Abstract. Chromophoric dissolved organic matter (CDOM) plays an important
role in the global carbon cycle and energy budget but is rarely studied in
seasonal snow. A field campaign was conducted across northwestern China from
January to February 2012, and surface snow samples were collected at 39 sites
in Xinjiang and Qinghai provinces. Absorption and fluorescence
spectroscopies,
along with chemical analysis, were used to investigate the optical
characteristics and potential sources of CDOM in seasonal snow. The abundance of CDOM, shown as the absorption coefficient at 280 nm,
aCDOM(280), and the spectral slope from 275 to 295 nm
(S275−295) ranged from 0.15 to 10.57 m−1 and
0.0129 to 0.0389 nm−1. The highest average
aCDOM(280) (2.30±0.52 m−1) was found in
Qinghai, and the lowest average S275−295 (0.0188±0.0015 nm−1) indicated that the snow CDOM in this region had a strongly
terrestrial characteristic. The lower values of aCDOM(280) were found at 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). Parallel factor (PARAFAC) analysis
identified three types of fluorophores that were attributed to two humic-like
substances (HULIS, C1 and C2) and one protein-like material (C3). C1 was
mainly from soil HULIS, C3 was a type of autochthonously labile organic
matter, while the potential sources of C2 were complex, including soil,
microbial activity, anthropogenic pollution, and biomass burning.
Furthermore, the regional variations of sources for snow CDOM were assessed
by analyses of chemical species (e.g., soluble ions), fluorescent components,
and air mass backward trajectories combined with satellite-derived active-fire
locations.
Supplementary material to "The optical characteristics and sources of chromophoric
dissolved organic matter
(CDOM) in seasonal snow of
northwestern China"
