酸性矿石废水短期污染对水稻土的影响

以受酸性矿石废水(ARD)污染1年的水稻田为研究对象,根据“ARD–土壤–水稻”体系中Cu、Cd、Pb和Zn等重金属含量,评价污染风险,分析ARD初期污染土壤中重金属的迁移特性;并分析土壤酸化潜力、理化性质和土壤脱氢酶含量,研究其与土壤重金属间的关系,探讨土壤污染特征,为酸性矿石废水(ARD)短期污染土壤的治理提供依据。结果表明:ARD的p H在2~3,其Cu和Cd分别超过国家V类水标准8.53倍和13倍。受ARD污染1年后,土壤中已有不同程度的Cu的富集,其中污染最严重的污1土壤中Cu(64.0 mg/kg)均超过国家二级标准(50.0 mg/kg),但污染土壤上水稻中的重金属大部分富集在根中,稻米中的重金属均远低于国家食品卫生标准。ARD污染也造成不同程度的土壤酸化和功能衰减,污1样地酸化和功能衰减最严重,其土壤p H和净产酸量(ANG)分别为3.5和H2SO4 12.4 kg/t,土壤脱氢酶活性已降为TBF 0.002 mg/(kg干土?24h)。此外,土壤中重金属含量和土壤酸化及土壤其他理化性质有一定关系,如土壤中总Cu和有效态Cu均和土壤中p H、NAGPH、Fe和SO42–极显著相关(P0.01),而土壤中Cu和Cd均和有效硅和电导率极显著相关(P0.01)。

Response of Paddy Soil Polluted by Acid Rock Drainage for a Short Time

To provide bases for paddy soil restoration polluted suddenly by acid rock drainage(ARD), a field investigation were carried out in a paddy soil polluted by ARD for about 1 year in Rongshui, Guangxi. The soil characteristics including acidification, fertility parameters, activity of dehydrogenase and the accumulation of Cu, Cd, Pb and Zn in the ARD-soil-plant systems were monitored, and the relationships among these properties were explored to find the pollution characteristics. The results showed that pH of ARD was 2 – 3, while Cu and Cd in ARD were even reached 8.53 and 13 times of the standard V class of national water standard. There was different Cu accumulation in the polluted soils, and the pollution in site 1 was most seriously, as Cu (64.0 mg/kg) in the soils were all exceeded the II class of national soil standard (50 mg/kg). While, the heavy metals absorbed by rice were mostly accumulated in roots, and the metals in grains were lower than the National Food & Health Standard. Varying degrees of acidification and degradation of soil function were also found in polluted soils. For example, pH and the net acid generation (NAG) in site 1 was 3.5 and H2SO4 11.27 kg/t respectively, while dehydrogenase in the soil was as low as TBF 0.002 mg/kgsoil?24h.The contents of total Cu and available Cu were both significantly correlated to pH, NAG-pH, Fe and SO42– in the soils (P<0.01). Moreover, the available Si and conductivity of the soils were both significantly correlated to Cu and Cd (P<0.01). These results might provide bases for the remediation of similar soils.