Age dependence accumulation of organochlorine pesticides and PAHs in needles with different forest types, southeast Tibetan Plateau

In this study, organochlorine pesticides (OCPs) and polycyclic aromatic hydrocarbons (PAHs) in needle leaves with different ages were measured in three prevalent coniferous forests including spruce, fir and pinus in southeast Tibetan Plateau ('IP) to investigate accumulation behavior of persistent organic pollutants (POPs) during entire growth cycle of needles. The accumulation concentration of POPs was higher in pinus and fir needles than in spruce needles. Concentrations for most of OCPs significantly increased with needle ages, especially dichlorodiphenyltrichloroethane (DDT) and its metabolites showed more remarkable increasing trend than hexachiorocy-clohexane isomers (HCHs) and hexachlorobenzene (HCB) in the three tree species. However, age dependence accumulation of PAHs was not observed in most cases, possibly due to its easier degradation property and the influence by dramatic change of ambient atmospheric concentration of PAHs. The lipid normalized concentrations in needles exhibited similar accumulation pattern with that of dry weight basis. The controlling factors for concentration variation in needles were identified using multiple linear regression. The suitability of these needle species acting as potential passive sampler for atmospheric POPs was evaluated. The different-age needles could reflect atmospheric OCP concentrations in the past long-term trend. Findings of this study provide guidance in use of needle as passive samples for the background monitoring of the atmospheric contamination at remote and poorly accessible locations such as the TP. (C) 2020 Elsevier B.V. All rights reserved.