Harmonisation, standardisation for soil and sediment fractionation studies, and usefulness in assessment and risk management

Single and sequential extraction procedures are often used to study the environmental fate of trace elements from soils and sediments. Although these schemes are quite popular, they are prone to various sources of errors, which require them to be thoroughly controlled. Owing to their operationally-defined character, the only way to compare analytical data is to stick closely to procedures that have been collaboratively studied and written in the form of an operating protocol. Groups of scientists have hence developed ‘harmonised’ procedures that are used as a reference for fractionation studies. A higher level is the formal standardisation of the procedures by official standardisation bodies, which also fulfils the need for achieving the comparability of data obtained by different laboratories from different countries. This paper discusses aspects of harmonisation (consensus obtained by groups of scientists) and standardisation (adoption of standards as mandated by an international organisation) as applied to single and extraction schemes for trace element fractionation studies, including quality control aspects.     

长江口及邻近海域沉积物重金属分布特征及生态风险评价

调查了2009年长江口及其邻近海域表层沉积物中Cu、Pb、Zn、Cd、Cr、Hg、As的含量,平均含量为Cu 27.88 mg/kg、Pb 22.98 mg/kg、Zn 95.88 mg/kg、Cd 0.178 mg/kg、Cr 41.01 mg/kg、Hg 0.031 mg/kg、As 11.40 mg/kg。空间分布上,Cu、Pb、Zn、Cd、Hg、As 6种重金属含量均在杭州湾北部及长江口南汇交界处呈现最大值,而Cr在调查海域的东部逐渐向近岸海域递减。运用主成分分析评价沉积物中重金属污染来源,同时采用Hakanson指数法评价了沉积物重金属生态风险,结果显示：长江口及其邻近海域表层沉积物中重金属元素的潜在生态风险整体表现为轻微。7种重金属元素对长江口及邻近海域潜在生态综合危害的大小贡献顺序为：Cd〉As〉Hg〉Cu=Pb〉Cr〉Zn。Cd的Eir值对RI值的权重贡献最大,即Cd表现为首要的潜在生态风险因子。     

Metal uptake in maize, willows and poplars on impoldered and freshwater tidal marshes in the Scheldt estuary

Foliar Cd and Zn concentrations in Salix, Populus and Zea mays grown on freshwater tidal marshes were assessed. Soil metal concentrations were elevated, averaging 9.7 mg Cd kg^?1 dry soil, 1100 mg Zn kg^?1 dry soil and 152 mg Cr kg^?1 dry soil. Cd (1.1–13.7 mg kg^?1) and Zn (192–1140 mg kg^?1) concentrations in willows and poplars were markedly higher than in maize on impoldered tidal marshes (0.8–4.8 mg Cd kg^?1 and 155–255 mg Zn kg^?1). Foliar samples of maize were collected on 90 plots on alluvial and sediment‐derived soils with variable degree of soil pollution. For soil Cd concentrations exceeding 7 mg Cd kg^?1 dry soil, there was a 50% probability that maize leaf concentrations exceeded public health standards for animal fodder. It was shown that analysis of foliar samples of maize taken in August can be used to predict foliar metal concentrations at harvest. These findings can therefore contribute to anticipating potential hazards arising from maize cultivation on soils with elevated metal contents.     

吕四渔场近岸海域水质和沉积物中多氯联苯(PCBs)的分布特征

采用气相色谱测定了吕四渔场水质和沉积物样品中的多氯联苯(PCBs),并分析了其分布特征。结果显示,吕四渔场水质和沉积物中的PCBs平面分布特征为南部近岸高,而北部近岸较外海低,调查海域PCBs含量有逐年升高的趋势。水质中以低氯代PCBs同族体为主,沉积物中以高氯代PCBs同族体为主,含6个氯原子的PCBs在水中和沉积物中含量都比较高。为了削减PCBs对环境和人类的危害,我们要加强控制、管理、研究和合作。     

Fluvial sediments in the Alagxa Plateau as a dust source: iron mineralogical and geochemical evidence

The Alagxa Plateau, in the margin of the northeastern Tibetan Plateau, is one of the most important dust source areas in East Asia, and the widespread sandy desert in the area is important both as a reservoir and a source of eolian silty. The northeastern margin of the Tibetan Plateau is one of the most actively-growing mountain belt on earth, and has large amounts of debris, with masses of fine grained material, which were continuously mobilized and deposited in the Alagxa Plateau by rivers, forming broad alluvial fans. It is possible that the role of fluvial sediments as a source of silty dust in the Alagxa Plateau has been underestimated. In this study, we test this hypothesis by investigating the iron mineralogical and geochemical characteristics of the fluvial sediments and the surface material of the sandy desert in the Alagxa Plateau, and comparing them with paleo-eolian dust deposits(loess) in the adjacent Chinese Loess Plateau(CLP) to investigate the possible linkages among the fluvial sediments, sandy desert and the last glacial loess of the CLP. The results show that sandy desert typically have high contents of goethite, and high ratios of goethite to hematite, similar to the fluvial sediments in the Alagxa Plateau. Based on the major element characteristics, field investigations and the results of previous studies, we found a genetic link between the silt component of the fluvial sediments and the sandy desert in the Alagxa Plateau with high value of Gt(goethite) and similarity of the Gt/(Hm(hematite)+Gt) ratio. But the silt component of the sandy desert main come from the adjacent fluvial sediments. The iron mineralogical characteristics(χ(magnetic susceptibility), χARM(anhysteretic susceptibility), SIRM(saturation isothermal remanent magnetization) and SIRM_(AF100 mT)(SIRM demagnetized at 100 mT)) of the CLP samples overlap with those of the fluvial sediments in the Alagxa Plateau, but there is a mismatch with the sandy desert samples. This suggests that the fluvial sediments are the source of a large amount of silty material which could be transported to the CLP. Therefore, we conclude that the fluvial sediment in the Alagxa Plateau is an important source of eolian silt, which is deposited in downwind region, and that this source has been previously underestimated.     

洞庭湖表层沉积物营养盐和重金属污染特征及生态风险评价

为探究洞庭湖表层沉积物中营养盐和重金属的空间分布特征与生态风险,2012年2月和2013年4月在东、南、西洞庭湖各取3个共计9个具有代表性样点的表层沉积物,测定其有机质（OM）、总氮（TN）、总磷（TP）、镉（Cd）、汞（Hg）、砷（As）、铅（Pb）和铬（Cr）的含量。结果表明,洞庭湖表层沉积物中 OM、TN 和 TP 的含量分别为1．48％～4．22％、382～2217 mg／kg 和142～716 mg／kg,与国内其他湖泊（水库）相比,OM和 TN 含量处于中等水平;OM和 TN 的空间分布相似,表现为南洞庭湖区＞东洞庭湖区＞西洞庭湖区,TP 表现为东洞庭湖区＞西洞庭湖区＞南洞庭湖区。洞庭湖表层沉积物中,Cd、Hg、As、Pb 和 Cr 的含量分别为0.60～20．70 mg／kg、0.090～0．640 mg／kg、10．4～83．7 mg／kg、16．9～95．8 mg／kg 和59．0～199．0 mg／kg,其中 Cd 和 As 超过土壤环境质量三级标准,是主要的重金属污染物;Cd 和 Hg 的空间分布相似,表现为南洞庭湖区＞西洞庭湖区＞东洞庭湖区;As、Pb 和 Cr 的空间分布相似,表现为南洞庭湖区＞东洞庭湖区＞西洞庭湖区。初步评价结果显示,除 TP 外,其余营养盐和重金属均具有引起较低生态风险的可能性,横岭湖和虞公庙的 Cd、As 和 Cr 以及洞庭湖出口的 Cr 具有引起较高生态风险的可能性;受 Cd 和 As 含量较高的影响,南洞庭湖区具有较高的生态风险。     

磷在富营养化湖泊沉积物-水界面的循环

沉积物中部分固定的磷可通过分解或溶解作用而释放磷酸盐到沉积物间隙水中;再生的磷可能释放到上覆水体中,或在沉积物中作为一种自生相而再沉淀,或被沉积物的其它组分所吸附。本文描述了磷在沉积物-水界面的迁移过程,并对影响磷循环的因子及其磷自沉积物释放的机制作一简要概述。     

岱海表层沉积物中影响氨氮释放的模拟研究

以北方半干旱地区典型内陆封闭湖泊岱海为研究对象,采用室内模拟实验方法,开展了温度、pH、溶解氧及水生植物对湖泊沉积物中NH4^＋—N释放的影响研究。结果表明,温度升高,中性条件,厌氧条件均有利于NF4^＋-N的释放。狐尾藻对上覆水NH4^＋-N含量的有效控制作用是其抑制底泥释放、同化吸收作用和增强上覆水氧化条件等综合作用的结果,植物修复是控制湖泊富营养化水平的有效措施。     

湘江衡阳段河漫滩沉积物粒度特征与历史洪水事件

[目的]分析河漫滩沉积记录的历史时期洪水信息,揭示极端洪水事件和洪水发生规律,为防洪减灾提供指导.[方法]根据湘江河漫滩沉积剖面91个样品的粒度分析,结合AMS 14C精确测年,分析湘江衡阳段河漫滩剖面粒度特征与洪水事件.[结果]①河漫滩沉积物粒度组成以粗粉砂、粗砂、极细砂为主.粒度参数显示,剖面洪水沉积动力较强,分选...     

青藏高原爬坡沙丘地表沉积物特征分析——以柴达木盆地托拉海河为例

为了阐明青藏高原爬坡沙丘的物源及沉积学意义并揭示其形成机理,对托拉海河爬坡沙丘进行断面采样,分析爬坡沙丘不同地形部位的粒度与地球化学元素特征。结果表明,托拉海河爬坡沙丘地表沉积物的粒度组成总体以极细砂、细砂、中砂为主,粒度特征表现出明显的风成特点;不同地形部位,粒度特征呈现不同的递变规律,自河床到迎风坡顶粒径变粗,分选变好,迎风坡顶到背风坡,粒径粗细混杂,分选变差。沉积物地球化学元素组成以Si、Al、Ca为主,和上陆壳(UCC)相比,除Co、As、CaO、SiO2以外,其余元素都有一定的亏损,不同部位化学元素分布具有一定相似性,且常量氧化物之间有较好的相关性,表明其具有相似的沉积环境。A-CN-K图解及CIA值揭示了托拉海河爬坡沙丘地表沉积物化学风化处于较低程度,大部分化学元素没有显著的风化或迁移,整体属于早期去Na、Ca的阶段;A-CNK-FM图则表明整个断面Fe、Mg元素在空间分布上存在一定的差异,Fe、Mg流失主要是差异风力风选的结果。从化学风化指标来看,不同地形部位风化程度不同,河床风化程度最弱,山地迎风坡的风化程度最强;河床与河流阶地的物源呈现多样性,而迎风坡和背风坡物源较为单一,可能是古沙翻新和就地起沙。因此,初步认为托拉海河爬坡沙丘的形成经历了两个阶段:一是古沙丘形成阶段;二是现代爬坡沙丘形成阶段。在不同空间尺度上,托拉海河爬坡沙丘地表沉积物的理化特征差异与风动力和水动力的差异有关,反映出沉积物对风、水交互作用的响应。