Atmospheric PCDD/F concentrations in 38 cities of China monitored with pine needles, a passive biosampler

Many studies have shown that pine needles are a good biomonitor for atmospheric concentrations of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). However, this biomonitor has not been tested in large areas, and the quantitative relationship between concentrations in pine needles and air has not been established. In the present study, we collected pine needles from 38 cities in China. The concentrations of 2,3,7,8-PCDD/Fs were measured by gas chromatography combined with high-resolution mass spectrometry. The total PCDD/F concentrations ranged from 5.4 to 330 pg/g dry weight of pine needles. The pine needles from cities located in central China and three major city agglomerations contained high concentrations of PCDD/Fs, while those from cities in the west and on the coast contained relatively low concentrations. Primary emission and diffusion processes were the main controls of the PCDD/F concentrations in pine needles. Homologue profiles of PCDD/Fs in pine needles were characterized by PCDFs/PCDDs >1 in the industrialized cities and <1 in unindustrialized cities. The congener patterns were dominated by 1,2,3,4,6,7,8-HpCDF and OCDD, indicating that combustion was the major source of the PCDD/Fs. By comparing the PCDD/F concentrations in the pine needles and those in air, we established a preliminary linear relationship between them. Finally, the concentrations in air of PCDD/Fs in the 38 cities of China could be predicted from this relationship.