부산대학교 도서관

Several anthropogenic (like industries, vehicles, coal-based thermal power plants, etc.) and natural sources (like lightning, degradation of organic matter, etc.) emit a copious amount of primary gaseous pollutants like Sulphur dioxide (SO2), Nitrogen dioxide (NO2) and Ammonia (NH3), which further contribute in the formation of particulate matters where they are present in the form of water-soluble inorganic ions (WSII) like SO42−, NO3−, NH4+, respectively. To assess the conversion of primary gaseous pollutants into dissolved ions in PM10, real-time sampling (24 h average) of PM10and primary gaseous pollutants (SO2, NO2, NH3) from September 2021 to March 2022 over 13 highly polluted places in Kolkata were performed. Then PM10was quantified using the gravimetric method, while NO2and NH3were estimated through chemiluminescence and SO2was estimated through the fluorescent spectrometric method. Analysis of WSII species in PM10was also performed through the spectrophotometric method and then to understand the conversion of the primary gaseous pollutants into WSIIs in PM10, sulphur oxidation ratio (SOR) and nitrogen oxidation ratio (NOR) and ammonia conversion ratio (NHR) was calculated. The results showed that NO2is the most abundant primary gaseous pollutant in the ambient air of Kolkata [highest in Dumdum (73.6 μgm−3)] and NO3–is the most abundant WSII in PM10of Kolkata [highest in Bansdroni (3.74 μgm−3)] and the SOR and NOR values were significantly higher in Bansdroni and NHR was significantly higher in Santoshpur due to presence of optimum meteorological conditions. Lightning is one of the major natural sources of NOx. So, due to lightning, atmospheric NOx level increases which then gets associated with particulate matter, increasing the concentration of NO3−ion in particulate matter due to gas-particle partitioning. This is indicated by strong linear correlation coefficients (R2= 0.746) between a number of flashes on the day of sampling and NO3−concentration in PM10aerosol.