Study On Airborne Microbes Concentration Change Of Urban Greenlands In Beijing City

Airborne mirobes concentration of different plots in the Yuan Dynasty park was monitored,and the diurnal and annual change of airborne microbes was studied in the paper by sampling using even dish descend method.Besides, airborne microbe concentration of different forest species and different structure of urban greenland, horizontal change of airborne microbe concentration, influence of environmental factors to airborne microbe concentration and bacteria-reducing effect of greenland, relation of particulates and airborne microbe concentration are also discussed.The result indicated:As for different seasons, the daily dynamics of airborne bacteria concentration in Beijing's urban greenlands is on the trend of decrease from 8: 00 to 16: 00 in autumn, in spring it presented "U" shape which higher in the morning and night than in the noon; and in summer it presented "M" shape which arrived peak at 9: 00 and 17: 00. Fungi concentration presented single-peak curve in autumn which arrived highest at 10:00 in the day; in spring it presented double-peak curve which arrived peak at 9: 00 to 11: 00 and 17: 00;and in summer it went on descend from 7: 00 to 13: 00,climbing from 13: 00 to 17: 00 and decreasing seriously from 17: 00 to 19: 00. Actinomycete concentration daily dynamics in autumn maintain ascend from 8:00 to 12:00 and peaked at 12:00 and decreased later,but in very few grrnlands,it increased from 16: 00 to 18: 00, in spring it presented double-peak curve which arrived peak at 9:00 and 17:00,in summer it is similar to that in autumn.Airborne microbe concentration of Beijing's urban greenlands presented regular change along with different month. The annual dynamics of airborne bacteria concentration presented double-peak curve, which is relatively higher at the November, May and June than other months. Fungi concentration presented three-peak curve, in which peak occured in October to November, March and June. Actinomycete concentration presented single-peak curve, in which peak occured in October to November.From the comparison of airborne bacteria concentration in different structure greenlands, it showed that the square space has the highest bacteria concentration, subsequently with lawn, which indicated greenlands have the effect on restraining and reducing airborne bacteria; the lawn, as the greening method with relatively lower vegetation quantity, has the limited function on reducing airborne bacteria.Urban greenlands has the best effect on reducing bacteria.The horizontal change of bacteria concentration was on descend trend from the border of greenlands to the area of 15m inside greenlands, and has no significant difference behind the 15m. Fungi concentration was on stepwise ascend trend from border of greenlands to the area of 15m inside greenlands, and changed a little behind the 15m.Actinomycete concentration formed concentration peak at the 5m apart from the border of greenlands.By multiple analyses to airborne microbe concentration at the horizontal direction of urban greenlands, the preferable forest width should be bigger than 30m which can reduce microbes better. If the shape of greenlands is rectangle, the area of greenlands should be larger than 900m²; if the shape is rotundity, the area should larger than 706.5m².Although the greenlands has the significant effect on reducing airborne microbe concentration and bacteria concentration; it has not distinctive effect on reducing fungi and actinomycete concentration. In July, August and September, the greenlands has the best effect on airborne microbe and bacteria concentration, subsequently with June and October, In July, August and September, the greenland decreased airborne microbe concentration more than 65 percent, and as to bacteria concentration, more than 70 percent was decreased; in June and October, only 40 percent and 45 percent was decreased.Fungi-reducing effect is better in July and August, which arrived above 60 percent, and about 20 percent in June, September and October, but it has no positive bacteria-reducing effect in other month.Air particulates, which usually as the carrier, nutrition and aegis, has great influence on airborne microbe concentration, The result can be concluded by analyzing the relation of particulates concentration and airborne microbe concentration: TSP and PM₁₀ has the significant relation with microbe concentration but PM_2.5 and PM₁ has no significant relation with it.