Spatiotemporal distribution of negative air ion and PM2.5 in urban residential areas

Urban environments are characterised by high pollution levels, which adversely affect the physiology, psychology and behaviour of the urban residents. In this study, on-site measurements and air quality evaluations were performed in urban residential areas. The negative air ion (NAI) concentration, fine particulate matter (PM2.5) concentration, temperature and relative humidity were measured in different seasons. Both PM2.5 and the NAI concentrations changed significantly with seasons. The PM2.5 concentration was the highest in winter, intermediate in autumn and the lowest in summer, while the NAI concentration showed an opposite trend. The overall changes in NAI and PM2.5 concentrations showed a trend of double peaks and double valleys, and there was a substantial difference between rainy days versus sunny days. The NAI concentration was positively correlated with temperature and relative humidity, and the influence of relative humidity on NAI was greater than that of temperature. There were notable spatial differences in the intensity of impact by different pollution sources. Based on these results, suggestions were made for optimising the layout of residential buildings and the rationalisation of traffic networks, with the aim of increasing NAI concentrations and reducing PM2.5 concentrations. This would help reduce the pollution levels in urban residential areas.