Study On The Dust Retention Ability Of Hetan Expressway Forest Belt In Urumqi

This study focused on the Hetan Expressway forest belt in Urumqi,Xinjiang as the research object,and three mixed forest belts of Hetan Road were selected as the research area,and sets 6 real-time monitoring points in different widths of the forest belt.In January,May,July and September of 2018,the teperal and spacial changes of the particle concentration in the forest belt were studied and the weather conditions for three consecutive days were monitored.The research on the change of the dust retention ability of the tree species was selected,such as Fraxinus bungeana,Ulmus pumila,Populus alba,Catalpa speciosa and Rhus typhina.The research conclusions are as follows:(1)The leaf dust retention of different tree species increased with the increase of interval time,reached near saturation after 20 days,and then manual cleaning;Populus alba(1.59 g·m-2)and Catalpa speciosa(2.42 g·m-2)dust retention ability is the best,followed by Ulmus pumila(1.15 g·m-2),and Fraxinus bungeana(0.60 g·m-2)is the worst.The Fraxinus bungeana with different width from the Hetan expressway has a larger dust holding capacity at 15 m(1.05 g·m-2)and 20 m(1.00 g·m-2),and the smallest is 5 m(0.47 g·m-2).(2)The daily variation of PM2.5 and PM10 concentrations is basically the same,12:00(44.06 μg·m-3,49.72 μg·m-3)is a distinct peak;at 9:00(26.94 μg·m-3,29.67 μg·m-3)and 18:00(22.83 pg·m-3,25.44 μg·m-3)are small peaks,10:00(18.11 μg·m-3,21.50 μg·m-3)an d 16:00(18.06 μg·m-3,20.44 μg·m-3)is a trough.The monthly variation of the concentra tion of particulate matter in the forest belt varies with the season,sorted as January>Septe mber>May>July.The rate of reduction of particulate matter in different seasons is from Ju ly>May>September>January;January reduction rate is all negative,May and July are all p ositive;forest belts block particulate matter.The effect is best at10:00 in the morning,and the reduction rates for PM10 and PM2.5 are 45%and 46%,respectively;at 14:00,the fores t belt reduction efficiency is all negative.(3)The concentration of particulate matter at a height of 0.6 m in the forest belt is less than 1.5 m;combined with the effective width of the forest belt in different seasons and different days of the season,it is considered that the effective width of the particulate matter in the unilateral forest belt of the Hetan expressway is:PM10,20-25 m;PM2.5,12-16 m.The concentration of particulate matter decreases with the increase of temperature and relative humidity,but when the temperature and relative humidity increase to a certain extent,the concentration of particulate matter will increase and increase,Maximum wind speed is the biggest factor affecting tree species.