Abstract
Measurement of elemental carbon (EC) and black carbon (BC) aerosols was carried out using AE-31, 7 channel aethalometer at Kathmandu and Biratnagar; two mega cities of Nepal, for five months, January to May 2011 to study its temporal and spatial variation. Total solar radiation was also monitored using Kipp and Zonen CMP 6 pyranometer. Monthly concentration variation for EC and BC was distinct in both study sites. At Biratnagar, monthly EC concentration varies from 3.3 -20.7 µg /m3 while in Kathmandu it varies between 6.0-13.7 µg /m3. Similarly, BC monthly concentration ranges from 3.3 -20.1 µg /m3 and 7.0-14.9 µg /m3 respectively. It was found that both EC and BC were highest during January in both the sites and it decreases gradually. Monthly average solar radiation shows a maximum value in May and minimum in January. A distinct anti-correlation between monthly average carbonaceous aerosols and total solar radiation was observed. Moreover, there was a pronounced diurnal variation of both carbonaceous aerosols EC and BC in the sites with two high peaks one in the morning at about 9:00 and another at late evening 20:00 local time with minimum concentration in the afternoon. The nature of peaks were different at two sites. Biratnagar shows a larger evening peak while Kathmandu shows in the morning inferring heavy domestic and industrial fuel consuming activities in evening and morning respectively. In addition to this, daily and monthly concentration of EC was more than BC at Biratnagar reflecting slightly more biomass fuel consumption than fossil fuel for domestic, industrial and other urban activities. In contrast to this, Kathmandu shows more domination of fossil fuel than biofuel because of reverse order concentration of carbonaceous aerosols. Total solar radiation also shows apparent diurnal variation in both sites with the highest value at around noon time.
Highlights
Carbonaceous aerosol is the main constituent (2080 % of fine particle) in the particulate matter [1]
Daily and monthly concentration of elemental carbon (EC) was more than Black carbon (BC) at Biratnagar reflecting slightly more biomass fuel consumption than fossil fuel for domestic, industrial and other urban activities
BC represents the fraction of the carbonaceous material that absorbs visible light; EC is graphitic carbon that absorbs in the visible range and it is not reduced to CO2 when heated to 800oC in an inert atmosphere
Summary
Carbonaceous aerosol is the main constituent (2080 % of fine particle) in the particulate matter [1]. About one half of the global BC aerosol emission is estimated to rise from fossil fuel combustion [5]. BC represents the fraction of the carbonaceous material that absorbs visible light; EC is graphitic carbon that absorbs in the visible range and it is not reduced to CO2 when heated to 800oC in an inert atmosphere. To have a snap- shot of EC, BC and total solar radiation, Kathmandu, the capital city of the country, and Biratnagar, the industrial city, are considered in this studied. Present study will provide a comparative knowledge of carbonaceous aerosols and total solar radiation at Kathmandu and Biratnagar which are two representative sites of valley and flat land in the country respectively
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More From: Journal of Technology Innovations in Renewable Energy
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