中国杭州夏季相对湿度对难溶性的亚微米级气溶胶演化的影响（英文）

Effect of relative humidity on non-refractory submicron aerosol evolution during summertime in Hangzhou, China

目的:研究湿度对气溶胶的影响。创新点:首次研究气溶胶中铵盐的存在形式,为研究相对湿度对大气中气溶胶的影响做了补充。方法:1.利用高分辨飞行时间气溶胶质谱仪采集的外场数据分析各组分时序浓度和粒径分布,并通过正矩阵因数分解模型进行来源解析。2.通过研究各种物质和解析的因子随湿度的变化,探讨湿度对气溶胶演化的影响。3.通过相关性处理探究铵在气溶胶中的存在形式。结论:在相对湿度大于60%时,湿祛除效应对有机物中的二次有机气溶胶及硫酸盐的影响较大,而硝酸盐受液相反应生成作用影响更大。湿度从低到高时,气溶胶中铵的存在形式由硫酸铵向硝酸铵过渡。

Relative humidity（RH） has a significant and complex effect on aerosols because of the aqueous phase process and gas-particle partition. The mass concentration and size distribution of organic aerosols, sulfate, nitrate, ammonium, and chloride were measured using high-resolution time-of-flight aerosol mass spectrometry（HR-To F-AMS）. These measurements were recorded from Aug. 5 to Sept. 23, 2016 in Binjiang District, Hangzhou, China, during which period more than 78% of the readings showed an RH over 60%, while the average temperature was 26 °C. Correlation analysis was applied to inorganic aerosol measurements while positive matrix factorization（PMF） was applied for source apportionment of organic aerosols（OA）. The pattern of fixation of ammonium in aerosols changed as the RH increased, suggesting that RH enhances nitrate participation in particles, while sulfate is scavenged by droplets. All species of non-refractory submicron particles（NR-PM_1） showed an increase in their peak size as the RH increased. Primary OA（POA） continuously accumulated as the RH increased. When RH60%, oxygenated OA（OOA） increased with increasing RH because of oxidation; semi-volatile OOA（SV-OOA） had a higher mass concentration during the daytime than at nighttime, indicating that the aqueous phase process and photochemistry synergistically affect the formation of oxygenated SV-OOA. When RH60%, there was a relatively slow decrease in OOA, dominated by the wet removal effect rather than oxidation. The degree of oxidation of OA decreased as RH increased; this can be explained by most of the OOA with higher hygroscopicity being removed as droplets.