Establishing Contributions from Agricultural Emissions to India's Ambient PM2.5 Exposures

GIRIVENDRA PRATAP YADAV, Neeldip Barman, Lucas Rojas-Mendoza, Zainab Arub, Piyush Bhardwaj, Julian Marshall, Joshua S. Apte, Srinidhi Balasubramanian, Chandra Venkataraman, Indian Institute of Technology Bombay, Mumbai, India

     Abstract Number: 438
     Working Group: Aerosol Exposure

Abstract
India has among the highest ambient PM_2.5 levels, posing critical risks to public health burden. PM_2.5 pollution from the agriculture sector, particularly, from crop residue burning in North India has received widespread attention. Yet, agriculture emissions result from many more sources. The impacts of the emitted pollutants from agricultural sources on PM_2.5 and their regional heterogeneity are unclear. We implemented the PAVITRA tool, that couples a high-resolution (5×5 km²⁾ representative emissions inventory with a recently developed India specific reduced-complexity air quality model (InMAP-PAVITRA) with demonstrated model performance against observations (NMB: 2.55%,  RSME: 36.30 µg/m³, IOA: 0.69). The contribution from emissions of ammonia (NH₃), primary PM_2.5, nitrogen oxide (NOx), sulfur dioxide (SO₂) and non-methane volatile organic compounds (NMVOCs) to ambient PM_2.5, were estimated and sensitivity of PM_2.5 exposure reduction under four emission-reduction scenarios (100%-25%) was assessed. Agriculture contributed 7 µg/m³ (15%) to India’s annual PM_2.5 exposure, with NH₃ alone accounting for ~70% (~5 µg/m³). Contribution of NOx, primary PM_2.5, NMVOCs and SO₂ were smaller (0.95, 0.81, 0.14 and 0.10 µg/m³, respectively). Emission-reduction of NH₃, resulted in reduced PM_2.5 exposures by 5.04-2.51 µg/m³, yielding far larger reductions compared to NOx (0.96-0.24 µg/m³) and primary PM_2.5 (0.81-0.20 µg/m³). This highlights NH₃, as key target pollutant, emitted from the manure management source in agriculture. Particulate ammonium (6–14 µg/m³) that results from NH3 reactions was concentrated in the Indo-Gangetic Plain (IGP) and Eastern India, with five major clusters exceeding 10 µg/m³. In contrast, primary PM_2.5 concentrations (2-8 µg/m³) were more concentrated within northwest IGP. These findings emphasize the need for regional NH₃ mitigation to control agriculture-driven PM_2.5 pollution in India.