Distribution of heavy metals in urban soils - a case study of Danang-Hoian Area (Vietnam)

This work is part of a research study which is intended to study the degree of anthropogenic influences of the trace metal distribution of soils from Danang-Hoian (Vietnam). Cu, Ni, Zn and Zr show significant effetcs in most of the cultivated soil categories, espeically in the industrial soils. Extremely high levels of Pb (up to 742 mu g/g) are observed in the industrial soil category, which shows an enrichment factor 114 as compared to rural soils. Cd shows only a relative local enrichment wiht the maximum level of 4.6 mu g/g in urban soils. Sequential extraction was performeed in selected samples tp evaluate the geochemical trace metals. The result indicates that Zn and Cr are mainly found in the crystal and amorphous Fe oxide bounded forms. The contents of Cr in these fractions comprise more than 94% of total extractable Cr. In the case of Zn, 85% of total extractable Zn is in fractins F-V and F-VI. Cu is mainly found in the organic fraction at an average of 39.3% of total extractable content. On the other hand heavy metal contents show an increasing tendency in the fine fraction (silt and clay).