| The universal environmental problems, such as soil erosion, heavy metal pollution, wick ecological environment and hard to ecological restore, were similar in Dabaoshan Mine, an open-pit mining polymetallic mine in Guangdong Province. Basing on the field investigation, in-situ district simulating runoff scouring experiment, laboratory analysis and outdoor planting experiments, the systematic study was conducted on the soil erosion characteristic and comprehensive measures for the prevention and control of Dabaoshan mine. The main conclusions were drawn as follows:1) Slope length, height and density of erosion gully could be used to represent the characteristics and differences of soil erosion for different slopes of the mining area, and a discriminant model of soil erosion intensity in mining area had been built by cluster analysis and discriminant analysis. After that, the existing soil loss area was324.48hm2in Dabaoshan mining area, accounting for48.8%of the total area. The soil erosion was severe and worthy of great attention.2) The average runoff of new spoil soils, old spoil soils and nature soils were6.52,5.75and0.69L/min respectively, and the average sediment content of each were156.79L.51.68L and23.99L;the sediment yield rate were0.99.0.27and0.03L/min. The average drain rate of soil Cd of new spoil soils, old spoil soil? and nature soils were32.55.12.18and0.09mg/(min·m2) respectively; the average drain rate of soil Pb were1648.98,432.10and8.07mg/(min·m2) respectively; the average drain rate of soil Zn were1854.35,460.14and4.92mg/(min·m2); the average drain rate of soil Cu were1742.63,429.47and8.69mg/(minm2) respectively. The sediment yield rate of new spoil soils and old spoil soils in the second minute were2.94and1.11kg/min. which were2.96and4.08times of its average sediment yield rate, showing the "early-yield-sediment" effect. The sum content of stone particles and sand particles of new spoil soils, old spoil soils and nature soils were87.15%,84.45%and32.02%respectively, significantly different from nature soils3) As the slope gradient were5°,15°and25°. its average runoff were respectively5.06.5.6and6.52L/min; the average sediment content were0.12.0.89and0.99kg/min:the average sediment yield rate were0.120.89and0.99kg/min. With the increase of gradient, the average runoff, sediment content and sediment yield rate increased. As the gradient was5°15°and25°. the average drop-out rate of heavy metals in the eroded sediment was as follows:the average drop-out rate of Cd was64,19.07and32.55mg/(min·m2); the average drop-out rate of Pb was1290.61,1788.71and1648.98mg/(min·m2); the average drop-out rate of Zn was178.46,1748.40and1854.35mg/(min·m2); the average drop-out rate of Cu was191.38,1809.89,1742.63mg/(min·m2).The average drop-out rate of Cd and Zn increased with the increase of slope; The average drop-out rate of Pb and Cu order as follow:15°>25°>5°.4) When the erosion intensity were300,500and700L/h, the average runoff were respectively4.33,6.52and8.82L/min; the sediment content were151.18,156.79and240.79g/L; the sediment yield rate were0.78,0.99and1.95kg/min; the average drain rate of heavy metals were showed as follows: Cd were24.08,32.55and48.36mg/(min·m2); Pb were1290.61,1648.98and3169.10mg/(min·m2); Zn were1397.22,1854.35and3437.87mg/(min·m2), Cu werel240.47,1742.63and2946.80mg/(min·m2) under the erosion strength of300,500and700L/h. All of indexes showed same change law, which increased with the rise of erosion intensity.5) When the coverage condition were0%,30%,60%and90%, the average runoff were respectively6.52,6.23,5.94and5.80n; the average sediment concentration were respectively156.79,43.40,33.17and26.83g/L; the average sediment rate were0.99,0.25,0.19and0.14kg/min; the average drain rate of heavy metals were Cd32.55,9.14,8.11and4.03mg/(min·m2); Pb1648.98.402.43.294.28and210.64mg/(min·m2); Zn1854.35,382.03.305.02and196.38mg/(min·m2); Cu1742.63.333.24.264.61and191.28mg/(min·m2). The average drain rate reduced with the increase of coverage. The single factor indexes of Cd and Cu, within the27soil samples of Dabaoshan mining area, were both more than1, exceeding the standard. The single factor index of21soil samples tested were more than1, and77.8%of all the samples exceeded the standard. The comprehensive pollution index of27soil samples were between5.74and157.23, greater than3, showing that the mining area had been severely polluted by heavy metals, especially Cd and Cu.6)1%limestone and3%manure were used as soil improvement to modify soils samples. and then the germinations ratio of wheat seeds, which were treated with improved soils, was95%and germination index was78%; the average survival (germination rate) and retention rate of experimental plants were94%and88%respectively, while the average height of plants were52.7cm, showing that the soils could meet the growing demands already.7) Between the13kinds of dominant species investigated in the mining area, the Pb content of aerial parts of Panicum repens L. reached1214.00mg/kg: the Cu content of Paulownia fortunei leaves reached1024.80mg/kg. both of which were more than1OOOmg/kg.the threshold of Pb and Cu hyper-accumulation planis: the biological transfer coefficients were1.77and13.74. greater than1.0, which were also satisfied with the standard of hyper-accumulation plants, indicating that Panicum repens L. might be a kind of Pb hyper-accumulation plants, and Paulownia fortunei might be a kind of Cu hyper-accumulation plants of absorbing heavy metals. According to the conclusions of the heavy metal enrichment characteristics of plants and outdoor planting test, Paulownia fortunei, Pinus massoniana, Nerium indicum Mill, Pennisetum purpureum, Miscanthus floridulus and Cynodondactylon(Linn.)Pers. Could be used as pioneer species of Dabaoshan mine vegetation restoration.
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