Screening Of Herbage Plants For Highway Slope Protection And Tree Species Of Forest Belts For Controlling Heavy Metal Pollutions

The construction and operation of highway Seriously destroyed ecological environment. Not only soil and water loss was caused,but also lots of pollution were made including of maleficence gas and heavy metals which come from automobile.Heavy metal pollution would seriously damage agriculture ecological environment safety.Artificial vegetation restoration including slope protection plants and forest belts are effective methods to settle this problem. Related studies were conducted along the Hailin-Yabuli road of national highway 301 in Heilongjiang province and the main results as below:1.According to large-scale field investigation as well as experiments indoors,16 appraisal indexes are selected aiming at getting the suitable plants for highway side slopes,Some important indexes,including belowground biomass,growth rate,leanness-resistance,drought-resistance,root length,aboveground biomass,plant-type,age of utilization were to filtrate the wild species from 21 familiar highway slopes herbaceous plants based on the analytic hierarchy process(AHP).The result showed that the general capability of 11 species were excellent and the suitable pioneer plants for highway slopes protection in cold regions, including Iris lactea var.chinensis,Oenothera biennis,Silene jenissensis,Poa pratensis,Medicago falcata,Plantago depressa,Agropyron cristatum,Erigeron acer,Viola alisoviana,Bromus inermis,Trifolium lupinaster.2.Concentrations of heavy metals(Pb,Cd,Cu,Zn,As) were investigated in roadside surface soil(0～20cm) Of typical vegetation region.The contamination of heavy metals in the soil samples was determined.The results showed that the average concentration of 5 elements were universally higher than the local background value.The roadside surface soil was lightly polluted by Cu,Pb,Zn,As,and was seriously polluted by Cd.Integrated pollution index were moderate.Correlation analysis indicated that the traffic and construction of road absolutely impacted the contamination of Pb,Cd,Cu in the roadside soils.Complex structure forest belts can prevent of pollutant dispersion and reduce impact from road and traffic,simple arbor forest belts do not reduce the area affected by the traffic pollution.So,the optimum model of the pollution control forest belt is consisted of multiple tree species(including arbor,shrub,vine,herbage),and the minimum width of the forest belt extend much beyond 20m,the best width should extend than 60m.3.Concentrations of heavy metals(Pb,Cd,Cu,Zn,As) were investigated in roadside surface soil and leaves of 19 plants species in the forest areas.The results showed that the excellent greening species of protective forest along the polluted highways area were Quercus mongolica,Betula platyphylla,Abies nephrolepis.which could grow well on contaminated environment and accumulated high concentrations of heavy metal elements.The other tree species such as Ulmus propinqua,Ulmus laciniata,Alnus hirsuta,Philadephus schrenkii,Sorbaria kirilowii,Lonicera maacki might be also mainly available in greening for controlling heavy metal pollutions.