title: Organic acids in cloud water and rainwater at a mountain site in acid rain areas of South China.
abstract: To investigate the chemical characteristics of organic acids and to identify their source, cloud water and rainwater samples were collected at Mount Lu, a mountain site located in the acid rain-affected area of south China, from August to September of 2011 and March to May of 2012. The volume-weighted mean (VWM) concentration of organic acids in cloud water was 38.42 μeq/L, ranging from 7.45 to 111.46 μeq/L, contributing to 2.50 % of acidity. In rainwater samples, organic acid concentrations varied from 12.39 to 68.97 μeq/L (VWM of 33.39 μeq/L). Organic acids contributed significant acidity to rainwater, with a value of 17.66 %. Formic acid, acetic acid, and oxalic acid were the most common organic acids in both cloud water and rainwater. Organic acids had an obviously higher concentration in summer than in spring in cloud water, whereas there was much less discrimination in rainwater between the two seasons. The contribution of organic acids to acidity was lower during summer than during spring in both cloud water (2.20 % in summer vs 2.83 % in spring) and rainwater (12.24 % in summer vs 19.89 % in spring). The formic-to-acetic acid ratio (F/A) showed that organic acids were dominated by primary emissions in 71.31 % of the cloud water samples and whole rainwater samples. Positive matrix factorization (PMF) analysis determined four factors as the sources of organic acids in cloud water, including biogenic emissions (61.8 %), anthropogenic emissions (15.28 %), marine emissions (15.07 %) and soil emissions (7.85 %). The findings from this study imply an indispensable role of organic acids in wet deposition, but organic acids may have a limited capacity to increase ecological risks in local environments.
authors: School of Environmental Science and Engineering, Shandong University, Jinan, 250100, China.
authors: Xiao
authors: X
authors: Sun
authors: School of Environmental Science and Engineering, Shandong University, Jinan, 250100, China. wy@sdu.edu.cn.
authors: Yan
authors: Y
authors: Wang
authors: School of Environmental Science and Engineering, Shandong University, Jinan, 250100, China.
authors: Haiyan
authors: H
authors: Li
authors: Shandong Academy of Environmental Science, Jinan, 250013, China.
authors: Xueqiao
authors: X
authors: Yang
authors: Environment Research Institute, Shandong University, Jinan, 250100, China.
authors: Lei
authors: L
authors: Sun
authors: Environment Research Institute, Shandong University, Jinan, 250100, China.
authors: Xinfeng
authors: X
authors: Wang
authors: Department of Civil and Environmental Engineering, the Hong Kong Polytechnic University, Hong Kong, China.
authors: Tao
authors: T
authors: Wang
authors: Environment Research Institute, Shandong University, Jinan, 250100, China.
authors: Wenxing
authors: W
authors: Wang
mesh_terms: D019342:Acetic Acid / Q000032:analysis*; D015258:Acid Rain / Q000032:analysis*; D000531:Altitude; D002681:China; D004784:Environmental Monitoring; D005561:Formates / Q000032:analysis*; D019815:Oxalic Acid / Q000032:analysis*; D012621:Seasons; D014874:Water Pollutants, Chemical / Q000032:analysis
chemical_list: D015258:Acid Rain; D005561:Formates; D014874:Water Pollutants, Chemical; C030544:formic acid; D019815:Oxalic Acid; D019342:Acetic Acid
keywords: Cloud water; Mount Lu; Organic acids; Rainwater; Sources