黄山PM_(10)中二元羧酸类化合物的季节变化特征及其来源

Seasonal Variation and Sources of Dicarboxylic Acids and Related Compounds in PM_(10) from Mt. Huangshan

为研究黄山大气PM_(10)中二元羧酸类化合物的季节变化特征,分别于2015年夏季、冬季在黄山山顶采集PM_(10)样品,并分析二元羧酸、酮羧酸和α-二羰基化合物.结果表明,无论在夏季还是冬季,草酸(HOOC—COOH,C_2)均是浓度最高的二元羧酸,其次是丙二酸(HOOC—CH_2—COOH,C_3)、丁二酸[HOOC—(CH_2)_2—COOH,C_4],这与其它高海拔地区的分子组成是相似的.大部分二元羧酸的浓度呈冬低夏高的季节变化特征,但是冬季己二酸(C_6)和邻苯二甲酸(Ph)的浓度约高于夏季的2倍,表明冬季黄山大气受周边地区所排放的人为污染物的影响更大.作为二元羧酸的重要前体物,乙二醛(Gly)与甲基乙二醛(mGly)的浓度呈冬高夏低的季节变化特征,表明夏季黄山气溶胶的氧化性比冬季强.主成分分析(PCA)结果表明,黄山冬季SOA主要来自人为源的长距离传输,而夏季SOA主要是当地生物源经二次氧化形成.气溶胶无机模型(AIM)的计算结果表明,黄山夏季的C_2主要是经酸催化反应二次形成的.

To identify the seasonal variation of dicarboxylic acids and related compounds in PM10 from Mt. Huangshan. PM10samples were collected during the summer and winter of 2015, which were then analyzed for dicarboxylic acids, ketocarboxylic acids, and α-dicarbonyls. The results showed that oxalic acid（HOOC-COOH, C2） was the dominant species in the summer and winter months, followed by malonic acid（HOOC-CH2-COOH, C3）, and succinic acid[HOOC-（CH2）2-COOH, C4], being consistent with that in other high-altitude regions. Most of the diacids were more abundant in the summer months than in the winter months, while adipic acid（C6） and phahalic acid（Ph） were twice lower in the summer months, suggesting significant impact of anthropogenic pollution on the wintertime alpine atmosphere. Moreover, as major precursors of C2, glyoxal（Gly） and methylglyoxal（mGly） were also lower in the summer months than in the winter months, which were opposite to those of the diacids, indicating that the mountain troposphere was more oxidative in the summer months than in the winter months. Principal component analysis（PCA） further revealed that the wintertime SOA in the Mt. Huangshan troposphere mostly originated from the anthropogenic pollutants from long-distance transport. Conversely, the summertime SOA mostly originated from the further oxidation of the mountainous biogenic sources. The AIM（Aerosol Inorganic Model） calculation results showed that the aqueous-phase C2 production was the primary mechanism of C2 formation in ambient aerosol and was driven by acid-catalyzed oxidation in summer.