Halocarbon Production Research Articles

Halocarbon production and in vivo brominating activity of Eucheuma denticulatum

In vivo brominating activity by Eucheuma denticulatum was compared with its production of volatile halocarbons. The ability of the alga to brominate phenol red showed good correlation ( p< 0.05, r = 1.0) to the production of bromoform (CHBr 3) estimated by gas chromatography. The production of tetrabromophenol or bromoform was raised by exposing the algae to mechanical stress (in the form of cutting), increased light or addition of the herbicide DCMU, prior to the measurements. We suggest that the in vivo brominating activity of E. denticulatum can be used as a simple method to study the physiology of this alga. We also suggest that the activity of the brominating peroxidases is dependent on the intracellular concentration of H 2O 2, possibly produced by the Mehler reaction. Production of singlet oxygen and triplet chlorophyll by photo-oxidative damage may increase halocarbon release. The amount produced and the species of volatile halocarbons released are dependent on the conditions the algae are subjected to prior and during the experiment. Addition of NaCN or NaN 3 inhibited the brominating activity with 95 or 75% of control values.

Policy Analysis, Peer Reviewed: Potential Environmental Impacts of Future Halocarbon Emissions

An integrated analysis of future halocarbon emissions and their environmental impacts shows that strict global compliance is required if the Montreal Protocol is to accomplish the goal of eliminating the lower stratospheric ozone hole. This analysis is integrated in the sense that demographic, economic, and regulatory processes controlling future production were linked explicitly to the technological factors translating production into emissions and the environmental processes transforming emissions into environmental impacts. Given current models of halocarbon transformation and atmospheric response, this research suggests that if a small percentage of nations continues to expand production at modest rates, the ozone hole will not be eliminated. In addition, high growth rate assumptions for halocarbon production by noncompliance nations will result in significantly increased ozone depletion. This research also shows that the continued use of small amounts of ozone-depleting substances for essential uses and the failure to adequately replace all ozone-depleting substances can eliminate the possibility of returning the atmosphere to pre-ozone hole conditions. The global climate change potential of halocarbons is fairly small if growth rates for chlorofluorocarbon substitutes remain low. If growth rates return to precontrol levels, these substitutes could contribute significantly to global climate change. 41 refs., 3 figs., 3 tabs.

Global warming from chlorofluorocarbons and their alternatives: Time scales of chemistry and climate

The halocarbons (chloroflurocarbons, CFCs, and their replacement chemicals: the hydrochloroflurocarbons, HCFCs, and the hydrofluorocarbons, HFCs) are greenhouse gases. The atmospheric accumulation of these gases is expected to add to the global warming predicted for expected increases of CO 2, CH 4, N 2O, tropospheric ozone and H 2O. Over the next decades, production of CFCs is scheduled to be phased out, while emissions of their alternatives are expected to increase. A simple model is used to illustrate the methodology for determining the time variations of the radiative forcing and temperature changes attributable to the direct greenhouse effect from potential emissions of the halocarbons. Although there are uncertainties associated with the lifetimes of the greenhouse gases, CFCs and their substitutes, the future growth rates of these gases, and the parameters used to simulate the response of the Earth-climate system, the method serves to illustrate an important aspect of the greenhouse warming issue beyond what is provided by the various greenhouse warming indices. Our results show that for likely substitution scenarios, the warming due to halocarbons will correspond to 4–10% of the total expected greenhouse warming at the year 2100. However, uncontrolled growth of the substitutes could result in an eight-fold increase in halocarbon production and a doubling of the halocarbon contribution by 2100.

Carotenoids and the retina — An overview

Eukaryotic phytoplankton such as diatoms and prymnesiophytes produce biogenic halocarbons in the ocean that serve as important sources of chlorine and bromine to the atmosphere, but the role of cyanobacteria in halocarbon production is not well established. We studied distributions of chloroform (CHCl3), carbon tetrachloride (CCl4), methylene bromide (CH2Br2) and bromoform (CHBr3) in relation to phytoplankton composition, determined from pigment analysis complemented by microscopic examination, for one month in coastal waters of the eastern Arabian that experienced a Trichodesmium bloom that typically occurs during the Spring Intermonsoon season. High concentrations of zeaxanthin (23 μg l−1), alpha beta betacarotene (6 μg l−1) and chlorophyll a (67 μg l−1) were found within the bloom whereas the marker pigment concentrations were low outside the bloom. CHCl3 and CCl4 occurred in relatively high concentrations in surface waters whereas CH2Br2 and CHBr3 were restricted to the subsurface layer. Chlorinated halocarbons were positively inter-correlated and with CHBr3. The observed spatial and temporal trends in brominated compounds appear to be related to the abundance of Trichodesmium although correlations between concentrations of brominated compounds with various marker pigments were poor and statistically non-significant. The results support the existence of multiple sources and sinks of halogenated compounds, which might obscure the relationship between halocarbons and phytoplankton composition.

Stratospheric ozone depletion and future levels of atmospheric chlorine and bromine

The rise in atmospheric chlorine levels caused by the emission of chlorofluorocarbons and other halocarbons is thought to be the main cause of the appearance of the Antarctic ozone 'hole' in the late 1970s, and the more modest ozone depletion observed over parts of the Northern Hemisphere. Atmospheric bromine, also associated with halocarbon emissions, is believed to contribute to ozone depletion. Over the next decade, further increases in these compounds are inevitable. Model calculations show that by the end of the next century, atmospheric chlorine and bromine levels may return to those prevalent before the onset of the ozone hole, but only if more stringent regulations are applied to halocarbon production than those currently proposed.

Volatile halocarbon production from the chlorination of marine algal byproducts, including D-mannitol

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTVolatile halocarbon production from the chlorination of marine algal byproducts, including D-mannitolAllan M. Crane, Peter. Kovacic, and Eric D. KovacicCite this: Environ. Sci. Technol. 1980, 14, 11, 1371–1374Publication Date (Print):November 1, 1980Publication History Published online1 May 2002Published inissue 1 November 1980https://doi.org/10.1021/es60171a005RIGHTS & PERMISSIONSArticle Views74Altmetric-Citations8LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (525 KB) Get e-Alerts Get e-Alerts