Fractionation of heavy metals in surface sediments of Taihu Lake, East China

The BCR (European Communities Bureau of Reference) three-step sequential extraction procedure was applied to fractionate heavy metals in the sediment of Taihu Lake. For the determination of total metal concentration of the sediments, sample digestion was achieved by using HF/H2O2/HNO3 (2/1/1) acid mixture in a microwave-irradiated closed vessel system. The concentrations of Cd, Ni, Cr, Zn, Cu and Pb in various extracts solutions were analyzed by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). The results obtained from the BCR three-step sequential extraction indicated relatively high mobility of Zn, Cu, Pb and Ni in the sediments while Cd and Cr were poorly mobile. Enrichment of heavy metals was found in the sediments collected in the northern parts of Taihu Lake. In the sediments collected in the southern and western sides of the Lake, heavy metal concentrations were relatively low. The relationship between total organic carbon (TOC) and heavy metals concentrations in the sediments is discussed.     

南太湖沉积岩芯中金属和营养元素的垂向分布特征及其意义

通过太湖南部钻孔(THS)沉积物^137Cs和^210Pb、总有机碳、总氮、总磷、粒度和金属元素分析，探讨其垂向分布特征及意义。表层^137Cs比活度高值表明表层沉积物具有混合作用的特征。粒度分析表明，沉积物呈现随深度变浅而变粗的总体趋势；绝大多数金属元素含量垂向上的变化与粘土含量呈正相关。铁锰界面循环也影响着金属元素的迁移。沉积物W(C)／w(N)比值的状况显示了其有机质主要为陆源性质，但最近60年内来源于水体的有机质呈现增加的趋势。沉积物中元素的演化序列表明，元素铅受到明显的人为活动来源的污染。     

Spatial distribution and ecological risk assessment of heavy metals in surface sediments from a typical plateau lake wetland, China

Surface sediment (0-15 cm) samples were collected from 31 different grid points throughout the Yilong Lake in April 2004. Samples were subjected to a total digestion technique and analyzed for As, Cd, Cr, Pb, Ni, Cu, and Zn in order to study spatial distribution characteristics based on Kriging method and assess their ecological risks posed by these heavy metals. Results showed that the mean concentrations of these heavy metals were lower than potential effect levels. Patches of higher heavy metal concentrations occurred in the inflow area of the Cheng River and northeast area nearby the road and railway. The higher concentrations of As and Cr also appeared in the east area (lake outlet), while the patches of lower concentrations were uniformly distributed at the southwest corner between Luosewan and Xiaoguoxi. The heavy metal loads such as As, Cd and Pb might come from the common sources due to industrial sewage and traffic pollution, while higher concentrations of Ni, Cr, and Zn in these sediments were dominated by parent rocks. However, Cu originated from both sources. Sediments with respect to As, Cd and Cu were grouped below the effect range low (ERL) at all sites, and with respect to Cr and Pb were grouped into the range from ERL to the effect range median (ERM) at more than 50% of sampling sites. The mean heavy metal toxic units in the Yilong Lake decreased following the order Pb > Cr > As > Ni > Zn > Cd > Cu, with higher contributions to the sum of toxic units of Pb, Cr and As.     

太湖不同湖区沉积物重金属含量季节变化及其影响因素

以太湖东北部梅梁湾、胥口湾、贡湖沉积物中重金属为研究对象,研究各湖区沉积物中As、Cd、Cu、Pb、Zn含量的年际变化规律及其与沉积物间隙水温度、pH、Eh值以及沉积物有机质、总氮、总磷、粒径等理化指标的相关关系.结果表明:沉积物中重金属含量及其年际的变化与其污染状况有一定的相关关系;富营养化程度较高的梅梁湾沉积物中重金属含量的最大值出现在9月,其他两个湖区的最大值均出现在6月;沉积物中重金属含量受到温度、pH值、Eh值等物理因素的影响,且与温度、pH值和Eh值有一定的正相关关系;沉积物有机质、总氮、总磷、粒径等因素也会对沉积物中重金属含量产生影响;有机质含量与重金属含量有很好的正相关性,粒径与重金属含量呈正相关,总氮、总磷与重金属含量呈负相关.     

Characterization of phosphorus species and modeling for its organic forms in eutrophic shallow lake sediments,North China

Variations of phosphorus （P） and its species in surface sediment of Baiyangdian Lake, a eutrophic shallow lake located in North China, were investigated through combination of field survey and numerical calculation based on cluster analysis. P fractionation was performed by a sequential extraction scheme, categorized as loosely bound P （NH4Cl-P）, reductant soluble P （BD-P）, metallic oxide bound P （NaOH-P）, calcium bound P （HCl-P） and organic P （Org-P）. P concentrations exhibited regional similarities and a total of four sub-areas were identified in which the same rank was HCl-P 〉 Org-P 〉 BD-P ,=NaOH-P 〉NH4Cl-E NH4Cl-P, BD-P and Org-P were found to contribute to P enrichment in overlying water column. Specifically, labile Org-P acted as a potential pool with a greater contribution in aerobic layer compared to anaerobic layer. A hysteresis （lag = 4 months） existed when labile Org-P concentration was negatively correlated with aerobic layer thickness. In view of magnitude of identified P contributors in sub-areas, higher potential of P release was present in Fuhe River and Tang River estuary areas. On the basis of calibration and verification, the mathematical model with parameter settings applied in this study was improved to serve as a tool for limnology management and eutrophic control.     

深圳蛇口渔港沉积物重金属分布及潜在生态风险评价

沉积物重金属污染对水生生态系统具有潜在危害.渔港是海岸带水环境的重要组成部分.对取自深圳蛇口渔港的10个表层沉积物样品中的As、Cd、Cu、Pb和Zn等典型重金属元素进行了分析,探讨了其空间分布;运用地积累指数法(Igeo)和生态危害指数法(RI),评价了表层沉积物中重金属的富集程度和潜在生态风险,初步探讨了其污染来源.结果表明:(1)蛇口渔港海域沉积物重金属Cu的污染十分严重,Zn和Pb污染较严重,其浓度均为港内>港口>港外;(2)渔港内沉积物重金属的富集达重度污染程度,潜在生态危害风险强.其中,又以Cu的富集程度最高,潜在生态危害风险最强;(3)渔港内Cu的污染,可能与电子工业废水的排放,以及渔业特有的防附着生物涂料有关.     

Assessment on contaminations in sediments of an intake and the inflow canals in Taihu Lake,China

As the second largest freshwater lake in China, Taihu Lake provides water supply to approximately 32 million inhabitants around the lake. However, dramatically increased pollution has threatened the safety of drinking water supply in recent years. In the present study, we investigated the contaminations of nutrients and heavy metals in the sediments of an intake and inflow canals in Gonghu Bay, Taihu Lake. Moreover, we also examined the impact of human activities on spatial distribution characteristics of contaminations. Our results showed that the intake presented relatively lower concentrations of phosphorus and nitrogen compared with inflow canals. However, the concentrations of Cr, Ni, Cu, Zn and Pb in the sediments of the intake exceeded the lowest effect level (LEL) values, indicating a potential risk to drinking water resource. In addition, the concentrations of Ni in the sediments of Tianji Canal and Jinshu Canal exceeded the severe effect level (SEL) value. More importantly, the concentrations of Cu in the sediments of Tianji Canal exceeded three times of the SEL value. Multivariate statistical analysis confirmed that the domestic sewage primarily contributed to the nutrient accumulation, and the leakage of electronic trash dominated the enrichment of metals in the sediments. Taken together, more effort should be made to ensure the security of water resources in Taihu Lake, especially for the treatment of domestic sewage and industrial wastewater.     

Assessment of enrichment,geo-accumulation and ecological risk of heavy metals in surface sediments of the Msimbazi mangrove ecosystem,coast of Dar es Salaam,Tanzania

Results of the assessment of enrichment, accumulation and the ecological risk associated with three heavy metals (Cd, Cu and Pb) and one metalloid (As) in surface sediments of Msimbazi estuary are presented. Surface sediment samples (0–5 cm) were collected from Msimbazi River estuary in September 2016 using handheld PVC short corers. Long-sediment cores from the site were also collected using PVC pipes and their vertical profiles of metals concentrations assessed with the aim of establishing site-specific baseline metals concentrations. The established site-specific baseline values were used for the determination of normalised enrichment factors (EF) and geoaccumulation (Igeo) of metals instead of using average crustal values. Iron-based enrichment factors show that the sediments of Msimbazi have experienced enrichment of metals that originate from anthropogenic sources of pollution (EF > 1). Geo-accumulation results indicate that Msimbazi sediments can be designated as uncontaminated to moderately-contaminated with As, Cd and Pb (class 1–2). Geoaccumulation indices for Cu indicate that sediment can be designated as uncontaminated to moderately contaminated (class 1) and moderately to strongly contaminated (class 3). Results show further that the Ecological Risk associated with the accumulation of these metals in Msimbazi sediments was low based on Hakanson approach.     

乌梁素海沉积物重金属生物活性及环境污染评估

为阐明乌梁素海沉积物重金属生物活性及理化性质对重金属形态变化的影响,对湖泊重金属污染修复治理方面提供科学依据,2011年1月在乌梁素海9个站点采集表层沉积物样品,采用改进BCR逐级提取法分析Cu、Zn、Pb、Cr、Cd、Hg、As等7种重金属元素的形态,利用活性系数与迁移系数对重金属生物活性进行研究;结合沉积物理化性质,系统探讨影响重金属化学形态与生物活性的因素;应用次生相与原生相比值法,从重金属形态学角度对沉积物重金属状况进行评估.结果表明,(1)沉积物中重金属活性系数的大小顺序为 Cd>Hg>Zn>Cu>Pb >As>Cr;重金属的迁移系数为 Cd>Hg>Zn>Cu>As>Pb>Cr.(2)沉积物物理化学性质和重金属总量对各种化学形态重金属含量影响程度明显不同.重金属总量对残渣态影响较大;pH对酸可提取态、有机物和硫化物结合态影响较大;有机质与酸可提取态、有机物和硫化物结合态有较大相关性;盐度与酸可提取态、有机物和硫化物结合态有一定的相关性.总氮、总磷与有机物和硫化物结合态有一定的相关性.(3)从重金属形态角度评价,7种重金属除Cd外,污染程度并不大,全湖KRSP的平均值大小顺序为Cd(1.66)>Cu(0.84)>Hg(0.72)>Zn(0.42)>Cr(0.15)>Pb(0.14)>As(0.06).结合总量、生物可利用性与形态学评价,乌梁素海重金属 Cd 是生物活性最强、污染最严重的金属,Hg污染次之,应该对Cd与Hg给予特别关注.     

Mercury distribution,speciation and potential ecological risk assessment in sediments from Lake Taihu,China

Abstract

Twenty-one surface sediments collected from seven surroundings areas of Lake Taihu in two different years were analyzed for total mercury (THg) concentrations, physicochemical characteristics and speciation using a sequential extraction method to assess spatial distribution, sources, and potential ecological risk. Surface sediments from Lake Taihu contained elevated levels of Hg in two sampling years with THg levels ranging from 77 to 346?ng/g (mean 145?ng/g) in October 2010 and ranging from 122 to 573?ng/g (mean 266?ng/g) in November 2012, respectively. The mean THg concentrations in all studied surface sediments exhibited an increasing trend over time. The oxidizable fraction (F3) and residual fraction (F4) were the predominant Hg species in sediments, while more mobile Hg phases of acid-soluble fraction (F1) and reducible fraction (F2) made up less than 0.5% THg. Significant relationships were found between total organic carbon (TOC) and THg and geochemical speciation indicating an important role for organic matter in affecting distribution, mobility, and bioavailability of Hg in sediments. As evidenced by Hakanson’s potential risk index the total ecological risk of Hg was low in the entire Lake Taihu in 2010 but considered moderate in Zhushan Bay, West Coast, and Meiliang Bay in 2012. These findings provide conservation managers with information needed to more effectively regulate the environment of Lake Taihu.     

Modeling linkages between sediment resuspension and water quality in a shallow,eutrophic, wind-exposed lake

The interactions between bed sediments and the water column in shallow, eutrophic lakes have tremendous implications for the fate and transport of nutrients in those water bodies. This has resulted in the development of water quality models for lakes incorporating the processes of sediment resuspension. Reliable resuspension models are thus needed to accurately represent this phenomenon. In this paper, three different sediment-resuspension models are combined with a hydrodynamic and water quality model, dynamic lake model-water quality (DLM-WQ), and the resulting models are used to simulate nutrient distributions in the highly eutrophic Salton Sea, California, USA. One of the resuspension formulas is based upon sediment characteristics as well as the bed shear stress exerted by wind-induced waves and currents, while the other two are standard, power-law-type formulas for cohesive sediments with two different exponents. The outputs for water quality variables, such as temperature, chlorophyll a, dissolved oxygen and nutrients, obtained from the three resulting models and from an earlier DLM-WQ run with a simple empirical sediment-resuspension model are compared with measured data. The level of agreement between the simulations and the measured data is assessed by using both statistical and graphical model evaluation methods, including measures of residual errors, sample autocorrelations, t-tests, and box plots. Based on these assessments, DLM-WQ with an extended version of the García and Parker [García, M.H., Parker, G., 1993. Experiments on the entrainment of sediment into suspension by a dense bottom current. J. Geophys. Res.-Oceans 98, 4793–4807] relationship gave the best results for water quality in the Salton Sea, confirming that the use of formulas with more information on the sediment characteristics yields more accurate results. To the best of our knowledge, this is the first effort to combine water quality models for lakes and reservoirs with a sediment-resuspension model which was originally intended for open-channel flows. The simulations confirm that sediment resuspension is the most dominant process in the Salton Sea's nutrient cycling. The effect of proposed physical changes to the Salton Sea on water quality characteristics is also addressed.     

Seasonal variation of heavy metals in sediment of Lake Ulansuhai,China

Sediment samples were collected from 10 sites in Lake Ulansuhai during summer and winter 2009 to reveal seasonal variations in sediment heavy metal levels. The geoaccumulation index (GI) was calculated to assess the severity of metal pollution. The GI values suggest that, in winter, the lake sediments were polluted slightly with Cu (GI=0.66–1.34), Zn (GI=0.59–1.35), Cr (GI=0.49–0.82) and Pb (GI=0.60–0.96), and moderately with Cd (GI=1.03–4.23). The degree of pollution was higher in winter than in summer. By contrast, the degree of pollution was higher in summer than in winter for Hg and As. Correlation analysis can be used to identify factors influencing seasonal variations in heavy metals. The concetrations of Cu, Zn, Pb, Cr and Cd were negatively correlated with water temperature and hydrodynamic conditions, but positively correlated with organic matter concentration in the sediments and with a sediment particle size of<63 μm (p<0.01). Meanwhile, Hg and As concentrations were affected by redox state and salinity. Among the metals tested, Hg and Cd posed a more serious pollution risk.     

Organophosphate esters in sediment from Taihu Lake,China: Bridging the gap between riverine sources and lake sinks

• Eleven OPEs were detected in river sediment and lake sediment in Taihu Lake. • TnBP dominated in river sediment, while TBEP dominated in lake sediment. • A strong correlation existed between logK_oc and logK_ow of OPEs. • Vertical profiles of OPEs in sediment cores varied according to sampling location. Surface sediment samples from Taihu Lake in China and its inflow rivers, along with two lake sediment core samples, were collected and analyzed for organophosphate esters (OPEs). The concentrations of total OPEs varied from 28.60 ng/g to 158.72 ng/g (median: 54.25 ng/g) in river surface sediment and from 62.57 ng/g to 326.84 ng/g (median: 86.37 ng/g) in lake sediment. Tributyl phosphate (TnBP) was the predominant compound in river surface sediment, and tris(2-butoxyethyl) phosphate was predominant in lake sediment. High contamination occurred in the north-west region, which was related to the high level of urbanization and high usage of OPEs. The sediment–water partition coefficients of OPEs (logK_oc) were calculated, showing a significant correlation with logK_ow (p<0.05). The concentration and composition of OPEs in two sediment cores varied due to the different sampling locations, with more OPE species found in the northern region than in the southern one. Principal component analysis and positive matrix factorization indicated that sewage discharges, vehicle emissions, and atmospheric deposition were the possible sources of OPEs in Taihu Lake sediments. Tris(1-chloro-2-propyl) phosphate, tris(2-chloroethyl) phosphate, and TnBP were the main OPEs causing ecological risks.     

中国三个不同富营养化湖泊沉积物中Cu、Zn赋存特征及其与营养盐的相关性分析

对太湖、南四湖、白洋淀三个不同富营养化湖泊沉积物进行采样,采用Tessier连续提取法,测定了3个湖泊表层沉积物中Cu、Zn两种重金属的赋存形态,并初步探讨了重金属各形态与沉积物及上覆水中营养盐的相关关系。结果表明,沉积物中重金属总量以白洋淀最高,太湖最低,但重金属污染程度为太湖＆gt;南四湖＆gt;白洋淀,太湖Cu污染指数为1.34~1.6,白洋淀Cu污染指数仅为0.79~1.17。沉积物中重金属赋存形态Cu主要以残渣态和有机质结合态为主（二者之和占73%以上）, Zn则以残渣态和Fe-Mn氧化态占优（二者之和比例达83%以上）,含量最少的均为可交换态。不同湖泊沉积物重金属赋存形态差异较大,太湖残渣态重金属占总量的比例最小（Cu为43%~56%,Zn为49%~63%）,南四湖残渣态占的比例最大（Cu为59%~82%、Zn为64%~77%）;可交换态比重在太湖中最高（Cu占3.2%~5.6%,Zn为1.3%~1.5%）,在南四湖中最低（Cu为1.1%~2.9%,Zn未检出）。从“非稳定态”重金属（除残渣态外的四种形态之和）所占比例看,相较其它两个湖泊,太湖沉积物中重金属污染人为输入的活性态占较大比重,具有较高的二次释放风险。相关性分析得出,重金属Cu的可交换态与上覆水中总氮及总磷之间存在着极显著的正相关关系,碳酸盐结合态Cu与沉积物中营养盐呈现出显著的负相关性,说明水体的富营养化程度加剧可能会增强沉积物中Cu向水体释放的风险。     

Speciation of heavy metals in sediments from the Scheldt estuary,Belgium

A simple three-step sequential extraction procedure was applied to study the speciation of heavy metals in sediment from Scheldt estuary, and their relationship to sediment grain size and organic matter content. The sedimentary metal content was fractionated into carbonate and exchangeable, metals bound to organic matter and residual fractions. Sedimentary total metal content was also determined using an industrial microwave (ETHOS 900) HF/HNO₃ extraction method. The extracts were analysed for metals using inductively coupled plasma atomic emission spectrometry. The bioavailable fraction (exchangeable and metals bound to organic matter) comprised less than the other forms. Residue metals were the dominant form of metals in almost all studied sites. The average total metal content for the studied sites decreased in the order Fe>Cr>Cu>Co>Zn>Pb>Cd. Based on average values for the studied sites, the highest bioavailable metals in sediments were Cd (38%) from Westkapelle, Zn (17%) from Yerseke, Co (12%) from Domburg, Cr (9%) from Vlissingen, Fe and Pb each (2%) from Yerseke, and Cu (1%) from Domburg. Metal recovery was good, with<10% difference between the total metal recovered through the extractant steps and the total metal determined using HF/HNO₃ extract.     

成都市河流表层沉积物重金属污染及潜在生态风险评价

根据流经成都市内的三条河流（府河、南河、沙河）表层沉积物重金属数据，采用Hakanson潜在生态危害指数法对重金属的潜在生态风险进行了评价。结果表明（1）重金属潜在的生态危害因子（Er^i）说明大多属于轻微生态危害范畴，产牛生态危害的主要重金属是Hg、Cd，Cu、Pb次之，As影响最小；（2）多种重金属的生态系统的潜在生态风险指数（RI）表明河流重金属污染属于轻微生态危害和接近中等生态危害，其受危害程度由强至弱的次序为：府河，南河，沙河。     

污染沉积物中重金属的释放及其动力学

研究了广州城市水体污染沉积物在不同pH条件下释放重金属的能力以及酸性条件下重金属的释放动力学。研究结果表明,重金属从污染沉积物中的释放主要是在酸性(pH<4)条件下发生,并且释放率随pH的升高而迅速降低。重金属的释放顺序大致为Cu≈Zn≈Ni>Pb。重金属的释放动力学过程可分为两个阶段,第一阶段一般认为是重金属从沉积物表面的快速解吸过程,第二阶段则可能是重金属缓慢地从沉积物内部微孔向溶液的扩散过程。释放动力学过程可以用Elovich方程和双常数速率方程(Freundlich修正式)较好地描述。     

Phosphorus speciation and effects of environmental factors on release of phosphorus from sediments obtained from Taihu Lake,Tien Lake,and East Lake

Phosphorus is considered the primary nutrient limiting eutrophication. The release of phosphorus from sediments not only provides hydrophytes with essential nutrients, but can also produce entrophication in lakes. In this study, the sediment characteristics, phosphorus speciation, and environmental factors affecting phosphorus release from sediments from Taihu Lake, Tien Lake, and East Lake were investigated. The results indicated that phosphorus levels of sediments ranged from 647 ± 67 to 2343 ± 122 mg/kg. Inorganic phosphorus comprised the majority of total phosphorus. The main phosphorus speciation of sediments obtained from Taihu Lake and Tien Lake was Residual-P, and the main phosphorus speciation of sediment obtained from East Lake was NaOH-P. Phosphorus release occurred in acidic and alkaline conditions but more frequently under alkaline conditions. The amount of phosphorus released from the sediments increased as the disturbing intensity rose. In addition, less phosphorus was released in natural than anaerobic conditions. The amount of phosphorus released was elevated as temperature increased.     

东昌湖表层沉积物的磷赋存形态

对东昌湖表层沉积物,应用Ruban等在欧洲标准委员会框架下发展的淡水沉积物磷形态分离法(SMT)测定铁铝结合态磷(Fe/Al-P)、钙结合态磷(Ca-P)、无机磷(IP)、有机磷(OP)和总磷(TP),分析TP与总氮(TN)和总有机碳(TOC)之间的相关性,结果表明,东昌湖表层沉积物的总磷含量在428.67—933.95 mg.kg-1之间,平均含量为597.78 mg.kg-1;沉积物的磷以IP为主,占TP的70.06%—91.08%,以OP为辅,占TP含量的12.31%—26.40%.IP中以Ca-P为主,占TP含量的64.67%—94.51%,Fe/Al-P仅占TP的2.57%—10.40%,从各形态磷占TP的百分比来看,Ca-P>OP>Fe/Al-P.东昌湖表层沉积物向上覆水体释放磷的潜力不大.东昌湖沉积物TP含量与梁子湖、太湖、洪泽湖、东湖和南四湖的TP含量相当,低于玄武湖和滇池;Fe/Al-P含量比我国其它湖泊要小1—2个数量级;Ca-P含量较国内其它湖泊的Ca-P含量高.表层沉积物的TP与TN、TOC之间呈极显著正相关关系,TP分布受到TN和TOC的输入影响.