A survey on polycyclic aromatic hydrocarbon concentrations in soil in Chiang-Mai, Thailand

Soil samples were collected at 30 sampling sites along roadsides in the cit y of Chiang-Mai, Thailand, in February 1996, and concentrations of 16 polyc yclic aromatic hydrocarbons (PAHs) were determined. The distribution of PAH concentration in the soil samples was almost lognormal for all PAHs. Conce ntrations of pyrene (Py) and fluoranthene (Fluor) were the highest, followe d by those of benzo[ghi]perylene and coronene (Cor). Since PAH concentratio ns were highest on the roadside where the traffic density was high, vehicle s were the main determinants of PAH concentration in soil in Chiang-Mai. Si gnificant correlations among PAH concentrations were found for almost all P AHs. PAH profiles in the air were different from those in the soil. For exa mple, relative benzo[a]pyrene (BaP) concentration in the soil was significa ntly lower than that in the air. Relative concentrations of Fluor, Py, chry sene, and Cor in the soil were considerably higher than those in the air, d ue presumably to their difference in photochemical reactivities and in sour ces. The sampling of soil has advantages relative to that of air: I) collec tion of soil is easy; 2) it needs no special equipment and electricity; 3) it takes little time; and 4) it can be collected anywhere. Therefore, PAH a nalysis in soil was useful as a proxy-screening tool for air pollution leve ls with consideration of compositional differences between soil and air sam ples. (C) 1999 Elsevier Science Ltd.