"Halocarbon" from_date:2012

Rapid Release of Halocarbons from Saline Water by Iron-Based Photochemistry. Methyl halides play important roles in stratospheric ozone depletion, but their formation mechanisms are not well defined. This study demonstrated that iron-based photochemistry significantly enhanced alkyl halide production by promoting the reaction of the representative monomer of lignin with halide ions in saline , which accounts for a portion of the unidentified sources of halocarbons in the ocean.

Halocarbon emissions by selected tropical seaweeds: species-specific and compound-specific responses under changing pH Five tropical seaweeds, (Doty) Doty ex P.C. Silva, Hauck, Sonder ex J. Agardh (syn. (Turner) C. Agardh), J. Agardh and (J. Agardh) Kützing, were incubated in seawater of pH 8.0, 7.8 (ambient), 7.6, 7.4 and 7.2, to study the effects of changing seawater pH on halocarbon emissions. Eight halocarbon species known to be emitted by seaweeds were investigated: bromoform (CHBr), dibro-momethane (CHBr), iodomethane (CHI), diiodomethane (CHI), bromoiodomethane (CHBrI), bromochlorometh-ane (CHBrCl), bromodichloromethane (CHBrCl), and dibro-mochloromethane (CHBrCl). These very short-lived halocarbon gases are believed to contribute to stratospheric halogen concentrations

First observations of the fourth generation synthetic halocarbons HFC-1234yf, HFC-1234ze(E), and HCFC-1233zd(E) in the atmosphere. Halogenated alkenes are a class of anthropogenic substances, which replace ozone-depleting substances and long-lived greenhouse gases in the foam-blowing, refrigeration, and solvent sectors. We report the first multiyear atmospheric measurements

Exposure to Potentially Toxic Hydrocarbons and Halocarbons Released From the Dialyzer and Tubing Set During Hemodialysis. Although much is known about the effect of chronic kidney failure and dialysis on the composition of solutes in plasma, little is known about their impact on the composition of gaseous compounds in exhaled breath. This study was designed to explore the effect of uremia -matched healthy individuals. Predictors include the dialyzers, tubing set, dialysate, and water supplies before, during, and after dialysis. Changes in the composition of exhaled breath. A 5-column/detector gas chromatography system was used to measure hydrocarbon, halocarbon, oxygenate, and alkyl nitrate compounds. Concentrations of 14 hydrocarbons and halocarbons in patients' breath rapidly increased

Degradation of Chloroform by Zerovalent Iron: Effects of Mechanochemical Sulfidation and Nitridation on the Kinetics and Mechanism. Chloroform (CF) is a widely used chemical reagent and disinfectant and a probable human carcinogen. The extensive literature on halocarbon reduction with zerovalent iron (ZVI) shows that transformation of CF is slow, even with nano, bimetallic, sulfidated, and other

First Atmospheric Measurements and Emission Estimates of HFO-1336mzz(Z). For the past few years, short-lived unsaturated halocarbons have been marketed as environmentally friendly replacements for long-lived halogenated greenhouse gases and ozone-depleting substances. The phase-in of unsaturated halocarbons for various applications, such as refrigeration and foam blowing, can be tracked of new unsaturated halocarbons in the atmosphere is crucial since long-term effects of their degradation products are still debated. Furthermore, the production of HFOs involves climate-active substances, which may leak to the atmosphere─in the case of HFO-1336mzz(), for example, the ozone-depleting CFC-113a (CFCCl).

Will Climate Change Influence Production and Environmental Pathways of Halogenated Natural Products? Thousands of halogenated natural products (HNPs) pervade the terrestrial and marine environment. HNPs are generated by biotic and abiotic processes and range in complexity from low molecular mass natural halocarbons (nHCs, mostly halomethanes and haloethanes) to compounds of higher molecular mass

growth rates were estimated to be 8.36, 4.10, and 0.71 ppt year for HCFC-22, HFC-125, and HFC-152a, respectively. The CPT measurements were combined with an inverse model to investigate emissions from SWSA. For all three halocarbons, Cape Town was found to be the dominant source within SWSA. These estimates were extrapolated, based on population statistics, to estimate emissions for the whole of South Africa. We estimate South Africa's 2017 emissions to be 3.0 (1.6-4.4), 0.8 (0.5-1.2), and 1.1 (0.6-1.6) Gg year for HCFC-22, HFC-125, and HFC-152a, respectively. For all three halocarbons, South Africa's contribution to global emissions is small (<2.5%), but future monitoring is needed to ensure South Africa's compliance with regulation set out by the Montreal Protocol and its Amendments.

The production of high efficiency Ziegler–Natta catalyst with dual active sites nature using cyclohexyl chloride as promoter with super activity and produced superior polyethylene with controllable molecular weight distribution In the previous studies, the several halocarbons (HC) were tested as promoters for a Ti-based Ziegler-Natta (ZN) catalyst at different polymerization conditions and hydrogen responsibility ratio of the catalyst increase up to 125 and 55% respectively. The acceptable growth of polymer powder up to 46%, lower flow rate ratio (FRR) up to 19% and decrease of wax amount up to 12%, completed the promotion results. Furthermore, in the next part of this study and as key note, a little dose of halocarbon was used in the catalyst preparation to produce the special catalysts

dispersion in culture-medium for studies and halocarbons (PRESAGE chemical compositions). PRESAGE dosimeters were scanned with spectrophotometer to determine the radiation dose enhancement. Clonogenic and cell viability assays were employed to determine cells survival curves from which the dose enhancement levels "radiosensitisation" are deduced. Comparable levels of radiosensitisation were observed

Bromomethane Contamination in the Cathode of Proton Exchange Membrane Fuel Cells The effects of bromomethane (BrCH), an airborne contaminant, on the performance of a single PEMFC are compared with that of another halocarbon, chlorobenzene. Under a constant current of 1 A cm and at 45 °C, 20 ppm bromomethane causes approximately 30% cell voltage loss in approximately 30 h, as opposed to much more

of reducing all the 2011 greenhouse gases from Australia or halocarbon ozone-depleting substances from China. Adipic acid production, the major industrial emission source, contributes nearly 80% of the industrial N2O emissions, and represents about 96.2% of the industrial mitigation potential. However, the mitigation will not happen without implementing effective policies and regulatory programs.

on halocarbon adsorption energies may explain pH effects on dechlorination rates. Adsorption energies for TCE and PCE were calculated via molecular mechanics simulations using the Universal force field and a self-consistent reaction field charge equilibration scheme. A range in solution pH values was simulated by varying the amount of atomic hydrogen adsorbed on the iron. The potential energies associated TCE and PCE complexes were dominated by electrostatic interactions, and complex formation with the surface was found to result in significant electron transfer from the iron to the adsorbed halocarbons. Adsorbed atomic hydrogen was found to lower the energies of TCE complexes more than those for PCE. Attractions between atomic hydrogen and iron atoms were more favorable when TCE versus PCE was adsorbed

burst after sunrise. BrCN acts as a short-term signal, leading to daily "cleaning" events around the algae. We show that allelopathic effects are H(2)O(2) dependent and link BrCN production to haloperoxidase activity. This strategy is a highly effective means of biofilm control and may provide an explanation for the poorly understood role of volatile halocarbons from marine algae, which contribute significantly to the atmospheric halocarbon budget.

Stratospheric ozone depletion due to nitrous oxide: influences of other gases The effects of anthropogenic emissions of nitrous oxide (N(2)O), carbon dioxide (CO(2)), methane (CH(4)) and the halocarbons on stratospheric ozone (O(3)) over the twentieth and twenty-first centuries are isolated using a chemical model of the stratosphere. The future evolution of ozone will depend on each of these gases, with N(2)O and CO(2) probably playing the dominant roles as halocarbons return towards pre-industrial levels. There are nonlinear interactions between these gases that preclude unambiguously separating their effect on ozone. For example, the CH(4) increase during the twentieth century reduced the ozone losses owing to halocarbon increases, and the N(2)O chemical destruction of O(3) is buffered

European emissions of halogenated greenhouse gases inferred from atmospheric measurements. European emissions of nine representative halocarbons (CFC-11, CFC-12, Halon 1211, HCFC-141b, HCFC-142b, HCFC-22, HFC-125, HFC-134a, HFC-152a) are derived for the year 2009 by combining long-term observations in Switzerland, Italy, and Ireland with campaign measurements from Hungary. For the first time , halocarbon emissions over Eastern Europe are assessed by top-down methods, and these results are compared to Western European emissions. The employed inversion method builds on least-squares optimization linking atmospheric observations with calculations from the Lagrangian particle dispersion model FLEXPART. The aggregated halocarbon emissions over the study area are estimated at 125 (106-150) Tg of CO(2

haloalkanes (also known as halogenoalkanes or alkyl halides) are alkanes containing one or more halogen substituents.[1] They are a subset of the general class of halocarbons, although the distinction is not often made. Haloalkanes are widely used commercially. They are used as flame retardants, fire extinguishants, refrigerants, propellants, solvents, and pharmaceuticals. Subsequent to the widespread use in commerce, many halocarbons have also been shown to be serious pollutants and toxins. For example, the chlorofluorocarbons have been shown to lead to ozone depletion. Methyl bromide is a controversial fumigant. Only haloalkanes that contain chlorine, bromine, and iodine are a threat to the ozone layer, but fluorinated volatile haloalkanes in theory may have activity as greenhouse gases. Methyl iodide

to the Montreal Protocol[32] due to their very high Global Warming Potential and the recognition of halocarbon contributions to climate change.[33]On September 21, 2007, approximately 200 countries agreed to accelerate the elimination of hydrochlorofluorocarbons entirely by 2020 in a United Nations-sponsored Montreal summit. Developing nations were given until 2030. Many nations, such as the United States

/96GL01258.{{cite journal}}: CS1 maint: uses authors parameter (link) 23. ^ Walker, S. J.; Weiss R. F. & Salameh P. K. (2000). "Reconstructed histories of the annual mean atmospheric mole fractions for the halocarbons CFC-11, CFC-12, CFC-113 and carbon tetrachloride". Journal of Geophysical Research. 105 (C6): 14285–96. Bibcode:2000JGR...10514285W. doi:10.1029/1999JC900273. 24. ^ The Atlas of Climate