| The development activity of nonferrous metals mine caused serious soil heavy metal pollution to mine areas and the surrounding areas, which became the main source of environmental pollution of mine areas. It is very difficult for this kind of pollution to be restored. However, the phytoremediation technology of low price, less environmental disturbance and no secondary pollution is the most effective measure for the soil heavy metal pollution control in metal mine areas and the improvement of eco-environmental quality. Therefore, this dissertation takes Hongtoushan copper mine area in Fushun city of Liaoning province, Qingchengzi lead-zinc mine area in Dandong city and Yangjiazhangzi molybdenum mine area in Huludao city as research areas to carry out field vegetation survey and collect plant samples as well as rhizosphere soil samples. The analysis of measuring the heavy metal content of plants and soil as well as physical and chemical properties of soil and the evluation towards soil nutrient status in mine areas and the pollution condition caused by heavy metals have been carried out to make clear the pollution degree of heavy metal in mine areas and determine soil improvement measures; The field investigation towards plants and the measuring on the enrichment and metastasis potential towards heavy metal caused by dominant plants have been carried out in order to screen out the heavy metal resistant plants suitable for the soil condition in this research area or the plants with (potential)hyper-accumulator characteristics. Then the perfect pattern of forest vegetation will be selected and the late maintenance management will be strengthened to complete phyto-remediation project. The research results show that:(1) The compound pollutiont of the heavy metal--Cu、Cd、Zn、Pb is in the nonferrous metals mineland.And there may be homoeologous relationship between these heavy metal elements.The content of the heavy metal--Cu、Cd、Zn、Pb in Hongtoushan copper mine area is beyond the standard greatly. Especially the accumulation of Cu、Cd、Zn in the soil is much higher. There is rather obvious positive relation between the total content of Cu, Zn and Cd, so it is the same with the total content of Zn, Cu and Cd as well as the total content of Pb and Hg together with the total content of Cr and As; The relation between the total content of Cu and As is obviously positive. The content of Pb, Cd, Zn, and Cu in Qingchengzi lead-zinc mine area is beyond the standard greatly; especially the content of Pb and Cd is both over100times higher. That shows the accumulation of Pb and Cd in the soil is very strong. There exists very apparent corelation between the contents of most heavy metals in the soil, which shows the pollution of various heavy metals has homology and all are probably closely related with frequent mining activity in mining areas. The contents of Pb, Zn, Cd and Cu in the soil of Yangjiazhangzi molybdenum mine area are slightly beyond the standard. There exist very obvious positive correlation between the total content of Cu and Pb, Cu and Pb and Cr, Zn and As and Pb, Cu and Cr, as well as Cd and Hg; that shows there may be homoeologous relationship between these heavy metal elements.(2) The pollution degree of soil heavy metal is rather serious in the nonferrous metals mineland.And the main pollution factors are Cu, Cd,Zn and Pb.Adopting fuzzy synthetic evaluation----weighed average model and fuzzy synthesis index to evaluate the pollution degree of heavy metal in Hongtoushan copper mine area: the main pollution factors of waste dump are Cu, Cd and Zn; the main pollution factors of tailing pond are Cu, Zn and Pb; the main pollution factors of the surrounding farmland are Cd, Zn, As and Cu. Adopting geo-accumulation index method and potential ecological risk index to evaluate the pollution degree of heavy metal Qingchengzi lead-zinc mine area: the pollution of heavy metals—Pb and Cd is extremely serious; the pollution of Zn is lopsided; the pollution of Cu and As is both moderate; and the pollution of Cr is slighter. The evalution result of the two evaluation modes—RI and Igeo is basically the same through comparing, which shows the combination of the two models is mutally supplemented and verified. The sequencing for the pollution degree of heavy metals is Cd>Pb>Hg>Zn>Cu>As>Cr. Among them, the pollution from Pb and Cd in waste dump is serious; the pollution from Cd and Pb in tailing pond is extremely serious; the pollution from Hg and Cd of the surrounding farmland is serious. Adopting single pollution index and Nemerow multi-factor index methods to evaluate the pollution degree of heavy metal in YangJiaZhangZi molybdenum mine areas:the multi-factor pollution index--Pj in waste dump, tailing pond and surrounding farmland is all over3, which shows the pollution degree of soil heavy metal is rather serious.(3) The content of exchangeable Zn, Mo, Cu and Cd in Yangjiazhangzi molybdenum mine area is the highest. All those factors have the highest effectiveness and toxity on plants.Adopting Tessier sequential extraction to perform sample analysis:the content of exchangeable Cd, Cu and Zn in surrounding mountain area around stopes is the highest; the content of exchangeable Zn, Mo and Cu of the farmland around waste dumps is the highest; the content of exchangeable Cd, Zn and Mo of the farmland around tailing pond is the highest. All those factors have the highest effectiveness and toxity on plants.Through the correlation analysis on the usability of heavy metal in soil and the content of heavy metal in crops, we can discover that:there exists very apparently weak or strong negative correlation between the available contents of Zn and Cd in soil and the contents of five kinds of heavy metals in crop seeds. The correlation between the rest elements is not significant. Through the correlation analysis between the content of all forms of heavy metal from soil samples and the content of soil nutrient, we can discover that:there is very significantly negative correlation between the combined state of organic sulphide of Cu and total nitrogen, available nitrogen, available phosphorus, total potassium and available potassium; there is very significantly positive correlation between the total content of Zn and its exchangeability as well as iron-manganese oxides; there is very significantly positive correlation between Zn and organic material as well as available phosphorus; obvious and extremely obvious negative correlation exists between the total content of Pb, the exchangeable content of Pb, the content of the combined state of organic sulphide of Pb and the content of soil nutrient; there is very apparent positive correlation between available phosphorus and the total content of Cd as well as other sorts of forms; very obvious negative correlation often exists between the combined state of organic sulphide of Hg and the content of soil nutrient.(4) The content of soil nutrient is very low in the nonferrous metals mineland. The most deficient nutrient elements of soil are nitrogen and potassium.Adopting fuzzy synthetic evaluation method and principal components analysis method carry out comprehensive evaluation on the soil fertility in mine areas:the nutrient situation of waste dump and the rock soil of tailing pond in Hongtoushan copper mine area is grade Ⅱ----"poorness"; the nutrient situation of surrounding farmland is grade V---"abundance". The most deficient nutrient elements of soil in waste dump are nitrogen and potassium; what the tailing pond is lacking in most is organic material, phosphorus and potassium. Of all nutritive elements besides phosphor, shortage of nitrogen and potassium in the waste dump and tailing mine area of Qingchengzi lead-zinc mine area is the most severe. And then the nutrient situation of vicinal agricultural land is abundant except the element of nitrogen. The sequencing of comprehensive fertility condition of soil is:surrounding farmland>waste dump> tailing pond. There usually exists very obvious negative correlation between the soil pH value of Yangjiazhangzi molybdenum mine area and the content of soil nutrient. The soil of abandoned land presents alkaline and the content of its nutrient is very low. The sequencing of comprehensive fertility condition of soil is:soil under hazelnut trees of nearby mountain slope> nearby farmland> sea buckthorns land in tailing pond> waste dump> tailing pond.(5) The measures of adjusting the pH value, Eh value, organic material and texture etc will be taken to change the activity of heavy metal in soil. Thus Bio-availability of heavy metal and the utilization fate of heavy metal by plants will also be changed to further improve the survival percentage of plants.Adopting the methods of applying lime to the acid soil and increasing soil alkaline to decrease the Bio-availability of heavy metal; To create the reducing environmental condition by irrigating or flooding so as to reduce the Eh value of soil and the number of heavy metal ions in soil; Increase the use of organic fertilizer like sewage sludges, solid waste, animal manure and plant straws etc to increase the content of soil nutrient and functional group; choose microelements which are harmless to plants or the microelements which are lightly harmful to plants and are good for the growth of plants when the concentration of microelements are low to resist the heavy metals with too high content. The discovery is made through experience that these improvement measures are feasible for the application in research area.(6) The enrichment and metastatic potential of analysis as well as comparison towards heavy metal have been carried out about main dominat plants in the nonferrous metals mineland. And the plants of rosa davarica pall, carex and garden burnet have stronger cumulate ability for heavy metal so that a theoretic basic can be provided for the selection of pioneer plants in the vegetation restoration process.Field survey has been conducted the natural plant community on the abandoned land in mine areas and analysis as well as determination have been carried out about main dominat plants and relative analysis has been performed about their heavy metal content in the rhizosphere soil:Cu, Zn and Cd of the dominant plants above earth are obviously positively correlated with the content of them respectively in the soil of Hongtoushan copper mine area and Zn, Pb and Cd in Qingchengzi lead-zinc mine area; the soil in Yangjiazhangzi molybdenum mine area has obvious correlation with Hg of corns, Pb and Hg of soybeans and Zn of millet.Comparison for the ability of enriching heavy metals by plants:the plants having stronger enriching ability for Cu in Hongtoushan copper mine area are respectively wild mugwort, carex and nicandra physalodes; the plants having stronger enriching ability for Zn are respectively rosa davarica pall, carex and nicandra physalodes; the plants having stronger enriching ability for Pb are respectively reed, larch and nicandra physalodes; the plants having stronger enriching ability for Cd are respectively Hankow willow, artemisia sieversiana and nicandra physalodes. The plants having stronger enriching ability for Cu in Qingchengzi lead-zinc mine area are respectively carex goat beard water pepper, clematis, wild mugwort, patrinia villosa and artemisia sieversiana; the plants having stronger enriching ability for Zn are respectively carex goat beard, cernuum, lactuca indica, Xingan oxtongue and birch; the plants having stronger enriching ability for Pb are respectively cernuum, water pepper, clematis, Xingan oxtongue, patrinia villosa and wild hawthorn; the plants having stronger enriching ability for Cd are respectively garden burnet, cernuum, lactuca indica, patrinia villosa and birch. The sequencing of enriching ability for heavy metal of three kinds of crops in Yangjiazhangzi molybdenum mine area are:corn and millet:Cu>Zn>Cd>Hg>Pb; soybeans:Cu>Cd>Zn>Hg>Pb.Comparison for the ability of transferring heavy metals by plants:the plants having stronger transferring ability for Cu in the tailing pond of Hongtoushan copper mine area, waste dump, and refuse dump are respectively rosa davarica pall, carex and nicandra physalodes; the plants having stronger transferring ability for Zn are respectively rosa davarica pall, carex and nicandra physalodes; the plants having stronger transferring ability for Pb are respectively false spiraea, carex and nicandra physalodes; the plants having stronger transferring ability for Cd are respectively rosa davarica pall, carex and nicandra physalodes. The plants having the strongest transferring ability for Cu in Qingchengzi lead-zinc mine area are respectively garden burnet, Xingan oxtongue and agrimony; the plants having the strongest transferring ability for Zn are respectively cernuum, lactuca indica and artemisia sieversiana; the plants having the strongest transferring ability for Pb are respectively cernuum, Xingan oxtongue and spiraea; the plants having the strongest transferring ability for Cd are respectively garden burnet, Xingan oxtongue and spiraea.(7) Sifting heavy metal resistant plants or the plants with (potential) hyper-accumulator characteristics such as false spiraea, nicandra physalodes and lactuca indica. And the optimus plant disposition mode are determined and applied in the vegetation restoration project through planting trials.According to community succession theory, the vegetation restoration process of abandoned land in mine areas begins with the introduction of pioneer plants and reaches the mesophytic climax community in the end after a series of succession stages. The zonal vegetation in research area is coniferous and broadleaved mixed forest. The progressive succession begins with bare land roughly experiences the stages of bare land'hassock'shrub'coniferous forest'coniferous and broadleaved mixed forest.Sift the heavy metal resistant plants or the plants with (potential) hyper-accumulator characteristics:Selecting wild mugwort, rosa davarica pall and false spiraea in original tailing pond of Hongtoushan copper mine area; selecting carex, larch and artemisia sieversiana in waste dump; selecting nicandra physalodes and glaucum etc in tailing pond covered with solid waste; selecting cernuum, garden burnet and carex goat beard in waste dump of Qingchengzi lead-zinc mine area; selecting Xingan oxtongue, lactuca indica and patrinia villosa; selecting white birch、spiraea and artemisia sieversiana etc in surrounding mountainous regions; selecting the plant variety possessing strong resistence against heavy metal like three kinds of turf grass---tall fescur, bluegrass and ryegrass as well as sea buckhorn etc in Yangjiazhangzi molybdenum mine area as the poineer species of plant restoration on the abandoned land in research areas.Determine the optimus plant disposition mode:the restoration in tailing pond of copper mine area aims at centering on protection, adopting plant restoration measure of the combination of shrub and herb plants. The optimus plant disposition mode:rosa davarica X false spiraea X (nicandra physalodes, glaucum and amaranth); the restoration in waste dump of Hongtoushan copper mine area aims at centering on protection and considering utilization as well by adopting the plant restoration measure of the combination of arbor and herb plants. The optimus plant disposition mode:larch X (aspen and black locust) X (artemisia sieversiana and carex). The restoration in tailing pond of Qingchengzi lead-zinc mine area aims at centering on protection, utilizing herb plant community to cover tailings bare land rapidly and improve soin quality gradually so as to create conditions for the growth of arbon and shrub. he optimus plant disposition mode:water-flooded land:reed X grass X polygonum hydropiper; others:Xingan oxtongue X lactuca indica X patrinia villosa; the restoration in waste dump aims at centering on protection and considering utilization as well by adopting the plant restoration measure of the combination of arbor, shrub and herb plants. The optimus plant disposition mode:Chinese pine X birch X (lespedeza and garden burnet) X (artemisia gmelinii, skunk bugbane, carex goat beard and cernuum). The restoration in tailing pond of Yangjiazhangzi molybdenum mine area aims at centering on protection and considering utilization as well by adopting the plant restoration measure of the combination of shrub and herb plants. The optimus plant disposition mode:sea buckhorn X caragana×(tall fescue, bluegrass and ryegrass). Above research conclusions are of large practical significance to environmental control and ecological restoration of metal mine areas polluted seriously by heavy metal, have greatly improved vegetation reconstruction effect and ecological restoration success rate, and will have a far-reaching impact on the sustainable development of the mine area and its entironment. |
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