Organic Contaminants In Groundwater Research Articles

Transport Characteristics in a 3D Groundwater Circulation Flow Field by Experimental and Numerical Investigations

The groundwater circulation well (GCW) is one of the important in situ techniques used for the remediation of volatile organic contaminants (VOCs) in groundwater. The hydraulic flow field of the GCW permits physical and biological remediation of the saturated as well as the unsaturated subsurface region. The GCW is designed to remove VOCs from the groundwater by transferring the contaminants from the aqueous phase to the gaseous phase and subsequently treating the resulting air stream through carbon adsorption units. As the flow phenomena surrounding a GCW in a heterogeneous aquifer are very complex, the characterization of transport is very difficult. This paper presents the analysis of experimental tracer transport in a three-dimensional (3D) flow field induced by a GCW in an artificial aquifer at the research facility for groundwater and subsurface remediation, Versuchseinrichtung zur Grundwasser und Altlastensanierung (VEGAS), at University of Stuttgart, Germany. The circulation flow field within a he...

13C/12C Analysis of Ultra-Trace Amounts of Volatile Organic Contaminants in Groundwater by Vacuum Extraction

We developed a method for the vacuum extraction (VacEx) of volatile organic compounds (VOCs) from water samples for ultratrace determinations of carbon isotopic signatures. Our method permits compound-specific stable carbon isotope analysis (CSIA) at VOC concentrations as low as 0.03-1.34 microg/L. VacEx was developed to extract and preconcentrate VOCs for subsequent carbon-CSIA by the standard technique purge-and-trap (P&T) coupled to an isotope-ratio mass spectrometer (IRMS). Even without complete extraction, the delta(13)C signatures of VOCs determined by VacEx-P&T-IRMS were in good agreement (deviation <1 per thousand) with signatures determined by P&T-IRMS. This indicates that VacEx does not cause isotopic discrimination. Limits of quantification (LOQs) for delta(13)C analysis were: 0.03-0.06 microg/L for benzene, toluene, o-xylene, m-p-xylene and ethylbenzene, 0.09 microg/L for methyl tert-butyl ether (MTBE), and 0.18-0.27 microg/L for trans-DCE, cis-DCE, TCE and PCE. These are the lowest LOQs reported to date for continuous-flow isotope-ratio determinations using a commercially available and automated system. To our knowledge, analytical protocols adopted from noble gas analysis in water were applied for the first time to determine the isotope composition of organic contaminants. We applied VacEx in a field study to illustrate how the determination of VOC isotopic signatures at very low concentrations opens new avenues in the in situ assessment of these priority groundwater pollutants.

Reduction of Polychlorinated Ethanes and Carbon Tetrachloride by Structural Fe(II) in Smectites

Ferrous iron associated with clay minerals can be important for the reductive transformation of organic contaminants in anoxic soils and groundwaters. We investigated the reactivity of structural Fe(II) in ferruginous smectite for the reduction of a series of polychlorinated alkanes (hexa-, penta-, 1,1,1,2-and 1,1,2,2-tetrachloroethane, and carbon tetrachloride (CCl4)) in laboratory batch reactors. Evaluation of reaction kinetics, product distribution, and C-isotope fractionation suggest that polychlorinated ethanes containing three alpha-Cl atoms reacted via reductive beta-elimination to the corresponding ethenes while CCl4-reduction leads predominantly to the formation of chloroform. Reduction kinetics followed a typical biphasic behavior characteristic of the presence of two types of Fe(II) species exhibiting different reactivity in the octahedral sheet of smectites, and reaction rate constants were pH-independent. Dehydrochlorination reactions of chloroethanes containing at least one beta-H atom were found to compete with or even dominate over the reduction reaction with increasing suspension pH. Reference experiments in homogeneous solution and with non-reduced smectite performed in the pH range of 5.5-8.5 suggest that the HCl-elimination is not catalyzed at mineral surfaces. From the observed slow transformation of chloroalkanes, we hypothesize that structural Fe(II) in smectites will be important mainly as a reductant in the subsurface once iron(hydr)oxides have been reductively dissolved.

Monitored natural attenuation of organic contaminants in groundwater: principles and application

This paper reviews the conceptual and technical basis underpinning the use of monitored natural attenuation (MNA) for the management of organic contaminants in groundwater. MNA has important advantages over engineered remediation technologies for groundwater. Its significance will increase across the international community generally and its application for the management of petroleum hydrocarbons and other aromatic compounds will expand. Its application to other contaminants such as chlorinated solvents requires further qualification, although it has demonstrable potential for these. Long-term dissolution of non-aqueous-phase liquid (NAPL) sources is a major issue affecting remediation time-frames for MNA. Source zone remediation in conjunction with MNA will be required for many contaminated sites to meet typical regulatory time-frames permitted for MNA application. Internationally, there is general consensus in the scientific basis and assessment methods included in the technical guidance or protocols supporting the application of MNA. It is not a ’do-nothing’ remediation strategy, but requires site-specific characterisation, scientifically based analysis and a long-term commitment to monitoring, data collection and rigorous technical evaluation for ongoing performance assessment. Additional remediation technologies may be required to support MNA during the remediation programme and the decision to implement MNA should consider the large body of MNA literature that now exists and is summarised here.

Phytoremediation of Organic Contaminants in Soil and Groundwater

Phytoremediation is an emerging technology for the clean-up of sites contaminated with hazardous chemicals. The term phytoremediation refers to a number of technologies that use photoautotrophic vascular plants for the remediation of sites contaminated with inorganic and organic contaminants. Phytoremediation of organic contaminants can be organized by considering 1) the green liver concept, which elucidates the metabolism of contaminants in planta versus that of contaminants ex planta (e.g. rhizosphere), 2) processes that lead to complete degradation (mineralization) of contaminants as opposed to those that only lead to partial degradation or transformation, and 3) active plant uptake versus passive processes (e.g. sorption). Understanding of these processes needs an interdisciplinary approach involving chemists, biologists, soil scientists, and environmentalists. This Review presents the basic concepts of phytoremediation of organic contaminants in soil and groundwater using selected contaminants as examples.

System from Basin Water targets organic contaminants in groundwater

Basin Water Incorporated is offering photo-catalytic membrane systems to drinking-water providers in the USA through an agreement that it has formed with Purifics ES Incorporated of London, Ontario, Canada. The technology can effectively treat a broad range of organic contaminants in groundwater.

Dioxins, chlorophenols and other chlorinated organic pollutants in colloidal and water fractions of groundwater from a contaminated sawmill site

The distribution of chlorinated organic contaminants in groundwater and the importance of colloids were studied in groundwater from a sawmill site contaminated by chlorophenol preservatives. The groundwater was fractionated into three different size ranges: (1) >0.7 microm, (2) 0.4-0.7 microm and (3) 0.2-0.4 microm and the filtered water phase. The concentrations of chlorophenols (CP), chlorinated phenoxy phenols (PCPP), chlorinated diphenyl ethers (PCDE), chlorinated dibenzofurans (PCDF) and chlorinated dibenzo-p-dioxins (PCDD) were determined in each fraction. The colloids were characterised regarding the chemical composition using X-ray photoelectron spectroscopy (XPS). Chlorophenols were mostly found in the water fraction and PCDD/Fs were found almost exclusively in the particulate fractions. For example, the filtered water phase contained 2,100 microg l(-1) and 0.72 ng l(-1) for CPs and PCDD/Fs, respectively, and the particulate fractions contained 27 microg l(-1) and 32 ng l(-1) for CPs and PCDD/Fs, respectively. XPS evaluation of the particulate phases showed no correlation between the surface chemistry of the particle properties and the distribution of chlorinated compounds. The results suggest that groundwater transport of CPs, PCPPs, PCDEs and PCDD/Fs may occur from contaminated sawmill sites and that the colloid-facilitated transport, especially of PCDD/Fs, is substantial. The results correlated well with previous studies of compounds sorbed to dissolved organic carbon, which indicate that dissolved and colloidal organic carbon facilitated the transport of PCDEs, PCDFs and PCDDs particularly. Several classes of chlorinated compounds were readily detected in the groundwater samples. Due to the differences in their physicochemical properties, CPs, PCPPs, PCDEs and PCDD/Fs vary in their partitioning between colloidal fractions and the filtered groundwater. The proportion of the bound fraction increased with an increasing hydrophobicity of the chlorinated compounds. The groundwater transport of colloid-associated pollutants from the site may be significant. The results imply that colloidal particles <0.7 microm are freely mobile in groundwater from this site. The groundwater transport of colloid-associated pollutants may be significant. However, the extent of the problem is not yet known and, thus, further research is needed to evaluate the impact of colloidal transport of hydrophobic organic contaminants. In Sweden alone, 400 to 500 sawmill sites are estimated to be contaminated with PCDD/Fs as a result of the former use of CP-based wood preservatives. The widespread use of CP mixtures for a variety of applications, including wood preservation, indicates that potential colloidal transport will be an issue of concern in many countries.

Geochemical evaluation of metals in groundwater at long‐term monitoring sites and active remediation sites

AbstractAt many sites, long‐term monitoring (LTM) programs include metals as chemicals of concern, although they may not be site‐related contaminants and their detected concentrations may be natural. At other sites, active remediation of organic contaminants in groundwater results in changes to local geochemical conditions that affect metal concentrations. Metals should be carefully considered at both types of sites, even if they are not primary contaminants of concern. Geochemical evaluation can be performed at LTM sites to determine if the monitored metals reflect naturally high background and, hence, can be removed from the analytical program. Geochemical evaluation can also be performed pre‐ and post‐treatment at active remediation sites to document the effects of organics remediation on metals and identify the processes controlling metal concentrations. Examples from both types of sites are presented in this article. © 2008 Wiley Periodicals, Inc.

Simultaneous quantification of polar and non-polar volatile organic compounds in water samples by direct aqueous injection-gas chromatography/mass spectrometry

A direct aqueous injection-gas chromatography/mass spectrometry (DAI-GC/MS) method for trace analysis of 24 volatile organic compounds (VOCs) in water samples is presented. The method allows for the simultaneous quantification of benzene, toluene, ethyl benzene, and xylenes (BTEX), methyl tert-butyl ether (MTBE), tert-butyl alcohol (TBA), as well as a variety of chlorinated methanes, ethanes, propane, enthenes and benzenes. Applying a liquid film polyethylene glycol or a porous layer open tubular (PLOT) divinylbenzene GC capillary column to separate the water from the VOCs, volumes of 1–10 μL aqueous sample are directly injected into the GC. No enrichment or pretreatment steps are required and sample volumes as low as 100 μL are sufficient for accurate quantification. Method detection limits determined in natural groundwater samples were between 0.07 and 2.8 μg/L and instrument detection limits of <5 pg were achieved for 21 out of the 24 evaluated VOCs. DAI-GC/MS offers both good accuracy and precision (relative standard deviations ≤10%). The versatility of our method is demonstrated for contaminant quantification in drinking water disinfection (advanced oxidation of MTBE) and for VOC concentration measurements in a polluted aquifer. The wide range of detectable compounds and the lack of labor-intensive sample preparation illustrate that the DAI method is robust and easily applicable for the quantification of important organic groundwater contaminants.

Potential for Sample Bias Due to NAPL Partitioning

AbstractTetrachloroethene, trichloroethene, dichloroethenes, and vinyl chloride are collectively known as chlorinated ethenes. Chlorinated ethenes are some of the most prevalent organic ground water contaminants in North America and may develop large ground water plumes. If areas of free‐phase petroleum are present within the boundaries of a chlorinated ethene plume, consideration must be given to the interpretation of ground water samples due to interactions between chlorinated ethenes and the petroleum. Chlorinated ethene concentrations in ground water samples may be significantly greater than concentrations immediately upgradient of the free‐phase petroleum zone if any of the free‐phase petroleum is entrained in the sample due to turbidity or a sheen/layer of product. This occurs because a significant mass of chlorinated ethenes can partition into the petroleum. The bias due to the entrainment of petroleum in a ground water sample becomes significant if a visible thickness of petroleum or oily sediment occurs in the sample.

Sensitive Detection of Anaerobic Monochlorobenzene Degradation Using Stable Isotope Tracers

Microbial degradation of monochlorobenzene (MCB) under anaerobic conditions was investigated using a stable isotope tracer under in and ex situ conditions. In situ microcosms were incubated directly in an anoxic aquifer and carbon derived from [13C6]-MCB was found to be incorporated into the microbial biomass. In laboratory microcosms, amended with [13C6]-MCB, anaerobic mineralization of MCB was indicated by the production of 13CO2. Further, recovery of the 13C-label in the fatty acids confirmed the assimilation of MCB-derived carbon into microbial biomass. The described approach may be applied to various other organic groundwater contaminants of concern using carbon (13C) as well as other stable isotope tracers, such as nitrogen (15N), allowing direct and sensitive detection of biodegradation.

Comparison of the equilibrium sorption of five organic compounds to HDPE, PP, and PVC geomembranes

This experimental investigation quantified the sorption uptake of five commonly encountered organic groundwater contaminants, methyl tertiary-butyl-ether (MTBE), benzene, trichloroethylene (TCE), 1,2-dichorobenzene (1,2-DCB), and trinitrotoluene (TNT), to geomembranes made from high density polyethylene (HDPE), polypropylene (PP), and polyvinylchloride (PVC). The organic compounds were chosen to span a range of aqueous solubilities and chemical properties. The geomembranes tested in this study exhibited sorption capacities that were of similar magnitude for each of the contaminants tested, with the exception of 1,2-DCB to HDPE, which exhibited strong uptake in comparison to the other solute/sorbent combinations. In general, the PVC geomembrane demonstrated the highest sorption capacities, while the HDPE geomembrane demonstrated the lowest sorption capacities. Measured partitioning coefficients for the contaminant/geomembrane combinations ranged from S gf<1 to 160, but most commonly had values between 10 and 75.

Formation of poorly crystalline iron monosulfides: Surface redox reactions on high purity iron, spectroelectrochemical studies

In the use of iron for reductive dehalogenation of chlorinated solvents in ground water, due to presence of sulfate-reducing bacteria the formation of hydrogen sulfide is expected. To simulate those processes the interface between 99.99% pure iron and 0.1 M NaHCO 3 deoxygenated solution with 3.1 × 10 −5–7.8 × 10 −3 M Na 2S · 9H 2O added was studied. The surface processes were characterised by the in situ normal Raman spectroscopy (NRS) and ex situ techniques; X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy dispersive X-ray (EDX). The open circuit potential (OCP) was monitored during in situ NRS measurements, and potentiodynamic anodic polarization measurements were carried out to reveal electrochemical behaviour of iron electrode. Open circuit potential–time transients indicated that the native oxide is unstable in deaerated bicarbonate solution and undergoes reductive dissolution (i.e. autoreduction) leaving the metallic Fe covered by Fe(OH) 2, adsorbed OH −, and patches of ‘magnetite-like’ oxide. Immediately upon injection of the Na 2S-solution the iron interface undergoes complex redox surface processes and a poorly crystalline FeS film forms. Potentiodynamic anodic polarization measurements indicated a mechanical breakdown of the FeS film. The origin and initiation of this breakdown process is not clear but is probably a result of internal stress developed during film growth. Based on surface studies supported by electrochemical measurements, a conceptual model for the complex redox processes occurring at the iron interface is proposed. This model describes the structural development of a poorly crystalline FeS, which breaks down, allowing further dissolution of the Fe and formation of FeOOH at the interface. Simultaneously and despite the existence of thick layer of FeS the entrance of hydrogen was evident as the typical hydrogen cracks in bulk of the iron material. This work shed the light on the complexity of the iron/sulfide solution interface, this knowledge is important to understand the kinetic of reduction of organic groundwater contaminants.

Compound-specific chlorine isotope ratios of TCE, PCE and DCE isomers by direct injection using CF-IRMS

A method for determining compound-specific Cl isotopic compositions ( δ 37Cl) was developed for tetrachloroethene (PCE), trichloroethene (TCE), cis-dichloroethene ( cis-DCE), trans-dichloroethene ( trans-DCE) and 1,1-dichloroethene (1,1-DCE). The isotope ratio mass spectrometry (IRMS) used in this study has nine collectors, including two for m/z 50 and 52 (CH 3Cl) and two for m/z 94 and 96 (CH 3Br). The development of this method is based on the fact that fragments with mass ratios of 94/96, 95/97 and 96/98 are produced from PCE, TCE and DCE isomers during ion bombardment in the source of a mass spectrometer. Using continuous flow isotope ratio mass spectrometry coupled with gas chromatography (GC–CF-IRMS), it is possible to separate these compounds on-line and directly measure the Cl isotopic ratios of the fragments with the specific mass ratios. Both pure phase and aqueous samples were used for Cl isotopic analysis. For pure phase samples, a vapour phase of the chlorinated ethenes was injected directly into the GC, whereas the solid phase micro extraction (SPME) method was used to extract these compounds from aqueous solutions. The precisions of this analytical technique were ±0.12‰ (1 σ, n = 30), ±0.06‰ (1 σ, n = 30), and ±0.08‰ (1 σ, n = 15) for PCE, TCE and DCE isomers, respectively. The limits of quantification (LOQ) for analyzing Cl isotopic composition in aqueous solutions were 20, 5, and 5 μg/L for PCE, TCE and DCE isomers, respectively. This corresponds to 6–9 nano-mole of Cl, which is approximately 80 times lower than the most sensitive existing method. Compared to methods previously available, this new development offers the following advantages: (1) The much lower LOQ make it possible to extract these compounds directly from aqueous solutions using SPME without pre-concentration; (2) The linking of a GC with an IRMS eliminates off-line separation; and (3) Because the fragments used for isotopic ratio measurement are produced during ion bombardment in the mass spectrometer, there is no need to convert chlorinated ethenes to methyl chloride. As a result, this technique greatly enhances the efficiency for isotopic analysis by eliminating procedures for pre-concentration, off-line separation and sample preparation. In addition, it also reduces the potential for isotopic fractionation introduced during these procedures. Compound-specific Cl stable isotope analysis can be used as a tool to study the sources of organic contaminants in groundwater and their behaviour in the subsurface environments. It may also assist in understanding processes such as transport, mixing, and degradation reactions.

Does the Rayleigh Equation Apply to Evaluate Field Isotope Data in Contaminant Hydrogeology?

Stable isotope data have been increasingly used to assess in situ biodegradation of organic contaminants in groundwater. The data are usually evaluated using the Rayleigh equation to evaluate whether isotope data follow a Rayleigh trend, to calculate the extent of contaminant biodegradation, or to estimate first-order rate constants. However, the Rayleigh equation was developed for homogeneous systems while in the subsurface, contaminants can migrate at different velocities due to physical heterogeneity. This paper presents a method to quantify the systematic effect that is introduced by applying the Rayleigh equation to field isotope data. For this purpose, the travel time distribution between source and sampling point is characterized by an analytical solution to the advection-dispersion equation. The systematic effect was evaluated as a function of the magnitude of physical heterogeneity, geometry of the contaminant plume, and degree of biodegradation. Results revealed that the systematic effect always leads to an underestimation of the actual values of isotope enrichment factors, the extent of biodegradation, or first-order rate constants, especially in the dispersion-dominant region representing a higher degree of physical heterogeneity. A substantial systematic effect occurs especially for the quantification of first-order rate constants (up to 50% underestimation of actual rate) while it is relatively small for quantification of the extent of biodegradation (< 5% underestimation of actual degree of biodegradation). The magnitude of the systematic effect is in the same range as the uncertainty due to uncertainty of the analytical data, of the isotope enrichment factor, and the average travel time.

Natural attenuation and enhanced bioremediation of organic contaminants in groundwater

An area of intense scientific and practical interest is the biogeochemical and microbial processes determining the success of natural attenuation, biostimulation and/or bioaugmentation treatments for organic contaminants in groundwater. Recent studies in this area have focused on the reductive dechlorination of chlorinated solvents, the degradation of the fuel additive methyl tert-butyl ether, and the removal of long-term hydrocarbon contamination. These studies have been facilitated by the use of stable isotope analysis to demonstrate in situ bioremediation and push-pull tests, in which isotopes are injected into aquifers and then quickly retrieved and analyzed, to measure in situ activity. Molecular tools such as quantitative PCR, the detection of mRNA expression, and numerous DNA fingerprinting methods have also proved valuable, being employed to identify and sometimes quantify environmentally important organisms or changes in communities. Methods to track bacteria and tools to characterize bacterial attachment properties have also offered insight into bacterial transport in situ.

Performance of semipermeable membrane devices for sampling of organic contaminants in groundwater

Lipid-filled semipermeable membrane devices (SPMDs) are receiving increasing attention as passive, in situ samplers for the assessment of environmental pollutant exposure. Although SPMDs have been successfully used in a variety of field studies in surface waters, only a few studies have addressed their characteristics as groundwater samplers. In this study, the performance of the SPMDs for monitoring organic contaminants in groundwater was evaluated in a pilot field application in an area severely contaminated by chemical waste, especially by chlorinated hydrocarbons. The spatial distribution of hydrophobic groundwater contaminants was assessed using a combination of passive sampling with SPMDs and non-target semiquantitative GC-MS analysis. More than 100 contaminants were identified and semiquantitatively determined in SPMD samples. Along the 6 field sites under investigation, a large concentration gradient was observed, which confirms a very limited mobility of hydrophobic substances in dissolved form in the aquifer. The in situ extraction potential of the SPMD is limited by groundwater flow, when the exchange volume of well water during an exposure is lower than the SPMD clearance volume for the analytes. This study demonstrates that SPMDs present a useful tool for sampling and analyzing of groundwater polluted with complex mixtures of hydrophobic chemicals and provides guidance for further development of passive sampling technology for groundwater.

Enrichment of Stable Carbon and Hydrogen Isotopes during Anaerobic Biodegradation of MTBE: Microcosm and Field Evidence

The conventional approach to evaluate biodegradation of organic contaminants in groundwater is to demonstrate an increase in the concentration of transformation products. This approach is problematic for MTBE from gasoline spills because the primary transformation product (TBA) can also be a component of gasoline. Compound-specific stable isotope analysis may provide a useful alternative to conventional practice. Changes in the delta13C and deltaD of MTBE during biodegradation of MTBE in an anaerobic enrichment culture were compared to the delta13C and deltaD of MTBE in groundwater at nine gasoline spill-sites. The stable isotopes of hydrogen and carbon were extensively fractionated during anaerobic biodegradation of MTBE. The stable isotope enrichment factor for carbon (epsilonC) in the enrichment cultures was -13 (-14.1 to -11.9 at 95% confidence level), and the hydrogen enrichment factor (epsilonH) was -16 (-21 to -11 at 95% confidence level). The isotope enrichment factors for carbon and hydrogen during anaerobic biodegradation indicate that the first reaction is enzymatic hydrolysis of the O-Cmethyl bond. The ratio of epsilonH to epsilonC was consistent between the enrichment culture and the field site that provided the inoculum, and with the other eight sites, suggesting a common degradation pathway. Compound-specific isotope evidence is discussed in terms of its utility for monitoring in situ biodegradation, in particular, for measuring how much MTBE was degraded. For the studied field sites, significant biodegradation of the original mass of MTBE is suggested, in some cases exceeding 90%.

New Device and Method for Flux-Proportional Sampling of Mobile Solutes in Soil and Groundwater

The importance of monitoring the transport of organic contaminants in soil and groundwater, and the pros and cons of existing sampling methods, are outlined. A new, alternative sampling method is proposed, using a passive sampler that functions as a water-permeable, semi-infinite sink for passing solutes of interest. Tracers integrated in the device store information on the volume of water passing through the sampler during the installation period. The conceptual basis of the sampling method is described. This device enables flux-proportional monitoring of the concentrations of mobile contaminants in the soil and groundwater. 14C-labeled phenanthrene (PHEN) and glyphosate (GLY) are used as case study compounds in laboratory experiments. The sorption capacities and uptake kinetics of 13 adsorbents are screened and compared, as well as the dissolution kinetics of three tracer salts: calcium citrate, calcium fluoride (CaF2), and calcium hydrogen phosphate (CaHPO4). The application of the passive sampler is then demonstrated in long-term laboratory experiments, using large soil columns under steady-state hydraulic conditions. The accumulated flux of PHEN was sampled with an accuracy of 3.6%-17.8%, using graphitized carbon, hexagonal mesoporous silica, and cross-linked polymers as adsorbents. The accumulated flux of GLY was sampled with an accuracy of 12.4%, using gamma-alumina as an adsorbent. The advantages and limitations of this new environmental monitoring method are discussed.

Distribution of oxides on iron materials used for remediation of organic groundwater contaminants — Implications for hydrogen evolution reactions

The distribution of oxides on commercial iron materials used for remediation of organic groundwater contaminants was studied using confocal Raman microspectroscopy. Raman microprobe mapping experiments revealed that commercial iron materials used for the construction of permeable reactive barriers are covered with an oxide film consisting of an inner film of magnetite Fe3O4 and an outer film of Fe2O3. The calculated probability of the charge transfer process (i.e., electron tunnelling probability) at commercial Fe | Fe2O3 (semiconductor) | solution interfaces approaches zero, indicating that "as received" commercial iron materials should not be reactive towards both organic contaminants and water. The combination of OCP (corrosion potential) – time measurements with in situ Raman spectroscopy demonstrated that the breakdown of the protective Fe2O3 oxide film followed by autoreduction of Fe2O3 is a requirement for the commercial materials to be chemically active towards both water and organic contaminants. Hydrogen evolution reactions on metals and oxide-covered iron were also investigated. In particular, spectroscopic evidence for adsorption of atomic hydrogen on polycrystalline Pt is presented. The possibility of adsorption of H on magnetite-covered iron was considered using thermodynamic calculations after Marcus and Protopopoff. The evolution of hydrogen on commercial iron materials is described. It is suggested that the separation of the anodic and cathodic sites because of opening of pores in the bulk metallic Fe and the involvement of spill-over hydrogen may play a crucial role in the catalytic hydrogenation of groundwater contaminants.Key words: Raman microprobe confocal spectroscopy, iron oxides, hydrogen evolution, remediation of organic groundwater contaminants.