Seasonal Variation and Sources of Carbonaceous Species and Elements in PM2.5 and PM10 Over the Eastern Himalaya

Abstract

The study represents the seasonal characteristics (carbonaceous aerosols and elements) and contribution of prominent sources PM2.5 and PM10 in the high altitude of the eastern Himalaya (Darjeeling) during August 2018-July 2019. Carbonaceous aerosols [organic carbon (OC), elemental carbon (EC) and water soluble organic carbon (WSOC)] and elements (Al, Fe, Ti, Cu, Zn, Mn, Cr, Ni, Mo, Cl, P, S, K, Zr, Pb, Na, Mg, Ca, and B) in PM2.5 and PM10 were analyzed to estimate their possible sources. The annual average concentration of PM2.5 and PM10 were computed as 37±12 µg m-3 and 58±18 µg m-3, respectively. In the present case, total carbonaceous species in PM2.5 and PM10 were accounted for 20.6% of PM2.5 and 18.6% of PM10, respectively. Whereas, trace elements in PM2.5 and PM10 were estimated as 15% of PM2.5 and 12% of PM10, respectively. Monthly are seasonal variations in concentrations of carbonaceous aerosols and elements in PM2.5 and PM10 were also observed during the observational period. The positive relationship between OC & EC and OC & WSOC of PM2.5 and PM10 during all the seasons (except monsoon in case of PM10) indicate rheir common sources. The enrichment factors (EFs) and significant positive correlation of Al with othe crustal elements (Fe, Ca, Mg and Ti) of fine and coarse mode aerosols indicates the influence of mineral dust at the Darjeeling. Principal component analysis (PCA) resolved the four common sources (biomass burning + fossil fuel combustion (BB+FFC), crustal/soil dust, vehicular emissions (VE) and industrial emissions (IE)) of PM2.5 and PM10 in Darjeeling.

Year-long evaluation of aerosol chemistry and meteorological implications of PM2.5 in an urban area of the Brahmaputra Valley, India

“…29 While primary organic carbon (POC) was calculated using each season's minimum OC/EC ratio. 30 SOC and POC were estimated by the EC-tracer method using the following equations. 31,32 (3) 𝑆𝑂𝐶 = 𝑂𝐶 -𝑃𝑂𝐶 Where, OC QF is the quartz front filter OC, OC QBQ is the quartz behind quartz filter OC, and OC bQF is the field blank OC from the quartz front filter.…”

“…28 Secondary OC was estimated by subtracting primary OC from OC. 29 While primary organic carbon (POC) was calculated using each season's minimum OC/EC ratio, 30 SOC and POC were estimated by the EC-tracer method using the following equations. 31,32…”