Levels of extractable organohalogens in pine needles in China

Pine needles can accumulate organohalogens from the ambient air, which are, hence, able to serve as a biomonitor to evaluate the levels of organochlorinated contaminants in the atmospheric environment. Extractable organochlorine (EOCl), the most abundant of the extractable organohalogens (EOX) in environmental samples, has received much attention as a parameter for evaluation of total contamination levels of organochlorinated compounds (OCs). However, few data concerning EOCl in vegetation are available. In this study, we selected pine needles from 17 different areas in China as a sampling matrix to reflectthe regional distribution of OCs. EOX (EOX = EOCl + EOBr + EOI) were measured by instrument neutron activation analysis for their concentrations and distribution in pine needles. The concentrations of EOX were on the order of EOCl >> EOBr > EOI. About 5-38% of EOCl remained as sulfuric acid-resistant organochlorine (EPOCl). The relatively high concentrations of EPOCl in pine needles from remote areas suggested that EPOCl mainly originated from long-range atmospheric transport and contaminated soil. The relative proportions of the known organochlorines (such as HCHs, DDTs, aldrin, heptachlor, and chlordanes) to total EOCl and EPOCl were 0.3-5.2% and 1.4-19.8%, respectively, which implied that a major portion of the EPOCl measured in pine needles was unknown. The EPOX accumulation rates were preliminarily estimated under the natural condition, which suggested that the "young" needle accumulated EPOX more quickly than the "old" and more than 94% of EPOX was accumulated at the first year of pine needles.