杭州湾及其邻近海域表层沉积物的沉积环境分区及重金属污染特征分析

Analysis of surface sediment environment division and heavy metal pollution character in Hangzhou Bay and its adjacent areas

于2017年春季和2018年春季,分两个航次,在杭州湾及其邻近海域采集了表层沉积物样品,并对其粒度组成及重金属含量进行了测定。结果表明,研究区域表层沉积物的粒级组成以砂和粉砂为主,平均占比分别为38.0%和55.4%。根据粒级组成的区域分布特征,将研究区域分为长江河口现代沉积区(Ⅰ-1)、钱塘江河口现代沉积区(Ⅰ-2)、长江羽状锋面积聚区(Ⅱ-1)、长江次级锋面积聚区(Ⅱ-2)、岛屿风化影响区(Ⅲ)、残留砂混合沉积区(Ⅳ)等4大类6个亚区。通过比较不同区域重金属含量发现,总体分布趋势为Ⅱ-1区和Ⅱ-2区含量较高,Ⅰ-2区和Ⅳ区含量较低,Ⅰ-1区和Ⅳ区相对居中。单因子污染指数评价结果显示,Ⅱ-1区和Ⅱ-2区的Cu、Pb、Zn、As、Cd、Hg已呈现出污染态势,需引起关注;Cr则未呈现出污染态势。

The grain size composition and heavy metal contents were determined in surface sediments of Hangzhou Bay and its adjacent areas.The samples were obtained from two spring cruises in 2017 and 2018.The results showed that the grain size composition of the study area was dominated by sand and silt,with average proportions of 38.0%and 55.4%,respectively.The study area was separated into six regions based on the grain size distributions,including the Yangtze River estuarine modern deposition region(Ⅰ-1),Qiantang River estuarine modern deposition region(Ⅰ-2),Yangtze River plume front region(Ⅱ-1),Yangtze River secondary plume front area(Ⅱ-2),island weathering related area(Ⅲ),and sandy relict deposition region(Ⅳ).The heavy metal contents were high in regionsⅡ-1 andⅡ-2 and low in regionsⅠ-2 andⅣ.A pollution trend was observed based on the contents of Cu,Pb,Zn,Cd,As,and Hg in regionsⅡ-1 andⅡ-2,wherein more attentions is needed.However,the Cr content was evidently lower than the background value.