Developing a vehicle emission inventory with high temporal-spatial resolution in Tianjin, China

The vehicle emission inventory is used to describe air pollutants from vehicles quantitatively. Many emission inventories have been developed using the top-down method in China; however, most have a low temporal-spatial resolution. This study utilized the top-down method to develop a vehicle emission inventory with high temporal-spatial resolution in Tianjin, China, a typical megacity experiencing severe vehicle pollution. The relationship between vehicle age and annual average vehicle kilometers travelled (VKT) was investigated by introducing the age-VKT curve, which indicated that the VKT decreased when vehicles get older. The emission estimation showed that light-duty passenger vehicles were the major contributors of carbon monoxide and volatile organic compounds, while heavy-duty passenger vehicles and heavy-duty trucks contributed significantly to nitrogen oxides and fine inhalable particles. China III standard vehicles were the main contributors to all pollutants. High-resolution gridded emissions were obtained using a practical allocation method, which showed that the spatial distributions differed slightly for each pollutant and the emissions changed significantly in a 24-h period. This study presented a comprehensive approach to developing a high-resolution emission inventory that can be utilized to assist in pollution control policy formulation.