CH4and N2O Research Articles

Effects of soil water status on the spatial variation of carbon dioxide, methane and nitrous oxide fluxes in tropical rain-forest soils in Peninsular Malaysia

Abstract:To assess the effects of soil water status on the spatial variation in soil carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) fluxes, we examined these gas fluxes and environmental factors in a tropical rain forest in Peninsular Malaysia. Measurements of soil CO2, CH4and N2O fluxes were taken ten, nine, and seven times, respectively over 30 mo at 15 or 39 sampling point within 2-ha plot. Mean (± SE) value of spatially averaged CO2flux was 4.70 ± 0.19 μmol CO2m−2s−1and observed spatial variation in CO2flux was negatively related to the volumetric soil water content (VSWC) during the dry period. Over the wet period, extremely high CO2emissions were positively correlated with VSWC at some locations, suggesting that no spatial structure of CO2flux was because of such hot-spot CO2emissions. Flux of CH4was usually negative with little variation, with a mean value of –0.49 ± 0.15 mg CH4m−2d−1, resulting in the soil at our study site functioning as a CH4sink. Spatial variation in CH4flux was positively related to the VSWC throughout the entire study period (dry and wet). Some CH4hot spots were observed during dry periods, probably due to the presence of termites. Mean value of spatially averaged N2O flux was 98.9 ± 40.7 μg N m−2h−1and N2O flux increased markedly during the wet period. Spatially, N2O flux was positively related to both the VSWC and the soil N concentration and was higher in wet and anaerobic soils. These findings suggest that denitrification is a major contributor to high soil N2O fluxes. Additionally, analysis by adjusting confounding effects of time, location and interaction between time and location in mixed models, VSWC has a negative effect on CO2flux and positive effects on CH4and N2O fluxes. We found that soil water status was related temporally to rainfall and controlled greenhouse gas (GHG) fluxes from the soil at the study site via several biogeochemical processes, including gas diffusion and soil redox conditions. Our results also suggest that considering the biological effects such as decomposer activities may help to explain the complex temporal and spatial patterns in CO2and CH4fluxes.

A Study on Methane and Nitrous Oxide Emissions Characteristics from Anthracite Circulating Fluidized Bed Power Plant in Korea

In order to tackle climate change effectively, the greenhouse gas emissions produced in Korea should be assessed precisely. To do so, the nation needs to accumulate country-specific data reflecting the specific circumstances surrounding Korea's emissions. This paper analyzed element contents of domestic anthracite, calorific value, and concentration of methane (CH4) and nitrous oxide (N2O) in the exhaust gases from circulating fluidized bed plant. The findings showed the concentration of CH4 and N2O in the flue gas to be 1.85 and 3.25 ppm, respectively, and emission factors were 0.486 and 2.198 kg/TJ, respectively. The CH4 emission factor in this paper was 52% lower than default emission factor presented by the IPCC. The N2O emission factor was estimated to be 46% higher than default emission factor presented by the IPCC. This discrepancy can be attributable to the different methods and conditions of combustion because the default emission factors suggested by IPCC take only fuel characteristics into consideration without combustion technologies. Therefore, Korea needs to facilitate research on a legion of fuel and energy consumption facilities to develop country-specific emission factors so that the nation can have a competitive edge in the international climate change convention in the years to come.

Development of Methane and Nitrous Oxide Emission Factors for the Biomass Fired Circulating Fluidized Bed Combustion Power Plant

This study makes use of this distinction to analyze the exhaust gas concentration and fuel of the circulating fluidized bed (CFB) boiler that mainly uses wood biomass, and to develop the emission factors of Methane (CH4), Nitrous oxide (N2O). The fuels used as energy sources in the subject working sites are Wood Chip Fuel (WCF), RDF and Refused Plastic Fuel (RPF) of which heating values are 11.9 TJ/Gg, 17.1 TJ/Gg, and 31.2 TJ/Gg, respectively. The average concentrations of CH4 and N2O were measured to be 2.78 ppm and 7.68 ppm, respectively. The analyzed values and data collected from the field survey were used to calculate the emission factor of CH4 and N2O exhausted from the CFB boiler. As a result, the emission factors of CH4 and N2O are 1.4 kg/TJ (0.9–1.9 kg/TJ) and 4.0 kg/TJ (2.9–5.3 kg/TJ) within a 95% confidence interval. Biomass combined with the combustion technology for the CFB boiler proved to be more effective in reducing the N2O emission, compared to the emission factor of the CFB boiler using fossil fuel.

Tillage and Fertilizer Management Effects on Soil-Atmospheric Exchanges of Methane and Nitrous Oxide in a Corn Production System

Land application of poultry litter (PL) presents an opportunity to improve soil productivity and disposal of poultry waste. We investigated methane (CH4) and nitrous oxide (N2O) emissions from agricultural soil receiving PL and ammonium nitrate (AN) fertilizers using surface (SA), soil incorporation (SI), and subsurface band (BA) application methods in conventional (CT) and no-tillage (NT) systems on a Decatur silt loam soil in North Alabama. Plots under CT and NT were sinks of CH4in spring, summer, and fall. In winter, the plots had net emissions of 3.32 and 4.24 g CH4ha-1day-1in CT and NT systems, respectively. Plots which received AN were net emitters of CH4and N2O, whereas plots which received PL were net sinks of CH4. Plots which received PL using SA or SI methods were net emitters of N2O, whereas under PL using BA application, the plots were net sinks of N2O. Our study indicates that using subsurface band application of PL was the most promising environmentally sustainable poultry waste application method for reducing CH4and N2O emissions from agricultural soil in NT and CT corn production systems on the Decatur soil in north Alabama.

An Initial Investigation into the Use of a Flux Chamber Technique to Measure Soil-Atmosphere Gas Exchanges from Application of Biosolids to UK Soils

While a significant amount of work has been conducted to assess the concentration of pollutants in soils and waterways near land that has been amended with biosolids, a relatively small body of research investigating emissions to atmosphere is available in the literature. Some studies have indicated that while the CO2emissions from soils decrease with fertiliser application, the CH4and N2O emissions might be increased, offsetting the benefit. The objective of the research presented in this paper was to address this gap, by the use of a flux chamber technique to measure soil-atmosphere gas exchanges from the application of biosolids to land. This was done by applying three different types of biosolids to soils and measuring gases at the soil-atmosphere interface. The measurements were taken on areas with three different types of vegetation. The gases were collected using a flux chamber technique and analysed by gas chromatography. The results presented here are preliminary findings of an ongoing experiment. Insignificant variation appeared to occur between different areas of vegetation; however, small variations in gas concentrations were observed indicating a need for continued monitoring of soil-atmosphere gas exchanges to determine the long-term impacts on the atmosphere and the environment.

Description and application of the EAP computer program for calculating life-cycle energy use and greenhouse gas emissions of household consumption items

Focusing on reduction in energy use and greenhouse gas emissions, a life-cycle-based analysis tool has been developed. The energy analysis program (EAP) is a computer program for determining energy use and greenhouse gas emissions related to household consumption items, using a hybrid calculation method. EAP consists of a number of fill-in screens corresponding to steps in the hybrid method, which in their turn correspond to different stages in life-cycles of consumer goods. The database incorporated in EAP comprises data about energy use and emissions of the main greenhouse gases (CO2, CH4and N2O) concerning materials, economic sectors, means of transport, etc. The use of the program in several projects showed the applicability and usefulness of EAP in research and policy. In this article, EAP is applied to food: French beans as a metaphor for fruit and vegetables.

Seasonal Study of Methane and Nitrous Oxide in the Coastal Waters of the Southern Baltic Sea

Atmospheric and dissolved methane (CH4) and nitrous oxide (N2O) were measured in the unique coastal ecosystem of theBoddenwaters, including the western Oder estuary, (southern Baltic Sea) during five campaigns between 1994 and 1997. The CH4saturations, ranging from 105–15500%, showed great spatial and temporal variability with maximum values in September and minimum values in December. The N2O saturations were in the range of 91–312% with a maximum in March. Enhanced concentrations of both gases were observed only in the western Oder estuary near the mouth of the Peene River. Thus, we conclude that the distributions of CH4and N2O in the investigatedBoddenwaters are, directly or indirectly, linked to the Peene River runoff and not to the Oder River. Our estimate of the annual CH4emissions from theBoddenwaters to the atmosphere indicates a significant contribution (c.17%) to the overall CH4emissions from the Baltic Sea. In contrast, theBoddenwaters represent only a small source for atmospheric N2O.CH4production rates estimated from sediment slurry experiments revealed a significant spatial variability and indicated that methanogenic activity was related to acetate consumption in the surface sediment layer. Sedimentary CH4production might depend on different amounts of accumulation of organic material.

Extrapolating feedback processes from the present to the past

Extant terrestrial vegetation alters its physical environment via its albedo, and its influence on immediate temperature via stomatal and boundary–layer influences of energy dissipation as sensible and latent heat; aquatic vegetation also controls albedo (e.g. coccolithophorids) and, by competing with water for electromagnetic energy absorption, the depth of the mixed layer and hence the quantity of nutrients trapped for the spring bloom. Both aquatic and terrestrial vegetation have had, together with microbial and geological processes, an influence on O2and CO2levels, and hence on the availability and biological functioning of Fe, Mn, Cu, Zn, Se and P, and the relative competitive advantage of C3versus C4, crassulacean acid metabolism (CAM) and carbon concentration mechanism (CCM) organisms. Less directly, changes in primary productivity impact on the production of CH4and N2O which, like CO2, are greenhouse gases, while some (marine) primary producers yield dimethyl sulphide (and hence cloud condensation nuclei, with effects on cloudiness) and halocarbons (via, in part, O2–dependent processes), partly negating the O3attenuation of UV–B radiation. These effects can be related to the terrestrial embryophytic vegetation back to ca. 450 Ma, and to eukaryotic marine vegetation back to at least 1.7, and probably 2.1 Ga, with implications for inter alia C3versus C4, CAM and CCM photosynthesis, and Fe acquisition mechanisms. Even earlier (3.8 Ga onwards) prokaryotes may have influenced CO2levels and hence controlled (as they did later) surface temperature. By producing O2, they led to decreasing availability of Fe, Mn and P (and utility of Se?), and increasing availability of Cu (and Zn?) that shaped the biochemistry on which later biogeochemistry was based.

Measurements of CH4and N2O fluxes at the landscape scale using micrometeorological methods

Flux gradient, eddy covariance and relaxed eddy accumulation methods were applied to measure CH4and N2O emissions from peatlands and arable land respectively. Measurements of N2O emission by eddy covariance using tunable diode laser spectroscopy provided fluxes ranging from 2 to 60 µ mol N2O m-2h-1with a mean value of 22 µ mol N2O m-2h-1from 320 h of continuous measurements. Fluxes of CH4measured above peatland in Caithness (U.K.) during May and June 1993 by eddy covariance and relaxed eddy accumulation methods were in the range 70 to 120 µ mol CH4m-2h-1with means of 14.7 µ mol CH4m-2h-1and 22.7 µ mol CH4m-2h-1respectively. Emissions of CH4from peatland changed with water table depth and soil temperature; increasing from 25 |Amol CH4m-2h-1at 5% pool area to 50 p.mol CH4m-2h-1with 30% within the flux footprint occupied by pools. A temperature response of 4.9 (xmol CH4m-2h-1°C-1in the range 6-12 °C was also observed. The close similarity in average CH4emission fluxes reported for wetlands in Caithness, Hudson Bay and Alaska in the range 11 to 40 jamol CH4m-2h-1suggests that earlier estimates of CH4emission from high latitude wetlands were too large or that the area of high latitudes contributing to CH4emission has been seriously underestimated.

Tests of photochemical and dynamical theories from satellite data

The launch of Nimbus 7 in 1978 led to the acquisition of global data sets for a number of stratospheric constituents: O 3 , HNO 3 , NO 2 , H 2 O, CH 4 and N 2 O. These data have been used extensively in studies of atmospheric chemistry and transport. Some examples of these studies are presented in this paper.

Solar infra-red spectroscopy from high-altitude aircraft

The infra-red solar spectrum has been the subject of a fairly continuous study since the first elementary observations of Sir John Herschel in 1832. Figure 12 reproduces the solar spectrum recorded by Langley & Abbott in 1900, and this early record serves as an example to show that much of the sun’s incident energy fails to reach the earth. The main absorbing constituents of the atmosphere are water vapour and CO 2 , and these are the cause of the deep bands in the infra-red spectrum. In recent years other rearr gases, such as O 3 , HDO, CO, CH 4 and N 2 O, have been identified through their characteristic absorption bands. It is interesting to note that the HDO absorption band at 3·67 μ , first reported by Gebbie, Harding, Hilsum & Roberts in 1949, is clearly recorded in the Langley & Abbott spectrum, although with deuterium unknown it was impossible for them to identify it. The rarer constituents of the atmosphere have interested a number of experi­menters in more recent years and, for example, Shaw, Chapman, Howard & Oxholm (1951) have identified some 800 lines of atmphoseric origin in the small region between 3·0 and 5·2 μ . However, at ground level measurements are only possible where some solar energy reaches the earth. In order to make observations in the regions normally obscured it is necessary to reduce the amount of water vapour and carbon dioxide in the path by going to high altitude. The percentage CO 2 content of the atmosphere is approximately constant, and hence the amount of CO 2 between the sun and an observer will be reduced to one-half in going to 18000 ft. and to about one-tenth in going to 50000 ft. The water-vapour content falls off much more rapidly and measurements can be made in the 2·5 to 3·5 μ band by going to only 30000 ft. Migeotte & Neven (1952 a, b ) have made an attempt to overcome the effects of the denser lower atmosphere by making observations from the summit of the Jungfraujoch at a height of almost 12000 ft. By carrying a spectrometer in a modern aircraft it is possible to make detailed observations from heights greater than 50000 ft. A program of high-altitude spectroscopy is being undertaken jointly by the Gassiot Committee of the Royal Society and the Royal Aircraft Establishment, Farnborough. The purpose of the program is to record the solar spectrum out into the far infra-red from a Canberra aircraft flying at these heights.