Contributions of low molecular weight carboxylic acids to aerosols and wet deposition in a natural subtropical broad-leaved forest environment

• Published in: Atmospheric environment (1994) Vol. 81; pp. 270 - 279
• Main Authors: Tsai, Ying I., Kuo, Su-Ching
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.12.2013; Elsevier
• Subjects: Aerosol; Applied sciences; Atmospheric pollution; Broad-leaved forest; Exact sciences and technology; Organic acids; Pollutants physicochemistry study: properties, effects, reactions, transport and distribution; Pollution; Raman spectroscopy; Wet deposition; Asia; Taiwan; Broad-leaved forest; Wet deposition; Raman spectroscopy; Aerosol; Organic acids; Subtropical zone; Forests; Atmospheric fallout; Diurnal variation; Rain; Carboxylic acid; Aerosols; Air pollution; Chemical composition; Raman spectrometry; Organic compounds; Fog
• ISSN: 1352-2310; 1873-2844
• DOI: 10.1016/j.atmosenv.2013.08.061

The carboxylic acid component of autumn aerosol and wet deposition (fog water and rainwater) in a broad-leaved forest in central Taiwan was investigated. High levels of low molecular weight carboxylic acids (LMWCAs) were noted in all deposition types. Acetic acid, oxalic acid and formic acid were the most prevalent carboxylic acids, together accounting for 72.2% (fog water), 86.7% (rain water), 77.2% (PM2.5) and 88.3% (PM2.5–10) of total carboxylic acid. The forest fog water contained 2453.9 ± 1030.5 ng mL−1 of carboxylic acid, 2.71 times more than was contained in forest rainwater. In PM, most carboxylic acid existed in the fine PM2.5 aerosol (576.6 ± 254.1 ng m−3 or 6.28 times more than was contained in PM2.5–10. Most carboxylic acids in PM had higher concentrations during the day. Pyruvic acid concentration was higher during the night (2.97 times), however, owing to its rapid photodegradation during the day. Citric acid accounted for 9.1% of the total carboxylic acid in fog water compared with just 1.8% in rainwater, confirming its origin from emissions from leaves. Raman spectroscopy was used to observe the photochemical conversion of citric acid into intermediate products and this observation confirmed that the carboxylic acids identified in the forest dry and wet depositions originated directly from biological emissions in the forest environment. •We investigated carboxylic acids in deposition in a broad-leaved sub-tropical forest.•Acetic acid, oxalic acid and formic acid were the most prevalent carboxylic acids.•Most carboxylic acids presented at highest concentration in fog water deposition.•Pyruvic acid is rapidly photodegraded leading to lower concentrations during the day.•Raman spectroscopy confirmed origin of carboxylic acids from forest emissions.