Organic Contaminants in Welsh Soils:Polynuclear Aromatic Hydrocarbons

Soil samples from 49 locations in Wales have been analyzed for 14 polynuclear aromatic hydrocarbons (PAHs) by HPLC with UV and fluorescence detection to define the normal or typical range of PAHs in surface soils (0–5 cm). The ΣPAH (defined as the sum of 14 PAH compounds sought) values vary by over 3 orders of magnitude. In general, soils show a constant qualitative mixture of PAH components but marked differences in absolute values along the remote-rural-urban gradient. Soil organic matter content has some controlling influence over soil ΣPAH values, but other soil properties (percent clay, bulk density) do not. In general, soils naturally rich in organic matter, such as peat bogs or deciduous and coniferous woodland soils, contain higher ΣPAH concentrations. SIMCA pattern recognition studies have been used to examine patterns in the samples and the variables. Principal component analysis supported the classification of “remote/rural” and “urban” soil samples based on the pattern of PAH; the distinction between remote/rural and urban is made at 600 μg of ΣPAH kg-1. The data are discussed further in the context of factors controlling soil PAH patterns