Relationships of Heavy Metals in Natural Lake Waters with Physico-chemical Characteristics of Waters and Different Chemical Fractions of Metals in Sediments

The relationships between heavy metal concentrations and physico-chemical properties of natural lake waters and also with chemical fractions of these metals in lake sediments were investigated in seven natural lakes of Kumaun region of Uttarakhand Province of India during 2003–2004 and 2004–2005. The concentrations of Cr, Mn, Fe, Ni, Cu, Zn, Cd and Pb in waters of different lakes ranged from 0.29–2.39, 10.3–38.3, 431–1407, 1.0–6.6, 5.3–12.1, 12.6–166.3, 0.7–2.7 and 3.9–27.1 μg l^?1 and in sediments 14.3–21.5, 90.1–197.5, 5,265–6,428, 17.7–45.9, 13.4–32.0, 40.0–149.2, 11.1–14.6 and 88.9–167.4 μg g^?1, respectively. The concentrations of all metals except Fe in waters were found well below the notified toxic limits. The concentrations of Cr, Mn, Ni, Cu, Zn, Cd and Pb were positively correlated with pH, electrical conductivity, biological oxygen demand, chemical oxygen demand and alkalinity of waters, but negatively correlated with dissolved oxygen. The concentrations of Cr, Ni, Zn, Cd and Pb in waters were positively correlated with water soluble + exchangeable fraction of these metals in lake sediments. The concentrations of Zn, Cd and Pb in waters were positively correlated with carbonate bound fraction of these metals in lake sediments. Except for Ni, Zn and Cd, the concentrations of rest of the heavy metals in waters were positively correlated with organically bound fraction of these metals in lake sediments. The concentrations of Cr, Mn, Ni, Cu and Zn in waters were positively correlated with reducible fraction of these metals in lake sediments. Except for Cd, the concentrations of rest of the metals in waters were positively correlated with residual fraction and total content of these heavy metals in lake sediments.     

闽江大樟溪下游沿线湿地沉积物中重金属

基于2018年7月采集的大樟溪下游沿线湿地表层沉积物样品,探讨了6种重金属(Pb、Cr、Cu、Zn、Ni、Cd)的沿程分布特征,并运用地累积指数法(Igeo)和潜在生态风险指数法(RI)对其生态风险进行了评估。结果表明,湿地沉积物中重金属的平均含量整体表现为Zn>Pb>Cr>Cu>Ni>Cd,且其沿程变化较为一致,而这主要取决于沉积物粒度组成、磁学参数、pH、EC和有机质的沿程分布。湿地沉积物中的6种重金属含量均于桃花洲、耕櫵亭、方庄村和奥莱时代出现较低值,原因主要与4个采样点的采砂活动改变了河流水沙条件使得沉积物发生粗化有关。湿地沉积物中6种重金属之间均存在极显著正相关关系(P<0.01),说明其具有同源性,并可能代表了一个因采砂/采石活动以及建筑/生活垃圾堆放导致的复合污染源。大樟溪下游沿线湿地大部分样点的Pb处于轻度污染状态,而Cd处于中度污染状态。6种重金属平均单项潜在生态风险指数(E■)表现为Cd>Pb>Ni>Cu>Cr>Zn,Cd具有强生态风险。所有样点重金属的平均RI值为228.62,说明湿地整体处于中等生态风险。研究发现,尽管大樟溪下游沿线湿地沉积物中的重金属含量相比闽江上游其它支流和闽江中下游河段处于一个较低水平,但其Pb、Cd污染及生态风险(特别是Cd)仍较为突出,故下一步在加强对沿线湿地管控时应给予特别重视。     

Extractability and plant uptake of heavy metals in alum shale soils

Abstract

Fifty soil samples (0–20 cm) with corresponding numbers of grain, potatoes, cabbage, and cauliflower crops were collected from soils developed on alum shale materials in Southeastern Norway to investigate the availability of [cadmium (Cd), copper (Cu), zinc (Zn), lead (Pb), nickel (Ni), and manganese (Mn)] in the soil and the uptake of the metals by these crops. Both total (aqua regia soluble) and extractable [ammonium nitrate (NH₄NO₃) and DTPA] concentrations of metals in the soils were studied. The total concentration of all the heavy metals in the soils were higher compared to other soils found in this region. Forty‐four percent of the soil samples had higher Cd concentration than the limit for application of sewage sludge, whereas the corresponding values for Ni, Cu, and Zn were 60%, 38%, and 16%, respectively. About 70% the soil samples had a too high concentration of one or more of the heavy metals in relation to the limit for application of sewage sludge. Cadmium was the most soluble of the heavy metals, implying that it is more bioavailable than the other non‐essential metals, Pb and Ni. The total (aqua regia soluble) concentrations of Cd, Cu, Zn, and Ni and the concentrations of DTPA‐extractable Cd and Ni were significantly higher in the loam soils than in the sandy loam soils. The amount of NH₄NCyextractable metals did not differ between the texture classes. The concentrations of DTPA‐extractable metals were positively and significantly correlated with the total concentrations of the same metals. Ammonium nitrate‐extractable metals, on the other hand, were not related to their total concentrations, but they were negatively and significantly correlated to soil pH. The average concentration of Cd (0.1 mg kg^‐1 d.w.) in the plants was relatively high compared to the concentration previously found in plants grown on the other soils. The concentrations of the other heavy metals Cu, Zn, Mn, Ni, and Pb in the plants were considered to be within the normal range, except for some samples with relatively high concentrations of Ni and Mn (0–11.1 and 3.5 to 167 mg kg‘¹ d.w., respectively). The concentrations of Cd, Cu, Zn, Ni, and Mn in grain were positively correlated to the concentrations of these respective metals in the soil extracted by NH₄NO₃. The plant concentrations were negatively correlated to pH. The DTPA‐extractable levels were not correlated with plant concentration and hence DTPA would not be a good extractant for determining plant availability in these soils.     

Heavy Metals in Freshly Deposited Stream Sediments of Rivers Associated with Urbanisation of the Ganga Plain,India

Freshly deposited stream sediments from six urban centres of the Ganga Plain were collected and analysed for heavy metals to obtain a general scenery of sediment quality. The concentrations of heavy metals varied within a wide range for Cr (115–817), Mn (440–1 750), Fe (28 700–61 100), Co (11.7–29.0), Ni (35–538), Cu (33–1 204), Zn (90–1 974), Pb (14–856) and Cd (0.14–114.8) in mg kg^-1. Metal enrichment factors for the stream sediments were <1.5 for Mn, Fe and Co; 1.5–4.1 for Cr, Ni, Cu, Zn and Pb; and 34 for Cd. The anthropogenic source in metals concentrations contributes to 59% Cr, 49% Cu, 52% Zn, 51% Pb and 77% Cd. High positive correlation between concentrations of Cr/Ni, Cr/Cu, Cr/Zn, Ni/Zn, Ni/Cu, Cu/Zn, Cu/Cd, Cu/Pb, Fe/Co, Mn/Co, Zn/Cd, Zn/Pb and Cd/Pb indicate either their common urban origin or their common sink in the stream sediments. The binding capacity of selected metals to sediment carbon and sulphur decreases in order of Zn > Cu > Cr > Ni and Cu > Zn > Cr > Ni, respectively. Stream sediments from Lucknow, Kanpur, Delhi and Agra urban centres have been classified by the proposed Sediment Pollution Index as highly polluted to dangerous sediments. Heavy metal analysis in the <20-μm-fraction of stream sediments appears to be an adequate method for the environmental assessment of urbanisation activities on alluvial rivers. The present study reveals that urban centres act as sources of Cr, Ni, Cu, Zn, Pb and Cd and cause metallic sediment pollution in rivers of the Ganga Plain.     

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.     

Bioaccessibility of Trace Metals in Sediment, Macroalga and Antifouling Paint to the Wild Mute Swan, Cygnus olor

The bioaccessibilities of trace metals (Cd, Cr, Cu, Ni, Pb, Zn) in eelgrass, sediment and preparations thereof with and without antifouling paint particles have been assessed by undertaken a physiologically based extraction test (W-PBET) designed to mimic the chemistry of the gizzard and intestine of the mute swan, Cygnus olor. Because Cu- and Zn-based pigments are employed in contemporary antifouling paints, concentrations of these metals were greatest in the preparations containing paint particles. Moreover, relative to total metal, both Cu and Zn displayed the highest gizzard bioaccessibilities in these preparations (about 10%). In the intestine, where most nutrients are absorbed, the accessibility of Cu was maintained while that of Zn was dramatically reduced. These observations were qualitatively consistent with metal concentrations measured in source materials relative to those in swan faeces. We conclude that Cu poses the greatest threat to C. olor inhabiting coastal areas where boat repair takes place.     

抚仙湖重金属污染强度、历史及来源的沉积记录

This study focused on the concentration change of heavy metals of sediment cores in heavily polluted north area and less polluted middle area of Fuxian Lake in Southwest China.On the basis of the analysis of Cu,Ni,Ti,V,Pb,Cd,and Zn concentration-depth profiles,the pollution history of heavy metals was studied using ¹³⁷cesium (¹³⁷Cs) dating.The sources of heavy metals were distinguished by normalization of their profiles to aluminum and analysis of heavy metal concentrations of potential source materials.Geoaccumulation index (I_geo) was used to quantify their contamination intensity.The results showed that all the heavy metals found in the Fuxian Lake sediments originated naturally before 1980s.Cu,Ni,Ti,and V were still mainly natural in the north lake after 1980s,Cu,Ni,Ti,V,and Pb were mainly natural in the middle lake at all time,but the concentrations of Pb and Zn in the north lake were influenced by industrial wastes from the phosphorus fertilizer factory and cement plants.In all the lake,the contaminations of Cd and Zn were the results of agricultural cultivation using a large amount of fertilizers and the atmospheric fallouts of dusts from cement plants.At present,the geoaccumulation indices showed that the Fuxian Lake sediments were moderately to strongly polluted by Cd in the middle lake,and unpolluted to moderately polluted by Pb and Zn and strongly polluted by Cd in the north lake.Moreover,the pollution intensities of Cd,Zn,and Pb have been increased since 1980s.     

府河-白洋淀沉积物中重金属污染特征及潜在风险评价

沉积物重金属污染是水环境污染评价的重要内容,重金属含量水平常被作为水环境质量的重要指标之一。为了掌握华北平原的府河和白洋淀中沉积物重金属的污染水平,研究了19个沉积物样品和3个土壤样品中7种重金属的污染特征,利用地积累指数法、潜在生态危害指数法及生物效应浓度法评估了重金属的环境风险,并初步分析了污染来源。结果表明,府河和白洋淀沉积物受多种重金属复合污染,其中Zn、Pb、Cu和Cd污染较为严重,府河沉积物的潜在生态环境危害强于白洋淀。相关分析显示府河和白洋淀重金属污染具有相似污染源,保定市工业废水、生活污水及府河沿岸金属冶炼企业很可能是白洋淀地区重金属的主要来源。从城市环境管理、生态环境修复、宣传教育等方面提出白洋淀区域重金属污染控制对策与建议,为白洋淀区域生态环境保护提供科技支撑。     

Distribution of heavy metals in soils of the Yellow River Delta: concentrations in different soil horizons and source identification

Purpose

The Yellow River Delta, an active land-ocean interaction area, will develop into a large eco-economic region in East China during the coming decade. It is necessary to assess the geochemical features of heavy metals in the soils. The objectives of this research were to evaluate the concentrations and distribution of heavy metals (Cr, Ni, Cu, Zn, Pb, and Cd) in soil profiles of the area and to identify their sources.

Materials and methods

Horizon samples were collected based on pedogenic features from bottom to top in each profile to a depth of 120 cm and a total of 92 samples were collected. The sampling sites were grouped into four lines from inland to coastal area with three land use types (cotton field, cereal field, and wetland). The concentrations of Cr, Ni, Cu, Zn, Pb, and Cd were measured by inductively coupled plasma-mass spectrometry. Iron oxide fractions in the soil were extracted by oxalate-oxalic acid and dithionite-citrate-bicarbonate. X-ray diffraction (XRD) was used to determine the mineral composition of the soils. Multivariate statistical analysis and historical data were employed to identify the possible sources of these heavy metals.

Results and discussion

The mean concentrations of heavy metals were elevated along the Yellow River region and in the southern part of the delta; however, they were generally lower than the Chinese guideline values. As for the depth distribution of heavy metals in soil profiles, the maximum values of Cr, Ni, Cu, Zn, and Cd in middle horizon of cotton field were almost twice than those in surface horizon. The iron oxides and XRD analysis indicated that the trace elements accumulation appeared to be related with the contents of crystalline iron oxide and layer silicates. Historical data from suspended sediments of the Yellow River and principal component analysis (PCA) implied that most of the metals (Cr, Ni, Cu, and Zn) were sourced from natural alluviation and sedimentation.

Conclusions

The Yellow River Delta soils were slightly polluted by heavy metals the Yellow River Delta. The special pedogenic horizon characterized by higher iron oxides and layered silicates minerals in the middle and lower part of the soil profile was found with heavy metals enrichment, which required to be studied further. Suspended sediments transported by the Yellow River were suggested to be one of the major sources for the heavy metals accumulation in the basal soils of this region.     

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.     

Gastropod Assemblages as Indicators of Sediment Metal Contamination in Mangroves of Dumai, Sumatra, Indonesia

Impacts of heavy metal concentrations in sediments on the gastropod community structure were assessed in the coastal waters of Dumai, Sumatra, Indonesia. The objective of this study was to relate the levels of heavy metal pollution with the changes of gastropod community structure in the study area. Concentrations of Cd, Cu, Pb, Zn, Ni, and Fe in surface sediments collected from five sampling stations were analyzed and correlated with the abundance, species richness, and diversity of gastropod populations. Sediments at stations with more anthropogenic activities accumulated higher concentrations of heavy metals and consequently displayed lower abundances, lower species richness and diversity; while stations with lower heavy metal concentrations in sediments showed the opposite pattern in gastropod community metrics. The above findings are complemented by significant negative correlations p?<?0.05–0.01) between concentrations of Cd, Cu, Pb, Zn, and Ni in the sediments and gastropod abundance and species richness. Among the metals analyzed, Cu and Zn had strongest negative correlations with the gastropod diversity which suggests that these metals may be the most detrimental to gastropod populations in the mangrove area of Dumai coastal waters.     

Distribution,risk assessment,and source analysis of heavy metals in sediment of rivers located in the hilly area of southern China

Purpose

River sediment, the important sink and source of heavy metals, can provide critical information for aquatic ecosystem health. Heavy metal pollution has been a serious problem facing river systems worldwide and can adversely affect human beings via the food chain. However, no comprehensive study has been conducted on heavy metal pollution in sediments of river systems in the hilly area of southern China, which plays a key role in water supply and ecosystem balance. This study is aimed at comprehensively studying the pollution status of heavy metals in river sediments in the hilly area of southern China and apportioning sources.

Materials and methods

A total of 39 superficial sediment samples were collected from the upstream, midstream, and downstream of 13 rivers (Xiangjiang River, Zishui River, Yuanjiang River, and Lishui River located in Hunan Province; Ganjiang River, Xinjiang River, Fuhe River, Raohe River), and Xiushui River located in Jiangxi Province; Qiantangjiang River and Oujiang River located in Zhejiang Province; Minjiang River and Jiulongjiang River located in Fujian Province) in the hilly area of southern China. The total concentrations of metals of Mn, Zn, Cr, Co, Ni, Cu, As, Cd, Sb, Pb, and V were analyzed using the inductively coupled plasma-mass spectrometry method. The pollution status and potential ecological risk were assessed with the geoaccumulation index (I_geo), sediment quality guidelines (SQGs), and potential ecological risk index (RI). The source apportionment of heavy metals was performed by correlation analysis and principle component analysis (PCA).

Results and discussion

Results indicated that Mn, Zn, and Pb concentrations were significantly higher than other metals, especially in the upstream of the Jiulong River and midstream and downstream of the Xiangjiang River. Pollution assessment indicated that Cd pollution of sediments was most serious and that more than 50% of sampling sites were significantly polluted, with a very high potential ecological risk. The rivers in Hunan provinces (HN) were identified as the priority controlled rivers because of the high I_geo and RI index values. Correlation and PCA analysis indicated that Mn, Pb, and Zn originated from natural and mineral exploitation activities; As, V, Ni, and Sb originated from industrial wastewater and mineral-smelting activities; Cu and Co originated from agricultural activities; Cr and Ni originated from natural sources. While the most polluted Cd came from a combination of multiple sources described above.

Conclusions

Results indicated that Cd was the most common heavy metal pollutant, especially in river sediments of Hunan Province. Anthropogenic activities have become the main source of heavy metals in the river sediments of the hilly area of southern China. Special attention should be paid to Cd, and measures must be taken to prevent from further anthropogenic influence on heavy metal pollution.

     

Bioaccumulation of heavy metals by Cyperus malaccensis and Spartina alterniflora in a typical subtropical estuary (Min River) of Southeast China

Purpose

To understand the bioaccumulation of heavy metals by Cyperus malaccensis (CM) and Spartina alterniflora (SA) in a typical subtropical estuary (Min River) of Southeast China, the concentrations of five metals (Pb, Cr, Cu, Zn, and Ni) in plants and sediments of CM and SA marshes were determined.

Materials and methods

Two experimental plots (no flooding plot and flooding plot) were established in the intertidal zone of the Min River estuary in July 2015, and, in each plot, in situ sampling was conducted in CM and SA marshes, respectively. The concentrations of heavy metals in all samples were determined by inductively coupled plasma mass spectrometry (ICP-MS) analysis.

Results and discussion

Vertical variations of the five metals differed between marshes or plots, and, in most cases, there was no evidence of grain-size composition (particularly for clay) and sediment organic matter (SOM) contributing to the sorption of significant amounts of metals in sediments of different marshes. Flooding regime was an important factor inducing the difference of metals in sediments of the two experimental plots. Heavy metal levels in different tissues of CM and SA differed within species or plots. For the five metals, the root was generally the main stock, and, as water condition changed from non-flooding to flooding, allocations of Pb, Cu, and Zn in CM and SA decreased while those of Cr increased. The accumulation factors [AF_s] of heavy metals in different tissues of CM and SA also differed between species or plots. In most cases, the [AF]_plant of different metals were less than 1, implying that the metal accumulations in CM and SA of the two plots were uncommon.

Conclusions

This study found that Cu and Zn pollution in non-flooding conditions and Pb and Cu pollution in flooding conditions might be more serious, indicating that intertidal sediments might be severely contaminated by the three metals if effective measures are not taken to control the pollutant loadings of the Min River estuary in the future. Moreover, CM generally accumulated more Pb, Cu, and Zn while SA absorbed more Cr and Ni (particularly in flooding conditions), implying that, when determining environmental pressures, the two plants could be used as specified biological indicators.

     

Influence of pH on the release and chemical fractionation of heavy metals in sediment from a suburban drainage stream in an arid mine-based oasis

Purpose

The objectives of this study were to explore the influences of pH on the release of Cu, Zn, Cd, Pb, Ni, and Cr in sediments derived from the upstream, middle, and downstream reaches of Dongdagou stream in Gansu Province, Northwest China, and to examine the fractionation changes of heavy metals in the sediments after reaching their release equilibrium under different pH conditions.

Materials and methods

Sediment samples were obtained using a stainless steel grab sampler to collect the uppermost 10 cm of sediment from the channel bed. The pH-dependent release experiment was conducted in the solid-to-liquid ratio of 1:20 at different pH values (2, 4, 6, 8, 10, and 12) at room temperature. The total Cu, Zn, Cd, Pb, Ni, and Cr concentrations in the sediments were digested using an acid digestion mixture (HNO₃ + HF + HClO₄) in an open system. Metal fractionation of selected sediments was obtained using the Tessier sequential extraction procedure. Heavy metal concentrations in the samples were determined using atomic absorption spectrophotometry.

Results and discussion

The mean concentrations of heavy metals in sediments decreased in the following order: Zn (1676.67 mg kg^?1) > Pb (528.65 mg kg^?1) > Cu (391.34 mg kg^?1) > Cr (53.48 mg kg^?1) > Ni (34.27 mg kg^?1) > Cd (11.53 mg kg^?1). Overall, the solubility of Cu, Zn, Cd, Pb, and Ni decreased with increasing pH, and they were strongly released at pH 2. Moreover, the solubility of Cr increased with increasing pH, and its release was highest at pH 12. After reaching the release equilibrium of heavy metals under different pH conditions, the percentages of organic Cu, Zn, Cd, and Fe-Mn oxyhydroxide Pb decreased, compared to their initial fractions. The residual fractions of Ni and Cr were dominant, regardless of pH.

Conclusions

The average concentrations of Cu, Zn, Cd, and Pb in sediments were highly elevated compared with the soil background values in Gansu Province, China. The results of this pH-dependent release experiment showed that the release behaviors of Cu, Zn, Pb, and Cr followed an asymmetric V-shaped pattern, whereas Cd and Ni followed an irregular L-shaped pattern. The changes in the release of heavy metals in sediments were related to their redistribution between chemical fractionations.

     

汉江上游汉中段河流表层沉积物重金属污染风险评价

通过监测汉江上游汉中段河流表层沉积物重金属Pb,Cu,Zn,Cd,Cr的浓度,分析了各元素的含量分布特征,并选用Hakanson生态风险指数法对研究区进行了环境风险评价。结果表明,汉江上游汉中段各监测点重金属富集顺序为:Cd >Zn >Pb >Cr >Cu。单个重金属的污染指数C_fⁱ显示,汉江上游汉中段监测点仅有Cu的含量均值为0.83,小于1,为轻微污染;Pb,Zn,Cd,Cr的均值分别为1.06,1.25,1.33,1.02,略大于等于1,处于轻微污染以上水平,达到中度污染水平。综合分析多项重金属污染系数C_d,单项重金属的潜在生态风险系数E_rⁱ和多种重金属的生态系统的潜在生态风险指数I_R可知,汉江上游汉中段各监测点沉积物重金属污染属于轻微生态危害。     

Soil Contamination in Dumps on the Karstic Areas from the Plateaus (Southeast of Madrid, Spain)

After over 10 years of accumulation of residues in the studied dumps near Madrid, it has been registered low or moderate heavy metals concentrations on the surrounding area. Only occasionally, some rubbish dumps contain significant quantities of Cu, Ni, Zn and Pb. The concentration levels of Pb, Ni, Zn and Cu are safe when they are compared with the surrounding areas levels of heavy metals. The aim of this paper is the analysis of pollutants existing around in the dumps located at the sides of the plateaus of the central valley of the Tajo River (provinces of Madrid and Toledo, Spain). The high karstification rate of the upper layer of these tablelands and the existence of numerous dumps on them (even on their slopes) make these areas vulnerable to heavy metal pollution. However, after several years of use, the concentration of pollutants only reaches moderate values in the studied areas. Dumping materials were collected at four rubbish dumps. The mineralogical composition of the materials were analysed by XRD. Sequential extraction procedure was applied for speciation of the metal forms in the collected samples. Concentrations of Zn, Pb, Ni, Cu, Cr and Cd in extracts were determined by AAS. The studied samples showed high carbonate concentration. Contamination processes are combined there with weathering processes. Heavy metals concentration in control samples (gypsum, limestones, red soils and colluviums) were compared with samples of the studied dump in order to evaluate the pollution level. Concentrations of Zn, Pb, Ni and Cu were variable. The contamination was elevated for samples in depth in relation with weathering process of heavy metals.     

Distribution, Seasonal Variations and Ecotoxicological Significance of Heavy Metals in Sediments of Cross River Estuary Mangrove Swamp

The concentrations and distribution of selected heavy metals in epipelic and benthic sediments of Cross River Estuary mangrove swamp were studied to determine the extent of anthropogenic inputs from industrial activities and to estimate the effects of seasonal variations on geochemical processes in this tropical estuarine ecosystem. The analysis shows that the mean concentrations (mg/kg, dw) of Cu, Cr, Fe, Ni, Pb, V and Zn vary from 24.1–32.4, 19.9–27.4, 666.7–943.5, 15.2–30.3, 8.8–24.7, 2.2–6.9 and 140.1–188.9, respectively. An important observation is that, in general, lowest metal concentrations are found during the dry season, compared to wet season. Pollution load index (PLI) and index of geoaccumulation (I _geo) revealed overall low values but the enrichment factors (EFs) for Cr, Zn, and V were high, and this reflects the intensity of anthropogenic inputs related to industrial discharge into the estuary. The mean concentrations of Zn, Cu and to some extent Ni exceeded the Effects Range—Low (ERL) and Threshold Effect Level (TEL) values in majority of the samples studied, indicating that there may be some ecotoxicological risk to organisms living in these sediments. The inter-element relationship revealed the identical source of elements in the sediments of the studied area. The concentration of heavy metals reported in this work will be useful as baselines for comparison in future sediment quality studies.     

巢湖表层沉积物中重金属污染的时空变化特征及潜在生态风险评价

2008年3月至7月连续对巢湖8个采样点的表层沉积物中Zn、Hg、Cr、Pb、Ni和Cu6种重金属含量进行分析,据此探讨巢湖表层沉积物中重金属污染程度及时空分布特征,评价巢湖重金属污染的潜在生态风险并筛选出主要生态风险因子。结果表明：3月至7月期间,全湖范围内表层沉积物中重金属含量逐渐降低,河流入湖区的污染程度高于其他区域,Zn、Cu、Pb的污染程度高于其他重金属,表层12cm沉积物中的重金属含量随深度增加污染情况呈加重趋势;从潜在生态风险角度分析,巢湖表层沉积物总体只具有轻微潜在生态风险,生态风险指数排名前两位的区域是南淝河入湖区和十五里河入湖区,3月至7月期间重金属潜在生态风险级别逐渐降低,巢湖生态安全主要风险因子为Hg,其次是Pb和Cu。     

Transport and distribution of heavy metals in Cauvery river

Heavy metal transport in Cauvery river chiefly takes place in the particulate form. Tributaries Hemevathi and Kabini draining highly mineralized areas contribute significantly to the heavy metal load of the Cauvery river. Particulate metal transport is influenced by the presence of major dams built across the river. Factor analysis of the elemental data identifies two major group of heavy metals, (a) Fe, Mn, Cr, V and Ti and (b) Cu, Pb and Zn in the suspended sediments of Cauvery river. Heavy metals in surface sediments show wide variations in their concentrations due to the non-uniform grain size distribution of the sediments. The elements Fe, Mn, Pb, Cu, Zn, Ni, Co and As are dominantly present in the <20 μm fraction of the river sediments. Speciation studies show that Fe-Mn oxide phase held the largest share of heavy metals in the sediments. The depth variation of heavy metals in the core sediments suggest their similar mobility during diagenesis. Geoaccumulation indices calculated suggest that Cd, Zn, Cr, Pb, Cu and Ni are enriched in sediments several times over background values.     

Heavy‐Metal Contamination of Soil and Vegetables in Wastewater‐Irrigated Agricultural Soil in a Suburban Area of Hanoi,Vietnam

The To Lich and Kim Nguu Rivers, laden with untreated waste from industrial sources, serve as sources of water for irrigating vegetable farms. The purposes of this study were to identify the impact of wastewater irrigation on the level of heavy metals in the soils and vegetables and to predict their potential mobility and bioavailability. Soil samples were collected from different distances from the canal. The average concentrations of the heavy metals in the soil were in the order zinc (Zn; 204 mg kg^?1) > copper (Cu; 196 mg kg^?1) > chromium (Cr; 175 mg kg^?1) > lead (Pb; 131 mg kg^?1) > nickel (Ni; 60 mg kg^?1) > cadmium (Cd; 4 mg kg^?1). The concentrations of all heavy metals in the study site were much greater than the background level in that area and exceeded the permissible levels of the Vietnamese standards for Cd, Cu, and Pb. The concentrations of Zn, Ni, and Pb in the surface soil decreased with distance from the canal. The results of selective sequential extraction indicated that dominant fractions were oxide, organic, and residual for Ni, Pb, and Zn; organic and oxide for Cr; oxide for Cd; and organic for Cu. Leaching tests for water and acid indicated that the ratio of leached metal concentration to total metal concentration in the soil decreased in the order of Cd > Ni > Cr > Pb > Cu > Zn and in the order of Cd > Ni > Cr > Zn > Cu > Pb for the ethylenediaminetetraaceitc acid (EDTA) treatment. The EDTA treatment gave greater leachability than other treatments for most metal types. By leaching with water and acid, all heavy metals were fully released from the exchangeable fraction, and some heavy metals were fully released from carbonate and oxide fractions. The concentrations of Cd, Cr, Cu, Ni, Pb, and Zn in the vegetables exceeded the Vietnamese standards. The transfer coefficients for the metals were in the order of Zn > Ni > Cu > Cd = Cr > Pb.