不同养殖方式下底泥中硫与重金属的环境行为

Environmental Behavior of Sulfur and Heavy Metal in Sediments of Aquaculture-pond with Cultivation of Different Methods

为探究不同养殖方式下底泥中污染物的环境行为,该文以海参养殖池塘为研究对象,分析了半开放与封闭养殖方式下硫与典型重金属的分布特征及其相互关系。结果表明:封闭养殖池塘的还原性无机硫(RIS)含量较高,各形态分布为酸可挥发性硫化物(AVS)>铬还原性硫(CRS)>元素硫(ES),AVS向CRS的转化受到一定程度的阻碍,而半开放式池塘中RIS的形态分布为CRS>AVS>ES,AVS可有效转化为CRS;受有机质(TOC)含量、水力扰动强弱等因素的影响,半开放养殖方式的硫化物环境风险较小,随着养殖时间增加,封闭养殖池塘底泥的环境风险增大;底泥重金属与TOC关系密切,来源可能是天然饵料以及有机药剂的降解;研究区域底泥中Cr、Cu、Zn、Cd优势态均为残渣态,而Pb以可还原态为主,养殖方式对重金属形态的分布影响较小;采用不同的评价方法得出的重金属污染等级存在差异,Cd污染应引起重视;底泥中AVS与Cu生物有效态呈显著正相关,表明AVS可有效限制Cu的生物毒性,而CRS与Pb生物有效态的负相关性显著,表明Pb生物有效态增加不利于CRS生成。

In this case study,sea cucumber is bred adopting two different methods which involve two different types of aquaculture ponds:semi-open pond,sealing pond.To explore the environment behavior of pollutants in the sediments of two types of ponds,a research was conducted to analyze the distribution characteristics of sulfur and heavy metal and correlation between them.The results showed that content of the form of reduced inorganic sulfide(RIS)in the sealing pond was relatively high,and transformation from acid volatile sulfide(AVS)to chromium(I)-reducible sulfur(CRS)was impeded to a certain degree;however,in semi-opened pond AVS could be effectively converted into CRS.Affected by TOC content and the strength of hydraulic disturbance,environmental risk of sulfide in semi-opened pond was less,and with the extension of aquaculture time,the environmental risk of sediment in the sealing pond would increase.Heavy metal in sediment was in close relation with TOC probably due to the degradation of natural baits and organic insecticides.As for heavy metals(Cr,Cu,Zn and Cd)in the sediments,their dominant forms were totally in residual fraction state,while the dominant form of Pb belonged to the reducible fraction state.It appeared that the cultivation methods slightly affected the morphological distribution of heavy metals;in evaluating the pollution level of heavy metal,the results depended on the evaluation methodology,i.e.,the results obtained may differ when using different evaluation methods.In summary,more attention should be given to Cd contamination in this study areas,and there existed a significant positive correlation between AVS and the bio-available form of Cu in sediment,which indicated that AVS could effectively restrain the biological toxicity of Cu.However,the negative correlation between CRS and the bio-available form of Pb was notable,indicating that the increase of Pb bio-availability is not conducive to the formation of CRS.