Effects of anthropogenic emissions and meteorological conditions on diurnal variation of formaldehyde (HCHO) in the Yangtze River Delta, China

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Formaldehyde (HCHO) plays an important role in the troposphere, as it is a major precursor of ozone and heavily affects the health of lives on the earth. However, to the present, major factors that influence the diurnal variation of HCHO in the Yangtze River Delta (YRD) of China have not been investigated thoroughly. Moreover, sensitivities of the HCHO concentration in cities of YRD to the primary anthropogenic emissions of these cities are also unclear. Thus, we used a mesoscale meteorological model coupled with chemistry, WRF-Chem to capture the variation of HCHO in ten cities of YRD, so that the factors dominating the diurnal change of HCHO in these cities can be identified. We also performed sensitivity tests by varying the primary anthropogenic emission intensity of HCHO, to investigate the sensitivity of HCHO in each city to primary anthropogenic emissions of HCHO. The simulation results showed that the driving factors for the daytime peak of HCHO include photochemical reactions and VOCs＋OH reactions. The change in meteorological conditions causes a deviation of the temporal evolution of HCHO in many cities of YRD from the conventional trend (i.e., peak at noon and low in the rest). The major impact areas of HCHO anthropogenic emissions from the cities of YRD and the contributions to HCHO in these cities were also revealed.