Natural groundwater of a gas field utilizable for a bioremediation of trichloroethylene-contamination

Groundwater from a shallow aquifer in Mobara, a city in a natural gas field in Chiba Prefecture, Japan, was found to contain a significant amount of dissolved methane (<3.1 mM) along with nitrate, phosphate and methane-oxidizing bacteria (methanotrophs, <9.9×10⁶ MPN ml^–1) which can degrade trichloroethylene (TCE). This water exhibited high methanotroph growth activity and rapid degradation of TCE. This water was introduced into a TCE-contaminated aquifer. The concentration of TCE at the monitoring well 2 m down-gradient of the injection pit decreased from 128 g L^–1 before the injection to less than the lower detection limit of 12.5 g L^–1 after the injection, while it decreased only slightly (to 86 g L^–1) when control water was injected. These results demonstrate the feasibility of utilizing a natural groundwater resource containing methane and methanotrophs without any additives for bioremediation of a TCE-contaminated site.     

The application of isotope and chemical analyses in managing transboundary groundwater resources

Managing transboundary groundwater resources requires accurate and detailed knowledge of aquifers and groundwater bodies. The Pannonian Basin is the largest intracontinental basin in Europe with a continuous succession of more than 7 km of Miocene to Quaternary sediments and with an average geothermal gradient of about 5 °C/100 m. Geographically the Pannonian basin overlaps eight countries (Hungary, Romania, Serbia, Croatia, Slovenia, Austria, Slovakia and Ukraine), so the issue of transboundary cold and thermal water resources is regionally very important. The T-JAM bilateral Hungarian–Slovenian (HU–SLO) project is the first to apply modern isotopic and chemical analyses in the characterization and correlation of a number of shared groundwater resources in the Mura-Zala Sub-basin of the Pannonian. The aims of this work were the identification of groundwater flow paths, the delineation of transboundary aquifers based on thermal and cold groundwater geochemical and isotope properties in the Mura-Zala Basin, and providing input to calibrate a hydraulic numerical model. Following a common groundwater sampling campaign, 24 cold and thermal groundwater samples from seven aquifers were collected for chemical, isotope, gas and noble gas analyses. Chemical analyses, and D, O and C isotopes were used to correlate cross border aquifers. A regional groundwater flow is hydrogeologically possible in some aquifers in the Mura-Zala Basin, and has been confirmed by hydrogeochemistry. The Újfalu (HU) and Mura (SLO) Formations are a part of the active regional thermal groundwater flow system, probably hydraulically separated from the shallower flow system of the Ptuj-Grad (SLO), Zagyva and Somló-Tihany (HU) Formations. The thermal water is of meteoric origin, reductive and alkaline. The predominant water type in the Quaternary and Pliocene aquifers is Ca–Mg–HCO₃, changing to Na–HCO₃ in the main Pannonian geothermal aquifer, and Na–Cl brine in deeper and older Miocene aquifers. Total dissolved solids and Na content generally increase with depth. Deuterium is in the range −87‰ to −75‰, ¹⁸O from −11.9‰ to −10.4‰, while ¹⁴C values are less than 6.1 pmC in the samples of the active regional thermal groundwater flow system. These and results of noble gas analyses indicate recharge during the Pleistocene interglacial period with temperatures around 6–7 °C. Regional thermal water resources are limited and environmental isotopes can be used as an early warning in the management of thermal water.     

Chloroaromatics in groundwater: chances of bioremediation

. The potential for biodegrading of mono-, di- and trichlorobenzenes in a contaminated aquifer in Bitterfeld (Saxony-Anhalt) was tested both in the laboratory and using on-site column experiments. Under the prevailing anaerobic conditions, the reductive dechlorination of 1,4-dichlorobenzene (1,4-DCB) takes place very slowly. Under aerobic conditions the indigenous micro-organisms are able to mineralize monochlorobenzene (MCB) and 1,4-DCB. The degradation rates for the other two isomeric dichlorobenzenes and for 1,2,4-trichlorobenzene (1,2,4-TCB) under aerobic conditions are significantly lower. Indications were found that once the oxygen has been consumed, Fe(III) species can be used as alternative electron acceptors.     

Intrinsic bioremediation of MTBE-contaminated groundwater at a petroleum-hydrocarbon spill site

An oil-refining plant site located in southern Taiwan has been identified as a petroleum-hydrocarbon [mainly methyl tert-butyl ether (MTBE) and benzene, toluene, ethylbenzene, and xylenes (BTEX)] spill site. In this study, groundwater samples collected from the site were analyzed to assess the occurrence of intrinsic MTBE biodegradation. Microcosm experiments were conducted to evaluate the feasibility of biodegrading MTBE by indigenous microorganisms under aerobic, cometabolic, iron reducing, and methanogenic conditions. Results from the field investigation and microbial enumeration indicate that the intrinsic biodegradation of MTBE and BTEX is occurring and causing the decrease in MTBE and BTEX concentrations. Microcosm results show that the indigenous microorganisms were able to biodegrade MTBE under aerobic conditions using MTBE as the sole primary substrate. The detected biodegradation byproduct, tri-butyl alcohol (TBA), can also be biodegraded by the indigenous microorganisms. In addition, microcosms with site groundwater as the medium solution show higher MTBE biodegradation rate. This indicates that the site groundwater might contain some trace minerals or organics, which could enhance the MTBE biodegradation. Results show that the addition of BTEX at low levels could also enhance the MTBE removal. No MTBE removal was detected in iron reducing and methanogenic microcosms. This might be due to the effects of low dissolved oxygen (approximately 0.3 mg/L) within the plume. The low iron reducers and methanogens (<1.8×10³ cell/g of soil) observed in the aquifer also indicate that the iron reduction and methanogenesis are not the dominant biodegradation patterns in the contaminant plume. Results from the microcosm study reveal that preliminary laboratory study is required to determine the appropriate substrates and oxidation-reduction conditions to enhance the biodegradation of MTBE. Results suggest that in situ or on-site aerobic bioremediation using indigenous microorganisms would be a feasible technology to clean up this MTBE-contaminated site.     

Biological and abiological processes in a simulated sedimentary system

A simulated sedimentary system, capable of being controlled and monitored for a considerable length of time without undue disturbance, has been assembled and applied to specific problems of the genesis of stratiform Pb‐Zn ore deposits. Results have been obtained relevant to: (i) the concentration of Pb and Zn from brines to underlying sediments; (ii) the behaviour of microorganisms in metal‐rich, highly saline environments; (iii) the precipitation diagenesis of calcium and magnesium carbonates; and (iv) the diagenesis of organic matter.

The experiment has demonstrated the feasibility of simulating a complex sedimentary environment in the laboratory and has indicated the potential of such systems for the investigation of geobiological problems.     

Geochemical analyses of geological layers and groundwater flows

X-ray fluorescent spectroscope analysis easily finds ratios of geochemical elements in soil. Applying the method of ratio matching to measured ratios, the classification of geological layers, and the flow directions of groundwater can be determined. This method is applied to three hill slopes in Japan and the results are in good agreement with the observations and measurements of soil cores obtained by drilling. The classification of geological layers is found to be quantitatively connected with the rates of organic matter in soil cores. Received: 5 February 1999 · Accepted: 7 September 1999     

Inferring the chemical parameters for the dissolution of fluoride in groundwater

Geochemical study of groundwater from 58 selected fluoride-rich areas in different parts of India that includes eight states indicates that: 1. These groundwaters are alkaline in pH (7.4-8.8) and their electrical conductivity varies from 530-2,680 µS/cm and fluoride concentration from 1.7-6.1 mg/l. Presence of fluoride-bearing minerals in the host rocks and their interaction with water is considered to be the main cause for fluoride in groundwater. 2. The decomposition, dissociation and dissolution are the main chemical processes for the occurrence of fluoride in groundwater. During rock-water interaction, concentration of fluoride in rock, aqueous ionic species and residence time of interaction, etc. are also important parameters. 3. This study indicates that 85% groundwater samples have EC: 1,000-2,000 µS/cm, pH: 7.5-8.5, and HCO₃/Ca (epm ratio): 0.8-2.3. 4. The Ca and HCO₃ contents of groundwater samples have shown good correlation with fluoride.     

Composition,stability, and measurement of reduced uranium phases for groundwater bioremediation at Old Rifle,CO

Reductive biostimulation is currently being explored as a possible remediation strategy for U-contaminated groundwater, and is being investigated at a field site in Rifle, CO, USA. The long-term stability of the resulting U(IV) phases is a key component of the overall performance of the remediation approach and depends upon a variety of factors, including rate and mechanism of reduction, mineral associations in the subsurface, and propensity for oxidation. To address these factors, several approaches were used to evaluate the redox sensitivity of U: (1) measurement of the rate of oxidative dissolution of biogenic uraninite (UO_2(s)) deployed in groundwater at Rifle, (2) characterization of a zone of natural bioreduction exhibiting relevant reduced mineral phases, and (3) laboratory studies of the oxidative capacity of Fe(III) and reductive capacity of Fe(II) with regard to U(IV) and U(VI), respectively.     

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。     

Preparation of integrative cubes as a novel biological permeable reactive barrier medium for the enhancement of in situ aerobic bioremediation of nitrobenzene-contaminated groundwater

Recent studies have indicated that in situ aerobic bioremediation is one of the most effective methods for remediating groundwater contaminated with nitrobenzene (NB). Aerobic bioremediation is largely dependent on the maintenance of adequate dissolved oxygen (DO) levels in the groundwater. Traditional in situ aeration has various disadvantages, such as high operational costs and nonuniform aeration. In this study, integrative cubes were prepared and utilized as a novel biological permeable reactive barrier (bio-PRB) medium to enhance the aerobic bioremediation of NB-contaminated groundwater. The results revealed an NB removal rate greater than 98.68% after 15–20 days of continuous oxygen release from the bio-PRB medium. DO concentrations reached 8.0 mg/L during treatment, and NB-degrading bacteria were able to tolerate a range of pH conditions. This multifaceted bio-PRB medium can simultaneously adsorb and biodegrade NB, release oxygen, and neutralize the pH with phosphate buffer. The results of this study suggest that this bio-PRB medium represents a highly effective in situ bioremediation method for NB-contaminated groundwater.     

江苏淮扬地区浅层地下水环境质量评价与分析

对淮扬地区浅层地下水环境质量进行了单组分评价和综合评价,分析了各项超标组分的形成机理。评价与分析结果显示:淮扬地区局部浅层地下水水质达不到饮用水标准。生态地质环境背景和人类活动导致该地区浅层地下水中多项指标超标。     

同位素技术解析安阳河与地下水相互作用

河流与地下水相互作用研究是水文学研究的难点和热点。安阳河与地下水相互作用研究,对于安阳市水资源科学开发与管理具有重要意义。安阳河冲洪积扇地表水与地下水转化率为17%～27%。潜水位标高为80 m,向下游逐渐变成多层含水层（水位40 m）。当地降水环境同位素监测数据表明,当地大气降水线与全球大气降水线接近平行,表明该线代表本地区大气降水的氢氧同位素特征。地表水同位素值较集中,2016年8月δ18O值变化范围为-9‰~-8.7‰,δD值变化范围为-65‰~-63‰,2017年1月δ18O值变化范围为-8.5‰~-8.2‰,δD值变化范围为-63‰~-61‰,河水水化学类型为HCO3·SO4—Ca型,表明流域内地表水的同位素值受距离的影响较小。地下水稳定同位素值变化较大,2016年8月δ18O值范围为-10.4‰~-5.5‰,δD值范围为-75‰~-46‰,2017年1月δ18O值范围为-10.2‰~-5.4‰,δD值范围为-75‰~-45‰,即从接近降水值到最大值形成一条“蒸发”线。河流出山口一带地下水同位素值呈现最大蒸发值,表明地表水补给地下水,地下水化学类型为HCO3·SO4·Cl—Ca,存在明显人为污染成分。下游为大气降水补给浅层地下水,中深层地下水主要来源于中游侧向径流,水化学类型主要为HCO3—Ca·Mg型,综合分析表明,安阳河中下游（冲洪积扇）地带“三水”转换积极,并影响其水质、水量。     

Comprehensive chemical analyses of natural cordierites: implications for exchange mechanisms

Cordierite samples from pegmatites and metamorphic rocks have been analysed for major [electron microprobe analysis (EMPA)] and trace elements [inductively coupled plasma mass spectrometry (ICP-MS), secondary ion mass spectrometry analyses (SIMS)] as well as for H₂O and CO₂ (coulometric titration), and the results evaluated in conjunction with published data in order to determine which exchange mechanisms are significant. Apart from the homovalent substitutions FeMg₋₁ and MnMg₋₁ on the octahedral site, some minor KNa₋₁ on the Ch0 channel site, and Fe³⁺Al₋₁ on the T₁1 tetrahedral site, the three most important substitution mechanisms are those for the incorporation of Li on the octahedral sites (NaLi□₋₁Mg₋₁), and of Be and other divalent cations on the tetrahedral T₁1 site (NaBe□₋₁Al₋₁ and Na(Mg,Fe²⁺)□₋₁Al₋₁). The dominant role of the last vector is clearly demonstrated. We propose a new generalized formula for cordierite: ^Ch(Na,K)_0–1 ^VI(Mg,Fe²⁺,Mn,Li)₂ ^IVSi₅ ^IVAl₃ ^IV(Al, Be, Mg, Fe²⁺, Fe³⁺)O₁₈ *x^Ch(H₂O, CO₂…). Our results show that the population of (Mg, Fe²⁺) on the T₁1-site is limited to about 0.08 a.p.f.u. Other exchange mechanisms that were encountered in experiments operate only under P–T conditions or in bulk compositions that are rarely realized in nature. Routine analyses by electron microprobe in which Li and Be are not determined can be plotted as (Mg+Fe+Mn) versus (Si+Al) to assess whether significant amounts of Li and Be could be present. These amounts can be calculated as Li (a.p.f.u.)=Al+Na–4 and Be (a.p.f.u.)=10–2Al–M²⁺–Na.     

Monitoring groundwater flow and chemical and isotopic composition at a demonstration site for carbon dioxide storage in a depleted natural gas reservoir

Between March 2008 and August 2009, 65,445 tonnes of ∼75 mol% CO₂ gas were injected in a depleted natural gas reservoir approximately 2000 m below surface at the Otway project site in Victoria, Australia. Groundwater flow and composition were monitored biannually in two overlying aquifers between June 2006 and March 2011, spanning the pre-, syn- and post-injection periods. The shallower (∼0–100 m), unconfined, porous and karstic aquifer of the Port Campbell Limestone and the deeper (∼600–900 m), confined and porous aquifer of the Dilwyn Formation contain valuable fresh to brackish water resources. Groundwater levels in either aquifer have not been affected by the drilling, pumping and injection activities that were taking place, or by the rainfall increase during the project. In terms of groundwater composition, the Port Campbell Limestone groundwater is brackish (electrical conductivity = 801–3900 μS cm⁻¹), cool (temperature = 12.9–22.5 °C), and near-neutral (pH = 6.62–7.45), whilst the Dilwyn Aquifer groundwater is fresher (electrical conductivity = 505–1473 μS cm⁻¹), warmer (temperature = 42.5–48.5 °C), and more alkaline (pH = 7.43–9.35). Carbonate dissolution, evapotranspiration and cation exchange control the composition of the groundwaters. Comparing the chemical and isotopic composition of the groundwaters collected before, during and after injection shows no statistically significant changes; even if they were statistically significant, they are mostly not consistent with those expected if CO₂ addition had taken place. The monitoring program reveals no impact on the groundwater resources attributable to the C storage demonstration project.     

Variations in the environmental characteristics of groundwater slightly contaminated with petroleum: effects of enhanced bioremediation in northeast China

The objective of this paper was to investigate a petroleum-contaminated groundwater site in northeast China. Based on the monitoring and analysis of environmental characteristics of groundwater slightly contaminated with petroleum, microbes were added into the petroleum-contaminated groundwater via single-well and multiple-well models to enhance bioremediation. The effect of enhanced bioremediation was monitored and analyzed, and variations in the environmental characteristics of groundwater containing total petroleum hydrocarbons (TPH) were identified to provide a scientific basis for controlling and remediating petroleum-contaminated groundwater. Findings confirmed that this site was slightly contaminated and TPH levels exhibited a slight decreasing trend. After enhanced remediation, the microbial degradation effect was large, and the TPH concentration significantly reduced. In particular, near the wells treated by bioremediation, the amounts of electron acceptors, such as NO₃ ^?, Fe³⁺, and SO₄ ^2?, markedly decreased. The product of the microbial degradation process, HCO₃ ^?, gradually increased in the treated wells. Activities of the enzyme catechol 1, 2-dioxygenase decreased, while those of catalase increased. Reductions in pH, from 7.4 to 6.1, were recorded, and the groundwater environment became further deoxidized.     

The variability of chemical analyses as a function of sample heterogeneity,and the implications to the analyses of rock standards

The errors in the chemical analyses of a granodiorite rock powder for 6 constituents (K ₂O, Na₂O, CaO,∑Fe₂O₃, MgO, and MnO) have been determined by replicate analyses of the whole rock and of a series of different sieved fractions. Sample inhomogeneity is indicated. This is confirmed by analyses of the fused rock powder. Fusion to a glass is therefore recommended for the preparation of geochemical rock standards.     

某化工场地土壤与地下水中多环芳烃的分布特征及迁移规律

选取某化工场地作为研究对象,采集不同深度的原状土壤样品和原状地下水样品,对土壤样品和地下水样品的16种优控多环芳烃进行定量分析,研究不同种类的多环芳烃在包气带和饱和带中的分布特征和迁移规律.研究表明,在平面上,多环芳烃在土壤和地下水中的污染高值区与生产车间分布基本一致;在垂向上,土壤中的16种多环芳烃集中分布在杂填土层...     

计算机水化学模型在地下水环境评价中的应用

介绍了基于平衡常数法的水溶液平衡组分分布的计算原理及其数学模型。在此基础上,以韩城电厂周原灰场区潜水环境为背景,对计算机水化学模型在地下水环境评价中的应用进行了探讨。与传统的水化学方法相比,该方法可以获得更多的信息,从而有助于分析地下水的化学特征及地下水与所处环境之间的关系和相互作用。