-
Global Change Biology Mar 2022Unprecedented nitrogen (N) inputs into terrestrial ecosystems have profoundly altered soil N cycling. Ammonia oxidizers and denitrifiers are the main producers of...
Unprecedented nitrogen (N) inputs into terrestrial ecosystems have profoundly altered soil N cycling. Ammonia oxidizers and denitrifiers are the main producers of nitrous oxide (N O), but it remains unclear how ammonia oxidizer and denitrifier abundances will respond to N loading and whether their responses can predict N-induced changes in soil N O emission. By synthesizing 101 field studies worldwide, we showed that N loading significantly increased ammonia oxidizer abundance by 107% and denitrifier abundance by 45%. The increases in both ammonia oxidizer and denitrifier abundances were primarily explained by N loading form, and more specifically, organic N loading had stronger effects on their abundances than mineral N loading. Nitrogen loading increased soil N O emission by 261%, whereas there was no clear relationship between changes in soil N O emission and shifts in ammonia oxidizer and denitrifier abundances. Our field-based results challenge the laboratory-based hypothesis that increased ammonia oxidizer and denitrifier abundances by N loading would directly cause higher soil N O emission. Instead, key abiotic factors (mean annual precipitation, soil pH, soil C:N ratio, and ecosystem type) explained N-induced changes in soil N O emission. Altogether, these findings highlight the need for considering the roles of key abiotic factors in regulating soil N transformations under N loading to better understand the microbially mediated soil N O emission.
Topics: Ammonia; Denitrification; Ecosystem; Nitrification; Nitrogen; Nitrous Oxide; Soil; Soil Microbiology
PubMed: 34923712
DOI: 10.1111/gcb.16042 -
Molecules (Basel, Switzerland) Dec 2022The environmentally benign Fe(MoO) plays a crucial role in the transformation of organic contaminants, either through catalytically decomposing oxidants or through...
The environmentally benign Fe(MoO) plays a crucial role in the transformation of organic contaminants, either through catalytically decomposing oxidants or through directly oxidizing the target pollutants. Because of their dual roles and the complex surface chemical reactions, the mechanism involved in Fe(MoO)-catalyzed PDS activation processes remains obscure. In this study, Fe(MoO) was prepared via the hydrothermal and calcine method, and photoFenton degradation of methyl orange (MO) was used to evaluate the catalytic performance of Fe(MoO). Fe(MoO) catalysts with abundant surface oxygen vacancies were used to construct a synergistic system involving a photocatalyst and PDS activation. The oxygen vacancies and Fe/Fe shuttle played key roles in the novel pathways for generation of •O, h, and O in the UV-Vis + PDS + FMO-6 photoFenton system. This study advances the fundamental understanding of the underlying mechanism involved in the transition metal oxide-catalyzed PDS activation processes.
Topics: Oxygen; Catalysis; Oxides
PubMed: 36615527
DOI: 10.3390/molecules28010333 -
Journal of Hazardous Materials Feb 2022Polyethylene (PE) plastics are highly recalcitrant and resistant to photo-oxidative degradation due to its chemically inert backbone structure. We applied two novel...
Polyethylene (PE) plastics are highly recalcitrant and resistant to photo-oxidative degradation due to its chemically inert backbone structure. We applied two novel reactions such as, Bio-Fenton reaction using glucose oxidase (GOx) enzyme alone and Bio-Photo-Fenton reaction using GOx immobilized on TiO nanoparticles (TiO-GOx) under UV radiation, for (bio)degradation of pre-activated PE with sulfonation (SPE). From both the reactions, GC-MS analyses identified small organic acids such as, acetic acid and butanoic acid as a major metabolites released from SPE. In the presence of UV radiation, 21 fold and 17 fold higher amounts of acetic acid (4.78 mM) and butanoic acid (0.17 mM) were released from SPE after 6 h of reaction using TiO-GOx than free GOx, which released 0.22 mM and 0.01 mM of acetic acid and butanoic acid, respectively. Our results suggest that (bio)degradation and valorization of naturally weathered and oxidized PE using combined reactions of biochemistry, photochemistry and Fenton chemistry could be possible.
Topics: Glucose Oxidase; Hydrogen Peroxide; Iron; Polyethylene; Titanium
PubMed: 34488097
DOI: 10.1016/j.jhazmat.2021.127067 -
Molecules (Basel, Switzerland) May 2017A suitable oxidative system is crucial to electrophilic selenium catalysis (ESC). This short review offers the overview of recent development in ESC with electrophilic... (Review)
Review
A suitable oxidative system is crucial to electrophilic selenium catalysis (ESC). This short review offers the overview of recent development in ESC with electrophilic N-F reagents as the oxidants. Several highly selective transformations of alkenes such as allylic or vinylic imidation, pyridination, -dichlorination, oxidative cyclization and asymmetric cyclization have been described.
Topics: Alkenes; Benzofurans; Catalysis; Cyclization; Imidoesters; Indoles; Molecular Structure; Organoselenium Compounds; Oxidants; Oxidation-Reduction; Pyridines; Stereoisomerism; Sulfonamides
PubMed: 28534837
DOI: 10.3390/molecules22050835 -
Applied and Environmental Microbiology Jan 2024Denitrification is a form of anaerobic respiration wherein nitrate (NO) is sequentially reduced via nitrite (NO), nitric oxide, and nitrous oxide (NO) to dinitrogen gas...
Denitrification is a form of anaerobic respiration wherein nitrate (NO) is sequentially reduced via nitrite (NO), nitric oxide, and nitrous oxide (NO) to dinitrogen gas (N) by four reductase enzymes. Partial denitrifying bacteria possess only one or some of these four reductases and use them as independent respiratory modules. However, it is unclear if partial denitrifiers sense and respond to denitrification intermediates outside of their reductase repertoire. Here, we tested the denitrifying capabilities of two purple nonsulfur bacteria, CGA0092 and SB1003. Each had denitrifying capabilities that matched their genome annotation; CGA0092 reduced NO to N, and SB1003 reduced NO to N. For each bacterium, NO reduction could be used both for electron balance during growth on electron-rich organic compounds in light and for energy transformation via respiration in darkness. However, NO reduction required supplementation with a denitrification intermediate, including those for which there was no associated denitrification enzyme. For CGA0092, NO served as a stable, non-catalyzable molecule that was sufficient to activate NO reduction. Using a β-galactosidase reporter, we found that NO acted, at least in part, by stimulating NO reductase gene expression. In SB1003, NO but not NO activated NO reduction, but NO was slowly removed, likely by a promiscuous enzyme activity. Our findings reveal that partial denitrifiers can still be subject to regulation by denitrification intermediates that they cannot use.IMPORTANCEDenitrification is a form of microbial respiration wherein nitrate is converted via several nitrogen oxide intermediates into harmless dinitrogen gas. Partial denitrifying bacteria, which individually have some but not all denitrifying enzymes, can achieve complete denitrification as a community by cross-feeding nitrogen oxide intermediates. However, the last intermediate, nitrous oxide (N2O), is a potent greenhouse gas that often escapes, motivating efforts to understand and improve the efficiency of denitrification. Here, we found that at least some partial denitrifying N2O reducers can sense and respond to nitrogen oxide intermediates that they cannot otherwise use. The regulatory effects of nitrogen oxides on partial denitrifiers are thus an important consideration in understanding and applying denitrifying bacterial communities to combat greenhouse gas emissions.
Topics: Nitrous Oxide; Denitrification; Nitrates; Greenhouse Gases; Nitrogen Dioxide; Bacteria; Nitric Oxide; Oxidoreductases
PubMed: 38078768
DOI: 10.1128/aem.01741-23 -
TheScientificWorldJournal Apr 2003Atmospheric chemistry is an important discipline for understanding air pollution and its impacts. This mini-review gives a brief history of air pollution and presents an... (Review)
Review
Atmospheric chemistry is an important discipline for understanding air pollution and its impacts. This mini-review gives a brief history of air pollution and presents an overview of some of the basic photochemistry involved in the production of ozone and other oxidants in the atmosphere. Urban air quality issues are reviewed with a specific focus on ozone and other oxidants, primary and secondary aerosols, alternative fuels, and the potential for chlorine releases to amplify oxidant chemistry in industrial areas. Regional air pollution issues such as acid rain, long-range transport of aerosols and visibility loss, and the connections of aerosols to ozone and peroxyacetyl nitrate chemistry are examined. Finally, the potential impacts of air pollutants on the global-scale radiative balances of gases and aerosols are discussed briefly.
Topics: Acid Rain; Aerosols; Air Pollution; Atmosphere; Chlorine; Fossil Fuels; Free Radicals; Greenhouse Effect; Organic Chemicals; Oxidants, Photochemical; Peracetic Acid; Photochemistry; Smog
PubMed: 12806107
DOI: 10.1100/tsw.2003.18 -
The ISME Journal Apr 2021Elevated dissolved iron concentrations in the methanic zone are typical geochemical signatures of rapidly accumulating marine sediments. These sediments are often...
Elevated dissolved iron concentrations in the methanic zone are typical geochemical signatures of rapidly accumulating marine sediments. These sediments are often characterized by co-burial of iron oxides with recalcitrant aromatic organic matter of terrigenous origin. Thus far, iron oxides are predicted to either impede organic matter degradation, aiding its preservation, or identified to enhance organic carbon oxidation via direct electron transfer. Here, we investigated the effect of various iron oxide phases with differing crystallinity (magnetite, hematite, and lepidocrocite) during microbial degradation of the aromatic model compound benzoate in methanic sediments. In slurry incubations with magnetite or hematite, concurrent iron reduction, and methanogenesis were stimulated during accelerated benzoate degradation with methanogenesis as the dominant electron sink. In contrast, with lepidocrocite, benzoate degradation, and methanogenesis were inhibited. These observations were reproducible in sediment-free enrichments, even after five successive transfers. Genes involved in the complete degradation of benzoate were identified in multiple metagenome assembled genomes. Four previously unknown benzoate degraders of the genera Thermincola (Peptococcaceae, Firmicutes), Dethiobacter (Syntrophomonadaceae, Firmicutes), Deltaproteobacteria bacteria SG8_13 (Desulfosarcinaceae, Deltaproteobacteria), and Melioribacter (Melioribacteraceae, Chlorobi) were identified from the marine sediment-derived enrichments. Scanning electron microscopy (SEM) and catalyzed reporter deposition fluorescence in situ hybridization (CARD-FISH) images showed the ability of microorganisms to colonize and concurrently reduce magnetite likely stimulated by the observed methanogenic benzoate degradation. These findings explain the possible contribution of organoclastic reduction of iron oxides to the elevated dissolved Fe pool typically observed in methanic zones of rapidly accumulating coastal and continental margin sediments.
Topics: Benzoates; Ferric Compounds; Geologic Sediments; In Situ Hybridization, Fluorescence; Iron; Oxidation-Reduction; Oxides
PubMed: 33154547
DOI: 10.1038/s41396-020-00824-7 -
International Journal of Environmental... Aug 2022Chlorinated organic compounds (COCs) are among the more toxic organic compounds frequently found in soil and groundwater. Among these, toxic and low-degradable...
Chlorinated organic compounds (COCs) are among the more toxic organic compounds frequently found in soil and groundwater. Among these, toxic and low-degradable chlorobenzenes are commonly found in the environment. In this work, an innovative process using hydrogen peroxide as the oxidant, ferrioxalate as the catalyst and a visible light-emitting diode lamp (Vis LED) were applied to successfully oxidize 124-trichlorobenzene (124-TCB) in a saturated aqueous solution of 124-TCB (28 mg L) at a neutral pH. The influence of a hydrogen peroxide (HP) concentration (61.5-612 mg L), Fe (Fe) dosage (3-10 mg L), and irradiation level (Rad) (I = 0.12 W cm and I = 0.18 W cm) on 124-TCB conversion and dechlorination was studied. A D-Optimal experimental design combined with response surface methodology (RSM) was implemented to maximize the quality of the information obtained. The ANOVA test was used to assess the significance of the model and its coefficients. The maximum pollutant conversion at 180 min (98.50%) was obtained with Fe = 7 mg L, HP = 305 mg L, and I = 0.12 W cm. The effect of two inorganic anions usually presents in real groundwater (bicarbonate and chloride, 600 mg L each) was investigated under those optimized operating conditions. A slight reduction in the 124-TCB conversion after 180 min of reaction was noticed in the presence of bicarbonate (8.31%) and chloride (7.85%). Toxicity was studied with Microtox® (Azur Environmental, Carlsbad, CA, USA) bioassay, and a remarkable toxicity decrease was found in the treated samples, with the inhibition proportional to the remaining 124-TCB concentration. That means that nontoxic byproducts are produced in agreement with the high dechlorination degrees noticed.
Topics: Bicarbonates; Chlorides; Chlorobenzenes; Hydrogen Peroxide; Hydrogen-Ion Concentration; Iron; Oxalates; Oxidation-Reduction
PubMed: 35955089
DOI: 10.3390/ijerph19159733 -
Molecules (Basel, Switzerland) Oct 2022The Mitsunobu reaction plays a vital part in organic chemistry due to its wide synthetic applications. It is considered as a significant reaction for the interconversion... (Review)
Review
The Mitsunobu reaction plays a vital part in organic chemistry due to its wide synthetic applications. It is considered as a significant reaction for the interconversion of one functional group (alcohol) to another (ester) in the presence of oxidizing agents (azodicarboxylates) and reducing agents (phosphines). It is a renowned stereoselective reaction which inverts the stereochemical configuration of end products. One of the most important applications of the Mitsunobu reaction is its role in the synthesis of natural products. This review article will focus on the contribution of the Mitsunobu reaction towards the total synthesis of natural products, highlighting their biological potential during recent years.
Topics: Biological Products; Phosphines; Reducing Agents; Esters; Oxidants
PubMed: 36296545
DOI: 10.3390/molecules27206953 -
Environmental Science & Technology Sep 2023Organic peroxides are key intermediates in the atmosphere but are challenging to detect, especially in the particle phase, due to their instability, which has led to...
Organic peroxides are key intermediates in the atmosphere but are challenging to detect, especially in the particle phase, due to their instability, which has led to substantial gaps in the understanding of their environmental effects. We demonstrate that matrix-assisted ionization in vacuum (MAIV) mass spectrometry (MS), which does not require an ionization source, enables characterization of peroxides and other products in the surface layers of organic particles. Hydroxyl radical oxidation of glutaric acid particles yields hydroperoxides and organic peroxides, which were detected with signals of the same order of magnitude as the major, more stable products. Product identification is supported by MS/MS analysis, peroxide standards, and offline high-resolution MS. The peroxide signals relative to the stable carbonyl and alcohol products are significantly larger using MAIV compared to those in the offline bulk analysis. This is also the case for analysis using fast, online easy ambient sonic-spray ionization mass spectrometry. These studies demonstrate the advantage of MAIV for the real-time characterization of labile peroxides in the surface layers of solid particles. The presence of peroxides on the surface may be important for surface oxidation processes as well as for the toxicity of inhaled particles.
Topics: Peroxides; Tandem Mass Spectrometry; Vacuum; Hydrogen Peroxide; Aerosols
PubMed: 37695633
DOI: 10.1021/acs.est.3c02895