Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP(3)), Department of Environmental Science and Engineering, Fudan University, Shanghai 200438, China.
Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP(3)), Department of Environmental Science and Engineering, Fudan University, Shanghai 200438, China; IRDR International Center of Excellence on Risk Interconnectivity and Governance on Weather/Climate Extremes Impact and Public Health, Fudan University, Shanghai 200433, China.
J Environ Sci (China). 2022 Mar;113:190-203. doi: 10.1016/j.jes.2021.05.035. Epub 2021 Jun 26.
Organic acids are important contributors to the acidity of atmospheric precipitation, but their existence in the Chinese atmosphere is largely unclear. In this study, twelve atmospheric gaseous organic acids, including C-C alkanoic acids, methacrylic acid, pyruvic acid, and benzoic acid, were observed in the suburb of Wangdu, Hebei Province, a typical rural site in the northern China plain from 16 December, 2018 to 22 January, 2019, using a Vocus® Proton-Transfer-Reaction time-of-flight mass spectrometer (Vocus PTR-ToF). The quantification of C-C alkanoic acids by the Vocus PTR-ToF was calibrated according to the titration of a NaOH solution by C-C alkanoic acids from home-made permeation sources, and the other organic acids except for formic acid were quantified based on the k-sensitivity linearity in the Vocus PTR-ToF, whereas formic acid was not quantified because our instrument setting led to a significant underestimation in its concentration. The average total concentration of eleven gaseous organic acids was 6.96 ± 5.20 ppbv (parts per billion by volume). The average concentration of acetic acid was the highest (3.86 ± 3.00 ppbv), followed by propanoic acid, butyric acid, and methacrylic acid. Domestic straw burning was likely the dominant source of the observed gaseous organic acids according to the good correlations between acetonitrile and organic acids and between particulate K and organic acids, and traffic emissions could also have contributed. During episodes with continuously high concentrations of organic acids, short-distance transport dominated in Wangdu according to the backward trajectory analysis. Baoding, Shijiazhuang, and Hengshui areas were the main source areas based on potential source contribution function and concentration weighing track analysis.
有机酸是大气降水酸度的重要贡献者，但它们在中国大气中的存在情况在很大程度上尚不清楚。本研究于 2018 年 12 月 16 日至 2019 年 1 月 22 日在河北省望都县郊区使用 Vocus®质子转移反应飞行时间质谱仪（Vocus PTR-ToF）观测到 12 种大气气态有机酸酸，包括 C-C 链烷酸、甲基丙烯酸、丙酮酸和苯甲酸。Vocus PTR-ToF 对 C-C 链烷酸的定量是根据自制渗透源的 C-C 链烷酸对 NaOH 溶液的滴定来校准的，除甲酸以外的其他有机酸则根据 Vocus PTR-ToF 中的 k-灵敏度线性来定量，而甲酸则未被定量，因为我们的仪器设置导致其浓度被显著低估。11 种气态有机酸的平均总浓度为 6.96±5.20 ppbv（体积十亿分率）。乙酸的平均浓度最高（3.86±3.00 ppbv），其次是丙酸、丁酸和甲基丙烯酸。根据乙腈与有机酸之间以及颗粒物 K 与有机酸之间的良好相关性，以及交通排放的可能贡献，推测观测到的气态有机酸可能主要来自于国内秸秆燃烧。在有机酸浓度持续较高的时段，根据后向轨迹分析，望都以短距离输送为主。基于潜在源贡献函数和浓度加权轨迹分析，保定、石家庄和衡水地区是主要的源区。
