Crop-Specific Oxidative Potential of PM2.5 from Major Crop Residue Burning in India Assessed Using the Dithiothreitol (DTT) Assay.

Emissions of fine particulate matter (PM2.5) from crop residue burning (CRB) are major contributors to air pollution across India, particularly the Indo-Gangetic Plain, where concentrations during burning events often exceed WHO guidelines. While PM2.5 mass is widely used to assess air quality, mass alone does not capture toxicity, as health effects are strongly determined by chemical composition of particles. Oxidative potential (OP), i.e., the capability of PM in depleting antioxidants or producing reactive oxygen species, has been widely recognized as a more health-relevant indicator than particulate matter (PM) mass, and dithiothreitol (DTT) assay is the most widely used chemical endpoint of OP quantification. Previous research on Indian CRB has primarily focused on PM2.5 mass, emission factors (EF), and chemical composition. However, no systematic, crop-specific assessment of DTT-based OP exists for major crop burning residues such as wheat, rice, sugarcane, and corn. Moreover, the effect of combustion characteristics on the OP of PM2.5 from these residues remains understudied.
The overall aim of our study was to provide a combustion-informed, source-resolved assessment of the OP of PM2.5 emitted from major Indian crop residues, to constrain CRB health impacts in India. We quantified EF and modified combustion efficiency (MCE) for each crop residue, measured the water-soluble OP using complementary DTT-based endpoints, including DTT depletion (OPDTT) and hydroxyl radical formation (OPOH-DTT), and examined how crop-specific OP differences are influenced by combustion characteristics. Controlled laboratory combustion experiments were conducted to generate source-specific PM2.5 under reproducible conditions, with their water-soluble fraction analyzed using DTT assays. The resulting particles were characterized for mass, size, and chemical composition. We found that OP differed across crop residues, showing redox activity varies with combustion characteristics and particle composition. The correlation between OP and crop EF, MCE, and chemical composition will be presented in the conference. Our study will address the gap of the health effects of crop-burning residues and the crucial drivers to these effects.