Acid Rain Impact on Phytoavailability of Heavy Metals in Soils

Soil heavy metal contamination and acid rain effects on terrestrial ecosystems are two major environmental problems of wide concern for some countries. Acid rain leads to great releases of soil heavy metals to surrounding ecosystem due to complicated soil chemical processes, mostly cation exchange and partly dissolution of minerals. In this study, the effects of acid rain on the transfer and phytoavailability of heavy metals to crop in contaminated soil was evaluated. A pot experiment was conducted to compare plant mechanism in various pH of acid rain treatment. The soil samples were collected from the paddy field in the vicinity of Janghang smelter. The Brassica campestris ssp. Pekinensis (Chinese cabbage) was used in this experiment. Each pot including Chinese cabbages was exposed to three conditions of simulated acid rain (pH 3.0 / 4.5 / 5.6) for 42 days. The results showed that phytoavailability of heavy metals were strongly controlled by pH of acid rain and lower pH can elevate the plant uptake of heavy metals, except for Pb. This indicates that acid rain has an adverse effect on surrounding ecosystems.