Single particle analysis of amines in ambient aerosol in Shanghai

An aerosol time-of-flight mass spectrometer was deployed in urban Shanghai to analyse amine-containing particles during two separate sampling periods, 1-9 August 2007 and 22-27 December 2009. Amine-containing particles are identified by a mass spectrometric marker at m/z 86 [NCH2(C2H5)(2)(+)] and classified into six major particle types to explore their possible origins. The number fraction of amine-containing particles in winter was much higher than in summer (23.4 v. 4.4 %), which can be explained by preferred gas-to-particle partitioning of gaseous amines at lower temperatures. Mass spectrometric patterns show the strong acidity of particles collected in December 2009, suggesting the acid-base reaction pathway might also contribute to the high concentration of amine aerosol in winter. Two fog episodes and two after-rain episodes of amine-containing particle bursts were observed in August 2007. Tightly correlated number fractions of sulfate-and amine-containing particles in all these episodes reveal that high relative humidity greatly enhances particulate amine formation based on acid-base reaction and subsequent particle growth. Our observations suggest that amines may account for significant parts of secondary organic mass in heavily polluted areas.

一台气溶胶质谱飞行时间分析仪被部署在上海市区，用于在两个不同的采样时段（2007年8月1日 - 9日和2009年12月22日 - 27日）分析含胺颗粒。含胺颗粒通过质荷比为86的质谱标记物[NCH₂(C₂H₅)₂(⁺)]来识别，并被分为六种主要的颗粒类型以探究其可能的来源。冬季含胺颗粒的数量分数比夏季高得多（23.4%对4.4%），这可以通过气态胺在较低温度下更倾向于气 - 粒分配来解释。质谱图显示2009年12月采集的颗粒具有强酸性，这表明酸碱反应途径可能也导致了冬季胺气溶胶的高浓度。在2007年8月观察到两次雾天事件和两次雨后含胺颗粒爆发事件。在所有这些事件中，含硫酸盐颗粒和含胺颗粒的数量分数紧密相关，这表明高相对湿度极大地促进了基于酸碱反应的颗粒状胺的形成以及随后的颗粒增长。我们的观察结果表明，在重污染地区，胺可能占二次有机物质的很大一部分。