Introduction

Abstract

An understanding of the occurrence and availability of heavy metals and metalloids in soils is of major importance to environmental health, crop and livestock produc- tion, food and water quality and ecotoxicology. The concentrations of heavy metal (loid)s in soils can vary widely, even in uncontaminated soils. Marked differences in the geochemical composition of the rocks which form the parent materials of soils and variations in the intensity of soil-forming processes can result in wide ranges of total and available concentrations of most elements in soils, even in those unaffected by contamination. Nevertheless, contamination from many sources can often give rise to some very high concentrations of heavy metal(loid)s which can cause toxicity in soil organisms and susceptible plants, but this depends on the factors affecting the bioavailability of the elements.