Seasonal variation and light absorption property of carbonaceous aerosol in a typical glacier region of the southeastern Tibetan Plateau
2018
Abstract. Deposition and accumulation of light-absorbing carbonaceous aerosol on
glacier surfaces can alter the energy balance of glaciers. In this study, 2 years
(December 2014 to December 2016) of continuous observations of
carbonaceous aerosols in the glacierized region of the Mt. Yulong and Ganhaizi (GHZ)
basin are analyzed. The average elemental carbon (EC) and organic carbon (OC)
concentrations were 1.51±0.93 and 2.57±1.32 µg m −3 , respectively. Although the annual mean OC ∕ EC
ratio was 2.45±1.96 , monthly mean EC concentrations during the
post-monsoon season were even higher than OC in the high altitudes
(approximately 5000 m a . s . l . ) of Mt. Yulong. Strong photochemical
reactions and local tourism activities were likely the main factors inducing
high OC ∕ EC ratios in the Mt. Yulong region during the monsoon season. The
mean mass absorption efficiency (MAE) of EC, measured for the first time in
Mt. Yulong, at 632 nm with a thermal-optical carbon analyzer using
the filter-based method, was 6.82±0.73 m 2 g −1 ,
comparable with the results from other studies. Strong seasonal and spatial
variations of EC MAE were largely related to the OC abundance. Source
attribution analysis using a global aerosol–climate model, equipped with
a black carbon (BC) source tagging technique, suggests that East Asia
emissions, including local sources, have the dominant contribution (over
50 %) to annual mean near-surface BC in the Mt. Yulong area. There is
also a strong seasonal variation in the regional source apportionment. South
Asia has the largest contribution to near-surface BC during the pre-monsoon
season, while East Asia dominates the monsoon season and post-monsoon season.
Results in this study have great implications for accurately evaluating the
influences of carbonaceous matter on glacial melting and water resource
supply in glacierization areas.
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