scholarly journals Diurnal sampling reveals significant variation in CO2 emission from a tropical productive lake

2014 ◽  
Vol 74 (3 suppl 1) ◽  
pp. S113-S119 ◽  
Author(s):  
PCJ Reis ◽  
FAR Barbosa
Keyword(s):  
Co2 Emission ◽  
Co2 Flux ◽  
Tropical Lakes ◽  
Southeastern Brazil ◽  
Diurnal Changes ◽  
Lake Metabolism ◽  
Temperature Trends ◽  
Air Water Interface ◽  
Net Heterotrophy ◽  
Co2 Dynamics

It is well accepted in the literature that lakes are generally net heterotrophic and supersaturated with CO2 because they receive allochthonous carbon inputs. However, autotrophy and CO2undersaturation may happen for at least part of the time, especially in productive lakes. Since diurnal scale is particularly important to tropical lakes dynamics, we evaluated diurnal changes in pCO2and CO2 flux across the air-water interface in a tropical productive lake in southeastern Brazil (Lake Carioca) over two consecutive days. Both pCO2 and CO2 flux were significantly different between day (9:00 to 17:00) and night (21:00 to 5:00) confirming the importance of this scale for CO2 dynamics in tropical lakes. Net heterotrophy and CO2 outgassing from the lake were registered only at night, while significant CO2 emission did not happen during the day. Dissolved oxygen concentration and temperature trends over the diurnal cycle indicated the dependence of CO2 dynamics on lake metabolism (respiration and photosynthesis). This study indicates the importance of considering the diurnal scale when examining CO2emissions from tropical lakes.

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 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 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 Environmental factors regulating winter CO<sub>2</sub> flux in snow-covered boreal forest soil, interior Alaska

2012 ◽  
Vol 9 (1) ◽  
pp. 1129-1159 ◽  
Author(s):  
Y. Kim ◽  
Y. Kodama
Keyword(s):  
Environmental Factors ◽  
Soil Temperature ◽  
Forest Soil ◽  
Atmospheric Pressure ◽  
Co2 Emission ◽  
Black Spruce ◽  
Co2 Flux ◽  
Atmospheric Temperature ◽  
Spruce Forest ◽  
Interior Alaska

Abstract. Winter CO2 flux is an important element to assess when estimating the annual carbon budget on regional and global scales. However, winter observation frequency is limited due to the extreme cold weather in sub-Arctic and Arctic ecosystems. In this study, the continuous monitoring of winter CO2 flux in black spruce forest soil of interior Alaska was performed using NDIR CO2 sensors at 10, 20, and 30 cm above the soil surface during the snow-covered period (DOY 357 to 466) of 2006/2007. The atmospheric pressure was divided into four phases: >1000 hPa (HP: high pressure); 985<P<1000 (IP: intermediate pressure); <986 hPa (LP: low pressure); and a snow-melting period (MP); for the quantification of the effect of the environmental factors determining winter CO2 flux. The winter CO2 fluxes were 0.22 ± 0.02, 0.23 ± 0.02, 0.25 ± 0.03, and 0.17 ± 0.02 gCO2-C/m2 d−1 for the HP, IP, LP, and MP phases, respectively. Wintertime CO2 emission represents 20 % of the annual CO2 emissions in this boreal black spruce forest soil. Atmospheric temperature, pressure, and soil temperature correlate at levels of 56, 25, and 31 % to winter CO2 flux, respectively, during the snow-covered period of 2006/2007, when snow depth experienced one of its lowest totals of the past 80 years. Atmospheric temperature and soil temperature at 5 cm depth, modulated by atmospheric pressure, were found to be significant factors in determining winter CO2 emission and fluctuation in snowpack. Regional/global process-based carbon cycle models should be reassessed to account for the effect of winter CO2 emissions, regulated by temperature and soil latent-heat flux, in the snow-covered soils of Arctic and sub-Arctic terrestrial ecosystems of the Northern Hemisphere.

scholarly journals Measuring Multi-Scale Urban Forest Carbon Flux Dynamics Using an Integrated Eddy Covariance Technique

2019 ◽  
Vol 11 (16) ◽  
pp. 4335 ◽  
Author(s):  
Kaidi Zhang ◽  
Yuan Gong ◽  
Francisco J. Escobedo ◽  
Rosvel Bracho ◽  
Xinzhong Zhang ◽  
...  
Keyword(s):  
Eddy Covariance ◽  
Green Infrastructure ◽  
Urban Forest ◽  
Scale Effects ◽  
Atmospheric Stability ◽  
Urban Forests ◽  
Co2 Flux ◽  
Forest Patches ◽  
Multi Scale ◽  
Co2 Dynamics

The multi-scale carbon-carbon dioxide (C-CO2) dynamics of subtropical urban forests and other green and grey infrastructure types were explored in an urbanized campus near Shanghai, China. We integrated eddy covariance (EC) C-CO2 flux measurements and the Agroscope Reckenholz-Tänikon footprint tool to analyze C-CO2 dynamics at the landscape-scale as well as in local-scale urban forest patches during one year. The approach measured the C-CO2 flux from different contributing areas depending on wind directions and atmospheric stability. Although the study landscape was a net carbon source (2.98 Mg C ha−1 yr−1), we found the mean CO2 flux in urban forest patches was −1.32 μmol m−2s−1, indicating that these patches function as a carbon sink with an annual carbon balance of −5.00 Mg C ha−1. These results indicate that urban forest patches and vegetation (i.e., green infrastructure) composition can be designed to maximize the sequestration of CO2. This novel integrated modeling approach can be used to facilitate the study of the multi-scale effects of urban forests and green infrastructure on CO2 and to establish low-carbon emitting planning and planting designs in the subtropics.

scholarly journals Global multi-scale segmentation of continental and coastal waters from the watersheds to the continental margins

2013 ◽  
Vol 17 (5) ◽  
pp. 2029-2051 ◽  
Author(s):  
G. G. Laruelle ◽  
H. H. Dürr ◽  
R. Lauerwald ◽  
J. Hartmann ◽  
C. P. Slomp ◽  
...  
Keyword(s):  
Continental Shelf ◽  
Co2 Flux ◽  
Global Scale ◽  
Continental Margins ◽  
Emission Rates ◽  
Large Marine Ecosystems ◽  
Multi Scale ◽  
Air Water Interface ◽  
Shelf Seas ◽  
Shelf Sea

Abstract. Past characterizations of the land–ocean continuum were constructed either from a continental perspective through an analysis of watershed river basin properties (COSCATs: COastal Segmentation and related CATchments) or from an oceanic perspective, through a regionalization of the proximal and distal continental margins (LMEs: large marine ecosystems). Here, we present a global-scale coastal segmentation, composed of three consistent levels, that includes the whole aquatic continuum with its riverine, estuarine and shelf sea components. Our work delineates comprehensive ensembles by harmonizing previous segmentations and typologies in order to retain the most important physical characteristics of both the land and shelf areas. The proposed multi-scale segmentation results in a distribution of global exorheic watersheds, estuaries and continental shelf seas among 45 major zones (MARCATS: MARgins and CATchments Segmentation) and 149 sub-units (COSCATs). Geographic and hydrologic parameters such as the surface area, volume and freshwater residence time are calculated for each coastal unit as well as different hypsometric profiles. Our analysis provides detailed insights into the distributions of coastal and continental shelf areas and how they connect with incoming riverine fluxes. The segmentation is also used to re-evaluate the global estuarine CO2 flux at the air–water interface combining global and regional average emission rates derived from local studies.

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