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摘要
A method for directly measuring carbon dioxide (CO2) emissions using a mobile sensor network in cities at fine spatial resolution was developed and tested. First, a com-pact, mobile system was built using an infrared gas analyzer combined with open-source hardware to control, georeference, and log measurements of CO2 mixing ratios on ve-hicles (car, bicycles). Second, two measurement campaigns, one in summer and one in winter (heating season) were carried out. Five mobile sensors were deployed within a 1x12.7 km transect across the city of Vancouver, BC, Canada. The sensors were operated for 3.5 h on pre-defined routes to map CO2 mixing ratios at street level, which were then averaged to 100 x 100m grid cells. The averaged CO2 mixing ratios of all grids in the study area were 417.9 ppm in summer and 442.5 ppm in winter. In both campaigns, mixing ratios were highest in the grid cells of the downtown core and along arterial roads and lowest in parks and well vegetated residential areas. Third, an aerodynamic resistance approach to calculating emissions was used to derive CO2 emissions from the gridded CO2 mixing ratio mea-surements in conjunction with mixing ratios and fluxes collected from a 28 m tall eddycovariance tower located within the study area. These measured emissions showed a range of 12 to 226CO(2) ha 1 h 1 in summer and of -14 to 163 kgCO(2) ha 1 h 1 in winter, with an average of 35.1 kgCO(2) ha (-1) h (-1) (summer) and 25.9 kgCO(2) ha 1 h 1 (winter). Fourth, an independent emissions inventory was developed for the study area using buildings energy simulations from a previous study and routinely available traffic counts. The emissions inventory for the same area averaged to 22.06 kgCO(2) ha (-1) h (-1) (summer) and 28.76 kgCO(2) ha (-1) h (-1) (winter) and was used to compare against the measured emissions from the mobile sensor network. The comparison on a grid-by-grid basis showed linearity between CO2 mixing ratios and the emissions inventory (R (2) =53 in summer and R (2) = 47 in winter). Also, 87% (summer) and 94% (winter) of measured grid cells show a difference within +/- 1 order of magnitude, and 49% (summer) and 69% (winter) show an error of less than a factor 2. Although associated with considerable errors at the individual grid cell level, the study demonstrates a promising method of using a network of mobile sensors and an aerody-namic resistance approach to rapidly map greenhouse gases at high spatial resolution across cities. The method could be improved by longer measurements and a refined calculation of the aerodynamic resistance.
- 出版日期2017-3-1
