Chloride is generally believed to be conservative with respect to water and is often used as atracer of water movement in hydrological research and biogeochemical modeling. However,the last decade of research has shown that naturally fanned organically bound chlorine isubiquitous in the environment. The turnover of such compounds has previously not been putin relation to the geochemical cycle of chloride.
The aim of this thesis was to examine and compare the distribution of organically bound chlorine and chloride in soil. The influence of central soil-forming factors, such as climate, ecosystems and topography were studied and special attention was paid to spatial distribution patterns. Samples were collected in southern Sweden and in the Anhui province in China. The former is situated in the temperate region and the latter in the subtropical region.
The results show that the storage of organic chlorine in the Swedish soils was 2-4 times larger than the chloride storage. This suggest that the storage of organic chlorine in forest soils with a moderate chloride deposition in the temperate region is of such size that even small changes in this storage are likely to have a considerable impact on the transport of chloride. In contrast, the size of the storage of organic chlorine in the Chinese soils was 2 times smaller than the storage of chloride. The storage is still of such size that it cannot be excluded thatchanges in this storage influence the transport of chloride.
It was also found that the concentration of both forms of chlorine varied among different types of ecosystems such as coniferous and deciduous forest soils. In addition, both forms of chlorine appear to vary seasonally with higher concentrations in the winter and lower concentrations in the summer. The spatial distribution pattem of organic chlorine followed that for organic matter in the Chinese forest soil whereas it followed the pattern of chloride in the study of Swedish forest soils.
In conclusion, the occurrence of organically bound chlorine in soil is influenced by factors such as climate, type of ecosystem and the topography. It is suggested that net-changes in the storage of organic chlorine are of importance for the transport of chloride, which implies that the biogeochemical cycle of chlorine should be addressed.
Linköping: Linköpings universitet , 2000. , 55 p.
2000-09-15, Sal Elysion, Hus-T, Universitetsområdet Valla, Linköping, 10:15 (Swedish)