CHARACTERIZATION, SOURCE IDENTIFICATION AND INVESTIGATION OF EFFECT OF WEATHER PARAMETERS ON ATMOSPHERIC TRANSFORMATION OF BLACK CARBON (BC) AND BROWN CARBON (BrC) AT A RURAL SITE IN INDO-GANGETIC PLAINS (IGP) REGION

Abstract

Carbonaceous aerosols Black Carbon (BC) and Brown Carbon (BrC) have significant impact of radiative forcing and influence climate system. BC can be emitted from combustion of fossil fuels and biofuels while primary source of BrC is biomass burning, and it can be constrained through atmospheric processes. However, how weather parameters like humidity (RH), temperature and solar radiation (SR) influence atmospheric processes of BC, BrC is not fully understood. Indo Gangetic Plains (IGP) region with high population density is a major source region for BC and BrC and have been facing major pollution problems like formation of atmospheric brown carbon. This study investigates sources, characteristics, atmospheric processes of BC and BrC and influence of weather parameters. Study is based on the yearlong data collected at Indo-Gangetic Plains Centre for Air Research and Education (IGP-CARE); monitoring station located in rural part of IGP region. Seasonal variation in BC and BrC was observed with higher concentration during winter and autumn. Monsoon season was characterized by very low BC, BrC most likely attributed to a wash effect. Summer season showed moderated BC and low BrC indicating fossil fuel combustion as source of emission and or long-term transport of particles from traffic emission or industrial emission. Solar radiation during winter and summer showed significant influence on BrC, indicating presence of photosensitive BrC. Nighttime changes of BrC were mostly attributed to the RH along with other atmospheric factors. During study period 10 episodic events of high concentration of BrC were identified and investigated. Evening and morning time peaks of BC and BrC observed indicates the biomass burning and emission of primary BrC along with BC. Freshly emitted BrC from local biomass burning was hyper-photosensitive compared to nighttime aged and atmospherically processed BrC. Study of change in BrC/BC ratio indicated influence of RH on atmospheric processes of BrC and likely, it negatively influenced the photosensitivity of the atmospheric BrC. Future studies should focus on the analysing effect of RH, temperature, and solar radiation on aging of BC, BrC along with different source materials, to better understand atmospheric processes of BC, BrC.