Vertical distribution characteristics of atmospheric VOCs in Shenzhen based on tower observation

From August to September 2018, Using 11vertical gradient platforms of Shenzhen meteorological gradient observation tower, nine rounds of volatile organic compounds (VOCs) stainless steel canisters sampling were carried out, and 103kinds of VOCs were quantitatively analyzed by gas chromatography-mass spectrometry (GC/MS), to study the VOCs composition characteristics at different vertical heights and its impact on near surface ozone (O3) formation. The results shown that the total volatile organic compounds (TVOCs) pollution level from the ground to 345m altitude was similar, and there was little change in the vertical gradient; however, the concentration of alkenes decreased with the increase of altitude, which was dominated by isoprene emitted from biogenic sources on the ground. Combined with the analysis of typical species and species pairs, it was found that the secondary formation, industrial emission and photochemical reaction consumption were the main reasons for the change of VOCs concentration on the vertical gradient. Using mixed layer gradient method to calculate VOCs flux, it was found that alkanes (28%) and aromatics (23%) contributed the most; dichloromethane (1.93±0.29) mg/(m2·h) and toluene (1.86±0.39) mg/(m2·h) had higher vertical flux. Combined with the analysis of the relationship between the vertical profiles of nitrogen dioxide (NO2) and O3, it was concluded that the peak value of TVOCs/NO2 above 300m was more conducive to the O3 formation, which was one of the important reasons for the O3 peak value above 300m. © 2023 Chinese Society for Environmental Sciences. All rights reserved.