Temporal and spatial variations of PM2.5 organic and elemental carbon in Central India

This study describes spatiotemporal patterns from October 2015 to September 2016 for PM2.5 mass and carbon measurements in rural (Kosmarra), urban (Raipur), and industrial (Bhilai) environments, in Chhattisgarh, Central India. Twenty-four-hour samples were acquired once every other week at the rural and industrial sites. Twelve-hour daytime and nighttime samples were acquired either a once a week or once every other week at the urban site. Each site was equipped with two portable, battery-powered, miniVol air samplers with PM2.5 inlets. Annual average PM2.5 mass concentrations were 71.8 ± 27 µg m−3 at the rural site, 133 ± 51 µg m−3 at the urban site, and 244.5 ± 63.3 µg m−3 at the industrial site, ~ 2–6 times higher than the Indian Annual National Ambient Air Quality Standard of 40 µg m−3. Average monthly nighttime PM2.5 and carbon concentrations at the urban site were consistently higher than those of daytime from November 2015 to April 2016, when temperatures were low. Annual average total carbon (TC = OC + EC) at the urban (46.8 ± 23.8 µg m−3) and industrial (98.0 ± 17.2 µg m−3) sites also exceeded the Indian PM2.5 NAAQS. TC accounted for 30–40% of PM2.5 mass. Annual average OC ranged from 17.8 ± 6.1 µg m−3 at the rural site to 64 ± 9.4 µg m−3 at the industrial site, with EC ranging from 4.51 ± 2.2 to 34.01 ± 7.8 µg m−3. The average OC/EC ratio at the industrial site (1.88) was 18% lower than that at the urban site and 52% lower than that at the rural site. OC was attributed to 43.0% of secondary organic carbon (SOC) at the rural site, twice that estimated for the urban and industrial sites. Mortality burden estimates for PM2.5 EC are 4416 and 6196 excess deaths at the urban and industrial sites, respectively, during 2015–2016.