珠江三角洲冲积平原土壤镉高含量区形成原因

Source and Cause of Regional Cd Enrichment in Alluvial Soils in the Pearl River Delta Plain

通过现场采样及室内分析方法,研究了珠江三角洲冲积平原土壤Cd高含量区形成的原因。调查发现,在西江和北江冲积平原存在Cd的高含量分布区。Cd高含量区仅分布于第四纪海陆交互相,从地表至深部含量变化不大,为珠江三角洲形成过程中,富含Cd的西江和北江冲积物质在珠江三角洲沉积而成。Cd高含量区空间分布特征明显,控制因素显著,属于由地质作用引起。这一结论与多数研究者认为是人为因素引起的具有根本差别。

The systemic geochemical survey for regional soil in the Pearl River Delta plain was carried out through sampling one or two samples per one square kilometer, one sample per 4 square kilometers for surface soils, and one sample per 16 square kilometers for deep soils with 1.5 m depth. The results presented that the concentration of Cd both in surface soils and deep soils were abundant in the alluvial plains of West river and North river in the Pearl river drainage system, and the vertical changes of Cd concentration was small. The areas with abundant Cd were mainly located at quarternary area with marine and continental sediments, and the concentration of Cd decreased in the order： transitional sediments〉marine sediment〉continental sediment. The variation degree of Cd concentrations in transitional sediments was bigger than that in continental sediment. High content of soil Cd was formed during delta development since sediment materials from West river and North river were rich in Cd. Regional high background of soil Cd was mainly caused by geological setting.