Investigating the Heterogeneity of NOx-VOCs-Ozone Relationships in Chinese Cities: Systematic Assessment and Spatiotemporal Maps

Abstract

Abstract Ozone is a pollutant threatening the atmospheric environment and public health. Investigating the relationship and sensitivity between ozone level and its precursors, including nitrogen oxides (NOx) and volatile organic compounds (VOC), has been a significant basis and reference for pollution mitigation. Through mining the internal comparability between individual data and the entire dataset, this study develops indexes assessing the ozone-NOx-VOC relationship while performing a case study on Chinese cities from 2015 to 2020. From the results, (1) the ozone-precursor correlation in Chinese cities generally showed increase-decrease trends in the assessing period while significantly correlating cities aggregating in two eastern city groups. (2) Differentiation in NOx- and VOC-limited ozone production regimes between cities located on the left and right sides of the Hu Huanyong Line has gradually formed over the past several years. (3) To effectively and efficiently mitigate ozone pollution, reducing NOx emission on a large scale while preventing VOC emission in key urban agglomerations with relatively developed economies and aggregated populations is recommended. The ozone-NOx-VOC relationship is assessed based on the quantitative and individual evaluation of ozone-NOx and ozone-VOC correlation, providing a novel local-to-global perspective to understand the contribution of precursors to ozone pollution.