Factors influencing the national distribution of polycyclic aromatic hydrocarbons and polychlorinated biphenyls in British soils

The polycyclic aromatic hydrocarbons (PAHs) naphthalene, acenaphthylene, acenaphthene, fluorene, fluoranthene, pyrene, benzo[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, ideno[1,2,3,-cd]pyrene, dibenz[a,h]anthracene, benzo[g,h,i]perylene and the polychlorinated biphenyls (PCBs) 8, 18, 28, 29, 31, 52, 77, 101, 105, 114, 118, 123, 126, 128, 138, 141, 149, 153, 156, 157, 163, 169, 170, 171, 180, 183, 187, 189, 194, 199, 201, 206, and 209 were measured in ~200 rural soils across Great Britain (GB). Dominance of soil PAH profiles by heavier compounds (4-6 rings) provided initial evidence for the importance of source in governing soil PAH concentrations. No relationship was found between soil organic matter (SOM) and sum concentration of total and "heavy" PAHs, although there was a weak positive relationship with lighter compounds. A spatial statistical technique showed that highest soil PAH concentrations were usually found close to industrial/urban centers where presumably source intensity is highest. PCBs clustered into seven groups, five of which contained a single "dioxin like" PCB, one contained lighter congeners (2-4 chlorines), and one contained heavy congeners (5-10 chlorines). Linear regressions with SOM explained up to 24.3% of variation for the sum concentration of penta- to deca- congeners, but <1% for the lighter congener groups. No significant relationships were found with latitude. Spatial statistical techniques showed clusters of high soil PCB concentrations predominantly in west and south east GB, either associated with urbanized areas or on the West coast.