Source apportionment of PM_2.5 in North India using source-oriented air quality models

In recent years, severe pollution events were observed frequently in India especially at its capital, New Delhi. However, limited studies have been conducted to understand the sources to high pollutant concentrations for designing effective control strategies. In this work, source-oriented versions of the Community Multi-scale Air Quality (CMAQ) model with Emissions Database for Global Atmospheric Research (EDGAR) were applied to quantify the contributions of eight source types (energy, industry, residential, on-road, off-road, agriculture, open burning and dust) to fine particulate matter (PM_2.5) and its components including primary PM (PPM) and secondary inorganic aerosol (SIA) i.e. sulfate, nitrate and ammonium ions, in Delhi and three surrounding cities, Chandigarh, Lucknow and Jaipur in 2015. PPM mass is dominated by industry and residential activities (>60%). Energy (∼39%) and industry (∼45%) sectors contribute significantly to PPM at south of Delhi, which reach a maximum of 200 μg/m³ during winter. Unlike PPM, SIA concentrations from different sources are more heterogeneous. High SIA concentrations (∼25 μg/m³) at south Delhi and central Uttar Pradesh were mainly attributed to energy, industry and residential sectors. Agriculture is more important for SIA than PPM and contributions of on-road and open burning to SIA are also higher than to PPM. Residential sector contributes highest to total PM_2.5 (∼80 μg/m³), followed by industry (∼70 μg/m³) in North India. Energy and agriculture contribute ∼25 μg/m³ and ∼16 μg/m³ to total PM_2.5, while SOA contributes <5 μg/m³. In Delhi, industry and residential activities contribute to 80% of total PM_2.5. - Highlights: • Sources of PM_2.5 in North India were quantified by source-oriented CMAQ. • Industrial/residential activities are the dominating sources (60–70%) for PPM. • Energy/agriculture are the most important sources (30–40%) for SIA. • Strong seasonal variations were predicted in contributions of sources to PPM/SIA. • Industry/residential/energy are top three sources to PM_2.5 in all selected cities. - Source-oriented air quality models indicate that industry, residential activities and energy are the main sources of PM_2.5 in Delhi and other cities in North India.