نتایج جستجو برای: bromine
تعداد نتایج: 2325 فیلتر نتایج به سال:
Abstract Unlike bromine, the effect of iodine chemistry on Arctic surface ozone budget is poorly constrained. We present ship-based measurements halogen oxides in high boundary layer from sunlit period March to October 2020 and show that enhances springtime tropospheric depletion. find chemical reactions between are second highest contributor loss over study period, after photolysis-initiated a...
We develop a performance model for a polymer electrolyte membrane based regenerative hydrogen-bromine fuel cell (rHBFC). The model includes four voltage loss mechanisms: ohmic loss through the membrane, hydrogen electrode activation, bromine electrode activation, and bromine electrode mass transport. We explore a large parameter space by looking at the dependences of each of these losses as a f...
In the polar tropospheric boundary layer, reactive halogen species (RHS) are responsible for ozone depletion as well as the oxidation of elemental mercury and dimethyl sulphide. After polar sunrise, air masses enriched in reactive bromine cover areas of several million square kilometers. Still, the source and release mechanisms of halogens are not completely understood. We report measurements o...
During springtime in the polar regions, unique photochemistry converts inert halide salt ions (e.g. Br) into reactive halogen species (e.g. Br atoms and BrO) that deplete ozone in the boundary layer to near zero levels. Since their discovery in the late 1980s, research on ozone depletion events (ODEs) has made great advances; however many key processes remain poorly understood. In this article ...
In the official method for determination of total bromine in fruit and grain foods, bromine is derivatized with 3-pentanone for GC analysis. Co-existing substances sometimes interfere with measurement of the derivative, though the method is highly selective. In this study, the notification method was modified to reduce impurity peaks by applying 3-hexanone. Samples were alkalized and reduced to...
Occasionally children are the victims of mass poisoning from an environmental contaminant that occurs due to an unexpected common point source of exposure. In many cases the contaminant is a widely used chemical generally considered to be safe. In the following case, members of a sports team visiting a community for an athletic event were exposed to chemicals while staying at a local motel. Bro...
Iodine is an essential trace element for all mammals and may also influence climate through new aerosol formation. Atmospheric bromine cycling is also important due to its well-known ozone depletion capabilities. Despite precipitation being the ultimate source of iodine in the terrestrial environment, the processes effecting its distribution, speciation and transport are relatively unknown. The...
Dehydrohalogenation of 5,6-dihalogen-1,3-dioxepanes II with KOH/MeOH or NaOCH3/MeOH under controlled reaction conditions gave mainly 5-halogen-4,7-dihydro-1,3-dioxepines III. Further substitution of vinylic-bromine in III whit KO-t-Bu/tert-BuOH or KOH/MeOH led to corresponding 5-substituted-4,7-dihydro-1 ,3-dioxepines some of which underwent spontaneous isomerization to 6,7-dihydro-1,3-dioxepin...
We report transient grating measurements carried out on single crystals of bromine clathrate hydrates and on bromine dissolved in water. In all cases, excitation into the B-state of Br2 leads to prompt predissociation, followed by cage-induced recombination on the A/A' electronic surfaces. In liquid water, the vibrationally incoherent recombinant population peaks at t=1 ps and decays with a tim...
Haloacetamides (HAcAms) are an emerging class of nitrogenous disinfection by-products (N-DBPs) of health concern. However, there are very limited data on the formation and speciation of the nine bromine- and chlorine-containing haloacetamides (HAcAm9). In the study, their formation and speciation during chlor(am)ination were investigated for a group of waters with a range of specific ultraviole...
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