农田生态系统中重金属的积累积循环

ACCUMULATION AND CIRCULATION OF HEAVY METALS IN THE ECOSYSTEM OF CULTIVATED FIELDS

本文通过对北京东郊高碑店地区污染农田的调查研究,探讨了重金属在农田生态系统中的积累和循环,计算出重金属在区域环境中的输入输出量,说明本区仍处于重金属积累状态,为防治农田环境污染,提出了停止施用污水处理厂的晾干污泥,减少灌溉污水中的重金属含量等保护性措施。

Through the investigation of the polluted cultivated field in the eastern suburbs of Beijing Gao Beidian area, accumulation and circulation of heavy metals in cultivated ecosystem have been researched, and the output and input of heavy metals have deen counted. The results are as follows.1.This area is still in the stats of heavy metals accumulation2.97%-99% of the total input amount of Hg and Cd comes from slu-dge. 92% of the total input amount of As comes from the irrigation sewage. Most of the input amount of Cu, Zn, Cr comes from the sludge, but it is also important that the amount (15-26%) comes from the sewage. Input amount of Pb, Zn from the rain and dust is more than that of the other eleme-nts. Output factors are plants and surface runoff. The output amount is mainly from leaves and stem. The output amount of surface runoff are much less than the total input amount.3.Input amount of the sludge is nearly equal to the accumulation of soil every year, especially Hg and Cd. In order to prevent further developing of polluted environment of cultivated fields, it is necessary that sludge is prohibit to be used.4.When sludge is forbidden to be used, it is available to irrigate the fields with sewage in which the heavy metal content is already decreased.