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The optical characteristics and sources of chromophoric dissolved organic matter (CDOM) in seasonal snow of northwestern China

Preprint published in 2018 by Yue Zhou, Hui Wen, Jun Liu, Wei Pu, Qingcai Chen, Xin Wang
This paper is available in a repository.
This paper is available in a repository.

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Preprint: policy unknown
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Postprint: policy unknown
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Published version: policy unknown

Abstract

Chromophoric dissolved organic matter (CDOM) plays an important role in the global carbon cycle and energy budget. A field campaign was conducted across northwestern China from January to February 2012, and surface seasonal snow samples were collected at 39 sites in Xinjiang and Qinghai provinces. Light-absorption measurements, fluorescence measurements and chemical analysis were conducted to investigate the optical properties and potential sources of CDOM in seasonal snow. The abundance of CDOM (the absorption coefficient at 280 nm, a 280 ) and the spectral slope from 275 to 295 nm (S 275–295 ) ranged from 0.15–10.57 m −1 and 0.0129–0.0389 nm −1 , respectively. The highest average a 280 (2.30±0.52 m −1 ) and lowest average S 275–295 (0.0188±0.0015 nm −1 ) in Qinghai indicated that the snow CDOM in this region had strongly terrestrial characteristic. Relatively low regional average a280 values were found in sites located to the north of the Tianshan Mountains and northwestern Xinjiang along the border of China (0.93±0.68 m −1 and 0.80±0.62 m −1 , respectively). Parallel factor analysis (PARAFAC) identified three types of chromophores that were attributed to two humic-like substances (HULIS, C1 and C2) and one protein-like material (C3). C1 was mainly from soil HULIS, while the potential sources of C2 were complex and included soil, microbial activities, anthropogenic pollution and biomass burning. The good relationship between a 280 and the intensity of C1 (R 2 = 0.938, p<0.001) indicated that the CDOM abundance in the surface snow across northwestern China was mainly controlled by terrestrial sources. In addition, the regional variations of sources for CDOM in snow were further assessed by the analysis of chemical species (e.g., soluble ions) and air mass backward trajectories combined with satellite fire locations.

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