Study On Vegetation Restoration In Weathered Soil Tailings

We have exploited the mineral resources on a large scale as we make progresses. The exploitation of gold resources have serious effects on the eco-environment of the mining area and soil of tailings. As a result, the social and economic sustainable development of mining area is greatly constrained. The thesis applies the theories on the recovery and reconstruction of ecology and studies the damages by mining gold resources on the eco-environment of the mining area through wild investigation and physical and chemical analysis; the thesis chooses the model of restoring tree species and allocation through vegetation research and analysis of biocenology and the self-restoring ability of environment; the thesis analyses the agricultural qualification of soil of tailings based on the pot experiment of heavy metals concentration; the thesis finally establishes vegetation self-restoring model and the eco-environment prevention and treatment systems. The studies of tailings vegetation have significant theoretical and realistic meaning for the better exploitation of tailings land resources and the maintenance and improvement of mining eco-environment. The conclusions are drawn as follows:(1)On the Water and soil resources damage of gold recourses exploitation. The exploiting projects occupies large quantities of land resources, deforms terrain, damages landscape, leads to the change of hydrology conditions and loss of biodiversity, aggravates water loss and soil erosion of the mining. The total area by destruction and occupation of gold mining area is 113.65hm2, it aggravated water and soil erosion 5903.8t in 2009.The influences on the soil of mining area are as follows:bad soil structure, reduction of silts contained, increase of sand particles, excessive solidity of tailings soil with density growing to 1.61-1.74 g/cm3,the change of the water-holding, water-retaining and water-tight capacity, pH increasing to over 8.18,soil alkalization, the loss of nutrition, the extreme leanness of soil, the growth of heavy metals in tailings soil with Cd,Ni exceeding national standard and the remaining toxic substance cyanide in the determination of five kinds(Cd,Pb,Cu,Ni,Zn).(2) Study on the vegetation damage of gold mining results show that the tailing areas have 24 species of plant, they belonged 14 families and 23 genera, contrasting with the natural vegetation areas without excavating, decreased of 11 families,20 genera and 22 species.In addition to five kinds of cultivated species, the main natural growth of vegetation is grasses, especially Asteraceae and Gramineae as the most important, accounting for 41.6%.Gold mining on vegetation damage is devastating, causing severe degradation of vegetation, loss of biodiversity, loss of community structure simplified.(3)Study of vegetation restoration on soil physical and chemical properties of modified matrix effect, and discussed the existing problems in restoration. On the basis of investigating vegetation of the mining, area and analyzing biocenology traits and environment self-restoring capacity, the thesis identifies Rabbinic pseudoacacia, Amorpha fruticosa, populous X Canadensis, Broussonetia kazinoki, Ailanthus altissima, Hibiscus, Pittosporum pentandrum, Boehmeria nivea, Vetiveria zizanioides, Ciliate desert-grass, and Neyraudia reynaudiana are used as vegetation restoration species and the allocation model of "mixing arbor, shrub and grass together but shrub and grass going ahead". The thesis discusses the establishment of vegetation restoration model combining "artificial restoration" and "natural evolution" and the eco-environment prevention and treatment systems "combining engineering measures, plant measures and temporary measures".(4) The pot experiment study of tailings soil based on Cd concentration shows that pak-choi can survive in tailings soil with seed germination rate between 33.3% and 66.7%.The seed germination rate increases with the life length of tailings soil.The output of T09 is only 28.7% of CK. The plant is short and yellow with diseases. The concentration effect of pakchoi absorbing Cd is so significant that pakchoi T09 contains the highest level of Cd reaching 1.65mg/kg 4.12 times more than national food hygienic standard critical point. The analysis shows that tailings soil is not proper, if in short time, for cultivating as agricultural land.