Hygroscopicity of particles generated from photooxidation of α-pinene under diferent oxidation conditions in the presence of sulfate seed aerosols

Smog chamber experiments were conducted to investigate the hygroscopicity of particles generated from photooxidation of α-pinene/NOx with diferent sulfate seed aerosols or oxidation conditions. Hygroscopicity of particles was measured by a tandem diferential mobility analyzer(TDMA) in terms of hygroscopic growth factor(Gf), with a relative humidity of 85%. With sulfate seed aerosols present, Gf of the aerosols decreased very fast before notable secondary organic aerosols(SOA) formation was observed, indicating a heterogeneous process between inorganic seeds and organic products might take place as soon as oxidation begins, rather than only happening after gas-aerosol partition of organic products starts. The final SOA-coated sulfate particles had similar or lower Gf than seed-free SOA. The hygroscopicity of the final particles was not dependent on the thickness but on the hygroscopicity properties of the SOA, which were influenced by the initial sulfate seed particles. In the two designed aging processes, Gf of the particles increased more significantly with introduction of OH radical than with ozone. However, the hygroscopicity of SOA was very low even after a long time of aging, implying that either SOA aging in the chamber was very slow or the Gf of SOA did not change significantly in aging. Using an aerosol composition speciation monitor(ACSM) and matrix factorization(PMF) method, two factors for the components of SOA were identified, but the correlation between SOA hygroscopicity and the proportion of the more highly oxidized factor could be either positive or negative depending on the speciation of seed aerosols present.     

Effect of illumination intensity and light application time on secondary organic aerosol formation from the photooxidation of α-pinene

Secondary organic aerosol (SOA) formation from hydroxyl radical (OH.) initiated photooxidation of α-pinene was investigated in a home-made smog chamber. The size distribution of SOA particles was measured using aerodynamic particle sizer spectrometer. The effects of illumination intensity and light application time on SOA formation for α-pinene were evaluated. Experimental results show that the concentration of SOA particles increased significantly with an increasing of illumination intensity, and the light...     

白马泉风景区夏季大气PM2.5中二次有机物的初步研究

实验选择2010年7月于雅安市白马泉风景区常绿阔叶林内采集PM2.5样本,并对样本进行甲醇提取、三甲硅醚衍生化及GC/MS分析,探讨研究区域内气溶胶中异戊二烯氧化产物、α-/β-蒎烯氧化产物、小分子羧酸(苹果酸、2-羟基戊二酸)的浓度与昼夜变化趋势,并结合大气污染气体(SO2、NOx、O3)和环境气候条件(风速、温度、湿度等)对其浓度的影响进行讨论.结果表明,24 h PM2.5样本中,2-甲基丁四醇、异丁烯三醇、2-甲基甘油酸的浓度分别为63.3、45.0、4.4 ng.m-3;降蒎酸、3-羟基戊二酸、3-羟基-1,2,3-丁三酸的浓度分别为4.1、5.0、5.3 ng.m-3.除降蒎酸外,此次研究的其他二次有机气溶胶组分均呈现昼高夜低.白马泉风景区聚集了较高浓度的天然源二次有机物与当地亚热带繁茂的植被、湿热气候、沟谷型地貌及大气污染状况等诸多环境因素有关.