乌鲁木齐市典型城区大气PAHs气-粒分配特征

大气中PAHs的气-粒分配是影响其在大气中分布、迁移和转化的一个重要因素,于2011年12月—2012年12月在乌鲁木齐市天山区采集大气气相和颗粒相样品,对聚氨酯泡沫样品的气相和石英纤维膜的颗粒相(TSP)中的16种PAHs进行分析.结果表明:采样期间颗粒相和气相中ρ(∑₁₆PAHs)总和的年均值为(116.71±92.74) ng/m3,采暖期〔(173.16±84.26) ng/m3〕是非采暖期〔(39.46±16.19) ng/m3〕的4.4倍；采暖期颗粒相中ρ(∑₁₆PAHs)平均值为(40.60±3.03) ng/m3,气相为(134.46±13.05) ng/m3,2～3环PAHs主要存在于在气相中,4～6环PAHs主要存在于颗粒相中.在非采暖期,颗粒相ρ(∑₁₆PAHs)平均值为(25.37±3.21) ng/m3,气相为(14.95±1.06) ng/m3.采用吸附和吸收模型对PAHs的分配特征进行了研究,表明PAHs的lg K_p(K_p为分配系数)与lg P_L0(P_L0为过冷蒸汽压)线性关系显著,在采暖期斜率绝对值为0.34,说明PAHs的气-粒分配以吸收为主；在非采暖期的斜率绝对值为0.78,表明PAHs的气-粒分配受吸收和吸附共同作用.PAHs的lg K_p与lg K_oa(K_oa为正辛醇-大气分配系数)线性关系显著,在采暖期斜率为0.38,表明PAHs气-粒分配并未达到平衡；在非采暖期,斜率为1.22,表明PAHs气-粒分配接近平衡.研究显示,乌鲁木齐市城区大气PAHs气-粒分配在采暖期及非采暖期特征不同,应区别制订政策和管理措施. 

Gas-Particle Partitioning of Atmospheric Polycyclic Aromatic Hydrocarbons in the Urban Area of Urumqi City, China

The gas-particle distribution of polycyclic aromatic hydrocarbons(PAHs) has a great impact on the distribution and transformation of PAHs in the atmosphere. Investigating the gas-particle distribution characteristics of PAHs is helpful to predict PAHs tendency and provide a theoretical basis for related air pollution prevention and control. Gas-particle phase samples were collected at an urban site inTianshan District of Urumqi City from December 2011 to December 2012, and 16 types of PAHs were analyzed. The results showed that the sum of PAHs(∑₁₆PAHs) in the gas and particle phases was(116.71±92.74) ng/m3, in which(173.16±84.26) ng/m3was for the heating period and(39.46±16.1) ng/m3 was for the non-heating period. During the heating period, the concentrations of PAHs in the particle and gas phases were(40.60±3.03) ng/m3 and(134.46±13.05) ng/m3 respectively； 2-3 ring PAHs contributed in the gas phase and 4-6 ring PAHs contributed in the gas particle phase. During the non-heating period, the concentrations of PAHs in the particle and gas phases were(25.37±3.21) ng/m3 and(14.95±1.06) ng/m3 respectively. Linear correlations were observed between lg K_p and lg P_L0 during the two periods using adsorption and absorption model. During the heating period, the absolute value of slope was 0.34, which shows PAHs in the gas particle partitioning to absorption. The slope during the non-heating period was 0.78, which indicated the combination of adsorption and absorption. lg K_p and lg K_oa showed a good linear relationship； in the heating period, the slope was 0.38, showing that PAHs and gas particle partitioning did not reach equilibrium. In the non-heating period, the slope was 1.22, which showed that the PAHs gas particle distribution was close to equilibrium. The research showed that PAHs distribution in the gas-particle phase had different characteristics in the heating and non-heating periods in Urumqi City.