THE DESIGN AND APPLICATION OF A NOVEL AUTOMATED SAMPLER FOR WET AND DRY DEPOSITION TO WATER SURFACES

A novel automated wet and dry deposition collector utilising a wet-surface surrogate for dry deposition sampling is described. This has been used at two sites in NW England to attempt to establish wet and dry deposition fluxes of a range of polycyclic aromatic hydrocarbons (PAH) to natural water surfaces in the UK. The sample collection and analytical procedures are described. The wet flux of SIGMAPAH (n = 13) for the winter period is more than double that for summer/autumn at both sites. The pattern of PAH in the seasonally-averaged wet deposition data set stayed constant between seasons at the Castleshaw site, but not at Esthwaite Water. Both wet and dry deposition are found to be important to the overall atmospheric input at each site. The total (wet plus dry) input rises from summer/autumn to winter: from 74 to 258 ng (SIGMAPAH) . m-2 . h-1 at Esthwaite; from 128 to 164 ng (SIGMAPAH) . m-2 . h-1 at Castleshaw. The proportion of the total flux of SIGMAPAH due to wet deposition doubles at Castleshaw from summer/autumn to winter but decreases at Esthwaite from 65 to 40%. Trends at the two sites may be explained by differences in the proximity of local point sources of PAH.