A New GIS-based Approach for Spatially Allocating Regional Mobile Source Emission Inventories in the Pearl River Delta (PRD), China

摘要

Gridded emission inventories of air pollutants are perquisites for using air quality models to assess air pollution control strategies and predict air quality. A more precise gridded emission inventory will help improve the accuracy of air quality simulation. Mobile emissions sources are major contributors to VOC and NO_x pollutants, the precursors of ozone formation. However, because of the complexity of road networks and variations in traffic flows at different locations and road types, spatial allocation of emissions from mobile sources into grid cells is more challenging. The commonly used population based-approach has limitations that small counties or densely populated areas were given the majority of vehicle emissions regardless of their actual transportation networks, thus lead to the spatial bias in emission allocation. This paper propose a new GIS-based spatial allocation approach named as the "standard " length method, in which road lengths in the transportation networks are converted into "standard" lengths by weighting different road types using real-world traffic flow statistics. The "standard" length-based unit emission intensity along with GIS-based road network information is used to help allocate mobile source emission inventory into the grid cells. The approach has been demonstrated in spatial allocation of the Pearl River Delta regional emission inventories. The results show that spatial distributions of mobile source emissions using the new approach are well consistent with regional road network systems. It implies that the new approach is promising in reducing spatial bias in spatial allocation of emissions, and is believed that it will help improve air quality model simulation results, especially as the modeling grid cell size decreases.