WEATHERING AND DISPERSAL OF POLYCHLORINATED-BIPHENYLS FROM A KNOWN SOURCE IN THE CANADIAN ARCTIC

The results of a PCB weathering experiment (i.e., losses from soil and changes in PCB composition from soil over time) at Cambridge Bay, Nor thwest Territories, in the Canadian Arctic are presented. Nine plots r epresenting three different general substrate types (dry barren, dry m oss, and wet grass) were treated with three different PCB Aroclor form ulations (1254, 1260, and a 1:1 mixture). Soil and plant samples were collected annually over a 5-year period and analyzed for individual PC B congeners. The results showed a high degree of variability between t reatments that was ascribed to the presence of vegetation as well as n on-homogenous PCB application and/or soil heterogeneity (e.g., biomass , organic carbon, and moisture content) within individual plots. Where readily interpretable data were available, the first-order rate const ant for the loss of PCBs from the substrate was calculated to be appro ximately 0.5 yr(-1) (t(1/2) = 1.1 yr) (range = 0.3-1.0 yr(-1) for indi vidual congeners). For the dry barren area, the rate of loss from soil of individual congeners was negatively correlated with the planar tot al surface area of the congener (or positively correlated with vapor p ressure). For a wet grass area or a dry moss area, the rate of loss wa s not correlated with any of the standard physical constants, suggesti ng that live and detrital vegetation may play a key role in the releas e and retention of PCBs. The estimated loss rates for the three plots may or may not be applicable to PCB-contaminated soils in general, whe re PCB volatility may be reduced by the presence of hydrocarbon-based carriers or influenced by other factors not considered in this study.