Chemical composition and hygroscopic properties of secondary organic aerosol : Their impact on the atmospheric environment

将串联式差示迁移率分析仪(TDMA)系统组装成吸湿TDMA系统，用于测量大气颗粒物的吸湿特性。首次利用该体系测定了左旋葡聚糖、D-葡萄糖等纤维素热解产物以及4-羟基苯甲酸、丁香酸等木质素热解产物的生长因子。我们发现，左旋葡聚糖和葡萄糖是非常吸湿性很强的化合物，因此可以作为大气中的云凝结核。在东京市区进行的撞击行动中，使用了TDMA和H-TDMA系统，并使用了高容量空气样品、PM1撞击器、环形喷管取样系统等多种仪器，分析了样品中的低分子二元酸、酮羧酸和二羧基，以及半挥发性醛、水溶性有机碳、元素碳和有机碳…更多的n(OC)。1.草酸等水溶性二元酸及其相关化合物的浓度从清晨到中午呈上升趋势，到傍晚呈下降趋势。个别物种的峰值幅度是夜间相对浓度的3-15倍，表明次生有机气溶胶的光化学产生。2.有机碳和总有机碳也表现出日变化，中午前后出现最大值。有机碳和总有机碳中二元酸的相对丰度也在白天出现最大值。这表明，在光化学过程中，城市大气中有选择性地产生了极性有机化合物。3.在东京测量了100 nm和200 nm两种粒径模式下气溶胶的吸湿性。细颗粒物的吸湿生长因子从早上到中午增加，到傍晚进一步增加。这一发现与白天水溶性二元酸和WSOC浓度的增加是一致的。我们还发现，对于尺寸为200 nm的颗粒，这种吸湿生长比对于100 nm颗粒更为显著。颗粒物的这些物理性质可能与气溶胶的化学成分有关。有机气溶胶的光化学演化似乎伴随着水溶性有机气溶胶的光化学产生，即经过光化学老化的气溶胶可能在较大的颗粒中更富集。较少

Tandem differential mobility analyzer (TDMA) system was assembled and modified to hygroscopic TDMA, by which hygroscopic properties of atmospheric particles were measured. This system was first used to determine the growth factors of cellulose pyrolysis products such as levoglucosan and D-glucose, and lignin-pyrolysis products such as 4-hydroxybenzoic acid, syringic acid. We found that levoglucosan and glucose are very hygroscopic compounds and thus can act as cloud condensation nuclei in the atmosphere.TDMA and H-TDMA system has been used for size distributions and hygroscopic properties of aerosols during the IMPACT campaign conducted in urban Tokyo together with many instruments including High-volume air samples, PM1 impactor, annular denuder sampling system, etc. The samples were analyzed for low molecular weight dicarboxylic acids, ketocarboxylic acids and dicarborryls, as well as semi-volatile aldehydes, water-soluble organic carbon (WSOC), elemental carbon (EC) and organic carbo … More n (OC).1.Concentrations of oxalic acid and other water-soluble dicarboxylic acids as well as related compounds increased from early morning to noon and then decreased toward to the evening. The amplitudes of the peaks for individual species were 3-15 times relative lo nighttime concentrations, suggesting photochemical production of secondary organic aerosols.2.OC and WSOC also showed diurnal variation with maxima around noontime. The relative abundances of diacids over OC and WSOC also showed maxima in daytime. This suggests that polar organic compounds are selectively produced in urban atmosphere during photochemical episode.3.Hygroscopic properties of aerosols were measured in Tokyo at particle size mode of 100 nm and 200 nm. Hygroscopic growth factors for fine particles were found to increase from the morning to noontime and further increase toward the evening. This finding is consistent with the increased concentrations of water-soluble dicarboxylic acids and WSOC in daytime. We also found that this hygroscopic growth is more significant for 200 nm size particles than that for 100 nm particles. These physical properties of particles may be associated with the chemical composition of the aerosols. Photochemical production of water-soluble organic aerosols seemed to be followed by the photochemical evolution of organic aerosols, namely, photochemically aged aerosols may be more enriched in larger particles. Less