PCDD/Fs accumulation in pine needles: variation with species and pine needle age.

Pine needles have been used for many decades as a cheap and convenient biosampler to monitor atmospheric levels of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs), collectively known as PCDD/Fs. However, it is unknown whether accumulation of PCDD/Fs varies according to pine tree species or pine needle age, which hampers the precise application of this biosampler. We collected 0.3-2.3-year-old pine needles from four different species of pine at three sites in Hangzhou City, Zhejiang Province, China. The PCDD/Fs were quantitatively analyzed by gas chromatography high-resolution mass spectrometry. The results show that Pinus massoniana and Cedrus deodara absorbed more PCDD/Fs than Pinus thunbergii and Pinus parviflora at the same site. More cuticular wax and cuticular cell secretions in the pine needles from P. massoniana and C. deodara, as observed by scanning electron microscopy (SEM), might explain this discrepancy. The PCDD/Fs concentrations in 0.3-, 1.3-, and 2.3-year-old pine needles, indicated that concentrations increase with ascending age. This may be ascribed to the enhancement of lipids and cuticular waxes with age in pine needles as indicated by the lipid contents and morphologies observed by SEM. Our results may be useful for selecting the species and age of pine needles used for biosampling, especially for monitoring PCDD/Fs in large areas where the pine species growing in one place may differ from those in another place.