Temporal And Spatial Characteristics Of Negative Air Ions

This paper systematically discusses the spatiotemporal dynamic characteristics of NAI?Negative air ion?distribution,by taking three places in Zhejiang Province as the research area,which ZAFU?Zhejiang Agriculture and Forestry University?is the main area,and ZAFU,forest scenic spots in Shengzhou and islands in Zhoushan each represent the urban ecosystem,forest scenic area and island environment.In 2018,we selected sampling points near the campus of ZAFU to discuss the distribution of NAI in the four typical functional areas of traffic roads,farmland,residential cultural and educational areas,and ecological land.At the same time,NAI concentration,meteorological factors and environmental pollution factors in four seasons and different weather conditions were monitored at ZAFU to analyze the temporal and spatial variation of NAI concentration and its correlation with meteorological factors and environmental pollution factors.In 2016-2018,four forest scenic spots in Shengzhou were monitored to analyze the difference of NAI concentration in different seasons and the difference of NAI concentration between four forest scenic spots in each season.In the summer of 2018,the NAI concentration monitoring was carried out on the three islands of Zhujiajian,Taohuadao and Liuhengdao in Zhoushan,and the differences in NAI concentration between different islands in summer were analyzed.?1?Under different weather conditions?sunny,cloudy,rainy and snowy days?,the daily variation of NAI concentration in ZAFU showed a pattern of low NAI concentration during the day and high at night.In the early morning and evening,the haze is severe,and the daily variation of NAI concentration shows a pattern of low NAI in the morning and late night,while high at noon.There is a significant difference in NAI concentration between foggy weather,sunny days,cloudy,rainy days and snowy weather which shows the law of thunderstorm days>?rainy days>sunny days and snowy days?>?cloudy days,haze days?.?2?The seasonal variation of NAI concentration is as follows,the difference of NAI concentration between different seasons of ZAFU is significant,showing that summer>autumn>spring>winter,and the NAI concentration level is significantly different between the four seasons in Shengzhou forest scenic spots,summer>?spring,autumn?>winter,there is no significant difference in NAI concentration between summer and autumn.?3?The number of days of fresh air is assessed by the NAI concentration,and the proportion in different months is as follows.Overall,the proportion of fresh air days at ZAFU in summer is the highest,followed by autumn.Among them,due to continuous precipitation throughout February 2019,the NAI concentration level is higher,while actually the winter season?December 2018,January 2019?has a lower proportion of fresh air days.Compared with January,the NAI concentration level began to rise in spring?March 2019?,and the proportion of fresh air days increased.?4?In the different functional areas of ZAFU in autumn,the general rule of NAI distribution is:ecological land>residential culture and education office area>farmland>traffic road;the general rule of NAI distribution in ecological land is:coniferous and broad-leaved mixed forest>evergreen broadleaf Mixed forest with deciduous broadleaf>bamboo forest.And there is no significant difference in NAI concentration in Shengzhou four forest scenic spots in different four seasons.And in summer,there is a significant difference in NAI concentration between the three islands of Zhujiajian,Taohua Island and Liuheng Island in Zhoushan,Zhujiajian>Taohua Island>Lihengdao Island.?5?The correlation between NAI concentration and meteorological factors is as follows:there is no significant positive correlation between temperature and NAI concentration,and there is a significant positive correlation between air relative humidity and NAI concentration,and there is a significant negative correlation between light intensity and NAI concentration.There is a significant difference between the wind direction and the NAI concentration,which is measured against the wind>perpendicular to the wind direction>back to the wind.Correlation between environmental pollution factors and NAI concentration is as follows:NAI is negatively correlated with PM_2.5,PM₁₀,AQI,SO₂,NO₂,CO,and NAI is positively correlated with O₃.