Study On Effect Of Traffic On Roadside Soil Environment In Lahsa And The Surrounding Area

ABSTRACT:Transportation construction and operation will be influence for the soil environment roadside, and lead to soil in an extent of degeneration, as the presentations of soil erosion, fertility degradation&heavy-metal accumulating. It is the road sections around Lhasa City as the investigation scope for this thesis. At Namtso in Damxung County which as a main region for sampling,12roadside slope surface samples,10mountain slope surface samples,3soil profile samples, and2precipitation samples were taken, in order to measure the7Be content in them for soil-erosion tracing by Hige Purity Ge (HPGe) y-ray Spectrometer. Inside the Lhasa City,17roadside-soil samples and16roadside-tree leaves samples are collected.80roadside-soil samples from14sections at different distance of Rd. G109and G318were also taken. These samples are used for the measurement of heavy-metal content by Inductively Coupled Plasma Mass Spectrometry (ICP-MS), including Cu, Zn, Pb, Cd, Cr, Co, Ni&As, on which the regularity of heavy-metal distribution analysis based. General conclusion of the research as below:(1) According to the analysis of the soil properties, as the conditions of higher attitude, lower pH value, looser texture and higher content of big grains, always lead to the higher organic carbon content in the soil. Within the distance of10m from the roadside, the vegetation degeneration gets seriously, organic carbon content gets low, fractal dimension goes down, and big sand-grains take higher ratio, nearby the road-edge. It presents the soil erosion obviously. Even for the excavated road-edge, soil is always lack of vegetation coverage, low content of organics, and soil pH value higher than7.5. It is hard for vegetation recovery naturally.(2) According to the result of7Be tracing investigation, in Damxung County, the bareness earth and excavated soil road-edge takes erosion more seriously than the soil inside bare mountain. Three samples which are taken from middle to bottom of the slope, present the depositing generally.(3) As the survey of heavy-metal accumulation for the road around Lhasa city, almost roadside soil is large quantity of heavy-metal gathered, and the cumulant is related with traffic opening duration and if higher mountain nearby. With the analysis of contents, classification of heavy-metals, and the research for the correlation between heavy-metals and soil physicochemical properties, beside Rd G109and G318sections, it is known that, Cu, Zn, Pb, and Cd are the main source of road transportation pollutions. Cr, Co, Ni and As are derived from the generating process of soil. The heavy-metal content is exponential reduction with the distance from road-edge. At the distance of0to10m, the content of heavy-metal reduces with sharp falling, and the reduction goes slow down at the distance10to30m. After30m, the heavy-metal comes almost to a constant. It proves that, transportation impact the soil environment critically, and lead to severity of erosion.