Occurrence of C 10–C 13 polychlorinated n-alkanes in the atmosphere of the United Kingdom

Abstract

Short-chain (C 10–C 13) polychlorinated n-alkanes (PCAs) have been measured in the air in the United Kingdom at 2 week intervals over a period of 12 months. The mean concentration of PCAs over the sampling period was 320±320 pg m −3 (arithmetic mean±1 S.D.) with a geometric mean of 160 pg m −3. Hexa- and hepta-chlorinated dodecane congeners are the predominant PCA components in the UK atmosphere. Analyses of gas phase and particulate phase PCAs indicate that 95% of the PCA content of the atmosphere is in the gas phase. No seasonal trend or dependence on temperature was observed. The data can be divided into 2 significantly different ( P<0.01) populations: one group of incidences of lower concentrations of 150±110 pg m −3 and one of higher concentrations of 800±170 pg m −3. The incidences of elevated concentrations could not be related to increased air temperature or other meteorological factors on the time-scale employed and suggest that atmospheric PCA concentrations in the UK may be dominated by episodic incidences of advective transport of contaminated air masses and/or releases to the environment from regional primary point sources rather than by temperature-dependent transport processes. Levels of PCAs in the UK atmosphere are similar to values obtained at a semi-rural location in Canada and at least an order of magnitude higher than in the Canadian Arctic atmosphere. These data represent the first detailed study on the occurrence of PCAs in the atmosphere and show that PCAs can be a major component of the persistent organic pollutant burden of the atmosphere which has the potential of undergoing long-range atmospheric transport processes.