Influence of Ordovician uraniferous black shales on the trace element composition of soils and food crops, Korea

Abstract

This paper examines the influences of some Korean uraniferous black shales on the concentrations of selected toxic trace elements in soils and on the chemical composition of crop plants, and possible implications to human health. Geochemical surveys were undertaken along 23 river valleys in Korea underlain by black shales and oil shale. Sampling of rocks, soils and crop plants was carried out along transect lines within each valley. Samples were analysed for 26 elements by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES), and for U by Neutron Activation Analysis (NAA). The average trace element concentrations of Okchon uraniferous black shale in the Deog-Pyoung area were 6.3 μg/g Cd, 136 μg/g Mo and 8.6 μg/g Se, which are considered sufficient to raise environmental problems. Soils derived from Okchon uraniferous black shales tend to reflect the extreme geochemical composition of the bedrock, and trace element concentrations in crop plants are influenced by those of the soils. Cadmium is accumulated in tobacco plants with a maximum of 46 μg/g D.M. and lettuce contain amounts ranging up to 3.1 μg/g Cd and 0.5 μg/g Se. The elevated trace element concentrations in these plants may have deleterious effects on human health.