Contributions of deposited particles to pine needle polycyclic aromatic hydrocarbons

Abstract

The contributions of deposited particles (P) to polycyclic aromatic hydrocarbon (PAH) levels in pine (Cedrus deodar) needles sampled from the Dalian region were evaluated by washing off the particles from pine needle surfaces. P values ranged from 4.4 ± 2.2% for fluorene to 69.9 ± 4.0% for indeno(1,2,3-cd)pyrene, and positively correlated with the logarithm of octanol–air partition coefficients (log K_OA) of each PAH significantly. P and the total levels of 14 PAHs under study (∑PAHs), that ranged from 490 to 3241 ng g⁻¹ dw (dry weight) with median value of 1521 ng g⁻¹ dw, were high for traffic areas, and low for residential or park areas, implying the significant contributions of PAHs in both gas and particle phases emitted by vehicles. However, PAH profiles in pine needles were not significantly altered by the washing, due to the low fractions (2–5%) of the 5- and 6-ring PAHs in ∑PAHs. The high wind speed and frequently alternating wind directions in the Dalian spring could quicken the depuration processes of pine needle PAHs. Thus, the local meteorological conditions and source variations should be taken into account when using pine needles to implicate seasonal variations of atmospheric semi-volatile organic compounds.