Distribution characteristics of heavy metals in flood plains, farm fields and high lands in Lake Poyang region in China

Abstract

Aim : Rice plantations have greatly contributed to the population and economic growth of Lake Poyang Basin, where heavy metal contamination has become increasingly serious due to considerable non ferrous metal mining and processing enterprises. Based on the values of heavy metals of soils sampled from the Le'An River Basin area, the present study aimed to investigate the pollutants distribution characteristics in flood plains, farmlands and rice fields, identify the potential sources and assess the ecological risk. Methodology : After a full survey in the midstream area of the Le'An River, twenty-nine sampling stations were selected from the flood plains, farmlands and high lands, and analyzed using a sequential chemical extraction method. Sediment quality values, pollution indexes and geoaccumulation indexes were combined with statistical analyses and were performed to evaluate the spatial characteristics of heavy metals, assess the ecosystem risks and identify the potential sources. Results : There was a clear spatial Evalnating the effect of mining activities distribution characteristic with a significant increasing trend from the high lands to the flood plains, where heavy metal concentrations were significantly higher than the corresponding background values, such as the levels of Cd and Cu at Station 6 and Station 18, respectively. Furthermore, the ratio of bioavailability metal chemical partition was over 50% of the total metals. Various assessments that employed different methods indicated that the degree of contamination in the flood plains was extreme, whereas the pollution in the rice plant fields was lower than that in the flood plains. Two sources of pollutants were revealed through statistical analysis, one that was explained by the mixed origin of industrial emissions and one that was related to terrigenous components. Interpretation : Anthropogenic activities such as domestic runoffs, mining processes, irrigation and petroleum industries maysignificantly contribute to the distribution of heavy metals.