Distributions and sources of low-molecular-weight monocarboxylic acids in gas and particles from a deciduous broadleaf forest in northern Japan
Distributions and sources of low-molecular-weight monocarboxylic acids in gas and particles from a deciduous broadleaf forest in northern Japan
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DOI：
10.5194/acp-19-2421-2019
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发表时间：
2019-02-25
影响因子：
6.3
通讯作者：
Boreddy, Suresh Kumar Reddy
中科院分区：
文献类型：
--
作者：
Mochizuki, Tomoki;Kawamura, Kimitaka;Boreddy, Suresh Kumar Reddy
为了更好地了解森林大气中低分子量（LMW）一元羧酸（一元酸）的分布和来源，我们在日本北部的落叶阔叶林场地同时收集了气体和颗粒样品。在气相和颗粒相中检测到 LMW 正常 (C-1-C-10)、支链 (iC(4)-iC(6))、羟基（乙醇酸和乳酸）和芳香族（苯甲酸）一元酸。气相中主要的 LMW 一元酸是甲酸（平均值：953 ng m(-3)）和乙酸（528 ng m(-3)），其次是丙酸（37 ng m(-3)）或异戊酸（42 ng m(-3)）。在颗粒相中，异戊酸（159 ng m(-3)）占主导地位，其次是乙酸（104 ng m(-3)）和甲酸（71 ng m(-3)）或乳酸（65 ng m(-3)）。 LMW 一元酸的浓度没有显示出与人为示踪剂（例如 nss-SO42- 和 NO3-）的相关性，表明人为贡献并不重要。气相中 C-1-C-6 一元酸的浓度与异丁酸 (iC(4)) 呈正相关 (r(2) = 0.21-0.91)，异丁酸可能是由土壤中微生物活动产生的。森林土壤可能是森林大气中气态C-1-C-6一元酸的来源。颗粒相中的乙酸与壬酸 (C-9) 呈正相关 (r(2) = 0.63)，表明乙酸和壬酸的形成除了与生物挥发性有机化合物的光化学氧化有关外，还与气溶胶相中生物不饱和脂肪酸的氧化有关。甲酸和乙酸的颗粒相分数（F-p）与环境温度（C-1：r（2）= 0.49，C-2：r（2）= 0.60）呈负相关，但与白天的相对湿度（C-1：r（2）= 0.30，C-2：r（2）= 0.55）呈正相关，这表明这些气象参数对于一元酸的气体和颗粒分配很重要森林的气氛。
To better understand the distributions and sources of low-molecular-weight (LMW) monocarboxylic acids (monoacids) in the forest atmosphere, we conducted simultaneous collection of gaseous and particulate samples at a deciduous broadleaf forest site in northern Japan. LMW normal (C-1-C-10), branched (iC(4)-iC(6)), hydroxyl (glycolic and lactic) and aromatic (benzoic) monoacids were detected in the gas and particle phases. The dominant LMW monoacids in gas phase were formic (mean: 953 ng m(-3)) and acetic (528 ng m(-3)) acids followed by propionic (37 ng m(-3)) or isopentanoic (42 ng m(-3)) acid. In the particle phase, isopentanoic (159 ng m(-3)) was dominant, followed by acetic (104 ng m(-3)) and formic (71 ng m(-3)) or lactic (65 ng m(-3)) acids. Concentrations of LMW monoacids did not show correlations with anthropogenic tracers such as nss-SO42- and NO3-, indicating that anthropogenic contribution is not important. Concentrations of C-1-C-6 monoacids in the gas phase showed positive correlations (r(2) = 0.21-0.91) with isobutyric acid (iC(4)), which may be produced by microbial activity in soil. The forest soil may be a source of gaseous C-1-C-6 monoacids in the forest atmosphere. Acetic acid in the particle phase positively correlated with nonanoic acid (C-9) (r(2) = 0.63), suggesting that formation of acetic and nonanoic acids is associated with the oxidation of biogenic unsaturated fatty acids in the aerosol phase, in addition to photochemical oxidation of biogenic volatile organic compounds. The particle-phase fractions (F-p) of formic and acetic acids showed negative correlation with ambient temperature (C-1: r(2) = 0.49, C-2: r(2) = 0.60) but showed positive correlation with relative humidity (C-1: r(2) = 0.30, C-2: r(2) = 0.55) in daytime, suggesting that these meteorological parameters are important for the gas and particle portioning of monoacids in the forest atmosphere.