Polycyclic aromatic hydrocarbons in the atmosphere of Shanghai, China

Shanghai is the largest industrial and commercial city in China, and its air quality has been concerned for several years. However, scarce study had been made on the seasonal levels of atmospheric polycyclic aromatic hydrocarbons (PAHs), together with their gas-particle partitioning and potential emission sources. Based on an intensive sampling campaign at urban and suburban areas in Shanghai during four seasons of 2005-2006, this study presented the measurement of PAH concentrations in both particulate and gaseous phases, as well as seasonal and spatial variability. The results showed that the annual PAH levels (gas + particle) were 167 +/- 109 ng m(-3) at the urban site and 216 +/- 86.5 ngm(-3) at the suburban site. Gaseous PAHs (>70%) dominated the total PAH mass at both sites, while particulate PAHs contributed more than 90% of the toxic power according to benzo(a) pyreneequivalent carcinogenic parameter. Different seasonal trend of PAH concentrations was observed between the two sites, and it may be explained by complicated factors such as sampling heights, local/regional emission sources, and climatic conditions. The gas-particle partitioning of PAHs in all samples was calculated, and strong linear correlations between log K-p and log P-L(o) were observed, with shallower slopes (m(r)) at the suburban site than the urban one and in warm season than the cold months, indicating the different equilibrium conditions of PAHs in spatial and seasonal scales in Shanghai. The slope (m(r) = -0.96) and correlation coefficient (R-2 = 0.81) for four-ring PAHs were closest to theoretical equilibrium conditions among compounds with various aromatic rings. Finally, the potential PAH sources were estimated based on principal factor analysis with multiple linear regressions. Ground volatilization dominated the PAH pollutions at both sites, while vehicles and coal consumption were the other main emission sources, which totally contributed 32.0% (suburban) to 49.2% (urban) of PAH mass in Shanghai atmosphere. The effects of wood and biomass burning were also detected, but their contributions to PAHs were negligible.

上海是中国最大的工商业城市，其空气质量多年来一直备受关注。然而，对于大气多环芳烃（PAHs）的季节性水平及其气 - 粒分配和潜在排放源的研究却很少。基于2005 - 2006年四个季节在上海市区和郊区的密集采样活动，本研究对颗粒相和气相中的PAH浓度以及季节和空间变异性进行了测量。结果表明，市区站点的年PAH水平（气体 + 颗粒）为167 ± 109纳克/立方米，郊区站点为216 ± 86.5纳克/立方米。在两个站点，气态PAHs（>70%）在PAH总质量中占主导地位，而根据苯并（a）芘等效致癌参数，颗粒态PAHs贡献了超过90%的毒性效力。两个站点之间观察到PAH浓度的不同季节趋势，这可能由采样高度、本地/区域排放源和气候条件等复杂因素所解释。计算了所有样本中PAHs的气 - 粒分配，观察到log K - p和log P - L（o）之间存在强线性相关性，郊区站点的斜率（m（r））比市区站点更平缓，暖季比冷季更平缓，这表明上海在空间和季节尺度上PAHs的平衡条件不同。四环PAHs的斜率（m（r）= - 0.96）和相关系数（R² = 0.81）在具有不同芳环的化合物中最接近理论平衡条件。最后，基于主因子分析和多元线性回归对潜在的PAH来源进行了估算。地面挥发在两个站点的PAH污染中占主导地位，而车辆和煤炭消耗是其他主要排放源，它们在上海大气中对PAH质量的贡献率总计为32.0%（郊区）到49.2%（市区）。也检测到了木材和生物质燃烧的影响，但它们对PAHs的贡献可忽略不计。