Long-term trends of HCHO columns in Shanxi Province based on satellite remote sensing
The long-term trends of formaldehyde(HCHO)column in Shanxi Province from May to August over the period 2013~2022 were analyzed,using satellite measurements from Ozone Monitoring Instrument(OMI)and auxiliary data.The research examines the influence of biogenic volatile organic compounds(BVOCs)and anthropogenic volatile organic compounds(AVOCs)emissions on the observed variations in HCHO levels.Results indicate that the average HCHO column ranged from 4.1×1015 to 53.6x1015 molecules/cm2,with an annual mean of 14.3 × 1015 molecules/cm2.From 2013 to 2018,HCHO column exhibited an increasing trend,followed by a fluctuating decline from 2019 to 2022.Rural areas consistently showed higher HCHO concentrations compared to urban regions.After removing temperature effects,decreases in HCHO concentrations were observed mostly in urban areas with intense human activities,while increases were observed in rural villages with minimal anthropogenic influence.In temperature-sensitive regions,the rise in HCHO concentrations in northern Datong was attributed to increased BVOCs emissions from croplands.Similarly,in western Xinzhou to northern Lüliang,elevated HCHO concentrations were linked to higher BVOCs emissions from croplands,dense shrublands,mixed forests,and savannas.Conversely,central Jinzhong and southern Linfen to northern Yuncheng experienced reductions in HCHO concentrations due to simultaneous decreases in both AVOCs and BVOCs emissions,with reductions in AVOCs playing a particularly significant role.