[A-AS09] Atmospheric Chemistry

[AAS09-P19] Seasonal variation of Volatile organic compounds and ozone formation potential at an urban site of Delhi, India

*Pooja Yadav^1,2, Shyam Lal³, Tuhin Kumar Mandal^1,2 (1.CSIR- National Physical Laboratory, Dr. K.S. Krishan Marg, New Delhi, India, 110012, 2.Academy of Council of Scientific Industrial Research, Ghaziabad, India , 3.Physical Research Laboratory, Ahmedabad, India )

Keywords:Volatile organic compounds, Seasonal variation, Gas chromatograph , Ozone formation potential

Volatile organic compounds (VOCs) are a wide variety of organic compounds found in the air and have a substantial effect on the environment, human health, and air quality. They contribute to the generation of secondary organic aerosols, act as precursors to pollutants like ground-level ozone, and influence climate change. To understand the atmospheric chemistry of VOCs we did the measurement of 25 VOCs categorised into 4 groups alkanes, alkenes, alkyne, and aromatics at CSIR- NPL, New Delhi from February 2022- February 2023. Measurement of VOCs was done at intervals of 2 hours by the Gas Chromatograph – Flame Ionisation Detection (GC-FID) coupled with Thermal Desorber (TD). Firstly, we estimated the composition, diurnal variation, seasonal variation of VOCs, and then the seasonal variation of ozone formation potential (OFP). The total average concentration of all VOCs was 163.79 ± 165.16 ppbv and in winter, pre-monsoon, monsoon, and post-monsoon 157.96 ± 152.22 ppbv, 205.51 ± 199.48 ppbv, 100.35 ± 50.75 ppbv, and 233.85 ± 215.50 ppbv respectively. Alkanes had the highest contribution to the total VOCs 61.12% followed by alkenes 22.40%, aromatics 11.39%, and alkyne 5.19%. Alkanes had the highest dominance over the total VOCs in all the seasons. Diel pattern of VOCs revealed that they have high concentration during night-time and less concentration during the daytime as they take part in the complex chemical reaction of ozone formation. 1-hexene had exceptional diurnal behaviour during the study time because it had high concentration during the day time and less during the day time. The total ozone formation potential of all VOCs was 329.01 ppb and in season winter, pre-monsoon, monsoon, and post-monsoon were 373.93 ppbv, 547.88 ppbv, 312.35 ppbv, and 542.88 ppbv respectively. High ozone formation during the pre-monsoon was associated with meteorological conditions like sunny and warm weather and low relative humidity.