Temporal and spatial variation of heavy metal contamination of farmland soil along the Xiaoqinling gold ore belt and its significance

Characteristic spatial and temporal variability of heavy metals accumulation in soils and quantitative variation trend forecast constitute the key to investigating the cumulative effects of heavy metal geochemistry as well as the early warning methods. Based on collecting research and monitoring data of the past 28 years, the authors analyzed comparative distribution characteristics and temporal-spatial variation of characteristic pollutants Hg, Pb, Cd, Cu in farmland soils of the Xiaoqinling gold orefield and, by means of two parameters (the average annual growth of the amount and the total rate of change), calculated quantitatively the accumulation rate of characteristic pollutants of heavy metals in farmland soils in the study area, with a discussion on its environmental significance. The results show that, from 1985 up till now, the average content of Hg, Pb, Cd in farmland soils of this area has continually increased, Cu content fluctuated, but the extremely seriously polluted area decreased or even disappeared.