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Investigation:

CD-06 (Richey / Victoria)

LBA Dataset ID:

CD06_CO2_Exchange

Originator(s):

1. ALIN, S.R.
      2. RICHEY, J.E.

Point(s) of Contact:

ORNL DAAC User Services Office Oak Ridge National Laboratory Oak Ridge, Tennessee 37 (ornldaac@ornl.gov)

Dataset Abstract:

Outgassing of carbon dioxide (CO2) from rivers and streams to the atmosphere is a major loss term in the coupled terrestrial-aquatic carbon cycle of major low-gradient river systems (the term river system encompasses the rivers and streams of all sizes that compose the drainage network in a river basin). However, the magnitude and controls on this important carbon flux are not well quantified. We measured carbon dioxide flux rates (FCO2), gas transfer velocity (k), and partial pressures (pCO2) in rivers and streams of the Amazon river system in South America. FCO2 and k values were significantly higher in small rivers and streams (channels <100 m wide) than in large rivers (channels >100 m wide). Small rivers and streams also had substantially higher variability in k values than large rivers. Observed FCO2 and k values suggest that previous estimates of basinwide CO2 evasion from tropical rivers and wetlands have been conservative and are likely to be revised upward substantially in the future.

Beginning Date:

2004-07-01

Ending Date:

2007-01-23

Metadata Last Updated on:

2012-11-15

Data Status:

Archived

Access Constraints:

PUBLIC

Data Center URL:

http://daac.ornl.gov/

Distribution Contact(s):

ORNL DAAC User Services Office Oak Ridge National Laboratory Oak Ridge, Tennessee 37 (ornldaac@ornl.gov)

Access Instructions:

PUBLIC

Data Access:

IMPORTANT: The LBA-ECO Project website is no longer being supported. Links to external websites may be inactive. Final data products from the LBA project can be found at the ORNL DAAC. Please follow the fair use guidelines found in the dataset documentation when using or citing LBA data.
Datafile(s):

LBA-ECO CD-06 CO2 Exchange in River Systems Across the Amazon Basin: 2004-2007 :  http://daac.ornl.gov/cgi-bin/dsviewer.pl?ds_id=1136

Documentation/Other Supporting Documents:

LBA-ECO CD-06 CO2 Exchange in River Systems Across the Amazon Basin: 2004-2007 :  http://daac.ornl.gov/LBA/guides/CD06_CO2_Exchange.html

Citation Information - Other Details:

Alin, S.R., and J.E. Richey. 2012. LBA-ECO CD-06 CO2 Exchange in River Systems Across the Amazon Basin: 2004-2007. Data set. Available on-line [http://daac.ornl.gov] from Oak Ridge National Laboratory Distributed Active Archive Center, Oak Ridge, Tennessee, U.S.A. http://dx.doi.org/10.3334/ORNLDAAC/1136

Keywords - Theme:

Parameter Topic Term Source Sensor
CARBON DIOXIDE TERRESTRIAL HYDROSPHERE SURFACE WATER FIELD INVESTIGATION IR CO2 ANALYZER

Uncontrolled Theme Keyword(s):  CARBON DIOXIDE

Keywords - Place (with associated coordinates):

Region
(click to view profile)
Site
(click to view profile)
North South East West
  AMAZON BASIN -0.14200 -11.76000 -52.41700 -72.70000

Related Publication(s):

Alin, S. R., M. F. F. L. Rasera, C. I. Salimon, J. E. Richey, G. W. Holtgrieve, A. V. Krusche, and A. Snidvongs. 2011, Physical controls on carbon dioxide transfer velocity and flux in low gradient river systems and implications for regional carbon budgets, J. Geophys. Res., 116, G01009, doi:10.1029/2010JG001398.

Data Characteristics (Entity and Attribute Overview):

Data Characteristics:

Data are presented in one comma-separated ASCII file named CO2_chamber_flux_data.csv. The file is organized as follows:



File name:,CO2_chamber_flux_data.csv

File date:,5-June_2012

Associated LME file:,CD06_CO2_Exchange



Column,Column_heading,Units/format,Explanation

1,Basin,,Major river basin in which the sampling station is located

2,Location,,Sampling station location usually given as nearby municipality or local name of the igarape or lake

3,Site_code,,Unique site identifiers for sites used in other studies

4,Date,YYYMMDD,Sample collection date,

5,Time,HH:MM,Sampling time in local time reported on a 24 hour clock

6,Env_type,,Description of the sampling location with special attention to the size of the water body and flow characteristics

7,Comments,,Comments from field notebooks about sampling location

8,Collector,,Initials of the person(s) collecting the samples

9,Latitude,decimal degrees,Geographic coordinates of the sampling location in decimal degrees of latitude: where location was not measured directly it was approximated from the nearest station with measured coordinates (see accompanying documentation)

10,Longitude,decimal degrees,Geographic coordinates of the sampling location in decimal degrees of longitude where location was not measured directly it was approximated from the nearest station with measured coordinates ( see accompanying documentation)

11,Elev,km,Elevation of the sampling location reported in kilometers (km): where direct measurements were not made values were approximated from the nearest station with reported values ( see accompanying documentation)

12,Wind_spd_avg,m per s,Average windspeed measured independently for 3-5 minutes during the chamber sampling period and reported in meters per second (m per s)

13,Wind_spd_max ,m per s,Maximum windspeed from independent measures done for 3-5 minutes during the chamber sampling period and reported in meters per second (m per s)

14,RH ,%,Relative humidity of the air reported in percent (%)

15,T_air,degrees C,Air temperature reported in degrees Celcius: where direct measurements were not made an approximate value was used (see accompanying documentation)

16,T_water,degrees C,Water temperature reported in degrees Celcius: where direct measurements were not made an approximate value was used (see accompanying documentation)

17,pCO2_water ,ppm,Partial pressure of CO2 in the water reported in parts per million

18,pCO2_air,ppm,Partial pressure of CO2 in the air reported in parts per million

19,Orig_file,,File name for the original data collection file

20,Time_start,seconds,Time at which the measurements used in the determination of the gas transfer velocity began reported in seconds

21,Time_end_1 ,seconds,Time at the end of the first sampling period used in the determination of the gas transfer velocity reported in seconds

22,Time_end_2 ,seconds,Time at the end of the second sampling period used in the determination of the gas transfer velocity reported in seconds

23,Time_end_3 ,seconds,Time at the end of the third sampling period used in the determination of the gas transfer velocity reported in seconds

24,pCO2_init ,ppm,Partial pressure of CO2 in the chamber at the start of the measurement period reported in parts per million

25,pCO2_end_1 ,ppm,Partial pressure of CO2 in the chamber at the end of the first measurement period (60 s) reported in parts per million

26,pCO2_end_2 ,ppm,Partial pressure of CO2 in the chamber at the end of the second measurement period (120 s) reported in parts per million

27,pCO2_end_3 ,ppm,Partial pressure of CO2 in the chamber at the end of the third measurement period (180 s) reported in parts per million

28,Slope_regression,ppm per second,Slope of the regression between change in CO2 concentration in the chamber (y-axis) and time (x-axis) over the sampling period

29,SE_regression,ppm per second,Standard error of the slope of the regression

30,Press_atm,atm,Atmospheric pressure in the chamber reported in atmospheres

31,k_1 ,cm per hour,Gas transfer velocity calculated for the first measured time period (60 seconds)

32,k_2 ,cm per hour,Gas transfer velocity calculated for the second measured time period (120 seconds)

33,k_3 ,cm per hour,Gas transfer velocity calculated for the third measured time period (180 seconds)

34,u_star,m per s,Friction velocity reported in meters per second and calculated as described in the documentation

35,u_10,m per s,Mean windspeed at a height of 10 meters about the water surface reported in meters per second and calculated as described in the documentation

36,FCO2 ,umol CO2 per m2 per s,Air-water CO2 gas exchange flux reported in micromoles CO2 per meter squared per second



missing numeric data are indicated by -9999 and missing text data are indicated by na



Sample data for the file CO2_chamber_flux_data.csv

Basin,Location,Site_code,Date,Time,Env_type,Comments,Collector,Latitude,Longitude,Elev,Wind_spd_avg,Wind_spd_max ,RH ,T_air,T_water,pCO2_water ,pCO2_air,Orig_file,Time_start,Time_end_1 ,Time_end_2 ,Time_end_3 ,pCO2_init ,pCO2_end_1 ,pCO2_end_2 ,pCO2_end_3 ,Slope_regression,SE_regression,Press_atm,k_1 ,k_2 ,k_3 ,u_star,u_10,FCO2 ,,

Tapajos,Tapajos,na,20040717,-9999,large lake/river,na,SRA,-2.289,-54.824,0.06,-9999,-9999,-9999,29,30,425,381.53,openwater_test_june 17_slow,60,120,180,240,423.5,470.49,527.89,576.89,0.86,3.8,0.99,527,812.3,1961,-9999,-9999,6.36,,

Amazonas,Amazonas,na,20040718,-9999,large river,na,SRA,-2.454,-54.482,0.06,-9999,-9999,-9999,29,29.5,3958,348.82,rowboat,0,60,120,180,348.82,433.83,497.18,551.88,1.05,6.36,0.99,25,22,20.2,-9999,-9999,7.72,,

Amazonas,Amazonas,na,20040718,-9999,large river,na,SRA,-2.454,-54.482,0.06,-9999,-9999,-9999,29,29.5,3958,370.45,jean_samples,0,60,120,180,370.45,412.42,459.41,516.81,0.84,4.67,0.99,12.4,13.2,14.5,-9999,-9999,6.23,,

Tapajos,Tapajos,na,20040719,-9999,large lake/river,na,SRA,-2.418,-54.875,0.06,4.3,5.6,88,29,31.2,425,362.34,tapajos_june_19_1-open_channel,60,120,180,240,377.78,394.22,409.01,422.66,0.24,1.14,0.99,119,117.4,116.7,0.15,5,1.81,,

Tapajos,Tapajos,na,20040719,-9999,large lake/river,na,SRA,-2.418,-54.875,0.06,3.4,4.2,92,30,31.2,425,372.23,tapajos_june_19_2_nearshore,60,120,180,240,358.67,360.68,362.21,365.25,0.04,0.48,0.99,12.9,11.4,14.2,0.12,3.9,0.279,,

Amazonas,Amazonas,na,20040719,-9999,large river,na,SRA,-2.462,-54.63,0.06,1.3,1.8,100,28.6,29.2,6037,392.2,amazonas_6_19_1-low_fan,0,60,120,180,392.2,447.15,531.44,616.97,1.39,1.35,0.99,10.4,13.2,14.3,0.04,1.5,10.3,,

Purus,Catuaba,na,20040701,-9999,small stream,na,SRA, CIS,-10.066,-67.606,0.15,0,0,100,28.1,26,140.5,638.95,catuaba1,100,160,220,280,688.54,718.4,749.17,777.52,0.49,0.36,0.98,-77.2,-76.3,-72.8,0,0,3.65,,

Purus,Catuaba,na,20040701,-9999,small stream,na,SRA, CIS,-10.066,-67.606,0.15,0,0,100,28.1,26,140.5,607.5,catuaba4,100,160,220,280,628.41,654.93,681.96,709.55,0.45,0.49,0.98,-77.7,-76.3,-75,0,0,3.35,,

Purus,Catuaba,na,20040701,-9999,small stream,na,SRA, CIS,-10.066,-67.606,0.15,0,0,100,28.1,26,140.5,416.84,catuaba5,100,160,220,280,433.43,464.54,494.15,528.64,0.52,0.86,0.98,-155.9,-144.7,-143.3,0,0,3.83,,

Purus,Catuaba,na,20040701,-9999,small stream,na,SRA, CIS,-10.066,-67.606,0.15,0,0,100,28.1,26,140.5,453.82,catuaba6,100,160,220,280,459.01,475.62,497.91,520.99,0.37,1.91,0.98,-77.9,-88,-90.2,0,0,2.71,,

Purus,Catuaba,na,20040701,-9999,small stream,na,SRA, CIS,-10.066,-67.606,0.15,0,0,100,28.1,26,140.5,554.79,catuaba7,100,160,220,280,580.68,602.59,647.33,682.88,0.5,8.75,0.98,-72,-104,-102.4,0,0,3.73,,

Purus,Humaita,na,20040702,-9999,small stream,na,SRA, CIS,-9.751,-67.672,0.15,0.3,0.8,100,25.1,24.9,860.3,371.4,humaita1,50,110,170,230,368.96,376.61,382.08,389.25,0.11,0.75,0.98,14.8,12.8,13.2,0.01,0.3,0.809,,

Purus,Humaita,na,20040702,-9999,small stream,na,SRA, CIS,-9.751,-67.672,0.15,0.3,0.8,100,25.1,24.9,860.3,375.13,humaita2,50,110,170,230,375.52,380.58,388.02,393.36,0.1,0.57,0.98,9.9,12.3,11.7,0.01,0.3,0.714,,

Purus,Humaita,na,20040702,-9999,small stream,na,SRA, CIS,-9.751,-67.672,0.15,0.3,0.8,100,25.1,24.9,860.3,376.07,humaita3,50,110,170,230,379.73,388.11,396.17,403.68,0.13,0.28,0.98,16.5,16.3,15.9,0.01,0.3,0.978,,

Purus,Humaita,na,20040702,-9999,small stream,na,SRA, CIS,-9.751,-67.672,0.15,0.3,0.8,100,25.1,24.9,860.3,378.97,humaita4,50,110,170,230,377.56,385.74,393.61,401.48,0.13,0.29,0.98,16.1,15.9,15.9,0.01,0.3,0.973,,

Purus,Humaita,na,20040702,-9999,small stream,na,SRA, CIS,-9.751,-67.672,0.15,0.3,0.8,100,25.1,24.9,860.3,379.03,humaita7,50,110,170,230,397,415.86,432.68,449.34,0.28,1.33,0.98,38.5,36.9,36.6,0.01,0.3,2.06,,

Purus,Humaita,na,20040702,-9999,small stream,na,SRA, CIS,-9.751,-67.672,0.15,0.3,0.8,100,25.1,24.9,860.3,372.67,humaita8,50,110,170,230,388.68,406.13,423.09,439.56,0.28,0.58,0.98,35.1,35.1,35,0.01,0.3,2.08,,

Purus,Purus,na,20040705,-9999,small river,na,SRA, CIS,-9.016,-68.584,0.15,0.5,1.7,55,33.8,30.5,414,346.28,purus1,20,80,140,200,349.65,354.06,360.01,365.24,0.08,0.79,0.98,29.5,35.1,35.6,0.02,0.6,0.58,,

Purus,Purus,na,20040705,-9999,small river,na,SRA, CIS,-9.016,-68.584,0.15,0.5,1.7,55,33.8,30.5,414,388.45,purus2,20,80,140,200,390.79,405.44,433.17,443.59,0.21,5.63,0.98,123.3,194.3,167.3,0.02,0.6,1.53,,

Purus,Purus,na,20040705,-9999,small river,na,SRA, CIS,-9.016,-68.584,0.15,0.5,1.7,55,33.8,30.5,414,360.02,purus3,20,80,140,200,360.48,366.74,373.78,381.59,0.13,0.49,0.98,44.2,47.7,51.5,0.02,0.6,0.913,,

Purus,Purus,na,20040705,-9999,small river,na,SRA, CIS,-9.016,-68.584,0.15,0.5,1.7,55,33.8,30.5,414,344,purus4,20,80,140,200,349.47,360.98,372.22,385.04,0.19,0.68,0.98,78.1,79.3,85.3,0.02,0.6,1.38,,

Purus,Purus,na,20040705,-9999,small river,na,SRA, CIS,-9.016,-68.584,0.15,0.5,1.7,55,33.8,30.5,414,344.02,purus5,20,80,140,200,344.93,352.04,360.13,366.98,0.13,1.12,0.98,46.8,51,50.1,0.02,0.6,0.955,,

Purus,Iaco,na,20040705,-9999,small river,na,SRA, CIS,-9.029,-68.593,0.15,0.8,1.4,64,32.4,30.2,141.3,346.48,iaco1,20,80,140,200,349.18,369.59,391.85,413.1,0.36,0.58,0.98,-186.7,-183.4,-173.6,0.03,0.9,2.6,,

Purus,Iaco,na,20040705,-9999,small river,na,SRA, CIS,-9.029,-68.593,0.15,0.8,1.4,64,32.4,30.2,141.3,346.15,iaco2,20,80,140,200,350.2,355.47,363.86,375.37,0.16,1.09,0.98,-50.2,-63.4,-75.2,0.03,0.9,1.14,,

Negro,Negro,na,20040714,-9999,large river,na,SRA,-3.063,-60.272,0.07,2.4,3.2,100,27.8,28.7,5665,375.73,negro1,10,70,130,190,379.82,435.97,482.63,533.64,0.83,1.44,0.99,11.3,10.4,10.4,0.08,2.8,6.19,,

Negro,Negro,na,20040714,-9999,large river,na,SRA,-3.063,-60.272,0.07,2.4,3.2,100,27.8,28.7,5665,374.14,negro2,10,70,130,190,378.85,452.73,515.9,579.02,1.06,2.63,0.99,14.9,13.9,13.6,0.08,2.8,7.84,,

Negro,Negro,na,20040714,-9999,large river,na,SRA,-3.063,-60.272,0.07,2.4,3.2,100,27.8,28.7,5665,372.67,negro5,10,70,130,190,380.4,492.17,565.97,639.35,1.32,6.59,0.99,22.6,18.9,17.7,0.08,2.8,9.8,,

Negro,Negro,na,20040714,-9999,large river,na,SRA,-3.063,-60.272,0.07,2.4,3.2,100,27.8,28.7,5665,371.37,negro6,10,70,130,190,373.91,420.79,474.71,537.89,0.99,5.68,0.99,9.4,10.2,11.1,0.08,2.8,7.34,,

Data Application and Derivation:

These data (both raw and calculated parameters) are suitable for assessing surface pCO2 values and air-water gas exchange.

Quality Assessment (Data Quality Attribute Accuracy Report):

Quality Assessment:

Floating chambers generate results consistent with mass balance and injected tracer methods of measuring gas exchange when the chamber is moving at the same speed as the water surface (rather than being tethered to a stationary object) and at wind speeds less than 8 to 10 m s-1 and low to moderate wave conditions [Kremer et al., 2003; Cole et al., 2010]. Chambers with and without fans have been found to give results within the range of normal variability when used under moderately windy conditions (<5 m s-1) [Kremer et al., 2003]. These conditions were routinely met during our deployments.



Infrared gas analysis was done on a LICOR LI820 using the 14-cm optical bench with a detection range of 0 to 2000 ppm CO2 and accuracy of less than 3% of reading. The unit was zeroed and spanned every field day. In addition a standard curve was run each day using standard gases of known concentrations to verify performance(approximately 300, 1000, and 10,000 uatm CO2 in nitrogen (Scott Specialty Gases)).

Process Description:

Data Acquisition Materials and Methods:

We measured carbon dioxide flux and transfer velocity in rivers and streams with channel widths ranging from meters to kilometers. Several fieldwork campaigns occurred between June 2004 and January 2007 in the Amazon River basin, with discharge conditions ranging from low to high flow. The sampled areas span the spectrum of chemical characteristics observed across the entire basin, including, for example, both low and high pH values and suspended sediment loads.



Field Work

We measured carbon dioxide flux and transfer velocity in rivers and streams with channel widths ranging from meters to kilometers. Several fieldwork campaigns occurred between June 2004 and January 2007 in the Amazon River basin, with discharge conditions ranging from low to high flow. The sampled areas span the spectrum of chemical characteristics observed across the entire basin, including, for example, both low and high pH values and suspended

sediment loads.



Floating Chamber Method



To measure CO2 fluxes and transfer velocities, we deployed floating chambers equipped with an internal fan to circulate air through the chamber [see Sebacher et al., 1983]. The chamber (50 cm length; 20 cm width; 20 cm height)

was made of Plexiglas with a stopcock in the top to release air pressure. The chamber was connected via CO2 impermeable tubing to a portable infrared CO2 analyzer (LI820; LICOR Instruments). Air was circulated through the LI820 system via an air filter using a miniature air pump (AS200; Spectrex) with a flow of approximately 150 mL per min. Closed cell foam was used for flotation.



To take chamber measurements, we gently placed the chamber on the water surface to avoid inducing additional turbulence. Data were recorded continuously on a laptop or data logger at 1 to 5 s intervals from the time the chamber was

placed on the water for 5 min or until the CO2 accumulation curve began to flatten out.



Chamber measurements on rivers with navigable channels were executed from small boats (both river size classes) while drifting with the river current. In streams and the smallest river environments, measurements were conducted from shore, with the chamber deployed in parts of the channel where the chamber was not pulled downstream by the current and was connected to shore by way of the

lines connecting it to the gas analyzer. The rope securing the chamber to shore was not taut during any of the measurements reported here. However, these locations may not be representative of the entire cross section of the stream, as water current velocity may be lower and water depth shallower than in the main flow of the stream. These factors would tend to decrease and increase k600, respectively. Thus, these measurements may not be representative of conditions across the entire channel.





The pCO2 Measurements

We measured the partial pressure of CO2 at each site by headspace equilibration. A 1 L polycarbonate bottle was overflowed for two to three volume changes, with water pumped from the upper meter of the water column before securely sealing the bottle with a stopper fitted with stopcocks

[Hesslein et al., 1991]. A headspace of 60 mL of ambient air (collected from upwind and overhead to avoid elevated CO2 concentrations from breath and motors, for example) was introduced into the bottle while removing the

same volume of water. The bottle was shaken vigorously for at least 60 s. The headspace was then removed while the water was reinjected at the same rate. Air samples were also collected in syringes to measure air pCO2.



All pCO2 samples were measured by infrared gas analysis on a LICOR LI820 using standards of approximately 300, 1000, and 10,000 matm CO2 in nitrogen (Scott Specialty Gases). Samples were run directly from syringes within 24 h of collection or were stored in vials previously flushed with nitrogen until analysis. Vial stored pCO2 values were corrected for dilution by the nitrogen remaining in the vials after evacuation with a hand pump (15%).



Air temperature was also measured with the Kestrel 3000. Water temperature was measured with a ThermoOrion pH or dissolved oxygen probe.



Chamber Data Analysis

Air water gas exchange fluxes were calculated as follows: Equation 1



where delta(pCO2)/delta t is the slope of the CO2 accumulation in the chamber (uatm s-1), V is the chamber volume (L), TK is air temperature (in degrees Kelvin, K), S is the surface area of the chamber at the water surface (m2), and R is the gas constant (L atm K-1 mol-1) [Frankignoulle, 1988]. Fluxes

were calculated using the first 30, 60, and 90 s of the initial CO2 accumulation in the chamber. The k value measured during each chamber deployment was calculated as follows:

Equation 2



where h is the chamber height (cm), a is the Ostwald solubility coefficient (dimensionless), t is time (s), and the subscripts w, a, i, and f represent water, air, initial, and final, respectively [MacIntyre et al., 1995]. The Ostwald solubility coefficient can be calculated from K0 as a function of temperature as described by Wanninkhof et al. [2009]. To compare gas transfer velocity values among sites, k values were normalized to a temperature of 20 degrees C (i.e., k600) using the following equation: Equation 3



with T in degrees Celsius [Wanninkhof, 1992]. where kT is the measured k value at the in situ temperature (T), ScT is the Schmidt number for temperature T, and the Schmidt number for 20 degrees C in freshwater is 600 [Jahne et al.,

1987]. The Schmidt value for freshwater is calculated as a function of temperature: Equation 4



In addition to chamber and pCO2 measurements, we measured wind speed and air and water temperatures. Wind speed was measured for 3 to 5 min at the time of flux measurements using a handheld anemometer (Kestrel 3000) facing into the wind at approximately 1.5 m above the water surface. Wind speeds were averaged over the period of the flux measurement as described by Borges et al. [2004a, 2004b]. Wind speeds were normalized to a height of 10 m above the surface using the following equation:

Equation 5



where u_bar subz is mean wind speed (m per s) at the height z, u star is friction velocity (m sâËâ� Ã¢Ã¯Â¿Â½â„¢1), kappa is von Karman\'s constant (approximately 0.40), and z0 is roughness length (10.5 m, an intermediate value for water surfaces) [Oke, 1988]. Friction velocity was first calculated by rearranging equation (5) to solve for u_star and using the mean wind speed measured at 1.5 m as z.

References:

Borges, A. V., et al. (2004a), Gas transfer velocities of CO2 in three European estuaries (Randers Fjord, Scheldt, and Thames), Limnology and Oceanography, 49, 1630 1641.



Borges, A. V., et al. (2004b), Variability of the gas transfer velocity of CO2 in a macrotidal estuary (the Scheldt), Estuaries, 27, 593�603.



Cole, J.J., et al. (2010), Multiple approaches to estimating air-water gas exchange in small lakes, Limnology & Oceanography: Methods, 8: 285-293.



Frankignoulle, M. (1988), Field measurements of air-sea CO2 exchange, Limnology and Oceanography, 33, 313�322.



Jahne, B., K. Mannich, R. Dutzi, W. Huber, and P. Libner (1987), On the

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