Bromoform

Abstract: Current estimates of annual bromoform production by temperate marine algae underestimate, by at least an order of magnitude, the flux required to sustain atmospheric concentrations. In the light of recent evidence of the potential of bromoform to deplete upper-tropospheric/lower-stratospheric ozone, such a substantial discrepancy in global emission rates is of considerable concern. Here we present new information on air and seawater CHBr3, CH2Br2, and CHBr2Cl concentrations in the coastal east Atlantic and review previous data from widespread locations which suggest that concentrations and ratios of reactive organobromines are consistent with marine macroalgal emissions. Detailed reviews of algal halocarbon emissions and biomass estimates imply that macroalgae produce around 70% of the world's bromoform, rather than only ∼20% as previously thought, and that the underestimation was most likely caused by over conservative biomass estimates. Our total global source strength estimate of 2.2×1011 g CHBr3 yr−1 agrees well with recent calculations derived from atmospheric data. Given the dominant role of macroalgae in producing bromoform, the effect of changing climate and environment on seaweed populations and consequent effect on biogenic bromine emissions should be investigated.

Abstract: The reductive dehalogenation of hexachloroethane (C 2 Cl 6 ), carbon tetrachloride (CCl 4 ), and bromoform (CHBr 3 ) was examined at 50 o C in aqueous solutions containing either (1) 500 μM of 2,6-anthrahydroquinone disulfonate (AHQDS), (2) 250 μM Fe 2+ , or (3) 250 μM HS - . The pH ranged from 4.5 to 11.5 for AHQDS solutions and was 7.2 in the Fe 2+ solutions and 7.8 in the HS - solutions. The observed disappearance of C 2 Cl 6 in the presence of AHQDS was pseudo-first-order and fit k' CCl4 =k 0 [A(OH) 2 ]+ k 1 [A(OH)O - ]+k 2 [A(O) 2 2- ] where A(OH) 2 , A(OH)O - , and A(O) 2 2- represent the concentrations of the three forms of the AHQDS in solution

Abstract: Thermodynamic interactions in binary mixtures of bromoform with hydrocarbons have been studied in terms of a number of excess functions from the measured mixture properties such as density, viscosity, sound velocity, refractive index, and dielectric constant. Results of excess molar volume, apparent excess molar viscosity, and excess molar Gibbs free energy of activation of flow have been discussed in terms of destruction or creation of order and/or induced conformational changes in liquid n-alkanes in the presence of a nearly spherical bromoform molecule

Abstract: DESTRUCTION of surface ozone in the Arctic environment during the spring is thought to be caused by photochemical reactions involving bromine compounds1. Berg et al.2 reported a pulse of bromine particles and gases in the Arctic lower atmosphere in spring, which may be responsible for this surface ozone destruction and for which biogenic sources have been hypothesized1–3. Here we report laboratory and in situ measurements which indicate that Arctic ice microalgae emit significant quantities of bromoform (CHBr3), which may be converted photochemically into active forms of bromine. Our estimates of total annual bromoform release indicate that polar ice algae might contribute globally significant amounts of organic bromine compounds, comparable with anthropogenic and macrophyte sources.