The Variation And Main Affecting Factors Of Negative Air Ions In Different Ecological Lands Of Chongming Island In Shanghai

In order to obtain the real time trend and main affecting factors of negative air ions, an open environment which includes different types of ecological lands and different dominant tree species, and a controlled environment were chosen for study. On this basis, real time monitoring of negative air ions along with temperature, humidity, wind speed and light intensity has been done in chosen points. Meanwhile, the ion polarity ratio and air ion assessment index was used for air quality evaluation, and the Guassian model was for validating the order of mean negative air ions concentration.(1) There is a seasonal difference on the daily variation of negative air ions in different types of ecological land and different dominant tree species. During the daily variation of negative air ions, there is a obvious peak in morning in spring, summer and autumn, but the difference is the time the peak concentration appears.(2) In addition to winter, the negative air ions concentration of Taxodium ascendens is highest in all trees in other seasons, the concentration of Camphor is highest only in winter, the concentration of mixed forest is in the middle level, and there is a difference in different tree species.In different ecological lands, the negative air ions concentration of wetland is hightest in summer and lowest in spring, but the concentration of other lands is hightest in winter and lowest in autumn. Meanwhile, there is a difference between greenbelt, wetland and control point (p<0.05).The frequency distribution and Guassian model show that the order of the expectations is almost same as the order of the mean concentration.(3) The annual average concentration of negative air ions in different ecological lands is in the order of wetland>woodland>greenbelt>control point. The concentration of wetland is significantly higher than that of others, and the concentration of control point is significantly lower than others (p<0.05). The annual average concentration of negative air ions in different dominant tree species is in the order of Taxodium ascendens forest> mixed forest> Ailanthus altissima forest> Metasequoia glyptostroboides forest> Camphor forest.(4) There is a positive correlation between negative air ions concentration and tree height, humidity, the area of Greenland and water. There is a negtive correlation between negative air ions concentration and temperature, the area of hard groud. In summer, there is a positive correlation between negative air ions concentration and light intensity when light intensity is less than 40000 lux, but no obvious increase when light intensity is more than 400001ux.(5) There is a negative correlation between negative air ions concentration and temperature, and a positive correlation between negative air ions and humidity. Plant is beneficial to the increase of negative air ions concentration. In the artificial climate box, the ventilation has a great influence on the negative air ions, and the static environment is more helpful to generate and accumulate negative air ions.