期刊
ATMOSPHERIC ENVIRONMENT
卷 185, 期 -, 页码 1-6出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.atmosenv.2018.04.037
关键词
Biomass burning; Water soluble organic carbon; pH; Photolysis; Light absorption
资金
- National Key RD Plan [2017YFC0213001]
- National Natural Science Foundation of China [41373131]
- National Key Technology Research and Development Program of the Ministry of Science and Technology of China [2014BAC22B04]
- National Natural Science Funds for Distinguished Young Scholars of China [41225013]
- National Science and Technology Support Program [2014BAC06B01]
Water soluble organic carbon (WSOC) can significantly influence the aerosol optical properties and the aqueous phase chemistry in cloudwater, fogwater and aerosol liquid water. Here, we examine how the changing pH (in acidic range) affects the absorption spectra of aqueous extracts from field biomass burning aerosols, under dark conditions and in presence of simulated sunlight illumination. The observation under dark conditions indicates that pH variation from 2 to 5 induces significantly enhanced light absorbance in the wavelength ranges of 235-270 nm and 300-550 nm, whereas the light absorbance decreased in the range of 270-300 nm, which might be partially ascribed to the deprotonation of carboxylic acids and phenols. During the extract photolysis, light absorption exhibits photo-bleaching below 380 nm and photo-enhancement above 380 nm, indicating that at acidic levels (pH = 2-5), the particle extracts could undergo a significant composition evolution leading to a modification of absorptive properties. Meanwhile, after 12 h-photolysis, the acidity ([H+]) normalized by WSOC concentration in aqueous extracts ([WSOCae]) increased with a variation of Delta[11(+)]/[WSOCae] = (3.7 +/- 0.7) x 10(-7) mol mgC(-1) (mean +/- standard deviation), suggesting the formation of new acidic substances. Although these findings were acquired in aqueous solutions more relevant to cloud and fog water, the similar evolution likely occurs in wetted aerosols. This calls more attention to the effect of acidity on the wetted aerosols in order to better estimate the aerosol radiative forcing.
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