Is the effect of human activity on air pollution linear or nonlinear? Evidence from Wuhan, China, under the COVID-19 lockdown

《Is the effect of human activity on air pollution linear or nonlinear? Evidence from Wuhan, China, under the COVID-19 lockdown》

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作者: Lu Liu;Qiuyun Wang

来源: CITIES,Vol.127,Issue1,Article 103752

语言: 英文

关键字: Air quality;COVID-19;Human activity;Lockdown;Wuhan

作者单位: School of Economics, Southwestern University of Finance and Economics, China;School of Economics, Southwestern University of Finance and Economics, China

摘要: This study explores the fundamental question of how and how much human activity affects air quality. It focuses in particular on whether this relationship is linear or nonlinear and provides suggestive results to the intriguing mechanism. To determine that answer, we make two important assumptions about the impact of human activity on air quality that we then test using a new analytical framework. In early 2020, the period of lockdown in Wuhan, China, due to the COVID-19 pandemic offers “extreme” observations with which we can test our assumptions from the perspective of either differences or ratios. In addition to offering a theory with a novel design, we also introduce statistical methods that are suitable for empirically estimating and testing our assumptions and obtaining suggestive results. Moreover, we construct a precise equation in quadratic form for examining the marginal effects of several types of air quality indicators/metrics concerning human activity as well as some important control variables for both natural and social factors. The level of human activity, measured as the index of travel intensity, that has the largest effect on air quality is around 1.657 for the most common urban air pollutants. This study implies that urban air quality can be improved more effectively by avoiding regions where human activity has the maximum marginal effect on increases in urban air pollution. This implication for urban policy and planning is valuable both domestically and globally.