PAHS IN SOILS - CONTEMPORARY UK DATA AND EVIDENCE FOR POTENTIAL CONTAMINATION PROBLEMS CAUSED BY EXPOSURE OF SAMPLES TO LABORATORY AIR

Archived (1951-1974) and contemporary (1993) surface soil samples coll ected from the same 46 locations widely distributed over the UK have b een analyzed for 12 polynuclear aromatic hydrocarbons (PAHs). Contempo rary soils were analyzed wet, ensuring that contamination, losses or a lteration of PAHs in the samples was minimal. Archived soils had been air-dried prior to storage. The Sigma PAH concentration of the contemp orary and archived soils range from approx 20 mu g kg(-1) to 7.4 mg kg (-1) (mean = 1.1 mg kg(-1)) and from approx. 160 mu g kg(-1) to 7.1 mg kg(-1) (mean = 2.1 mg kg(-1)), respectively. Comparison of the concen trations of PAHs in the archived and contemporary soils revealed no si gnificant trends for compounds heavier than benzanthracene. For some o f the lighter molecular weight compounds the concentrations were notab ly higher in the archived soils than in the contemporary soils. Two so ils of contrasting PAH content (0.08 and 9.8 mg kg(-1)) were used in a n experiment to compare the effects of air-drying on soils with relati vely low and high PAH concentrations. Subsamples of soil (10 g) were p laced into foil trays and exposed to laboratory air for up to 64 days. A clear increase in the concentration of the lighter molecular weight compounds (acenaphthene, fluorene, phenanthrene) occurred in both soi ls. No marked changes were observed for the heavier molecular weight P AH compounds. This experiment suggests that the higher concentrations of the lower molecular weight compounds measured in the archived soil samples is due to contamination during air drying. (C) 1997 Elsevier S cience B.V.