Research Watch: Mathyl chloride source - Environmental Science

Research Watch: Mathyl chloride source - Environmental Science...

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Research Watch

Air Detecting nitrate radicals. Cavity ring-down spectroscopy has been used to detect the nitrate radical N 0 3 in ambient room air that had been dosed with a precursor of the radical dinitrogen pentoxide, N 2 O s . (King, M. D., et al. "A New Method for the Atmospheric Detection of the Nitrate Radical (N0 3 )", Atmos. Environ. 2000, 34 (5), 685-688) Lead transport. Concentrations of lead in livers of willow grouse (Lagopus lagopus), black grouse [Tetrao tetrix), and hare [Lepus ttmidus) were determined in samples collected across Norway with the objective of elucidating the impact of long-range atmospheric transport on the lead exposure of the animals. (Kals, J. A., et al. "Lead Exposure of Small Herbivorous Vertebrates From Atmospheric Pollution", Environ. Pollut. 2000 107 (1), 21-29) Methyl chloride source. The authors report evidence of significant CH3C1 emissions from warm coastal land, particularly from tropical islands, based on a global monitoring study and spot measurements and suggest that this is why the distribution of CH3CI is uniform between the northern and southern hemispheres, despite their differences in ocean and land area. (Yokouchi, Y., et al. "A Strong Source of Methyl Chloride to the Atmosphere From Tropical Coastal Land" Nature 2000 403 (6767) 295-298) Passive sampling. This study addresses the growing interest in using passive sampling systems for quantifying ambient, gaseous air pollutant concentrations, particularly in remote and wilderness areas. (Krupa, S. V; Legge, A. H. "Passive Sampling of Ambient, Gaseous Air Pollutants: An Assessment From an Ecological Perspective", Environ. Pollut. 2000, 107 (1), 31-45)

PCDD/Fs in industrial boilers The potential for emissions of polychlorinated dibenzodioxin and dibenzofuran (PCDD/F) from industrial boilers that cofire hazardous waste is not well characterized. To address this issue, B. Gullett and co-workers sampled emissions from a fuel-oil fired firetube boiler cofired with 2,4-dichlorophenol or 1,2-dichlorobenzene and a copper naphthenate mixture. PCDD/F levels were significantly elevated when improved combustion conditions followed periods of flame wall-impingement and soot formation and deposition on the boiler tubes. Results indicate that boiler tube deposits became a sink and source for PCDD/F reactants and PCDD/F and led to continued formation and emissions long after waste cofiring ceased. The role of deposits in PCDD/F formation makes emissions dependent on current, as well as previous, firing conditions, resulting in uncertainty regarding prediction of emissions based solely on the type and rate of cofired hazardous waste. {Environ. Sci. Technoll ,his iisue ,p. 2069-2074)

Climate Amazon carbon. The annual flux of carbon from deforestation and abandonment of agricultural lands in the Brazilian Amazon was about 0.2 Pg yr"1 over the period 1989-1998 (1 Pg is 10+15 g), an estimate based on annual rates of deforestation and spatially detailed estimates of deforestation, regrowing forests, and biomass. (Houghton, R. A., et al. "Annual Fluxes of Carbon From Deforestation and Regrowth in the Brazilian Amazon", Nature 2000, 403 (6767) 301-304) Forest ecosystems. Assessing the long-term exchange of trace gases and energy between terrestrial ecosystems and the atmosphere is an important priority of current climate change research and makes significant this paper's data on simultaneous fluxes of carbon, water vapor, and pollutants over representative ecosystems. (Zeller, K. E; Nikolov, N. T. "Quantifying Simultaneous Fluxes of Ozone, Carbon Dioxide and Water Vapor Above a Subalpine Forest Ecosystem" Environ. Pollut. 2000 107 (1) 1-20) Marsh emissions. Results suggest mat even though marshes constitute less than 0.1% of the global surface area, they may produce roughly 10% of the


total fluxes of atmospheric CH3Br and CH3CI. (Rhew, R. C. "Natural Methyl Bromide and Methyl Chloride Emissions From Coastal Salt Marshes", Nature 2000, 403 (6767), 292-295) Natural oxidation processes. The authors identify a little-known terrestrial source of naturally occurring volatile halogenated organic compounds. In soils and sediments, halide ions can be alkylated during the oxidation of organic matter by an electron acceptor such as Fe(III); sunlight or microbial mediation are not required for these reactions. (Keppler, E, et al. "I Ialocarbons Produced by Natural Oxidation Processes During Degradation of Organic Matter", Nature 2000 403 (6767) 298-301) Carbon sinks. Both the 13C and the 0 2 data show significant interannual variability in carbon storage in the land biosphere and world oceans over the period 1991-1997. (Battle, L, M.; et al. "Global Carbon Sinks and Their Variability Inferred From Atmospheric 0 2 and 13C", Science 2000, 287 (5462), 2467-2470) Ozone depletion effects. In highlatitude regions, freshwater ecosystems at present located across vegetation gradients will experience significant shifts in underwater spec-