Chemical characteristics of BTEX, Formaldehyde and Trace gases: concentration, ozone formation potential and source apportionment at a campus site of Agra

Benzene, toluene, ethylbenzene, xylenes (BTEX) and formaldehyde (HCHO) impact the environment and human health due to their deleterious effect and are of great concern. In the present study, diurnal and seasonal trend of BTEX and HCHO along with trace gases are reported. BTEX samples were collected by activated charcoal tubes and analysed by Gas Chromatograph coupled with Mass Spectrometer and Flame Ionization Detector (GC–MS/FID) and formaldehyde sampling was done by impinger method and analysed by UV–Visible Spectroscopy. Summation BTEX varied from 50.3 to 188.3 µg m −3 (average = 74.8 ± 31.8 µg m −3 ). Amongst all species, toluene was the most abundant. Highest levels of BTEX, NO x and CO were observed in winter (96.4 ± 39.1 µg m −3 , 11.9 ± 7.8 ppb and 540.8 ± 402.0 ppb respectively) probably due to enhanced local emissions, stagnant weather conditions resulting in dilution and dispersion of pollutants and weak photochemical removal. Lower values are seen during monsoon (58.6 ± 25.4 µg m −3 , 7.6 ± 6.1 µg m −3 and 149.8 ± 68.7 µg m −3 ) as a consequence of rain showers and washout effect leading to clean atmospheric conditions. Further, ozone forming potential (OFP) BTEX was determined based on their reactivity with OH˙radical and concentration. Toluene (90.9 µg m −3 ) was the largest contributor to ozone formation, whereas benzene (9.1 µg m −3 ) was the lowest. Source apportionment of BTEX was determined based on estimation of diagnostic ratios, correlations and positive matrix factorization (PMF) analysis and revealed emissions from vehicles was the main source. Air mass back trajectory analysis for different seasons shows the impact of long-range during the summer season and localized air masses during winter season. The results of the current study provide a better understanding of OFP and sources of BTEX and HCHO to formulate effective pollution management.