石灰土盐基离子迁移对模拟酸雨的响应

为揭示酸雨条件下石灰土盐基离子迁移特征及其缓冲性能,对石灰土进行了室内模拟酸雨淋溶试验,探讨酸雨酸度、土层厚度、土表覆被对石灰土酸化/石灰土抗酸性以及盐基离子迁移的影响。结果表明:（1）在pH=3.5、4.5、5.5的酸雨淋溶下,石灰土盐基离子迁移量差异不显著,对酸雨具有极强的缓冲能力。期间,Ca2+与Mg2+释放呈显著线性相关。（2）土壤厚度对石灰土抗酸性有极显著影响,土壤越厚,对酸雨的抗性越大,反之越小。（3）土厚比1∶2.5∶5的石灰土盐基离子淋失状况为K+淋失量1∶1.43∶2.06,Ca2+淋失量为1∶1.63∶3.13,Mg2+淋失量为1∶1.64∶3.15,表明土厚的增加能大大降低酸雨对盐基的淋溶。（4）石灰土土表覆盖不同,其盐基离子迁移淋溶量差异明显,但并不对土壤酸化效应产生显著影响。      

模拟酸雨对阳离子在土体内迁移的影响

利用室内模拟酸雨的土柱实验,研究了在红壤表土施用钾肥后酸雨对不同土层交换性阳离子迁移的影响.结果表明,在不同土体深度,表土直接受酸沉降的淋溶,也是最容易发生酸化的土层, pH 2.5酸雨淋溶后,表土 pH值下降到 3.5～ 4.2,这是铝的缓冲范围,且土壤交换性 H 和 Al3 含量的增加显示出土壤对酸沉降的缓冲效率和缓冲能力的急剧减弱; pH 4.5酸雨淋溶后, A和 B层土壤 pH值上升了 0.3～ 0.5,其机理与的专性吸附释放 OH-有关;表土施用钾肥后, K 交换土壤表面的 H 和 Al3 ,引起土壤交换性 H 和 Al3 向下迁移;不同 pH值的酸性降雨引起土壤中交换性阳离子向下迁移和淋失的程度也有明显的差异, pH 2.5酸雨淋溶后土壤溶液中钾的含量高于 pH 4.5酸雨淋溶的,但交换性钾含量低于后者; pH 2.5和 pH 4.5酸雨淋溶后交换性钙的淋失量分别占原土的 50%～ 70%和 20%～ 40%,这表明酸雨淋洗会导致养分库的损耗,造成土壤养分贫瘠.     

淋滤条件下GGBS-MgO固化铅污染黏土强度与溶出特性研究

以粒化高炉矿渣粉-氧化镁（GGBS-MgO）固化铅污染黏土为研究对象,通过半动态淋滤试验,对GGBS-MgO在酸雨作用下的强度特性及溶出特性进行研究。通过对GGBS-MgO固化铅污染黏土半动态淋滤后pH值、针刺深度、无侧限抗压强度及浸出液中[Pb]、[Ca]、[Mg]元素浓度的测试,分析淋滤液初始pH值、掺量以及含铅不含铅对GGBS-MgO固化土强度特性的影响,讨论了初始淋滤液pH值、固化剂掺量对GGBS-MgO固化铅污染土累积铅、钙、镁溶出质量以及铅有效扩散系数的影响规律。结果表明,半动态淋滤试验使试样无侧限抗压强度qu较标准养护39 d试样降低了2%～53%,且淋滤液初始pH=2对试样qu影响最大;在相同掺量、相同淋滤液初始pH值时,GGBS-MgO固化未污染土半动态淋滤后qu较水泥固化未污染土qu提高了12%～43%;且当固化剂掺量为18%时,固化铅污染土强度特性较水泥有明显优势,约为水泥固化铅污染土强度的1.3～1.8倍;且相同配比时,淋滤液初始pH=2表层的pH值约为pH=3、4、5、7的1/2;随着淋滤液初始pH值、半动态淋滤后qu及内部pH值的增加,针刺深度减小;针贯入阻力与qu存在幂指数关系。此外,累积铅、钙、镁溶出质量随着初始淋滤液pH值、固化剂掺量的增加而减少,在初始淋滤液pH=2时,Ai,Pb、Ai,Ca、Ai,Mg分别约为pH=3、4、5和7的29～222倍、1.7～4.4倍和12.0～80.3倍;固化剂掺量为12%时的累积溶出质量约是18%掺量时的1.1～2.0倍;铅有效扩散系数De随着初始淋滤液pH值的增加而降低,初始淋滤液pH=2时的De比pH=3～7的De高约3～5个数量级;且低于水泥固化铅污染土De,当初始淋滤液pH=7时,GGBS-MgO固化土De相比于水泥固化土低1～2个数量级。     

酸雨淋溶下MICP固化铅污染土的淋滤特性研究

酸雨可与MICP矿化作用过程中生成的碳酸盐反应,破坏材料的结构强度,使被固定的重金属离子再次释放,但该技术在酸雨环境下的研究较少,耐酸腐蚀性尚不明确,因此对酸雨入渗作用下MICP固化重金属污染土的淋滤特性的研究具有现实意义。本文设计了pH值为3.5、4.5、5.6的3种典型的酸雨条件,用pH值为7.5的去离子水作对照,通过土柱淋滤的方法对MICP固化粉土进行了实验研究,分析不同酸雨pH值对MICP固化铅污染土样的强度、pH值、Pb²⁺、Ca²⁺淋出量及Pb²⁺赋存形态的影响。结果表明：随酸液pH值降低,MICP固化试样的强度降低,淋出液pH值降低,Pb²⁺、Ca²⁺淋出量增加,固化试样中可交换态的Pb²⁺增加,当pH值为5.6时,试样受酸雨影响较小,pH值降为3.5时,试样变化显著。     

渔塘坝富硒碳质岩石中硒淋滤实验的初步研究

渔塘坝是中国较为典型的高硒地区之一。从该区选取了4个典型的富硒碳质岩样品,并在常温条件下进行了淋滤实验研究(pH=2.0,4.0和6.5)。初步结果表明:随着液固比的增大和淋滤时间的延长,淋滤液中硒含量变化的总体呈降低趋势。不同岩类间硒的淋失量有所差别,但岩石总量硒并不是影响硒淋失的主要因素。淋滤原液的不同pH值对岩石硒的淋失有显著影响,其淋失量的排列顺序是pH=2.0>pH=6.5>pH=4.0。岩石中碳酸盐与黄铁矿含量之比同淋滤液pH的变化有关,并且极可能是影响岩石风化初始阶段硒淋失的重要因素之一。     

模拟酸雨对土壤有效磷衰减的影响

采用pH3．0和pH4．5的2种模拟酸雨与对照pH6．0的雨水， 湿润培育加磷后的土壤（2种红壤和1种水稻土）。试验结果表明，土壤中的有效磷的衰减在快反应阶段呈直线下降，而在慢反应阶段缓慢下降。快反应阶段持续时间约3－6h，随模拟降雨的p H值不同而不同，pH值愈低，持续时间愈短。与对照相比，模拟酸雨对有效磷衰减产生较大影响，模拟酸雨pH值愈低，有效磷衰减得愈快，尤其在快反应阶段影响更为明显；在慢反应阶段，随着时间的延续，影响逐渐变小。模拟酸雨对有效磷衰减的影响因土壤类型不同而不同，表现为红壤大于水稻土。酸雨加快土 壤有效磷的衰减，其主要原因是酸雨作用导致活性铝的大量释放，增加了磷的活性吸附点位，从而增加了对磷酸根离子配位吸附。     

成都经济区农业土壤Cd元素的解吸动力学

对不同酸雨条件下水稻土Cd释放的研究发现,吸附态Cd释放的过程可以分为快反应和慢反应2个阶段。采用常见的动力学方程和本文创建的反三角函数方程,对淋滤实验数据进行了拟合。结果表明,反三角函数方程对多种酸雨条件下水稻土吸附态Cd释放过程的拟合度最佳。此外,多项式方程也能较好地描述这一过程。     

不同酸度淋溶条件下石煤中Cd、Pb释放速率

模拟天然降雨成分在三种酸度(pH 3.5、5.5和7.5)下对浙江省下寒武统荷塘组含钒石煤进行了淋溶作用实验,利用ICP-OES、ICP-MS等技术分析了滤出液中的Cd、Pb含量,研究了它们在不同酸碱度的淋溶条件下的释放特征.结果表明,石煤滤出液中Cd含量高低与淋滤液pH值的大小呈反比关系,在强酸性淋滤条件下滤出率为1...     

模拟不同气候条件下碳酸盐岩风化作用的淋溶实验研究

通过模拟干热、湿热与干冷3种气候条件,以饱和CO2水作为淋溶液,对黔中岩溶区3条碳酸盐岩风化壳岩-土界面的岩粉层试样进行了淋溶实验(其中干热、湿热条件下淋溶到残余酸不溶物阶段),对淋出液的pH值以及主要造岩元素的浓度进行了动态分析。结果表明,碳酸盐岩风化壳岩-土界面由岩到土的转变过程中,伴随碳酸盐的溶蚀,酸不溶物已表现出明显的风化倾向。碳酸盐的溶蚀强度表现为干冷>干热>湿热的变化趋势。温度低,碳酸盐的溶解速率大;排水条件好,碳酸盐溶解释放的Ca、Mg易随风化流体排出体系。对于酸不溶物组分,淋溶实验中有:(1)K、Na、Mg、Si、P的载体矿物风化强度在干热条件下最大(至于Ca,由于方解石与白云石均是其主要的载体矿物,酸不溶物相中的Ca难以在淋出液中有效识别)。在干冷与湿热之间,K、Na、Mg等盐基离子的溶出能力大多表现为湿热>干冷,指示了温度对盐基离子释放强度的重要制约作用;而Si和P未表现出一致的变化趋势,可能源于淋溶体系微环境的差异。(2)Fe与Mn表现出弱迁移性。其中,Fe在干冷环境下淋出强度最弱,说明温度是制约含Fe矿物分解速率的重要因素。而Fe在干热与湿热之间,以及Mn在3种淋溶条件下,未呈现出一致的变化趋势。(3)Al和Ti在碳酸盐岩风化过程中表现出强烈的惰性。      

模拟酸雨条件下石灰土—碳酸盐岩体系的碳汇效应

为揭示不同酸度降雨对石灰土—碳酸盐岩体系内岩溶碳汇效应的影响,以贵阳市花溪区历史降水量为参照,选取贵阳市青岩镇纯灰岩发育土壤与贵阳市花溪水库三叠纪大冶组纯灰岩为样本进行淋溶试验。测定了6个月时长内不同酸度降水﹑不同土壤深度下模拟石灰土—碳酸盐岩体系降水淋出液的HCO3-﹑DOC含量和土壤呼吸速率,研究了模拟酸雨对石灰土-石灰岩体系碳汇的影响。结果表明:（1）在土壤深度10～50 cm匀质状态的样本中,随着土壤厚度的增加,淋出液中HCO3-含量逐渐增大﹑DOC含量逐渐减小﹑土壤呼吸速率逐渐增大,显示出土壤厚度对石灰土—碳酸盐岩体系的碳汇效应有着明显的影响;(2)在pH=3.5~6.8的范围内,降水酸度的增强可以抑制岩溶作用与有机碳的溶解,并降低岩溶碳汇效应;（3）在日降水量90～230 mm范围内,随着降水量的增大碳汇效应也会随之增强。      

Effect of simulated acid rain on soil acidification and rare earth elements leaching loss in soils of rare earth mining area in southern Jiangxi Province of China

Acid rain has long been a great concern because of environmental and ecological problems; however, the effect of acid rain on soil acidification, loss of rare earth elements (REEs) via the leaching process, and transformation are rarely reported in rare earth mining areas. Through a simulated acid rain leaching experience, the effect of acid rain was studied on soil acidification and REEs leaching loss. The results showed that the tested soil had certain buffering capacity against nearly neutral rainwater. However, simulated acid rain of low and very low pH (pH ≤ 3.5) had a greater impact on soil acidification. After eluviating by simulated acid rain of pH 3.5 for 36 h, the pH of tailings, garden soil, paddy soil, and alluvial soil decreased by 20.41, 32.03, 13.60, 16.88, and 15.83 %, respectively, from the original values. For simulated acid rain of pH 2.5, it was 31.89, 44.76, 31.26, 29.87, and 29.15 %, respectively. After simulated acid rain eluviations of low and very low pH (pH ≤ 3.5), the order of the leaching rate of REEs in the tested soil was as follows: garden soil > tailings > paddy soil > alluvial soil. For nearly neutral rainwater (pH 4.5 simulated acid rain and pH 5.6 deionized water), the order was tailings > garden soil > paddy soil > alluvial soil. For simulated acid rain of the same pH, the leaching amounts of REEs in tailings and garden soil were higher than those in paddy soil and alluvial soil. After leaching by low and very low pH-simulated acid rain (pH ≤ 3.5), the peak value of the leaching amount of REEs in all tested soil appeared at 2 h, and then gradually reduced and reached a stable leaching state 20 h after leaching. On leaching by simulated acid rain of pH 2.5, the maximum REEs contents of leachate in tailings, garden soil, paddy soil, and alluvial soil were 156.35, 145.82, 99.88, and 85.97 mg/L, respectively. For pH 3.5 of simulated acid rain, it was 130.49, 110.49, 80.57, and 62.73 mg/L, respectively. On leaching by simulated acid rain of pH 4.5, the maximum contents of REEs in the leachate were 53.46 and 29.82 mg/L, respectively, which were observed after leaching for 6 h in tailings and garden soil that became stable 12 h after leaching. The contents of leached REEs in paddy soil and alluvial soil were always in a lower and stable state. After eluviations with deionized water of pH 5.6, the contents of leached REEs in other soils were lower, except for the slight fluctuations in tailings. The maximum content in the leachate of REEs was in the water-soluble and exchangeable fraction. When bound to carbonate fractions, REEs were not detected in the leachate. REEs bound to iron-manganese (Fe–Mn) oxides fraction and to organic matter fraction in the leachate possibly came from the tested soil or from the REEs transformation during the migration process. The content of residual fraction REEs in the leachate was very low.     

高强度模拟酸雨量对珠三角地区潮土中重金属元素释放的影响

采用平均离子强度下30年雨量的模拟酸雨淋滤珠江三角洲潮土,电感耦合等离子体质谱法测定重金属元素,研究潮土0~90 cm处各节土壤柱中重金属镉、钴、铜、锌、铅、砷、钛、钒、铬、锰等元素的释放情况。研究表明,在高强度模拟酸雨淋滤下,潮土中重金属元素的释放情况存在较大差异。长期的酸雨淋滤,土壤中的镉、钴、铜、锌和铅在不同深度均有不同程度的淋失;砷、钛、钒、铬、锰等元素不会造成大量的淋失。利用这种差异可以评估重金属元素对环境的潜在影响,为农田生态系统的预警预测提供依据。     

Experimental simulation and dynamic model analysis of Cadmium(Cd) release in soil affected by rainfall leaching in a coal-mining area

In order to explore the influence of rainfall on the release of heavy metal Cadmium(Cd)in soil in a coal-mining area,soil column leaching experiments were carried out by simulating 3 types of rainfall(acid rain,normal rainfall,and actual rainfall)with 5 different pH values(4,5,6,6.7,7),and 65 groups of data about leachate pH value and Cd concentration were obtained respectively.The results indicate the general change rule of Cd concentration in leachate:(1)the easiness of Cd release is negatively correlated to the pH value of leaching solution and positively correlated the leaching amount;(2)leaching solution with lower pH values shows more obvious release stages.Leached by solution with different pH values,the release of Cd in soil ranks as follows:Acid rain group>normal rainfall group>actual rainfall group.In the first stage,the acidity of rainfall has a significant impact on the release of Cd in soil,but in the second stage,the release of Cd is alleviated due to the soil buffering.Among the four dynamic equations to simulate the release of Cd in soil,the modified Elovich equation can describe the process most accurately,with the highest coefficient of determination R2 of 0.9975.These results can serve as a reference for further study on the migration,transformation and enrichment of Cd in soil.     

Mobility of trace and potentially harmful elements in the environment from high sulfur Indian coal mines

Coal mine rejects and sulfide bearing coals are prone to acid mine drainage (AMD) formation due to aqueous weathering. These acidic effluents contain dissolved trace and potentially harmful elements (PHEs) that have considerable impact on the environment. The behavior of these elements in AMD is mainly controlled by pH. The focus of the present study is to investigate aqueous leaching of mine rejects for prediction of acid producing potential, rates of weathering, and release of PHEs in mine drainage. Mine reject (MR) and coal samples from the active mine sites of Meghalaya, India typically have high S contents (1.8–5.7% in MR and 1.7–4.7% in coals) with 75–90% of the S in organic form and enrichment of most of the PHEs in rejects. Aqueous kinetic leaching experiments on mine rejects showed high acid producing potential and release of trace and potentially harmful elements. The elements (Sb, As, Cd, Cr, Co, Cu, Pb, Mn, Ni, V and Zn) in mine sample leachates are compared with those in mine waters. The concentrations of Al, Si, P, K, Ti, Mn, Fe, Co, Ni, Cu, Zn and Pb are found to increase with leaching time and are negatively correlated with pH of the solution. The processes controlling the release of these elements are acid leaching, precipitation and adsorption. The critical loads of PHEs in water affected by AMD are calculated by comparing their concentrations with those of regulatory levels. The Enrichment Factors (EFs) and soil pollution indices (SPIs) for the elements have shown that PHEs from coal and mine reject samples are mobilized into the nearby environment and are enriched in the associated soil and sediment.     

Interaction of organic acids and pH on multi-heavy metal extraction from alkaline and acid mine soils

Vegetation at mining sites can produce increased heavy metal leaching by the organic acids and protons originating from root secretion and litter degradation. Batch experiments were conducted to investigate the effects of organic acids and pH on the extraction of Pb, Cd, Zn and Cu from an alkaline mine soil (sampled from a mining site of Chenzhou City, Hunan Province) and an acid mine soil (sampled from a mining site of Daxin county, Guangxi Province). The results showed that in the presence of organic acids (acetic, oxalic, malic, fumaric, tartaric and citric acids) at pH 7, the extraction of Pb, Cd, Zn and Cu from the acid mine soil was much higher than that from the alkaline mine soil, in which only citric acid with higher concentration was capable of extracting some heavy metals. Citric acid had the strongest ability in extracting heavy metals, followed by oxalic acid. Heavy metal extraction dramatically decreased with increasing pH. Moreover, at low pH, oxalic acid promoted the risk of Cu leaching; at high pH, the leaching of Pb, Zn, Cd and Cu was enhanced by both oxalic and citric acids. This indicated that those plants, which can produce substantial citric acid or oxalic acid by root secretion and litter degradation, should not be selected for the revegetation of mining sites.     

Sequential extraction and leaching characteristics of heavy metals in abandoned tungsten mine tailings sediments

The chemical speciation of potentially toxic elements (As, Cd, Cu, Pb, and Zn) in the contaminated soils and sulfides-rich tailings sediments of an abandoned tungsten mine in Korea was evaluated by conducting modified BCR sequential extraction tests. Kinetic and static batch leaching tests were also conducted to evaluate the potential release of As and other heavy metals by acidic rain water and the leaching behaviors of these heavy metals. The major sources of the elements were As-, Zn- and Pb-bearing sulfides, Pb carbonates (i.e., cerussite), and Pb sulfates (i.e., anglesite). The biggest pollutant fraction in these soil and tailing samples consists of metals bound to the oxidizable host phase, which can be released into the environment if conditions become oxidative, and/or to residual fractions. No significant difference in total element concentrations was observed between the tailings sediments and contaminated soils. For both sample types, almost no changes occurred in the mobility of As and the other heavy metals at 7 days, but the mobility increased afterwards until the end of the tests at 30 days, regardless of the initial pH. However, the mobility was approximately 5–10 times higher at initial pH 1.0 than at initial pHs of 3.0 and 5.0. The leached amounts of all the heavy metal contents were higher from tailings sediments than from contaminated soils at pH > 3.0, but were lower at pH < 3.0 except for As. Results of this study suggest that further dissolution of heavy metals from soil and tailing samples may occur during extended rainfall, resulting in a serious threat to surface and groundwater in the mine area.     

溶解性有机质对冻融作用下污染土壤中重金属Pb的溶出释放规律

采用室内模拟实验方法研究了溶解性有机质（DOM）对冻融作用下污染土壤中重金属Pb的溶出规律。结果表明：冻融作用明显改变了土壤基本理化性质和重金属Pb的化学形态;与未冻融土壤相比,DOM明显促进了冻融土壤中Pb的溶出释放。DOM对污染土壤中Pb的溶出释放作用与土壤类型、土壤污染时间和污染程度有关：DOM对棕壤中Pb的溶出释放作用大于对黑土中Pb的溶出释放作用;而且随着土壤Pb污染时间越长和污染程度越重,DOM对土壤中Pb的溶出释放作用越大。DOM对土壤中Pb的溶出释放还与DOM质量浓度、性质和组成密切相关：DOM质量浓度的增加提高了污染土壤中Pb的溶出释放;DOM的低pH和小分子量亲水性组分利于土壤中Pb的溶出释放。     

煤矸石井下填充对矿井水的污染及其吸附控制模拟实验

以焦作煤矿区演马矿煤矸石为例，采取连续淋溶方式，模拟井下填充过程中煤矸石对地下水的污染，并利用土壤的吸附性能对矸石中溶出的污染因子进行控制。检测了淋溶水中的pH值、氟、总硬度、锰、铅、镉等6个因子，其中铅、镉未检出。实验表明，pH值、氟、总硬度变化范围均符合地下水Ⅲ类标准。锰是造成地下水污染的主零因子，考虑到累积效应，氟也有可能影响地下水质。控制实验显示，利用当地土壤的吸附性能对矸石中溶出的污染因子进行控制是可行、有效的，且分层填充比混合填充的控制效果好。     

An experimental study of heavy metal attenuation and mobility in sandy loam soils

Column flow-through experiments reacting wastewater solutions with sandy loam soil samples were performed to study heavy metal attenuation by two soils with different physical and chemical properties. Reacted soil columns were leached with synthetic acid rain to study the mobility of attenuated heavy metals under leaching conditions. This study demonstrates that cation exchange, surface adsorption, chelation with solid organic material, and precipitation were the important attenuation mechanisms for the heavy metals (Cd, Cr, Cu, Mo, Ph, and Zn). Adsorption on soil hydrous oxide surfaces was the primary attenuation mechanism for Cd and Zn in both soils, and for Cu in a soil with low organic matter content. Wastewater solution pH is also an important factor that influences the retention of heavy metals. Cadmium, Cu, Cr, and Zn became mobile after prolonged application of spiked wastewater solution, either through saturation of soil adsorption sites or due to decreasing pH. Only Cr, Pb, and Mo, which are attenuated primarily through precipitation, show significant net retention by soil. Acid rain water removed heavy metals left in the column residual pore solution and weakly sorbed heavy metals in the soils, and has the ability to mobilize some strongly attenuated heavy metals, especially when the soil organic matter content is high. The results have important applications in predicting heavy metal mobility in contaminated soil, the disposal of acid mine drainage, and assessing the risks of landfall leachate leakage.