Chlorination rates in forest soils - the importance of environmental factors

Transformation of chloride (Cl-) to organic chlorine (Clorg) occurs naturally in soil but it is poorly understood how and why transformation rates vary among environments. Even though formation of Clorg has been known for several decades, there are still few measurements of chlorination rates in soils. In the present study we compare organic matter (OM) chlorination rates, measured by 36Cl tracer experiments, in soils from eleven different locations. This comparison provides information on chlorination rates from different sites and gives an indication about how various environmental factors effect chlorination. A strong correlation was seen with environmental variables such as soil OM content and Cl- concentration and forest soil chlorination rates. Data presented support the hypothesis that OM levels give the framework for the soil chlorine cycling and that chlorination in more organic soils over time leads to a larger Clorg pool and in turn to a high internal supply of Cl- upon dechlorination. This can explain why soil Cl- locally can be more closely related to soil OM content and the amount organically bound chlorine than to Cl- deposition.