Abstract: We observed PM_2.5 and negative air ion concentration in five different vegetation configuration structures and the entrance to the west side of the park (hard pavement, control site (CK)) in Chilechuan Park, Hohhot City. The observation was carried out at 07:00-19:00 across different seasons from 2020 to 2021, under sunny and partly cloudy weather conditions. We analyzed the change characteristics, influencing factors and interactive effects of pollution and negative air ions in the park. The results showed that PM_2.5 concentration of different configuration structures was the highest in autumn and the lowest in summer. The diurnal variation curve in spring showed a downward trend, with a “double peak and double valley” pattern in summer and winter, and a “single peak and single valley” pattern in autumn. In different seasons in the park, the daily variation of PM_2.5 concentration in sites of different vegetation configuration structures could reach or surpass the ambient air quality level II standard. Except for spring, the concentration of negative air ions at different sites with different vegetation configuration structures in various seasons was higher than that of the CK. The daily change of negative air ion concentration in spring and summer was roughly in a pattern of “low at noon, high in the morning and evening”, but a fluctuating trend in autumn and winter. The air ion evaluation index (CI) values of different seasons in the park were summer>autumn>winter>spring. The mean evaluation grades were all within the range of moderate (III) and allowable (IV) concentrations. The CI value of sites with multi-layer configuration structure was higher in different seasons. The correlation between negative air ion and PM_2.5 concentrations was different among seasons. The concentration of PM_2.5 was most significantly affected by air pressure, followed by temperature and relative humidity. The concentration of negative air ions was affected by wind speed, temperature, relative humidity and PM_2.5 concentration in different seasons, respectively.

Key words: urban park greenspace, PM_2.5 concentration, air anion concentration, variation characteristics, air quality.