基于车载CO_(2)/CH_(4)移动观测的城市站点空间代表性和热点识别研究

Spatial representativeness of urban observation sites and hotspot identification based on CO2/CH4 vehicle-carried mobile observations

基于车载激光气体分析仪于2020年冬季和2021年春季在杭州道路观测近地面大气CO_(2)和CH4浓度.结果表明:(1)城市不同区域道路近地面大气CO_(2)浓度与城市背景站差值(ΔCO_(2))的排序为工业区>商业居民混合区>沿江住宅区>自然风景区,而CH4差值(ΔCH4)的排序为沿江住宅区>商业居民混合区>工业区>自然风景区,这说明城市CO_(2)和CH4排放源有差异.(2)城市CO_(2)和CH4排放热点同一位置多次观测浓度均高于周边地区30%以上,且CO_(2)和CH4浓度昼夜差异明显.(3)杭州隧道内CH4:CO_(2)浓度比值为(0.000912±0.00002),表明杭州主城区车辆以汽油车为主.(4)在高度约为20~30m的高架处观测的CO_(2)浓度对于不透水面影响的空间代表范围半径为2100~3100m,普通路面近地面观测CO_(2)浓度对于植被覆盖影响的空间代表范围半径为1900~6100m,由此可见,2000m半径对于高密度组网观测来说是较为合理的布局间隔.

The road CO_(2)and CH4 concentrations in Hangzhou during 2020 winter and 2021 spring were observed using vehicle-carried laser gas analyzer.The results indicate that:(1)theΔCO_(2)magnitude(road surface atmospheric concentration minus urban background concentration)in different areas of the city was in the order of industrial area>commercial residential area>riverside residential area>natural scenic area,and theΔCH4was in the order of riverside residential area>commercial residential area>industrial area>natural scenic area,indicating that the CO_(2)and CH4 emission sources were different;(2)the atmospheric CO_(2)and CH4 concentrations were more than 30%higher near emission hotspots than in the surrounding areas,having obvious diurnal difference;(3)the CH4 and CO_(2)concentration ratio in Hangzhou tunnel was(0.000912±0.00002),suggesting that gasoline and diesel vehicles were dominant in Hangzhou;and(4)the observations of CO_(2)concentration from the viaducts with the heights of 20~30m can represent the impact of impervious surface within the radius from 2100 to 3100m,and the observations on ordinary roads can represent the impacts of vegetation within the radius from 1900 to 6100m.Obviously,the radius of 2000m is a suitable spatial interval for deploying high-density network observations.