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Environ Pollut

Title:		Contribution of biogenic and photochemical sources to ambient VOCs during winter to summer transition at a semi-arid urban site in India
Author(s):		Sahu LK; Tripathi N; Yadav R;
Address:		"Physical Research Laboratory (PRL), Navrangpura, Ahmedabad, 380009, India. Electronic address: lokesh@prl.res.in. Physical Research Laboratory (PRL), Navrangpura, Ahmedabad, 380009, India"
Journal Title:		Environ Pollut
Year:		2017
Volume:		229
Issue:
Page Number:		595 - 606
DOI:		10.1016/j.envpol.2017.06.091
ISSN/ISBN:		1873-6424 (Electronic) 0269-7491 (Linking)
Abstract:		"This paper presents the sources and characteristics of ambient volatile organic compounds (VOCs) measured using PTR-TOF-MS instrument in a metropolitan city of India during winter to summer transition period. Mixing ratios of VOCs exhibited strong diurnal, day-to-day and episodic variations. Methanol was the most dominant species with monthly mean values of 18-22 pbbv. The emission ratios of VOCs relative to benzene calculated from nighttime data were used to estimate the relative contributions of vehicle exhaust and other sources. The increasing daytime ratios of oxygenated-VOCs (OVOCs)/benzene and isoprene/benzene from February to March indicates increasing contribution of photo-oxidation and biogenic sources. Daytime fractions of acetone (18%), acetaldehyde (15%) and isoprene (4.5%) to the sum of measured VOCs in March were higher than those in February. Variations of VOCs at lower temperatures (<25 degrees C) were predominantly controlled by anthropogenic sources. At high temperatures, particularly in the range of 32-40 degrees C during March, levels of OVOCs and isoprene were influenced by biogenic emissions. The emissions of OVOCs from vehicle exhaust were estimated to be smaller (20-40%) than those from other sources. The contributions of biogenic and secondary sources to OVOCs and isoprene increased by 10-15% from winter to summer. This study provides evidence that the winter-to-summer transition has an impact on sources and composition of VOCs in tropical urban areas"
Keywords:		Air Pollutants/*analysis Benzene Butadienes Cities *Environmental Monitoring Hemiterpenes India Pentanes Photochemical Processes Seasons Vehicle Emissions/analysis Volatile Organic Compounds/*analysis Biogenic Ptr-tof-ms Topical India Urban VOCs Winter-su;
Notes:		"MedlineSahu, L K Tripathi, Nidhi Yadav, Ravi eng England 2017/07/10 Environ Pollut. 2017 Oct; 229:595-606. doi: 10.1016/j.envpol.2017.06.091"