A theoretical study on the environmental oxidation of fenpyrazamine fungicide initiated by hydroxyl radicals in the aqueous phase.

Fenpyrazamine (FPA) is a widely used fungicide in agriculture to control fungal diseases, but its environmental degradation by oxidants and the formation of potential degradation products remain unexplored. This study investigates the oxidation of FPA by hydroxyl radicals (HO˙) using density functional theory (DFT) calculations at the M06-2X/6-311++G(3df,3pd)//M06-2X/6-31+G(d,p) level of theory. Three standard oxidation mechanisms, including formal hydrogen transfer (FHT), radical adduct formation (RAF), and single electron transfer (SET), were evaluated in the aqueous phase, with reaction kinetics analyzed over a temperature range of 283-333 K.

Non-targeted analysis and suspect screening of organic contaminants in temperate snowfall using liquid chromatography high-resolution mass spectrometry.

Contaminants released into the atmosphere that undergo regional and long-range transport can deposit back to Earth through snowfall. When snow melts, these contaminants re-enter the environment, sometimes far from their original emission sources. Here we present the first comprehensive characterization of organic contaminants in snow from North America.

Welcome to 310 Environmental Working Group! A Group Project That Places Students in the Role of Consultants Helping Businesses Choose the Most Climate Friendly Fluorinated Gas.

The Montreal Protocol is an international treaty that controls substances that deplete the ozone layer. Through the control of halogenated gases, it has been one of the most successful climate legislations to date. This success is driven by the interplay between chemical regulation and smart chemical design, demonstrating the positive impact chemistry can have on the world.

Ligand bound structure of a 6-hydroxynicotinic acid 3-monooxygenase provides mechanistic insights.

6-Hydroxynicotinic acid 3-monooxygenase (NicC) is a bacterial enzyme involved in the degradation of nicotinic acid. This enzyme is a Class A flavin-dependent monooxygenase that catalyzes a unique decarboxylative hydroxylation. The unliganded structure of this enzyme has previously been reported and studied using steady- and transient-state kinetics to support a comprehensive kinetic mechanism.

Non-targeted identification and semi-quantitation of emerging per- and polyfluoroalkyl substances (PFAS) in US rainwater.

High-resolution mass spectrometry was used to screen for emerging per- and polyfluorinated alkyl substances (PFAS) in precipitation samples collected in summer 2019 at seven sites in the United States. We previously quantified the concentration of ten PFAS in the rainwater samples using the method of isotopic dilution (Pike , 2021). Nine of these targeted analytes belonged to the U.

PFAS on atmospheric aerosol particles: a review.

Per- and polyfluoroalkyl substances (PFAS) are persistent organic pollutants of concern to human health. These synthetic chemicals are in widespread use for consumer products, firefighting foams, and industrial applications. They have been detected all over the globe, including at remote locations distant from any possible point sources.

Correlation Analysis of Perfluoroalkyl Substances in Regional U.S. Precipitation Events.

Per- and polyfluoroalkyl substances (PFAS) are transported in the atmosphere, leading to both wet and dry deposition to the surface. The concentrations of 15 PFAS were measured at six locations in the Ohio-Indiana region of the U.S.

Organic Surfactants Protect Dissolved Aerosol Components against Heterogeneous Oxidation.

Oxidative aging alters the composition of organic aerosols over time, in turn affecting the ability of aerosols to seed cloud formation and scatter solar radiation. Here we explore the heterogeneous photooxidation of model organic particles with and without a soluble surfactant coating. Tricarballylic acid (TCA), a proxy for α-pinene oxidation products, serves as a representative small organic solute.

Heterogeneous Chlorination of Squalene and Oleic Acid.

Washing with chlorine bleach leads to high mixing ratios of gas-phase HOCl. Using two methods that are sensitive to surface film composition-attenuated total reflection fourier transform infrared (ATR-FTIR) spectroscopy and direct analysis in real time mass spectrometry (DART-MS)-we present the first study of the chlorination chemistry that occurs when gaseous HOCl reacts with thin films of squalene and oleic acid. At mixing ratios of 600 ppbv, HOCl forms chlorohydrins by adding across carbon-carbon double bonds without breaking the carbon backbone.

Role of Aerosol Liquid Water in Secondary Organic Aerosol Formation from Volatile Organic Compounds.

A key mechanism for atmospheric secondary organic aerosol (SOA) formation occurs when oxidation products of volatile organic compounds condense onto pre-existing particles. Here, we examine effects of aerosol liquid water (ALW) on relative SOA yield and composition from α-pinene ozonolysis and the photooxidation of toluene and acetylene by OH. Reactions were conducted in a room-temperature flow tube under low-NO conditions in the presence of equivalent loadings of deliquesced (∼20 μg m ALW) or effloresced (∼0.

Microjets and coated wheels: versatile tools for exploring collisions and reactions at gas-liquid interfaces.

This tutorial review describes experimental aspects of two techniques for investigating collisions and reactions at the surfaces of liquids in vacuum. These gas-liquid scattering experiments provide insights into the dynamics of interfacial processes while minimizing interference from vapor-phase collisions. We begin with a historical survey and then compare attributes of the microjet and coated-wheel techniques, developed by Manfred Faubel and John Fenn, respectively, for studies of high- and low-vapor pressure liquids in vacuum.

Gas-Microjet Reactive Scattering: Collisions of HCl and DCl with Cool Salty Water.

Liquid microjets provide a powerful means to investigate reactions of gases with salty water in vacuum while minimizing gas-vapor collisions. We use this technique to explore the fate of gaseous HCl and DCl molecules impinging on 8 molal LiCl and LiBr solutions at 238 K. The experiments reveal that HCl or DCl evaporate infrequently if they become thermally accommodated at the surface of either solution.

Super-Maxwellian helium evaporation from pure and salty water.

Helium atoms evaporate from pure water and salty solutions in super-Maxwellian speed distributions, as observed experimentally and modeled theoretically. The experiments are performed by monitoring the velocities of dissolved He atoms that evaporate from microjets of pure water at 252 K and 4-8.5 molal LiCl and LiBr at 232-252 K.

Ballistic Evaporation and Solvation of Helium Atoms at the Surfaces of Protic and Hydrocarbon Liquids.

Atomic and molecular solutes evaporate and dissolve by traversing an atomically thin boundary separating liquid and gas. Most solutes spend only short times in this interfacial region, making them difficult to observe. Experiments that monitor the velocities of evaporating species, however, can capture their final interactions with surface solvent molecules.

Surfactant-promoted reactions of Cl2 and Br2 with Br- in glycerol.

Gas-liquid scattering experiments are used to explore reactions of gaseous Cl2 and Br2 with a 0.03 M solution of the surfactant tetrahexylammonium bromide (THABr) dissolved in glycerol. At thermal collision energies, 79 ± 2% of incident Cl2 molecules react with Br(-) to form Cl2Br(-) in the interfacial region.

Near-interfacial halogen atom exchange in collisions of Cl2 with 2.7 M NaBr-glycerol.

Gas-liquid scattering experiments are used to investigate reactions of Cl(2) with a 2.7 M NaBr-glycerol solution at 291 K. Only the single and double halogen exchange products, BrCl and Br(2), are observed to desorb from solution.