Levels And Characteristics Of Polycyclic Aromatic Hydrocarbons In Pine Needles From Northeastern China

Polycyclic aromatic hydrocarbons (PAHs), a group of ubiquitous semivolatile organic compounds (SOCs), are mainly originated from incomplete combustion of fossil fuel and biomass. Due to possible human carcinogens, PAHs have become an issue of increasing concern in recent decades. Northeastern area is one of typical traditional industrial bases in China. Over the last century, increases in population and industry in the region have resulted in high consumption of fossil fuel. In addition, biomass burning is a traditional practice for heating and cooking in rural areas. Thus, it was expected that Northeastern area might suffer from severe PAH pollution. Pine is most widely distributed conifer in the world. Due to lipid-rich cuticle and pore structure of its surfaces, pine needles have a high affinity for SOCs and can be used as passive samplers to monitor regional contaminations and to identify point sources of SOCs. The PAH levels in pine needles from Northeastern area and Dalian were investigated, which is very important to understand the characters of PAH pollution in Northeastern China. In addition, contributions of deposited particle bound PAHs, relationships of PAH profiles and distribution between pine needle and soil samples and influence of pine needle's physiological properties on the capabilities of PAH accumulation were investigated.The levels and distribution of PAHs in Dalian pine (Cedrus deodar) needles were investigated. The strong turbulence and air exchange may facilitate air depuration effectively and also mitigate the diffusion of PAHs into the pine needles. Consequently, PAH concentrations were no statistically significant differences among the different sampling campaigns. The concentrations of PAHs in Dalian were comparable with that in other regions in the world. Pine needle PAH concentrations showed a major traffic areas - minor traffic -residential areas - city parks/island gradient. The profiles in all pine needle samples were dominated by 3- and 4-ring PAHs. The profiles of 4-ring PAHs decreased along the heavy traffic - minor roads - residential areas - city parks/island transect, whereas the franctions of 5- and 6-ring PAHs increased slightly among the four areas. The plots of selected PAH diagnostic ratios in the four sampling areas suggested that pine needle PAHs were mainly from traffic emission in the urban areas and coal/wood combustion in the suburban and rural areas.The contributions of deposited particles (P) to PAH levels in pine (Cedrus deodar) needles sampled from Dalian region were evaluated. The results showed that the average contributions of deposited particles (P) were (23.1±3.4)%, and positively correlated with logarithm of octanol/air partition coefficients (logK_OA) of each PAH significantly. P 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 ZPAHs.The concentrations and profiles of PAHs in soil and pine neddle samples were investigated.ΣPAHs in soil samples are higher than in pine needles from Dalian areas. Significant correlations were observed between logarithm of particle/gas partition coefficient, as well as logK_OA, and logarithm of soil PAH concentrations from atmosheirc particle deposition vs. washed pine needle PAH levels. Benzo(a)pyrene (BaP) was a good indicator for assessing the potential toxicity of PAHs. Toxic equivalent concentrations based on the toxic equivalency factor of BaP of most soil samples are higher than pine needles.The influences of the physiological properties on the accumulation of PAHs in pine (Cedrus deodar and Pinus thunbergii) needles were investigated. The lipid content is the principal factor influencing the PAH levels in different species of pine needles. Pine needles are prone to accumulate gas phase PAHs, such as 3-ring PAHs. There are no significant correlations between the levels of 5- and 6-ring PAHs and lipid contents for two species. For two species, the correlations between lipid contents and specific surface areas are different, which result in the contrary correlations between the PAH levels and specific surface areas for Cedrus deodar and Pinus thunbergii. Specific surface areas and stomata density affect the levels of 5- and 6-ring PAHs in pine needles significantly.The levels and distribution of PAHs in pine (Pinus thunbergii) needles from Northeastern area were investigated. Due to high combustion of coal for heating in autumn and winter, PAH levels in pine needle samples were statistically significant differences between heating and non-heating periods, whereas insignificant differences of the PAH composition profiles by ring size were observed. Pine needle PAHs were dominated by phenanthrene, naphthalene and fluoranthene. With the latitude increasing, pine needle PAH concentrations in major cities presented three peak values in Tieling, Fushun and Jilin City, respectivly. The results of diagnostic ratios indicated that pine needle PAHs in the study area were mainly from incomplete combustion of coal and/or biomass, and were affected by other emission sources, too. Significant correlations were observed between population densities and pine needle PAHs in major cities as well as the ratio of second gross domestic product (GDP) vs. total GDP. High traffic densities could lead to high XPAHs.