Simultaneous measurements of black carbon and PM 2.5 , CO, and NO x variability at a locally polluted urban location in India

Black carbon, which is a by-product of incomplete combustion of carbon containing fuels, can alter atmospheric radiation property and make adverse impacts on human health. This paper shows the comparative study of particles and associated gaseous pollutants measurements at five observatories dispersed across central part of megacity Delhi, India, with high-temporal resolution (5 min) measurements. The mean ± SD concentrations of black carbon (BC), fine particles (PM 2.5 ), carbon monoxide (CO), and oxides of nitrogen (NO x ) of the all five stations were 13.4 ± 10, 149.6 ± 109 µg m −3 , 3.4 ± 2 ppm, and 81.8 ± 79 ppb, respectively. The mean mass concentration of PM 2.5 was approximately four times and ten times in excess of annual average standards of Indian air quality (40 µg m −3 ) and USEPA (15 µg m −3 ) levels. Highest BC mass concentrations were recorded during winter (December) due to consistent with a shallower atmospheric boundary layer, lower wind speeds, and possibly larger biofuel burning in the coldest period. Also, the strong diurnal dynamics in boundary layer height had a large impact on the ground-level concentrations of all the pollutants. A significant difference in the emissions of atmospheric pollutants was observed over Delhi during weekdays and weekends during study period. There was a strong diurnal effect on BC and the other pollutants, presumably with mixing height as a strong driver. The 24-h cycle is characterized throughout the study by maximum concentrations around midnight and lowest concentrations at 1500–1700 hours local time (LT), with a local maximum between 0800 and 1000 hours LT, presumably due to morning rush hour. While the amplitude of the BC excursion was a factor of 2–3, the mixing height decreased by a factor of 12–14 from day to night. This monitoring program contributed to insights into the levels and dynamics of atmospheric pollutants in the New Delhi megacity over a 5-month period. The concentrations are varying over several timescales, consistent with both atmospheric mixing and variations in presumed emission source strengths. Copyright Springer Science+Business Media Dordrecht 2015