VOCs Over Himalayan Glaciers: Speciation, Sources and Comparison with Other Glaciers

This study presents the concentration and speciation of VOCs over three high-altitude Himalayan glacier regions {Western Himalayan region (WHR; Thajiwas glacier, 2799 m asl), central Himalayan region (CHR; Gomukh glacier, 3415m asl) and eastern Himalayan region (EHR; Zemu glacier, 2700 m asl)} along with their comparison with those reported over Arctic and Antarctic glacier regions. 28 VOCs were determined in ambient air samples, collected in sorbent tubes using a ACTI -VOC low flow pump sampler, throughout the summer and winter periods of 2019-2020, followed by analysis using thermal desorption gas-chromatography mass spectrometry (TD-GC-MS/MS). The average sums of 28 VOCs were found to be 161.58 µg.m^-3 at CHR, 120.73 µg.m^-3 at EHR and 94.33 µg.m^-3 at WHR. These values are found to be 4 to 40 fold and 0.8 to 2 fold higher than those reported over Arctic and Antarctic glaciers. On comparing these findings with those reported for an urban-industrial location of India (Raipur, Chhattisgarh) with similar period of measurement campaigns, a 2-fold lower concentration is observed over Himalayan glaciers. The results, also, indicated that CHR site has higher concentration of VOCs compared to other two sites WHR and EHR. Evaluation of seasonal variation pattern across the sites and source characterization by PMF5.0 were also made. UNMIX output of three-factor solution that explain >90% ambient VOC’s measurement is found to be similar to those of three source-factor solution from PMF5.0. The results revealed that three VOCs source types were: vehicle engine exhausts, biomass burning and coal combustion and biogenic emissions. The findings have important implications for appropriately assessing the effects of VOCs on glacial melting in high-altitude Himalayan glacier regions.

Keywords: Ambient VOCs, Seasonal variability; Himalayan glacier region, Source identification