Research On Absorption Of Common Tree Species To Heavy Metal And PM2.5 In Beijing

In this study, more than 10 different tree species(Salix babylonica, Pinus bungeana Zucc., Platycladus orientalis(Linn.), Sophora japonica Linn., Cedrus deodara(Roxb.)Loud Franco, Sabina chinensis, Ginkgo biloba, Acer elegantulum Fang et P. L. Chiu, Pinus tabuliformis, Fraxinus chinensis Roxb., populous) in four different zones were taken as the research objects. These zones included Beijing urban area(Nanhaizi Park), Suburban Park area(Botanical Garden), outer suburb garden area(Xishan Park), and the outer Mountain Scenic Area(Songshan Nature Reserve). It aimed at researching the accumulation ability of plant leaves to the toxic and harmful pollutants and particulate in the atmosphere, and evaluating the service function conversion efficiency of plants, and screening tree species resources of strong ecological purification ability, which could provide the scientific data basis for selecting excellent ecological greening tree species and promoting better development for city forestry. The results showed that:The accumulation ability of toxic and harmful pollutants for part of the trees had larger seasonal variation. The accumulation for most of them in the spring was low and higher in autumn.The absorption ability for different elements of different trees on different sites changed largely. But generally speaking, there were three areas in that the accumulation ability of Salix babylonica to Cu(the highest were 21.51, 20.20, 10.00 mg·kg-1, respctively) were most, and the accumulation ability of conifer tree species to Sb(0.290, 0.146, 0.126mg·kg-1, respectively) and Pb(5.95, 5.08, 3.04mg·kg-1, respectively) were most, and the accumulation ability of populous to Co(1.09, 0.73, 2.46, 0.64 mg·kg-1, respectively) were most.The average accumulation of trees for S, the ability of Salix babylonica(8.43 g·kg-1) and Ginkgo biloba(5.57g·kg-1) were higher. From the pot experiment, the S accumulation in leaves was mainly from the atmosphere, and the forest played the part of purifying atmospheric S pollution.In addition to Cd and Mo in the leaves that had a significant correlation with soil, there were no significant correlation between leaves and soil for other elements; in the same place, there was a certain relationship for the metal content in leaves with different trees.There was a certain difference on PM2.5 particles retention ability for different species leaves, and the retention ability of conifer was higher than that of broadleaf tree species. In autumn, the PM2.5 average adsorption amount per unit leaf area of the conifer was 0.160μg·cm-2 and broadleaf tree was 0.011μg·cm-2 in Nanhaizi Park; the conifer was 0.204μg·cm-2 and broadleaf tree was 0.096μg·cm-2 in Botanical Garden; in the conifer was 0.534μg·cm-2 and broadleaf tree was 0.245μg·cm-2 in Xishan Forest Park; the conifer was 0.143μg·cm-2 and broadleaf tree was 0.017μg·cm-2 in Songshan Nature Reserve.The comprehensive pollutants absorption ability for different tree species sorted: Salix babylonica > populous > Cedrus deodara( Roxb.) Loud Franco > Acer elegantulum Fang et P. L. Chiu>Sabina chinensis>Sophora japonica Linn.>Pinus tabuliformis>Ginkgo biloba>Fraxinus chinensis Roxb.>Pinus bungeana Zucc.>Platycladus orientalis(Linn.).For the different species and its absorption function on different elements, the conversion efficiency basically was shown a decreasing trend by the “high pollution area(center and district)- intermediate pollution area(suburban park area)- lower pollution area(suburban landscape district)- relatively clean area(outer)”.