Yang Xiao-Ying, Cao Fang, Lin Yu-Qi, Zhang Yan-Lin
Yale-NUIST Center on Atmospheric Environment, Nanjing University of Information Science & Technology, Nanjing 210044, China.
Huan Jing Ke Xue. 2020 Jun 8;41(6):2519-2527. doi: 10.13227/j.hjkx.201911049.
Rainwater samples were collected in Nanjing from December 2016 to November 2017. Water-soluble ion and organic acid content in rainwater samples was determined to analyze the chemical characteristics of precipitation and their seasonality. The positive matrix factorization (PMF) model was employed to identify the potential sources of precipitation. The results show that the volume-weighted mean of pH in precipitation was 5.6, which was higher than the results of previous studies conducted in Nanjing. The volume-weighted mean of total ions was 297.3 μmol·L, and the concentrations of each species were in the order of NH > Ca > K > Na > Mg for cations and NO > SO > Cl > F for anions. The volume-weighted mean of organic acids was 2.86 μmol·L, with organic acids accounting for 2.2% of the total anions. CHO, CHO, and CO were the main organic acids in precipitation with annual volume-weighted means of 1.35, 1.05, and 0.26 μmol·L, respectively. A significant seasonality was observed for the ions and organic acids. The volume-weighted mean of inorganic ions was higher in winter and spring compared to those in summer and autumn. On the other hand, the volume-weighted mean of total organic acids was the highest in summer, followed by spring, and the lowest in winter. High concentrations of organic acids in the summer can be attributed to the biogenic emissions from plants. The ratio of formic and acetic (F/A) showed that organic acids mainly originated from primary emissions (e.g., biogenic emissions, combustion of organics, and traffic emissions) rather than atmospheric oxidation processes. Using the PMF model, we found that marine sources and secondary inorganic products (40.0%) were the predominant sources of inorganic ions and organic acids in precipitation, followed by burning of biomass (22.2%), continental origin and waste incineration (22.0%), secondary organic products (14.5%), and biological emissions along with their secondary products (1.3%).
2016年12月至2017年11月期间在南京采集了雨水样本。测定了雨水样本中的水溶性离子和有机酸含量，以分析降水的化学特征及其季节性。采用正定矩阵因子分解（PMF）模型来识别降水的潜在来源。结果表明，降水pH的体积加权平均值为5.6，高于此前在南京开展的研究结果。总离子的体积加权平均值为297.3μmol·L，阳离子中各物种浓度顺序为NH＞Ca＞K＞Na＞Mg，阴离子中各物种浓度顺序为NO＞SO＞Cl＞F。有机酸的体积加权平均值为2.86μmol·L，有机酸占总阴离子的2.2%。CHO、CHO和CO是降水中的主要有机酸，年体积加权平均值分别为1.35、1.05和0.26μmol·L。离子和有机酸呈现出显著的季节性。与夏季和秋季相比，冬季和春季无机离子的体积加权平均值更高。另一方面，总有机酸的体积加权平均值在夏季最高，其次是春季，冬季最低。夏季有机酸浓度较高可归因于植物的生物源排放。甲酸与乙酸的比例（F/A）表明，有机酸主要源于一次排放（如生物源排放、有机物燃烧和交通排放），而非大气氧化过程。使用PMF模型，我们发现海洋源和二次无机产物（40.0%）是降水中无机离子和有机酸的主要来源，其次是生物质燃烧（22.2%）、大陆源和垃圾焚烧（22.0%）、二次有机产物（14.5%）以及生物排放及其二次产物（1.3%）。
