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The Optical and Molecular Characteristics of Water-soluble Organic Carbon in Seasonal Snow across Northern Xinjiang, Northwestern China
YUE ZHOU, Christopher West, Anusha P.S. Hettiyadura, Xiaoying Niu, Tenglong Shi, Wei Pu, Xin Wang, Alexander Laskin, Purdue University
Abstract Number: 240
Working Group: Remote and Regional Atmospheric Aerosol
Abstract
The deposition of light-absorbing aerosol on snow lowers the surface albedo and therefore influences the regional and global climate. In this study, snow samples were collected across regional area of northern Xinjiang, Northwestern China to investigate the optical and molecular characteristics of water-soluble organic carbon (WSOC), and to estimate effects of deposited aerosol on radiative forcing. For samples collected from the industrial region (IND) in Xinjiang, the concentrations of WSOC were higher than those from remote region (REM) (1.97 mg L-1 vs. 0.92mg L-1). The average absorption coefficient of the IND samples was approximately twice higher than that of the REM samples, however values of their characteristic mass absorption coefficients (MACs) showed no substantial difference. Based on the Excitation-Emission Matrices (EEMs) of WSOC samples and parallel factor (PARAFAC) analysis, two humic-like (HULIS-1 and HULIS-2) and one protein-like (PRLIS) components were identified. IND samples exhibited higher relative intensities of HULIS-2 (46%), but lower PRILS contributions (30%) compared to those of REM samples (36% and 42%, respectively). Molecular-level characterization of WSOC samples using high-resolution mass spectrometry provided further insights into differences between IND and REM collected WSOC samples. Generally, the IND samples were characterized by lower H/C and O/C elemental ratios, but higher unsaturated degree compared to REM samples. Much more CHOS and CHONS compounds were detected in IND samples, indicating different sources of snow WSOC from these two regions. The averages of WSOC-induced radiative forcing (RF) were estimated as 0.21 and 0.14 W m-2 in IND and REM regions, respectively, and contributed to 7% and 10% of the BC-induced RF. This study presents a comprehensive overview of WSOC in seasonal snow of Northwestern China, which helps to better understand their characteristics, sources, and climatic effects.