scholarly journals Regulation of CO<sub>2</sub> emissions from temperate streams and reservoirs

2013 ◽  
Vol 10 (11) ◽  
pp. 7539-7551 ◽  
Author(s):  
S. Halbedel ◽  
M. Koschorreck
Keyword(s):  
Co2 Emission ◽  
Water Reservoir ◽  
Co2 Flux ◽  
Co2 Concentration ◽  
Small Degree ◽  
Dominant Factor ◽  
Physical Factors ◽  
Metabolic Processes ◽  
Piston Velocity ◽  
Co2 Concentrations

Abstract. It has become more and more evident that CO2 emission (FCO2) from freshwater systems is an important part of the global carbon cycle. To date, only a few studies have addressed the different mechanisms that regulate FCO2 in lotic and lentic systems. In a comparative study we investigated how different biogeochemical and physical factors can affect FCO2 values in streams and reservoirs. We examined the seasonal variability in CO2 concentrations and emissions from four streams and two pre-dams of a large drinking water reservoir located in the same catchment, and compared them with environmental factors that were measured concurrently. All the streams were generally supersaturated with CO2 throughout the year, while both reservoirs functioned to a small degree as CO2 sinks during summer stratification and CO2 sources after circulation had set in. FCO2 from streams ranged from 23 to 355 mmol m−2 d−1 and exceeded the fluxes recorded for the reservoirs (−8.9 to 161.1 mmol m−2 d−1). Both the generally high piston velocity (k) and the CO2 oversaturation contributed to the higher FCO2 from streams in comparison to lakes. In both streams and reservoirs FCO2 was mainly governed by the CO2 concentration (r = 0.92, p < 0.001 for dams; r = 0.90, p < 0.001 for streams), which was in turn affected by metabolic processes and nutrients in both systems and also by lateral inflow in the streams. Besides CO2 concentration, physical factors also influence FCO2 in lakes and streams. During stratification, FCO2 in both pre-dams was regulated by primary production in the epilimnion, which led to a decrease of FCO2. During circulation, when CO2 from the hypolimnion was mixed with the epilimnion, FCO2 increased on account of the CO2 input from the hypolimnion. The CO2 from the hypolimnion originates from the mineralisation of organic matter. FCO2 from streams was mainly influenced by geomorphological and hydrological factors affecting k, which is less relevant in low-wind lakes. Under high-wind conditions, however, k regulates FCO2 from lotic systems as well. We developed a theoretical framework describing the role of the different regulation mechanisms for FCO2 from streams and lakes. In summary, the dominant factor affecting FCO2 is the concentration of CO2 in the surface water. Lake stratification has a very important regulatory effect on FCO2 from lakes on account of its influence on CO2 concentrations and metabolic processes. Nevertheless, FCO2 values in heterotrophic streams are generally higher. The higher k values are responsible for the comparatively high degree of FCO2. On a Central European scale, CO2 emission from streams is probably of greater importance than the CO2 flux from standing waters.

scholarly journals Different regulation of CO<sub>2</sub> emission from streams and lakes

2013 ◽  
Vol 10 (6) ◽  
pp. 10021-10053
Author(s):  
S. Halbedel ◽  
M. Koschorreck
Keyword(s):  
Co2 Emission ◽  
Water Reservoir ◽  
Co2 Flux ◽  
Co2 Concentration ◽  
Physical Factors ◽  
Regulation Mechanism ◽  
Schematic Model ◽  
Piston Velocity ◽  
Drinking Water Reservoir ◽  
Standing Waters

Abstract. It has become more and more evident that CO2 emission (FCO2) from freshwater systems is an important part in the global carbon cycle. Only few studies addressed the different mechanisms regulating FCO2 from lotic and lentic systems. In a comparative study we investigated how different biogeochemical and physical factors can affect FCO2 from streams and reservoirs. We examined the seasonal variability in CO2 concentrations and emissions from four streams and two pre-dams of a large drinking water reservoir located in the same catchment, and compared them with parallel measured environmental factors. All streams generally were supersaturated with CO2 over the whole year, while both reservoirs where CO2 sinks during summer stratification and sources after circulation. FCO2 from streams ranged from 23 to 355 mmol m–2 d–1 and exceeded the fluxes from the reservoirs (–24 to 97 mmol m–2 d–1). Both the generally high piston velocity (k) and CO2 oversaturation were responsible for the higher FCO2 from streams in comparison to lakes. In both, streams and reservoirs FCO2 was mainly controlled by the CO2 concentration (r = 0.86 for dams, r = 0.90 for streams), which was clearly affected by metabolism and nutrients in both systems. Besides CO2 concentration, also physical factors control FCO2 in lakes and streams. During stratification FCO2 in both pre-dams was controlled by primary production in the epilimnion, which led to a decrease of FCO2. During circulation when CO2 from the hypolimnion was mixed with the epilimnion and the organic matter mineralisation was more relevant, FCO2 increased. FCO2 from streams was physically controlled especially by geomorphological and hydrological factors regulating k, which is less relevant in low wind lakes. We developed a schematic model describing the role of the different regulation mechanism on FCO2 from streams and lakes. Taken together, FCO2 is generally mostly controlled by CO2 concentration in the surface water. Lake stratification is a very important factor regulating FCO2 from lakes via controlling CO2 concentration and metabolism. But FCO2 in heterotrophic streams is generally higher. The higher k values are responsible for the comparable high FCO2. On a Central European landscape scale CO2 emission from streams was more relevant than the CO2 flux from standing waters.

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 Explaining CO<sub>2</sub> fluctuations observed in snowpacks

2018 ◽  
Vol 15 (3) ◽  
pp. 847-859
Author(s):  
Laura Graham ◽  
David Risk
Keyword(s):  
Diffusion Model ◽  
Meteorological Data ◽  
Negative Relationship ◽  
Flux Measurement ◽  
Co2 Flux ◽  
Co2 Concentration ◽  
Physical Factors ◽  
Advective Transport ◽  
Soil Co2 ◽  
C Cycle

Abstract. Winter soil carbon dioxide (CO2) respiration is a significant and understudied component of the global carbon (C) cycle. Winter soil CO2 fluxes can be surprisingly variable, owing to physical factors such as snowpack properties and wind. This study aimed to quantify the effects of advective transport of CO2 in soil–snow systems on the subdiurnal to diurnal (hours to days) timescale, use an enhanced diffusion model to replicate the effects of CO2 concentration depletions from persistent winds, and use a model–measure pairing to effectively explore what is happening in the field. We took continuous measurements of CO2 concentration gradients and meteorological data at a site in the Cape Breton Highlands of Nova Scotia, Canada, to determine the relationship between wind speeds and CO2 levels in snowpacks. We adapted a soil CO2 diffusion model for the soil–snow system and simulated stepwise changes in transport rate over a broad range of plausible synthetic cases. The goal was to mimic the changes we observed in CO2 snowpack concentration to help elucidate the mechanisms (diffusion, advection) responsible for observed variations. On subdiurnal to diurnal timescales with varying winds and constant snow levels, a strong negative relationship between wind speed and CO2 concentration within the snowpack was often identified. Modelling clearly demonstrated that diffusion alone was unable to replicate the high-frequency CO2 fluctuations, but simulations using above-atmospheric snowpack diffusivities (simulating advective transport within the snowpack) reproduced snow CO2 changes of the observed magnitude and speed. This confirmed that wind-induced ventilation contributed to episodic pulsed emissions from the snow surface and to suppressed snowpack concentrations. This study improves our understanding of winter CO2 dynamics to aid in continued quantification of the annual global C cycle and demonstrates a preference for continuous wintertime CO2 flux measurement systems.

scholarly journals A regional carbon data assimilation system and its preliminary evaluation in East Asia

2015 ◽  
Vol 15 (2) ◽  
pp. 1087-1104 ◽  
Author(s):  
Z. Peng ◽  
M. Zhang ◽  
X. Kou ◽  
X. Tian ◽  
X. Ma
Keyword(s):  
Transport Model ◽  
Atmospheric Transport ◽  
Co2 Flux ◽  
Co2 Concentration ◽  
Preliminary Evaluation ◽  
Co2 Fluxes ◽  
Scaling Factors ◽  
Multi Scale ◽  
Co2 Concentrations ◽  
Inflation Factor

Abstract. In order to optimize surface CO2 fluxes at grid scales, a regional surface CO2 flux inversion system (Carbon Flux Inversion system and Community Multi-scale Air Quality, CFI-CMAQ) has been developed by applying the ensemble Kalman filter (EnKF) to constrain the CO2 concentrations and applying the ensemble Kalman smoother (EnKS) to optimize the surface CO2 fluxes. The smoothing operator is associated with the atmospheric transport model to constitute a persistence dynamical model to forecast the surface CO2 flux scaling factors. In this implementation, the "signal-to-noise" problem can be avoided; plus, any useful observed information achieved by the current assimilation cycle can be transferred into the next assimilation cycle. Thus, the surface CO2 fluxes can be optimized as a whole at the grid scale in CFI-CMAQ. The performance of CFI-CMAQ was quantitatively evaluated through a set of Observing System Simulation Experiments (OSSEs) by assimilating CO2 retrievals from GOSAT (Greenhouse Gases Observing Satellite). The results showed that the CO2 concentration assimilation using EnKF could constrain the CO2 concentration effectively, illustrating that the simultaneous assimilation of CO2 concentrations can provide convincing CO2 initial analysis fields for CO2 flux inversion. In addition, the CO2 flux optimization using EnKS demonstrated that CFI-CMAQ could, in general, reproduce true fluxes at grid scales with acceptable bias. Two further sets of numerical experiments were conducted to investigate the sensitivities of the inflation factor of scaling factors and the smoother window. The results showed that the ability of CFI-CMAQ to optimize CO2 fluxes greatly relied on the choice of the inflation factor. However, the smoother window had a slight influence on the optimized results. CFI-CMAQ performed very well even with a short lag-window (e.g. 3 days).

scholarly journals 2-D tomography of volcanic CO<sub>2</sub> from scanning hard-target differential absorption lidar: the case of Solfatara, Campi Flegrei (Italy)

2016 ◽  
Vol 9 (12) ◽  
pp. 5721-5734 ◽  
Author(s):  
Manuel Queißer ◽  
Domenico Granieri ◽  
Mike Burton
Keyword(s):  
Co2 Emission ◽  
Co2 Flux ◽  
Co2 Concentration ◽  
Campi Flegrei ◽  
Emission Rates ◽  
Differential Absorption ◽  
Differential Absorption Lidar ◽  
Major Pathway ◽  
Soil Degassing ◽  
Solfatara Crater

Abstract. Solfatara is part of the active volcanic zone of Campi Flegrei (Italy), a densely populated urban area where ground uplift and increasing ground temperature are observed, connected with rising rates of CO2 emission. A major pathway of CO2 release at Campi Flegrei is diffuse soil degassing, and therefore quantifying diffuse CO2 emission rates is of vital interest. Conventional in situ probing of soil gas emissions with accumulation chambers is accurate over a small footprint but requires significant time and effort to cover large areas. An alternative approach is differential absorption lidar, which allows for a fast and spatially integrated measurement. Here, a portable hard-target differential absorption lidar has been used to acquire horizontal 1-D profiles of column-integrated CO2 concentration at the Solfatara crater. To capture heterogenic features in the CO2 distribution, a 2-D tomographic map of the CO2 distribution has been inverted from the 1-D profiles. The scan was performed one-sided, which is unfavorable for the inverse problem. Nonetheless, the result is in agreement with independent measurements and furthermore confirms an area of anomalous CO2 degassing along the eastern edge as well as the center of the Solfatara crater. The method may have important implications for measurements of degassing features that can only be accessed from limited angles, such as airborne sensing of volcanic plumes. CO2 fluxes retrieved from the 2-D map are comparable, but modestly higher than emission rates from previous studies, perhaps reflecting an increase in CO2 flux or a more integrated measurement or both.

scholarly journals A regional carbon flux data assimilation system and its preliminary evaluation in East Asia

2014 ◽  
Vol 14 (14) ◽  
pp. 20345-20381
Author(s):  
Z. Peng ◽  
M. Zhang ◽  
X. Kou ◽  
X. Tian ◽  
X. Ma
Keyword(s):  
Carbon Flux ◽  
Transport Model ◽  
Atmospheric Transport ◽  
Co2 Flux ◽  
Co2 Concentration ◽  
Preliminary Evaluation ◽  
Co2 Fluxes ◽  
Scaling Factors ◽  
Co2 Concentrations ◽  
Inflation Factor

Abstract. In order to optimize surface CO2 fluxes at finer scales, a regional surface CO2 flux inversion system (Carbon Flux Inversion system and Community Multi-scale Air Quality, CFI-CMAQ) has been developed by simultaneously assimilating CO2 concentrations and surface CO2 fluxes into the regional modeling system, CMAQ. The smoothing operator is associated with the atmospheric transport model to constitute a persistence dynamical model to forecast the surface CO2 flux scaling factors. In this implementation, the "signal-to-noise" problem can be avoided; plus, any useful observed information achieved by the current assimilation cycle can be transferred into the next assimilation cycle. Thus, the surface CO2 fluxes can be optimized as a whole at the grid scale in CFI-CMAQ. The performance of CFI-CMAQ was quantitatively evaluated through a set of Observing System Simulation Experiments (OSSEs) by assimilating CO2 retrievals from GOSAT (Greenhouse Gases Observing Satellite). The results showed that the CO2 concentration assimilation using the ensemble Kalman filter (EnKF) could constrain the CO2 concentrations effectively, illustrating that the simultaneous assimilation of CO2 concentrations can provide convincing CO2 initial analysis fields for CO2 flux inversion. In addition, the CO2 flux optimization using the ensemble Kalman smoother (EnKS) demonstrated that CFI-CMAQ could in general reproduce true fluxes at finer scales with acceptable bias. Two further sets of numerical experiments were conducted to investigate the sensitivities of the inflation factor of scaling factors and the smoother window. The results showed that the ability of CFI-CMAQ to optimize CO2 fluxes greatly relied on the choice of the inflation factor. However, the smoother window had a slight influence on the optimized results. CFI-CMAQ performed very well even with a short lag-window (e.g. 3 days).

scholarly journals Explaining CO<sub>2</sub> fluctuations observed in snowpacks

2017 ◽  
Author(s):  
Laura Graham ◽  
David Risk
Keyword(s):  
Diffusion Model ◽  
Meteorological Data ◽  
Negative Relationship ◽  
Flux Measurement ◽  
Co2 Flux ◽  
Co2 Concentration ◽  
Physical Factors ◽  
Advective Transport ◽  
Soil Co2 ◽  
C Cycle

Abstract. Winter soil carbon dioxide (CO2) respiration is a significant and understudied component of the global carbon (C) cycle. Datasets have shown that winter soil CO2 fluxes can be surprisingly variable, owing to physical factors such as snowpack properties and wind. This study aimed to: quantify the effects of advective transport of CO2 in soil-snow systems on the sub-diurnal to diurnal (hours to days) timescale, use an enhanced diffusion model to replicate the effects of CO2 concentration depletions from persistent winds, and use a model-measure pairing to effectively explore what is happening in the field. We took continuous measurements of CO2 concentration gradients and meteorological data at a site in the Cape Breton Highlands of Nova Scotia, Canada to determine the relationship between wind speeds and CO2 levels in snowpacks. We adapted a soil CO2 diffusion model for the soil-snow system, and simulated stepwise changes in transport rate over a broad range of plausible synthetic cases. The goal was to mimic the changes we observed in CO2 snowpack concentration to help elucidate the mechanisms (diffusion, advection) responsible for observed variations. On sub-diurnal to diurnal timescales with varying winds and constant snow levels, a strong negative relationship between wind speed and CO2 concentration within the snowpack was often identified. Modelling clearly demonstrated that diffusion alone was unable to replicate the high frequency CO2 fluctuations, but simulations using above-atmospheric snowpack diffusivities (simulating advective transport within the snowpack) reproduced snow CO2 changes of the observed magnitude and speed. This confirmed that wind-induced ventilation contributed to episodic pulsed emissions from the snow surface and to suppressed snowpack concentrations. This study improves our understanding of winter CO2 dynamics to aid in continued quantification of the annual global C cycle, and demonstrates a preference for continuous wintertime CO2 flux measurement systems.

scholarly journals Effects of Climatic Conditions, Season and Environmental Factors on CO2 Concentrations in Naturally Ventilated Primary Schools in Chile

2021 ◽  
Vol 13 (8) ◽  
pp. 4139
Author(s):  
Muriel Diaz ◽  
Mario Cools ◽  
Maureen Trebilcock ◽  
Beatriz Piderit-Moreno ◽  
Shady Attia
Keyword(s):  
Air Quality ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
Primary Schools ◽  
Co2 Concentration ◽  
Building Design ◽  
Climatic Conditions ◽  
Indoor Environmental Quality ◽  
Co2 Concentrations ◽  
The Impact

Between the ages of 6 and 18, children spend between 30 and 42 h a week at school, mostly indoors, where indoor environmental quality is usually deficient and does not favor learning. The difficulty of delivering indoor air quality (IAQ) in learning facilities is related to high occupancy rates and low interaction levels with windows. In non-industrialized countries, as in the cases presented, most classrooms have no mechanical ventilation, due to energy poverty and lack of normative requirements. This fact heavily impacts the indoor air quality and students’ learning outcomes. The aim of the paper is to identify the factors that determine acceptable CO2 concentrations. Therefore, it studies air quality in free-running and naturally ventilated primary schools in Chile, aiming to identify the impact of contextual, occupant, and building design factors, using CO2 concentration as a proxy for IAQ. The monitoring of CO2, temperature, and humidity revealed that indoor air CO2 concentration is above 1400 ppm most of the time, with peaks of 5000 ppm during the day, especially in winter. The statistical analysis indicates that CO2 is dependent on climate, seasonality, and indoor temperature, while it is independent of outside temperature in heated classrooms. The odds of having acceptable concentrations of CO2 are bigger when indoor temperatures are high, and there is a need to ventilate for cooling.

scholarly journals First experimental evidence for the CO<sub>2</sub>-driven origin of Stromboli's major explosions

2011 ◽  
Vol 3 (1) ◽  
pp. 411-430 ◽  
Author(s):  
A. Aiuppa ◽  
M. Burton ◽  
P. Allard ◽  
T. Caltabiano ◽  
G. Giudice ◽  
...  
Keyword(s):  
Experimental Evidence ◽  
Co2 Emission ◽  
Weight Ratio ◽  
Co2 Flux ◽  
Recent Model ◽  
Stromboli Volcano ◽  
Plumbing System ◽  
Gas Leakage ◽  
Basaltic Volcanoes ◽  
Monitoring Strategies

Abstract. We report on the first detection of CO2 flux precursors of the till now unforecastable larger than normal ("major") explosions that intermittently occur at Stromboli volcano (Italy). Automated survey of the crater plume emissions in the period 2006–2010, during which 12 such explosions happened, demonstrate that these events are systematically preceded by a brief phase of increasing CO2/SO2 weight ratio (up to >40) and CO2 flux (>1300 t/d) with respect to the time-averaged values of 3.7 and ~500 t/d typical for standard Stromboli's activity. These signals are best explained by the accumulation of CO2-rich gas at a discontinuity of the plumbing system (decreasing CO2 emission at the surface), followed by increasing gas leakage prior to the explosion. Our observations thus support the recent model of Allard (2010) for a CO2-rich gas trigger of recurrent major explosions at Stromboli, and demonstrate the possibility to forecast these events in advance from geochemical precursors. These observations and conclusions have clear implications for monitoring strategies at other open-vent basaltic volcanoes worldwide.

scholarly journals Elevated CO2 Concentrations and Water Stress Affect the Ability of Italian Ryegrass to Remediate Herbicides and Enhance its Allelopathic Effect

2019 ◽  
Vol 37 ◽  
Author(s):  
L.P. SILVEIRA ◽  
A.R. FEIJÓ ◽  
C. BENETTI ◽  
J.P. REFATTI ◽  
M.V. FIPKE ◽  
...  
Keyword(s):  
Water Stress ◽  
Elevated Co2 ◽  
Co2 Concentration ◽  
Italian Ryegrass ◽  
Allelopathic Effect ◽  
Irrigated Rice ◽  
Allelopathic Potential ◽  
Co2 Concentrations ◽  
Temporal Persistence ◽  
The Impact

ABSTRACT: The long temporal persistence of select herbicides negatively impacts crops sown in succession to irrigated rice. One way to reduce these compounds in the soil over time is through phytoremediation. However, elevated CO2 concentrations may interfere with the phytoremediation process. Another consequence of climate change is the production of allelopathic compounds by forage species used as remedial agents. This study aimed to evaluate the impact of elevated CO2 concentration and drought stress on the remediation of soil samples contaminated with imazapyr + imazapic herbicides by Italian ryegrass and any subsequential affect on the allelopathic effect of this species. We report that the increasing CO2 decreased the phytoremediation potential of ryegrass. Water stress combined with a CO2 concentration of 700 µmol mol-1 caused increased allelopathy. Overall, these are the first data to indicate a significant effect of higher CO2 levels with respect to both phytoremediation efficacy and allelopathic potential of the plant species used in phytoremediation.

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