Assessment of motor vehicle emission control policies using Model-3/CMAQ model for the Pearl River Delta region, China

In recent decades, the Pearl River Delta (PRD) region located in south China has been experiencing severe air pollution, arising from the rapid increase in industry and motor vehicles. As a major contributing source to VOCs and NO_x emissions, control of vehicular emissions plays a very important role in improving regional air quality. By taking 2015 as a target year, this paper assessed the impacts of five possible motor vehicle emission control measures and a combined policy scenario on ambient air quality in the PRD region, with the use of the Model-3/CMAQ (Community Multi-scale Air Quality) model. The results show: (1) an overall decreasing pattern in SO₂, NO₂ and PM₁₀ concentrations was found in central-south metropolitan areas of the PRD region for all measures, but increased O₃ concentrations may occur in these areas as well. The exception to this is that a slight decrease was observed for the cases of motorcycle restriction and introduction of HEV; (2) upgrading to National IV emission standards is the most effective individual measure and can reduce daily averaged NO₂ and PM₁₀ concentrations by 11.7ppbV and 21.3μgm^-3, respectively; but involves an increase (at maximum) of 10.3ppbV in O₃ concentration. Evaluation of the combined scenario indicates that solely controlling motor vehicle emissions is not sufficient to improve PRD regional air quality significantly. O₃ and PM₁₀ concentrations under the same VOC/NO_x reduction ratios exhibit differently at different locations, suggesting that integrated and location-specific pollution control strategies, considering co-control of multi-pollutants, are needed in this region in order to decrease primary and secondary pollutant concentrations simultaneously.