Multiphase transfer processes in waste rock piles producing acid mine drainage: 2. Applications of numerical simulation

Acid mine drainage (AMD) results from the oxidation of sulfides, mainly pyrite, present in mine wastes, either mill tailings or waste rock. This is the second of two papers describing the coupled physical processes taking place in waste rock piles undergoing AMD production. Since the oxidation of pyrite involves the consumption of oxygen and the production of heat, the oxidation process initiates coupled processes of gas transfer by diffusion and convection as well as heat transfer. These processes influence the supply of oxygen that is required to sustain the oxidation process. This second paper describes a numerical simulator used to represent the interaction of these coupled transfer processes. Numerical simulations are applied to two large sites with extensive characterization programs and widely different properties and behavior that were described in the first paper. The South Dump of the Doyon mine in Canada is permeable and has a high pyrite oxidation rate, thus making temperature-driven air convection the main oxygen supply mechanism. The Nordhalde of the Ronnenberg mining district in Germany contains lower permeability material which is less reactive, thus leading to a more balanced contribution of gaseous diffusion and convection as oxygen supply mechanisms. Overall, simulations allow a coherent representation of the conditions monitored within the waste rock piles and the confirmation of their physical properties. Conceptual simulations are also carried out to illustrate the potential effect of border membranes and layered co-mingling as mitigation methods used to control AMD production in either active or future waste rock piles.     

“九五”广州地区酸雨污染基本特征研究

根据“九五”期间广州地区酸雨污染状况及与"七五"期间的对比结果,通过分类统计和多元回归,研究探讨了"九五"酸雨污染的基本特征及其影响降水酸度的有关因素.研究表明,SO₄2-是降水化学组成中比重最大的离子,NO₃-对降水酸度影响较大,这两种阴离子的含量多少基本上决定了降水酸度的强弱.因此在减轻二氧化硫污染的同时,加强对氮氧化物污染控制对降低广州地区降水酸度意义重大.      

水稻叶片质膜H~+-ATPase对酸雨胁迫的适应机制

采用水培法研究酸雨胁迫对水稻叶片质膜H+-ATPase活性的影响,结果表明,高强度酸雨(pH 2.5和pH 3.0组)胁迫下,pH 2.5组质膜H+-ATPase活性显著受抑,胞内pH降低,POD活性受抑,pH3.0组质膜H+-ATPase活性上升,胞内pH降低,POD活性升高,质膜透性和MDA含量均增加,Fv/Fm和叶鲜重降低;低强度酸雨(3.0相似文献   

淠河流域不同强度等级降水变化研究

淠河流域降水时空变率大,深入分析不同强度等级降水的特征和变化,对于全面揭示研究区气候变化、合理有效利用水资源、防治洪旱灾害具有十分重要的意义。基于淠河流域12个气象站1958~2012年逐日降水资料,分析年、季不同级别降水量(频次)的变化特点,以及主汛期(5~9月)连续3d最大降水量的概率分布。结果表明,淠河流域小雨量(频次)四季分布比较均匀,级别越高,降水频次越少,分布越集中,夏季暴雨多发。淠河流域年总降水量增加趋势不显著,总降水频次则显著减少。夏季各级别降水量(频次)均呈增加趋势,其中暴雨增加最显著,冬季总降水频次无明显趋势变化,小雨、中雨量增加显著,春、秋季总降水频次和小雨频次的减少趋势极其显著。淠河流域暴雨量、暴雨频次均在1968年发生增多突变,小雨频次在1975年有极显著减少突变,年总降水量有增多突变,总降水频次则有减少突变。自20世纪70年代后期以来,研究区主汛期连续3d极端强降水出现概率加大,不同重现期极值增大,洪涝灾害风险加剧。     

Effect of acid solutions on plants studied by the optical beam deflection method

The optical beam deflection method was applied to study the effects of acid solution on both a terrestial and aquatic plants Egeria and Cerastium, which are common aquatic plant and terrestial weed respectively. A probe beam from a He-Ne laser was passed through a vicinity of a leaf of the plants, which were put in culture dishes filled with acid solutions. Deflection signals of the probe beam were monitored and compared for acid solutions with different pH values. The results of Egria showed that the deflection signals changed dramatically when pH values of acid solutions were 2.0 and 3.0, while little at pH of 4.0 and 5.0. For Cerastium when pH were below 3.0, deflection signals changed greatly with time at the begining. After a certain period of time, deflection signals changed little with time. When pH value was above 4.0, deflection signals of Cerastium were still changing with time even after 20 hours. The results suggested that the damage threshold of pH was between 3.0 and 4.0 for both the land and aquatic plants.     

硬脂酸改性磁铁矿对石油污水的处理研究

研究硬脂酸改性磁铁矿对石油污水中油类物质的吸附,通过改变温度、超声振荡时间和磁铁矿与硬脂酸的质量比等因素,在最佳的改性条件下制得改性磁铁矿。将改性后的磁铁矿应用于石油污水处理,改变震荡时间,用红外分光测油仪得出吸附结果。结果表明:当改性温度为35℃、改性时间为35min、硬脂酸与磁铁矿质量比为3.5%时磁铁矿改性效果最佳,当吸附时间为8min时,对石油炼化污水中油类物质的吸附效果最好,吸附量为216.65mg/g。     

模拟酸雨下铅锌冶炼废渣重金属的静态释放特征

以株洲某铅锌冶炼废水中和渣为研究对象,开展不同初始pH值（3.0,4.5,5.6和7.0）模拟酸雨静态浸出实验,研究22d浸泡过程中废渣Cd、Cu、Pb和Zn等重金属的动态释放规律及其化学形态变化和矿物相变特征.结果表明,废渣具有较强的酸缓冲潜力,浸出液pH值稳定在6.20~6.66.Cu和Pb在浸泡初期释放较快,Cd和Zn释放相对较慢.浸出液Cd浓度随浸出时间增加而上升,Zn浓度呈波动变化,Cu和Pb浓度变幅较小.提高雨水酸度促进废渣中重金属的释放,浸出液Cd、Cu、Pb和Zn浓度范围分别为1.38~8.70,0~0.02,1.21~2.26和27.2~135mg/L,其中Cd、Pb和Zn浓度分别超过我国《铅、锌工业污染物排放标准》（GB 25466-2010）限值的26.6~173倍、1.42~3.52倍和17.1~89.0倍..重金属BCR顺序提取表明,浸出液中较高Cd和Zn浓度与其赋存高活性态比例一致,且酸雨促使残渣态Cd和Pb向活性态转化.XRD分析显示,pH=3.0酸雨处理22d后原废渣中Cd和Zn的赋存矿物相消失,PbSO₄谱峰增强,表明废渣重金属的释放受其赋存矿物相及次生矿物形成的影响.重金属释放率呈现出Cd （2.50%~15.8%）> Zn （0.41%~2.13%）> Pb （0.06%~0.10%）> Cu （0.0003%~0.11%）的趋势.自然堆存酸雨作用下废渣中Cd、Pb和Zn具有较大环境风险,需加强降雨淋滤污染防治管控.     

Mechanisms of Pb(II) coprecipitation with natrojarosite and its behavior during acid dissolution

Lead (Pb) coprecipitation with jarosite is common in natural and engineered environments, such as acid mine drainage (AMD) sites and hydrometallurgical industry. Despite the high relevance for environmental impact, few studies have examined the exact interaction of Pb with jarosite and the dissolution behavior of each phase. In the present work, we demonstrate that Pb mainly interacts with jarosite in four modes, namely incorporation, occlusion, physically mixing, and chemically mixing. For comparison, the four modes of Pb-bearing natrojarosite were synthesized and characterized separately. Batch dissolution experiments were undertaken on these synthetic Pb-bearing natrojarosites under pH 2 to simulate the AMD environments. The introduction of Pb decreases the final Fe releasing efficiency of jarosite-type compounds from 18.18% to 3.45%-5.01%, showing a remarkable inhibition of their dissolution. For Pb releasing behavior, PbSO₄ dissolves in preference to Pb-substituted natrojarosite, i.e., (Na, Pb)-jarosite, which primarily results in the sharp increase of Pb releasing concentration (> 40 mg/L). PbSO₄ occlusion by jarosite-type compounds can significantly reduce the release of Pb. The results of this study could provide useful information regarding Fe and Pb cycling in acidic natural and engineered environments.     

SO2 gas adsorption by modified kaolin clays: influence of previous heating and time acid treatments

Modified kaolin clays were used as adsorbents for SO(2) gas adsorptions. The clays were heated up to 900 °C previous to acid treatments with 0.5 N sulfuric acid solutions at boiling temperature during different times up to 1440 min. Equilibrium adsorption at 25 °C and 0.1 MPa was carried out by using a volumetric apparatus. The samples were characterized by chemical analysis, X-ray diffraction and infrared analysis. The heating of the clays followed by acid treatment improved the adsorption capacity of the kaolin clays. The presence of amorphous silica and hydroxyl in the final products improved SO(2) adsorption capacity. Better properties for SO(2) adsorption were found in kaolin rich in not well ordered kaolinite clay mineral.     

Metal and oxalate contamination in a suburban watershed in the greater Toronto area: the benefits of combining acid leach and selective extraction procedures

Environmentally available concentrations of Fe, Mn, Zn, Cu, Pb, Cr and Ni in soils and sediments from a small suburban catchment, obtained using an acid leach procedure, are compared to the Ontario Ministry of the Environment lowest effect level (LEL) and severe effect levels (SEL) and to Provincial sediment quality guidelines (PSQG's). These data are then compared to the bioavailability, potential bioavailability and non-bioavailability of the same metals, plus oxalate concentration, identified using a selective extraction procedure. This combination of techniques enhanced analytical interpretation with respect to metal mobility and potential metal contamination. Selective extraction highlighted the presence of oxalate as a potential contaminant, especially in poorly drained valley floor deposits (33,633 mg kg(-1) and 26,284 mg kg(-1)) and lakeshore sediments (27,095 mg kg(-1) and 13,729 mg kg(-1)). These levels are considerably in excess of those previously documented in a similar study from Rio de Janeiro, where contamination of urban sediment by sewage is a recognised environmental problem, and could possibly be used both as an indicator of similar contamination and the identification of those areas that warrant further investigation.