Distribution of Heavy Metals in Near-Shore Sediments of the Swan River Estuary,Western Australia

Estuarine systems adjacent to urban areas are at risk of contamination by contaminants from anthropogenic sources, such as heavy metals. We anticipated that the sediments of the Swan River estuary, which runs through metropolitan Perth in Western Australia, would show metal contamination related to industrialization and inputs of stormwater. Total Cu, Pb and Cd concentrations, and Cu, Pb, Cr and Zn inoperationally-defined fractions, were determined inseparate sampling exercises in near-shore sediments ofthe upper Swan River estuary.Total metal concentrations in sediments were not high (maximum values of 297 mg kg^-1 for Cu, 184 mg kg^-1 for Pb and 0.9 mg kg^-1 for Cd) when compared with Australian environmental assessmentguidelines for soils. On the basis of linear regressions between sediment metal concentrations andphysicochemical properties of the sediments (pH, organic carbon, particle size distribution), no single parameter could explain the variation in metal concentrations for all metals. Sediment organic carbon content was positively correlated with Cu concentration; Cu concentrations also increased significantly with increasing clay content anddecreasing sand content. Pb concentrations showed a significant increase with increasing sediment pH, and were approximately three-fold higher in sediments adjacent to stormwater drain outfalls than in sediments remote from drains; no such effect was observed for Cu or Cd. No effect of distance downstream was observed. Sequential extraction of sediments showed that most of the metals were in relatively immobile forms, for example bound to Feoxides, or only extractable by aqua regia. The enhanced concentrations of Pb near stormwater outfalls suggest that vehicle-derived Pb may be an important contributor of Pb to the estuary.     

Fractionation of copper and uranium in organic and conventional vineyard soils and adjacent stream sediments studied by sequential extraction

Purpose

Particularly in organic viticulture, copper compounds are intentionally released into the environment as fungicide, whereas uranium originates from conventional phosphate fertilization. Both activities contribute to the metal contamination in wine-growing areas. This pilot study aimed to better understand how soil properties influence the presence and environmental fate of copper and uranium with respect to viticultural management.

Materials and methods

We characterized metal binding forms, i.e., their association with different soil constituents, in organically and conventionally cultivated vineyard soils and adjacent upstream and downstream sediments. The available metal fraction and the fractions associated with manganese oxides, organic matter, iron oxides, and total contents were extracted sequentially.

Results and discussion

Total soil copper ranged from 200 to 1600 mg kg^?1 with higher contents in topsoil than subsoil. The majority of copper (42–82%) was bound to soil organic matter. In all fractions, copper contents were up to 2-fold higher in organic than in conventional vineyards, whereas the sediment concentrations were independent of the adjacent viticultural management. A net increase of copper in downstream sediments was found only when water-extractable organic carbon (WEOC) in an adjacent vineyard was elevated. With 11 ± 1 mg kg^?1, total uranium was 25% higher in conventional than in organic vineyard soils. Its affinity to iron or WEOC potentially rendered uranium mobile leading to a substantial discharge to downstream sediments.

Conclusions

Translocation of copper and uranium from vineyards into adjacent stream sediments may rather be attributed to WEOC and iron contents than the viticultural management. Follow-up studies should scrutinize the processes driving metal availability and transport as well as their interaction at the aquatic–terrestrial interface.

     

Trace metals in sediments and aquatic plants from the Xiangjiang River, China

Purpose

The metal concentrations and Pb isotopic composition in sediments and plants from the Xiangjiang River, China, were investigated to understand the contamination and potential toxicity of metals in sediments; to determine the accumulation and distribution of metals in plant tissues; and to trace the possible pollution source of Pb in sediments and plants.

Materials and methods

Sediments and plants were collected from 43 sampling sites in the study region. After sediments were air-dried and passed through a 63-??m sieve, they were acid-digested and DTPA-extracted for determination of total and bioavailable metals. The plants were separated into roots, leaves, and stems; dried; cut into pieces; and digested with HNO₃?CH₂O₂. Metals (As, Cd, Cr, Cu, Ni, Pb, and Zn) and Pb isotopic composition were analyzed by inductively coupled plasma-mass spectrometry.

Results and discussion

Maximum As, Cd, Cr, Cu, Ni, Pb, and Zn concentrations in sediments were 47.18, 55.81, 129.5, 161.6, 160.4, 430.7, and 1,098.8?mg?kg^?1, respectively. The bioavailable fractions of As, Cd, Cu, Pb, and Zn had significant linear relationship with their corresponding total contents in sediments while no significant relationship was observed between bioavailable and total contents of Cr and Ni. In general, plant tissues showed higher As, Cd, Cu, Pb, and Zn concentrations and lower Cr and Ni concentrations compared with sediments. The ²⁰⁶Pb/²⁰⁷Pb ratios decreased in the order of total > bioavailable > stems ?? leaves > roots. A strong linear correlation was observed between the ²⁰⁸Pb/²⁰⁶Pb and ²⁰⁶Pb/²⁰⁷Pb ratios of the plant tissues, sediments, and the possible pollution sources of Pb in the Xiangjiang River.

Conclusions

As, Cd, Cu, Pb, and Zn demonstrated higher contamination levels in sediments and plants compared with Cr and Ni. Cd had highest potential ecological risk. The Pb from anthropogenic sources with low ²⁰⁶Pb/²⁰⁷Pb ratios was preferentially associated with the bioavailable fractions in sediments and accumulated in roots. The Pb in plant tissues is mainly derived from the Pb in sediment and is taken up through the sediment-to-root pathway.     

Transformation of Lead Solid Fraction in the Rhizosphere of Elsholtzia splendens: The Importance of Organic Matter

The rhizosphere, enriched in organic matter, is the bottleneck of metal transfer in the soil–plant system. However, the transformation of metal fractions in the rhizosphere and the mechanisms that are involved, notably the role of organic matter, are poorly known. In this study, the solid-phase fractionation of lead (Pb) in the rhizosphere and non-rhizosphere soil of Elsholtzia splendens in a Pb-contaminated soil was investigated using a nine-step selective sequential extraction method in a pot experiment. Compared to the non-rhizosphere soil, there were measurable increases in Pb-fulvic complexes, Pb-humic complexes, organic Pb, and amorphous Pb but no significant changes in other forms of Pb in the rhizosphere soil. Pb-fulvic complexes and organic Pb, increasing from 397 to 438 mg kg^?1 and 229 to 258 mg kg^?1, respectively, showed a stronger accumulating trend than Pb-humic complexes and amorphous Pb, with an increase from 15.9 to 17.3 mg kg^?1 and 6.04 to 7.80 mg kg^?1 respectively, in the rhizosphere soil relative to non rhizosphere soil. These results may be mainly due to the enrichment of organic matter in the rhizosphere soil, resulting from root exudation and the enhanced turnover of microorganisms. The accumulation of Pb-fulvic complexes in the rhizosphere soil increases the potential phytoavailable pool, thus likely facilitating the phytoextraction of Pb in metal-contaminated soil.     

水稻子实对不同形态重金属的累积差异及其影响因素分析

在分析成都平原核心区土壤重金属(Cd、Cr、Pb、Cu、Zn)全量、各形态含量及相应点位种植的水稻子实重金属含量的基础上,通过统计分析、空间插值及线性回归方程的模拟,研究了土壤Cd、Cr、Pb、Cu、Zn全量的空间分布状况、各形态重金属含量统计特征,以及水稻子实对重金属各形态的累积差异及其影响因素。结果表明,成都平原水稻土重金属污染较轻,除Cd外,均低于国家土壤环境质量二级标准。土壤中重金属的可交换态含量均较低,Cd主要以铁锰氧化态存在,Cr、Cu、Zn、Pb主要以残渣态存在。水稻子实对5种重金属的累积效应顺序为:Cd>Zn>Cu>Pb>Cr。与水稻重金属累积关系密切的重金属活性形态(可交换态、碳酸盐结合态、铁锰氧化物结合态和有机物结合态)主要有:Cd的碳酸盐结合态、Cr的可交换态、Pb的有机物结合态和Cu的碳酸盐结合态含量;Zn各活性形态对水稻子实含量的影响不明显。土壤理化性质对不同活性形态重金属元素的影响效应各不相同。活性态Cd主要受有机质、pH和容重的影响;活性态Cr与pH、有机质、CEC和容重密切相关;活性态Pb与有机质、容重、中细粉粒、砂粒等均有密切的关系;Cu的活性主要受粘粒、有机质含量的影响;Zn的有效性主要受pH、有机质、砂粒、容重的影响。总的看来,对土壤Cd、Cr、Pb、Cu、Zn各活性形态含量影响效应较强的是有机质、pH、容重,而与土壤吸附性能密切相关的颗粒组成、CEC的影响不甚明显。     

Lead-organic matter interactions in a mollisol

Samples from the surface layer (0–15 cm) of a cultivated Typic Haplaquoll, collected in the fall of 1975 from field plots amended with variable amounts of Pb in the spring of 1969 and with ground corn cobs in 1973 and 1974 (22.4 tons ha^?1), were analyzed for organic N, total Pb, exchangeable- and soluble-Pb, specifically-adsorbed Pb, and organically-bound Pb. Highly-significant correlations were obtained between organic N and soil Pb concentrations, from which it was concluded that the applied Pb resulted in small increases in the organic matter content of the soil. The most probable mechanism was believed to be through the formation of biologically-resistant Pb-organic matter complexes. At low amounts of soil Pb (20–30 μg g^?1 range), approximately 30% of the soil Pb occurred in organic linkages but the proportion increased steadily up to 400 μg g^?1 and gradually leveled off thereafter. The conclusion was reached that progressive contamination of the test soil by exogenous Pb additions, such as from automobile exhaust near traffic highways, would have little effect on plant available forms until soil Pb concentrations reached about 100 μg g^?1, following which the concentration in the soil solution would be related to and controlled by the size of the organic pool.     

Characterization of Heavy Metals and Sulphur Isotope in Water and Sediments of a Mine-Tailing Area Rich in Carbonate

Mine tailings can provide a long-term source of environmental contamination. Lead-zinc mine tailings can represent a source of toxic elements-Pb and Zn through mobilization into surface water, and then into downstream rivers. Previous studies have shown that migration of heavy metals can be mitigated by carbonate rock. This research investigates the characterization of heavy metals and sulphur isotope in a downstream river of the Shanshulin Pb-Zn mine, which is located in Guizhou province in China, a typical carbonate area in the world. A slight alkalinity (pH > 8) of the river water is maintained owing to the carbonate rich country rocks. The results of this study show that heavy metals in water can be strongly adsorbed by suspended solids and therefore decrease more quickly than in sediments. Pb and Zn contents in water close to the waste pile are 6780 μg L^-1 and 324 μg L^-1 (Pb and Zn in water not affected by mine waste piles are only 3.71 μg L^-1 and 11.6 μg L^-1), respectively, meaning that the water is severely contaminated by the pile. Thirty kilometers downstream Pb and Zn contents in water drop quickly to 3.15 μg L^-1 and 16.4 μg L^-1. In contrast, Pb and Zn contents in sediment close to the waste pile are 4553 mg kg^-1 and 7971 mg kg^-1, respectively, and are still high 30 km downstream with measurements of 3334 mg kg^-1 and 7268 mg kg^-1 , respectively (Pb and Zn contents in sediment not affected by mine waste piles are only 20 mg kg^-1 and 120 mg kg^-1). This indicates that the impact of tailings on the sediment can be much further than on water. In sediment, Pb exists mostly as carbonate and oxide fractions, Zn mostly as sulfide+organic fraction, and Cu mostly as sulfide+organic, residual and carbonate fractions. Sulphur characteristics indicate that sulphur in sediment originates from mine tailing, soil and suspended solids in other tributaries, whereas sulphur in water originates from mine tailing dissolution, spring water, rain water and dissolution of gypsum. In conclusion, the environmental impact of mine tailing can be indicated by heavy metals content, sulphur content and sulphur isotope of sediment. On the other hand, heavy metal content, sulphur content or sulphur isotope of water are possibly not good indicators for mine impact due to mitigation of carbonate rocks, sorption of heavy metals, as well as interference of gypsum layers.     

copper,lead and zinc distribution in soils and sediments of the south-western coast of the río de la plata estuary

Background, Aim and Scope.  The compositional study of suspended matter in water from rivers of different latitudes and climates has revealed that the fine fraction reflects both substrate lithology from source areas or topsoil composition along the course. Metal distribution patterns are also strongly related to the clay mineral fate in fluvial aquatic systems. For the particular case of the coastal area of the Río de la Plata estuary in South America, previous studies have, on the one hand, focused on the analysis of distribution patterns of heavy metals in bottom river sediments and, on the other hand, on the assessment of metal contents in topsoils. The present study was conducted to evaluate the Cu, Pb and Zn distribution in soils and sediments from four drainage basins crossing two differentiated geomorphologic units composed of unconsolidated materials and to understand the metal behaviour. Methods  Data used included the existent, self-produced soil and sediment data sets (grain size, organic matter and Cu, Pb and Zn contents from 124 samples). Analyses were performed by using standardised methods: grain size analysis by sieving and settling; organic matter content based on the reduction of dichromate ion followed by titration; metal content by atomic absorption spectrophotometry following acid digestion. Results and Discussion. The average (% w/w) clay and organic matter content were 45.9 ± 17.1 and 1.5 ± 1.7 for sediments and 32.0 ± 19.8, and 7.5 ± 7.6 for soils, respectively. The raw mean metal concentrations (mg-kg^-1 dry weight) for sediments and soils were: Cu: 28.02 ± 27.28, 32.08 ± 21.64; Pb: 32.08 ± 46.94, 68.44 ± 69.25 and Zn: 83.09 ± 150.33, 118.22 ± 74.20, respectively. A good correlation for each clay-normalised metal concentration was found between soil and sediments using regression analysis considering average data for each basin sampling site (r > 0.89, p < 0.05). A comparison between metal concentration levels taking into account geomorphologic units by a t independent sample test showed significant differences for the normalised soil-sediment metal data (p < 0.001), responding to differences in grain size, clay mineralogy, organic matter and neoformed Fe-Mn oxide composition. Conclusion, Recommendation and Outlook  A clear parenthood between the topsoils and the bottom sediments in the study area was found. The Argiudolls from the inner zone are frequently affected by rainwater erosion, which washes the fine materials with sorbed metals and carries them to the streams. These watercourses reach the flat coastal plain, where soil flooding and bottom sediment depositional processes predominate. Here, both soils and bottom sediments are enriched in clay, organic matter and metals. The topography and lithology, under the environmental conditions of a temperate and humid climate control the fate of metals within these small basins. The influence of the physical media on the distribution and fate of pollutants should not be minimised in the understanding of the governing processes from natural systems.     

Road-deposited sediment, soil and precipitation (RDS) in Bratislava, Slovakia: compositional and spatial assessment of contamination

Background, aim and scope  The urban environment in Bratislava is, in association with rapid urbanisation and industrialisation, significantly influenced by several potential sources of pollution, including automobile exhaust and industry emmissions. Urban road-deposited sediments contain many potentially toxic elements such as Pb, Cr, Cu, Zn and also Fe at concentrations much higher than in soil. In this study, the chemical composition and spatial variability of road-deposited sediments in urban area of Bratislava were assessed for the elements As, Cd, Cr, Cu, Hg, Ni, Pb, Fe and Mn. Additional evaluation of archive data for soil, snow and atmospheric dust was undertaken to provide an integrated view on urban environment contamination. Materials and methods  Urban road-deposited sediments (RDS) were collected during summer 2003 and 2004 mainly from major city crossroads. RDS samples were analysed for total metal content, pseudo-total metal content (HNO₃ digestion) and by a sequential extraction method, grain fraction composition and mineralogical composition (X-ray analysis). Metal concentrations in soil and snow samples from urban and non urban city area were compared. Results and discussion  The highest concentrations for all metals were found in the finest RDS fraction (<0.125 mm). Whilst in the fraction <1 mm mean concentrations of Cr, Cu and Pb reached 55.2, 143.8 and 34.4 mg kg⁻¹, respectively, for the fraction <0.125 mm, markedly higher contents of these elements were documented at the level of 86.8, 218.4 and 63.1 mg kg⁻¹, respectively. The soil contents of potentially toxic risk elements in the urban area including As, Cr, Cu, Fe, Hg, Mn, Ni, Pb and Zn were higher than in the non-urban area (except for Cd with similar contents). This distribution pattern of evaluated chemicals in urban and non-urban area is more evident in the case of winter precipitation (snow). The snow concentrations of As, Cr, Cu, Fe, Mn, Pb and Zn in the urban area were two tot five times higher than in non-urban area. Conclusions and recommendations  Monitoring of road-deposited sediments, dust, soil and precipitation has confirmed the significant contamination of the urban environment in Bratislava with potentially toxic elements that can pose a threat for the health of its residents. Future works should be based on analyses of temporal variability of RDS and analyses of organic matter content.     

Heavy metal pollution of soil from industrial and municipal wastes in Chittagong,Bangladesh

Heavy metal pollution was assessed in soils collected from 0–15, 15–30 and 30–45-cm depths of three industrial (FMC, PMC and CMC), and two municipal (BSD and MLF) waste disposal sites around Chittagong city in 2008. Soils were analysed for pH, organic carbon, total nitrogen, available P, exchangeable Ca, Mg, K and Na, and total Cd, Pb, Cu, Mn and Zn. The pH, organic C, total N, available P, total Cd, Pb, Cu and Mn, and contamination indices for Cd and Pb varied significantly among sites. Mean Cd, Pb, Cu, Mn and Zn were in the range 0.5–1.9, 54–86, 25–50, 261–624 and 204–330 mg kg^?1, respectively. Contamination indinces for Cd, Pb, Zn and Cu were estimated by comparison with respective threshold values. Contamination indices showed that the sites MLF and FMC had low Cu contamination. Other sites were not contaminated with thisheavy metal. All sites except PMC were highly contaminated with Cd, FMC was moderately contaminated and the others had low Pb contamination. FMC was highly contaminated, but the others were moderately contaminated with Zn. The integrated contamination index revealed that PMC had low contamination and the other sites were highly contaminated with heavy metals.     

Fractionation and Distribution of Metals in Guadiamar River Sediments (SW Spain)

Traditionally, the Guadiamar River (Seville, Southwest Spain) has received pollution from two different sources, in its upper section, from a pyrite exploitation (Los Frailes mine) and, in its lower section, from untreated urban and industrial wastes and from intensive agricultural activities. In 1998, the accidental spillage of about 6 million m³ of acid water and sludge from mine tailings to Guadiamar River worsened the pollution of an already contaminated area. The main polluting agents of the spillage were heavy metals. The total concentration of a metal provides scarce information about the effects on environmental processes or about the toxicity of the sediment samples. A more sophisticated fractionation of the sediment samples based on a species distribution can help to understand the behaviour and fate of the metals. This article describes a distribution study of the metals Al, Cd, Cu, Fe, Mn, Pb and Zn by fractionation analysis of sediments from eleven sample sites alongside the Guadiamar Riverbed. The samples were collected in summer 2002, four years after the spillage and after the area had been cleaned. Sequential extraction analysis resulted in the definition of four fraction categories: exchangeable metal (the most available fraction), reducible metal (bound to hydrous oxides of Fe and Mn), oxidizable metal (bound to organic matter and sulphides) and a residual fraction (bound to minerals). Significant increases in the available fraction of several potentially toxic metal ions like Cd, Mn and Zn were found. The distribution pattern was variable along the River. At the site closest to the mineworks, the soluble forms of Cd, Mn and Zn were significantly more abundant that those downstream. Cu and Pb were present in the reducible fraction while Fe was present associated in the residual fraction.     

秦岭神安沟矿区沟道地表水和沉积物中重金属分布形态研究

为了探讨重金属在矿山水体环境中的富集规律,以秦岭神安沟矿区沟道地表水、沉积物中的重金属为研究对象,测试了各类重金属含量,并利用Tessier五步连续萃取法分析了沉积物中重金属的5种形态,旨在为该矿区环境恢复治理提供参考。结果显示,未受采矿活动影响的对照区地表水与沉积物均未检出Zn、Pb、Cd,对照区未受污染。受开采活动影响的上、中、下游地表水、沉积物受到Pb、Cd不同程度的污染,下游地表水Pb、Cd分别超标5.3倍、43.3倍,不符合农田灌溉用水水质要求;上、中、下游沉积物中重金属污染负荷指数均达Ⅲ级,沟道沉积物已受到严重污染。沉积物中重金属形态分布特征为：Zn、Cd以有机结合态所占比例最高,Pb以铁锰氧化物结合态所占比例最高,Zn、Pb的生物有效性高。由此得出下游地表水不适于灌溉。由于矿方目前已终止尾矿库淋滤水向沟道排放,沉积物中各类重金属含量已趋于稳定,矿区神安沟地表水、沉积物重金属污染严重,亟需治理恢复。     

荣成天鹅湖沉积物中重金属的分布特征研究

通过对表层沉积物中重金属及粒度的分析,研究了荣成天鹅湖重金属的含量水平及分布特征,并对沉积物的环境质量进行了初步评价。结果表明,天鹅湖重金属的总体水平较低,Cd、Cr、Pb、Cu、Zn的平均含量均低于国家海洋沉积物I类质量标准,其中Cr和Pb存在轻度污染。Cd、Cr、Ni、Pb、Cu、Zn的含量范围分别为0～0.84、1.75～116.11、1.50～29.06、17.36～27.25、2.00～34.98mg.kg-1和11.48～92.61mg.kg-1,平均含量排序为Zn〉Cr〉Pb〉Cu、Ni〉Cd。天鹅湖重金属的富集状况与沉积物的粒度以及人类活动密切相关,大部分元素的高值区出现在颗粒较细的湖中央以及污染严重的西北部,东南部含量较低。相关分析表明,各重金属之间的相关性较好,其中Cd、Cu、Mn、Zn、Fe间呈高度的正相关,空间分布规律相似;重金属与有机质、粘粒含量呈极显著正相关,而与砂粒呈极显著负相关。根据加拿大制定的沉积物评价标准,天鹅湖沉积物中Cr具有较大的生态危害性。     

贵州铅锌冶炼区农田土壤镉铅有效性评价与预测模型研究

农田土壤重金属的不同活性库分布和土壤-溶液分配模型能够提供重金属的生物有效性和浸出能力等信息,因而在风险评价和修复实践中非常重要。本研究采集毕节铅锌冶炼区30个历史污染农田土壤,同时在贵州省范围内采集5种类型背景土壤制成不同浓度Pb/Cd单一污染土壤;经3个月老化,分别测定由0.43 mol/L HNO_3、0.1 mol/L HCl和0.005 mol/L DTPA提取态表征的重金属反应活性库以及由0.01 mol/L CaCl_2提取态表征的直接有效库;分析铅锌冶炼区农田土壤Cd、Pb不同有效库的分布特征,建立土壤-溶液分配模型,并讨论土壤理化性质的影响。结果表明:历史污染土壤中Cd和Pb的直接有效库占全量比例分别比人工污染土壤低4倍和223倍,然而历史污染土壤Cd和Pb的反应活性库(0.43 mol/L HNO_3提取态)占全量比例要高于相应人工污染土壤中的比例。拓展Freundlich形式吸附方程能够准确描述各提取态表征的Cd和Pb活性库与土壤全量Cd和Pb的关系,尤其0.43 mol/L HNO_3提取方法能够克服土壤理化性质对土壤Cd和Pb提取的影响而与总量建立极显著的相关关系。pH依附性Freundlich吸附方程准确描述了Cd和Pb的总反应活性库分别与土壤溶液Cd和Pb的关系,对于Pb而言,还要考虑土壤有机质和有效磷的影响。本研究可为矿区农田土壤重金属污染评价、修复以及农田有效态标准的推导提供参考。     

Environmental Impacts of Heavy Metal Discharges from a Smelter in Deûle-canal Sediments (Northern France): Concentration Levels and Chemical Fractionation

Heavy metal pollution in sediments derived from the Deûle canal and sampled at different sites not far from a smelting plant has been examined in the present work in order to identify the sources of these metals and to assess the sediment environmental quality. The total concentrations of lead, zinc, cadmium, thallium, indium and tin in the samples were determined using inductively coupled plasma-atomic emission spectroscopy (ICP-AES). Our investigations have revealed that metal pollution is readily apparent in the studied sediments, with metals contents largely exceeding those measured in the background soils: maximum values are obtained for sediments collected near the industrial zone. The chemical forms of Pb, Zn, Cd, Tl, In and Sn in these sediments have also been studied using a sequential extraction method in order to evaluate their possible mobility, bioavailability and toxicity in this aquatic environment. Overall, the averaged fractionation of Pb and Zn is dominated, in a decreasing order, by the easily reducible, oxidizable and carbonate fractions. The importance of oxidizable phase (which is assumed to be composed mainly of organic matter and sulphides) in the Pb and Zn fractionations has been confirmed by the detection of X-ray diffraction peaks ascribed to galena (PbS) and wurtzite (ZnS) in contaminated sediment samples. Anthropogenic Tl, In, and Cd are mainly retained in Fe–Mn oxides/hydroxides, whereas anthropogenic Sn predominates in aluminosilicates/clays. We suspect that elevated percentage levels of Pb, Zn, Cd and In in the reducible fraction constitute a particular potential risk to this aquatic environment in case early diagenetic phenomena (that are observed in the sedimentary material) and physical disturbances (that occur in the water column) both take place strongly in the medium.     

Identification of the sources of metals and arsenic in river sediments by multivariate analysis and geochemical approaches

Purpose

Frequent mining activities and higher background values in soil have led to the contamination of the sediments of some rivers in southwest China by several metals and arsenic (As). This study combined multivariate analysis with geochemical approaches to differentiate mining activity from other sources, which may aid to evaluate the effectiveness of reducing mining release.

Materials and methods

Sixteen sediment samples were collected along the Yuan River, China. The total concentrations of lead (Pb), zinc (Zn), copper (Cu), cadmium (Cd), chromium (Cr), mercury (Hg), and As were measured by inductively coupled plasma-atomic emission spectrometer (ICP-AES). The Pb isotopic composition was measured using a thermal ionization mass spectrometer (TIMES). Both geochemical approaches and multivariate statistical analysis were used to identify the sources of these metals. The fractionation of Pb was determined through a Community Bureau of Reference (BCR) sequential extraction procedure to aid the identification of the sources.

Results and discussion

The concentrations and enrichment factors (EFs) of Pb, Zn, Cu, Cd, and As in the middle reach of the river were higher than those at the other sites, indicating anthropogenic sources. The factor analysis (FA) extracted “mining and smelting,” “mixture of anthropogenic and natural,” and “natural” factors. The Pb isotope composition of metal ores was similar (²⁰⁶Pb/²⁰⁷Pb?<?1.190 and ²⁰⁸Pb/²⁰⁶Pb?>?2.023) to that found in the sediments in the middle reach, indicating anthropogenic sources of mining activities. Compared with the narrow ranges of the δ³⁴S ratios in the bedrock (+8.5 to +9.3?‰) and the metal ores (?1.4 to +1.9?‰), the sediment samples presented a relatively wide range of δ³⁴S ratios from ?2.6 to +9.2?‰ with a mean of +2.6?‰, which suggests a mixed composition. The BCR sequential extraction procedure revealed that the proportion of the extractable fraction in the sediments in the middle reach was higher than that in other sites, suggesting anthropogenic sources as the cause of contamination in the study area.

Conclusions

Lead, Zn, Cu, Cd, Cr, Hg, and As are mainly derived from natural materials in the upstream region. In the middle reach, these elements are the result of anthropogenic activities, particularly activities associated with the mining industry. In the downstream region, the origin of these elements is considered to be a mixture of anthropogenic and natural sources. In addition to geochemical approaches and multivariate statistical analysis, the BCR sequential extraction method is an effective procedure for the identification of the anthropogenic sources of sediment-associated metals.     

在法国前铅和锌冶炼厂附近的城市土壤重金属的污染、分离和利用

smelters in Northern France were studied by analysing the chemical forms of these metals and evaluating their phytoavailability. These metals were determined using flame or electrothermal absorption atomic spectrometry （FAAS or ETAAS）, depending on their concentration levels. After optimisation of the ETAAS method, characteristic mass of In in water and aqua regia were 9.9 and 18 pg, respectively, showing the high sensitivity of the analytical Soil contamination by metals from anthropogenic activities （e.g., mining and smelting） is a major concern for the environment and human health. Environmental availability of cadmium （Cd）, lead （Pb）, zinc （Zn）, copper （Cu）, and indium （In） in 27 urban soils located around two former Pb and Zn smelters in Northern France were studied by analysing the chemical forms of these metals and evaluating their phytoavailability. These metals were determined using flame or electrothermal absorption atomic spectrometry （FAAS or ETAAS）, depending on their concentration levels. After optimisation of the ETAAS method, characteristic mass of In in water and aqua regia were 9.9 and 18 pg, respectively, showing the high sensitivity of the analytical procedure. Metal partitioning was conducted using a four-step sequential extraction procedure. The results showed that Cd and Zn were mainly in the acid-extractable and reducible forms in the urban soils studied. In contrast, Pb and In were largely in the reducible fraction. However, in some samples, the amount of In extracted in the residual or exchangeable fraction was higher than that in the reducible fraction. Copper was mainly found in the reducible and residual fractions. A pot experiment was conducted in a glasshouse with seven soils （six contaminated and one uncontaminated） and two plant species, ryegrass and lettuce. The results showed transfer of metals from the contaminated soils to the shoots of ryegrass and the edible part of lettuce. The metal bioconcentration factor was in the order of Cd Cu > In > Zn Pb for lettuce leaves, whereas for ryegrass shoots, three orders were found, Cd > Zn > Cu In > Pb, Cd ≥ In > Zn > Cu Pb, and Zn > Cd > Cu > In > Pb, depending on the physico-chemical properties of the soils, such as pH, cation exchange capacity, carbonates, and organic matter. It was established that the metal toxicity was related to the contamination levels and the physico-chemical properties, including pH, organic matter, and in a lesser extent, Ca, Mg, and phosphorus contents, of the soils. However, it was shown that lettuce could grow on soils having high Cd and CaCO₃ contents. Cadmium was one of the most available metals while Pb was always the least available in the soils studied.     

The Historical Record of Metals in Sediments from Six Lakes in the Fraser River Basin,British Columbia

Sediment cores were collected from six lakes (Moose, Stuart, Chilko, Kamloops, Nicola and Harrison Lakes) distributed throughout the Fraser River Basin, British Columbia. The cores were dated primarily from ²¹⁰Pb profiles and dating was corroborated by counting laminae and by using ¹³⁷Cs as a discrete time marker. The cores were analyzed for a suite of metals (Co, Cr, Cu, Hg, Ni, Mn, Pb and Zn) and organic carbon. The data were evaluated in the context of post-1900 contamination by metals in the Fraser River basin. Overall, lake sediments from the Fraser Basin remain relatively pristine in terms of metal contamination, exhibiting only minor metal enrichments in layers dating from industrial times (post-1900). Stuart Lake, which received Hg contamination from a mine on Pinchi Lake, shows a clear contaminant Hg signal. Pb exhibits ubiquitous contamination in five of the six lakes studied. The Pb enrichments are minor (ranging from 8.4 to 30.9 μg g^-1) and consistent with local automotive emissions from the use of leaded gasoline possibly augmented by long-range transport from industrial and municipal centers along the west coast. The largest Pb fluxes were observed in Kamloops, Moose and Harrison Lakes, each of which has either a highway or a large urban centre as a local source of Pb. This watershed-scale evaluation offers a unique opportunity to compare the relative importance of local and regional sources of contamination.     

去除有机质对城市浅水湖泊氮磷释放特征的影响

[目的] 分析南昌市浅水湖泊象湖表层沉积物的释放特征及有机质对氮、磷释放的影响,为城市内浅水湖泊治理中富营养化控制提供理论依据。[方法] 通过释放动力学试验以及释放潜能试验研究了城市浅水湖泊氨氮（NH₄⁺-N）和溶解性活性磷（SRP）的释放特征,以及与通过H₂O₂去除有机质后的释放特征进行了对比。[结果] 去除前后的氮磷的释放速率都是先由一个较快的过程逐渐变慢最后趋于稳定达到最大释放量（Q_max）。去除有机质后NH₄⁺-N的释放平衡时间缩短,SRP则几乎不变。去除有机质后,NH₄⁺-N的最大释放量（Q_max）与有机质含量呈显著正相关,而SRP与有机质无显著相关性。[结论] 影响沉积物氮磷释放的因素多样,其中高等水生植物丰富的区域对磷的释放有明显的抑制作用。沉积物有机质的含量越高沉积物氮的最大释放量（Q_max）也越高,磷的的最大释放量（Q_max）则受有机质含量、活性、组成成分、吸附与结合的铁铝磷含量等因素共同影响。     

Investigating speciation and toxicity of heavy metals in anoxic marine sediments—a case study from a mariculture bay in Southern China

Purpose

The pollution of marine sediments by heavy metals is still a major concern, especially in zones affected by industry or mariculture. Toxicity of sediment heavy metal contents may be assessed using sequential extraction (SE) procedures, minding inherent constraints of such approaches. In this study, we investigated heavy metal speciation and toxicity in anoxic marine sediments in Zhelin Bay, a mariculture bay in Southern China, using an SE and acid volatile sulfur-simultaneously extracted metals (AVS-SEM) approach.

Materials and methods

Speciation of Cd, Cu, Ni, Pb, and Zn were studied by a modified SE of five fractions, adapted to separate organic and sulfidic metal fractions in anoxic sediments: F1 weak acid soluble (readily available), F2 reducible fraction, F3 organic matter-bound fraction, F4 sulfide-bound fraction, and F5 residually bound fraction. Toxicity predictions based on the sum of non-residual (NR) metal fractions from sequential extraction were compared to predictions based on AVS-SEM.

Results and discussion

Results showed that Cd, Ni, and Pb predominantly occurred in the weak acid soluble fraction (F1), residual fraction (F5), and sulfide-bound fraction (F4), respectively; Cu and Zn were mainly obtained in F4 and F5. Based on the distribution of indicator elements for metal fractions, the SEM from AVS extraction included different yields of non-residual and residual fractions besides the sulfidic fraction. Estimates for potential heavy metal toxicity based on NR metals of the SE procedure were thus based on a better-defined speciation compared to the simplistic approach of the AVS-SEM method.

Conclusions

Based on the contents of NR metals and normalizing them by organic matter content, toxic effects are not expected for any of the sampling sites, irrespective of the presence or absence of mariculture. Using Pearson correlation analysis to identify predominant fractions influencing toxicity, we conclude that toxicity of heavy metals in anoxic sediments can be well predicted by their non-residual heavy metal contents.