污泥施入黄土后重金属Cu、Zn、Cd的淋滤迁移

Leaching and migration of Cu,Zn,Cd from sludge applied into loess

污泥土地利用是目前国内外污泥处置的主要方式和鼓励方向,在中国西北黄土地区更有前景和意义。污泥富含有机质和营养元素可弥补黄土的贫瘠缺陷,改善黄土肥力、增加植物产量。污泥施入黄土后,灌溉水对污泥重金属的淋滤迁移和污染风险是值得研究的课题之一。研究旨在了解重金属Cu、Zn、Cd在黄土层中的淋滤迁移特征,为黄土地区污泥的土地利用及重金属污染控制提供实验依据。实验选择污泥中含量或毒性大的Cu、Zn、Cd 3种重金属作为研究对象,通过室内模拟土柱对表层堆肥污泥中2种源强的重金属进行1年灌溉用水量的淋滤对比实验,测定淋滤前后土柱中和渗出液的Cu、Zn、Cd总量、有机质及p H值,以期分析重金属在黄土中的淋滤、迁移特征。结果表明,淋滤作用可使堆肥污泥Cu、Zn、Cd发生少量迁移并富集于土柱中、上部,大部分或绝大部分重金属仍滞留于耕作层(0~20 cm);淋滤使堆肥污泥Cd与Cu向下迁移约30 cm,Zn向下迁移约20 cm;渗出液呈弱碱性,其中Cu、Zn、Cd 3种重金属的浓度较入渗水均有增多,但随渗出液从黄土柱中溶出的重金属量极少。实验表明,耕作层重金属源强对Cu、Zn、Cd在土柱剖面中的淋滤、迁移和滞留作用以及溶出量均有不同程度的影响,堆肥污泥土地利用可以明显改善黄土肥力,灌溉对耕作层污泥有机质的淋滤损失量较小。并得出,堆肥污泥在黄土地区的土地利用是可行的。

Sludge land application is now one of major approaches for disposing urban sewage sludge at home and abroad. It has a bright promising and meaning in China's northwest loess region. Sludge is rich in organic matters and nutrient elements which can make up the barren loess defects,such as improving the fertility of loess,increasing the yield of plants. After the sludge adding into the loess,the risk of irrigation water on the leaching of heavy metals in sludge is one of the subjects to worth studying. The experiment was aimed at studying the leaching migration characteristics of Cu,Zn,Cd in soil,and providing experimental basis for land use to control heavy metal pollution in loess area. Under simulating an annual irrigation water leaching condition,the experiment choosed different sources of Cu,Zn,Cd to study the characteristics of leaching and migration after the sludge applied into the loess through interior surface soil column. In order to analyze the leaching migration characteristics of heavy metals by measuring the leaching of the total amount of Cu,Zn,Cd,organic matter and p H value before and after soil column. The results showed that a little Cu,Zn,Cd which are in the composted sludge,migrate and enrich in the upper soil column by leaching,while most of heavy metals are still stranded in the plow layer( 0 ~ 20 cm); Cd,Cu migrate downward about 30 cm,and Zn about 20 cm. All the concentrations of Cu,Zn,Cd increase in the weakly alkaline exudates,but little heavy metals leaching from the loess column.Experimental results show that the heavy metal source which is in the plow layer has different degrees of impacts on Cu,Zn,Cd leaching,migration,retention and dissolution in the soil column. Composted sewage sludge with land utilization can significantly improve the loess soil fertility,and irrigation has little effect on losing the organic matters in the sludge layer. And it is concluded that the compost sludge is feasible to apply to the loess areas.