| The environment pollution and ecological destruction caused by mining and smelting is a global event which has attracted more and more attention and has become an important field for environmental geochemical research. For a long time, AMD, which has lower pH and higher heavy metal content, has been paid more attention for its damage on ecosystem and the studies of AMD have acquired some important developments. The problem of AMD and heavy metals contamination are especially serious in sulfide-ore-dominated nonferrous multi-metal mines.Tongling mine area is one of the typical skarn type Cu-Au mining district in the World, which has been exploited for 3-thousand-year. Through the careful field study and in-house analyses, the article focuses on the environmental geochemistry study of copper-ore-tailings yard, mine waste dump, water system, sediments, soil and plants. The study of weathering characteristics of representative mining sections in Xinqiao pyrite-type massive sulfide deposit and Yaoyuanshan skarn-type copper deposit reveals the mechanisms of the sulfide mineral oxidation acid, the law of heavy metals release, migration and transform in Tongling mine waste dump and mine tailing sand, and heavy metals existing species and their biological effects. Furthermore, dimensional distribution of heavy metals in water systems, sediment, mine tailing, scrapheaps, soil plants has been studied in details and comprehensive heavy metals environmental impacts by mining has been analyzed. In the end, the releasing, migrating and transforming model of heavy metals among different medium is constructed.In Xinqiao mine, the CIA value of weathering profile changes rapidly, reflecting that the weathering action occurs completely and mainly on the rock-soil intrerfaces. In Yaoyuanshan mine, the variety of primary components of weathering profile appears with ore transformation progresses, while the variety near the rock-soil interfaces is not obvious. The sequence of heavy metals releasing capability from sulfide ores is Pb>Zn>Ni>Co>Cu in the studied weathering profile. Super high enrichment and strong fractionation of REE occurred near the interface, and the REE distribution patterns in the Xinqiao's weathering profile and Yaoyuanshan's weathering profile show negative slope model on the basis of standard of shale in North America because of the moist and thermic weathering conditions and low-pH mine drainage in Tongling.The study shows that the metals contents in rich-sulfids abandoned ore heaps reduce gradually as lapse of time and there are subsection and zonation in the weathering profiles. The sequence of heavy metals releasing capability from mine waste dump is Cr>Mn>Zn>Co>Hg >Cd>As>Pb>Cu, which is determined by original content and occurrence. According to the calculation of fitting equetion, it will take 103.2a for Cu, 101.4a for Pb, 42.7a for Zn, 95.6a for As, 91.2a for Cd, 72.1a for Hg, 39.6a for Mn, 45.5a for Co and 1.43a for Cr to reduce to the natural background value in soil. For the Ni content in abandoned ore heaps is lower than the value of its background value in soil, the problem of Ni releasing does not exist.Eluviating experiment shows that in the early stage, tailing does not acidify and the heavy metal releasing ratio is low. Tailing- water interaction induce the activation and transportation of heavy metals in the tailing and aquatic pollution. The water transport ability of Pb, Hg is high in tailing of Tongling mine area. Migration coefficients of heavy metals in tailings by water of Pb and Hg are 9.95 and 5.56, while that of As, Cr and Co are 0.08, 0.07 and 0.05, respectively. Migration coefficients of other heavy metals are lower than 1., the gangues is also a potential primary heavy metal pollution source for surface water in Tongling because of higher content of heavy metal elements Although its relatively low migration coefficients of heavy metals. According to the calculation by fitting negative exponente quations of some heavy metal releasing, it will take 143a for Cu, 8a for Pb, 105a for Zn, 79.4a for Cd, 59a for As and 11.6a for Cr to reduce to the safe capability of soil. The relative releasing ratio of heavy metals in tailing is Pb> Cr>As>Cd>Zn>Cu.The distribution regulation of heavy metals in reclamation Linchong tailing is the enrich in middle and deficient around, but the content of As, Cd in middle is low than that around. In 40~60cm depth, Co, As, Cu, Zn, Cd, Ni, Pb has been enriched obviously, the reason is of artificially reclamation and shallow weathering.The characteristics of granularity distribution shows that the heavy metals content inside sediments increases as granularity decrease. The heavy metals content is very high in mine and decrease rapidly along the direction of stream. The content become stable in middle reaches of rivers, but is still much higher than standard. In the catchment area, most heavy metals are slight pollutions except Cd. The sediment in Tongling area is multi-metal pollution, the characteristic of pollution is quite different in varied district. Compared with background value, Cu, Pb, Zn, Cd, As has been highly enriched. The Cd is the most serious pollution element in sediment, while As, Cu, Pb, Hg, Cr, Zn, Co, Ni, Mn are less serious.For the appraised reaches, Ecological risk and heavy metals pollution evaluation with potential ecological risk index show that the most dangerous ecological risk factor of the mine area sediment is Cd, followed with As, Cu and Pb. Ecological risk of different reaches of mine area rivers is also drastically varied. The most ecologically dangerous sediment was that from Jiguanshan reaches of Yang river, followed by the section of Shengchong river which locates in the vicinity of Xinqiao field, middle-reaches of Xinqiao river. Even the estuary nearby Yangtse River of Shun'an river sediment was heavily contaminated due to high concentration of cadmium, and the heavy metals contamination and potential ecological risk of Baoshan river and Zhongcang river were relatively slight. The eigenvalue and distribution pattern of sediment REE show that the contamination of water systems sediment is due to the historic minging of polymetallic ores and the calcinations of ores.The soil's physical chemistry condition in different city zones of Tongling are prone to adsorb metals ion. The heavy metals' bio-toxicity was increased by high heavy metals validity content because of the lower-pH of the soils. Fe-Mn oxide species and exchangeable species are predominant for the majority of heavy metals which are assessed in the acid soil.organic matter species, carbonate species and mineral slag species is lower. Organic matter species and mineral slag species were dominated in alkaline soil.The Igeo and RI show that soil was contaminated by heavy metals mainly in some mining areas such as in the vicinity of Xinqiao, Jiguanshan and Fenghuangshan ore-field, cupper2351.4, cadmiuml8.92, Iead341.4, arsenic77.7, Znl611.0 and HgO.351 values et al. typically exceedrespectively 2351.4 mg-kg"1, 18.92 mg-kg"1, 341.4 mg-kg"1, 77.7 mg-kg"1, 1611.0 mg-kg1 and 0.351 mg-kg'1 in sampled topsoils, with high values also being present in the subsoil. The assessment result of the heavy metals' ecological risk reveals that the most dangerous pollution element was Cu, followed with Cd, As, Pb. Cr, Co, Hg, Mn which belong to lightly potential ecological risk. The majority of heavy metals assessed were more than middle contaminated in vegetable plantation soils in Xiangsicun and Xiashankou of Xiangsi river valley because of wastewater irrigation.In comparison with the standard of national food, the content of Pb> As> Cd^ Cr in Brassica peHnensis, Capsicus frutescens, Radish and Lettuce is transnomal, respectively. The superscale times of Pb is 13.5~71.0; The content of As in vegetable is evidently on the high side, the superscale times is 1.2~11.6. Moreover, the superscale times of Cd is 3.8-46.4. The results of our study indicate that the content of Cu is over 10 times in the roots of penoy which is a kind of officinal plants, Pb and As is slightly excessive, Cd is under the limit. The accumulation of heavy mentals in pioneers which are wild and self-sowed is much higher than those in edible vegetables and officinal plants. What is more, different kinds of plants have different distinct selectivities for heavy metals. The accumulation of Cu in the root of Commelina communis is high to 2777 mg-kg"1, and is beyond 1000 mg-kg"1 in shoot, which is the extreme of Cu hyperaccumulating plant. Phragmites australis Trin has a powerful uptake ability of Fe and Cd, and the accumulation is 11.3% and 29.8 mg-kg"1, respectively. Furteremore, Commelina communis and Phragmites australis Trin also have predominance in enriching other heavy metals. In contrast with Commelina communis and Phragmites australis Trin, although the enrichment of Impretacy lindraca, Cynodon dactylon, Torilis japonica Houtt. and Portulaca oleraceais are lower than them, they are still considered as prefered species in Phytoremediation of mine because of their mighty viability in ultra environment. As far as the cumulative accumulation of heavy metals is concerned, the enrichment in different plants decreases in the order: Phragmites australis Trin.> Commelina communis> Impretacy lindraca> Torilis japonica Houtt.> root peel of Paeonia ostii > Cynodon dactylon> Portulaca oleracea. In vegetables , the accumulative coefficients of these elements, except Cd, are all less than 1. Compared with different elements in the same kind of vegetables, we can clearly know that the accumulative coefficients of Cd, Zn, Fe are remarkable higher than those of Cu, Pb, Cr, Ni, and those accumulative coefficients, except Pb, are basically accorded with pollution coefficients and water transferred coefficients. What is more, those accumulative coefficients indicate that the accumulative abilities of these elements decrease in the order: Fe>Hg>Cd>Pb>As>Cu>Ni>Zn>Co>Mn>Cr, which are mainly related to the compound pollution and the difference of content between different kinds of elements. The rate of heavy metal transport in Radish is all more than 1, which indicates that the shoots of Radish is much easier to uptake heavy metals than the roots. But there are obvious differences between the rate of heavy metal transport in Brassica pekinensis. The rate of Cu, Zn, Cd, Hg is more than 1, and the rate of others is less than 1.Whereas the heavy metal transport rate of Commelina communis and Penoy is correspondingly lower than others. We have studied 89 species, members of 73 genera and 30 families high plants which grow in the ultra environment of TongLing diggning, and knew that all of these plants are high tolerance widespread species, and every one has higher adaption in the ultra environment. For the type of existence, they are mainly herbage. For the behaviour of bionomics, they are mostly sun-plants, few are shade-plants. It indicates the entironments of mullock-heap, mining-pit and copper-ore-tailings yard were atrocious.The "butterfly effect" operates when exploitation polluting interacts, overlaps, accelerates and toxicity magnifies. Ruined saps, archaic slags heaps, ganguse reservoirs and abandoned ore hills are the source of AMD and heavy metal pollution in Tongling ore field. The model of releasing and migariting of heavy metals is that the acidic mine drainage containing wealthily metals ions which rain eluviation generates exudes downwards and around it. and the AMD contaminate water and soil in the vicinity of mine, ruin biology environment, decrease bacteria and microorganism in water system, prevent cleansing from microorganism and deteriorate water system,Destroy the soil's structures of nutrition and constitutes, lead to unsettling and living for plants. It pollutes environment by raising a dust on dry weather. Polluted waters, soils and air injurants enter into animals and plants through food chains, finally endanger human being's health.The bioremediation can be achieved by executing "biomanipulation" and by the help of kinds of technologies and measures. There are three pollution remediation areas and three phases are classified for mining area eco-remediating. Therefore, the paper chooses reasonably out pioneer plants which were natural colonized, especially breed remediation plants with beared strongly native species. There are appropriate natural root and extreme ecological environments for hyperaccumulator growing in Tongling mining area, and hyperaccumulator, bioindicator and metal-tolerant plants are propitious to be variated and evoluted.There are copper hyperaccumulator-------Commelina communis and potential copperhyperaccumulatoi------Elsholtzia splendens N and Rumex acetosa growing, and potential ironhyperaccumulator------Commelina communis, Phragmites australis Trin., Imperata cylindricaland CynodondactylonCL.) Pers. growing in Tongling mining area. It is a appropriate native species breeding of hyperaccumulator for mining eco-remediating. According to geography and climate of Tongling, breeding and migrating can be used for mining area eco-remediating. If migrating hyperaccumulator is used as a chief means for eco-remediation, native species is all-important to migrate hyperaccumulator. |
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