Characteristics and Sources of Volatile Organic Compounds during COVID-19 Outbreak in a Highly Industrialized City of China

Abstract:

The COVID-19 outbreak caused significant impact on social and industrial activities in China. During the lockdown period, primary emissions of air pollutants such as nitrogen oxides (NOx) dramatically reduced across cities, as revealed by satellite and surface observations. However, measurements of volatile organic compounds (VOCs) are seldom reported, hindering our understanding of ozone (O₃) variations during this unconventional time. Here, we analyze VOCs data measured at four air quality monitoring stations in the industrial hub of China - Dongguan city - to examine the changes in their sources and effects on O₃ production. From January 2019 to April 2020, sixteen consecutive months of VOCs online measurements provide a unique opportunity to distinguish the effects of city lockdown and Spring Festival holiday in China. VOCs compositions, chemical reactivity and source contributions are analyzed by comparing the entirely period of pre- and post-lockdown in 2020 and the 2019 counterpart. In addition to NOx decline, the concurrent drop of VOCs affects the O₃ variations differently during daytime and nighttime. The consequence of unintended emission reductions helps demystify the formation mechanism of O₃. This study will provide important implications for the policy-makers to formulate effective O₃ control strategy by precursors abatement in the highly industrialized areas.