CONTAMINANT ENRICHMENT AND PROPERTIES OF SOIL ADHERING TO SKIN

The adhesion of contaminated soil to skin has potentially important he alth implications, because the contaminants may ultimately be ingested or absorbed through the skin. Previous studies indicated that the adh ering soil is enriched in contaminant concentration relative to the or iginal soil because of the selective adhesion of finer particles. This study investigated this enrichment using 11 markedly different soils. Two sandy soils consistently gave very high contaminant enrichment ra tios, with a mean enrichment of 10-fold. The other soils all had enric hment ratios above unity. Scanning electron microscopy illustrated the potential for strong adhesion of very fine clay particles. The contam inant enrichment ratios were positively correlated to enrichments in s pecific surface area, organic matter content, and extractable Fe conte nt. Correlations to soil textural properties and detailed particle-siz e analysis of the adhering soil indicated that 50 to 100 mum may be a critical particle size: larger grains and aggregates do not adhere rea dily to skin. Because of this, enrichment ratios will vary positively with the proportion of particles in the whole soil that are greater th an 50 mum. A simple model is provided to predict enrichments using inf ormation from routine soil particle-size analysis.