scholarly journals Methane and nitrous oxide sources and emissions in a subtropical freshwater reservoir, South East Queensland, Australia

2014 ◽  
Vol 11 (18) ◽  
pp. 5245-5258 ◽  
Author(s):  
K. Sturm ◽  
Z. Yuan ◽  
B. Gibbes ◽  
U. Werner ◽  
A. Grinham
Keyword(s):  
Nitrous Oxide ◽  
Water Column ◽  
Water Flux ◽  
No Production ◽  
Pore Waters ◽  
Ch4 Production ◽  
N2o Fluxes ◽  
Ch4 And N2o ◽  
Diffusive Fluxes ◽  
Carbon Dioxide Co2

Abstract. Reservoirs have been identified as an important source of non-carbon dioxide (CO2) greenhouse gases with wide ranging fluxes for reported methane (CH4); however, fluxes for nitrous oxide (N2O) are rarely quantified. This study investigates CH4 and N2O sources and emissions in a subtropical freshwater Gold Creek Reservoir, Australia, using a combination of water–air and sediment–water flux measurements and water column and pore water analyses. The reservoir was clearly a source of these gases as surface waters were supersaturated with CH4 and N2O. Atmospheric CH4 fluxes were dominated by ebullition (60 to 99%) relative to diffusive fluxes and ranged from 4.14 × 102 to 3.06 × 105 μmol CH4 m−2 day−1 across the sampling sites. Dissolved CH4 concentrations were highest in the anoxic water column and sediment pore waters (approximately 5 000 000% supersaturated). CH4 production rates of up to 3616 ± 395 μmol CH4 m−2 day−1 were found during sediment incubations in anoxic conditions. These findings are in contrast to N2O where no production was detected during sediment incubations and the highest dissolved N2O concentrations were found in the oxic water column which was 110 to 220% supersaturated with N2O. N2O fluxes to the atmosphere were primarily through the diffusive pathway, mainly driven by diffusive fluxes from the water column and by a minor contribution from sediment diffusion and ebullition. Results suggest that future studies of subtropical reservoirs should monitor CH4 fluxes with an appropriate spatial resolution to ensure capture of ebullition zones, whereas assessment of N2O fluxes should focus on the diffusive pathway.

scholarly journals Methane and nitrous oxide sources and emissions in a subtropical freshwater reservoir, south east Queensland, Australia

2013 ◽  
Vol 10 (12) ◽  
pp. 19485-19508
Author(s):  
K. Sturm ◽  
Z. Yuan ◽  
B. Gibbes ◽  
A. Grinham
Keyword(s):  
Nitrous Oxide ◽  
Water Column ◽  
Water Flux ◽  
N2o Emissions ◽  
Pore Waters ◽  
Flux Measurements ◽  
Study Support ◽  
Ch4 And N2o ◽  
Diffusive Fluxes ◽  
Freshwater Reservoir

Abstract. Reservoirs have been identified as an important source of non-CO2 greenhouse gases, especially methane (CH4). This study investigates CH4 and nitrous oxide (N2O) sources and emissions in a subtropical freshwater reservoir Gold Creek Dam, Australia using a combination of water–atmosphere and sediment–water flux measurements, water column sampling and pore water analysis. The reservoir was clearly a net source as surface waters were supersaturated with CH4 and N2O. CH4 flux rates were one to two orders of magnitude higher than N2O rates when expressed as CO2 equivalents. Atmospheric CH4 fluxes were dominated by ebullition (<60%) relative to diffusive fluxes and ranged from 165 to 6526 mg CO2 eq m−2 d−1. Dissolved CH4 concentrations in sediment pore waters were approximately 5 000 000% supersaturated. However, dissolved N2O concentrations were 140 to 220% supersaturated and generally confined to the water column greatly reducing the likelihood of ebullition. The flux measurements from this study support past findings that demonstrate the potential important contribution of emissions from subtropical reservoirs to overall GHG budgets. Results suggest future efforts to monitor and model emissions that concentrate on quantifying the ebullition pathway for CH4 as this was dominant relative to diffusive fluxes as well as total N2O emissions.

scholarly journals Automatic high-frequency measurements of full soil greenhouse gas fluxes in a tropical forest

2018 ◽  
Author(s):  
Elodie Alice Courtois ◽  
Clément Stahl ◽  
Benoit Burban ◽  
Joke Van den Berge ◽  
Daniel Berveiller ◽  
...  
Keyword(s):  
High Frequency ◽  
Co2 Flux ◽  
Appropriate Technology ◽  
Flux Chamber ◽  
Soil Co2 Flux ◽  
Reliable Estimation ◽  
Closure Time ◽  
N2o Fluxes ◽  
Ch4 And N2o ◽  
Carbon Dioxide Co2

Abstract. Measuring in situ soil fluxes of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) continuously at high frequency requires appropriate technology. We tested the combination of a commercial automated soil CO2 flux chamber system (LI-8100A) with a CH4 and N2O analyzer (Picarro G2308) in a tropical rainforest for 4 months. A chamber closure time of 2 minutes was sufficient for a reliable estimation of CO2 and CH4 fluxes (100 % and 98.5 % of fluxes were above Minimum Detectable Flux – MDF, respectively). This closure time was generally not suitable for a reliable estimation of the low N2O fluxes in this ecosystem but was sufficient for detecting rare major peak events. A closure time of 25 minutes was more appropriate for reliable estimation of most N2O fluxes (85.6 % of measured fluxes are above MDF ± 0.002 nmol m−2 s−1). Our study highlights the importance of adjusted closure time for each gas.

scholarly journals Impacts of Clear-Cutting of a Boreal Forest on Carbon Dioxide, Methane and Nitrous Oxide Fluxes

Forests ◽  
2020 ◽  
Vol 11 (9) ◽  
pp. 961
Author(s):  
Patrik Vestin ◽  
Meelis Mölder ◽  
Natascha Kljun ◽  
Zhanzhang Cai ◽  
Abdulghani Hasan ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Nitrous Oxide ◽  
Forest Management ◽  
Boreal Forest ◽  
Total Carbon ◽  
Clear Cut ◽  
Clear Cutting ◽  
N2o Fluxes ◽  
Ch4 And N2o ◽  
Ghg Fluxes

The 2015 Paris Agreement encourages stakeholders to implement sustainable forest management policies to mitigate anthropogenic emissions of greenhouse gases (GHG). The net effects of forest management on the climate and the environment are, however, still not completely understood, partially as a result of a lack of long-term measurements of GHG fluxes in managed forests. During the period 2010–2013, we simultaneously measured carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) fluxes using the flux-gradient technique at two clear-cut plots of different degrees of wetness, located in central Sweden. The measurements started approx. one year after clear-cutting, directly following soil scarification and planting. The study focused on robust inter-plot comparisons, spatial and temporal dynamics of GHG fluxes, and the determination of the global warming potential of a clear-cut boreal forest. The clear-cutting resulted in significant emissions of GHGs at both the wet and the dry plot. The degree of wetness determined, directly or indirectly, the relative contribution of each GHG to the total budgets. Faster establishment of vegetation on the wet plot reduced total emissions of CO2 as compared to the dry plot but this was partially offset by higher CH4 emissions. Waterlogging following clear-cutting likely caused both plots to switch from sinks to sources of CH4. In addition, there were periods with N2O uptake at the wet plot, although both plots were net sources of N2O on an annual basis. We observed clear diel patters in CO2, CH4 and N2O fluxes during the growing season at both plots, with the exception of CH4 at the dry plot. The total three-year carbon budgets were 4107 gCO2-equivalent m−2 and 5274 gCO2-equivalent m−2 at the wet and the dry plots, respectively. CO2 contributed 91.8% to the total carbon budget at the wet plot and 98.2% at the dry plot. For the only full year with N2O measurements, the total GHG budgets were 1069.9 gCO2-eqvivalents m−2 and 1695.7 gCO2-eqvivalents m−2 at the wet and dry plot, respectively. At the wet plot, CH4 contributed 3.7%, while N2O contributed 7.3%. At the dry plot, CH4 and N2O contributed 1.5% and 7.6%, respectively. Our results emphasize the importance of considering the effects of the three GHGs on the climate for any forest management policy aiming at enhancing the mitigation potential of forests.

scholarly journals Combining two complementary micrometeorological methods to measure CH<sub>4</sub> and N<sub>2</sub>O fluxes over pasture

2015 ◽  
Vol 12 (18) ◽  
pp. 15245-15299 ◽  
Author(s):  
J. Laubach ◽  
M. Barthel ◽  
A. Fraser ◽  
J. E. Hunt ◽  
D. W. T. Griffith
Keyword(s):  
Large Fraction ◽  
Industrial Sector ◽  
N2o Emissions ◽  
Emission Rates ◽  
Co2 Fluxes ◽  
Nitrogen Inputs ◽  
Animal Excreta ◽  
N2o Fluxes ◽  
Ch4 And N2o ◽  
Carbon Dioxide Co2

Abstract. New Zealand's largest industrial sector is pastoral agriculture, giving rise to a large fraction of the country's emissions of methane (CH4) and nitrous oxide (N2O). We designed a system to continuously measure CH4 and N2O fluxes at the field scale on two adjacent pastures that differed with respect to management. At the core of this system was a closed-cell Fourier-transform infrared spectrometer (FTIR), measuring the mole fractions of CH4, N2O and carbon dioxide (CO2) at two heights at each site. In parallel, CO2 fluxes were measured using eddy-covariance instrumentation. We applied two different micrometeorological ratio methods to infer the CH4 and N2O fluxes from their respective mole fractions and the CO2 fluxes. The first is a variant of the flux-gradient method, where it is assumed that the turbulent diffusivities of CH4 and N2O equal that of CO2. This method was reliable when the CO2 mole-fraction difference between heights was at least 4 times greater than the FTIR's resolution of differences. For the second method, the temporal increases of mole fractions in the stable nocturnal boundary layer, which are correlated for concurrently-emitted gases, are used to infer the unknown fluxes of CH4 and N2O from the known flux of CO2. This method was sensitive to "contamination" from trace gas sources other than the pasture of interest and therefore required careful filtering. With both methods combined, estimates of mean daily CH4 and N2O fluxes were obtained for 60 % of days at one site and 77 % at the other. Both methods indicated both sites as net sources of CH4 and N2O. Mean emission rates for one year at the unfertilised, winter-grazed site were 8.2 (± 0.91) nmol CH4 m−2 s−1 and 0.40 (± 0.018) nmol N2O m−2 s−1. During the same year, mean emission rates at the irrigated, fertilised and rotationally-grazed site were 7.0 (± 0.89) nmol CH4 m−2 s−1 and 0.57 (± 0.019) nmol N2O m−2 s−1. At this site, the N2O emissions amounted to 1.19 (± 0.15) % of the nitrogen inputs from animal excreta and fertiliser application.

scholarly journals Methane and nitrous oxide exchange over a managed hay meadow

2014 ◽  
Vol 11 (24) ◽  
pp. 7219-7236 ◽  
Author(s):  
L. Hörtnagl ◽  
G. Wohlfahrt
Keyword(s):  
Nitrous Oxide ◽  
Sink Strength ◽  
N2o Emissions ◽  
Eddy Covariance Method ◽  
Sources And Sinks ◽  
Mountain Grassland ◽  
Time Period ◽  
Soil Temperatures ◽  
N2o Fluxes ◽  
Ch4 And N2o

Abstract. The methane (CH4) and nitrous oxide (N2O) exchange of a temperate mountain grassland near Neustift, Austria, was measured during 2010–2012 over a time period of 22 months using the eddy covariance method. Exchange rates of both compounds at the site were low, with 97% of all half-hourly CH4 and N2O fluxes ranging between ±200 and ±50 ng m−2 s−1, respectively. The meadow acted as a sink for both compounds during certain time periods, but was a clear source of CH4 and N2O on an annual timescale. Therefore, both gases contributed to an increase of the global warming potential (GWP), effectively reducing the sink strength in terms of CO2 equivalents of the investigated grassland site. In 2011, our best guess estimate showed a net greenhouse gas (GHG) sink of −32 g CO2 equ. m−2 yr−1 for the meadow, whereby 55% of the CO2 sink strength of −71 g CO2 m−2 yr−1 was offset by CH4 (N2O) emissions of 7 (32) g CO2 equ. m−2 yr−1. When all data were pooled, the ancillary parameters explained 27 (42)% of observed CH4 (N2O) flux variability, and up to 62 (76)% on shorter timescales in-between management dates. In the case of N2O fluxes, we found the highest emissions at intermediate soil water contents and at soil temperatures close to 0 or above 14 °C. In comparison to CO2, H2O and energy fluxes, the interpretation of CH4 and N2O exchange was challenging due to footprint heterogeneity regarding their sources and sinks, uncertainties regarding post-processing and quality control. Our results emphasize that CH4 and N2O fluxes over supposedly well-aerated and moderately fertilized soils cannot be neglected when evaluating the GHG impact of temperate managed grasslands.

scholarly journals Methane and nitrous oxide exchange over a managed hay meadow

2014 ◽  
Vol 11 (6) ◽  
pp. 8181-8225
Author(s):  
L. Hörtnagl ◽  
G. Wohlfahrt
Keyword(s):  
Nitrous Oxide ◽  
Sink Strength ◽  
N2o Emissions ◽  
Eddy Covariance Method ◽  
Sources And Sinks ◽  
Mountain Grassland ◽  
Time Period ◽  
Soil Temperatures ◽  
N2o Fluxes ◽  
Ch4 And N2o

Abstract. The methane (CH4) and nitrous oxide (N2O) exchange of a temperate mountain grassland near Neustift, Austria, was measured during 2010–2012 over a time period of 22 months using the eddy covariance method. Exchange rates of both compounds at the site were low, with more than 95% of the half-hourly fluxes of CH4 and N2O ranging between ±10 and ±1 nmol m−2 s−1, respectively. The meadow acted as a sink for both compounds during certain time periods, but was a clear source of CH4 and N2O on an annual time scale. Therefore, both gases contributed to an increase of the global warming potential (GWP), effectively reducing the sink strength in terms of CO2-equivalents of the investigated grassland site. In 2011, our best guess estimate showed a net GHG sink of −32 g CO2-equ. m−2 yr−1 for the meadow, whereby 55% of the CO2 sink strength of −71 g CO2 m−2 yr−1 was offset by CH4/N2O emissions of 7/32 g CO2-equ. m−2 yr−1. When all data were pooled, the ancillary parameters explained 26/38% of observed CH4/N2O flux variability, and up to 62/75% on shorter time scales in-between management dates. In case of N2O fluxes, we found highest emissions at intermediate soil water contents and at soil temperatures close to zero or above 14 °C. In comparison to CO2, H2O and energy fluxes, the interpretation of CH4 and N2O exchange was challenging due to footprint heterogeneity regarding their sources and sinks, uncertainties regarding post-processing and quality control. Our results emphasize that CH4 and N2O fluxes over supposedly well-aerated and moderately fertilized soils cannot be neglected when evaluating the GHG impact of temperate managed grasslands.

scholarly journals Fluxes of CO<sub>2</sub>, CH<sub>4</sub> and N<sub>2</sub>O from soil of burned grassland savannah of central Africa

2010 ◽  
Vol 7 (3) ◽  
pp. 4089-4126 ◽  
Author(s):  
S. Castaldi ◽  
A. de Grandcourt ◽  
A. Rasile ◽  
U. Skiba ◽  
R. Valentini
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Water Saturation ◽  
Soil Parameters ◽  
N2o Emissions ◽  
No Production ◽  
Net N Mineralization ◽  
N2o Fluxes ◽  
Ch4 And N2o ◽  
The Impact

Abstract. Grassland savannah ecosystems subject to frequent fires are considered to have an almost neutral carbon balance, as the C released during burning mostly balance the C fixed by the photosynthetic process. However, burning might modify the net soil-atmosphere exchange of GHGs in the post burning phase so that the radiative balance of the site might shift from neutrality. In the present study the impact of fire on soil fluxes of CO2, CH4 and N2O was investigated in a grassland savannah (Congo Brazzaville) where high frequency burning is the typical management form of the region. An area was preserved for one season from annual burning and was used as "unburned" treatment. Two field campaigns were carried on at different time length from the fire event, 1 month, in the middle of the dry season, and 8 months after, at the end of the growing season. CO2, CH4 and N2O fluxes, as well as several soil parameters, were measured in each campaign from burned and unburned plots. Rain events were simulated at each campaign to evaluate magnitude and length of the generated GHG flux pulses. In laboratory experiments, on soil samples from the two treatments, microbial biomass, net N mineralization, net nitrification, N2O, NO and CO2 emissions were analyzed in function of soil water and/or temperature variations. Results showed that fire had a significant effect on GHG fluxes but the effect was transient, as after 8 months differences between treatments were no longer significant. One month after burning CO2 soil emissions were significantly lower in the burned plots, CH4 fluxes were dominated by net emissions rather than net consumption in the unburned area and fire shifted the CH4 flux distribution towards more negative values. No significant effect of fire was observed in the field on N2O fluxes. It was assumed that the low water content was the main limiting factor as in fact laboratory data showed that only above 75% of water saturation, N2O emissions increased sharply and more strongly in the soil from burned plots. This soil water content was hardly reached in the field even in the watered plots. Burned also stimulated NO production in the laboratory, which was more evident at low water content. Differently from N2O, 25% of water saturation was sufficient to significantly stimulate CO2 production in the laboratory and rain simulation in the field stimulated soil respiration. However in the laboratory the highest fluxes were measured in burned soil whereas in the field the opposite was observed. Increasing the incubation temperature from 25 °C to 37 °C affected negatively microbial growth and activities (mineralization and nitrification) but stimulated gas production (N2O and CO2). Overall, data indicate that fire would have a reductive or null impact on soil GHG emissions in savannah sites presenting similar soil characteristics (acidic, well drained, nutrient poor) and land management (high fire frequency).

Soil–Atmosphere Exchange of Trace Gases in the Colorado Shortgrass Steppe

2008 ◽  
Author(s):  
Arvin R. Mosier ◽  
William J. Parton
Keyword(s):  
Nitrous Oxide ◽  
Greenhouse Gases ◽  
Atmospheric Chemistry ◽  
Trace Gases ◽  
Absolute Amount ◽  
N2o Production ◽  
Past Half Century ◽  
Low Concentrations ◽  
Ch4 And N2o ◽  
Carbon Dioxide Co2

During the past half century, atmospheric concentrations of important greenhouse gases including carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) have been increasing at unprecedented rates ( I PCC, 1996, 2007). Trace gases such as methane (CH4), nitric oxide (NO), and nitrous oxide (N2O) are exchanged regularly between the soil and atmosphere, playing important roles in the greenhouse effect, in atmospheric chemistry, and in the redistribution of ecosystem nitrogen (N). Soils can be important sources of greenhouse gases, commonly contributing up to two thirds of atmospheric N2O and more than one third of atmospheric CH4 (Monson and Holland, 2001; Smith et al., 2003). Recent extensive changes in land management and in cultivation, which can stimulate N2O production and/or decrease CH4 uptake, could be contributing to the observed increases of both CH4 and N2O in the atmosphere (IPCC, 2007). Although the absolute amount of trace gases (such as CH4, NO, and N2O) released into the atmosphere from soils may be small, these gases are extremely effective at absorbing infrared radiation (Smith et al., 2003). Methane, for example, is 20 to 30 times more effcient than CO2 as a greenhouse gas (LeMer and Roger, 2001). As a result, even small changes in the production or consumption of these gases by soils could dramatically influence climate change. Of the gases exchanged between the soil and atmosphere, the major reactive ones are oxides of N (NO and NO2, collectively referred to as NOx). Combustion is a major source of NOx, but native and N-fertilized soils also contribute signi3 - cant amounts of NOx to the atmosphere (Williams et al., 1992). Nitric and nitrous oxide play a complex role in atmospheric chemistry. At low concentrations, it catalyzes the breakdown of ozone. At higher concentrations it can interact with carbon monoxide (CO), hydroxyl radicals (OH.), and hydrocarbons to produce ozone. Atmospheric NOx is converted within days to nitric acid, which is an important component (30% to 50%) of acidity in precipitation (Williams et al., 1992).

scholarly journals Combining two complementary micrometeorological methods to measure CH<sub>4</sub> and N<sub>2</sub>O fluxes over pasture

2016 ◽  
Vol 13 (4) ◽  
pp. 1309-1327 ◽  
Author(s):  
Johannes Laubach ◽  
Matti Barthel ◽  
Anitra Fraser ◽  
John E. Hunt ◽  
David W. T. Griffith
Keyword(s):  
Large Fraction ◽  
Industrial Sector ◽  
N2o Emissions ◽  
Emission Rates ◽  
Co2 Fluxes ◽  
Nitrogen Inputs ◽  
Animal Excreta ◽  
N2o Fluxes ◽  
Ch4 And N2o ◽  
Carbon Dioxide Co2

Abstract. New Zealand's largest industrial sector is pastoral agriculture, giving rise to a large fraction of the country's emissions of methane (CH4) and nitrous oxide (N2O). We designed a system to continuously measure CH4 and N2O fluxes at the field scale on two adjacent pastures that differed with respect to management. At the core of this system was a closed-cell Fourier transform infrared (FTIR) spectrometer, which measured the mole fractions of CH4, N2O and carbon dioxide (CO2) at two heights at each site. In parallel, CO2 fluxes were measured using eddy-covariance instrumentation. We applied two different micrometeorological ratio methods to infer the CH4 and N2O fluxes from their respective mole fractions and the CO2 fluxes. The first is a variant of the flux-gradient method, where it is assumed that the turbulent diffusivities of CH4 and N2O equal that of CO2. This method was reliable when the CO2 mole-fraction difference between heights was at least 4 times greater than the FTIR's resolution of differences. For the second method, the temporal increases of mole fractions in the stable nocturnal boundary layer, which are correlated for concurrently emitted gases, are used to infer the unknown fluxes of CH4 and N2O from the known flux of CO2. This method was sensitive to “contamination” from trace gas sources other than the pasture of interest and therefore required careful filtering. With both methods combined, estimates of mean daily CH4 and N2O fluxes were obtained for 56 % of days at one site and 73 % at the other. Both methods indicated both sites as net sources of CH4 and N2O. Mean emission rates for 1 year at the unfertilised, winter-grazed site were 8.9 (±0.79) nmol CH4 m−2 s−1 and 0.38 (±0.018) nmol N2O m−2 s−1. During the same year, mean emission rates at the irrigated, fertilised and rotationally grazed site were 8.9 (±0.79) nmol CH4 m−2 s−1 and 0.58 (±0.020) nmol N2O m−2 s−1. At this site, the N2O emissions amounted to 1.21 (±0.15) % of the nitrogen inputs from animal excreta and fertiliser application.

scholarly journals Automatic high-frequency measurements of full soil greenhouse gas fluxes in a tropical forest

2019 ◽  
Vol 16 (3) ◽  
pp. 785-796 ◽  
Author(s):  
Elodie Alice Courtois ◽  
Clément Stahl ◽  
Benoit Burban ◽  
Joke Van den Berge ◽  
Daniel Berveiller ◽  
...  
Keyword(s):  
High Frequency ◽  
Co2 Flux ◽  
Appropriate Technology ◽  
Flux Chamber ◽  
Soil Co2 Flux ◽  
Reliable Estimation ◽  
Closure Time ◽  
N2o Fluxes ◽  
Ch4 And N2o ◽  
Carbon Dioxide Co2

Abstract. Measuring in situ soil fluxes of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) continuously at high frequency requires appropriate technology. We tested the combination of a commercial automated soil CO2 flux chamber system (LI-8100A) with a CH4 and N2O analyzer (Picarro G2308) in a tropical rainforest for 4 months. A chamber closure time of 2 min was sufficient for a reliable estimation of CO2 and CH4 fluxes (100 % and 98.5 % of fluxes were above minimum detectable flux – MDF, respectively). This closure time was generally not suitable for a reliable estimation of the low N2O fluxes in this ecosystem but was sufficient for detecting rare major peak events. A closure time of 25 min was more appropriate for reliable estimation of most N2O fluxes (85.6 % of measured fluxes are above MDF ± 0.002 nmol m−2 s−1). Our study highlights the importance of adjusted closure time for each gas.

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