A5023072528- Water Treatment and Disinfection
- Chemical Analysis and Environmental Impact
- Groundwater and Isotope Geochemistry
- Isotope Analysis in Ecology
- Toxic Organic Pollutants Impact
- Groundwater flow and contamination studies
- Microbial bioremediation and biosurfactants
- Radioactive contamination and transfer
- Atmospheric and Environmental Gas Dynamics
- Atmospheric chemistry and aerosols
- Wastewater Treatment and Nitrogen Removal
- Radioactive element chemistry and processing
- Air Quality and Health Impacts
- Hydrocarbon exploration and reservoir analysis
- Nuclear Physics and Applications
- Energetic Materials and Combustion
- Pharmaceutical and Antibiotic Environmental Impacts
- Methane Hydrates and Related Phenomena
- Chemical Reactions and Isotopes
- Chemical Synthesis and Characterization
- Atmospheric aerosols and clouds
- Radioactivity and Radon Measurements
- Environmental remediation with nanomaterials
- Mercury impact and mitigation studies
- Extraction and Separation Processes
University of Delaware
2016-2024
University of Illinois Chicago
2002-2014
Weatherford College
2011
United States Geological Survey
2007-2009
Texas Tech University
2009
Los Alamos National Laboratory
2009
Oak Ridge National Laboratory
2009
Woods Hole Oceanographic Institution
2000-2007
Swiss Federal Institute of Aquatic Science and Technology
2007
University of California, Santa Barbara
2002
A nonaqueous, high-temperature method is described for converting micromole quantities of chlorinated volatile organic compounds to CO2 and CH3Cl C Cl isotope ratio determinations. This provides an improved analytical approach using ratios in studies the biodegradation environment. Conversion reagent + CuCl then conversion back by present gives typical yields 99 ± 1% 91 CH3Cl, both products >99% purity. An offset −0.23 0.05‰ observed between 37Cl/35Cl product initial CH3Cl. Precision...
Natural attenuation of chlorinated aliphatic hydrocarbons (CAHs) can be an important mechanism for groundwater remediation. It is difficult to determine the effectiveness natural CAH from chemical analyses samples because mixing, dispersion, and secondary reactions mask evidence attenuation. In this paper, we explore application stable chlorine isotope ratio measurements as a new tool evaluating CAHs. We report ratios in both trichloroethene (TCE) inorganic chloride aerobic aquifer beneath...
Abstract. In order to determine the wavelength dependence of fine (<1 micron) atmospheric aerosol absorption in Mexico City area, Ångstrom exponents (AAEs) were calculated from hourly averages measured at seven wavelengths (370, 450, 520, 590, 660, 880, and 950 nm) with an aethalometer during two field campaigns, Metropolitan Area study April 2003 (MCMA 2003) Megacity Initiative: Local Global Research Observations March 2006 (MILAGRO). These results compared AAEs determined laboratory...
Perchlorate is a widespread environmental contaminant having both anthropogenic and natural sources. Stable isotope ratios of O Cl in given sample perchlorate may be used to distinguish its source(s). Isotopic also useful for identifying the extent biodegradation perchlorate, which critical assessing attenuation this groundwater. For approach useful, however, kinetic isotopic fractionations during must first determined as function variables such temperature bacterial species. A laboratory...
Perchlorate contamination of surface water and groundwater is an emerging public health problem that has adversely affected the drinking supplies millions people in western United States. Microbial reduction shown promise as a cost-effective means for situ bioremediation perchlorate-contaminated water. Measurements stable isotope ratios light elements (H, C, N, O, S, Cl) can often be used to distinguish biodegradation organic inorganic molecules from abiotic loss mechanisms such adsorption,...
We investigated the extent and variability of C Cl isotope fractionation during reduction polychlorinated ethanes to evaluate potential use analysis for assessment contaminant transformation in subsurface environments. Kinetic effects (KIE) reductive β-elimination 1,1,2,2-tetrachloroethane (1,1,2,2-TeCA), pentachloroethane (PCA), hexachloroethane by Cr(II) used as model reductant homogeneous solution were compared KIEs measured dehydrochlorination 1,1,2,2-TeCA PCA. Since isotopic reactions...
Perchlorate (ClO4−) is ubiquitous in the environment. It produced naturally by atmospheric photochemical reactions, and also synthesized large quantities for military, aerospace, industrial applications. Nitrate-enriched salt deposits of Atacama Desert (Chile) contain high concentrations natural ClO4−, have been exported worldwide since mid-1800s use agriculture. The widespread introduction synthetic agricultural ClO4− into environment has contaminated numerous municipal water supplies....
2,4-Dinitroanisole (DNAN) is a main constituent in various new insensitive munition formulations. Although DNAN susceptible to biotic and abiotic transformations, many environmental instances, transformation mechanisms are difficult resolve, distinguish, or apportion on the basis solely of analysis concentrations. We used compound-specific isotope (CSIA) investigate characteristic fractionations (by three microbial consortia pure cultures) 9,10-anthrahydroquinone-2-sulfonic acid [AHQS])...
An exploratory investigation was conducted to evaluate if stable chlorine isotopic ratios of polychlorinated biphenyls (PCBs) could be useful in studying the processes that determine their transport and fate environment. First, we determined variability δ37Cl source materials for PCBs. Second, values contaminated environmental samples fell outside range variability. The among (Aroclors) rather small; ranged from −3.37 −2.11‰ (mean standard deviation, −2.78 ± 0.39‰, n = 12). There no...
Analyses of stable isotope ratios chlorine and oxygen in perchlorate can, some cases, be used for mapping source identification groundwater plumes. This is demonstrated here large, intersecting plumes from a region having extensive contamination large population dependent on resources. The contains both synthetic derived rocket fuel manufacturing testing activities agricultural predominantly imported Chilean (Atacama) nitrate fertilizer, along with likely component indigenous natural...
Several chlorinated organic compounds (COCs) that have been detected in a wide range of human, animal, and environmental samples may be derived from natural or anthropogenic sources. To determine whether the Cl isotope ratios these could used to differentiate sources, we investigated chlorine effect for enzyme-catalyzed chlorination. Two aromatic substrates, 1,3,5-trimethylbenzene (TMB) 3,5-dimethylphenol (DMP), were treated with chloroperoxidase isolated fungus Caldariomyces fumago. A...
Environmental context. Perchlorate (ClO4–) and nitrate (NO3–) are common co-contaminants in groundwater, with both natural anthropogenic sources. Each of these compounds is biodegradable, so situ enhanced bioremediation one alternative for treating them groundwater. Because bacteria typically fractionate isotopes during biodegradation, stable isotope analysis increasingly used to distinguish this process from transport or mixing-related decreases contaminant concentrations. However,...
Here we report on a set of six apatite reference materials (chlorapatites MGMH#133648, TUBAF#38 and fluorapatites MGMH#128441A, TUBAF#37, 40, 50) which have characterised for their chlorine isotope ratios; these RMs span range Cl mass fractions within the Ca 10 (PO 4 ) 6 (F,Cl,OH) 2 solid solution series. Numerous specimens, obtained from mineralogical collections, were initially screened 37 Cl/ 35 homogeneity using SIMS followed by δ characterisation gas source spectrometry both dual‐inlet...
ABSTRACT Kinetic isotopic fractionation of carbon and nitrogen during RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) biodegradation was investigated with pure bacterial cultures under aerobic anaerobic conditions. Relatively large bulk enrichments in 15 N were observed via ring cleavage (ε = −12.7‰ ± 0.8‰) nitro reduction −9.9‰ 0.7‰), comparison to smaller effects denitration −2.4‰ 0.2‰). 13 C enrichment negligible −0.8‰ 0.5‰) but larger degradation −4.0‰ 0.8‰), modest variability among...
The environmental fate of insensitive munitions compounds, such as 2,4-dinitroanisole (DNAN), has drawn increasing attention because their growing use in military activities. One the main attenuation mechanisms DNAN degradation aqueous environments is alkaline hydrolysis. We investigated pathway for hydrolysis at pH 12 by a combined approach experiment and theory. An using 18O-labeled water was performed to verify reaction pathway. Calculated free energies two putative pathways...
Perchlorate (ClO4- ) is a common trace constituent of water, soils, and plants; it has both natural synthetic sources subject to biodegradation. The stable isotope ratios Cl O provide three independent quantities for ClO4- source attribution attenuation studies: δ37 Cl, δ18 O, δ17 (or Δ17 or 17 Δ) values. Documented reference materials, calibration schemes, methods, interferences will improve the reliability such studies.Three large batches KClO4 with contrasting isotopic compositions were...
Radiokrypton isotopes ((81)Kr and (85)Kr) are ideal tracers chronometers of various environmental processes. Atom trap trace analysis (ATTA) is capable determining the ultralow isotopic abundances radiokryptons (<10(-12)) provided that 50 microL pure Kr available. The by using ATTA (81)Kr in naturally occurring gases interest, e.g., dissolved hydrological reservoirs, requires separation parts-per-million (ppm) level from chemically airlike bulk gas. A newly developed purification system...