公路绿化带滞尘效应研究

Dust-retaining Effects of Roadside Tree-belt on TSP Pollution of Roadside

道路交通扬尘不仅危害人体健康,而且会造成环境污染。以山西省典型公路绿化带为研究对象,对不同公路绿化带进行分类,并选择粒径分别为150、106、75、53μm的黄土粉,模拟道路交通TSP,采用喷粉机设置1、2、3、4 m·s-1的喷粉速度在路沿处设置人工喷粉,在路侧设置样带分0、2、5、10、15、20 m距离梯度布设采样点进行尘源样品的采集,进行称重。本文提出绿化带净滞尘率和梯度净化率的概念,研究不同粒径水平、不同瞬时风力条件以及不同类型绿化带对交通扬尘的阻滞吸收效应,最后基于显著影响因子和因子的互作采用逐步回归法拟合绿化带滞尘效应多元回归模型,分析绿化带滞尘效应与多种林带特征因子的关系。结果表明,公路绿化带明显改变了道路TSP扩散格局,对空气中的粉尘有显著的净化效应。本实验条件下,在距道路5 m范围内绿化带开始发挥效应,净滞尘效应均值达22.95%,随后TSP净滞尘率降低,在20m净滞尘率均值为9.83%,但净化率均值达96.56%;不同粒径水平和瞬时风力条件下,绿化带的滞尘效应不同,TSP粒径为53、75μm时,绿化带在5 m的净滞尘率最高,分别为18.81%和38.09%,而粒径为106、150μm时,绿化带在15 m的净滞尘率最高,分别为15.40%和24.94%,当瞬时风力为1 m·s-1时,净滞尘率在15 m处最高,为16.50%,当瞬时风力分别为2、3、4 m·s-1时,净滞尘率均在5 m处最高,分别为22.03%、28.69%、25.09%,均以高密度型绿化带(郁闭度≥0.55)效果较好;在近路基处栽植杨树(Populus L.)或槐树(Sophora japonica Linn.),且乔木种长势高大并伴有较密的灌草结构,能增强绿化带的滞尘效应。

Road traffic TSP not only threatens human health, but causes environmental pollution. Some typical roadside tree-belts were selected and classified for this study in Shanxi province, TSP pollution of roadside simulated by loess powder with particle size were 150, 106, 75 and 53μm respectively, powder spraying by manual operations via gallus power sprayer with powder spraying speed were 1, 2, 3 and 4 m·s-1 respectively at subgrade, dust sampling points was set in roadside tree-belts distance away from the roads by 0, 2, 5, 10, 15, 20 m on the ground, the dispersion patterns of TSP with or without tree-belts were studied, and dust-retaining effect of tree-belts on TSP pollution with different particle size, different instantaneous wind condition and different stand types were analyzed. Based on significant impact factors and interactions, multiple regression models on dust-retaining effects of roadside tree-belt and stand characteristic factors were set up using stepwise. The results showed: Roadside tree-belts have obvious dust-retaining effects that changed the dispersion patterns of road traffic TSP, in this study, away from the roads of 5 m the net purifying rate of tree-belt was 22.95%on average, and dust-retaining rate of 61.10%, then declined with net purifying rate of tree-belt of 9.83% at 20 m, with dust-retaining rate of 96.56%; dust-retaining effects varies from particle size and instantaneous wind condition, net purifying rate of tree-belt was highest at 5 m with particle size were 53 and 75 μm or with instantaneous wind condition were 2, 3, 4 m·s-1, the value were 18.81%, 38.09%, 22.03%, 28.69% and 25.09% respectively; net purifying rate of tree-belt was highest at 15 m with particle size were 106 and 150μm or with instantaneous wind condition was 1 m·s-1, the value were 15.40%, 24.94%and 16.50%respectively;high density tree-belt with a canopy density≥0.55 have better effect on dust-retaining, the dust-retaining effects of roadside tree-belt could be improved by complex structure with taller trees plus shrubs and grass, Populus L. and Sophora japonica Linn. planted at subgrade would be better.