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Seasonal inhomogeneity of soot particles over the central Indo-Gangetic Plains,India: Influence of meteorology |
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| Authors: | B P Singh S Tiwari Philip K Hopke R S Singh D S Bisht A K Srivastava R K Singh U C Dumka A K Singh B N Rai Manoj K Srivastava |
| Institution: | 1. Department of Geophysics, Banaras Hindu University, Varanasi, 221005, India 2. Indian Institute of Tropical Meteorology (New Delhi Branch), Delhi, 110060, India 3. Clarkson University, Potsdam, NY, Box 5708, 13699-5708, USA 4. Department of Chemical Engineering, Banaras Hindu University, Varanasi, 221005, India 5. Aryabhatta Research Institute of Observational Sciences, Manora Peak, Nainital, 263002, India 6. Department of Physics, Banaras Hindu University, Varanasi, 221005, India |
| Abstract: | Black carbon (BC) particles play a unique and important role in earth’s climate system. BC was measured (in-situ) in the central part of the Indo-Gangetic Plains (IGP) at Varanasi, which is a highly populated and polluted region due to its topography and extensive emission sources. The annual mean BC mass concentration was 8.92 ± 7.0 µg m -3, with 34% of samples exceeding the average value. Seasonally, BC was highest during the post-monsoon and winter periods (approximately 18 µg m -3) and lower in the premonsoon/ monsoon seasons (approximately 6 µg m -3). The highest frequency (approximately 46%) observed for BC mass was in the interval from 5 to 10 µg m -3. However, during the post-monsoon season, the most common values (approximately 23%) were between 20 and 25 µg m -3. The nighttime concentrations of BC were approximately twice as much as the daytime values because of lower boundary layer heights at nighttime. The Ångström exponent was significantly positively correlated (0.55) with ground-level BC concentrations, indicating the impact of BC on the columnar aerosol properties. The estimated mean absorption Ångström exponent was 1.02 ± 0.08 µg m -3, indicating that the major source of BC was from fossil fuel combustion. Significant negative correlations between BC mass and meteorological parameters indicate a pronounced effect of atmospheric dynamics on the BC mass in this region. The highest mean BC mass concentration (18.1 ± 6.9 µg m -3) as a function of wind speed was under calm wind conditions (38% of the time). |
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