networks into streams, careful monitoring of environmental conditions appears to be very important. With respect to ecotoxicity, it is apparent the Zn and Cu pollution is of particular concern in Seoul city.     

Effect of overlying water pH, dissolved oxygen, salinity and sediment disturbances on metal release and sequestration from metal contaminated marine sediments

Experiments were undertaken to examine the key variables affecting metal release and sequestration processes in marine sediments with metal concentrations in sediments reaching up to 86, 240, 700, and 3000 mg kg(-1) (dry weight) for Cd, Cu, Pb and Zn, respectively. The metal release and sequestration rates were affected to a much greater extent by changes in overlying water pH (5.5-8.0) and sediment disturbance (by physical mixing) than by changes in dissolved oxygen concentration (3-8 mg l(-1)) or salinity (15-45 practical salinity units). The physical disturbance of sediments was also found to release metals more rapidly than biological disturbance (bioturbation). The rate of oxidative precipitation of released iron and manganese increased as pH decreased and appeared to greatly influence the sequestration rate of released lead and zinc. Released metals were sequestered less rapidly in waters with lower dissolved oxygen concentrations. Sediments bioturbated by the benthic bivalve Tellina deltoidalis caused metal release from the pore waters and higher concentrations of iron and manganese in overlying waters than non-bioturbated sediments. During 21-day sediment exposures, T. deltoidalis accumulated significantly higher tissue concentrations of cadmium, lead and zinc from the metal contaminated sediments compared to controls. This study suggests that despite the fact that lead and zinc were most likely bound as sulfide phases in deeper sediments, the metals maintain their bioavailability because of the continued cycling between pore waters and surface sediments due to physical mixing and bioturbation.     

A comparison of physiologically based extraction test (PBET) and single-extraction methods for release of Cu, Zn, and Pb from mildly acidic and alkali soils

In vitro digestion test can be applied to evaluate the bioaccessibility of soil metals by measuring the solubility of the metals in synthetic human digestive tract. Physiologically based extraction test (PBET), composed of sequential digestion of gastric and intestinal phase, is one of the frequently used in vitro digestion tests. In this study, the PBET was chosen to determine the bioaccessibility of Cu, Zn, and Pb in 14 mildly acidic and alkali (pH 5.87–8.30) soils. The phytoavailability of Cu, Zn, and Pb in the same soils was also measured using six single-extraction methods (0.1 M HNO₃, 0.4 M HOAc, 0.1 M NaNO₃, 0.01 M CaCl₂, 0.05 M EDTA, and 0.5 M DTPA). The extraction efficiencies of the methods were compared. The PBET had a strong ability to extract metals from soil, which was much greater than neutral salt extraction and close to dilute acid and complex extraction in spite of the last 2 h neutral intestinal digestion. The amounts of bioaccessible Cu, Zn, and Pb in the gastric phase and in the gastrointestinal phase were both largely determined by the total content of soil Cu, Zn, and Pb. But the results of gastrointestinal digestion reflected more differences resulting from element and soil types than those of gastric digestion did. It was noticed that most of variations in the amounts of soil Cu, Zn, and Pb extracted by EDTA were well explained by the total soil Cu, Zn, and Pb, as same as the PBET. Moreover, the solubility of Cu, Zn, and Pb in the gastric phase and gastrointestinal phase were all positively linearly correlated with the results of EDTA. It was suggested that EDTA extraction can be used to predict the bioaccessibility of Cu, Zn, and Pb in mildly acidic and alkali (pH?>?5.8) soils, and the PBET and EDTA could be applied to measure, in a certain extent, the bioaccessibility and phytoavailability of Cu, Zn, and Pb in mildly acidic and alkali (pH?>?5.8) soils at the same time.     

Contamination status and potential release of trace metals in a mangrove forest sediment in Ho Chi Minh City,Vietnam

Can Gio district is located in the coastal area of Ho Chi Minh City, southern Vietnam. Discharge of wastewater from Ho Chi Minh City and neighboring provinces to the rivers of Can Gio has led to concerns about the accumulation of trace metals (As, Cu, Cr, Ni, Pb, and Zn) in the coastal sediments. The main objective of this study was to assess the distribution of As, Cu, Cr, Ni, Pb, and Zn in surface and core sediments and to evaluate the contamination status in relation to local background values, as well as the potential release of these selected trace metals from sediments to the water environment. Sediment characteristization, including determination of fine fraction, pH, organic matter, and major elements (Al, Fe, Ca, K, Mg, and S), was carried out to investigate which parameters affect the trace metal enrichment. Fine fraction and Al contents were found to be the controlling proxies affecting the distribution of trace metals while other sediment characteristics did not show any clear influence on trace metals’ distribution. Although As concentrations in the sediments were much higher compared to its reference value in other areas, the enrichment factor based on local background values suggests minor contamination of this element as well as for Cr, Cu, and Pb. Risk assessment suggested a medium to very high risk of Mn, Zn, and Ni under acidification. Of importance is also that trace metals in sediments were not easily mobilized by organic complexation based on their low extractabilities by ammonium-EDTA extraction.

     

Changes in speciation and leaching behaviors of heavy metals in dredged sediment solidified/stabilized with various materials

Solidification/stabilization (S/S) of sediments is frequently used to treat contaminants in dredged sediments. In this study, sediment collected from the Pearl River Delta (China) was solidified/stabilized with three different kinds of functional materials: cement, lime and bentonite. Lime primarily acted via induced increases in pH, while cements stabilization occurred through their silicate-based systems and the main function of bentonite was adsorption. The speciation and leaching behaviors of specific heavy metals before and after S/S were analyzed and the results showed that the residual speciation of Cd, Cr, Ni, Pb and Zn increased in all treatments except for Cu, as the exchangeable speciation, carbonate-bound speciation and Fe-Mn-oxide-bound speciation of Cu (all of which could be stabilized) were less than 2 % of the total amount. Pb leaching only decreased when pH increased, while the mobility of Cr and Ni only decreased in response to the silicate-based systems. The leached portion of the Fe-Mn-oxide-bound speciation followed the order Zn?>?Cu?>?Ni/Cd?>?Pb?>?Cr. The leached portion of organic-matter-bound species was less than 4 % for Cd, Cr, Ni and Pb, but 35.1 % and 20.6 % for Cu and Zn, respectively.