Understanding the origin of carbonaceous aerosols during periods of extensive biomass burning in northern India

摘要

This study explores the PM_(2.5) (particulate matter with aerodynamic diameter ≤2.5 μm) emissions during various time periods (pre-monsoon, monsoon, and post-monsoon) over the biomass burning source region in Beas, Punjab. The PM_(2.5) concentrations during the pre-monsoon period (106-458 μg/m~3) and the post-monsoon period (184-342 μg/m~3) were similar but much higher than concentrations during the monsoon season (23-95 μg/m~3) due to enhanced wet deposition. However, the carbonaceous aerosol fraction in PM_(2.5) was nearly double in the post-monsoon season (～27%) than in the pre-monsoon period (～15%). A higher contribution of secondary organic carbon (SOC) observed during the pre-monsoon season can be attributed to enhanced photochemical activity in dry conditions. The concentration of carbon fractions in sampled sources and aerosols suggests contribution of biofuels,resultinginenhancedPMconcentration at this location. δ~(13)C_(TC) values of pre- and post-monsoon samples show dominance of freshly emitted aerosols from local sources. Impact of biomass and biofuel combustion was also confirmed by biomass burning K~+_(BB) tracer, indicating that major agriculture residue burning occurred primarily during night-time. C_3 plant derived aerosols dominated at the sampling location during the entire sampling duration and contributed significantly during the pre-monsoon season. Both fossil fuel and C_3 plant combustion contributed to the total mass of carbonaceous aerosols during the post-monsoon and monsoon seasons.