Revealing the characteristics of long-term Chinese tropospheric formaldehyde under the influence of socio-natural sources

Monitoring the spatiotemporal distribution of formaldehyde (HCHO) is crucial for reducing volatile organic compounds (VOCs) emissions, and the long-term evolution of socio-natural sources contributions to tropospheric HCHO over China is still unclear. We propose an oversampling algorithm for quantitatively tracking the evolution of uncertainty, which lowers the uncertainty of the original Level 2 OMI HCHO data (50% -105%) to 0-50%, and then we examine the evolution of contributions from various emissions sources applying multi-scale correlation. We found that the high formaldehyde emissions caused by human activities in eastern China are crossing the Hu Huanyong Line, which was formerly used to demarcate the population distribution. National-scale analysis indicate that HCHO emissions are significantly correlated with per capita Gross Domestic Product (per capita GDP) (r = 0.948) and Normalized Difference Vegetation Index (r = 0.864), while no substantial correlation with land surface temperature (LST) (r = 0.233). Diagnosis at pixel scale reveals that anthropogenic emissions continue to weaken the contributions of HCHO emissions caused by the increase in vegetation proportion. Our research identifies the evolutionary process and characteristics of the spatiotemporal distribution and socio-nature sources contributions of tropospheric formaldehyde of China from 2005 to 2022.