scholarly journals Technical note: mesocosm approach to quantification of carbon dioxide fluxes across the vadose zone

2013 ◽  
Vol 10 (6) ◽  
pp. 9947-9967
Author(s):  
E. M. Thaysen ◽  
S. Jessen ◽  
P. Ambus ◽  
C. Beier ◽  
D. Postma ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Vadose Zone ◽  
Water Flux ◽  
Lower Boundary ◽  
Agricultural Practices ◽  
Small Variation ◽  
Technical Note ◽  
Carbon Dioxide Partial Pressure ◽  
Physical Factors ◽  
Promising Tool

Abstract. Carbon dioxide (CO2) fluxes in the vadose zone are influenced by a complex interplay of biological, chemical and physical factors. A soil mesocosm system was designed to assess the effect of agricultural practices on carbon fluxes within and out of the vadose zone at controlled environmental conditions. Carbon dioxide partial pressure (pCO2), alkalinity, soil moisture and temperature were measured with depth and time, and DIC in the percolate was quantified using a sodium hydroxide trap. Results showed good reproducibility between two replicate mesocosms. The pCO2 varied between 0.2–1.1% and alkalinity was 0.1–0.6 meq L−1. The measured effluent DIC flux was 185–196 mg L−1 m−2 and in the same range as estimates derived from pCO2 and alkalinity in samples extracted from the side of the mesocosm column, and the water flux. The relatively small variation provides confidence that the mesocosm system is a promising tool for studying a~range of processes in unsaturated environments. Meanwhile, high suction at the mesocosm bottom applied to reduce water ponding during intensive irrigation caused degassing of dissolved CO2 from the water phase just below the outlet, leading to diffusion of dissolved CO2 across the lower boundary. Though not influencing DIC flux measurements to the groundwater, this lead to a lowering of the pCO2 in the stagnant water at the mesocosm bottom. A free-drainage boundary is suggested in order to avoid this effect.

scholarly journals Technical Note: Mesocosm approach to quantify dissolved inorganic carbon percolation fluxes

2014 ◽  
Vol 11 (4) ◽  
pp. 1077-1084 ◽  
Author(s):  
E. M. Thaysen ◽  
S. Jessen ◽  
P. Ambus ◽  
C. Beier ◽  
D. Postma ◽  
...  
Keyword(s):  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Experimental Period ◽  
Technical Note ◽  
Transport Processes ◽  
Carbon Dioxide Partial Pressure ◽  
Physical Factors ◽  
Soil Carbon Dioxide ◽  
Promising Tool ◽  
Unplanted Soil

Abstract. Dissolved inorganic carbon (DIC) fluxes across the vadose zone are influenced by a complex interplay of biological, chemical and physical factors. A novel soil mesocosm system was evaluated as a tool for providing information on the mechanisms behind DIC percolation to the groundwater from unplanted soil. Carbon dioxide partial pressure (pCO2), alkalinity, soil moisture and temperature were measured with depth and time, and DIC in the percolate was quantified using a sodium hydroxide trap. Results showed good reproducibility between two replicate mesocosms. The pCO2 varied between 0.2 and 1.1%, and the alkalinity was 0.1–0.6 meq L−1. The measured cumulative effluent DIC flux over the 78-day experimental period was 185–196 mg L−1 m−2 and in the same range as estimates derived from pCO2 and alkalinity in samples extracted from the side of the mesocosm column and the drainage flux. Our results indicate that the mesocosm system is a promising tool for studying DIC percolation fluxes and other biogeochemical transport processes in unsaturated environments.

scholarly journals Inorganic carbon fluxes across the vadose zone of planted and unplanted soil mesocosms

2014 ◽  
Vol 11 (3) ◽  
pp. 4251-4299 ◽  
Author(s):  
E. M. Thaysen ◽  
D. Jacques ◽  
S. Jessen ◽  
C. E. Andersen ◽  
E. Laloy ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Vadose Zone ◽  
Inorganic Carbon ◽  
Plant Biomass ◽  
Dissolved Inorganic Carbon ◽  
Carbon Fluxes ◽  
Atmospheric Co2 ◽  
Carbon Dioxide Partial Pressure ◽  
Post Harvest ◽  
Unplanted Soil

Abstract. The efflux of carbon dioxide (CO2) from soils influences atmospheric CO2 concentrations and thereby climate change. The partitioning of inorganic carbon fluxes in the vadose zone between emission to the atmosphere and to the groundwater was investigated. Carbon dioxide partial pressure in the soil gas (pCO2), alkalinity, soil moisture and temperature were measured over depth and time in unplanted and planted (barley) mesocosms. The dissolved inorganic carbon (DIC) percolation flux was calculated from the pCO2, alkalinity and the water flux at the mesocosm bottom. Carbon dioxide exchange between the soil surface and the atmosphere was measured at regular intervals. The soil diffusivity was determined from soil radon-222 (222Rn) emanation rates and soil air Rn concentration profiles, and was used in conjunction with measured pCO2 gradients to calculate the soil CO2 production. Carbon dioxide fluxes were modelled using the HP1 module of the Hydrus 1-D software. The average CO2 effluxes to the atmosphere from unplanted and planted mesocosm ecosystems during 78 days of experiment were 0.1 ± 0.07 and 4.9 ± 0.07 μmol carbon (C) m−2 s−1, respectively, and largely exceeded the corresponding DIC percolation fluxes of 0.01 ± 0.004 and 0.06 ± 0.03 μmol C m−2 s−1. Post-harvest soil respiration (Rs) was only 10% of the Rs during plant growth, while the post-harvest DIC percolation flux was more than one third of the flux during growth. The Rs was controlled by production and diffusivity of CO2 in the soil. The DIC percolation flux was largely controlled by the pCO2 and the drainage flux due to low solution pH. Plant biomass and soil pCO2 were high in the mesocosms as compared to a standard field situation. Our results indicate no change of the cropland C balance under elevated atmospheric CO2 in a warmer future climate, in which plant biomass and soil pCO2 are expected to increase.

scholarly journals Inorganic carbon fluxes across the vadose zone of planted and unplanted soil mesocosms

2014 ◽  
Vol 11 (24) ◽  
pp. 7179-7192 ◽  
Author(s):  
E. M. Thaysen ◽  
D. Jacques ◽  
S. Jessen ◽  
C. E. Andersen ◽  
E. Laloy ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Plant Growth ◽  
Vadose Zone ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Carbon Dioxide Partial Pressure ◽  
Co2 Production ◽  
Post Harvest ◽  
Unplanted Soil ◽  
Soil Mesocosms

Abstract. The efflux of carbon dioxide (CO2) from soils influences atmospheric CO2 concentrations and thereby climate change. The partitioning of inorganic carbon (C) fluxes in the vadose zone between emission to the atmosphere and to the groundwater was investigated to reveal controlling underlying mechanisms. Carbon dioxide partial pressure in the soil gas (pCO2), alkalinity, soil moisture and temperature were measured over depth and time in unplanted and planted (barley) mesocosms. The dissolved inorganic carbon (DIC) percolation flux was calculated from the pCO2, alkalinity and the water flux at the mesocosm bottom. Carbon dioxide exchange between the soil surface and the atmosphere was measured at regular intervals. The soil diffusivity was determined from soil radon-222 (222Rn) emanation rates and soil air Rn concentration profiles and was used in conjunction with measured pCO2 gradients to calculate the soil CO2 production. Carbon dioxide fluxes were modeled using the HP1 module of the Hydrus 1-D software. The average CO2 effluxes to the atmosphere from unplanted and planted mesocosm ecosystems during 78 days of experiment were 0.1 ± 0.07 and 4.9 ± 0.07 μmol C m−2 s−1, respectively, and grossly exceeded the corresponding DIC percolation fluxes of 0.01 ± 0.004 and 0.06 ± 0.03 μmol C m−2 s−1. Plant biomass was high in the mesocosms as compared to a standard field situation. Post-harvest soil respiration (Rs) was only 10% of the Rs during plant growth, while the post-harvest DIC percolation flux was more than one-third of the flux during growth. The Rs was controlled by production and diffusivity of CO2 in the soil. The DIC percolation flux was largely controlled by the pCO2 and the drainage flux due to low solution pH. Modeling suggested that increasing soil alkalinity during plant growth was due to nutrient buffering during root nitrate uptake.

Dynamics of CO2 emission from chernozems under agricultural use

2017 ◽  
Vol 4 (3) ◽  
pp. 43-49
Author(s):  
M. Miroshnychenko ◽  
O. Siabruk
Keyword(s):  
Carbon Dioxide ◽  
Agricultural Practices ◽  
Growing Season ◽  
Warm Period ◽  
Direct Seeding ◽  
Soil Tillage ◽  
Plant Residues ◽  
Hydrothermal Conditions ◽  
Organic Mineral ◽  
Mineral System

Aim. The comparison of the effect of hydrothermal conditions and various agricultural practices on the emission of CO 2 from chernozems in the Left-Bank Forest-Steppe of Ukraine. Methods. The dynamics of the intensity of carbon dioxide emissions from chernozem calcic (typical chernozem – in Ukrainian classifi cation) was studied during the growing season of 2011–2012. The observations were based on two fi eld experiments with various methods of soil till- age (6–7 years from the beginning of the experiment) and fertilization systems (21–22 years from the beginning of the experiment). Particularly, plowing at 20–22 cm, disking at 10–12 cm, cultivation at 6–8 cm and direct seeding using Great Plains drill were studied among the soil tillage methods. Mineral system (N 45 P 50 K 45 ), organic system (manure 8 t/ha) and combined organic-mineral system (manure 8 t/ha + N 45 P 50 K 45 ) were studied among fertilization systems. The intensity of CO 2 fl ux was determined using the non-stationary respiratory chambers by the alkaline absorption method, with averaging of the results during the day and the frequency of once a month. Results. During the warm period, the emission of carbon dioxide from the soil changes dynamically depending on temperature and humidity. The maximum of emission coincides with the periods of warm summer showers in June-July, the minimum values are characteristic for the late autumn period. The total emission losses of carbon in chernozems over the vegetation period ranged from 480 to 910 kg/ha and varied depending on the methods of tillage ± (4.0–6.0) % and fertilization systems ± (3.8–7.1) %. The changes in the intensity of CO 2 emission from the soil under different methods of soil tillage are associated with hydrothermal regime and the depth of crop residues location. The biggest difference is observed im- mediately after tillage, but in the spring period the differences are only 12–25 %, and after drying of the top layer of soil become even less. Direct seeding technology provides the greatest emission of CO 2 from chernozem, which is fa- cilitated by better water regime and more complete mineralization of plant residues on the soil surface. Annual losses of carbon are the least under disking of soil at 10–12 cm. The changes in the intensity of CO 2 emission from the soil under different fertilization systems are associated with the involvement of the additional organic matter from plant residues and manure to the microbiological decomposition. The greatest emission was observed under the organic- mineral fertilization system, which increased the loss of carbon by 7–8 % in comparison with the mineral system in the unfavorable hydrothermal year and by 11–15 % in the more favorable year. These differences are observed mainly during the fi rst half of the growing season when there is a clear tendency to increase the intensity of soil respiration. Conclusions. The hydrothermal conditions of the warm period of the year are decisive in the formation of the CO 2 emission fl ow from chernozems. Due to the improvement of agricultural practices, emissions might be reduced but not more that by 15 % of natural factor contribution.

Continuous, transcutaneous carbon-dioxide monitoring to avoid hypercapnia in complex catheter ablations under conscious sedation

2020 ◽  
Vol 41 (Supplement_2) ◽  
Author(s):  
K Weinmann ◽  
A Lenz ◽  
R Heudorfer ◽  
D Aktolga ◽  
M Rattka ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Conscious Sedation ◽  
Venous Blood ◽  
Patient Comfort ◽  
Carbon Dioxide Partial Pressure ◽  
Close Monitoring ◽  
Blood Gas ◽  
Transcutaneous Carbon Dioxide ◽  
The Difference ◽  
Venous Blood Gas

Abstract Background Ablation of complex cardiac arrhythmias requires an immobilized patient. For a successful and safe intervention and for patient comfort, this can be achieved by conscious sedation. Administered sedatives and analgesics have respiratory depressant side effects and require close monitoring. Purpose We investigated the feasibility and accuracy of an additional, continuous transcutaneous carbon-dioxide partial pressure (tpCO2) measurement during conscious sedation in complex electrophysiological catheter ablation procedures. Methods We evaluated the accuracy and additional value of tpCO2 detection by application of a Severinghaus electrode in comparison to arterial and venous blood gas analyses. Results We included 110 patients in this prospective observational study. Arterial pCO2 (paCO2) and tpCO2 showed good correlation throughout the procedures (r=0.60–0.87, p<0.005). Venous pCO2 (pvCO2) were also well correlated to transcutaneous values (r=0.65–0.85, p<0.0001). Analyses of the difference of pvCO2 and tpCO2 measurements showed a tolerance within <10mmHg in up to 96–98% of patients. Hypercapnia (pCO2<70mmHg) was detected more likely and earlier by continuous tpCO2 monitoring compared to half-hourly pvCO2 measurements. Conclusion Continuous tpCO2 monitoring is feasible and precise with good correlation to arterial and venous blood gas carbon-dioxide analysis during complex catheter ablations under conscious sedation and may contribute to additional safety. Funding Acknowledgement Type of funding source: None

Nitrate transport in the chalk vadose zone in in Picardy (France)

2021 ◽  
pp. SP517-2020-164
Author(s):  
N. Surdyk ◽  
L. Gourcy ◽  
V. Bault ◽  
N. Baran
Keyword(s):  
Groundwater Quality ◽  
Vadose Zone ◽  
Nitrate Concentration ◽  
Agricultural Practices ◽  
Nitrate Transport ◽  
Transport Time ◽  
Major Question ◽  
Noticeable Effect ◽  
Fertiliser Application ◽  
The Impact

AbstractSince the 1980s, nitrate has been shown to be present in soils and the vadose zone of various types of geological materials years after fertiliser application. In chalk where the vadose zone is thick, nitrate storage can be considerable and its transport time toward groundwater can be lengthy.In this context, evaluation of the impact of changes in agricultural practices on groundwater quality remains a major question. Improvement of groundwater quality can in certain cases be greatly delayed after the implementation of environmental agricultural practices.The principal objective of this study is to improve our knowledge of when changes in agricultural practices will have a noticeable effect on groundwater quality.To meet this objective, nitrate concentration profiles were performed in agricultural plots in Picardy (France). A crop marker event was used to calculate the transport velocity of water and associated solutes. This method is useful when other tracers (as tritium or chlorine) cannot be used. Estimated velocities range from 0.51 to 0.54 m/year; these values are similar to those described in similar chalk aquifers.

scholarly journals Carbon Dioxide Fluxes and Carbon Stocks under Conservation Agricultural Practices in South Africa

Agriculture ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 374 ◽  
Author(s):  
Patrick Nyambo ◽  
Chiduza Cornelius ◽  
Tesfay Araya
Keyword(s):  
South Africa ◽  
Carbon Dioxide ◽  
Soil Moisture ◽  
Carbon Stock ◽  
Crop Residue ◽  
Agricultural Practices ◽  
Carbon Stocks ◽  
Residue Management ◽  
Co2 Fluxes ◽  
Carbon Dioxide Fluxes

Understanding the impacts of agricultural practices on carbon stocks and CO2 emission is imperative in order to recommend low emission strategies. The objective of this study was to investigate the effects of tillage, crop rotation, and residue management on soil CO2 fluxes, carbon stock, soil temperature, and moisture in the semi-arid conditions in the Eastern Cape of South Africa. The field trial was laid out as a split-split-plot design replicated three times. The main plots were tillage viz conventional tillage (CT) and no-till (NT). The sub-plots were allocated to crop rotations viz maize–fallow–maize (MFM), maize–oat–maize (MOM), and maize–vetch–maize (MVM). Crop residue management was in the sub-sub plots, viz retention (R+), removal (R−), and biochar (B). There were no significant interactions (p > 0.05) with respect to the cumulative CO2 fluxes, soil moisture, and soil temperature. Crop residue retention significantly increased the soil moisture content relative to residue removal, but was not different to biochar application. Soil tilling increased the CO2 fluxes by approximately 26.3% relative to the NT. The carbon dioxide fluxes were significantly lower in R− (2.04 µmoL m−2 s−1) relative to the R+ (2.32 µmoL m−2 s−1) and B treatments (2.36 µmoL m−2 s−1). The carbon dioxide fluxes were higher in the summer (October–February) months compared to the winter period (May–July), irrespective of treatment factors. No tillage had a significantly higher carbon stock at the 0-5 cm depth relative to CT. Amending the soils with biochar resulted in significantly lower total carbon stock relative to both R+ and R−. The results of the study show that NT can potentially reduce CO2 fluxes. In the short term, amending soils with biochar did not reduce the CO2 fluxes compared to R+, however the soil moisture increases were comparable.

scholarly journals Technical Note: Improving computational efficiency in large linear inverse problems: an example from carbon dioxide flux estimation

2012 ◽  
Vol 5 (4) ◽  
pp. 3325-3342
Author(s):  
V. Yadav ◽  
A. M. Michalak
Keyword(s):  
Carbon Dioxide ◽  
Inverse Problems ◽  
Computational Efficiency ◽  
Optimization Problems ◽  
Temporal Distribution ◽  
Carbon Dioxide Flux ◽  
Technical Note ◽  
Sensitivity Matrix ◽  
Direct Computation ◽  
Spatio Temporal

Abstract. Addressing a variety of questions within Earth science disciplines entails the inference of the spatio-temporal distribution of parameters of interest based on observations of related quantities. Such estimation problems often represent inverse problems that are formulated as linear optimization problems. Computational limitations arise when the number of observations and/or the size of the discretized state space become large, especially if the inverse problem is formulated in a probabilistic framework and therefore aims to assess the uncertainty associated with the estimates. This work proposes two approaches to lower the computational costs and memory requirements for large linear space-time inverse problems, taking the Bayesian approach for estimating carbon dioxide (CO2) emissions and uptake (a.k.a. fluxes) as a prototypical example. The first algorithm can be used to efficiently multiply two matrices, as long as one can be expressed as a Kronecker product of two smaller matrices, a condition that is typical when multiplying a sensitivity matrix by a covariance matrix in the solution of inverse problems. The second algorithm can be used to compute a posteriori uncertainties directly at aggregated spatio-temporal scales, which are the scales of most interest in many inverse problems. Both algorithms have significantly lower memory requirements and computational complexity relative to direct computation of the same quantities (O(n2.5) vs. O(n3)). For an examined benchmark problem, the two algorithms yielded a three and six order of magnitude increase in computational efficiency, respectively, relative to direct computation of the same quantities. Sample computer code is provided for assessing the computational and memory efficiency of the proposed algorithms for matrices of different dimensions.

Sign in / Sign up

Export Citation Format

Share Document