汕头南澳白沙湾养殖区沉积物重金属形态及潜在生态风险

Heavy metal speciation and potential risk assessment in sediments from the mariculture areas in Baisha Bay,Nanao,Shantou

采用欧洲标准局连续提取法(Sequential extraction procedure of European Community Bureau of Reference)测定了汕头南澳白沙湾4种不同类型养殖区(鱼类、贝类、龙须菜和贝藻混养区)表层和柱状沉积物中4种重金属(Pb、Ni、Cu和Zn)不同形态的含量,初步评估了4种重金属的生物可利用性。结果表明,白沙湾表层沉积物中Pb和Zn主要以可还原态存在,而Ni和Cu均以残渣态存在。鱼类养殖区表层沉积物中4种重金属的生物可利用性较其他养殖区要高。4个养殖区柱状沉积物中4种重金属的生物可利用态总体上均随深度增加而减少;其中鱼类养殖区减小幅度较其余三种养殖区要大。形态风险准则评价表明,Zn对白沙湾水环境危害最重,已达到中等程度危害;Ni和Cu在各养殖区均为低危害;Pb在鱼类养殖区无危害,而在其余三个养殖区为低危害。

Nanao Island is one of Guangdong Province＇s largest mariculture bases in Southern China.The speciation of heavy metals（Pb,Ni,Cu,Zn） in four type mariculture（fish,shellfish,Gracilaria lemaneiformis,and shellfish ＋ seaweed） areas＇s surface sediments and sediment cores from Baisha Bay,Nanao Island were determined according to the 3-stage sequential extraction procedure proposed by the European Community Bureau of Reference,to evaluate the heavy metal bioavailability.In surface sediments,Pb and Zn mainly occurred in oxidizable fraction,while Ni and Cu mainly occurred in residual fraction.Bioavailability fraction（Step1＋Step2＋Step3） of heavy metals in the surface sediment of fish cage culture area was higher than shellfish,Larege seaweed,and the mixed culture areas.In sediment cores,bioavailability fraction of four heavy metals in the four type mariculture areas decreased with the increase of depth.Bioavailability fraction of heavy metals in the sediment core of fish cage culture area was significant higher than the other three cultures.Risk assessment code analysis indicated that Zn was in medium risk category;Ni and Cu posed low risk to aquatic environment;Pb was no risk in fish cage culture area and low risk in other three mariculture areas.