Ranking The Suitability Of Urban Tree Species Based On Affecting Air Quality In Hangzhou,China

Air pollution is becoming serious in most cities of China in recent years.It has attracted people’s attention gradually.Planting trees is the most cost-effective method to improve air quality.Many selection and evaluation systems of urban tree species have been built.But there are still lack of selection systems aiming at improving air quality.According to the demand of improving air quality,taking Hangzhou for example,selection and evaluation system of urban tree species was built in this paper.92 kinds of common tree species in Hangzhou have been screened out for the evaluation,and analytic hierarchy process(AHP)was adopted for the selection systems.The selection and evaluation systems of urban tree species improving air quality was established.Five main characteristics of tree species were summed up: deposition and removal of particulate matter(PM),emitting of volatile organic compounds(VOCs),emitting of anions,features of carbon fixation and oxygen release,and the suitability to urban environment.The weight order is as follows: deposition and removal of particulate matter(PM)(0.3749)>emitting of volatile organic compounds(VOCs)(0.1736)>emitting of anions(0.1560)>the suitability to urban environment(0.1544)>carbon fixation and oxygen release(0.1411).After ranking,the top trees are: Platycladus orientalis(Linn.)Franco,Juniperus chinensis L.,Juniperus chinensis ’Kaizuka’,Cedrus deodara(Roxb.)G.Don,Cupressus funebris Endl.,Magnolia grandiflora Linn.,Cinnamomum camphora(L.)J.Presl and Podocarpus macrophyllus D.Don.,Photinia × fraseri Dress,Viburnum Odoratissimum Ker-Gawl.,Nerium oleander Linn.,Ilex cornuta ’Fortunei’ and Pittosporum tobira(Thunb.)Ait.Applications of these tree species are suggested to be enlarged in Hangzhou.In many cases,the landscape of trees are also important to enjoy people’s feeling in most cities.Besides,microclimatic modification of trees can improve the comfortability of the living environment.Thus,the other selection and evaluation system of urban tree species was built,considering not only the effect to air quality,but also the landscape and microclimatic modification.The indicators weights are as follows: deposition and removal of particulate matter(PM)(0.2840)>emitting of volatile organic compounds(VOCs)(0.1394)> the suitability to urban environment(0.1356)> emitting of anions(0.1355)> microclimatic modification(0.1271)> carbon fixation and oxygen release(0.1178)>landscape(0.0606).After ranking,the top ten suggested trees are: Cupressus funebris Endl.,Juniperus chinensis L.,Cedrus deodara(Roxb.)G.Don,Magnolia grandiflora Linn.,Podocarpus macrophyllus D.Don,Platycladus orientalis(Linn.)Franco,Juniperus chinensis ’Kaizuka’,Pinus elliottii Engelm.,Cinnamomum camphora(L.)J.Presl and Taxodium distichum(Linn.)Rich..The top ten suggested shrubs are: Nerium oleander Linn.,Pittosporum tobira(Thunb.)Ait.,Ligustrum × vicaryi Rehder,Ilex cornuta ’Fortunei’,Photinia × fraseri Dress,Viburnum Odoratissimum Ker-Gawl.,Pyracantha fortuneana(Maxim.)Li,Jasminum mesnyi Hance,Nandina domestica Thunb and Rhododendron simsii Planch.