The biogeochemistry of chlorine in soil
Gunilla Oberg
Department of Thematic Studies, Campus Norrrköping, Linköpings universitet
 

The past decade of research has revealed that chloride participates in a complex biogeochemical cycle involving formation, mineralization, leaching and volatilization of organic chlorine compounds. As a matter of fact the amount of organic chlorine in soil is in the same order of magnitude as the amount of organic phosphorus, which makes chlorine the sixth most common element in soil organic matter. It is a wide-spread notion that chlorinated compounds solely originate from anthropogenic sources. A large number of environmental pollutants are with no doubt chlorinated, but it is also true that a large number of chlorinated compounds are formed through natural processes. Some of the naturally formed compounds are recalcitrant but some are easily degraded. In addition to a formation of specific compound by specific organism it is quite clear that an unspecific chlorination of organic matter takes place in soil and elsewhere. The underlying processes are still unknown but there are strong indications that an enzymatically induced formation of reactive chlorine takes place during degradation of organic matter, resulting in an oxidation and fragmentation of the organic matter and a simultaneous chlorination. The ability to produce enzymes that induce formation of reactive chlorine appears rather common among litter and wood degrading fungi. It has therefore been suggested that the ability to produce reactive chlorine is an overlooked process involved in the degradation of recalcitrant organic matter. There are also studies that suggest that abiotic processes are involved in the formation of chlorinated compound in soil.

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