Papers by Stefan B Haderlein
Research Square (Research Square), Mar 11, 2024
Determination of glyphosate and AMPA in surface and waste water using high-performance ion chroma... more Determination of glyphosate and AMPA in surface and waste water using high-performance ion chromatography coupled to inductively coupled plasma dynamic reaction cell mass spectrometry (HPIC-ICP-DRC-MS).
Social Science Research Network, 2022
Environmental Science & Technology, Nov 23, 2013
Redox reactions at iron mineral surfaces play an important role in controlling biogeochemical pro... more Redox reactions at iron mineral surfaces play an important role in controlling biogeochemical processes of natural porous media such as sediments, soils and aquifers, especially in the presence of recurrent variations in redox conditions. Ferrous iron associated with iron mineral phases forms highly reactive species and is regarded as a key factor in determining pathways, rates, and extent of chemically and microbially driven electron transfer processes across the iron mineral-water interface. Due to their transient nature and heterogeneity a detailed characterization of such surface bound Fe(II) species in terms of redox potential is still missing. To this end, we used the nonsorbing anthraquinone-2,6-disulfonate (AQDS) as a redox probe and studied the thermodynamics of its redox reactions in heterogeneous iron systems, namely goethite-Fe(II). Our results provide a thermodynamic basis for and are consistent with earlier observations on the ability of AQDS to "shuttle" electrons between microbes and iron oxide minerals. On the basis of equilibrium AQDS speciation we reported for the first time robust reduction potential measurements of reactive iron species present at goethite in aqueous systems (EH,Fe-GT ≈ -170 mV). Due to the high redox buffer intensity of heterogeneous mixed valent iron systems, this value might be characteristic for many iron-reducing environments in the subsurface at circumneutral pH. Our results corroborate the picture of a dynamic remodelling of Fe(II)/Fe(III) surface sites at goethite in response to oxidation/reduction events. As quinones play an essential role in the electron transport systems of microbes, the proposed method can be considered as a biomimetic approach to determine "effective" biogeochemical reduction potentials in heterogeneous iron systems.
American Chemical Society eBooks, Nov 6, 2001
ABSTRACT
EGU General Assembly Conference Abstracts, Apr 1, 2019
Journal of Contaminant Hydrology, Jun 1, 2009
The transport of organic contaminants in porous media is frequently influenced by nonequilibrium ... more The transport of organic contaminants in porous media is frequently influenced by nonequilibrium sorption and/or nonlinear sorption. In this study, sorption of coal tar related contaminants with different sorption properties, i.e., toluene, quinoline, quinaldine, and benzotriazole, was studied in column experiments using a European reference soil and compared with batch sorption results in order to quantify the governing sorption features. The breakthrough curves (BTCs) were simulated with a versatile 1-D reactive transport model using a one-site first-order sorption approach. Some differences in fitted parameters from batch and column experiments were found and discussed in terms of different sorption mechanisms in different aqueous concentration ranges, effects of solution properties (e.g., pH) and differences in solid-to-solution ratio and accessible sorption sites. The modeling results show that the fitting results were not sensitive to mass transfer coefficients and that a local equilibrium assumption provides excellent agreement with BTCs in our designed column when Damkohler numbers were greater than 20. Nonequilibrium sorption resulting from intraparticle diffusion thus was negligible in the column experiments. Tailing of BTCs nevertheless occurred and was primarily attributed to nonlinear sorption due to specific interactions in the sorption processes rather than to sorption nonequilibrium. Our study demonstrates how column experiments with different concentrations and flow velocities can be designed to obtain reliable sorption parameters for polar solutes with nonlinear sorption isotherms from modeling.
Environmental Science & Technology, Sep 6, 2006
Sorption is an important natural and technical process. Sorption coefficients are typically deter... more Sorption is an important natural and technical process. Sorption coefficients are typically determined in batch experiments but this may be challenging for weakly sorbing compounds. An alternative method enabling analysis of those compounds is column chromatography. A column packed with the sorbent is used and sorption data are determined by relating sorbate retention to that of a non-retarded tracer. In this study, column chromatography was applied for the first time to study sorption of previously hardly investigated heterocyclic organic compounds to multi-walled carbon nanotubes (MWCNTs). Sorption data for these compounds are very limited in literature and weak sorption is expected from predictions. Deuterium oxide was used as non-retarded tracer. Sorption isotherms were well described by the Freundlich model and data showed reasonable agreement with predicted values. Sorption was exothermic and physisorption was observed. H-bonding may contribute to overall sorption, which is supported by reduced sorption with increasing ionic strength due to blocking of functional groups. Lowering pH reduced sorption of ionizable compounds, due to electrostatic repulsion at pH 3 where sorbent as well as sorbates were positively charged. Overall, column chromatography was successfully used to study sorption of heterocyclic compounds to MWCNTs and could be applied for other carbon-based sorbents.
Natural Organic Matter (NOM) shows both oxidizing and reducing capabilities through its quinone/h... more Natural Organic Matter (NOM) shows both oxidizing and reducing capabilities through its quinone/hydroquinone functional groups and takes part in various geochemically redox reactions. Here four natural and synthetic quinone model compounds (anthraquinone-2,6-disulfonate, AQDS; anthraquinone-2-sulfonate, AQS; 2-hydroxyl-1,4-naphthoquinone, Lawsone; and anthraquinone-2,3-dicarboxylic acid, AQDC) were used to study the effect of adsorption of redox active organic matter on mediating ferrihydrite reduction. The studied quinone compounds varied regarding reduction potential and their tendency to adsorb at ferrihydrite. An electrochemical setup rather than iron reducing bacteria was used to circumvent potential inhibitory effects of the model quinones on microbial activity. Iron speciation, dissolved and adsorbed quinone concentrations and their redox state were monitored to elucidate controlling factors in mediated ferrihydrite reduction. Results show that all model quinones present at 100 µM total concentration enhanced the initial iron reduction rate of ferrihydrite, however, to very different extents. At -0.45 V (vs. Ag/AgCl) redox potential applied, the initial reduction rates increased compared to quinone free systems by factors of 62.53, 43.11, 32.26 and 2.91 for AQDS, AQS, Lawsone and AQDC, respectively. In contrast to AQDC and Lawsone, AQDS and AQS did not show significant adsorption at ferrihydrite under the conditions of our study. Due to the high sorption, the initial dissolved AQDC concentration was only 3.60 μM. The initial dissolved concentration of Lawsone was 85.70 µM and decreased further during ferrihydrite reduction. Adsorbed Fe(II) promoted the adsorption of Lawsone on ferrihydrite thereby decreasing the rate of iron reduction. Our findings demonstrate that the rate of ferrihydrite reduction correlated with dissolved quinone concentrations. As a result, AQDS and AQS showed the highest acceleration of ferrihydrite reduction. At the redox conditions applied (-0.45 V vs. Ag/AgCl) the fraction of reduced quinone species was higher for AQDS than for AQS, consistent with the higher efficiency of AQDS in mediating ferrihydrite reduction.The possibility of conducting experiments at defined redox potentials and precisely controllable experimental conditions reveals the perspectives of an electrochemical setup for the investigation of biogeochemical redox reactions.
Geochimica et Cosmochimica Acta, Sep 4, 2009
EGU General Assembly Conference Abstracts, Apr 1, 2017
Soil gas measurements on a sanitary landfill site were carried out with a mobile sampling pipe de... more Soil gas measurements on a sanitary landfill site were carried out with a mobile sampling pipe device. After having adsorbed the halogenated organic gas constituents in the field, quantification and identification of the extracted compounds was done by GC-ECD and GC-MS in the laboratory. Several contaminated areas of the landfill site were localized by means of grid point sampling, using volatile halo-carbons as tracers for industrial wastes. Shredder wastes from metal utilizing plants were found to be highly contaminated with chlorofluorocarbons (CFCs). The outgasing dynamics of CFCs from shredder wastes were estimated by several one dimensional diffusion models. A comparison of measured vertical soil gas concentration profiles with model calculations showed good agreement, using a model with two diffusion interphases — one into the atmosphere and one into the subsoil. Since the half life for CCl2F2 due to diffusion into the atmosphere lasts only two days, covering of the shredder wastes with compacted adsorbing layers immediately after their deposition is recommended.
Environmental Science: Processes & Impacts, 2022
We present field data on the effects of heavy rainfall after drought on the mobility of glyphosat... more We present field data on the effects of heavy rainfall after drought on the mobility of glyphosate and redox conditions in a clayey floodplain soil.
Analytical and Bioanalytical Chemistry, Jun 10, 2020
In this study, we developed and validated a CE-TOF-MS method for the quantification of glyphosate... more In this study, we developed and validated a CE-TOF-MS method for the quantification of glyphosate (N-(phosphonomethyl)glycine) and its major degradation product aminomethylphosphonic acid (AMPA) in different samples including beer, media from toxicological analysis with Daphnia magna, and sorption experiments. Using a background electrolyte (BGE) of very low pH, where glyphosate is still negatively charged but many matrix components become neutral or protonated, a very high separation selectivity was reached. The presence of inorganic salts in the sample was advantageous with regard to preconcentration via transient isotachophoresis. The advantages of our new method are the following: no derivatization is needed, high separation selectivity and thus matrix tolerance, speed of analysis, limits of detection suitable for many applications in food and environmental science, negligible disturbance by metal chelation. LODs for glyphosate were < 5 μg/L for both aqueous and beer samples, the linear range in aqueous samples was 5-3000 μg/L, for beer samples 10-3000 μg/L. For AMPA, LODs were 3.3 and 30.6 μg/L, and the linear range 10-3000 μg/L and 50-3000 μg/L, for aqueous and beer samples, respectively. Recoveries in beer samples for glyphosate were 94.3-110.7% and for AMPA 80.2-100.4%. We analyzed 12 German and 2 Danish beer samples. Quantification of glyphosate and AMPA was possible using isotopically labeled standards without enrichment, purification, or dilution, only degassing and filtration were required for sample preparation. Finally, we demonstrate the applicability of the method for other strong acids, relevant in food and environmental sciences such as N-acetyl glyphosate, Nacetyl AMPA (present in some glyphosate resistant crop), trifluoroacetic acid, 2-methyl-4-chlorophenoxyacetic acid, glufosinate and its degradation product 3-(methylphosphinico)propionic acid, oxamic acid, and others.
Environmental Science & Technology, Dec 18, 2002
Mineral-bound Fe(II) species represent important natural reductants of pollutants in the anaerobi... more Mineral-bound Fe(II) species represent important natural reductants of pollutants in the anaerobic subsurface. At clay minerals, three types of Fe(II) species in fundamentally different chemical environments may be present simultaneously, i.e., structural Fe(II), Fe(II) complexed by surface hydroxyl groups, and Fe(II) bound by ion exchange. We investigated the accessibility and reactivity of these three types of Fe(II) species in suspensions of two different clay minerals containing either ferrous iron-bearing nontronite or iron-free hectorite. Nitroaromatic compounds (NACs) exhibiting different sorption behavior on clays were used to probe the reactivity of the various types of reduced iron species. The clay treatment allowed for a preparation of nontronite and hectorite surfaces with Fe(II) adsorbed by surface hydroxyl groups at the edge surfaces. Furthermore, hectorite suspensions with additional Fe(II) bound to the ion exchange sites at the basal siloxane surfaces were set up. We found that both structural Fe(II) and Fe(II) complexed by surface hydroxyl groups of nontronite reduced the NACs to anilines. An electron balance revealed that more than 10% of the total iron in nontronite was reactive Fe(II). Fe(II) bound by ion exchange did not contribute to the observed reduction of NACs. Reversible adsorption of the NACs at the basal siloxane surface of the clays strongly retarded NAC reduction, even in the presence of high concentrations of Fe(II) bound by ion exchange to the basal siloxane surfaces. Our work shows that in natural systems a fraction of the total Fe(II) present on clays may contribute to the pool of highly reactive Fe(II) species in the subsurface. Furthermore, this work may help to distinguish between Fe(II) species of different reactivity regarding pollutant reduction. Although structural iron in clays represents only a small fraction of the total iron pool in soils and aquifers, reactive Fe(II) species originating from the reduction of structural Fe(III) in clays may contribute significantly to the biogeochemical cycling of electrons in the subsurface since it is not subject to depletion by reductive dissolution.
Springer eBooks, 1995
Numerous synthetic chemicals contain one or several nitro groups that are bound to an aromatic ri... more Numerous synthetic chemicals contain one or several nitro groups that are bound to an aromatic ring. Figure 1 shows the structures of some prominent representatives of such nitroaromatic compounds (NACs). The high toxicity of some NACs, particularly the mutagenic and carcinogenic potential of some nitrated polycyclic aromatic hydrocarbons (PAHs), has led to considerable interest in the fate of such compounds in the environment. Due to their widespread use, NACs are ubiquitous contaminants, especially in aqueous environments. In addition to contamination originating from agricultural use, from production facilities, and waste disposal sites, diffuse input into the pedosphere via the atmosphere has been documented (21, 27, 36, 37, 59, 65, 69, 80, 81). Atmospheric production of significant quantities of NACs by photochemical processes has been reported (19, 29, 42, 80). Table 1 lists some typical concentrations of NACs that have been measured in various compartments of the environment. Very high concentrations of nitroaromatic explosives (2,4,6-trinitrotoluene (TNT) and by-products) have been found especially in soil and subsurface systems. At those sites, significant concentrations of substituted aromatic amines that may have been formed from the reduction of NACs are frequently encountered.
Environmental Science & Technology, May 25, 2011
b S Supporting Information ' INTRODUCTION Chlorinated organic compounds such as PCE, TCE, and the... more b S Supporting Information ' INTRODUCTION Chlorinated organic compounds such as PCE, TCE, and their transformation products are notorious groundwater pollutants. 1 They occur in dissolved state and as nonaqueous-phase liquids (NAPLs), which act as long-term sources for contaminant plumes in the subsurface. 1,2 Compound-specific isotope analysis (CSIA) has been successfully used in a variety of studies to quantify the fate of chlorinated organic pollutants, as well as to identify contaminant sources in groundwater. 2À6 Recently, there has been increasing interest for dual element isotope analysis 7À12 as it improves the robustness and range of applications of CSIA approaches considerably. Chlorine CSIA provides a valuable tool to detect and quantify biodegradation processes and abiotic transformation of the chlorinated organic compounds in the subsurface. However, unlike the well-established and widely implemented stable carbon isotope analysis, 2,3 traditional analytical techniques used for stable chlorine isotopes require tedious off-line sample treatment and dedicated instrumentation. After chromatographic separation the chlorinated analytes have to be converted quantitatively into compounds containing only one chlorine atom (e.g., CsCl, CH 3 Cl). These pure compounds are then analyzed for their isotopic ratio using either a thermal ionization mass spectrometer (TIMS for solid CsCl) or a dual-inlet gas isotope ratio mass spectrometer (DI-IRMS for gaseous CH 3 Cl). 13À17 Using a gas chromatograph (GC) coupled to a continuous flow isotope ratio mass spectrometer (CF-IRMS) Shouakar-Stash et al. 14 established the first online method for chlorine CSIA and reported a concept for deriving chlorine isotope ratios for PCE, TCE, and cis-DCE. Sakaguchi-Soeder et al. 18 introduced an alternative instrumental approach for online compound-specific chlorine isotope analysis using widely available gas chromatographyÀquadrupole mass spectrometry (GCÀqMS). They determined chlorine isotope ratios for PCE and TCE, and referenced their data to an internal standard trichlorofluoromethane (CFCl 3). Very recently, Aeppli et al. 20 determined chlorine isotope compositions of PCE, PCP, and DDT with GCÀqMS using on-column liquid injection and bracketing with external standards of known chlorine isotope composition. In contrast to carbon, hydrogen, nitrogen, and oxygen, the two stable isotopes of chlorine are two-mass units apart and both occur at relatively similar abundances (35 Cl at 75.78% and 37 Cl at
Environmental Science & Technology, Mar 13, 2002
Uptake of ferrous iron from aqueous solution by iron oxides results in the formation of a variety... more Uptake of ferrous iron from aqueous solution by iron oxides results in the formation of a variety of reactive surface species capable of reducing polyhalogenated methanes (PHMs). Pseudo-first-order reaction rate constants, k obs , of PHMs increased in the order CHBrCl 2 < CHBr 2 Cl < CHBr 3 < CCl 4 < CFBr 3 < CBrCl 3 < CBr 2 Cl 2. The k obs values increased with the exposure time, t eq , of Fe(II) to suspended iron oxides which was attributed to the rearrangement of initially sorbed Fe(II) species to more reactive surface species with time. At pH 7.2, the k obs values of PHMs also increased with the concentration of surface-bound ferrous iron, Fe(II) sorb , particularly when Fe(II) tot was increased to concentrations where surface precipitation becomes likely. At fixed total Fe(II) concentrations, k obs values increased exponentially with pH. The highest reactivities were associated with pH conditions where surface precipitation of Fe(II) is expected. Fe(II) sorb and pH, however, had opposite effects on the product formation of PHMs. At pH 7.2, the formation of formate from CX 4 (X) Cl, Br) increased with Fe(II) sorb , whereas increasing pH favored the formation of CHX 3. The ratio of halogenated products and formate formed is indicative of the relative importance of initial one-or two-electron-transfer processes, respectively, and was found to depend on the type of iron oxide mineral also. Our data form a basis to assess the importance of chemical reactions in natural attenuation processes of PHMs in environmental systems under ironreducing conditions.
AGU Fall Meeting Abstracts, Dec 1, 2012
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Papers by Stefan B Haderlein