Oxide Fluxes (oxide + flux)

Distribution by Scientific Domains

Kinds of Oxide Fluxes

  • nitrous oxide flux

  • Selected Abstracts

    Assessment of methane and nitrous oxide flux from mangroves along Eastern coast of India

    GEOFLUIDS (ELECTRONIC), Issue 4 2008
    Abstract Mangroves are considered to be a minor source of greenhouse gases (CH4 and N2O) in pristine environmental condition. However, estimates of efflux suggest that anthropogenic activities have led to a pronounced increase in greenhouse gas emission. Along the east coast of India, mangroves vary substantially in area, physiography and freshwater input, which ultimately modify the biogeochemical processes operating within this ecosystem. An attempt has here been made to elucidate the existing variation and role of climatic variability on the emission of greenhouse gases from mangroves. The flux estimates of CH4 and N2O have been quantified from Bhitarkanika mangrove accounting for spatial and temporal (seasonal) variation. The annual rates were estimated to be 0.096 × 10 9 g CH4 year,1 and 5.8 × 103g N2O year,1 for the whole mangrove area of the east coast of India. Upscaling these estimates yield an annual emission of 1.95 × 10 12 g CH4 year,1 and 1.1 × 10 11 g N2O year,1 from worldwide mangrove areas. The influence of elevated nutrient inputs through anthropogenic influence enhances the emission of greenhouse gas. The present article shows the need to develop an inventory on greenhouse gas flux from mangrove ecosystem. [source]

    Zirconia,Silica,Carbon Coatings on Ceramic Fibers

    Emmanuel E. Boakye
    Precursors for zircon,carbon mixtures were made to coat fibers for ceramic-matrix composites. Precursors were characterized using XRD, TGA, and DTA. Zircon formed from vanadium- or lithium-doped precursors after heat treatments at ,900°C in air, but it did not form at 1200°,1400°C in argon when large amounts of carbon were added. Some precursors were used to coat NextelÔ 720 and Hi-NicalonÔ fibers. The coatings were characterized using SEM and TEM, and coated-fiber tensile strengths were measured. Although zircon formed in powders, only tetragonal-zirconia,silica mixed phases formed in fiber coatings at 1200°C in air. Loss of vanadium oxide flux to the fibers may have caused the lack of conversion to zircon. The strengths of the coated fibers were severely degraded after heat treatment at ,1000°C in air, but not in argon. The coated fibers were compared with zirconia,carbon-coated fibers made using similar methods. Mechanisms for fiber strength degradation are discussed. [source]

    Methane and nitrous oxide fluxes from a farmed Swedish Histosol

    Å. Kasimir Klemedtsson
    Summary Fluxes of the greenhouse gases methane (CH4) and nitrous oxide (N2O) from histosolic soils (which account for approximately 10% of Swedish agricultural soils) supporting grassley and barley production in Sweden were measured over 3 years using static chambers. Emissions varied both over area and time. Methane was both produced and oxidized in the soil: fluxes were small, with an average emission of 0.12 g CH4 m,2 year,1 at the grassley site and net uptake of ,0.01 g CH4 m,2 year,1 at the barley field. Methane emission was related to soil water, with more emission when wet. Nitrous oxide emissions varied, with peaks of emission after soil cultivation, ploughing and harrowing. On average, the grassley and barley field had emissions of 0.20 and 1.51 g N2O m,2 year,1, respectively. We found no correlation between N2O and soil factors, but the greatest N2O emission was associated with the driest areas, with < 60% average water-filled pore space. We suggest that the best management option to mitigate emissions is to keep the soil moderately wet with permanent grass production, which restricts N2O emissions whilst minimizing those of CH4. [source]

    Methane and nitrous oxide fluxes of soils in pure and mixed stands of European beech and Norway spruce

    W. Borken
    Summary Tree species can affect the sink and source strength of soils for atmospheric methane and nitrous oxide. Here we report soil methane (CH4) and nitrous oxide (N2O) fluxes of adjacent pure and mixed stands of beech and spruce at Solling, Germany. Mean CH4 uptake rates ranged between 18 and 48 ,g C m,2 hour,1 during 2.5 years and were about twice as great in both mixed and the pure beech stand as in the pure spruce stand. CH4 uptake was negatively correlated with the dry mass of the O horizon, suggesting that this diminishes the transport of atmospheric CH4 into the mineral soil. Mean N2O emission was rather small, ranging between 6 and 16 ,g N m,2 hour,1 in all stands. Forest type had a significant effect on N2O emission only in one mixed stand during the growing season. We removed the O horizon in additional plots to study its effect on gas fluxes over 1.5 years, but N2O emissions were not altered by this treatment. Surprisingly, CH4 uptake decreased in both mixed and the pure beech stands following the removal of the O horizon. The decrease in CH4 uptake coincided with an increase in the soil moisture content of the mineral soil. Hence, O horizons may maintain the gas diffusivity within the mineral soil by storing water which cannot penetrate into the mineral soil after rainfall. Our results indicate that conversion of beech forests to beech,spruce and pure spruce forests could decrease soil CH4 uptake, while the long-term effect on N2O emissions is expected to be rather small. [source]

    Initial cultivation of a temperate-region soil immediately accelerates aggregate turnover and CO2 and N2O fluxes

    Abstract The immediate effects of tillage on protected soil C and N pools and on trace gas emissions from soils at precultivation levels of native C remain largely unknown. We measured the response to cultivation of CO2 and N2O emissions and associated environmental factors in a previously uncultivated U.S. Midwest Alfisol with C concentrations that were indistinguishable from those in adjacent late successional forests on the same soil type (3.2%). Within 2 days of initial cultivation in 2002, tillage significantly (P=0.001, n=4) increased CO2 fluxes from 91 to 196 mg CO2 -C m,2 h,1 and within the first 30 days higher fluxes because of cultivation were responsible for losses of 85 g CO2 -C m,2. Additional daily C losses were sustained during a second and third year of cultivation of the same plots at rates of 1.9 and 1.0 g C m,2 day,1, respectively. Associated with the CO2 responses were increased soil temperature, substantially reduced soil aggregate size (mean weight diameter decreased 35% within 60 days), and a reduction in the proportion of intraaggregate, physically protected light fraction organic matter. Nitrous oxide fluxes in cultivated plots increased 7.7-fold in 2002, 3.1-fold in 2003, and 6.7-fold in 2004 and were associated with increased soil NO3, concentrations, which approached 15 ,g N g,1. Decreased plant N uptake immediately after tillage, plus increased mineralization rates and fivefold greater nitrifier enzyme activity, likely contributed to increased NO3, concentrations. Our results demonstrate that initial cultivation of a soil at precultivation levels of native soil C immediately destabilizes physical and microbial processes related to C and N retention in soils and accelerates trace gas fluxes. Policies designed to promote long-term C sequestration may thus need to protect soils from even occasional cultivation in order to preserve sequestered C. [source]