Atmospheric fluxes of persistent semivolatile organic pollutants to a forest ecological system at the Swedish west coast and accumulation in spruce needles

Abstract

Measurements of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) have been carried out in a forested area at Lake Gårdsjön. The overall aim of this study was to identify the importance of atmospheric fluxes for the occurrence of persistent semivolatile organic compounds in a forest at the Swedish west coast and to measure the major pathways of circulation and accumulation of these contaminants within a terrestrial ecosystem. The sampling was undertaken in campaigns chosen to represent different seasons. The measurements carried out in 1991–94 were concentrated on the uptake of persistent organic pollutants (POPs) in spruce needles in relation to concentrations in air and amounts in deposition, while the measurements undertaken in 1995 also included sampling of throughfall, litterfall and run-off. The concentrations of PCBs and PAHs in the different compartments have been used to identify important reservoirs and to estimate the annual fluxes of these compounds. The results of measurements showed that atmospheric fluxes are important for the occurrence of PCBs and PAHs in forest at the Swedish west coast. A seasonal variation was found in the atmospheric concentrations, and the ambient temperature was important for PCBs in air. The amounts of PAHs and PCBs deposited to the Gårdsjö area (open field) were similar to those obtained during measurements at coastal- and sea-based sites at the Swedish west coast. Soot episodes at the Swedish west coast affected the deposition fluxes of POPs in the forest. There seemed to be both an accumulation and release of POPs in different compartments in this forest ecosystem. A greater deposition of POPs was found in the forest soil via throughfall compared with the open field deposition. An estimate of the fluxes of PAHs and PCBs in the catchment area in a forest showed that the soil is the main reservoir for POPs in this area.