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Magnetic Resonance Imaging of the Effect of Zeolite on Lithium Uptake in Poplar Michael J. Harbottle,* Michael D. Mantle, Michael L. Johns, René van Herwijnen, Abir Al-Tabbaa, Tony R. Hutchings, Andy J. Moffat, and Sabeha K. Ouki Department of Engineering, Cambridge University, Trumpington Street, Cambridge, CB2 1PZ, UK, Department of Chemical Engineering, Cambridge University, New Museums Site, Pembroke Street, Cambridge, CB2 3RA, UK, Forest Research, Alice Holt Research Station, Alice Holt Lodge, Farnham, Surrey, GU10 4LH, UK, and School of Engineering, University of Surrey, Guildford, Surrey, GU2 7XH, UK Received for review September 27, 2006 Revised manuscript received February 14, 2007 Accepted March 5, 2007 Abstract: The use of a zeolite (clinoptilolite) to protect poplar plants from lithium-contaminated soil has been studied using magnetic resonance imaging. Lithium was used as a model contaminant as it could be tracked directly using specific nuclear magnetic resonance probes, rather than relying on relaxation time effects on protons due to paramagnetic solutes. The sorption of lithium to the zeolite was investigated both in static and dynamic systems; lithium was found to sorb readily to the zeolite over time. Poplar plants were grown in soil microcosms consisting of either sand or sand and zeolite with nutrients provided through the use of Hoagland's solution as the pore fluid. Both one-dimensional profiles of lithium concentration along poplar stems and direct lithium imaging of stem cross-sections were employed to reveal the uptake of the contaminant into the plant structure, showing significantly less lithium present in plants grown in sand and zeolite than those grown in sand alone. Evidence of structural features involved in the uptake of lithium was also obtained. -------------------------------------------------------------------------------- Laccase-Mediated Michael Addition of 15N-Sulfapyridine to a Model Humic Constituent Heidi M. Bialk, Curtis Hedman, Alex Castillo, and Joel A. Pedersen*# Molecular and Environmental Toxicology Center, Departments of Biochemistry and Soil Science, and Environmental Chemistry and Technology Program, University of Wisconsin, Madison, Wisconsin 53706, and Wisconsin State Laboratory of Hygiene, Madison, Wisconsin 53718 Received for review July 20, 2006 Revised manuscript received January 8, 2007 Accepted February 9, 2007 Abstract: Chemical incorporation of sulfonamide antimicrobials into natural organic matter may represent an important process influencing the fate of these synthetic, primarily agents in soil and sediment environments. We previously demonstrated that a fungal peroxidase mediates covalent coupling of sulfonamide antimicrobials to model humic constituents; reactions with the 2,6-dimethoxyphenol syringic acid produced Schiff bases (Bialk et al. Environ. Sci. Technol. 2005, 39, 4436-4473). Here, we show that fungal laccase-mediated reaction of sulfapyridine with the ortho-dihydroxyphenol protocatechuic acid yields a Michael adduct. We synthesized 15N-enriched sulfapyridine to facilitate determination of the covalent linkage(s) formed between sulfapyridine and protocatechuic acid by NMR spectroscopy. 1H-15N heteronuclear multiple bond correlation experiments and tandem mass spectrometry demonstrated that the sulfapyridine anilinic nitrogen engaged in a Michael addition reaction to oxidized protocatechuic acid to form an anilinoquinone. Michael adducts are more stable than the previously reported imine linkages between sulfonamides and 2,6-dimethoxyphenols. Michael addition to quinone-like structures in soil organic matter is expected to diminish the mobility and biological activity of sulfonamide antimicrobials. -------------------------------------------------------------------------------- Mobilization of Arsenic During One-Year Incubations of Grey Aquifer Sands from Araihazar, Bangladesh Kathleen A. Radloff,* Zhongqi Cheng, Mohammad W. Rahman, Kazi M. Ahmed, Brian J. Mailloux, Andrew R. Juhl, Peter Schlosser, and Alexander van Geen 1Department of Earth and Environmental Engineering, Columbia University, New York, New York 10025, Lamont-Doherty Earth Observatory of Columbia University, Palisades, New York 10964, Department of Geology, University of Dhaka, Dhaka, Bangladesh, and Barnard College, Columbia University, New York, New York 10025 Received for review December 7, 2006 Revised manuscript received March 5, 2007 Accepted March 12, 2007 Abstract: Elevated As concentrations in shallow groundwater pose a major health threat in Bangladesh and similarly affected countries, yet there is little consensus on the mechanism of As release to groundwater or how it might be influenced by human activities. In this study, the rate of As release was measured directly with incubations lasting 11 months, using sediment and groundwater collected simultaneously in Bangladesh and maintained under anaerobic conditions throughout the study. Groundwater and gray sediment were collected as diluted slurries between 5 and 38 m in depth, a range over which ambient groundwater As concentrations increased from 20 to 100 g L-1. Arsenic was released to groundwater in slurries from 5 and 12 m in depth at a relatively constant rate of 21 ± 4 (2 ) and 23 ± 6 g As kg-1 yr-1, respectively. Amendment with a modest level of acetate increased the rate of As release only at 12 m (82 ± 18 g kg-1 yr-1). Although the groundwater As concentration was initially highest at 38 m depth, no release of As was observed. These results indicate that the spatial distribution of dissolved As in Bangladesh and local rates of release to groundwater are not necessarily linked. Iron release during the incubations did not occur concurrently with As release, providing further confirmation that the two processes are not directly coupled. Small periodic additions of oxygen suppressed the release of As from sediments at all three depths, which supports the notion that anoxia is a prerequisite for accumulation of As in Bangladesh groundwater. -------------------------------------------------------------------------------- Urinary Methoxyphenol Biomarkers and Woodsmoke Exposure: Comparisons in Rural Guatemala with Personal CO and Kitchen CO, Levoglucosan, and PM2.5 Michael Clark, Michael Paulsen, Kirk R. Smith, Eduardo Canuz, and Christopher D. Simpson* Environmental Health Sciences, School of Public Health, University of California at Berkeley, 140 Warren Hall, Berkeley, California 94720, Environmental and Occupational Health Sciences, School of Public Health and Community Medicine, University of Washington, Box 357234, Seattle, Washington 98195-7234, and Centro de Estudios en Salud, Universidad Del Valle, Guatemala City, Guatemala Received for review June 27, 2006 Revised manuscript received November 27, 2006 Accepted December 6, 2006 Abstract: Urinary methoxyphenols have been proposed as biomarkers for woodsmoke exposure, but few field studies have been undertaken. We evaluated these biomarkers for assessing the exposure to woodsmoke of householders in rural Guatemala. The study population was a subset (10 female cooks, 2 female non-cooks, and 8 male non-cooks ranging in age from 7 to 60) drawn from those participating in a longterm randomized intervention trial (RESPIRE) in the highlands. All households rely solely on woodburning for cooking and home heating. Approximately half of the homes in the trial used open woodfires in the home, while the intervention group used cookstoves, called "planchas," that vent most of the woodsmoke outdoors through a chimney. Corrected for creatinine levels, 16 of the 19 methoxyphenols measured were lower in the urine of cooks using the plancha; and 11 of the 19 compounds were lower in the urine of non-cooks from homes using the plancha. Furthermore, the 4 low-molecular-weight syringyl methoxyphenols (syringol, methysyringol, ethylsyringol, propylsyringol) were each moderately correlated (r 2 = 0.71, 0.64, 0.68, 0.53 respectively, with all p < 0.05) with personal exposure measurements determined by carbon monoxide (CO) passive diffusion tubes, but not with CO in exhaled breath. 48-Hour kitchen area measurements of PM2.5 mass, PM2.5 levoglucosan, and CO were highly correlated (>0.89) with each other and moderately correlated (0.54-0.78) with personal CO measurements. Although based on relatively few measure ments, this study demonstrates that the urinary concentra tions of specific methoxyphenols may be effective biomarkers of short-term exposures to inhaled woodsmoke in field conditions. -------------------------------------------------------------------------------- 如果需要原文，请留下邮箱  |
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