| Surface soil samples were collected at16stations across central Tibetan Plateau.The concentration and composition of polybrominated diphenyl ethers (PBDEs), soilorganic carbon, minerals and particle size distribution were determined to assess thelevel and identify the influence of soil on PBDEs accumulation. The soilconcentration of ΣPBDEs ranged from17.03-298.29ng/kg,dw, and the fraction ofBDEs from mono-to hexa-BDEs contributes approximately90%of the ΣPBDEs. Dueto cold condensation, the maximum value in the study area was found at thehighest-elevation site (T1), and meanwhile significant correlation between altitude andΣPBDEs was observed.There are42BDE congeners were detected in all, among which BDE-3was themost abundant congener, followed by BDE-2and BDE-1. A wide variety of othercongeners were also detected including BDE-209, with the average concentration1.25ng/kg,dw. It suggested the PBDEs in the study area were transported by longrange atmospheric transport (LRAT).Based on the characteristic composition of the technical BDEs and the similarproperties of BDE congeners, the BDEs may be tentatively classified. Here we use thecategorization in terms of the following three fractions: light (mono-, di-andtri-BDEs); intermediate (tetra-, penta-and hexa-BDEs); and heavy (hepta-, octa-,nona-and deca-BDEs). The light fraction and heavy fraction are negatively correlatedwith soil organic carbon (SOC), whereas the intermediate fraction is positivelycorrelated with it. This influence of clay minerals and grain size (<2μm) on eachfraction of BDEs is similar to that obtained for SOC, Note also that the coefficient ofdetermination (r2), is higher for the clays than for SOC. Although the complex of SOCand clays functions to adsorb PBDEs, the principal dynamic effect may be caused bythe clays because SOC may lose its dominant role if its content is less than the criticalvalue2%.Besides local sources, the physical and chemical properties of PBDEs alsoaffect their behaviors in soil. |
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