scholarly journals Soil–atmosphere exchange of carbonyl sulfide in a Mediterranean citrus orchard

2019 ◽  
Vol 19 (6) ◽  
pp. 3873-3883
Author(s):  
Fulin Yang ◽  
Rafat Qubaja ◽  
Fyodor Tatarinov ◽  
Rafael Stern ◽  
Dan Yakir
Keyword(s):  
Soil Depth ◽  
Carbonyl Sulfide ◽  
Surface Flux ◽  
Temporal Variations ◽  
Co2 Exchange ◽  
Co2 Fluxes ◽  
Concentration Gradients ◽  
Citrus Orchard ◽  
Soil Concentration ◽  
Net Uptake

Abstract. Carbonyl sulfide (COS) is used as a tracer of CO2 exchange at the ecosystem and larger scales. The robustness of this approach depends on knowledge of the soil contribution to the ecosystem fluxes, which is uncertain at present. We assessed the spatial and temporal variations in soil COS and CO2 fluxes in a Mediterranean citrus orchard combining surface flux chambers and soil concentration gradients. The spatial heterogeneity in soil COS exchange indicated net uptake below and between trees of up to 4.6 pmol m−2 s−1 and net emission in sun-exposed soil between rows of up to 2.6 pmol m−2 s−1, with an overall mean uptake value of 1.1±0.1 pmol m−2 s−1. Soil COS concentrations decreased with soil depth from atmospheric levels of ∼450 to ∼100 ppt at 20 cm depth, while CO2 concentrations increased from ∼400 to ∼5000 ppm. COS flux estimates from the soil concentration gradients were, on average, -1.0±0.3 pmol m−2 s−1, consistent with the chamber measurements. A soil COS flux algorithm driven by soil moisture and temperature (5 cm depth) and distance from the nearest tree, could explain 75 % of variance in soil COS flux. Soil relative uptake, the normalized ratio of COS to CO2 fluxes was, on average, -0.4±0.3 and showed a general exponential response to soil temperature. The results indicated that soil COS fluxes at our study site were dominated by uptake, with relatively small net fluxes compared to both soil respiration and reported canopy COS fluxes. Such a result should facilitate the application of COS as a powerful tracer of ecosystem CO2 exchange.

scholarly journals Soil-atmosphere exchange of carbonyl sulfide in Mediterranean citrus orchard

2018 ◽  
Author(s):  
Fulin Yang ◽  
Rafat Qubaja ◽  
Fyodor Tatarinov ◽  
Rafael Stern ◽  
Dan Yakir
Keyword(s):  
Soil Depth ◽  
Carbonyl Sulfide ◽  
Surface Flux ◽  
Temporal Variations ◽  
Co2 Exchange ◽  
Co2 Fluxes ◽  
Concentration Gradients ◽  
Citrus Orchard ◽  
Soil Concentration ◽  
Net Uptake

Abstract. Carbonyl sulfide (COS) is used as a as a tracer of CO2 exchange at the ecosystem and larger scales. The robustness of this approach depends on knowledge of the soil contribution to the ecosystem fluxes, which is uncertain at present. We assessed the spatial and temporal variations of soil COS and CO2 fluxes in the Mediterranean citrus orchard combining surface flux chambers and soil concentration gradients. The spatial heterogeneity in soil COS exchange indicated net uptake below and between trees of up to −4.6 pmol m−2 s−1, and net emission in exposed soil between rows, of up to +2.6 pmol m−2 s−1, with weighted mean uptake values of −1.10 ± 0.10 pmol m−2 s−1. Soil COS concentrations decreased with soil depth from atmospheric levels of ~ 450 to ~ 100 ppt at 20 cm depth, while CO2 concentrations increased from ~ 400 to ~ 5000 ppm. COS flux estimates from the soil concentration gradients were, on average, −1.02 ± 0.26 pmol m−2 s−1, consistent with the chamber measurements. A soil COS flux algorithm driven by soil moisture and temperature (5 cm depth) and distance from the nearest tree, could explain 75 % of variance in soil COS flux. Soil relative uptake, the normalized ratio of COS to CO2 fluxes was, on average −0.37 and showed a general exponential response to soil temperature. The results indicated that soil COS fluxes at our study site were dominated by uptake, with relatively small net fluxes compared to both soil respiration and reported canopy COS fluxes. Such result should facilitate the application of COS as a powerful tracer of ecosystem CO2 exchange.

Chloride Regulation at Low Salinities by Nereis Diversicolor (Annelida, Polychaeta)

1970 ◽  
Vol 53 (1) ◽  
pp. 75-92
Author(s):  
RALPH I. SMITH
Keyword(s):  
Electrical Potential ◽  
Urine Volume ◽  
Chloride Concentration ◽  
Pond Water ◽  
The Body ◽  
Salinity Range ◽  
Concentration Gradients ◽  
North Eastern ◽  
Net Uptake ◽  
Chloride Regulation

1. N. diversicolor from estuarine conditions in north-eastern England can be adapted to a chloride concentration in a pond water (PW) medium at least as low as 0.9 mM/l, and shows a net uptake of chloride when returned to a medium 3-10 mM/l more concentrated. But in comparable transfers after adaptation at a chloride concentration of 10 mM/l, net uptake is not measurable. 2. Net uptake of chloride is demonstrable in the lowest salinities, where coelomic chloride concentration drops below the regulatory plateau. Net uptake reaches 3.5 µM/g wet weight/h. 3. Chloride loss is well correlated with weight loss after adaptation in 10 mM/l, but poorly so after adaptation in PW, suggesting that the urine is very hypotonic to body fluid in PW, and isotonic (or less hypotonic) at environmental chloride concentrations of 10 mM/l or higher. 4. Uptake of chloride occurs against both electrical and chemical-concentration gradients over the lower third of the environmental salinity range, which is the range in which hyperosmotic and hyperionic regulation are most pronounced. 5. The electrical potential across the body wall is maximal in PW (17 mV, inside-negative), and decreases to zero in 50 % SW. 6. Chloride influx (as measured with 36Cl) is highest in SW, and decreases in proportion to chloride concentration down to 50-25% SW, rises to a secondary maximum in 10% SW or less, and decreases as fresh water is approached. 7. Urinary chloride loss is low, and proportional to external chloride concentration in higher salinities, maximal in the c. 10% SW range of salinities, and apparently decreases to a minimum in FW. This may be in part the consequence of recovery of chloride from an hypotonic urine, in part the consequence of a reduction in urine volume. Evidence for these last two possibilities will be given in the papers which follow.

scholarly journals Estimating surface CO<sub>2</sub> fluxes from space-borne CO<sub>2</sub> dry air mole fraction observations using an ensemble Kalman Filter

2009 ◽  
Vol 9 (8) ◽  
pp. 2619-2633 ◽  
Author(s):  
L. Feng ◽  
P. I. Palmer ◽  
H. Bösch ◽  
S. Dance
Keyword(s):  
Kalman Filter ◽  
Mole Fraction ◽  
Ensemble Kalman Filter ◽  
Transport Model ◽  
Co2 Flux ◽  
Surface Flux ◽  
Surface Fluxes ◽  
Co2 Fluxes ◽  
Dry Air ◽  
Geographical Regions

Abstract. We have developed an ensemble Kalman Filter (EnKF) to estimate 8-day regional surface fluxes of CO2 from space-borne CO2 dry-air mole fraction observations (XCO2) and evaluate the approach using a series of synthetic experiments, in preparation for data from the NASA Orbiting Carbon Observatory (OCO). The 32-day duty cycle of OCO alternates every 16 days between nadir and glint measurements of backscattered solar radiation at short-wave infrared wavelengths. The EnKF uses an ensemble of states to represent the error covariances to estimate 8-day CO2 surface fluxes over 144 geographical regions. We use a 12×8-day lag window, recognising that XCO2 measurements include surface flux information from prior time windows. The observation operator that relates surface CO2 fluxes to atmospheric distributions of XCO2 includes: a) the GEOS-Chem transport model that relates surface fluxes to global 3-D distributions of CO2 concentrations, which are sampled at the time and location of OCO measurements that are cloud-free and have aerosol optical depths <0.3; and b) scene-dependent averaging kernels that relate the CO2 profiles to XCO2, accounting for differences between nadir and glint measurements, and the associated scene-dependent observation errors. We show that OCO XCO2 measurements significantly reduce the uncertainties of surface CO2 flux estimates. Glint measurements are generally better at constraining ocean CO2 flux estimates. Nadir XCO2 measurements over the terrestrial tropics are sparse throughout the year because of either clouds or smoke. Glint measurements provide the most effective constraint for estimating tropical terrestrial CO2 fluxes by accurately sampling fresh continental outflow over neighbouring oceans. We also present results from sensitivity experiments that investigate how flux estimates change with 1) bias and unbiased errors, 2) alternative duty cycles, 3) measurement density and correlations, 4) the spatial resolution of estimated flux estimates, and 5) reducing the length of the lag window and the size of the ensemble. At the revision stage of this manuscript, the OCO instrument failed to reach its orbit after it was launched on 24 February 2009. The EnKF formulation presented here is also applicable to GOSAT measurements of CO2 and CH4.

scholarly journals O<sub>2</sub> : CO<sub>2</sub> exchange ratio for net turbulent flux observed in an urban area of Tokyo, Japan, and its application to an evaluation of anthropogenic CO<sub>2</sub> emissions

2020 ◽  
Vol 20 (9) ◽  
pp. 5293-5308
Author(s):  
Shigeyuki Ishidoya ◽  
Hirofumi Sugawara ◽  
Yukio Terao ◽  
Naoki Kaneyasu ◽  
Nobuyuki Aoki ◽  
...  
Keyword(s):  
Fuel Consumption ◽  
Urban Area ◽  
Co2 Emission ◽  
Co2 Flux ◽  
Co2 Exchange ◽  
Co2 Fluxes ◽  
Diurnal Cycles ◽  
Co2 Concentrations ◽  
Human Respiration ◽  
Two Peaks

Abstract. In order to examine O2 consumption and CO2 emission in a megacity, continuous observations of atmospheric O2 and CO2 concentrations, along with CO2 flux, have been carried out simultaneously since March 2016 at the Yoyogi (YYG) site located in the middle of Tokyo, Japan. An average O2 : CO2 exchange ratio for net turbulent O2 and CO2 fluxes (ORF) between the urban area and the overlaying atmosphere was obtained based on an aerodynamic method using the observed O2 and CO2 concentrations. The yearly mean ORF was found to be 1.62, falling within the range of the average OR values of liquid and gas fuels, and the annual average daily mean O2 flux at YYG was estimated to be −16.3 µmol m−2 s−1 based on the ORF and CO2 flux. By using the observed ORF and CO2 flux, along with the inventory-based CO2 emission from human respiration, we estimated the average diurnal cycles of CO2 fluxes from gas and liquid fuel consumption separately for each season. Both the estimated and inventory-based CO2 fluxes from gas fuel consumption showed average diurnal cycles with two peaks, one in the morning and another one in the evening; however, the evening peak of the inventory-based gas consumption was much larger than that estimated from the CO2 flux. This can explain the discrepancy between the observed and inventory-based total CO2 fluxes at YYG. Therefore, simultaneous observations of ORF and CO2 flux are useful in validating CO2 emission inventories from statistical data.

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

2011 ◽  
Vol 8 (4) ◽  
pp. 7475-7524 ◽  
Author(s):  
G. Keppel-Aleks ◽  
P. O. Wennberg ◽  
R. A. Washenfelder ◽  
D. Wunch ◽  
T. Schneider ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Large Scale ◽  
Carbon Sink ◽  
Potential Temperature ◽  
Surface Flux ◽  
Growing Season ◽  
Temporal Variations ◽  
Surface Fluxes ◽  
Synoptic Scale ◽  
Meridional Gradient

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 Carnegie Ames Stanford Approach (CASA) biospheric fluxes underestimate both the ⟨CO2⟩ seasonal cycle amplitude throughout the Northern Hemisphere midlatitudes as well as the meridional gradient during the growing season. Simulations using CASA net ecosystem exchange (NEE) with increased and phase-shifted boreal fluxes better reflect the observations. Our simulations suggest that boreal growing season NEE (between 45–65° N) is underestimated by ~40 % in CASA. We describe the implications for this large seasonal exchange on inference of the net Northern Hemisphere terrestrial carbon sink.

scholarly journals Cereal-legume mixtures increase net CO<sub>2</sub> uptake in a forage system of the Eastern Pyrenees

2020 ◽  
Author(s):  
Mercedes Ibañez ◽  
Núria Altimir ◽  
Àngela Ribas ◽  
Werner Eugster ◽  
Maria-Teresa Sebastià
Keyword(s):  
Management Strategies ◽  
Growth Period ◽  
Co2 Exchange ◽  
Co2 Uptake ◽  
Co2 Fluxes ◽  
Crop Season ◽  
Forage Species ◽  
Net Co2 Uptake ◽  
Forage System ◽  
Intensively Managed

Abstract. Forage systems are the major land use, and provide essential resources for animal feeding. Assessing the influence of forage species on net ecosystem CO2 exchange (NEE) is key to develop management strategies that can help to mitigate climate change, while optimizing productivity of these systems. However, little is known about the effect of forage species on CO2 exchange fluxes and net biome production (NBP), considering: species ecophysiological responses; growth and fallow periods separately; and the management associated with the particular sown species. Our study assesses the influence of cereal monocultures vs. cereal legume mixtures on (1) ecosystem scale CO2 fluxes, for the whole crop season and separately for the two periods of growth and fallow; (2) potential sensitivities of CO2 exchange related to short-term variations in light, temperature and soil water content; and (3) NBP during the growth period; this being the first long term (seven years) ecosystem scale CO2 fluxes dataset of an intensively managed forage system in the Pyrenees region. Our results provide strong evidence that cereal-legume mixtures lead to higher net CO2 uptake than cereal monocultures, as a result of higher gross CO2 uptake, while respiratory fluxes did not significantly increase. Also, management associated with cereal legume mixtures favoured vegetation voluntary regrowth during the fallow period, which was decisive for the cumulative net CO2 uptake of the entire crop season. All cereal legume mixtures and some cereal monocultures had a negative NBP (net gain of C) during the growth period, indicating C input to the system, besides the yield. Overall, cereal legume mixtures enhanced net CO2 sink capacity of the forage system, while ensuring productivity and forage quality.

scholarly journals Evidence for surface organic matter modulation of air-sea CO<sub>2</sub> gas exchange

2009 ◽  
Vol 6 (6) ◽  
pp. 1105-1114 ◽  
Author(s):  
M. Ll. Calleja ◽  
C. M. Duarte ◽  
Y. T. Prairie ◽  
S. Agustí ◽  
G. J. Herndl
Keyword(s):  
Organic Matter ◽  
Wind Speed ◽  
Gas Exchange ◽  
Co2 Exchange ◽  
Open Ocean ◽  
Gas Transfer ◽  
Co2 Fluxes ◽  
Transfer Velocity ◽  
Gas Transfer Velocity

Abstract. Air-sea CO2 exchange depends on the air-sea CO2 gradient and the gas transfer velocity (k), computed as a function of wind speed. Large discrepancies among relationships predicting k from wind suggest that other processes also contribute significantly to modulate CO2 exchange. Here we report, on the basis of the relationship between the measured gas transfer velocity and the organic carbon concentration at the ocean surface, a significant role of surface organic matter in suppressing air-sea gas exchange, at low and intermediate winds, in the open ocean, confirming previous observations. The potential role of total surface organic matter concentration (TOC) on gas transfer velocity (k) was evaluated by direct measurements of air-sea CO2 fluxes at different wind speeds and locations in the open ocean. According to the results obtained, high surface organic matter contents may lead to lower air-sea CO2 fluxes, for a given air-sea CO2 partial pressure gradient and wind speed below 5 m s−1, compared to that observed at low organic matter contents. We found the bias in calculated gas fluxes resulting from neglecting TOC to co-vary geographically and seasonally with marine productivity. These results support previous evidences that consideration of the role of organic matter in modulating air-sea CO2 exchange may improve flux estimates and help avoid possible bias associated to variability in surface organic concentration across the ocean.

Damping of Sinusoidal Surface Flux Fluctuations with Soil Depth

2009 ◽  
Vol 8 (1) ◽  
pp. 119-126 ◽  
Author(s):  
Mark Bakker ◽  
John L. Nieber
Keyword(s):  
Soil Depth ◽  
Surface Flux ◽  
Sinusoidal Surface

Carbon Dioxide and Water Vapour Exchange Parameters of Photosynthesis in a Crassulacean Plant, Kalanchoe daigremontiana

1974 ◽  
Vol 1 (3) ◽  
pp. 397 ◽  
Author(s):  
WG Allaway ◽  
B Austin ◽  
RO Slatyer
Keyword(s):  
Water Vapour ◽  
Internal Resistance ◽  
Co2 Exchange ◽  
C3 Plants ◽  
Co2 Uptake ◽  
Co2 Compensation Point ◽  
Steady Rate ◽  
Water Vapour Diffusion ◽  
Net Uptake ◽  
Second Period

In 16-h days and under a 26/19°C day/night temperature regime, leaves of K. daigvemontiana took up CO2 in the daytime as well as at night. Daytime net CO2 uptake was in two periods: an initial one about 5 h long, in which net uptake rose to a maximum and then fell to near zero; and, after a period in which stomata were closed and CO2 exchange did not take place, a second period of net uptake. In this second period net uptake rose rapidly to a steady rate which was maintained for about 8 h until the end of the day. In this period, mean rate of light-saturated photosynthesis in normal air was 25 ng cm-2 s-1; maximum obtainable photosynthesis rate averaged 87 ng cm-2 s-1 at this time. These values are considerably lower than those to be expected for C3 plants. The internal resistance to CO2 uptake averaged about 8 s cm-l. In normal air, leaf resistance to water vapour diffusion averaged about 8.5 s cm-1 in the steady period of photosynthesis. Both these resistances are higher than those often reported for C3 plants, and may explain the low photosynthetic rates. The CO2 compensation point during the period of steady photosynthesis was about 51 μ 1/1 (92 ng cm-3). This value, together with some biochemical evidence from pulse-chase experiments, suggests that photosynthesis in the last 8 h of the light period follows a C3-type pathway.

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