Magnitude Of CO Research Articles

CO2 Emission from Oil & Gas Production - Challenges & Opportunities

The analysis in the report is related to the issue of emission of CO 2 from the oil and gas companies in Pakistan. The issue was selected considering the increasing threats for the environmental sustainability that are caused due to the emission of CO 2 gases on consistent basis. The variables that were chosen for the purpose of analysis were knowledge of the firm, incentives of the government, magnitude of CO 2 , cost and scale of CCU technology. The statistical techniques that were applied were regression, correlation and Cronbach alpha analysis. The findings that were obtained through regression and correlation illustrated a positive impact between the independent and the dependent variables. Keywords: Carbon Capture and Utilization, Awareness, Acceptance, Perception, Emissions, Greenhouse Gases, Emissions Reduction, Emissions Mitigation. DOI: 10.7176/CER/12-2-07 Publication date: February 29 th 2020

The contribution to exogenic CO2 by contact metamorphism at continental arcs: A coupled model of fluid flux and metamorphic decarbonation

Recent work has suggested a possible temporal coincidence between greenhouse intervals and enhanced arc volcanism, motivating the hypothesis that magmatic and metamorphic CO₂ emissions from volcanic arcs, particularly those intersecting crustal carbonates, may play a strong role in modulating the long-term carbon budget of the exogenic system. When hot fluid exsolving from arc magmas interacts with carbonate sequences on active margins, contact metamorphism releases CO₂ to metasomatic fluids that transport carbon to shallow reservoirs. To estimate the magnitude of CO₂ release, here we model how the infiltration of silica-saturated magmatic water into a porous medium facilitates the decarbonation reaction in contact aureoles. Analytical scalings and numerical simulations show that the propagation rate of the reaction front scales with the ratio of the infiltration flux to the mass of the rate-limiting reactant, and accordingly the CO₂ flux increases linearly with the infiltration flux. This simple relationship allows for scaling to predict regional and global scale CO₂ release at continental arcs if magma emplacement rate is known. Using the global rate of continental arc magma emplacement, we estimate that the present-day contact-metamorphic CO₂ release range from ∼0.06 to 0.9 Tmol/yr, half-to-one orders of magnitude smaller than the field-based estimates of carbon output in modern arcs (1.5–3.5 Tmol/yr). Yet, the extrapolated CO₂ release from Cretaceous continental arcs via simple infiltration-induced decarbonation is comparable to the release from mid-ocean ridges. CO₂ released from continental arcs amplifies the background flux of CO₂ from direct degassing of the magma, and therefore may have been key in causing the climatic greenhouse interval in the Cretaceous when there was heightened arc activity. Thus, our result supports the hypothesis that global arc flare-ups at continental margins effectively increase CO₂ outgassing coinciding with green-house intervals in the geological past. The contribution by arcs to the tectonic CO₂ input could be significant, which needs field-based studies to revise long-term climate models.

Atmospheric columnar CO<sub>2</sub> enhancement over E. huxleyi blooms : case studies in the North Atlantic and Arctic waters

Blooms of a coccolithophore E. huxleyi are generally huge, occur annually and in the oceans of both Hemispheres. As a calcifying algal species, E. huxleyi is known to enhance the partial pressure of dissolved CO 2 in surface ocean, thus reducing its ability to absorb atmospheric CO 2 . Here we report on the results of our satellite study of CO 2 enhancement in the atmospheric column over E. huxleyi blooms in the North, Greenland, Iceland and Barents seas. The study is based on OCO-2 data, wind force and direction, and E. huxleyi bloom masks developed by us earlier. Eight case studies are discussed herein relating to the time period 2015-2018. The results obtained are strongly indicative that indeed the phenomenon of E. huxleyi blooms noticeably affect the carbon fluxes between the atmosphere and the surface ocean: the quantified enhancement of CO 2 content in the atmospheric column over the bloom area in the six case studies proved to be in the range 0.6 -3.0 ppm. It is also shown that the magnitude of CO 2 enhancement in the atmospheric column is significantly controlled by the air advection in the boundary layer.

Potentiometric CO sensors using anion-conducting polymer electrolyte: Effects of the kinds of noble metal-loaded metal oxides as sensing-electrode materials on CO-sensing properties

Potentiometric CO-sensing properties of electrochemical gas sensors using an anion-conducting polymer as an electrolyte and a metal oxide (MO; Bi2O3, CeO2, In2O3, SnO2, or V2O5) loaded with or without 2.0 wt% noble metal (N; Ag, Au, Ir, Ru, Rh, Pd, or Pt) as an electrode material (EC(N/MO) or (EC(MO) sensor; N/MO: N-loaded MO) were investigated in wet synthetic air (57%RH) at 30 °C. Among all the EC(MO) sensors, the EC(CeO2) sensor showed the largest CO response and excellent CO selectivity against H2 and the EC(Bi2O3) sensor showed relatively large CO and H2 responses (no CO selectivity against H2). Other EC(MO) sensors hardly showed both CO and H2 responses. However, the Au loading just onto In2O3 and SnO2 was effective in improving the magnitude of CO and H2 responses of the EC(In2O3) and EC(SnO2) sensors, respectively, which resulted in relatively poor CO selectivity against H2. On the other hand, the Pt loading only onto SnO2 extremely enhanced only the magnitude of CO response of the EC(SnO2) sensor, and thus the EC(Pt/SnO2) sensor showed the most excellent CO selectivity against H2, among all the sensors in this study. The heat treatment of N/MO powders in H2 at 250 °C reduced only the H2 response of the EC(Au/SnO2) sensor, leading to an improvement of the CO selectivity of only the EC(Au/SnO2) sensor against H2. On the other hand, the heat treatment drastically enhanced both CO and H2 responses of the EC(Pt/SnO2) sensor, resulting in a decrease in its CO selectivity against H2. The CO and H2 responses of other EC(N/SnO2) sensors before and after the heat treatment in H2 at 250 °C were also examined, and the effectiveness of the noble metal loading and the heat treatment on the CO-sensing properties was discussed in this study. In addition, gas-sensing mechanism was also proposed on the basis of chemical surface states of representative N/MO.

Seasonal and daily variability of CO2 emissions from the Czerwone Bagno peat bog in Biebrza National Park (Poland)

The article describes the results of field studies carried out in the period from April 2013 to May 2014. The study concerned the assessment of the magnitude of CO 2 emissions from marsh soils in the area of Czerwone Bagno (Red Swamp), which is a part of the largest complex of marsh in Poland. The authors used the closed chamber method to measure seasonal variability of net ecosystem CO 2 emission and drew attention to the impact of environmental factors (air temperature, air pressure and soil moisture) on it. The highest values of average daily CO 2 emission (over 630 mg(CO2)×m –2 ×h –1 ) were recorded in late spring and summer. Lowest values were obtained in late autumn and winter (in the range of 178-212 mg(CO2)×m –2 ×h –1 ). The need for monitoring of wetlands in temperate latitudes is stressed due to the progressive process of wetlands drying which enables the release of large quantities of greenhouse gases – CO 2 , CH 4 – into the atmosphere.

Effect of CO2 on hydrogen absorption in Ti-Zr-Mn-Cr based AB2 type alloys

Abstract The effect of CO 2 on hydrogen absorption has been investigated for AB 2 type alloys of Ti 0.515 Zr 0.485 Mn 1.2 Cr 0.8 (Ti-Zr-Mn-Cr) and Ti 0.515 Zr 0.485 Mn 1.2 Cr 0.8 M 0.1 (Ti-Zr-Mn-Cr-M, M = Fe, Co, or Ni) in order to develop metal hydrides for a hydrogen purification and storage system. A magnitude of CO 2 poisoning tolerance was evaluated by comparing hydrogen absorption properties before and after CO 2 exposure. As the results, an order of CO 2 tolerance was Ti-Zr-Mn-Cr-Ni 2 alloys have dependence of additive 3d-transition elements on CO 2 tolerance. Ti-Zr-Mn-Cr-Fe has the highest CO 2 tolerance among them. The additive of Fe and Co improves tolerance of CO 2 poisoning for hydrogen absorption properties. On the other hand, Ni element in AB 2 alloy decreases CO 2 tolerance. The estimated enthalpy change between CO 2 and the alloys surface was comparable to the formation of metal oxide. And the CO 2 -exposed AB 2 alloys after reacting with hydrogen desorbed methane gas. Therefore, CO 2 would dissociate to CO and O on the surface of alloys, and then oxygen atom reacts with the alloys.

Impact of forest fires, biogenic emissions and high temperatures on the elevated Eastern Mediterranean ozone levels during the hot summer of 2007

Abstract. The hot summer of 2007 in southeast Europe has been studied using two regional atmospheric chemistry models; WRF-Chem and EMEP MSC-W. The region was struck by three heat waves and a number of forest fire episodes, greatly affecting air pollution levels. We have focused on ozone and its precursors using state-of-the-art inventories for anthropogenic, biogenic and forest fire emissions. The models have been evaluated against measurement data, and processes leading to ozone formation have been quantified. Heat wave episodes are projected to occur more frequently in a future climate, and therefore this study also makes a contribution to climate change impact research. The plume from the Greek forest fires in August 2007 is clearly seen in satellite observations of CO and NO2 columns, showing extreme levels of CO in and downwind of the fires. Model simulations reflect the location and influence of the fires relatively well, but the modelled magnitude of CO in the plume core is too low. Most likely, this is caused by underestimation of CO in the emission inventories, suggesting that the CO/NOx ratios of fire emissions should be re-assessed. Moreover, higher maximum values are seen in WRF-Chem than in EMEP MSC-W, presumably due to differences in plume rise altitudes as the first model emits a larger fraction of the fire emissions in the lowermost model layer. The model results are also in fairly good agreement with surface ozone measurements. Biogenic VOC emissions reacting with anthropogenic NOx emissions are calculated to contribute significantly to the levels of ozone in the region, but the magnitude and geographical distribution depend strongly on the model and biogenic emission module used. During the July and August heat waves, ozone levels increased substantially due to a combination of forest fire emissions and the effect of high temperatures. We found that the largest temperature impact on ozone was through the temperature dependence of the biogenic emissions, closely followed by the effect of reduced dry deposition caused by closing of the plants' stomata at very high temperatures. The impact of high temperatures on the ozone chemistry was much lower. The results suggest that forest fire emissions, and the temperature effect on biogenic emissions and dry deposition, will potentially lead to substantial ozone increases in a warmer climate.

Carbon dioxide and the uneasy interactions of trees and savannah grasses.

Savannahs are a mixture of trees and grasses often occurring as alternate states to closed forests. Savannah fires are frequent where grass productivity is high in the wet season. Fires help maintain grassy vegetation where the climate is suitable for woodlands or forests. Saplings in savannahs are particularly vulnerable to topkill of above-ground biomass. Larger trees are more fire-resistant and suffer little damage when burnt. Recruitment to large mature tree size classes depends on sapling growth rates to fire-resistant sizes and the time between fires. Carbon dioxide (CO(2)) can influence the growth rate of juvenile plants, thereby affecting tree recruitment and the conversion of open savannahs to woodlands. Trees have increased in many savannahs throughout the world, whereas some humid savannahs are being invaded by forests. CO(2) has been implicated in this woody increase but attribution to global drivers has been controversial where changes in grazing and fire have also occurred. We report on diverse tests of the magnitude of CO(2) effects on both ancient and modern ecosystems with a particular focus on African savannahs. Large increases in trees of mesic savannahs in the region cannot easily be explained by land use change but are consistent with experimental and simulation studies of CO(2) effects. Changes in arid savannahs seem less obviously linked to CO(2) effects and may be driven more by overgrazing. Large-scale shifts in the tree-grass balance in the past and the future need to be better understood. They not only have major impacts on the ecology of grassy ecosystems but also on Earth-atmosphere linkages and the global carbon cycle in ways that are still being discovered.

Surface heat flow and CO2 emissions within the Ohaaki hydrothermal field, Taupo Volcanic Zone, New Zealand

Abstract Carbon dioxide emissions and heat flow have been determined from the Ohaaki hydrothermal field, Taupo Volcanic Zone (TVZ), New Zealand following 20 a of production (116 MW e ). Soil CO 2 degassing was quantified with 2663 CO 2 flux measurements using the accumulation chamber method, and 2563 soil temperatures were measured and converted to equivalent heat flow (W m −2 ) using published soil temperature heat flow functions. Both CO 2 flux and heat flow were analysed statistically and then modelled using 500 sequential Gaussian simulations. Forty subsoil CO 2 gas samples were also analysed for stable C isotopes. Following 20 a of production, current CO 2 emissions equated to 111 ± 6.7 T/d. Observed heat flow was 70 ± 6.4 MW, compared with a pre-production value of 122 MW. This 52 MW reduction in surface heat flow is due to production-induced drying up of all alkali–Cl outflows (61.5 MW) and steam-heated pools (8.6 MW) within the Ohaaki West thermal area (OHW). The drying up of all alkali–Cl outflows at Ohaaki means that the soil zone is now the major natural pathway of heat release from the high-temperature reservoir. On the other hand, a net gain in thermal ground heat flow of 18 MW (from 25 MW to 43.3 ± 5 MW) at OHW is associated with permeability increases resulting from surface unit fracturing by production-induced ground subsidence. The Ohaaki East (OHE) thermal area showed no change in distribution of shallow and deep soil temperature contours despite 20 a of production, with an observed heat flow of 26.7 ± 3 MW and a CO 2 emission rate of 39 ± 3 T/d. The negligible change in the thermal status of the OHE thermal area is attributed to the low permeability of the reservoir beneath this area, which has limited production (mass extraction) and sheltered the area from the pressure decline within the main reservoir. Chemistry suggests that although alkali–Cl outflows once contributed significantly to the natural surface heat flow (∼50%) they contributed little ( 2 emissions due to the loss of >99% of the original CO 2 content due to depressurisation and boiling as the fluids ascended to the surface. Consequently, the soil has persisted as the major (99%) pathway of CO 2 release to the atmosphere from the high temperature reservoir at Ohaaki. The CO 2 flux and heat flow surveys indicate that despite 20 a of production the variability in location, spatial extent and magnitude of CO 2 flux remains consistent with established geochemical and geophysical models of the Ohaaki Field. At both OHW and OHE carbon isotopic analyses of soil gas indicate a two-stage fractionation process for moderate-flux (>60 g m −2 d −1 ) sites; boiling during fluid ascent within the underlying reservoir and isotopic enrichment as CO 2 diffuses through porous media of the soil zone. For high-flux sites (>300 g m −2 d −1 ), the δ 13 CO 2 signature (−7.4 ± 0.3‰ OHW and −6.5 ± 0.6‰ OHE) is unaffected by near-surface (soil zone) fractionation processes and reflects the composition of the boiled magmatic CO 2 source for each respective upflow. Flux thresholds of −2 d −1 for purely diffusive gas transport, between 30 and 300 g m −2 d −1 for combined diffusive–advective transport, and ⩾300 g m −2 d −1 for purely advective gas transport at Ohaaki were assigned. δ 13 CO 2 values and cumulative probability plots of CO 2 flux data both identified a threshold of ∼15 g m −2 d −1 by which background (atmospheric and soil respired) CO 2 may be differentiated from hydrothermal CO 2 .

Electronic structure, magnetism, and spin fluctuations in the superconducting weak ferromagnetY4Co3

Results of the first principles study on the electronic structure and magnetism of the superconducting weak ferromagnet Y$_4$Co$_3$, are presented. Using the full potential Korringa-Kohn-Rostoker (FP-KKR) method, densities of states, dispersion curves and magnetic moments were calculated for quasi-ordered structural model of the compound in the framework of the local density approximation. Spin-polarized KKR calculations confirm that weak ferromagnetic properties of Y$_4$Co$_3$ can be attributed to only one cobalt atom located on (2b) site in the unit cell, while other twenty Co and Y atoms acts as a diamagnetic environment. Moreover, the magnetic Co atoms form a quasi-one-dimensional chains along $z$ direction. The magnitude of Co(2b) magnetic moment ($0.55~\mu_B$) markedly overestimates the experimental value (0.23~$\mu_B$), which suggests the importance of spin fluctuations in this system. Calculated distribution of spin magnetization in the unit cell provides a background for discussion of the coexistence of ferromagnetism and superconductivity in Y$_4$Co$_3$. Finally, the effect of pressure on magnetism is discussed and compared with experimental data, also supporting weak ferromagnetic behaviors in the system.

Generation of carbon dioxide from glycerol: Evidences of massive production on polycrystalline platinum

In this work we investigate the glycerol electrooxidation reaction on polycrystalline platinum in acid media. Cyclic voltammetry shows the existence of multiple oxidation peaks, which are related with a complex electrooxidation mechanism. We follow the voltammetric response of Pt in the presence of glycerol by using FTIR in situ. Results show that during glycerol electrooxidation massive amounts of CO 2 are produced. The production of CO 2 begins at low potentials and depends on the previous formation of adsorbed CO. This pathway is accelerated at high potentials and seems to be the main responsible for the rising of the currents observed in the cyclic voltammogram for potentials up to 1.0 V. Moreover, there is a parallel pathway involving the production of a carboxylic acid (probably glyceric acid), but the relative magnitudes of CO 2 bands and acid bands makes clear that the production of CO 2 is the dominant feature of the spectra, suggesting that glycerol can be a suitable candidate for use in direct alcohol fuel cells.

Carbon dioxide and methane fluxes in the littoral zones of two lakes, east Antarctica

During the summertime of 2007/2008, carbon dioxide (CO 2) and methane (CH 4) fluxes across air–water interface were investigated in the littoral zones of Lake Mochou and Lake Tuanjie, east Antarctica, using a static chamber technique. The mean fluxes of CO 2 and CH 4 were −70.8 mgCO 2 m −2 h −1 and 144.6 μgCH 4 m −2 h −1, respectively, in the littoral zone of Lake Mochou; The mean fluxes were −36.9 mgCO 2 m −2 h −1 and 109.8 μgCH 4 m −2 h −1, respectively, in the littoral zone of Lake Tuanjie. Their fluxes showed large temporal and spatial dynamics. The CO 2 fluxes showed a significantly negative correlation with daily total radiation (DTR) and a weakly negative correlation with air temperature and water temperature, indicating that sunlight intensity controlled the magnitude of CO 2 fluxes from the open lakes. The CH 4 fluxes significantly correlated with local air temperature, water table and total dissolved solids (TDS), indicating that they were the predominant factors influencing CH 4 fluxes. Summertime CO 2 budgets in the littoral zones of Lake Mochou and Lake Tuanjie were estimated to be −152.9 gCO 2 m −2 and −79.7 gCO 2 m −2, respectively, and net CH 4 emissions were estimated to be 312.3 mgCH 4 m −2 and 237.2 mgCH 4 m −2, respectively. Our results show that shallow, open, alga-rich lakes might be strong summertime CO 2 absorbers and small CH 4 emitters during the open water in coastal Antarctica.

Soil CO 2 efflux and extractable organic carbon fractions under simulated precipitation events in a Mediterranean Dehesa

The magnitude of CO 2 efflux pulses after rewetting a dry soil is highly variable and the factors regulating these pulses are poorly understood. In this field experiment, we aimed to study the C dynamics after simulated summer rainstorms in a Mediterranean open holm oak woodland ( dehesa). We hypothesized that because the herbaceous cover is mostly dead during the summer in this ecosystem, the short-term CO 2 efflux (SR) after rewetting could mainly be explained by different measurable soil C fractions: i) K 2SO 4-extracted soil C (EOC); ii) microbial biomass C (MBC); or iii) chloroform-fumigated extracted C (CFE). On both grazed and abandoned dehesa sites, we simulated three summer rain events at two-week intervals and we measured SR discontinuously in three plots under tree canopy and in another three plots in open grassland. In each plot, C fractions and water content were estimated before (2 h) and after (36 h) each irrigation event. Following rewettings, SR increased up to ten times compared with non-irrigated plots. The CFE actually increased after rewetting in the first two irrigations but not in the third event, suggesting that the capacity of the soil to release labile organic C from soil aggregates or litter was reduced after each irrigation event. Overall, the C released as CO 2 in the first 24 h was related to the CFE existing before rewetting, which may help to explain the spatial variability in SR. However, the explained variability decreased after each irrigation, suggesting a change to a less labile composition of the CFE fraction as a consequence of multiple drying-rewetting cycles.

Effect of macrostructural control of an auxiliary layer on the CO 2 sensing properties of NASICON-based gas sensors

Macrostructural effects of an auxiliary electrode on the CO 2 gas sensing properties of NASICON (Na 3Zr 2Si 2PO 12) solid-electrolyte sensors were investigated. The sensor with a porous Li 2CO 3–BaCO 3-based auxiliary layer (mp-Sensor), which was prepared by utilizing constituent metal acetates and polymethylmethacrylate microspheres as a template, showed faster CO 2 response and recovery and smaller cross-response against humidity changes than those obtained with a dense auxiliary layer without pores (d-Sensor). The magnitude of CO 2 response of mp-Sensor was slightly larger than the theoretical one, probably due to the existence of impurities which might have reacted with CO 2 in the auxiliary layer. On the other hand, c-Sensor with a thicker and dense auxiliary layer, which was prepared by commercially available carbonates, showed smaller CO 2 response and larger cross-response to humidity than mp-Sensor and d-Sensor. Thus, the use of the porous auxiliary layer prepared by constituent metal acetates was confirmed to be effective for improving the CO 2 sensing properties along with the large CO 2 response and small cross-response to humidity.

Adsorption separation of carbon dioxide, methane, and nitrogen on Hβ and Na-exchanged β-zeolite

Adsorption isotherms of carbon dioxide (CO 2), methane (CH 4), and nitrogen (N 2) on Hβ and sodium exchanged β-zeolite (Naβ) were volumetrically measured at 273 and 303 K. The results show that all isotherms were of Brunauer type I and well correlated with Langmuir-Freundlich model. After sodium ions exchange, the adsorption amounts of three adsorbates increased, while the increase magnitude of CO 2 adsorption capacity was much higher than that of CH 4 and N 2. The selectivities of CO 2 over CH 4 and CO 2 over N 2 enhanced after sodium exchange. Also, the initial heat of adsorption data implied a stronger interaction of CO 2 molecules with Na + ions in Naβ. These results can be attributed to the larger electrostatic interaction of CO 2 with extraframework cations in zeolites. However, Naβ showed a decrease in the selectivity of CH 4 over N 2, which can be ascribed to the moderate affinity of N 2 with Naβ. The variation of isosteric heats of adsorption as a function of loading indicates that the adsorption of CO 2 in Naβ presents an energetically heterogeneous profile. On the contrary, the adsorption of CH 4 was found to be essentially homogeneous, which suggests the dispersion interaction between CH 4 and lattice oxygen atoms, and such interaction does not depend on the exchangeable cations of zeolite.

CO2 efflux, CO2 concentration and photosynthetic refixation in stems of Eucalyptus globulus (Labill.)

In spite of the importance of respiration in forest carbon budgets, the mechanisms by which physiological factors control stem respiration are unclear. An experiment was set up in a Eucalyptus globulus plantation in central Portugal with monoculture stands of 5-year-old and 10-year-old trees. CO(2) efflux from stems under shaded and unshaded conditions, as well as the concentration of CO(2) dissolved in sap [CO(2)(*)], stem temperature, and sap flow were measured with the objective of improving our understanding of the factors controlling CO(2) release from stems of E. globulus. CO(2) efflux was consistently higher in 5-year-old, compared with 10-year-old, stems, averaging 3.4 versus 1.3 mumol m(-2) s(-1), respectively. Temperature and [CO(2)(*)] both had important, and similar, influences on the rate of CO(2) efflux from the stems, but neither explained the difference in the magnitude of CO(2) efflux between trees of different age and size. No relationship was found between efflux and sap flow, and efflux was independent of tree volume, suggesting the presence of substantial barriers to the diffusion of CO(2) from the xylem to the atmosphere in this species. The rate of corticular photosynthesis was the same in trees of both ages and only reduced CO(2) efflux by 7%, probably due to the low irradiance at the stem surface below the canopy. The younger trees were growing at a much faster rate than the older trees. The difference between CO(2) efflux from the younger and older stems appears to have resulted from a difference in growth respiration rather than a difference in the rate of diffusion of xylem-transported CO(2).

Adsorption kinetics of CO2, CH4, and their equimolar mixture on coal from the Black Warrior Basin, West-Central Alabama

Abstract Laboratory experiments were conducted to investigate the adsorption kinetic behavior of pure and mixed gases (CO 2, CH 4 , approximately equimolar CO 2 + CH 4 mixtures, and He) on a coal sample obtained from the Black Warrior Basin at the Littleton Mine (Twin Pine Coal Company), Jefferson County, west-central Alabama. The sample was from the Mary Lee coal zone of the Pottsville Formation (Lower Pennsylvanian). Experiments with three size fractions (45–150 µm, 1–2 mm, and 5–10 mm) of crushed coal were performed at 40 °C and 35 °C over a pressure range of 1.4–6.9 MPa to simulate coalbed methane reservoir conditions in the Black Warrior Basin and provide data relevant for enhanced coalbed methane recovery operations. The following key observations were made: (1) CO 2 adsorption on both dry and water-saturated coal is much more rapid than CH 4 adsorption; (2) water saturation decreases the rates of CO 2 and CH 4 adsorption on coal surfaces, but it appears to have minimal effects on the final magnitude of CO 2 or CH 4 adsorption if the coal is not previously exposed to CO 2 ; (3) retention of adsorbed CO 2 on coal surfaces is significant even with extreme pressure cycling; and (4) adsorption is significantly faster for the 45–150 μm size fraction compared to the two coarser fractions.

Environmental effects on net ecosystem CO 2 exchange at half-hour and month scales over Stipa krylovii steppe in northern China

The objectives of this research are to quantify the magnitude of CO 2 exchange and to investigate the responses of net ecosystem CO 2 exchange (NEE), gross ecosystem production (GEP) and ecosystem respiration ( R e) to environmental factors over a temperate Stipa krylovii steppe by an eddy covariance system in northern China. Differences in annual precipitation, soil water content (SWC), air temperature ( T a) and evapotranspiration (ET) were the most important factors which controlled patterns and variations of CO 2 exchange between atmosphere and the steppe. Precipitation received at study site was 297 mm in 2004, close to the average value during 1971–2000 (±S.D., 290 ± 82 mm), whereas precipitations in 2005 (174 mm) and 2006 (215 mm) were significantly below the average. The lowest values of precipitation and SWC in 2005 resulted in much lower carbon exchange rate related to those in 2004 and 2006. In 2005, daytime NEE reached the seasonal peak about −3 μmol C m −2 s −1, this was much lower than those in 2004 and 2006 (−7 to −8 μmol C m −2 s −1). Seasonal peaks of integrated monthly NEE was the lowest in 2005 (−8.8 g C m −2 mon −1) and the highest in 2004 (−34.3 g C m −2 mon −1). Compared with 2004, the peak values of monthly GEP and R e in 2005 reduced more than 30% and 20% due to soil water stress. SWC was an important environmental factor regulated the variation of CO 2 exchange. At hour time scale, daytime NEE was positive when SWC was less than 0.15 m 3 m −3, R e tripled when SWC increased from 0.075 to 0.225 m 3 m −3. At month time scale, SWC was the primary factor controlling monthly CO 2 fluxes, there was no net carbon uptake until SWC exceeded 18%, in the low (LAI < 0.5 m 2 m −2) and the high (LAI > 0.5 m 2 m −2) ranges of LAI, SWC explained about 71% and 90% variations in monthly NEE, and about 92% and 82% variations in monthly GEP. Except SWC, NEE–light response curve was also regulated by air temperature because it influenced both plant photosynthetic capacity and the variations of soil and plant respirations. The optimal air temperature for the carbon uptake of S. krylovii steppe was 10–20 °C, carbon uptake decreased in magnitude when air temperature departed from this range. The close relationship between ET and CO 2 fluxes was explained that ET was determined by both SWC and T a. At monthly scale, ET predicted 62% variations of NEE, 78% variations of GEP, 85% variations of R e. Accumulative ET and accumulative NEE in growing seasons were tightly coupled. The highest ET coincided with carbon sink in the growing season of 2006, and the lowest ET in 2005 resulted in the maximum carbon loss.

Eddy covariance measurements of hydrothermal heat flux at Solfatara volcano, Italy

The first measurements of volcanic/hydrothermal water vapor and heat flux using eddy covariance (EC) were made at Solfatara crater, Italy, June 8–25, 2001. Deployment at six different locations within the crater allowed areas of focused gas venting to be variably included in the measured flux. Turbulent (EC) fluxes of water vapor varied between 680 and 11 200 g H 2O m − 2 d − 1 . Heat fluxes varied diurnally with the solar input, and the volcanic component of sensible heat ranged from ∼25 to 238 W m − 2 . The highest measurements of both sensible and latent heat flux were made downwind of hot soil regions and degassing pools and during mid-day. The ratio of average volcanic heat (both latent and sensible) to CO 2 flux resulted in an equivalent H 2O/CO 2 flux ratio of 2.2 by weight, which reflects the deep source H 2O/CO 2 gas ratio. The amount latent heat flux/evaporation was determined to be consistent both with what would be expected from the magnitude of CO 2 fluxes and the fumarolic H 2O/CO 2 ratio, as well as with observed surface temperatures and wind speeds given a moist soil. This suggests that the water vapor that condenses in the shallow subsurface is remobilized at the soil–atmosphere interface through variable evaporation dependent on the deep heat flux and surface temperature. The results suggest that EC provides a quick and easy method to monitor average H 2O/CO 2 ratios continuously in volcanic regions, providing another important tool for volcanic hazards monitoring.

Effect of clearcuts on footprints and flux measurements above a forest canopy

A two-equation model based on transport equations of turbulent kinetic energy ( E) and specific dissipation ( ω) ( E– ω model) is used to investigate both the footprint and the effect of surface heterogeneities on flux measurements. The present study examines the influence of a model bare soil patch located upwind of the eddy-covariance tower on fluxes in a managed forest plantation. Using as a testbed measured flow statistics in the managed pine plantation of the Florida AmeriFlux site, scalar fluxes from a clearcut–forest transect with swaths of logged land of dimensions varying with wind direction were modeled. In sharp contrast with momentum fluxes, the magnitude of CO 2 and scalar fluxes is found to be sensitive to clearcut widths. The adjustment to new underlying scalar flux values as a function of distance from the forest leading edge appears to be far greater for scalar fluxes than for momentum fluxes. This result is consistent for all modeled clearcut swaths–forest canopy interfaces, suggesting that CO 2 flux measurements using the eddy-covariance technique require a larger fetch for forest flux towers than previously thought. The present footprint analysis indicates flux contributions from the clearcut, forest floor, and forest canopy to the tower flux hundreds of meters downwind of the clearcut–forest interface and highlights the need for caution in the interpretation of data away from the leading forest edge (up to 30 canopy heights). This is specially true when the strength of both surface and in-canopy sources are of comparable magnitude. Furthermore, depending on the geometry of the surface heterogeneity, results from this study suggest that aerodynamic parameters characterizing vegetation, such as displacement height and roughness length, can be a function of both distance from the clearcut and the clearcut's dimensions with respect to wind direction. Such parameters, when derived from flow information collected at the flux tower downwind of a bare soil patch–forest interface, cannot be used as specific parameters for the vegetation stand studied until the flux has reached equilibrium with the underlying surface. This study also suggests that, to improve our current assessment of net carbon uptake, attention should be given to the importance of careful tower location selection in a landscape characterized by a mosaic of surface properties as observed in a managed forest plantation or in most natural ecosystems.