The distribution and origins of the hydrocarbon fraction of particulate material in the North Sea atmosphere

Abstract

The results of a fifteen month survey programme of hydrocarbons in the aerosol fraction of the North Sea atmosphere are presented. 98 high volume filter samples were analysed for saturated and polynuclear aromatic hydrocarbons (PAH) together with the uncharacterized complex material (UCM), using gas chromatography-mass spectrometry. The results indicate that the dominant source of hydrocarbons to the North Sea atmosphere is air which has recently passed over the UK. Concentrations in air from over continental Europe are generally higher but such air masses are relatively rare. Air whose recent history has been spent over the open sea shows the lowest hydrocarbon concentrations. Evidence of preferential loss of PAH over the sea is presented which has important consequences for flux calculations. Examination of carbon preference indices suggests that terrestrial sources dominate the aerosol with marine sources being relatively insignificant. Over the study period clear evidence was obtained of a large increase in PAH concentrations during the winter due to the increased combustion of fossil fuels during this period.