Vapor Absorption of Semivolatile Organic Compounds to Atmospheric Particulate Matter

为了评估对流层中有机化合物的源、汇、化学和传输，必须确定几种人造和天然化合物在气态和凝聚态之间的分布。目前，关于大气中存在的半挥发性有机化合物的相分布的定量信息很少。化合物的蒸汽/颗粒分布对其在大气中的寿命及其所经历的化学反应有重要影响。直接测量大气中半挥发性化合物的相分布是一个具有挑战性的分析问题，需要进一步的研究。在这个项目中，半挥发性有机化合物（SOC）在气相和大气颗粒物之间的分布将通过现场和实验室实验来确定。本研究的目的是：(1)确定不同类别的半挥发性化合物的分配行为；(2)验证了有机碳液相蒸汽压在很大程度上控制对大气特定物质的吸附的假设；(3)研究有机碳分子形态对吸附的影响；(4)区分颗粒上的“可交换”和“不可交换”有机碳。在夏季和冬季使用由吸附剂捕集器支持的玻璃纤维过滤器收集大量空气样本。样品将通过色谱程序进行分析。蒸汽-颗粒分配系数将根据吸附剂捕集器和过滤器上的有机碳浓度和总悬浮颗粒浓度计算。现场和实验室的吸附热估计将作出。估计“不可交换”部分的SOC将通过分析过滤器后剥离与无SOC的空气。

To evaluate the sources, sinks, chemistry, and transport of organic compounds in the troposphere, one must define the distribution of several manmade and natural compounds between the gaseous and condensed phases. Currently there is little quantitative information available about the phase distribution of semivolatile organic compounds present in the atmosphere. The vapor/particle distribution of compounds has an important influence on their atmospheric lifetimes and the chemical reactions they undergo. Direct measurement of the phase distribution of semivolatile compounds in the atmosphere is a challenging analytical problem that requires additional research. In this project the distribution of semivolatile organic compounds (SOC) between the vapor phase and atmospheric particulate matter is to be determined through field and laboratory experiments. The objectives of this study are to: (1) determine the partitioning behavior of different classes of semi-volatile compounds; (2) test the hypothesis that the SOC liquid-phase vapor pressure largely controls adsorption to atmospheric particular matter; (3) investigate the influence of SOC molecular shape on adsorption; and (4) distinguish "exchangeable" and "non-exchangeable" SOC on particles. High volume air samples are to be collected in summer and winter using a glass fiber filter backed up by an adsorbent trap. Samples will be analyzed by chromatographic procedures. Vapor-particle partition coefficients are to be calculated from the SOC concentrations on the adsorbent trap and filter and the total suspended particle concentration. Field and laboratory estimates of heats of adsorption will be made. Estimates of the "non-exchangeable" fraction of SOC will be made by analyzing filters after stripping with SOC-free air.