Characteristics And Sources Of Particulate Polycyclic Aromatic Hydrocarbon (PAHs) In The Yellow River Delta

To understand the pollution characteristics of particulate PAHs in the Yellow River Delta, a background site located in the North China Plain, a four seasons’observation from January2011to October2011was carried out using a Micro-orifice Uniform Deposit Impactor (MOUDI). Then we used gas chromatography/mass spectrometry (GC/MS) to analyze16kinds of optimal control PAHs and studied the concentration, size distribution, toxicity and sources of particulate PAHs in four seasons and haze condition. The main conclusions were as follows:(1) The average annual concentration of particulate PAHs in the YRD. The average annual concentration of particulate PAHs in the YRD.was18.95±16.51ng/m3. The average concentration of∑15PAHs in winter was the highest (34.17±2.19ng/m3), then was those in spring (19.09±1.00ng/m3) and autumn (9.71±0.68ng/m3), and those in summer was lowest (7.43±0.68ng/m3). The variation was caused by different meteorological conditions. Compared with the correlations between the PAHs concentration and meteorological conditions, the ambient temperature exerted a high negative correlation with the concentration of particulate PAHs. In addition, the PAHs concentration in hazy days was higher than that in normal days, especially in winter.(2) Fl、Phe、Flu and Pyr PAHs were main PAHs compositional pattern in four seasons and summer haze and winter haze. Although certain differences existed in the distribution patterns at different sampling periods, the main components of the PAHs in each season were Fl (5.93%-26.80%), Phe (8.17%-26.52%)、Flu (15.23%-27.12%) and Pyr (9.23%-16.31%). Fl、Phe、Flu and Pyr were also the dominant PAHs, representing81.38%、77.37%、50.40%and44.15%of the total PAHs in summer normal%summer hazy%winter normal and winter hazy conditions, respectively. The dominant individual PAHs (Fl、Phe、Flu and Pyr) in hazy days showed higher values compared to normal days, indicating that PAH concentrations were prone to increase in the YRD during hazy days.(3) The size distribution of particulate PAHs had no clear seasonal variation. In four seasons, the3-ring PAHs exhibited a bimodal distribution with the major peaks in the ranges of1.0-1.8μm (accumulation mode) and3.2-5.6μm (coarse mode). The4-6ring PAHs showed a nearly unimodal distribution with the highest peak in the range of1.0-1.8γμm (accumulation mode). In addition, the coarse fraction decreased for the4-ring PAHs and nearly disappeared for the5-and6-ring PAHs. The higher ring number PAHs were adsorbed onto the finer particles, whereas the more volatile PAHs were associated with the larger particles. In haze and normal days,3-ring PAHs exhibited a bimodal distribution. The size ranges of major peaks in the accumulation mode in summer normal (0.32-0.56μm) and winter normal (0.56-1.0μm) conditions were smaller than in summer hazy (1.0-1.8μm) and winter hazy (1.0-1.8γμm) conditions, respectively, whereas in the coarse mode, the size ranges of major peak did not have significant differences over the four sampling periods. The4-6ring PAHs showed almost unimodal distribution with the highest peak in the range of1.0-1.8γμm (the accumulation mode) over four sampling periods.(4) Toxic equivalent concentrations of particulate PAHs had clear seasonal variation, highest value occurred in haze day, especially in winter. The TEQ values of the sampling period varied from0.45to3.44ng/m3, with a mean value of1.84ng/m3. The higher TEQ value was found in winter, which was also more than seven times higher than that in summer. The BaPeq concentrations in winter normal and winter hazy conditions were5.7and10.0times higher than those in summer normal and summer haze, respectively, suggesting that PAHs have more carcinogenic and mutagenic effects in winter. The BaPeq concentrations were2.17and3.78times those in summer normal and winter normal conditions, respectively. The results indicated that PAHs on hazy days might.(5) PCA and diagnostic ratios (IcdP/(IcdP+BghiP)、BaA/(BaA+Chr) and BaP/BghiP) suggested that coal combustion and traffic emissions were the main PAH source in the four seasons and haze condition. In addition, back-trajectory calculations demonstrated that atmospheric PAHs were produced primarily by local anthropogenic sources.