Study On Air Purification Ability Of Platycladus Orientalis And Quercus Variabilis In Jiulong Mountain Of Beijing

In the research five types of stands were selected in Jiulong Mountain of Beijing,including both even-aged stands of Platycladus orientalis and Quercus variabilis,both uneven-aged stands of Platycladus orientalis and Quercus variabilis,and one mixed stand composed of Platycladus orientalis and Quercus variabilis.Which had been explored to determine the dynamic change of atmospheric environment and their purification ability.It took a series of investigation including stand structure,air-ion concentration,concentration of SO₂,sulfur dioxide elimination capacity of 9 common greening tree species.Then atmosphere quality of the stands and sulfur dioxide elimination capacity of species were evaluated.The results would provide scientific basis for choosing the ideal greening species,develop eco-tourism and adjusting the greening structure of urban area in the future.The main conclusion was as follows:（1）Variation characteristics of air-ion concentration of 5 standsThe whole rhythm of the air-ion concentration of 5 stands showed double peak type just like‘M’.The best level occurred during 8 am and 10 am.Significant difference has been found that the average air ions concentration were diffenent in different seasons.Among all the concentration of summer is the highest,autumn is higher than spring.The average air-ion concentration during daytime of 5 stands were 1548 ions/cm³,1440 ions/cm³,1233 ions/cm³,1157 ions/cm³,1656 ions/cm³ in summer.Which was higher than that in spring and autumn.There was no significant difference between the average air-ion concentration during daytime of spring and autumn even if that in spring was higher than autumn.Significant difference has been found that the average air ions concentration were different in different stands stand types.The ranking of average air-ion concentration during daytime showed as Platycladus orientalis×Quercus variabilis>Platycladus orientalis of the same age>Platycladus orientalis of the different age >Quercus variabilis of the same age>Quercus variabilis of the different age.There was significant difference between two kinds stands of Platycladus orientalis and two kinds stands of Quercus variabilis.And there was significant difference between the stand of Platycladus orientalis×Quercus variabilis and two kinds stands of Quercus variabilis too.（2）Variation characteristics of SO₂ concentration of 5 standsThe whole rhythm of variation of SO₂ concentration of 5 stands showed downward and upward type just like‘V’ during the growth period of leaf and branch and the slow growth period.The minimum of the growth period of leaf and branch occurred during 14 and 16 pm.The slow growth period of which occurred during 10 am.The whole rhythm of variation of SO₂ concentration of 5 stands showed double peak type just like ‘M’ during the growth period of height and diameter.The maximum occurred at 14 pm and the minimum occurred at 12 am and 16 pm.Significant difference has been found that the average SO₂ concentration were different in different seasons.The ranking of average SO₂ concentration during daytime showed as the growth period of leaf and branch>the slow growth period>the growth period of height and diameter,which were significantly different.Significant difference has been found that the average SO₂ concentration were different in different stands stand types.Among all the concentration of Platycladus orientalis of the same age is the highest,two kinds stands of Platycladus orientalis is higher than two kinds stands of Quercus variabilis and Platycladus orientalis&Quercus variabilis.There was no significant difference among two kinds stands of Platycladus orientalis and Platycladus orientalis&Quercus variabilis.The others were just the opposite.（3）Sulfur dioxide elimination capacity of 9 common greening tree SpeciesThere was significant difference in sulfur contents and relative sulfur absorption ability of each species under different fouling conditions.Which was tend to significantly related with the pollution levels.There was obvious difference in sulfur dioxide absorption and accumulation capacity among 9 species under same fouling conditions.Salix matsudana is the best of which average relative sulfur absorption ability is 2.38 mg·g^-1 and average contaminative index was 2.23,Sophora japonica was better of which average relative sulfur absorption ability is 1.18 mg·g^-1 and average contaminative index was 2.09,Ailanthus altissima,Cotinus coggygria,Populus tomentosa and Acer mono were general;Ulmus pumila,Platycladus orientalis and Pinus tabuliformis were worse.To summarise,Salix matsudana and Sophora japonica could be ideal selection for urban greening of Beijing.