Deciduous vegetation (Betula glandulosa) as a biomonitor of airborne PCB contamination from a local source in the Arctic

Abstract

Concentrations of polychlorinated biphenyls (PCBs) were measured in the new-year growth of dwarf birch (Betula glandulosa) before (2001–2002), during (2003–2004), and for six years after (2005–2010) the screening and containerization of PCB-contaminated soils (>50μg/g PCBs) at a remote Arctic radar site. During the remediation activities, ambient air PCB concentrations were measured using active air samplers for comparison to the passive samplers (dwarf birch). PCB concentrations measured by the active samplers reached a maximum of 0.037μg/m3 which was below the project criteria of 0.15μg/m3 indicating minimal source emissions. During the same time period, PCB concentrations in the dwarf birch (passive samplers) showed significant increases of 2–14 fold compared to the baseline data from previous years. The birch data also showed significant changes between monitoring events within the 2003 and 2004 sampling seasons (June to September) and decreases when ambient air concentrations were low, indicating the sensitivity of new-year growth to reflect net accumulation and ambient conditions at a temporal scale of approximately two weeks. The dwarf birch PCB concentrations remained elevated compared to baseline levels for two years after the remediation was completed. In the third year following remediation, concentrations decreased to below baseline levels reflecting the overall remediation and source removal at the site. Spatial variations observed in dwarf birch PCB concentrations are likely due to the influence of wind direction on contaminant dispersal and deposition.