SPATIAL DISTRIBUTION, ORIGIN IDENTIFICATION AND POTENTIAL RISKS OF HEAVY METALS IN SUBURBAN FA LAND SOILS OF TIANJIN, CHINA

Accumulation of heavy metals in farmland soil threaten ecological environment and affect human health through food chain. 31 soil samples. 30 crops samples and 22 irrigation water samples were collected from a typical agricultural area, Xiqing district in western Tianjin, China, then the concentrations of 9 heavy metals were investigated. The heavy metals pollution and ecological risk were respectively evaluated by the Geoaccumulation Index and the Potential Ecological Risk Index methods. Multivariate statistical analysis is employed to analyse the correlations among these heavy metals and the potential sources of them. The results showed that the soils in the study area generally had low contents of heavy metals except that Zn and Cr were enriched in the soils near residential areas, highways, railways, or closed livestock farm. Potential ecological risk assessment indicated slight risk of soil pollution by heavy metals. Ordination results in indirect gradient analysis revealed the first three ordination axes respectively accounted for 49%, 23%, 12 /"0 of the total variance of the samples. Irrigation water significantly influenced the enrichment of As and Pb, while the distribution of Cr and. Ni can be attributed to soil parent material. The contents of Pb, Zn, Cu were affected by the emissions of nearby road traffic. V and As had similar distribution and were mainly related to the accumulation of historical pollutions from industrial.