Spatial distribution of negative air ions (NAIs) in urban green spaces of Nyingchi City, Tibet Plateau

Taking Nyingchi City as an example, this study explored the distribution of negative air ions (NAIs) in urban green spaces of plateau. Six representative areas of different types of urban green spaces in the main urban area of Nyingchi City were selected for NAIs observation and measurement. The results demonstrated that the NAI concentration in summer was significantly higher than the other three seasons in the study area. The NAI concentration in Fujian Park was significantly higher than the other observation sites, in the order of Fujian Park > the green space of Guangfu Avenue > Wetland Park of Happiness Community > the ecological scenic area of Biri Holy Mountain > Gala Peach Blossom Village > the scenic area of Cypress King’s Garden. Pearson’s correlation analysis showed that the NAI concentration was positively correlated with positive air ions and humidity, while humidity was positively correlated with NAIs and positive air ions, but negatively correlated with temperature and CO 2 concentration ( p < 0.05). The correlations between the other variables all have p > 0.05, indicating no statistically significant correlations among them. PCA analysis showed that the highest loading was positive ions with a value of 0.929, and the loading of humidity was −0.876, positively and negatively correlated, respectively.