Enteric methane emission rates determined by the SF6 tracer technique: Temporal patterns and averaging periods - ScienceDirect
Export JavaScript is disabled on your browser. Please enable JavaScript to use all the features on this page., 23 June 2011, Pages 183-191Author links open overlay panelShow moreAbstractThe sulphur hexafluoride (SF6) tracer technique has been widely applied to determine CH4 emission rates by ruminants since its development in the mid-1990s. It remains the only viable method for determining emission rates from individual grazing animals. Essential parts of the method for each participating animal are pre-insertion into the rumen of a source of SF6 with known release rate and breath sample collections near the nose and mouth for CH4 and SF6 analysis. Breath samples are accumulated over an ‘averaging period’ of usually 24 h to yield estimates of CH4 emissions. As a tracer, SF6 is biologically inert and has a very low detection limit (i.e., 10-12), enabling release rates of a few tens of μl/h to be sustained for many months by an initial SF6 charge of ~1 g. Any departure from a uniform SF6 collection rate, such as through SF6 interactions in the digestive tract, could introduce variability into the inferred CH4 emission rate, which has the potential to explain reports of higher variability in CH4 emission rates estimated with this technique compared with whole animal chamber techniques. Our study examined SF6 and CH4 excretion rates for their variability using a novel automated gas chromatography system that isolated and analysed 20 min breath samples collected successively for 6 d from each of 9 housed sheep. We found that that SF6 was not excreted into the breath stream at a uniform rate, but its daily pattern of excretion was strongly correlated with that of CH4, suggesting that some SF6 is retained within the digestive tract and later ventilated with eructated gases following feeding. Methane emission rates can be estimated for different averaging periods through different combinations of the 20 min data. Methane emission rate estimates for each sheep are independent of averaging period between 3 h and 6 d, although inter-period variability is highest for averaging periods less than 1 d. Improved understanding of the SF6 tracer technique supports it as a reliable unbiased estimator of enteric CH4 emission rate in ruminants.This paper is part of the special issue entitled: Greenhouse Gases in Animal Agriculture – Finding a Balance between Food and Emissions, Guest Edited by T.A. McAllister, Section Guest E K.A. Beauchemin, X. Hao, S. McGinn and Editor for Animal Feed Science and Technology, P.H. Robinson.AbbreviationsECDelectron capture detectorFIDflame ionisation detectorGCgas chromatographyKeywordsMethaneRuminant livestockSF6 tracer techniqueIntensive breath samplingAveraging periodCheck if you have access through your login credentials or your institution.ororRecommended articlesCiting articles (0)Meteorological Influences on Trace Gas Transport along the North Atlantic Coast
Title:Meteorological Influences on Trace Gas Transport along the North Atlantic Coast during ICARTT 2004
Authors:; ; ;
Publication:Atmosphere, vol. 5, issue 4, pp. 973-1001
Publication Date:12/2014
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arXiv e-printsModeling the Effects of Zinc and Orthophosphate on the Growth of Phytoplankton f
Title:Modeling the Effects of Zinc and Orthophosphate on the Growth of Phytoplankton from Coeur d'Alene Lake, ID
Authors:; ;
Affiliation:AA(U.S. Geological Survey, 345 Middlefield Road, MS 439, Menlo Park, CA 94025 United States ), AB(U.S. Geological Survey, 345 Middlefield Road, MS 439, Menlo Park, CA 94025 United States ), AC(U.S. Geological Survey, 345 Middlefield Road, MS 439, Menlo Park, CA 94025 United States )
Publication:American Geophysical Union, Fall Meeting 2006, abstract #H23B-1495
Publication Date:12/2006
Keywords:0470 Nutrients and nutrient cycling (), 0489 Trace element cycling (4875), 0496 Water quality, 1871 Surface water quality, 1880 Water management (6334)
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Coeur d'Alene Lake, a transitional mesotrophic/oligotrophic system,
continues to receive metal loading from historic mining operations now
associated with the Bunker Hill Superfund Site, the largest Superfund
Site in the country.
Two dominant algal species, Chlorella minutissima
and Asterionella formosa, within the longitudinal dissolved-zinc
concentration gradient of Coeur d'Alene Lake were isolated and cultured
in chemically defined media to examine and model the growth response to
a range of dissolved orthophosphate and zinc-ion activities
representative of the region within and up gradient of the Coeur d'Alene
River inlet to the Lake.
Although an essential micronutrient, elevated
concentrations of uncomplexed zinc adversely affect algal metabolism of
phosphorus, the limiting nutrient in the lake.
Ancillary chemical
characterizations of the water column as well as biological
characterizations of the benthos were also done to facilitate
interpretation of the algal-culturing results and for comparison with
similar characterizations performed a decade before.
The water column
and benthos of Coeur d'Alene Lake were sampled in August 2001, June 2004
and June 2005 to provide the biological characterization in terms of
phytoplankton community composition, benthic macroinvertebrate community
composition and benthic chlorophyll concentrations, as well as chemical
characterizations at six sites (three depths per site) within the lake.
This study provides information in support of developing process-
interdependent solute-transport models for the watershed (that is,
models integrating physical, geochemical and biological processes), and
hence in support of subsequent evaluation of remediation or
load-allocation strategies.
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