Showing papers by "Stefan B. Haderlein published in 2011"

Compound-specific chlorine isotope analysis: a comparison of gas chromatography/isotope ratio mass spectrometry and gas chromatography/quadrupole mass spectrometry methods in an interlaboratory study.

Abstract: Chlorine isotope analysis of chlorinated hydrocarbons like trichloroethylene (TCE) is of emerging demand because these species are important environmental pollutants. Continuous flow analysis of noncombusted TCE molecules, either by gas chromatography/isotope ratio mass spectrometry (GC/IRMS) or by GC/quadrupole mass spectrometry (GC/qMS), was recently brought forward as innovative analytical solution. Despite early implementations, a benchmark for routine applications has been missing. This study systematically compared the performance of GC/qMS versus GC/IRMS in six laboratories involving eight different instruments (GC/IRMS, Isoprime and Thermo MAT-253; GC/qMS, Agilent 5973N, two Agilent 5975C, two Thermo DSQII, and one Thermo DSQI). Calibrations of (37)Cl/(35)Cl instrument data against the international SMOC scale (Standard Mean Ocean Chloride) deviated between instruments and over time. Therefore, at least two calibration standards are required to obtain true differences between samples. Amount dependency of δ(37)Cl was pronounced for some instruments, but could be eliminated by corrections, or by adjusting amplitudes of standards and samples. Precision decreased in the order GC/IRMS (1σ ≈ 0.1‰), to GC/qMS (1σ ≈ 0.2-0.5‰ for Agilent GC/qMS and 1σ ≈ 0.2-0.9‰ for Thermo GC/qMS). Nonetheless, δ(37)Cl values between laboratories showed good agreement when the same external standards were used. These results lend confidence to the methods and may serve as a benchmark for future applications.

Chlorine isotope analysis of organic contaminants using GC-qMS: method optimization and comparison of different evaluation schemes.

Abstract: Compound-specific online chlorine isotope analysis of chlorinated hydrocarbons was evaluated and validated using gas chromatography coupled to a regular quadrupole mass spectrometer (GC–qMS). This technique avoids tedious off-line sample pretreatments, but requires mathematical data analysis to derive chlorine isotope ratios from mass spectra. We compared existing evaluation schemes to calculate chlorine isotope ratios with those that we modified or newly proposed. We also tested systematically important experimental procedures such as external vs. internal referencing schemes, and instrumental settings including split ratio, ionization energy, and dwell times. To this end, headspace samples of tetrachloroethene (PCE), trichloroethene (TCE), and cis-dichloroethene (cDCE) at aqueous concentrations in the range of 20–500 μg/L (amount on-column range: 3.2–115 pmol) were analyzed using GC–qMS. The results (37Cl/35Cl ratios) showed satisfying to good precisions with relative standard deviations (n = 5) between...

Aquatic redox chemistry

Abstract: Preface 1. Introduction to Aquatic Redox Chemistry Timothy J. Grundl, Stefan Haderlein, James T. Nurmi, and Paul G. Tratnyek 2. Thermodynamic Redox Calculations for One and Two Electron Transfer Steps: Implications for Halide Oxidation and Halogen Environmental Cycling George W. Luther, III 3. One-Electron Reduction Potentials from Chemical Structure Theory Calculations Eric J. Bylaska, Alexandra J. Salter-Blanc, and Paul G. Tratnyek 4. Thermodynamic Control on Terminal Electron Transfer and Methanogenesis Christian Blodau 5. Redox Chemistry and Natural Organic Matter (NOM): Geochemists' Dream, Analytical Chemists' Nightmare Donald L. Macalady and Katherine Walton-Day 6. Electron Shuttling by Natural Organic Matter: Twenty Years After Garrison Sposito 7. Electrochemistry of Natural Organic Matter James T. Nurmi and Paul G. Tratnyek 8. Pathways Contributing to the Formation and Decay of Ferrous Iron in Sunlit Natural Waters Shikha Garg, Andrew L. Rose, and T. David Waite 9. The Role of Iron Coordination in the Production of Reactive Oxidants from Ferrous Iron Oxidation by Oxygen and Hydrogen Peroxide Christina Keenan Remucal and David L. Sedlak 10. TiO2 Photocatalysis for the Redox Conversion of Aquatic Pollutants Jaesang Lee, Jungwon Kim, and Wonyong Choi 11. Chlorine Based Oxidants for Water Purification and Disinfection Gregory V. Korshin 12. Remediation of Chemically-Contaminated Waters Using Sulfate Radical Reactions: Kinetic Studies Stephen P. Mezyk, Kimberly A. Rickman, Garrett McKay, Charlotte M. Hirsch, Xuexiang He, and Dionysios D. Dionysiou 13. Voltammetry of Sulfide Nanoparticles and the FeS(aq) Problem G. R. Helz, I. Ciglenecki, D. Krznaric, and E. Bura-Nakic 14. Redox Reactivity of Organically Complexed Iron(II) Species with Aquatic Contaminants Timothy J. Strathmann 15. Fe2+ Sorption at the Fe Oxide-Water Interface: A Revised Conceptual Framework Christopher A. Gorski and Michelle M. Scherer 16. Redox Driven Stable Isotope Fractionation Jay R. Black, Jeffrey A. Crawford, Seth John, and Abby Kavner 17. Redox Properties of Structural Fe in Smectite Clay Minerals Anke Neumann, Michael Sander, and Thomas B. Hofstetter 18. Reactivity of Zerovalent Metals in Aquatic Media: Effects of Organic Surface Coatings Paul G. Tratnyek, Alexandra J. Salter-Blanc, James T. Nurmi, James E. Amonette, Juan Liu, Chongmin Wang, Alice Dohnalkova, and Donald R. Baer 19. Current Perspectives on the Mechanisms of Chlorohydrocarbon Degradation in Subsurface Environments: Insight from Kinetics, Product Formation, Probe Molecules, and Isotope Fractionation Martin Elsner and Thomas B. Hofstetter 20. Degradation Routes of RDX in Various Redox Systems Annamaria Halasz and Jalal Hawari 21. Role of Coupled Redox Transformations in the Mobilization and Sequestration of Arsenic Janet G. Hering, Stephan J. Hug, Claire Farnsworth, and Peggy A. O'Day 22. Redox Processes Affecting the Speciation of Technetium, Uranium, Neptunium, and Plutonium in Aquatic and Terrestrial Environments Edward J. O'Loughlin, Maxim I. Boyanov, Dionysios A. Antonopoulos, and Kenneth M. Kemner 23. Rate Controlling Processes in the Transformation of Tetrachloroethylene and Carbon Tetrachloride under Iron Reducing and Sulfate Reducing Conditions Elizabeth C. Butler, Yiran Dong, Lee R. Krumholz, Xiaoming Liang, Hongbo Shao, and Yao Tan 24. The Use of Chemical Probes for the Characterization of the Predominant Abiotic Reductants in Anaerobic Sediments Huichun (Judy) Zhang, Dalizza Colon, John F. Kenneke, and Eric J. Weber 25. The Role of Transport in Aquatic Redox Chemistry Wolfgang Kurtz and Stefan Peiffer 26. Evolution of Redox Processes in Groundwater Peter B. McMahon, Francis H. Chapelle, and Paul M. Bradley Editors' Biographies Indexes Author Index Subject Index

Effects of Zwitterionic Buffers on Sorption of Ferrous Iron at Goethite and Its Oxidation by CCl4

Abstract: A major factor which controls sorption and oxidation of Fe(II) at the mineral-water interface is pH, hence buffers are commonly used to control pH in experimental studies. Here, we examined the effects of widely used organic buffers (3-morpholinopropane-1-sulfonic acid (MOPS) and 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES)) on Fe(II) uptake and oxidation by CCl4 in aqueous suspensions of goethite. Significant sorption of these zwitterionic buffers occurred only at Fe(II)-loaded goethite but not at native goethite. The addition of MOPS and HEPES caused substantial release of Fe(II) from goethite, retarded the oxidation of surface-bound Fe(II) by CCl4 and changed the reaction pathway as indicated by lower yields of CHCl3. To explore electrostatic and steric contributions of MOPS and HEPES to the observed phenomena we studied sorption and competitive effects of model sorbates (Ca2+, sulfonates) which suggest the formation of a complex between surface-bound Fe(II) and MOPS or HEPES. Our study s...

Groundwater pollution potential of additives used in borehole heat exchanger fluids

Abstract: Ground-based heat exchanger systems need to be evaluated in terms of potential effects on groundwater quality due to the risk of leakage of borehole heat exchanger fluids. They contain glycols or inorganic brines as major components, but typically also various additives. As the identity of these additives is proprietary information, the major objective of this study was to obtain an overview of the identities and properties of individual additive compounds used in borehole heat exchanger fluids. Leading companies in the production and distribution of these fluids were invited to participate in a confidential data survey. A wide variety of additive compounds were assembled, which can be grouped into ten chemical classes: triazoles, carboxylic acids/carbonates, phosphonates, alcohols, aldehydes, ethers borates, silicates, nitrates and hydroxides. Among these substances some are also used in other applications, e.g. aircraft de-icing fluids and engine antifreeze formulations, and are of potential concern for groundwater quality. Based on their abundance in the investigated borehole heat exchangers and their concerning environmental behaviour in the subsurface, benzotriazoles, tolyltriazoles and some carbonates were selected for further biodegradation experiments.

Groundwater pollution potential of additives used in borehole heat exchanger fluids

Abstract: Ground-based heat exchanger systems need to be evaluated in terms of potential effects on groundwater quality due to the risk of leakage of borehole heat exchanger fluids. They contain glycols or inorganic brines as major components, but typically also various additives. As the identity of these additives is proprietary information, the major objective of this study was to obtain an overview of the identities and properties of individual additive compounds used in borehole heat exchanger fluids. Leading companies in the production and distribution of these fluids were invited to participate in a confidential data survey. A wide variety of additive compounds were assembled, which can be grouped into ten chemical classes: triazoles, carboxylic acids/carbonates, phosphonates, alcohols, aldehydes, ethers borates, silicates, nitrates and hydroxides. Among these substances some are also used in other applications, e.g. aircraft de-icing fluids and engine antifreeze formulations, and are of potential concern for groundwater quality. Based on their abundance in the investigated borehole heat exchangers and their concerning environmental behaviour in the subsurface, benzotriazoles, tolyltriazoles and some carbonates were selected for further biodegradation experiments.

Assessment of chlorinated ethenes biodegradation in an anaerobic aquifer by isotope analysis and microcosm studies

Abstract: This work focused on identification and quantification of natural attenuation of chlorinated ethenes in a contaminated aquifer beneath an industrial area using compound specific isotope analysis (CSIA). Presence of cis-1,2-dichloroethene (cis-DCE) and vinylchloride (VC), as well as in situ redox conditions indicated degradation of the primary contaminant trichloroethene (TCE) by reductive dechlorination. The potential for VC degradation was further corroborated by PCR-analysis on water samples which confirmed the presence of Dehalococcoides strains and VC reductases. In situ biodegradation was estimated by various approaches, including concentration measurements along the groundwater flow path, microcosm studies and by compound specific stable carbon isotope analysis. Using the Rayleigh model carbon isotope enrichment factors, e, were determined both in the field and in microcosm experiments for each dechlorination step. Estimates of biodegradation based on enrichment factors derived from microcosms (―8.6‰ (cis-DCE) and ―27.2‰ (VC)) were consistently lower (up to 40%) than those based on field data. Our results of the isotope study at field scale, microcosm experiments and molecular marker analysis provided conclusive information on natural attenuation processes and can be recommended as a general approach for site characterisation and risk assessment in NA studies.

Enhanced natural attenuation - Determining the potential for reductive dechlorination in an oxic aquifer

Abstract: The aim of the study was to demonstrate the stimulation of reductive dehalogenation of chlorinated ethenes in an oxic aquifer. Microcosms with aquifer material were amended with different organic substrates as electron donors in order to stimulate microbial reductive dechlorination. Next to molasses and lactate a commercial product was applied, which has been described as controlled-release carbon zero valent iron particles (EHC™). In addition, vitamins and bicarbonate buffer were added to the microcosms to further stimulate growth of halorespiring microorganisms. Reductive dechlorination was followed by measuring chlorinated ethene concentrations and their stable carbon isotope fractionation. The microbiological community was monitored by terminal restriction fragment length polymorphism (T-RFLP). The EHC amended microcosms showed only incomplete conversion of PCE, resulting in an accumulation of cis-DCE after incubation for 103 days. In the microcosms amended with molasses, complete reductive dechlorination of PCE to ethene was observed within 56 days. The degradation of the less chlorinated ethenes correlated with the appearance of Dehalococcoides microorganisms and carbon isotope fractionation. Also one of the parallel set-ups amended with lactate showed complete dechlorination. In this microcosm an isotopic overtaking of VC was observed, proving complete microbiological degradation to ethene. Control microcosms without substrate addition showed no dechlorination during the whole experiment. Our study demonstrates that the potential for microbial reductive dechlorination was present and can be stimulated in an oxic aquifer by establishing reducing conditions and supplementing fermentable substrates.