A study of the spatial distribution of PCBs in the UK atmosphere using pine needles

Past and current polychlorinated biphenyl (PCB) inputs to the environment, mainly in industrialized countries, continue to determine a global re-distribution of these contaminants. In order to better understand PCB transport and distribution phenomena, a number of large-scale distribution studies have been recently published in the literature. In this paper a nationwide survey of 28 pine needle samples taken across the UK is presented. Mean PCB concentrations of a number of latitudinal bands (transects) revealed the presence of a decreasing concentration gradient from southern England to northern Scotland of a factor of 7. The pine needle data also provide evidence to suggest: 1) that there has been a decrease in the PCB concentration of the atmosphere in the southern UK; and 2) there is a relationship between regional mean needle PCB concentrations and population densities. Calculated air concentrations from the pine needle results were compared with measured literature data of a similar area to test the possibility of using bioconcentration factors (BCF) based on n-octanol: air partition coefficients (Koa) to predict air-leaf equilibrium of semivolatile organic compounds. A more detailed analysis, in accordance with some literature data, has revealed that uncertainties arise when leaf-air uptake of molecules with high Koa values (Log Koa > 8–9) is modelled.