电化学循环井驱动模拟含水层化学氧化降解三氯乙烯

传统原位化学氧化地下水修复技术存在氧化剂迁移距离短和利用率低等问题。本研究在双井循环模式促进传质的基础上,通过注水井中的地下水电解原位提供O₂和H₂,配合乙二胺四乙酸(ethylenediamine tetraacetic acid,EDTA)络合溶解出含水层Fe(Ⅱ),活化O₂产生羟基自由基(•OH),实现地下水三氯乙烯(TCE)的氧化降解。在填充了砂土和黏土互层的二维砂槽中,设置电流为0.2 A、流速为72 cm/d、初始TCE浓度为3 mg/L,经过9 d的连续通电处理后,TCE浓度降低到1 mg/L,降解率达到67%。通电前投加0.5 mmol/L EDTA,经过1 d水流循环后含水层中溶解态Fe(Ⅱ)浓度从02 mg/L增加到414 mg/L,黏土区域较高。通电过程中,循环井促进O₂、Fe(Ⅱ)-EDTA和TCE的有效接触与反应,使TCE氧化降解。通电初期,黏土区域Fe(Ⅱ)氧化速率、TCE降解速率较周围慢,后期差异逐渐减小。未通电时加入醋酸钠可促进Fe(Ⅲ)还原,使含水层中铁循环利用。该修复过程通过循环井提升了氧化剂迁移距离,使用源于含水层的Fe(Ⅱ)-EDTA和稳定性较好的O₂提高了氧化剂利用率,有望应用于有机污染地下水修复。     

电化学-水动力循环耦合井内生物反应器去除地下水中苯胺

为使含水层中苯胺污染的原位修复过程高效安全且不产生二次污染,提出了一种电化学-水动力循环下的井内生物反应器修复地下水中苯胺的方法.在水动力循环系统的驱动下,评价了苯胺在水动力循环系统的挥发情况并且通过电化学手段提供氧气,井内生物反应器提供修复载体,在砂槽模拟的含水层体系中开展井内生物反应器降解苯胺的修复实验,并对生长曲线及含水层中苯胺修复进行了模拟.289 h的修复使体系内苯胺平均浓度从298 mg/L降低到132 mg/L,去除率为56.5%.运行过程中,监测点苯胺平均浓度在48 h内去除速率为1.10 mg/（L·h）,48~72 h内去除速率为0.85 mg/（L·h）,72 h到289 h内苯胺去除速率维持在0.65 mg/（L·h）,氧化降解逐步减弱.该过程符合Michaelis-Menten方程,反应速率为:-6.71×10-7/（15+t）2.该修复系统是基于地下水动力循环技术的改进,有望应用于有机污染地下水修复.      

壳聚糖包覆纳米铁镍双金属的迁移性能及其降解地下水中三氯乙烯的研究

地下水中三氯乙烯(TCE)严重威胁公众健康和环境安全,纳米零价铁原位注射技术可以还原降解TCE,但是应用中,纳米零价铁存在易氧化团聚而失活、迁移性差等问题。为此,利用天然高分子壳聚糖作包覆剂增强分散性和稳定性,镍作催化剂增强反应活性,成功制备获得壳聚糖包覆纳米铁镍双金属颗粒(CS Fe Ni)。沉降光谱实验表明包覆壳聚糖后纳米铁的分散稳定性得到增强,Zeta电位测试进一步证实颗粒表面负电荷增加,提高了静电排斥力,使得CS Fe Ni分散稳定性明显改善。柱迁移实验表明改性后的CS Fe Ni迁移能力得到提高。批实验表明CS Fe Ni能够高效降解TCE并能完全脱氯,研究结果为纳米铁原位注射技术的实际应用提供了理论基础和实验参考。     

地下水中三氯乙烯-苯酚的好氧共代谢的实验研究

以苯酚作为三氯乙烯（TCE）降解的共代谢基质,用瓦勃氏微量呼吸测压仪（简称瓦呼仪）作为测试手段,分析了经苯酚驯化后的混合微生物对苯酚、TCE的降解特性;并讨论了以苯酚作为共代谢基质时TCE降解的可能性。实验结果表明：未驯化的活性污泥不能降解TCE; 经苯酚驯化后的活性污泥,当TCE的质量浓度为50 μg/L时其降解效果较好,TCE的氧化率达3369%;TCE的质量浓度为100 μg/L时其降解效果较差,其氧化率仅为3.2%;苯酚和TCE共代谢降解时,苯酚的存在促进了TCE的降解,当苯酚质量浓度为40 mg/L、TCE质量浓度为50 μg/L时共代谢降解效果最好,TCE的氧化率为79.11%。     

微生物电化学体系中金红石可见光还原降解偶氮染料的实验研究

利用双室微生物电化学装置对微生物和半导体矿物协同作用下偶氮类染料废水的还原脱色降解进行了系统的实验研究.不同光照条件及不同阴极电极材料的对比实验结果显示,偶氮染料甲基橙(MO)可作为终端电子受体直接从固体电极上获得电子被还原脱色;各对比实验中,在微生物催化与半导体矿物光催化协同作用条件下,MO还原脱色效率最高.电化学交流阻抗谱(EIS)的拟合结果显示金红石涂布阴极电极光照下极化内阻(Rp)为443.4 Ω,较无光条件下的1378 Ω显著降低,证明光照下金红石阴极的电子转移过程受其光催化作用的驱动.不同初始浓度下MO的生物-半导体催化还原反应符合准一级动力学模型,其反应速率随MO初始浓度降低而增加.通过对脱色产物的进一步分析,推测该实验中MO的还原脱色反应机制为: 阳极初始电子供体在微生物的催化作用下将电子通过阳极电极和外电路传递给阴极半导体矿物电极,进而在半导体矿物的光催化作用下通过光生电子还原终端电子受体MO,使MO中的偶氮键断裂,生成无色的联氨类衍生物.     

应用地球化学模式恢复准噶尔盆地东部浅层地下水的氧化-还原环境

地下水的ＥｈＷ值是反映其氧化还原能力的水文地球化学参数,是确定铀氧化还原环境必不可少的参数之一。在准噶尔盆地东部进行１∶５０万层间氧化带砂岩型铀矿床区调时,受工作条件限制,没能对所采集到的水样进行ＥｈＷ值测定,因而影响了对水的氧化还原能力的评价,但是这批水样分析资料中的Ｆｅ２＋／Ｆｅ３＋是非常有用的氧化还原电对,可用来模拟计算地下水环境的ＥｈＷ值。详细讨论了应用地球化学模式来模拟计算地下水ＥｈＷ值的原理和结果。     

秦岭大巴山地区紫阳毒重石矿床成因: 矿石组构、氧化还原敏感元素和碳-氧同位素证据

秦岭大巴山地区钡矿资源极为丰富,以蕴含世界罕见的层状毒重石矿床为特色。本研究在紫阳毒重石矿床中发现了玫花瓣状结构,经显微镜观察和电子探针分析表明,玫花瓣体由板柱状重晶石呈放射状排列而成,与前人报道的矿物组成明显不同。紫阳灰黑色毒重石矿石有较高的V、Ni、Cr、U、Mo含量,较低的Th/U比值(<0.04),较高的V/(V+Cr)比值(>0.8)和V/(V+Ni)比值(>0.9),指示寒武纪紫阳毒重石矿床的沉积环境为较还原的环境。紫阳毒重石矿石的C同位素分布在-10.9‰~-16.0‰, O同位素分布在18.1‰~22.3‰之间,表明毒重石中CO₃^2-是有机质通过氧化作用或脱羧基(生物有机质降解)作用提供的低¹³C的碳与同期海水提供的高¹³C的水溶性HCO₃^-或CO₃^2-的混合来源。综合研究表明,该区毒重石矿床的形成可能与寒武纪早期的海底热液成矿作用有关。     

康滇古陆西侧早志留世古海洋氧化-还原环境及优质烃源岩发育模式——以盐源地区CYD2井为例

在系统的地质调查和沉积学、地球化学研究的基础上, 以康滇古陆西侧盐源盆地南缘CYD2井龙马溪组为研究对象, 探讨早志留世古氧化还原环境、古水文条件、热液影响及有机质富集因素, 总结优质烃源岩发育模式, 为该区优质烃源岩预测提供基础。研究表明: 盐源地区优质烃源岩发育于龙马溪组下部(L1~L3), 经历了由初期(L1)滞留程度较高的硫化环境到晚期(L5)较开阔氧化环境的演化过程; 且在志留纪早期古海洋遭受了强烈的热液活动影响, 表现为轻稀土元素显著富集, Ce略有亏损, Eu显著富集。康滇古陆早期构造演化造成了强烈的热液活动和差异隆升, 控制盐源地区龙马溪初期古海洋氧化还原特征及海盆局限程度, 与海平面持续上升共同控制了盐源地区志留纪龙马溪期古海洋环境及优质烃源岩的形成和分布。     

地下水循环井修复技术发展现状综述

地下水循环井修复技术（GCW）是通过为地下水创造三维环流来进行地下水修复的新型原位修复技术。本文阐述了该技术在国内外的发展现状,介绍了真空气化井系统、气流提升井系统和密度驱动对流井系统的特点、优势和适用条件以及它们在实际工程的应用情况。针对地下水循环井修复技术目前存在的修复范围小、修复时间长、场地要求高、抽注不平衡等问题,提出需要在大范围水力调控、原位生物修复、多相同步修复、一体化智能设备等方面对该技术进行改进的建议。     

A model for coupled sulfate reduction and methane oxidation in the sediments of Saanich Inlet

A methane-sulfate coupled reaction diffusion model has been developed to describe the inverse relationship commonly observed between methane and sulfate concentrations in the pore waters of anoxic marine sediments. The sediment column was divided into two zones; an upper zone where diagenetic reaction rates are limited by the concentration of oxidizable organic matter and a lower zone in which reaction rates are limited by the concentration of oxidizing agent—sulfate. For each zone differential equations describing the distribution of methane and sulfate were derived. The boundary conditions used to solve these equations resulted in a set of four coupled equations. When fit to data from Saanich Inlet (B.C., Canada) and Skan Bay (Alaska) the model not only reproduces the observed methane and sulfate pore water concentration profiles but also accurately predicts the methane oxidation and sulfate reduction rates. Maximum methane oxidation rates occur at the transition boundary from the upper to the lower layer. In Saanich Inlet sediments from 23 to 40% of the downward sulfate flux is consumed in methane oxidation while in Skan Bay this value is only about 12%.     

Denitrification coupled to pyrite oxidation and changes in groundwater quality in a shallow sandy aquifer

This study focuses on denitrification in a sandy aquifer using geochemical analyses of both sediment and groundwater, combined with groundwater age dating (³H/³He). The study sites are located underneath cultivated fields and an adjacent forested area at Oostrum, The Netherlands. Shallow groundwater in the region has high nitrate concentrations (up to 8 mM) due to intense fertilizer application. Nitrate removal from the groundwater below cultivated fields correlates with sulfate production, and the release of dissolved Fe²⁺ and pyrite-associated trace metals (e.g. As, Ni, Co and Zn). These results, and the presence of pyrite in the sediment matrix within the nitrate removal zone, indicate that denitrification coupled to pyrite oxidation is a major process in the aquifer. Significant nitrate loss coupled to sulfate production is further confirmed by comparing historical estimates of regional sulfate and nitrate loadings to age-dated groundwater sulfate and nitrate concentrations, for the period 1950-2000. However, the observed increases in sulfate concentration are about 50% lower than would be expected from complete oxidation of pyrite to sulfate, possibly due to the accumulation of intermediate oxidation state sulfur compounds, such as elemental sulfur. Pollutant concentrations (NO₃, Cl, As, Co and Ni) measured in the groundwater beneath the agricultural areas in 1996 and 2006 show systematic decreases most likely due to declining fertilizer use.     

Feasibility of nitrate reduction combined with persulfate oxidation in the remediation of groundwater contaminated by gasoline

Hydrogeology Journal - Enhanced bioremediation combined with in-situ chemical oxidation has the potential to remediate groundwater contaminated with organics. To explore the remediating effects of...     

Deep groundwater circulation in Hercynian basement

Observations in deep drillholes reveal slow but extensive movement of crustal fluids. Geothermal observables and their interpretation by modelling heat- and mass-transfer yield flow-rates and penetration depths of deep groundwater circulation. As examples, two sites in Hercynian terranes are examined: 1) northern Switzerland and 2) KTB (Kontinentales Tiefbohrprogramm) in Germany. Flow rates are of the order of liters per square meter per year for both sites; depth of penetration is different (5 km and 0.5 km, respectively). Received: 3 September 1996 / Accepted: 17 December 1996     

Correction: Feasibility of nitrate reduction combined with persulfate oxidation in the remediation of groundwater contaminated by gasoline

Hydrogeology Journal -     

Modelling coupled heat and contaminant transport in groundwater

This paper presents the results of a research programme conducted on the geotechnical centrifuge at The University of Western Australia to investigate coupled heat and contaminant transport in the soil surrounding a buried waste source. The phenomena which govern heat and contaminant transport through porous media are discussed, the principles of geotechnical centrifuge modelling are outlined, and relevant scaling laws that govern the relationship between a centrifuge model and the prototype, with respect to the problem of coupled waste transport, are presented. A model test, simulating two-dimensional migration from a buried heat and contaminant source, is described, and the results from four model tests are presented. The experimental data show that hydraulic instability is responsible for the transport of contaminant in the soil around the source and that the mode of instability is determined by the magnitude of the effective Rayleigh number.     

Nitrate in groundwater and N circulation in eastern Botswana

Nitrate pollution due to deep leaching from pit latrines has caused water supply wells in eastern Botswana to exceed health limits concerning nitrate. It was deduced from the estimated intake of salt and protein by the population that, as an average, about 10 percent of the human nitrogen excretion is leached to the groundwater. This fraction was also found in southern India, where on-the-ground excretion is customary. The nitrogen circulation in general in the savanna ecosystem is not appreciably affected in spite of a large livestock density. Overall nitrate leaching is in the order of 1.5 kg N/ha/y, similar to that in another semiarid area in southern India. However, in India, there seems to be a more diffuse areal leaching from agriculture as well as from villages.Measures to minimize the nitrate leaching could be to plant deep-rooted trees adjacent to pit latrines or to use latrines that separate the urine from the faces for a more near-surface infiltration facilitating plant uptake. Measures to minimize leaching will also lessen the rick for bacterial pollution of the groundwater.     

地下水循环结构的动力学研究进展

由地下水补给、径流和排泄过程构成的地下水循环运动,是水文循环的重要组成部分,也是水文地质学的基本研究对象.地下水循环在空间上表现为不同结构单元的组合,存在以含水层特性为依据的介质结构和以渗流场为依据的动力结构2种划分方法.地下水流系统是动力结构意义上的地下水循环单元.近10年来,区域地下水流系统理论取得了显著进展,更加全面深入地揭示了地下水循环结构的动力学特性.通过对河间地块地下水流系统的研究,发现潜水面最高点并非地下水分水岭的准确位置.在盆地尺度上,系统研究了沟谷地貌、降水入渗强度、渗透性随埋深变化和盆地厚度等因素对潜水面波形与地下水循环动力结构的影响,初步发现了动力结构的周期性或趋势性演化特征.通过大规模流线路径的精细识别或驻留时间的统计分析,提出了三维地下水循环单元的划分方法.在水文地质效应方面,发现地下水循环的动力结构对地下水年龄的分布有重要影响.地下水循环的动力结构反映了不同补给区和排泄区之间的水力联系,在盆地尺度地球化学过程、流域尺度生态水文过程中发挥着关键作用,未来的研究重点是三维地下水循环的动力特性和演变规律.