Temporal Variation Characteristics of Negative Air ion Concentration and Air Quality Evaluation in Songshan National Nature Reserve, Beijing

Abstract: The aim of this study was to investigate the temporal characteristics of negative air ion concentration in the Songshan National Nature Reserve, Beijing. Hence, three typical forest stands and a nonforested land control group were selected during the growing season of May to October. The ion concentration was monitored using the Japanese COM-3200PRO negative air ion detector, and the air quality was evaluated using the amperometric air ion evaluation index method. The results showed that the diurnal variation of negative air ion concentration in the typical forest stands exhibited “double peak” curves, except for Betula dahurica forest in spring. The peak values of the annual growth season were attained between 9:00 and 11:00 as well as 16:00 and 17:00, and the trough value was attained at approximately 13:00. The monthly concentration variation characteristics in the stands showed “single peaks”, with the exception of the Juglans mandshurica forest. The negative air ion concentration was higher in July, August, and September both inside and outside the forest. The seasonal concentration variation characteristics showed that the negative air ion concentration inside and outside the forest followed the relation: summer (833±150 ion cm–3) > autumn (735±174 ion cm–3) > spring (632±178 ion cm–3). From the air quality evaluation, the average CI value of the forested land was 0.75±0.26, indicating that the air was clean. The average CI value of the nonforested land was 0.31±0.04; the air quality was within an acceptable range. Overall, the concentration of each stand followed the relation: Juglans mandshurica (0.83±0.11) > Tilia mongolica (0.74±0.10) > Betula dahurica (0.67±0.13) > nonforested land (0.31±0.04). Varied forest stands have different temporal characteristics for negative air ion concentration and air quality. Using forest resources wisely, it is possible to significantly enhance the air quality in the Songshan National Nature Reserve.