【作者】 詹婧；

【导师】 孙庆业；

【作者基本信息】 安徽大学 ， 生态学， 2014， 博士

【摘要】 铜矿开采和浮选过程所产生的废弃物堆积而形成铜尾矿废弃地,其中的金属硫化物易于发生氧化,导致尾矿的酸化,从而对周围环境造成污染。植被重建被广泛地应用于废弃地的生态修复。本研究以铜陵矿区不同金属硫化物含量的水木冲尾矿废弃地和杨山冲尾矿废弃地为研究对象,通过分析铜尾矿中铁和硫的形态与含量、尾矿产酸潜力以及氧化速率,探讨自然和人工植物群落建立下铜尾矿废弃地中金属硫化物的生物氧化和化学氧化作用,植物地上凋落物以及植物根系对铜尾矿中金属硫化物氧化过程的影响以及不同修复方式下植物的发育及引起的尾矿中金属硫化物氧化作用的变化。主要研究结果如下：1.铜尾矿废弃地剖面(0-60cm)自上而下,pH和酸中和能力增加,净产酸量和金属硫化物的氧化速率逐渐降低。水木冲尾矿库裸地表层30cm呈现较强的酸化作用,植物群落下废弃地酸化主要在表层10cm,金属硫化物氧化过程均以化学氧化为主。尾矿裸地表层极端酸性环境有利于嗜酸铁硫氧化微生物的代谢,具有较高的生物氧化速率。植物群落的建立促进了废弃地水分的积累和孔隙度的提高,有利于尾矿中金属硫化物生物和化学氧化作用的进行。然而,尾矿裸地产酸潜力和氧化速率显著高于植物群落下废弃地,植被建立引起的废弃地表面光照、温度和氧气浓度的降低可能是导致尾矿中金属硫化物氧化减弱的主要原因。2.木本植物盐肤木(Rhus chinensis)群落下尾矿中金属硫化物氧化作用强于草本植物白茅(Imperata cylindrica)和香根草(Vetiveria zizanioides);主成分分析(PCA)表明植物群落对废弃地剖面40-60cm尾矿层影响不显著。植物群落的建立和发育有利于减缓尾矿的酸化,同时能够有效抑制尾矿氧化前锋的深层迁移。水木冲铜尾矿的产酸潜力和氧化速率显著高于低硫化物含量的杨山冲铜尾矿,植物群落建立对杨山冲铜尾矿酸化影响不显著。铜尾矿中金属硫化物含量是决定尾矿酸化与否的关键因子。3.水木冲铜尾矿废弃地四种优势植物白茅、香根草、狗牙根(Cynodon dactylon)和芒(Miscanthus sinensis)根际尾矿pH和NAG-pH低于非根际尾矿,根际尾矿净产酸量分别高于其非根际尾矿,不同植物根际pH和NAG-pH由低到高依次为狗牙根、芒、白茅和香根草,但仅以狗牙根根际和非根际之间净产酸、NAG-pH差异显著。优势植物根际和非根际尾矿为近中性(pH6.13-7.38),以化学氧化为主；根际高的有机质和养分含量促进了尾矿的生物和化学耗氧；狗牙根根际尾矿的生物和化学氧化速率显著高于其他三种优势植物。植物根系通过影响根际氧气含量和铁硫氧化微生物活性一定程度上抑制了根际尾矿中金属硫化物的氧化,有利于减缓根际pH的降低。4.聚类分析表明,各植物根际尾矿和非根际尾矿的氧化特征表现出高的相关性。以狗牙根与其他植物根际尾矿相关性最低,具有最高的净产酸。植物根系在尾矿层的分布特征对根际尾矿中金属硫化物的氧化具有重要影响,以浅根系植物狗牙根根际尾矿酸化程度最高,具有发达根系的优势植物香根草,其根际尾矿低的酸化作用可能与深根系植物根际环境中低的氧气浓度有关。5.不同厚度(5cm、10cm和20cm)植物(白茅和香根草)凋落物覆盖下,铜尾矿剖面的氧气浓度显著降低,各尾矿层水分含量提高。受凋落物影响,水木冲近中性正常铜尾矿pH显著降低,随凋落物厚度增加,其pH降幅增大,各处理组均以表层铜尾矿(0-10cmm)酸化程度最高,主要为金属硫化物的化学氧化过程。然而,凋落物覆盖引起水木冲酸化铜尾矿pH的升高,pH增幅随凋落物厚度增加而增大；0-30cm尾矿层中,以中间层(10-20cm)pH最低,具有高的离子浓度,而对照处理以表层(0-10cm)酸化程度最强,存在硬盘层的形成；其氧化过程以生物氧化为主。6.白茅和香根草凋落物覆盖处理能够抑制尾矿中金属硫化物的化学氧化；同时,引起近中性铜尾矿的生物氧化速率的降低和酸化尾矿铁硫氧化微生物活性的提高。总体上凋落物的覆盖有利于减缓铜尾矿的氧化进程,植物凋落物类型对尾矿总氧化速率影响不显著。多元回归分析表明,所加凋落物中过量阳离子总量(总灰分碱)和尾矿起始pH是影响尾矿pH变化的主要因子。7.对于水木冲铜尾矿废弃地,覆土(30-40cm)处理下的表层铜尾矿具有低的有机质以及有效氮、磷等养分含量,其游离氧化铁含量、净产酸量以及生物和化学氧化速率显著低于未覆土表层尾矿。粉砂质壤土的覆盖能够有效地减少尾矿层的矿物风化,低的氧气和养分含量抑制了尾矿中金属硫化物的化学和生物氧化作用。8.尿素在水木冲铜尾矿废弃地的施用能够显著提高尾矿中的速效氮含量,促进植被的生长。对于呈微酸性(pH4.4-5.3)的近期植物(白茅和香根草)群落下铜尾矿废弃地,尿素作用下,尾矿的游离氧化铁含量、生物和化学氧化速率显著提高,净产酸量显著降低；对于近中性(pH6.9～7.1)的早期植物群落下铜尾矿废弃地,尿素对尾矿中金属硫化物氧化作用的影响并不显著,然而,尾矿净产酸量显著提高。铜尾矿废弃地pH的变化取决于尿素中氮的转化过程以及尾矿自身酸碱性。9.解磷真菌出芽短梗霉(Aureobasidium pullulans)直接施用于铜尾矿废弃地,植被的生长、尾矿游离氧化铁、速效养分(氮和磷)和有机质含量、生物和化学氧化速率均有所提高,但影响并不显著,可能与废弃地不良环境对A. pullulans生长和代谢的抑制作用有关。总而言之,植被的建立有利于尾矿废弃地的酸化控制,植物凋落物和根系对尾矿中金属硫化物氧化的影响因尾矿和植物类型而异；具有高近地面盖度和深根系的耐性植物(如香根草)能够有效地应用于废弃地的生态修复；人工辅助修复(施肥、覆土)对废弃地酸化的影响与废弃地自身的性质有关。更多还原

【Abstract】 The mining tailings, powder wastes produced in the flocculate flotation of copper ore, are generally piled up in the tailings impoundment leading to the formation of copper mine wasteland. Acidification of mine wasteland is caused by the oxidization of metal sulfides, resulting in serious pollution to the surrounding environment. Phytoremediation is widely used in ecological restoration of mine wastelands. In this study, the forms and contents of iron and sulfur, the net acid generation and the oxidation rate of mine tailings were analyzed in Yangshanchong and Shuimuchong mine wastelands differing in the contents of metal sulfides, in order to investigate the biological and chemical oxidation processes of metal sulfides in mine wastelands under natural and artificial plant communities, the effects of plant residues and roots on the oxidation processes of sulfides, and the development of plant communities with different amendments and the consequent changes of oxidation of metal sulfides. The main results were as follows:1. The wastelands of copper mine tailings in the profile (0-60cm) showed increasing pH and acid neutralization capacity, and decreasing net acid generation and oxidation rate of metal sulfides. The top30cm showed obvious acidification in bare wastelands, while only the top10cm of wasteland under plant communities was significantly oxidized in Shuimuchong mine wasteland. The oxidation processes were dominated by chemical oxidation. The extreme acidic condition of top tailings favored the oxidation of sulfides by acidophilic bacteria, resulting in the high biological oxidation rate. The establishment of plant communities increased the water content and porosity of mine wasteland, and thus promoted the biological and chemical oxidation of sulfides in mine tailings. Bare wasteland showed higher net acid generation and oxidation rate than wastelands under plant communities. The reducing of light, temperature and oxygen content on the surface of mine wasteland resulted from phytoremediation was likely to be the main reason for the weakness of sulfide oxidation in the tailings. 2. The mine wasteland under Rhus chinensis showed high net acid generation and oxidation rate than that under I. cylindrica and V. zizanioides. The principal component analysis (PCA) showed that the layers of40to60cm were not significantly affected by plant communities. The development of plant communities was beneficial to slow the acidification of mine tailings, and effectively inhibit the migration of oxidation front. Shuimuchong wasteland displayed significantly higher net acid generation and oxidation rate than Yangshanchong wasteland with low sulfide content, and the effect of phytoremediation on the acidification of Yangshanchong wasteland was not significant. The content of metal sulfides in the copper tailings was the key factor leading to the acidification.3. Compared to nonrhizospheric tailings from I. cylindrical, V. zizanioides, Cynodon dactylon and Miscanthus sinensis in Shuimuchong wasteland, the rhizospheric tailings showed low pH and NAG-pH, and high net acid generation, respectively. The pH and NAG-pH of rhizospheric tailings increased in the following order:Cynodon dactylon<M. sinensis<I. cylindrical<V. zizanioides. The rhizospheric and nonrhizospheric tailings with circumneutral pH (6.13～7.38) dominated by chemical oxidation of sulfides. The high contents of organic matter and nutrients in rhizosphere contributed to the biological and chemical oxygen consumption, and the rhizospheric tailings of C. dactylon showed the highest biological and chemical oxidation rate among four dominant plants. The changes of oxygen content and oxidizing bacteria activities caused by plant roots slowed the oxidation rate of metal sulfides in rhizosphere to a certain extent, which was conducive to suppress a decrease in pH of the rhizosphere.4. Cluster analysis showed that the oxidation characteristics of rhizospheric and nonrhizospheric tailings from the same plant displayed a high correlation, and a low correlation was presented between C. dactylon and the other three dominant plants. Distribution of plant roots in the tailings exerted an important impact on the oxidation of rhizospheric tailings. C. dactylon with shallow roots showed the greatest acidification, while the rhizospheric tailings from V. zizanioides with well-developed root presented weak acidification, which may be related to the low oxygen content in deep rhizospheric tailings.5. The contents of oxygen and water in the mine tailings with I. cylindrical and V. zizanioides residues covered (5cm, to10cm and20cm thick layer) significantly decreased and increased, respectively. With the coverage of plant residues, the circumneutral unoxidized tailings showed decreasing pH compared with controls, and the increasing thick of plant restudies enhanced the pH decline. The top layer tailings (0-10cm) were in the greatest acidification, and dominated by chemical oxidation. However, the acidic oxidized tailings showed increasing pH with residues covered, and the pH amplification increased with the thick of plant restudies; among the three tailings layers,10-20cm tailings displayed the lowest pH, and the highest ion concentration; the most acidified layer of controls was0-10cm tailings with the formation of the hardpan, and biological oxidation was the main oxidizing process.6. The coverage of I. cylindrica and V. zizanioides residues restrained the chemical oxidation of metal sulfides in mine tailings. Meanwhile, the residues caused a decline of biological oxidation of circumneutral tailings, and an improvement of oxidizing bacteria activity in oxidized tailings. As a whole, the coverage of residues was beneficial to slow the oxidation rate of mine tailings, and no significan difference was shown due to the types of residues. Multiple regression analysis showed that the amounts of excessive cations added as plant residues and the initial pH of tailings were main factors affecting the extent of tailing pH changes.7. The copper tailings covered with soil layer (30～40cm) in Shuimuchong mine wasteland showed low content of organic matter, available nitrogen and phosphorus; the free iron oxides content, net acid generation, and biological and chemical oxidation rate of the tailings was significantly lower than that of tailings without amendments. The silty loam cover layer can effectively reduce the mineral weathering of tailings, and low contents of oxygen and nutrient restrained the chemical and biological oxidation of metal sulfides in the copper mine tailings.8. The available nitrogen content of Shuimuchong mine wasteland increased significantly with the application of urea; the wastelands (pH4.44～5.25) under plant communities of I. cylindrica and V. zizanioides in young phase displayed a great improvement in free iron oxide content and biological and chemical oxidation rate, and a significant decrease in net acid generation; meanwhile, the oxidation of metal sulfides in wastelands (pH6.9～7.1) under plant communities of I. cylindrica and V. zizanioides in mature phase was not significantly affected by the application of urea, but net acid generation greatly increased. The pH change of mine wastelands depended on the transformation of urea and the acidity of tailings.9. The inoculation of phosphate-solubilizing fungi Aureobasidium pullulans in mine wasteland promoted the development of plant communities, the contents of free iron oxides, available nutrients (nitrogen and phosphorus) and organic matter, and biological and chemical oxidation rate of sulfides, but the effect was not significant, which was likely related to the inhibition of hostile condition of mine wasteland on A. pullulans growth and metabolism.In conclusion, the establishment of vegetation is effective in suppressing the acidification of mine wastelands; the effect of plant residues and root on sulfide oxidation in the tailings differs in tailings and plant species, and the tolerant plant with high surface coverage and deep roots (such as V. zizanioides) can be effectively applied to the restoration of mine wastelands. The effect of assisted remediation (fertilization or soil covers) on wasteland acidification is close related to the properties of mine tailings.更多还原