Abstract
India is currently experiencing degraded air quality, and future economic development will lead to challenges for air quality management. Scenarios of sectoral emissions of fine particulate matter and its precursors were developed and evaluated for 2015–2050, under specific pathways of diffusion of cleaner and more energy-efficient technologies. The impacts of individual source sectors on PM2.5 concentrations were assessed through systematic simulations of spatially and temporally resolved particulate matter concentrations, using the GEOS-Chem model, followed by population-weighted aggregation to national and state levels. We find that PM2.5 pollution is a pan-India problem, with a regional character, and is not limited to urban areas or megacities. Under present-day emissions, levels in most states exceeded the national PM2.5 annual standard (40 μg m−3). Sources related to human activities were responsible for the largest proportion of the present-day population exposure to PM2.5 in India. About 60 % of India’s mean population-weighted PM2.5 concentrations come from anthropogenic source sectors, while the remainder are from “other” sources, windblown dust and extra-regional sources. Leading contributors are residential biomass combustion, power plant and industrial coal combustion and anthropogenic dust (including coal fly ash, fugitive road dust and waste burning). Transportation, brick production and distributed diesel were other contributors to PM2.5. Future evolution of emissions under regulations set at current levels and promulgated levels caused further deterioration of air quality in 2030 and 2050. Under an ambitious prospective policy scenario, promoting very large shifts away from traditional biomass technologies and coal-based electricity generation, significant reductions in PM2.5 levels are achievable in 2030 and 2050. Effective mitigation of future air pollution in India requires adoption of aggressive prospective regulation, currently not formulated, for a three-pronged switch away from (i) biomass-fuelled traditional technologies, (ii) industrial coal-burning and (iii) open burning of agricultural residue. Future air pollution is dominated by industrial process emissions, reflecting larger expansion in industrial, rather than residential energy demand. However, even under the most active reductions envisioned, the 2050 mean exposure, excluding any impact from windblown mineral dust, is estimated to be nearly 3 times higher than the WHO Air Quality Guideline.
Highlights
India hosts the world’s second largest population (UNDP, 2017), but accounts for only 6 % of the world’s total primary energy use (IEA, 2015)
Ambient PM2.5 concentrations are influenced by emissions of both primary or directly emitted PM2.5, and its precursor gases, including SO2, NH3, NOx and nonmethane volatile organic compounds (NMVOCs), whose atmospheric reactions yield secondary particulate sulfate, nitrate and organic carbon, while reactions of NOx and NMVOCs increase ozone levels
The impacts of individual source sectors on PM2.5 concentrations is assessed through simulation of spatially and temporally resolved particulate matter concentrations, using the GEOS-Chem chemical transport model, followed by aggregation to populationweighted concentrations at both national and state levels
Summary
India hosts the world’s second largest population (UNDP, 2017), but accounts for only 6 % of the world’s total primary energy use (IEA, 2015). Strategies for mitigation of air pollution require understanding of pollutant emissions, differentiated by emitting sectors and by sub-national regions, representing both present-day conditions and future evolution under different pathways of growth and technology change. The impacts of individual source sectors on PM2.5 concentrations is assessed through simulation of spatially and temporally resolved particulate matter concentrations, using the GEOS-Chem chemical transport model, followed by aggregation to populationweighted concentrations (estimated as the sum of product of concentration and population for each grid divided by the total population) at both national and state levels. C. Venkataraman et al.: Source influence on emission pathways and ambient PM2.5 pollution and state levels under present-day and future emission scenarios; and the last section discusses findings and conclusions
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