Modeling persistent organic pollutant (POP) partitioning between tree bark and air and its application to spatial monitoring of atmospheric POPs in mainland China.

A mathematical model describing the bark/air partitioning of persistent organic pollutants (POPs) was established taking into consideration the accumulation processes of POPs from air into bark and compound-, species-, and site-specific air-to-bark accumulation factors. It allows the assessment of the concentrations of atmospheric POPs based on those recorded in tree bark. The spatial distribution of atmospheric POPs including 18 polycyclic aromatic hydrocarbons (Sigma18PAHs), 5 organic chlorinated pesticides (Sigma5OCPs), 10 polychlorinated biphenyls (Sigma10PCBs), and 17 brominated flame retardants (Sigma17BFRs) were investigated by analyzing 163 bark samples from 68 sites across mainland China. The atmospheric POPs were estimated to be 4.1-399 ng/m3 air, and 11.3-553, 4.5-130, and 0.9-624 pg/m3 air with geometric means of 71 ng/m3 air, and 99,26, and 25 pg/m3 airfor Sigma18PAHs, Sigma5OCPs, Sigma10PCBs, and Sigma17BFRs, respectively, based on those recorded in the tree barks of 5.1-1770, 0.05-12.9, 0.21-21.6, and 0.02-48.3 ng/g bark on dry weight basis, with geometric means of 295, 1.47, 3.12, and 2.79 ng/g bark. These results generally indicated that contamination by atmospheric POPs is more serious in eastern and mid China than that in western China.