渤海湾天津段表层沉积物重金属分布特征及其来源解析

年8月对渤海湾天津段沉积物进行采样分析,结果表明,渤海湾天津段表层沉积物中常量重金属质量分数为w(Fe)>w(Al)>w(Mn),微量重金属质量分数为w(Cr)>w(Zn)>w(Cu)>w(Pb)>w(Cd). 空间分布上,5种微量重金属在入海口海域和中部海域的质量分数较高. 利用I_geo(地累积指数)法评价重金属污染程度,结果显示,Cd、Cr和Zn的I_geo处于2级(中度污染),而Cu和Pb的污染较轻,其I_geo处于1级(未污染到中度污染). 多元统计结果表明:①渤海湾天津段表层沉积物中微量重金属质量分数与w(Fe)、w(Al)显著相关(P<0.01),说明微量重金属在海洋沉积过程中与常量重金属具有类似的地球化学行为；②在聚类分析中,所有重金属聚为一类,说明其具有相似的来源,都受陆源输入的影响；③所有重金属均在第一主成分上表现出较高正载荷,说明微量重金属与常量重金属具有相同的地球化学过程和环境行为. 根据重金属空间分布特征和多元统计结果,结合渤海湾的环流等情况可以推测,渤海湾天津段表层沉积物中微量重金属主要来源于环渤海地区入海河流的外源输入,并且大部分来源于工业源；其在渤海湾中的分布和迁移受到Fe和Al等常量重金属的影响. 

Distribution Characteristics and Source Identification of Heavy Metals in Surface Sediments of Bohai Bay near Tianjin

Sampling and analysis of the surface sediments in Bohai Bay near Tianjin in August 2011 showed that the concentrations of the major and trace metals in the surface sediments were present in the following decreasing order:Fe>Al>Mn and Cr>Zn>Cu>Pb>Cd. Regarding spatial distribution, the concentrations of the five trace heavy metals were determined to be high in the estuary sediments and in the middle of the bay. Using the geo-accumulation index (I_geo), the pollution levels of Cd, Cr and Zn were evaluated to be moderately polluted (Class 2 of I_geo), while the pollution levels for Cu and Pb were relatively low (Class 1 of I_geo). The results of multivariate statistics methods indicated that:1) The trace heavy metals were significantly correlated with the major metals Fe and Al (P<0.01); this result indicated that the trace metals and major metals had the same geochemical processes. 2) All metal elements were clustered together, which indicated that the metals originated from the same sources and were influenced by exogenous inputs. 3) All metals had high positive loadings in the first principal component, which indicated that the trace metals and the major metals had the same geochemical processes and environmental behaviors. According to the spatial distribution, multivariate statistical results and the circumfluence in Bohai Bay, it was concluded that the heavy metals in Bohai Bay (Tianjin) were mainly derived from the exogenous inputs of rivers in the areas around the bay. The input was generally from industrial sources. However, when the metals entered into Bohai Bay, Fe and Al significantly affected the distribution and transportation of the heavy metals.