The Significance of Heavy Metal and Organic Micropollutants in Soils.

Abstract

The southeastern region of Ireland, representing 22% of the land area of the country, has been systematically sampled. Soils have been analysed for a range of heavy metals and persistent organics. These soils have now been archived and are available for future analyses as required. Analyses conducted to date, the results of which are discussed here, are for soil parameters pH and organic matter, for major components, aluminum, iron, and manganese, for trace elements (heavy metals) arsenic, cadmium, chromium, cobalt, copper, lead, mercury, nickel, selenium and zinc and for organics, hexachlorobenzene, hexachloro-cyclohexanes, and for DDT and its metabolites. Other organics, polychlorinated biphenyls and polycyclic aromatic hydrocarbons, were examined in a proportion of soils. Results have been statistically analysed and frequency distributions have been calculated. Geographic distributions have also been plotted and localized concentrations have been found for most elements. Geochemical factors are considered to be largely responsible for most of these localized concentrations. Aerial deposition of lead and selenium was also indicated. Historic usage of DDT and g - HCH was detected in soils with different land uses. Overall, little serious contamination of soils, especially that caused by man, by toxic elements was evident. However, as many as 21% of soils breached the provisions of the EU Sewage Sludge Directive for heavy metals in soil.