The variation characteristics of atmospheric CH4 mixing ratio observed in the middle and lower reaches of the Huai River
Based on the atmospheric CH4 mixing ratios from the high-precision greenhouse gas monitoring station in Wuhe,Anhui Province in 2023,as well as the concurrent meteorological observation data,this study investigated the CH4 mixing ratio variation characteristics,transport influence,and potential emission source distribution characteristics in the typical underlying surface conditions of the middle and lower reaches of the Huai River.The results show that the CH4 mixing ratios with regional representativeness is(2113.0±1.9)×10-9,which is significantly lower than the CH4 mixing ratio affected by local conditions near the monitoring station((2417.4±9.9)×10-9).The CH4 mixing ratios in the Wuhe area exhibits a peak-trough feature with higher levels in the morning and lower levels in the afternoon in different seasons,and a unimodal feature with higher levels in summer and lower levels in winter.The difference in CH4 mixing ratios between the lower layer(50 m)and the upper layer(80 m)is small during the day and large at night.The ground wind has asignificant impact on the CH4 mixing ratios in the Wuhe area,which is easily influenced by the southwest sector airflow and increases;the CH4 mixing ratios decrease with the increase of wind speed.Backward trajectory and potential source analysis indicate that the emission areas are mainly distributed in the four provinces of Central China(Anhui,Henan,Hubei,Jiangxi),Jiangsu Province,and Shandong Province,where there are a large number of wetlands,paddy fields,and livestock production bases,all of which are the main factors affecting the increase of CH4 mixing ratios in the typical representative areas of the middle and lower reaches of the Huai River.
the middle and lower reaches of the Huai RiverCH4variation of mixing ratiospotential emission sources
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