PBDEs in European Background Soils: Levels and Factors Controlling Their Distribution

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Abstract
Surface soils (0−5 cm) from remote/rural woodland (coniferous and deciduous) and grassland locations on a latitudinal transect through the United Kingdom and Norway were analyzed for polybrominated diphenyl ethers (PBDEs). Concentrations ranged between 65 and 12 000 ∑ALLPBDE ng kg-1 dry weight. PBDE-47, -99, -100, -153, and -154the major constituents of the penta-BDE technical productdominated the average congener pattern of the soils. Indeed, the average congener composition and distribution measured in these European background soils closely matched that reported in the technical penta-BDE product. This is interpreted as evidence that transfer of the congeners present in penta-BDE-treated products from source−air−soil occurs with broadly similar efficiency, perhaps because there has been little weathering/degradation/alteration of the congener source pattern by processes operating during atmospheric transport or within the soil itself. BDE-183, a marker for the octa-BDE mix, was detected at concentrations ranging from -1). In most soils, it made a minor contribution to the ∑ALLPBDE concentration, but it was a major component in some samples from northern England. Forest soils tended to have higher concentrations than grasslands. Underlying the average soil composition, some differences in the congener pattern were observed. Notably, there was evidence of latitudinal fractionation, with the relative contribution of PBDE-47 and lighter congeners to the ∑PBDE increasing northwards (with increasing distance from source areas), while the proportion of PBDE-99 and heavier congeners decreased. Plots of concentration against percentage soil organic matter had different slopes for different congeners. Higher slopes were generally seen for the lighter PBDEs (e.g., PBDE-47), indicating that they have undergone some air−surface exchange (hopping), while the slopes of heavier congeners (e.g., PBDE-153) were close to zero, indicating that they are retained more effectively by soils after deposition.

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