Sources of Organic Halogens in Spruce Forest Soil

Abstract

It is known that large amounts of organic halogens are present in soil, but the relative contribution from different sources is unclear. The aim of the present study was to determine the storage of organic halogens in a spruce forest soil and the deposition by needle litterfall and to elucidate the relative contribution from needle litterfall in relation to other sources and sinks. Sampling was conducted in a small spruce forest area in Denmark. Soil samples were collected at six locations to a depth of 60 cm. Litterfall was collected in 15 sample collectors every third month during 1 year. Soil leachate was collected below the Bh horizon over two periods of 5 days at five locations distributed over the study site. Throughfall data was compiled from a previous study conducted at the same site and during the same period as the present study, and data concerning net formation in soil was estimated from previous studies at similar sites. The pool was 630 kg of Clorg ha-1, contribution from litterfall was 0.35 kg ha-1 yr-1, and loss by leaching was 0.63 kg of Clorg ha-1 yr-1 (mean values). The estimated contributions from throughfall and net formation within the soil were 0.38 and 0.36 kg of Clorg ha-1 yr-1, respectively. The results suggest that the pool in the investigated soil originates mainly from sources within the forest and that it increases with time.