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Photo-tautomerization of acetaldehyde as a photochemical source of formic acid in the troposphere.

ABSTRACT: Organic acids play a key role in the troposphere, contributing to atmospheric aqueous-phase chemistry, aerosol formation, and precipitation acidity. Atmospheric models currently account for less than half the observed, globally averaged formic acid loading. Here we report that acetaldehyde photo-tautomerizes to vinyl alcohol under atmospherically relevant pressures of nitrogen, in the actinic wavelength range, ??=?300-330?nm, with measured quantum yields of 2-25%. Recent theoretical kinetics studies show hydroxyl-initiated oxidation of vinyl alcohol produces formic acid. Adding these pathways to an atmospheric chemistry box model (Master Chemical Mechanism) demonstrates increased formic acid concentrations by a factor of ~1.7 in the polluted troposphere and a factor of ~3 under pristine conditions. Incorporating this mechanism into the GEOS-Chem 3D global chemical transport model reveals an estimated 7% contribution to worldwide formic acid production, with up to 60% of the total modeled formic acid production over oceans arising from photo-tautomerization.

SUBMITTER: Shaw MF

PROVIDER: S-EPMC6030138 | biostudies-literature | 2018 Jul

REPOSITORIES: biostudies-literature

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Photo-tautomerization of acetaldehyde as a photochemical source of formic acid in the troposphere.

Shaw Miranda F MF Sztáray Bálint B Whalley Lisa K LK Heard Dwayne E DE Millet Dylan B DB Jordan Meredith J T MJT Osborn David L DL Kable Scott H SH

Nature communications 20180703 1

Organic acids play a key role in the troposphere, contributing to atmospheric aqueous-phase chemistry, aerosol formation, and precipitation acidity. Atmospheric models currently account for less than half the observed, globally averaged formic acid loading. Here we report that acetaldehyde photo-tautomerizes to vinyl alcohol under atmospherically relevant pressures of nitrogen, in the actinic wavelength range, λ = 300-330 nm, with measured quantum yields of 2-25%. Recent theoretical kinetics stu ...[more]

PMID: 29968712

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Project description:The choice of the calcium (Ca) source in pig diets and the addition of formic acid may affect the gastrointestinal inositol phosphate (InsP) degradation and thereby, phosphorus (P) digestibility in pigs. This study assessed the effects of different Ca sources (Ca carbonate, Ca formate), exogenous phytase, and chemical acidification on InsP degradation, nutrient digestion and retention, blood metabolites, and microbiota composition in growing pigs. In a randomized design, 8 ileal-cannulated barrows (24 kg initial BW) were fed 5 diets containing Ca formate or Ca carbonate as the only mineral Ca addition, with or without 1,500 FTU/kg of an exogenous hybrid 6-phytase. A fifth diet was composed of Ca carbonate with phytase but with 8 g formic acid/kg diet. No mineral P was added to the diets. Prececal InsP6 disappearance and P digestibility were lower (P ≤ 0.032) in pigs fed diets containing Ca formate. In the presence of exogenous phytase, InsP5 and InsP4 concentrations in the ileal digesta were lower (P ≤ 0.019) with Ca carbonate than Ca formate. The addition of formic acid to Ca carbonate with phytase diet resulted in greater (P = 0.027) prececal InsP6 disappearance (87% vs. 80%), lower (P = 0.001) InsP5 concentration, and greater (P ≤ 0.031) InsP2 and myo-inositol concentrations in the ileal digesta. Prececal P digestibility was greater (P = 0.004) with the addition of formic acid compared to Ca carbonate with phytase alone. Prececal amino acid (AA) digestibility of some AA was greater with Ca formate compared to Ca carbonate but only in diets with phytase (P ≤ 0.048). The addition of formic acid to the diet with Ca carbonate and phytase increased (P ≤ 0.006) the prececal AA digestibility of most indispensable AA. Exogenous phytase affected more microbial genera in the feces when Ca formate was used compared to Ca carbonate. In the ileal digesta, the Ca carbonate diet supplemented with formic acid and phytase led to a similar microbial community as the Ca formate diets. In conclusion, Ca formate reduced prececal InsP6 degradation and P digestibility, but might be of advantage in regard to prececal AA digestibility in pigs compared to Ca carbonate when exogenous phytase is added. The addition of formic acid to Ca carbonate with phytase, however, resulted in greater InsP6 disappearance, P and AA digestibility values, and changed ileal microbiota composition compared to Ca carbonate with phytase alone.

Dataset Information

Photo-tautomerization of acetaldehyde as a photochemical source of formic acid in the troposphere.

Publications

Photo-tautomerization of acetaldehyde as a photochemical source of formic acid in the troposphere.

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