Analysis of pollutant distribution based on taxi travel volume: a case comparison of Xi’an and Ningbo, China

With rapid social and economic development, the amount of traffic in China has gradually increased, so as the traffic-generated pollution, which has caused serious influence to the environment and the public health. In this paper, Xi'an, a typical city in the northwest China, and Ningbo, another typical in the southeast, have been selected to analyze the impact of traffic on environmental pollution to solve environmental problems. In the analysis, the GPS taxi data and pollutant concentration data of national environmental monitoring points of 7 days in Xi'an and Ningbo are used respectively. Spatial-temporal characteristics and the high and low value cluster analysis of the taxi data and pollutant concentration are carried out using spatial interpolation, kernel density analysis, and clustering. The results show that the peak of taxis data coincides with the extremely high concentration of 6 pollutants. The concentration of the pollutants reaches peak level at 9 o'clock, and begins to drop sharply at 12 o'clock. The ozone has an opposite trend with other pollutants, which may be related to the concentration of nitrogen oxides and have a titration effect on the ozone. The hotspot areas of taxi data are highly coincident with the spatial distribution of pollutants, which mainly locate in Xi'an and Ningbo downtown areas. The taxi data and pollutant data have high similarity in the high and low value clustering results. In addition, it has been found that the traffic restriction policy has a certain effect on reducing pollutant concentration. And the study also shows that corresponding pollutant concentration in Xi'an is significantly higher than that in Ningbo, which has a great relationship with the population, economy, climate and travel habits of the two regions. Therefore strengthened management on traffic restrictions, purchase restrictions as well as traffic in Xi'an is advocated. Altogether, this study may provide technical support to the relevant decision making.