Airborne black carbon concentrations over an urban region in western India—temporal variability, effects of meteorology, and source regions
- 416 Downloads
This study characterizes over 5 years of high time resolution (5 min), airborne black carbon (BC) concentrations (July 2003 to December 2008) measured over Ahmedabad, an urban region in western India. The data were used to obtain different time averages of BC concentrations, and these averages were then used to assess the diurnal, seasonal, and annual variability of BC over the study region. Assessment of diurnal variations revealed a strong association between BC concentrations and vehicular traffic. Peaks in BC concentration were co-incident with the morning (0730 to 0830, LST) and late evening (1930 to 2030, LST) rush hour traffic. Additionally, diurnal variability in BC concentrations during major festivals (Diwali and Dushera during the months of October/November) revealed an increase in BC concentrations due to fireworks displays. Maximum half hourly BC concentrations during the festival days were as high as 79.8 μg m−3. However, the high concentrations rapidly decayed suggesting that local meteorology during the festive season was favorable for aerosol dispersion. A multiple linear regression (MLR) model with BC as the dependent variable and meteorological parameters as independent variables was fitted. The variability in temperature, humidity, wind speed, and wind direction accounted for about 49% of the variability in measured BC concentrations. Conditional probability function (CPF) analysis was used to identify the geographical location of local source regions contributing to the effective BC measured (at 880 nm) at the receptor site. The east north-east (ENE) direction to the receptor was identified as a major source region. National highway (NH8) and two coal-fired thermal power stations (at Gandhinagar and Sabarmati) were located in the identified direction, suggesting that local traffic and power plant emissions were likely contributors to the measured BC.
KeywordsAhmedabad Western India BC concentrations Diurnal variability Seasonal and annual variability Effect of meteorology Conditional probability function (CPF)
- ART, Ahmedabad Bus Rapid Transit System, India. ART report 2006, <http://www.ahmedabadbrts.com/images/05.Traffic%20volume%20characteristics%20&%20Juunction%20Management.pdf>, accessed on 22/06/10
- Baron R E, Montgomery W D and Tuladhar S D (2010) An analysis of black carbon mitigation as a response to climate change, Copenhagen Consensus Center, <http://fixtheclimate.com/uploads/tx_templavoila/AP_Black_Carbon_Baron_Montgomery_Tuladhar_v.4.0.pdf>, accessed on 20/06/10
- CPCB, Central Pollution Control Board, India. CBCB Air quality data 2004–2006, downloaded via <http://www.cpcb.nic.in/Air_quality_data.php>, accessed on 27/07/10
- NASA GES–DISC, NASA Goddard Earth Sciences Data and Information Services Center, USA. Precipitation data 2003–2008 downloaded via <http://disc.sci.gsfc.nasa.gov/giovanni>, accessed on 15/06/2010
- Hansen ADA (2005) The Aethalometer, Magee Scientific 2005, <http://mageesci.com/support/downloads/Aethalometer_book_2005.07.03.pdf>, accessed on 23/07/2010
- Nishanth T, Satheesh Kumar MK (2011) Increasing trends of tropospheric ozone and NO2 at the prominent hot spots along the coastal belt of the Arabian Sea in Indian Subcontinent. Int J Environ Sci 1 No.5Google Scholar
- USAID, United States Agency for International Development (2010) Black carbon emission in Asia: sources, impacts, and abatement opportunities, <http://usaid.eco-asia.org/programs/cdcp/reports/summary-black-carbon-emissions-in-asia.pdf>, accessed on 27/07/10.