Distribution,speciation, and ecological risk assessment of heavy metals in surface sediments of Jiaozhou Bay,China

This paper analyzed the distribution and speciation of seven heavy metals in sediments in Jiaozhou Bay. The ecological risk was assessed using three index approaches (i.e., risk assessment code (RAC), contamination factor (CF), and potential ecological risk index (PERI)) and by a comparison with sediment quality guidelines (Chinese Marine Sediment Quality Standards (CMSQS), and threshold effect level (TEL) and probable effect level (PEL) from the USEPA). Pb, Cr, As, Cu, Zn, and Hg contents at most sites were above the corresponding TEL and Class I criteria (CMSQS) value. Particularly, high contents of Cu, detected at sites S₇ (124.5 mg kg^?1) and S₈ (118.3 mg kg^?1), exceeded the respective PEL value, indicating that harmful biological effects might occur. Speciation analysis, individual CF, and RAC calculations suggested that Cd had the highest bioavailable fraction and thus posed a very high risk to aquatic ecosystem; Cu and Zn showed a medium–high risk. Both global CF and PERI analysis indicated a high pollution risk at sites S₇, S₁, S₃, and S₂, but the assessments of specific sites were different. The incomplete consistency suggested that it is necessary to consider both total contents and chemical speciation for providing a more realistic appraisal for the risk of heavy metals in sediments.     

Distribution of heavy metals in surface sediments of the Bacochibampo Bay,Sonora, Mexico

Abstract

The aim of this study was to determine the levels of heavy metals (Al, Cd, Cr, Cu, Fe, Mn and Pb) in the geochemical fractions of the coastal surface sediments from the Bacochibampo Bay in Sonora, Mexico. Two surveys were conducted (March and September) during 2004, at eight sampling stations inside the bay, and in three natural effluents discharged into this bay. The extraction of metals was carried out using a microwave oven method and the quantification was done by atomic absorption spectro-photometry. The highest detected concentration of total heavy metals in sediments was: Fe>Al>Mn>Pb>Cr>Cu>Cd, with the following concentration values: Fe (1.72%), Al (1.03%), Mn (416.31 mg kg^?1), Pb (11.73 mg kg^?1), Cr (11.41 mg kg^–1), Cu (6.78 mg kg^–1) and Cd (1.33 mg kg^–1). The levels of total heavy metals (Al, Cr, Cu, Fe, Mn and Pb) were much less than the lowest observable effect level (LEL) which indicates that the sediments were not from polluted areas and that the origin of the metals was due to natural conditions. However, concentrations of Cd were much higher than the low effect level (LEL), over 40% of metal was detected in the exchangeable fraction and carbonates. The normalisation study showed a high degree of enrichment of Cd in all the sampling stations in the Bacochibampo Bay (samples EF 34–87) and in the natural flows that discharge into this bay (samples EF 22–35%), which exceeds by several orders of magnitude the value of sample EF 1, which indicates that Cd is anthropogenically induced. Based on these results, it is important that precautionary measures are established, since the deposited Cd in these fractions may be potentially toxic, due to the physicochemical changes that occur in the environment. Thus, future studies will focus on identifying problems involved with Cd bioaccumulation in different trophic levels.     

Pollution characteristics and ecological risk assessment of heavy metals in the surface sediments from a source water reservoir

Surface sediment samples were collected from a source water reservoir in Zhejiang Province, East of China to investigate pollution characteristics and potential ecological risk of heavy metals. The BCR sequential extraction method was used to determine the four chemical fractions of heavy metals such as acid soluble, easily reducible, easily oxidizable and residual fractions. The heavy metals pollution and potential ecological risk were evaluated systematically using geoaccumulation index (I_geo) and Hakanson potential ecological risk index (H′). The results showed that the sampling sites from the estuaries of tributary flowing through downtowns and heavy industrial parks showed significantly (p < 0.05) higher average concentrations of heavy metals in the surface sediments, as compared to the other sampling sites. Chemical fractionation showed that Mn existed mainly in acid extractable fraction, Cu and Pb were mainly in reducible fraction, and As existed mainly in residual fraction in the surface sediments despite sampling sites. The sampling sites from the estuary of tributary flowing through downtown showed significantly (p < 0.05) higher proportions of acid extractable and reducible fractions than the other sampling sites, which would pose a potential toxic risk to aquatic organisms as well as a potential threat to drinking water safety. As, Pb, Ni and Cu were at relatively high potential ecological risk with high I_geo values for some sampling locations. Hakanson potential ecological risk index (H′) showed the surface sediments from the tributary estuaries with high population density and rapid industrial development showed significantly (p < 0.05) higher heavy metal pollution levels and potential ecological risk in the surface sediments, as compared to the other sampling sites.     

Evaluation of trace metals in sediment,water, and fish (Mugil cephalus) of the central Black Sea coast of Turkey

In this study, concentrations of trace metals such as As, Cd, Cu, Cr, Fe, Pb, Ni, Sn, Se, and Zn were determined in sediments, water, and a kind of fish (Mugil cephalus) of the central Black Sea coasts by employing Inductively Coupled Plasma Mass Spectrometry and microwave digestion technique. Gill, muscle, liver, and other tissues were analyzed separately for each sample. The accuracy of the results were checked by using a certified reference material (DORM-4). In water samples, the metal determined at highest concentrations was Cu (1645.44 µg/L). In sediment samples, the metal determined at highest concentrations was Fe (12223.50 mg/kg). The levels of trace metals found in the different parts of the fish were: Zn in muscle tissue (30393.28 mg/kg), Sn in gill tissue (5140.08 mg/kg), and Cu in liver tissue (289.31 mg/kg). These results were also compared with various relevant guidelines and literature.     

Distribution and risk assessment of heavy metals in river surface sediments of middle reach of Xijiang River basin,China

Xijiang River is the main surface water source in Guangxi province, South China. This study was carried out to investigate the distribution and potential ecological risks of seven heavy metals (Cu, Pb, Zn, As, Cd, Ni, and Cr) in surface sediments in Xijiang River basin. The results illustrated that the average concentrations of Zn, Pb, Cd, Cu, As, Ni, and Cr were 483.9, 207.5, 13.35, 23.50, 312.1, 28.75, and 50.62 mg/kg, respectively. Among them, Zn, Pb, Cd, and As were the major heave metals with concentration exceeding Class 3 threshold value of Chinese national standard. The result also showed samples with high ecological risk were mainly located in the upstream of Xijiang River basin as Diaojiang River, Hongshui River, Jincheng River, and Dahuan River. Based on the pollution risk assessment, the area manifested composite pollution of heavy metals in the sediments, signifying As, Pb, and Cd as the dominant heavy metals, and there were high ecological risk in sediments for these metals. According to correlation matrix and factor analysis (FA), the seven heavy metals were divided into three types/classes, Cd, as and Zn attributed by anthropogenic sources, natural sources corresponds for Ni and Cr while both natural and anthropogenic sources were attributed to Cu.     

Distribution of organochlorines and ecological risks in surface sediments from El-Mex Bay,Mediterranean Sea

Polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) were determined in eight sampling sites collected from El-Mex Bay sediments during the period of 2013–2015. Concentrations of PCBs, Hexachlorocyclohexanes (HCHs), Dichloro Diphenyl Trichloroethanes (DDTs), and cyclodienes ranged from 0.148 to 23.99, ND to 0.089, ND to 4.64, and 0.005 to 0.581 ng g^?1 dry wt, respectively. Total organic carbon (TOC) was relatively low, ranging from 0.09% to 1.42%. Total carbonate content ranged from 38% to 58%. The negative correlation of TOC with total pesticides (r = ?0.18) suggested that TOC does not have a role binding with pesticides. On the other hand, a positive correlation between PCBs and TOC (r = 0.254 at p > 0.01) was observed probably due to the low solubility of PCBs in the seawater. So, it will continue to precipitate until it reaches the bottom water and contaminates the sediment. The data obtained in the present work compared well with the counterpart data reported internationally. In general, the results of PCBs and OCP concentrations in El-Mex Bay sediments were much lower than the permissible levels recorded by sediment quality guidelines (SQGs). Interestingly, the organochlorines in sediments of El-Mex Bay were below the respective SQG values and were not likely to pose potential biological adverse impact.     

Distribution and bioavailability of heavy metals in different particle-size fractions of sediments in Taihu Lake,China

Abstract

Taihu Lake is one of the most important water sources in the economically developed central-eastern part of China, and metal pollution is a major concern for the lake. The distribution and bioavailability of Cd, Cr, Cu, Pb, Sb and Zn were analysed in undifferentiated bottom sediments and in various particle-size fractions of the sediment from different parts of the lake. The average concentration of total metals in undifferentiated sediments ranged from 0.86 mg kg^-1 (Cd) to 95.45 mg kg^-1 (Zn) for the entire lake, with the highest concentrations in Zhushan Bay. The concentration of heavy metals was higher in extremely fine sands (0.064–0.125 mm) and fine sands (0.125–0.25 mm) than in other fractions. Sequential extractions showed that Cu, Zn and Cd were the most bioavailable accounting for 55.6%, 38.7% and 30.0% of their total concentration, respectively. However, the bioavailable proportion of many metals was not significantly different between grain grades except for Cu and Zn, which were higher in silts (<0.064 mm) than in other grades. Compared with the background values of local soils, the concentration of Zn, Cd, Cu, Pb and Sb was higher, indicating enrichment in the sediment. From ecological safety concerns, Zn, Cd and Cu should be examined closely because of their higher bioavailabilty in the sediment.     

湘西河流表层沉积物重金属污染特征及其潜在生态毒性风险

花垣河和峒河是湘西地区受到锰矿和铅锌矿生产影响严重的两条河流。通过表层沉积物采样分析了Cd、Pb、Cu、Ni、Cr、Zn和Mn的总量,根据BCR连续提取程序分析沉积物样品中重金属的地球化学赋存形态,采用内梅罗指数法和地积累指数法评价了沉积物重金属污染特征,根据重金属的富集程度探讨了重金属污染来源,采用淡水生态系统沉积物质量基准(SQGs,TEL/PEL)和毒性单位评价了花垣河和峒河沉积物中重金属元素的生态毒性风险。结果表明,花垣河和峒河绝大多数位点的表层沉积物中Cd、Pb、Cu、Ni、Cr、Zn和Mn的总量高于参照点,形成严重的复合污染,花垣河沉积物中重金属的污染水平明显高于峒河,但沿程变化规律不明显,而峒河沉积物中重金属的沿程变化较有规律,即上游含量低,中下游含量较高。两条河流表层沉积物中富集程度居前列的均为Cd、Pb、Zn和Mn。花垣河和峒河沉积物重金属污染主要来源于矿业生产所产生废渣和废水的点排放。在花垣河和峒河的大多数位点,Cd、Pb和Mn的形态具有共同特征,其生物可利用态均较大程度地超过生物不可利用态,而且Mn和Cd的生物可直接利用态所占比例远高于其它重金属,而Cu和Cr的生物可直接利用态所占比例很低。花垣河沉积物中Cd、Pb和Zn在所有位点极大地超过PEL,在峒河中下游,Cd、Pb、Ni和Zn超过PEL,具有较大的潜在生物毒性。除上游S1位点外,花垣河的其余各位点都具有明显的急性毒性,峒河中下游各位点具有明显的急性毒性,这些河段需要重点治理。     

东海表层沉积硅藻组合与环境关系研究

对东海表层沉积硅藻分析研究,共发现有103种和变种,根据其中分布特征和规律,结合因子负荷变化曲线,把东海表层沉积分为六个硅藻组合和分布区,并探讨影响硅藻分布的环境因素,为恢复古环境提供科学依据。     

Fractionation and ecological risk assessment of trace metals in surface sediment from the Huaihe River,Anhui, China

Abstract

The Huaihe River has suffered increasing pressure from pollutants including metals from anthropogenic activities. In this study, enrichment and fractionation behavior of trace metals were analyzed in sediment samples obtained from fish spawning area of the Huaihe River (Anhui Section) to evaluate the potential ecological risk of trace metals to aquatic organisms. Geochemical indices including enrichment factor and geo-accumulation index as well as mean probable effect concentration quotient and risk assessment code were adopted to assess the contamination degree and potential ecological toxicity. Results showed that the total contents of Cu, Pb, Zn, Cr, Cd, As, and Hg in sediment were 23.1?±?6.4, 32.3?±?11.1, 76.8?±?14.2, 84.6?±?17.2, 0.2?±?0.1, 9.0?±?3.0, and 0.031?±?0.010?mg/kg, respectively. The indexes EF and I_geo revealed slight accumulation for Pb, Zn, Cr, Cd, and As in some sampling sites. The result of Q_m-PEC demonstrated that trace metals in sediment were not toxic to aquatic organisms. Most trace metals appeared to mainly associate with the residual form suggesting lower mobility whereas Cd presented a relative higher exchangeable fraction indicating a great degree of bioavailability. The result of risk assessment code (RAC) evaluation revealed that Cd poses a medium ecological risk for aquatic organisms whereas most of the other trace metals pose low risks.     

Standardization of methods of analysis for heavy metals in sediments

In studies of heavy metals in sediments, there is a need for standardization of the procedures for sample collection and preservation, chemical analyses and presentation of results. The method and depth of sampling depend on the aim of the investigation and on local sediment conditions, such as consistency of the sediment, rate of sedimentation, diagnetic processes and bioturbation. Therefore no general recommendations can be given in this respect. During collection and preservation, contamination and loss of constituents ust be avoided. In sediments, the best means for estimating total contents of metals is digestion with HF, in combination with strong acids. Other methods include X-ray fluorescence and neutron activation analyses. The use of HF is considered objectionable by some laboratories. A reasonable alternative is aqua regia. Because variations in granular composition affect metal contents, it is advisable to use the fraction < 63 μm for the analysis. Chemical partition of sediments provides an insight into the source of metallic constituents, and their pathways to deposition areas. A three-step extraction procedure, in the sequence 0.1 M hydroxylamine-HCl, H₂O₂ 30% and HF, is proposed. Finally, attention is paid to the anthropogenic enrichment of metals in sediments. The establishment of base-line levels is discussed.     

北京市南沙河沉积物重金属污染特征及风险评价

北京南沙河是海淀北部地区的重要排水和风景观赏性河道,为全面了解南沙河底泥沉积物中重金属的污染特征,采集了表层沉积物样品,分析了重金属元素的含量和形态,并利用单因子指数法、Hakanson综合污染指数法和潜在生态风险指数法对沉积物重金属进行了生态风险评价.结果表明:南沙河表层沉积物各种重金属元素存在较好的同源性,污染程度为:Cr＞Cd＞Zn＞Cu＞Pb＞Ni.基于单项潜在生态风险指数的评价表明,该区域重金属生态风险等级由强至弱依次为:Cd＞Pb＞Cu≈Cr＞Ni≈Zn,其中,仅Cd具有较高的潜在生态风险,综合潜在生态风险指数表明,除了京藏高速桥河段危害等级较高外,南沙河总体处于轻微的生态风险等级.形态分析表明,Cd的酸提取态含量高,迁移性最强,最容易对生物造成直接危害,其次是Pb和Zn,Cu和Ni具有一定程度的潜在环境危害,Cr产生环境危害的可能性较小.     

Impact of bioavailable heavy metals on bacterial activities in coastal marine sediments

Total heavy metal concentrations in marine sediments are not sufficient to reliably predict detrimental biological effects. Here we provide evidence that only bioavailable heavy metals have a significant impact on benthic microbial loop functioning. Sediment samples collected along 250 km of the Apulian coast (Mediterranean Sea) were analysed for total and bioavailable heavy metals (Cr, Cd, Pb and Cu), organic matter content, bacterial abundance, biomass and carbon production and -glucosidase activity. Sampling strategy was specifically designed to cover a wide range of environmental conditions and types of anthropogenic influences. Total heavy metal concentrations in the sediments were tightly coupled with organic matter content, whereas bioavailable heavy metal concentrations displayed an opposite pattern. Bioavailable Cr concentrations were up to 10-fold higher than values observed for the other bioavailable metals and significantly inhibited benthic bacterial metabolism and turnover. Results from this study suggest that functional microbial variables are highly sensitive to heavy metal contamination and could be used as bioindicators of stress conditions in coastal sediments.     

Spatial variability characteristics and environmental effects of heavy metals in surface riparian soils and surface sediments of Qinggeda Lake

Abstract

One hundred and twenty topsoil (0–20?cm layer) samples and 45 surface sediment samples were collected from the riparian area and bottom of Qinggeda Lake. The content of Pb, Cu, Cr, Ni, Zn, Mn, V, and As were determined to reveal the distribution characteristics and explore the spatial dependency relationship between environmental factors (pH, conductivity, and organic matter) and heavy metals using Kriging interpolation and the geographical weighted regression model. Results showed as follows: (1) The average contents of Pb, Cu, Cr, Ni, Zn, V, and As did not exceed the Standard of National Soil Environmental Quality. However, Cu, Cr, and V were higher than the Xinjiang soil background. (2) The target elements in the surface sediments of the lake showed a decreasing trend from the center of the lake to the shore. Also, the heavy metal concentrations in the eastern part of the lake shore were significantly higher than those in other areas, and the highest concentrations appeared in the paddy field. (3) The effects of the eight heavy metals on pH, conductivity, and organic matter displayed significant spatial nonstationary characteristics. Cr, As, Cu, and Zn are the primary factors that affect environmental characteristics such as pH, conductivity, and organic matter content.     

Structure and content of pollutants in temporal surface sediments in small watersheds

ABSTRACT

Formation of gel-like surface sediments has been observed during spring and autumn in small watersheds in boreal areas with pH <5.7 and concentrations of humic substances above 3 mg L^?1. This structure efficiently accumulates dissolved, colloidal and particulate constituents. The gel consists of ferric (hydr)oxides and fulvic acid and has high viable counts of bacteria (notably Gallionella spp.) as well as fungal hyphae. The solid/solution distribution (log K_d; l kg^?1) for trace metals (Cd, Cu, Pb, V, Zn) ranges from 4 to 6.5 which indicate an efficient accumulation during periods with gel. The concentrations of adsorbable organic halogens in the gel were not different from forest soils in general.     

Seasonal and spatial variations of heavy metals in surface sediments collected from the Baoxiang River in the Dianchi Watershed,China

To explore potential ecological hazards due to heavy metals in the Dianchi Lake Watershed, a three-stage European Community Bureau of Reference (BCR) sequential extraction procedure was applied to examine the spatial distributions and relative speciation ratios of Zn, Cu, Ni, Pb, and Cr in Baoxiang River sediments during wet and dry seasons. The metal species have similar spatial variations during different seasons. In the upstream reaches of the Baoxiang River, heavy metals reside primarily in the non-extractable residual fraction (72–90%). In the midstream, the residual fraction (35–89%) remains dominant, but the extractable fraction increases, featuring especially notable increases in the reducible fraction (5–40%). Downstream, the Cu, Ni, Pb, and Cr residual fractions remain high (46–80%) and the extractable fractions increase rapidly; the Zn extractable fraction is quite high (65.5%). Anthropogenic sources drive changes in heavy metal speciation. Changes in the river environment, such as pH and oxidation-reduction potential, also affect speciation. The reducible fraction of heavy metals in Baoxiang River sediments is most sensitive to pH. Potential ecological risk assessments for these five elements indicate that risks from Zn and Pb are mild to moderate in the middle and lower reaches of the river.     

青海湖表层沉积物重金属富集特征及其来源

针对青海湖表层沉积物重金属分布特征,测定了湖区11个采样点99个样本表层(0～20 cm)沉积物中重金属Zn、Cu、Pb、Ni、Cr和Fe的含量,采用地累积指数和潜在生态危害指数评价重金属富集状况,并运用相关分析和因子分析对重金属来源进行了初步探讨.结果表明,旅游区采样点151码头(1#)和江西沟码头(4#)的Zn和Cu元素及布哈河(5#)Cr为轻度污染,其他样点未受重金属污染,所有样点潜在生态危害均为轻微程度,以旅游区码头的潜在生态危害综合评价最高;沉积物中Cr、Fe和TOC存在显著相关性,且在因子1(内源因子)中占绝对负荷,其来源主要与沉积母质有关.此外,入湖河流也带入一定量的Cr元素;Pb和Zn与其他元素相关性较差,分别反映因子2(农业生产活动因子)和因子3(旅游交通排放因子)的迁移转化规律,其来源与人类活动有关;表层沉积物中Cu的积累与内源因子、农业和旅游排放因子均有关;Ni的分布特征主要受内源因子和旅游交通排放因子的影响.本研究表明,青海湖表层沉积物重金属污染及潜在生态危害较轻,其来源除内源因子外,还与湖区农业活动及旅游交通排放等人为因素有关.     

东江沉积物重金属分布特征及污染评价

采用ICP-MS对东江河流沉积物中的重金属进行分析,发现东江沉积物中Cu、Zn、Cd、Hg等重金属呈现相同的变化特点,高值区和低值区基本一致.东江流域沉积物的重金属污染物主要是Cu、Zn、Cd、Hg、Pb,其平均含量分别为157.29、213.21、0.98、0.42、50.77mg·kg-1,均高于中国大陆沉积物背景值.地累积指数法和Hakanson潜在生态危害指数法对东江流域沉积物污染程度和生态危害程度的评价结果显示,东江沉积物中地累积指数从大到小的顺序为Cd、Cu、Zn、Hg、Pb;从总的污染程度来看,东江沉积物中各重金属对生态风险影响程度从大到小的顺序为Hg、Cd、Cu、Pb、Zn;从总的生态风险指数上看,整个东江流域除处于上游的河源市段生态风险低外,处于中游的惠州段生态风险为"较高",处于下游的东莞段生态风险为"极高".     

Using multiple indicators to assess the environmental status in impacted and non-impacted bathing waters in the Iranian Caspian Sea

Human activities have increased in the Caspian Sea in last decades, impacting the coastal zone ecosystems. One of the increasing activities is recreation, including bathing areas in the south of the Caspian Sea, which have been scarcely studied and assessed. Investigating the interactions between human activities and the resulting environmental status in bathing areas, by using adequate indicators and assessment methods, is necessary to undertake management measures for ecosystem restoration. In this study, for the first time, we use the Nested Environmental status Assessment Tool (NEAT) outside the European waters to assess environmental status in bathing waters, to differentiate areas impacted and non-impacted by bathing activities. We have assessed the status in winter and summer seasons, by combining multiple indicators from different ecosystem components (8 physico-chemical, 4 bacteria, 2 plankton, and 1 benthos indicators). Despite the interactions between season and human affection, NEAT determined that the Caspian Seas is not in good status, differentiating, in summer, between impacted and non-impacted bathing areas, with a significant correlation with the number of beach users. Accordingly, management measures should be taken in the southern Caspian Sea to improve the environmental status in general and that of bathing areas in particular.