Carbon Dioxide Variations Research Articles

Gasification of Some Locally Available Biomass using a Downdraft Gasifier

The ever-increasing price of fossil fuels and the rising environmental concern have encouraged the use of biomass as energy sources. Gasification is a simple and highly efficient method for converting biomass energy into fuel. In the present work, gasification of some locally available woody and non-woody biomass in Assam has been done. Proximate analysis is used to give the composition of the biomass in terms of gross components such as moisture, volatile matter, ash and fixed carbon. Thermo-chemical equilibrium modelling is performed and the variation of gas composition, namely, hydrogen, carbon dioxide, carbon monoxide, methane and nitrogen, with moisture content (0–20%) is studied for all the samples of biomass at a temperature of 850°C. It is found that nitrogen has the highest content at0% weight basis and methane has the lowest for the same composition. It is found that the composition of hydrogen and carbon dioxide in the fuel gas increases continuously with the moisture content. On the other hand, the percentage of carbon monoxide reduces for the same variation of moisture content. The composition of methane and the inert nitrogen is almost constant with moisture content. The results obtained are also compared with the existing commercially available biomass sources.

Open and Closed Endotracheal Suctioning and Arterial Blood Gas Values: A Single-Blind Crossover Randomized Clinical Trial.

Aim. This study was aimed at comparing the effects of the open and closed suctioning techniques on the arterial blood gas values in patients undergoing open-heart surgery. Methods. In a clinical trial, we recruited 42 patients after open-heart surgery in an educational hospital. Each patient randomly underwent both open and closed suctioning. ABGs, PaO2, SaO2, PaCO2, were analyzed before and one, five, and fifteen minutes after each suctioning episode. Results. At first the pressure of oxygen in arterial blood increased; however, this increase in the open technique was greater than that of the closed system (P < 0.001). The pressure of oxygen decreased five and fifteen minutes after both suctioning techniques (P < 0.05). The trends of carbon dioxide variations after the open and closed techniques were upward and downward, respectively. Moreover, the decrease in the level of oxygen saturation five and fifteen minutes after the open suctioning was greater than that of the closed suctioning technique (P < 0.05). Conclusion. Arterial blood gas disturbances in the closed suctioning technique were less than those of the open technique. Therefore, to eliminate the unwanted effects of endotracheal suctioning on the arterial blood gases, the closed suctioning technique is recommended.

Carbon and Water Footprints and Energy Use of Greenhouse Tomato Production in Northern Italy

SummaryThis study reports on the carbon, water, and energy footprints of tomatoes grown in a greenhouse in Northern Italy and two possible future variations of heating and carbon dioxide (CO2) fertilization on the current setup. The heat supply in place, consisting of natural gas (NG) and canola oil combustion, is compared to cogeneration and incineration of municipal solid waste for heating and CO2 from industrial exhaust for fertilization. As a benchmark, the current system is also compared to a conventional system, in which heat is delivered solely based on NG. Each kilogram (kg) of fresh tomatoes (“Cuore di Bue” variety) produced in the current greenhouse emits 2.28 kg CO2 equivalents (eq) and uses 95.5 megajoules (MJ) eq energy and 122 liters (L) of water. Relative to the system in place, the carbon footprint (CF) is 57.5% and 18% higher with conventional NG heating and cogeneration and is 40% lower with waste valorization. Further, 33%, 55%, and 63% less energy and 9%, 96%, and 14% less water are used in the conventional, cogeneration, and waste valorization scenarios, respectively. This confirms that there are multiple strategies to reduce the impact of the tomato production under consideration.

Spatial and temporal variations in carbon dioxide (CO2) concentrations in selected soils of the Moravian Karst (Czech Republic)

The evolution of CO2 concentrations in selected soils of the Moravian Karst (Czech Republic) was studied during a 1-year period from August 2008 to July 2009. CO2 concentrations directly measured in air of the soils of coniferous and deciduous forests reached up to 0.5 vol%. Substantially, higher CO2 concentrations, over 1 vol%, were found in thicker sinkhole soils under grassy vegetation. CO2 concentrations showed strong seasonality with maxima in summer and minima in winter at all sites. On the basis of temperature dependence, \( \ln c_{{{\text{CO}}_{ 2} }} = b_{0} - b_{1} /T \) (where \(c_{{{\text{CO}}_{ 2} }}\) is CO2 concentration in mol/L, T is temperatures in Kelvin, and b 1, b 2 are constants); all CO2 concentrations were normalized to 10 °C. These concentrations did not correlate with rainfall or soil profile depth. The remaining maxima in the time series of CO2 concentrations (a sharp peak especially in July) might be the result of increased plant respiration during enhanced photosynthesis activity during the early-summer stage of the green period.

Spatio-temporal variations of carbon dioxide and its gross emission regulated by artificial operation in a typical hydropower reservoir in China

Supersaturation and excess emission of greenhouse gases in freshwater reservoirs have received a great deal of attention in recent years. Although impoundment of reservoirs has been shown to contribute to the net emission of greenhouse gases, reservoir age, geographical distribution, submerged soil type and artificial regulation also have a great impact on their emissions. To examine how large scale reservoir operation impact the water column CO2 and its air-water interface flux, a field study was conducted in 2010 to evaluate potential ecological processes that regulate the partial pressure of CO2 (pCO2) in the water column in the Pengxi River backwater area (PBA), a typical tributary in the Three Gorges Reservoir, China. Measurements of total alkalinity (TA), pH and water temperature were applied to compute the pCO2. And this approach was also validated by calculation of pCO2 from the dissolved inorganic carbon data of samples. Partial least squares (PLS) regression was used to determine how the dynamics of the water pCO2 were related to the available variables. The estimated pCO2 in our sample ranged from 26 to 4,087 μatm in the surface water. During low water operation from July to early September, there was an obvious pCO2 stratification, and pCO2 in the surface was almost unsaturated. This phenomenon was also observed in the spring bloom during discharge period. Conversely, there was no significant pCO2 stratification and the entire water column was supersaturated during high water operation from November to the following February. Significant correlation was observed between the magnitude of pCO2, DO and chlorophyll a, suggesting that phytoplankton dynamics regulate pCO2 in the PBA. The average areal rate of CO2 emissions from the Pengxi River ranged from 18.06 to 48.09 mmol m(-2) day(-1), with an estimated gross CO2 emission from the water surface of 14-37 t day(-1) in this area in 2010. Photosynthesis and respiration rates by phytoplankton might be the dominant processes that regulated pCO2 in the water column. We conclude that pCO2 values in the surface water of Pengxi River could be regarded as potential sources of CO2 to the atmosphere were smaller or similar to those that have been reported for many other reservoirs to date.

Atmospheric CO2 Variations in Two Contrasting Environmental Sites Over India

We analyzed the influence of environmental parameters on the temporal variation of atmospheric carbon dioxide (CO2) mixing ratios in two environmentally contrasting Indian sites, Dehradun (30.1°N, 77.4°E, humid subtropical station) and Gadanki (13.5°N, 79.18°E, dry tropical station), from October 2010 to September 2011. The annual range of mixing ratios is low in Gadanki as compared to those of Dehradun because of relatively less monthly variation in temperature and relative humidity (RH) at Gadanki. At both the stations, the minimum mixing ratios are present during the high ecosystem productivity seasons in the afternoon hours. The maximum values are in the early morning hours. However, low wind speed conditions control the unexpected afternoon high mixing ratios in Gadanki during the pre-monsoon season. The early morning maximum is high during monsoon and post-monsoon seasons in Dehradun and Gadanki, respectively, whereas morning inflexion occurred earlier in Gadanki compared with Dehradun. The effect of cloudiness on the CO2 uptake depends on the canopy cover.

Seasonal Variations of CO&lt;sub&gt;2&lt;/sub&gt;, CH&lt;sub&gt;4&lt;/sub&gt;, N&lt;sub&gt;2&lt;/sub&gt;O and CO in the Mid-Troposphere over the Western North Pacific Observed Using a C-130H Cargo Aircraft

Seasonal variations of carbon dioxide (CO2), methane (CH4), carbon monoxide (CO), and nitrous oxide (N2O), in the mid-troposphere over the western North Pacific, are investigated using air samples collected onboard a C-130H aircraft. These samples were obtained between Atsugi Base (35.45°N, 139.45°E) and Minamitorishima (MNM; 24.28°N, 153.98°E), once a month, from September 2010 to September 2012. Increasing trends of CO2 and N2O and large variability of CH4 and CO (at approximately 6 km) have been found. During summer, concentrations of CH4 and CO were found to increase with height over MNM. High concentrations of CH4 were persistently observed in the mid-troposphere throughout the observation period. The average enhancement ratios of CH4 to CO above background levels (ΔCH4/ΔCO) were 0.47 and 1.2 ppb/ppb for winter-spring and summer-fall, respectively. The results suggested that the high CH4 concentrations originated primarily from fossil fuel combustions in winter-spring, while there could be an additional contribution from increased biogenic sources during summer-fall. Because a surface station in MNM rarely observed the summer-fall high CH4 concentration values in the mid-troposphere, the aircraft measurements could provide a powerful constraint on the CH4 emission estimates for Asia, in addition to that provided by the surface measurements. This aircraft measurement program is regularly conducted for the long-term monitoring of the greenhouse gases in the mid-troposphere, and it has a significant role for filling the data gap of the existing measurement network.

방화셔터와 피난계단이 존재하는 실내 환경의 화재 컴퓨터 시뮬레이션

논문에서는 방화셔터와 피난계단이 존재하는 실내 환경의 화재 시뮬레이션을 실시하여 방화셔터와 화재 확산 사이의 관계를 분석하였다. 화재 시뮬레이션용 상용 소프트웨어인 FDS(Fire Dynamics Simulator)를 사용하여 가상으로 설정한 실내 로비에서 화재 규모와 방화셔터의 개폐 여부를 변화시켜 가면서 모의실험을 실시하였다. 실험을 통해 화재실 벽면과 계단 입구의 온도 변화, 이산화탄소 농도 변화, 연기의 확산 등의 변수들을 구하고 결과를 검토하였다. 피난계단에서 온도와 이산화탄소의 분포는 화재규모와 개구부의 개폐 여부와 별 상관이 없으나, 방화셔터의 부분 하강이 연기의 확산을 막고 있음을 알 수 있었다. This paper analyzes the relation between fire shutters and fire spread by conducting fire simulation on inner space with fire shutters. Using Fire Dynamics Simulator (FDS), a commercial fire simulation software, the simulation is done on an ideal inner robby, where fire size and the open/close of fire shutters are varied. Our simulation environment can derive significant fire parameters such as temperature variation of fire room walls and entrances of refuge stairs, variation of carbon dioxide, and soot spread. According to the simulation results, temperature and carbon dioxide distribution in refuge stairs have little dependence on vent open or close, but the part close of fire shutters blocks soot inflow to refuge stairs.

Satellite‐derived estimations of spatial and seasonal variation in tropospheric carbon dioxide mass over China

China has frequently been questioned about the data transparency and accuracy of its energy and emission statistics. Satellite-derived remote sensing data potentially provide a useful tool to study the variation in carbon dioxide (CO2) mass over areas of the earth's surface. In this study, Greenhouse gases Observing SATellite (GOSAT) tropospheric CO2 concentration data and NCEP/NCAR reanalysis tropopause data were integrated to obtain estimates of tropospheric CO2 mass variations over the surface of China. These variations were mapped to show seasonal and spatial patterns with reference to China's provincial areas. The estimates of provincial tropospheric CO2 were related to statistical estimates of CO2 emissions for the provinces and considered with reference to provincial populations and gross regional products (GRP). Tropospheric CO2 masses for the Chinese provinces ranged from 53 ± 1 to 14,470 ± 63 million tonnes were greater for western than for eastern provinces and were primarily a function of provincial land area. Adjusted for land area troposphere CO2 mass was higher for eastern and southern provinces than for western and northern provinces. Tropospheric CO2 mass over China varied with season being highest in July and August and lowest in January and February. The average annual emission from provincial energy statistics of CO2 by China was estimated as 10.3% of the average mass of CO2 in the troposphere over China. The relationship between statistical emissions relative to tropospheric CO2 mass was higher than 20% for developed coastal provinces of China, with Shanghai, Tianjin, and Beijing having exceptionally high percentages. The percentages were generally lower than 10% for western inland provinces. Provincial estimates of emissions of CO2 were significantly positively related to provincial populations and gross regional products (GRP) when the values for the provincial municipalities Shanghai, Tianjin, and Beijing were excluded from the linear regressions. An increase in provincial GRP per person was related to a curvilinear increase in CO2 emissions, this being particularly marked for Beijing, Tianjin, and especially Shanghai. The absence of detection of specific elevation of CO2 mass in the troposphere above these municipalities may relate to the rapid mixing and dispersal of CO2 emissions or the proportion of the depth of the troposphere sensed by GOSAT.

The effects of increased temperature and CO2 on the Amazon fish, tambaqui (Collosoma macropomum, Cuvier, 1818)

The effect of Changed temperature and carbon dioxide (CO 2 ) variations on LDH (Lactate de Hydrogenase), MDH (Malate de Hydrogenase) & GST (Glutathione-S-Transferase) enzymes of muscles and MDH & GST Enzymes of liver of Tambaqui fish ( Collosoma macropomum, Cuvier, 1818) were studied in the Laboratory of Ecophysiology and Molecular Evolution (LEEM) of the National Institute for Amazonian Research (INPA). The initiative involves exposing fish to a temperature rise from 28C to 32C and a CO 2 concentration up to 10 times higher than today for 24, 48, 72 and 96 hours. The level of LDH, GST and MDH in both the tissues of Tambaqui (Muscles & Liver) showed a significant decreased at different exposure period. The level of Glucose in blood showed decreased and the values of Hb, Ht, RBC, VCM, HCM & CHCM showed increased at that exposure.

Diurnal Variations of Carbon Dioxide, Methane, and Nitrous Oxide Vertical Fluxes in a Subtropical Estuarine Marsh on Neap and Spring Tide Days

Measuring fluxes of greenhouse gases (GHGs) is fundamental to estimating their impact on global warming. We examined diurnal variations of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) vertical fluxes in a tidal marsh ecosystem. Measurements were recorded on neap and spring tide days in April and September 2010 in the Shanyutan wetland of the Min River estuary, southeast China. Here, we define a positive flux as directing into the atmosphere. CH4 fluxes on the diurnal scale were positive throughout, and CH4 emissions into the atmosphere on neap tide days were higher than on spring tide days. CH4 releases from the marsh ecosystem on neap tide days were higher in the daytime; however, on spring tide days, daily variations of CH4 emissions were more complex. The marsh ecosystem plays a twofold role in both releasing and assimilating CO2 and N2O gases on the diurnal scale. Average CO2 fluxes were positive on the daily scale both on neap and spring days and were greater on the neap tide days than on spring tide days. Diurnal variations of N2O fluxes fluctuated more. Over the diurnal period, soil temperature markedly controlled variations of CH4 emissions compared to other soil factors, such as salinity and redox potential. Tidal water height was a key factor influencing GHGs fluxes at the water–air interface. Compared with N2O, the diurnal course of CO2 and CH4 fluxes in the marsh ecosystem appeared to be directly controlled by marsh plants. These results have implications for sampling and scaling strategies for estimating GHGs fluxes in tidal marsh ecosystems.

Variations in atmospheric Carbon Dioxide and its association with rainfall and vegetation over India

In this paper we have studied variability and growth rate of surface observed atmospheric Carbon Dioxide (CO2) concentrations over Cape Rama, west coast of India and its association with rainfall and vegetation over this region. Cape Rama is a maritime site which experiences a seasonal reversal wind pattern receiving air masses having marine (continental) signatures during summer (winter) monsoon season. This study reveals that summer monsoon (JJAS) precipitation and monthly values of atmospheric CO2 concentration during the season are well correlated. Negative correlations are seen with CO2 concentrations of concurrent months of the season as well as subsequent months. However the magnitudes of correlation coefficients are decreased till hot pre-monsoon season (MAM). Annual cycle and interannual variability show negative relationship between CO2 concentration and vegetation over the region. CO2 concentration shows increasing trend and NDVI shows decreasing trend. However, the magnitude of increasing trend of CO2 concentration is higher. Amplitude of decreasing phase of vegetation is higher than the amplitude of increasing phase. Though the results show certain link between CO2 and climate variability, further examination with dense and longer data may be needed to confirm the result.

Seasonal variation in abiotic factors and ferulic acid toxicity in snail‐attractant pellets against the intermediate host snail Lymnaea acuminata

Laboratory evaluation was made to access the seasonal variations in abiotic environmental factors temperature, pH, dissolved oxygen, carbon dioxide, electrical conductivity and ferulic acid toxicity in snail-attractant pellets (SAP) against the intermediate host snail Lymnaea acuminata in each month of the years 2010 and 2011. On the basis of a 24-h toxicity assay, it was noted that lethal concentration values of 4.03, 3.73% and 4.45% in SAP containing starch and 4.16, 4.23% and 4.29% in SAP containing proline during the months of May, June and September, respectively, were most effective in killing the snails, while SAP containing starch/proline + ferulic acid was least effective in the month of January/February (24-h lethal concentration value was 7.67%/7.63% in SAP). There was a significant positive correlation between lethal concentration value of ferulic acid containing SAP and levels of dissolved O2 /pH of water in corresponding months. On the contrary, a negative correlation was observed between lethal concentration value and dissolved CO2 /temperature of test water in the same months. To ascertain that such a relationship between toxicity and abiotic factors is not co-incidental, the nervous tissue of treated (40% and 80% of 24-h lethal concentration value) and control group of snails was assayed for the activity of acetylcholinesterase (AChE) in each of the 12 months of the same year. There was a maximum inhibition of 58.43% of AChE, in snails exposed to 80% of the 24-h lethal concentration value of ferulic acid + starch in the month of May. This work shows conclusively that the best time to control snail population with SAP containing ferulic acid is during the months of May, June and September.

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.

DIURNAL AND SEASONAL VARIATION OF MEASURED ATMOSPHERIC CO2 AT DEHRADUN DURING 2009

Abstract. Atmospheric carbon dioxide (CO2) is the major greenhouse gas. We analysed the diurnal trend and seasonal variations of atmospheric Carbon Dioxide (CO2) measured at Dehradun during 2009. The measurements are taken from the Vaisala CO2 probe installed at the top of the IIRS building. A distinct diurnal cycle with seasonal variations is present in these measurements. Diurnal cycle exhibits a half sinusoidal variation with decreasing phase during sunrise to afternoon and increasing phase during afternoon to sunset. CO2 mostly remains constant with higher values during the night. The largest negative anomaly with respect to the annual mean varies between +/-20 ppmv with positive anomaly during the night time and negative anomaly during the day time. The cause of such variation could be attributed to the local ecosystem activity. During the day time the sinking of CO2 through the photosynthesis dominates its release through autotrophic and heterotrophic respiration. On the other hand, photosynthesis has been ceased during the night time and respiration only controls the night variation of CO2.There exists significant change on the diurnal cycle of CO2 in different seasons during the year. The maximum rapid decrease in CO2 concentration in early morning hours is due to photosynthetic activity during the monsoon periods (maximum in August -8ppm). During monsoon period rapid night time increase of CO2 is observed due to the enhancement of respiration. An inverse relationship exist between model simulated net ecosystem productivity and CO2 deviations on monthly basis. This diurnal and seasonal variations in situ CO2 are in confirmation with model simulated results.

Steady-State Behavior of Natural Circulation Loops Operating With Supercritical Fluids for Open and Closed Loop Boundary Conditions

Supercritical water (SCW) exhibits excellent heat transfer characteristics and a high volumetric expansion coefficient (hence high mass flow rates in natural circulation systems) near the critical temperature. SCW is being considered as a coolant in some advanced nuclear reactor designs on account of its potential to offer high thermal efficiency, compact size, and elimination of steam generator, separator, and dryer, making it economically competitive. The elimination of phase change results in elimination of the critical heat flux phenomenon. Cooling a reactor at full power with natural instead of forced circulation is generally considered an enhancement of passive safety. In view of this, it is essential to study natural circulation behavior at supercritical conditions. Carbon dioxide can be considered to be a good simulant of water for natural circulation at supercritical conditions, since the density and viscosity variation of carbon dioxide follows a curve parallel to that of water at supercritical conditions. Hence, experiments were conducted in a closed supercritical pressure natural circulation loop (SPNCL) with supercritical carbon dioxide as working fluid. A nonlinear stability analysis code (NOLSTA) has been developed to carry out steady-state and stability analysis of open and closed loop natural circulation at supercritical conditions. The code has been validated for steady-state predictions with experimental data available in open literature and experiments conducted in SPNCL.

The imprint of surface fluxes and transport on variations in total column carbon dioxide

Abstract. New observations of the vertically integrated CO2 mixing ratio, ⟨CO2⟩, from ground-based remote sensing show that variations in CO2⟩ are primarily determined by large-scale flux patterns. They therefore provide fundamentally different information than observations made within the boundary layer, which reflect the combined influence of large-scale and local fluxes. Observations of both ⟨CO2⟩ and CO2 concentrations in the free troposphere show that large-scale spatial gradients induce synoptic-scale temporal variations in ⟨CO2⟩ in the Northern Hemisphere midlatitudes through horizontal advection. Rather than obscure the signature of surface fluxes on atmospheric CO2, these synoptic-scale variations provide useful information that can be used to reveal the meridional flux distribution. We estimate the meridional gradient in ⟨CO2⟩ from covariations in ⟨CO2⟩ and potential temperature, θ, a dynamical tracer, on synoptic timescales to evaluate surface flux estimates commonly used in carbon cycle models. We find that simulations using Carnegie Ames Stanford Approach (CASA) biospheric fluxes underestimate both the ⟨CO2⟩ seasonal cycle amplitude throughout the Northern Hemisphere midlatitudes and the meridional gradient during the growing season. Simulations using CASA net ecosystem exchange (NEE) with increased and phase-shifted boreal fluxes better fit the observations. Our simulations suggest that climatological mean CASA fluxes underestimate boreal growing season NEE (between 45–65° N) by ~40%. We describe the implications for this large seasonal exchange on inference of the net Northern Hemisphere terrestrial carbon sink.

Spatial variation of carbon dioxide fluxes in corn and soybean fields

Spatial variation of soil carbon dioxide (CO2) flux during a growing season within corn and soybean canopies has not been quantified. These cropping systems are the most intense in the United States and the potential for carbon (C) sequestration in these systems through changes in soil management practices create an opportunity for reduction in greenhouse gas emissions; however, the need to understand the variation in fields is critical to evaluating changes in management systems. A study was designed to evaluate the spatial variation in soil CO2 fluxes along two transects in corn and soybean fields. Samples were collected every 5 m along a 100 m transect between the rows of the crop and also along a transect in which the plants had been removed to reduce the potential of root respiration. Soil CO2 fluxes were collected at each position with air temperature, soil temperature at 0.05 m, and soil water content (0 - 0.06 m). At the end of the season, soil samples for the upper 0.1 m were collected for soil organic C content, pH, sand, silt, and clay contents. On each day measurements were made, the observed CO2 emissions were scaled by dividing the CO2 flux at each position by the mean CO2 flux of the entire transect. Observed CO2 fluxes were signifycantly larger in the row than in the fallow position for both crops. There were no differences between the corn and soybean fallow transects; however, the corn row samples were larger than the soybean row samples. No consistent spatial patterns were observed in the CO2 fluxes or any of the soil properties over the course of the study. When the CO2 flux data were combined over the season, there was a significant spatial pattern in the fallow transects for both crops but not for the row transects. Sampling for CO2 flux values in cropping systems has to consider the presence of a crop canopy and the amount of root respiration.

Five-year analysis of background carbon dioxide and ozone variations during summer seasons at the Mario Zucchelli station (Antarctica)

Five-year analysis of background carbon dioxide and ozone variations during summer seasons at the Mario Zucchelli station (Antarctica)

Seasonal variation of carbon dioxide fluxes over irrigated soybean (Glycine max L.)

In this study, variations in carbon dioxide (CO2) fluxes resulting from gross primary production (GPP), net ecosystem exchange (NEE), and respiration (R e) of soybean (Glycine max L.) were investigated by the Eddy Covariance method during the growing period from June to November 2005 on an irrigated sand field at the Arid Land Research Center, Tottori University in Tottori, Japan. Although climatic conditions were humid and temperate, the soybeans required frequent irrigation because of the low water holding capacity of the sandy soil at the field site. Finally, it has been found that the accumulated NEE, GPP, and R e fluxes of soybean over 126 days amount to −93, 319, and 226 gC m−2, respectively. Furthermore, the average ratio of GPP to R e was 1.4 and the average ratio of NEE to GPP was about −0.29 for the growth period of soybean. Daily maximum NEE of −3.8 gC m−2 occurred when LAI was 1.1.