SOURCES AND FATE OF IODINE IN THE ENVIRONMENT

As iodine is an essential element for humans, there is considerable interest in its environmental geochemistry. It is unique amongst the elements in that most iodine in the terrestrial environment does not derive from normal weathering of crustal rocks but derives through volatilisation from the oceans, which represent the major reservoir of iodine on the Earth. As a result of this major source of environmental iodine, soils in coastal regions are strongly enriched in iodine, while those far removed from marine influence generally have low iodine contents. The strong maritime influence on the British Isles is reflected in the relatively high iodine contents of soils in the western coastal regions, generally reflecting the predominant south-westerly winds, with decreasing concentrations on moving inland. While this general pattern holds for most of the UK in the western part of East Anglia, England, a region with a “continental-like” climate and little maritime influence, soil iodine contents range up to 80 µg kg^-1, with a geometric mean of 6 µg kg^-1, considerably higher than might have been expected. In this case a local source of iodine has a marked effect on its distribution in soils.