天津城市排污河道沉积物中重金属含量及分布特征

测定了天津大沽排污河沉积物和底部原状土壤中重金属及As、Fe、TN、TP和有机质的含量,采用相对富集系数、相关分析等方法,研究其重金属污染特征.结果表明,沉积物中重金属污染相当严重,底部原状土壤污染较小.Hg、Cd、Zn和Pb富集最严重,Cr、Ni和As富集水平较低,Hg、Cd、Zn和Pb相对富集系数(REF)在沉积物中分别为59.3、25.4、14.5和7.5,在原状土壤中分别为8.44、5.19、6.6和3.3.各沉积物采样点中重金属含量差别较大,变异系数(CV)在74.4%～110.8%之间,津涞公路断面和新城桥2个采样点污染最严重.沉积物的重金属含量与原状土壤的重金属含量之间没有相关性,沉积物中重金属元素之间的相关性也较差;但在底部原状土壤中,Hg、Cd、Zn和Pb之间的相关性强,其与OM和TP的相关性也较强,Cr、Ni和As与OM和TP的相关性差,Hg、Cd、Zn和Pb具有相似的环境地球化学行为,明显受到人类活动的影响.与天津市主要河流相比,大沽排污河沉积物中重金属污染最为严重.

Concentrations and Distribution of Heavy Metals in Urban Sewage Discharge Channel of Tianjin

Concentrations of metals, organic matter(OM), total nitrogen (TN) and total phosphorus (TP) were determined in sediment and soil samples collected from 15 selected sites along Dagu sewage discharge channel in Tianjin, China. Relative enrichment factors and correlation analysis were taken to study the distribution and pollution level of metals. The results show that pollution level is more serious in sediment than that in soil. Hg, Cd, Zn and Pb are more enriched while Cr, Ni and As are less enriched. Relative enrichment factors (REF) of Hg, Cd, Zn and Pb in sediment are 59.3, 25.4, 14.5 and 7.5, and that in soil are 8.44, 5.19, 6.6 and 3.3, respectively. The heavy metal concentrations greatly vary among different sampling sites, which is demonstrated by the fact that coefficient of variation (CV) varies from 74.4% to 110.8% in sediment. The highest enrichments of heavy metals are found in sampling site S4 and S12, which are affected by chemical industry wastewater. There is no significant correlation between metal concentrations in sediment and those in soil. The concentrations of heavy metals in sediment are not reciprocally correlated, either. However, significant correlations exist among many pollutants in soil. Hg, Cd, Zn and Pb are positively correlated with each other, at the same time they are positively correlated with OM, TN and TP, but Cr, Ni and As are poorly correlated with OM and TP, which suggests that Cd, Zn and Pb have similar environmental geochemical properties and are contaminated by anthropogenic impact. When compared with the main rivers in Tianjin, the enrichment of heavy metals in Dagu sewage discharge channel is relatively high.