贵州中部山区煤矸石堆场周边污染水稻土重金属的释放特征

通过对贵州中部山区煤矸石堆场周边污染的水稻土及上覆水进行调查与采样分析,探讨污染水稻土有效态重金属(Cr、Cu、Zn、As、Cd、Hg和Pb)含量的变化及其释放特征。研究结果表明:不同程度污染水稻土中Cd、As和Hg的含量及部分水稻土中的Cu含量超过了土壤环境质量二级标准,随着水稻土污染程度的增加,土壤有效态Cd的含量出现明显的增加,中度污染水稻土和重度污染水稻土有效态Cd的平均含量分别比轻度污染水稻土增加了1.30、2.60倍;在水稻生长期间(6~8月),污染稻田上覆水中均出现Cd的超标,中度污染稻田和重度污染稻田上覆水Cd的平均浓度(三次采样)分别比轻度污染稻田的上覆水高11.3%和27.3%。污染水稻土淹水1~30d期间,上覆水Cd的浓度出现不断地增加,淹水20d后中度及重度污染水稻土上覆水Cd均出现超标。因此,煤矸石堆场周边污染稻田排水的Cd会产生明显的二次污染。

Release Characteristics of Heavy Metals from Polluted Paddy Soil around a Gangue Field in Moutain Areas of Central Guizhou Province, China

Paddy soil and overlying water around a coal gangue field in a mountain area of central Guizhou Province, China were sampled and analyzed to explore the bioavailability of heavy metals (chromium, copper, zinc, arsenic, cadmium, mercury and lead) and their release potentialfrom the soils. Results show that concentrations of cadmium, arsenic, mercury and some samples of copper in the polluted paddy soil exceed the Second Level of National Soil Environment Quality Standard.Content of labile cadmium increases obviously with increasing pollution degree of paddy soil. Labile Cd contents in paddy soils with intermediate and severe level of pollution increase 1.30 and 2.60 times of those with light level of pollution, respectively. During the period of rice growth (from June to August), the average concentrations (triple sampling) of cadmium in water samples overlying intermediately and severely polluted paddy soil are 11.3% and 27.3% higher than those of lightly polluted paddy soil, respectively. In polluted paddy soil flooding experiment for one to thirty days, the concentration of cadmium in the overlying water increased continually. After first 20 days of the experiment time, cadmium concentrations in water samples overlying intermediately and severely polluted paddy soil exceed the standard. It can be concluded that paddy soil affected by coal gangue effluent may cause cadmium pollution obviously.