This study inspects the concentrations
of fine particulate matter
(PM2.5) mass and carbonaceous species, including organic
carbon (OC) and elemental carbon (EC), as well as their thermal fractions
in the Indian Himalayan glacier region at the western Himalayan region
(WHR; Thajiwas glacier, 2799 m asl), central Himalayan region (CHR;
Gomukh glacier, 3415 m asl), and eastern Himalayan region (EHR; Zemu
glacier, 2700 m asl) sites, throughout the summer and winter periods
of 2019–2020. Ambient PM2.5 samples were collected
on quartz fiber filters using a low-volume sampler, followed by carbon
(OC and EC) quantification using the IMPROVE_A thermal/optical reflectance
methodology. Different seasonal variations in PM2.5 and
carbonaceous species levels were found at all three sites investigated.
Averaged PM2.5 mass ranged 55–87 μg m–3 with a mean of 55.45 ± 16.30 μg m–3 at WHR, 86.80 ± 35.73 μg m–3 at CHR, and 72.61 ± 24.45 μg m–3 at
EHR. Among the eight carbon fractions, high-temperature OC4 (evolved
at 580 °C in the helium atmosphere) was the most prevalent carbon
fraction, followed by low-temperature OC2 (280 °C) and EC1 (580
°C at 2% oxygen and 98% helium). Char-EC representing incomplete
combustion contributed to 56, 67, and 53% of total EC, whereas soot-EC
contributed to 38, 26, and 43% of total EC in WHR, CHR, and EHR, respectively.
The measured OC/EC ratios imply the presence of secondary organic
carbon, whereas char-EC/soot-EC ratios suggested that biomass burning
could be the predominant source of carbon at CHR, whereas coal combustion
and vehicular emission might be dominant sources at WHR and EHR sites.
reported studies, the order of occurrence of BTEX compounds was toluene > benzene > xylene isomers > ethylbenzene and winter had higher concentrations than in other seasons, including summer. As far as BTEX levels in classified areas of urban environments are concerned, traffic locations have shown the highest BTEX concentrations, followed by residential, commercial, and industrial locations. OFP indicated that xylene isomers and toluene contributed to ozone formation. The major gaps in reported studies on BTEX measurement are (1) source apportionment;(2) impact on lower tropospheric chemistry, human health, and climate change; and (3) removal techniques from air.
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