Secondary formation of oxalic acid and related organic species from biogenic sources in a larch forest at the northern slope of Mt. Fuji
Secondary formation of oxalic acid and related organic species from biogenic sources in a larch forest at the northern slope of Mt. Fuji
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DOI：
10.1016/j.atmosenv.2017.07.028
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发表时间：
2017-10
影响因子：
5
通讯作者：
Tomoki Mochizuki;K. Kawamura;Y. Miyazaki;R. Wada;Yoshiyuki Takahashi;N. Saigusa;A. Tani
中科院分区：
文献类型：
--
作者：
Tomoki Mochizuki;K. Kawamura;Y. Miyazaki;R. Wada;Yoshiyuki Takahashi;N. Saigusa;A. Tani
为了更好地了解森林大气中水溶性有机气溶胶的形成，我们测量了位于日本落叶松（Larix kaempferi）林（位于日本山北方坡）气溶胶中的低分子量（LMW）二元羧酸、羰基羧酸、α-二羰基化合物、不饱和脂肪酸（UFAs）和水溶性有机碳（WSOC）。2012年夏天，日本富士。二羧酸、氧代羧酸、α-二羰基化合物和WSOC的浓度在白天最高。草酸在低分子量二羧酸中的相对丰度平均为52%，其平均浓度为214 ng m−3。研究发现，草酸的日变化和时间变化与异戊二烯和α-蒎烯的日变化和时间变化不同，而异戊二烯和α-蒎烯的生物源次生有机气溶胶（BSOAs）的日变化和时间变化与草酸相似。草酸/BSOAs的质量浓度比是相对恒定的，虽然甲苯的浓度，这是一种人为的挥发性有机化合物的大的变化进行了观察。这些结果表明，草酸的形成与森林大气中O3等氧化剂对异戊二烯和α-蒎烯的氧化有关。此外，还首次观察到森林中的不饱和脂肪酸浓度在白天急剧下降。壬二酸与不饱和脂肪酸的质量浓度比与O3呈正相关，表明不饱和脂肪酸被氧化生成壬二酸，壬二酸在森林大气中可能进一步分解为草酸。我们发现，草酸的贡献WSOC是显着的高，从3.7%到9.7%（平均6.0%）。研究表明，森林生态系统是大气中草酸和其他二元酸的重要来源。
To better understand the formation of water-soluble organic aerosols in the forest atmosphere, we measured low molecular weight (LMW) dicarboxylic acids, oxocarboxylic acids, α-dicarbonyls, unsaturated fatty acids (UFAs), and water-soluble organic carbon (WSOC) in aerosols from aLarix kaempferiforest located at the northern slope of Mt. Fuji, Japan, in summer 2012. Concentrations of dicarboxylic acids, oxocarboxylic acids, α-dicarbonyls, and WSOC showed maxima in daytime. Relative abundance of oxalic acid in LMW dicarboxylic acids was on average 52% and its average concentration was 214 ng m−3. We found that diurnal and temporal variations of oxalic acid are different from those of isoprene and α-pinene, whereas biogenic secondary organic aerosols (BSOAs) derived from isoprene and α-pinene showed similar variations with oxalic acid. The mass concentration ratios of oxalic acid/BSOAs were relatively constant, although a large variation in the concentrations of toluene that is an anthropogenic volatile organic compound was observed. These results suggest that formation of oxalic acid is associated with the oxidation of isoprene and α-pinene with O3and other oxidants in the forest atmosphere. In addition, concentrations of UFAs were observed, for the first time, to decrease dramatically during daytime in the forest. Mass concentration ratios of azelaic acid to UFAs showed a positive correlation with O3, suggesting that UFAs are oxidized to yield azelaic acid, which may be further decomposed to oxalic acid in the forest atmosphere. We found that contributions of oxalic acid to WSOC are significantly high ranging from 3.7 to 9.7% (average 6.0%). This study demonstrates that forest ecosystem is an important source of oxalic acid and other dicarboxylic acids in the atmosphere.