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Investigation:

TG-04 (Martens / Moraes / Victoria / Moreira )

LBA Dataset ID:

TG04_Radon_Flux

Originator(s):

1. Martens, Christopher S.
2. Moraes, Osvaldo Luiz Leal de
3. Crill, Patrick Michael
4. Mendlovitz, Howard P.
      5. Moura, Jose Mauro
6. Shay, Tom
7. Saleska, Scott R.
8. Wofsy, Steven C.

Point(s) of Contact:

Mendlovitz, Howard P. (mendlovitz@unc.edu)
Martens, Christopher S. (cmartens@email.unc.edu)

Dataset Abstract:

Radon-222 is used as a transport tracer of forest canopy-atmosphere CO2 exchange in an old-growth, tropical rain forest site near km 67 of the Tapajos National Forest, Para, Brazil; the km 77 Pasture Tower Site; and the km 83 logged forest site. Initial results, from month-long periods at the end of the wet season (June-July) and the end of the dry season (Nov-Dec) in 2001, demonstrate the potential of new radon measurement instruments and methods to quantify mass transport processes between forest canopies and the atmosphere. Gas exchange rates yield mean canopy air residence times ranging from minutes during turbulent daytime hours to greater than 12 hours during calm nights. Radon is an effective tracer for net ecosystem exchange of CO2 (CO2 NEE) during calm, nighttime hours when eddy covariance-based NEE measurements are less certain because of low atmospheric turbulence. Radon-derived nighttime CO2 NEE (9.00 +/- 0.99 umol m-2 s-1 in the wet season, 6.39 +/- 0.59 in the dry season) was significantly higher than raw uncorrected, eddy covariance-derived CO2 NEE (5.96 +/- 0.51 wet season, 5.57 +/- 0.53 dry season), but agrees with corrected eddy covariance results (8.65 +/- 1.07 wet season, 6.56 +/- 0.73 dry season) derived by filtering out lower NEE values obtained during calm periods using independent meteorological criteria. The radon CO2 results suggest that uncorrected eddy covariance values underestimate nighttime CO2 loss at this site. If generalizable to other sites, these observations indicate that previous reports of strong net CO2 uptake in Amazonian terra firme forest may be overestimated. These final and corrected data are available for the years 2000-2004.

Beginning Date:

2000-04-23

Ending Date:

2004-12-06

Metadata Last Updated on:

2013-05-14

Data Status:

In Preparation for Archive

Access Constraints:

Public

Data Center URL:

http://daac.ornl.gov

Distribution Contact(s):

ORNL DAAC User Services (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):

Citation Information - Other Details:

Martens, C.S., O.L.L. de Moraes, P.M. Crill, H.P. Mendlovitz, J.M. Moura. 2013. LBA-ECO TG-04 Radon Flux Data from Forests and Pasture in the Brazilian Amazon: 2000-2004. Data set. Available on-line [http://www.daac.ornl.gov] from Oak Ridge National Laboratory Distributed Active Archive Center, Oak Ridge, Tennessee, U.S.A.

Keywords - Theme:

Parameter Topic Term Source Sensor
TRACE GASES ATMOSPHERE-BIOSPHERE INTERACTIONS ATMOSPHERIC CHEMISTRY FIELD INVESTIGATION RADON DETECTOR
NET ECOSYSTEM EXCHANGE ATMOSPHERE-BIOSPHERE INTERACTIONS ATMOSPHERIC CHEMISTRY    

Uncontrolled Theme Keyword(s):  Gas Flux, Radon, Rn-222, gas exchange

Keywords - Place (with associated coordinates):

Region
(click to view profile)
Site
(click to view profile)
North South East West
Para Western (Santarem) km 67 Primary Forest Tower Site -2.85700 -2.85700 -54.95900 -54.95900
Para Western (Santarem) km 77 Pasture Tower Site -3.02020 -3.02020 -54.88850 -54.88850
Para Western (Santarem) km 83 Logged Forest Tower Site -3.01700 -3.01700 -54.97070 -54.97070

Related Publication(s):

Martens, C.S., T.J. Shay, H.P. Mendlovitz, D.M. Matross, S.R. Saleska, S.C. Wofsy, W.S. Woodward, M.C. Menton, J.M.S. De Moura, P.M. Crill, O.L.L. De Moraes, and R.L. Lima. 2004. Radon fluxes in tropical forest ecosystems of Brazilian Amazonia: night-time CO2 net ecosystem exchange derived from radon and eddy covariance methods. Global Change Biology 10(5):618-629.

Data Characteristics (Entity and Attribute Overview):

Data Characteristics:

Data are provided as 16 tab-delimited ASCII csv files, organized in separate directories for each study site.




File naming conventions:

Files are named as follows:

Radon_AAkm_yyyy.txt

where

AA refers to the kilometer number: 67 (km67), 77 (km77), or 83 (km83)

yyyy indicates the sample year, e.g. 2000



For the years where detectors were added and redistributed (km67 and km83 sites) two files are available each identified by the dates included in the title so for those years the file names are RadonAAkm_yyyymmdd_yyyymmdd.csv




File organization and contents:




File name,Radon_67km_2000.csv,,,,,,,,,

File date: 6-May-2013,,,,,,,,,,

Associated LME file: TG-04_Radon_Flux,,,,,,,,,,

,,,,,,,,,,

Column,Column_heading,Unit/format,Explanation,,,,,,,

1,Year,,Year in which samples were collected,,,,,,,

2,Date,YYYYMMDD,Sampling date in local time,,,,,,,

3,Time,HH:MM:DD,Start of the 15 minute sampling period in local time (local time- GMT-4),,,,,,,

4,Rn_30,mBq per m3,Activity of radon at 0.3 meters above the ground reported in milliBequerels per meter cubed (mBq per m3),,,,,,,

5,Rn_100,mBq per m3,Activity of radon at 1.0 meter above the ground reported in milliBequerels per meter cubed (mBq per m3),,,,,,,

6,Rn_300,mBq per m3,Activity of radon at 3.0 meters above the ground reported in milliBequerels per meter cubed (mBq per m3),,,,,,,

7,Rn_1070,mBq per m3,Activity of radon at 10.7 meters above the ground reported in milliBequerels per meter cubed (mBq per m3),,,,,,,

8,Rn_3200,mBq per m3,Activity of radon at 32.0 meters above the ground reported in milliBequerels per meter cubed (mBq per m3),,,,,,,

9,Rn_3700,mBq per m3,Activity of radon at 37.0 meters above the ground reported in milliBequerels per meter cubed (mBq per m3),,,,,,,

10,Rn_4720,mBq per m3,Activity of radon at 47.2 meters above the ground reported in milliBequerels per meter cubed (mBq per m3),,,,,,,

11,Rn_6100,mBq per m3,Activity of radon at 61.0 meters above the ground reported in milliBequerels per meter cubed (mBq per m3),,,,,,,

,,,,,,,,,,

,Data flagged and removed as bad are indicated by -9999,






Example Data Records (Radon_67km_2000.csv),

Year,Date,Time,Rn_30,Rn_100,Rn_300,Rn_1070,Rn_3200,Rn_3700,Rn_4720,Rn_6100

2000,20000423,13:45:00,13,-9999,-9999,-9999,-9999,-9999,-9999,-9999

2000,20000423,14:00:00,-9999,-9999,-9999,-9999,-9999,-9999,-9999,-9999

2000,20000423,14:15:00,-9999,-9999,-9999,-9999,-9999,-9999,-9999,-9999

2000,20000423,14:30:00,-9999,-9999,-9999,-9999,-9999,-9999,-9999,-9999

2000,20000423,14:45:00,-9999,-9999,-9999,-9999,-9999,-9999,-9999,-9999

2000,20000423,15:00:00,-9999,-9999,-9999,-9999,-9999,-9999,-9999,-9999

2000,20000423,15:15:00,-9999,-9999,-9999,-9999,-9999,-9999,-9999,-9999

2000,20000423,15:30:00,-9999,-9999,-9999,-9999,-9999,-9999,-9999,-9999

.....

2000,20001231,22:30:00,12.139,12.608,9.06,7.998,7.246,2.773,2.887,2.731

2000,20001231,22:45:00,11.928,10.662,7.534,8.457,7.407,4.438,2.17,2.464

2000,20001231,23:00:00,13.687,11.69,8.39,7.538,7.567,3.583,2.306,3.188

2000,20001231,23:15:00,12.315,11.91,10.959,9.446,7.727,5.697,2.716,2.769

2000,20001231,23:30:00,13.687,11.69,9.88,8.068,-9999,4.438,2.716,3.949

2000,20001231,23:45:00,12.948,10.735,9.396,7.821,-9999,5.022,2.716,3.188

Data Application and Derivation:

Radon-222 is used as a transport tracer to quantify mass transport processes between forest canopies and the atmosphere. Gas exchange rates yield mean canopy air residence times ranging from minutes during turbulent daytime hours to greater than 12 hours during calm nights. Radon is an effective tracer for net ecosystem exchange of CO2 (CO2 NEE) during calm, nighttime hours when eddy covariance-based NEE measurements are less certain because of low atmospheric turbulence.

Quality Assessment (Data Quality Attribute Accuracy Report):

Quality Assessment:

Calibration



The detectors for the continuous-sampling flowthrough system were calibrated regularly using a Ra-226 RNC Rn source, serial number 106. This source was commercially produced by Pylon Electronic Inc. (Ottawa, Ontario, Canada). The calibration was a two-step procedure. First, a Rn-free gas was introduced to the detector at 1 L per min using a mass flow controller to ensure accurate and precise delivery. This allowed us to correct for background noise within

each detector. Then the known Rn source was added in series to calculate the sensitivity calibration coefficient. Both steps were run for a minimum of 24 h to obtain adequate counting statistics. In addition, the system is checked monthly with a field calibration. During this 2-day period, all detectors were valved to the same atmospheric gas. This procedure allowed us to check for detector stability and make necessary corrections.



The flow-through detectors proved to have a precision of better than plus or minus 0.74 Bq per m3 [95% confidence limits,based on a bootstrap analysis (Efron & Gong, 1983)] of Rn activity based on binning 15 min of counts.

Process Description:

Data Acquisition Materials and Methods:

Site



Measurements were made from the three eddy flux towers located in and near the

Tapajos National Forest, Para, Brazil. The towers are identified by the nearest kilometer marker on the BR 163 highway which runs south from the city of Santarem to the city of Cuiba.

Annual mean temperature in the area is 25 degrees C (Silver et al. 2000). The rainy season extends from late December or early January through June. The duration of the rainy period varies from year to year. Vegetation at the site is evergreen, mature tropical forest with a total biomass of about 372 Mg per ha (Keller et al. 2001). The study site is located on an old, nearly flat, erosional remnant plateau with well-drained soils.



Km 83 tower

This tower was located within the Tapajos National Forest. The site was selectively logged starting in September 2001. Forest extended 5 km to the east, 8 km to the south, and 40 km to the north of the tower before reaching pasture. The site was on a flat plateau (the planalto) that extended many kilometers to the north, south, and east. Forest continued 8 km west to

the edge of the planalto before dropping to the Tapajos River 14 km from the tower. The total relief within 1 to 2 km of the tower was approximately 10 m, with occasional 10 to 30 m deep stream gullies farther from the tower.



Km 77 tower

The agricultural site flux tower stands in an approximately 500 ha field surrounded by primary and secondary forest with a 40m tall average canopy height. The tower is 25km from the 15km wide Tapajos River on terrain that slopes at about 4.81 from west to east. To the east, a small spring-fed lake 460m from the tower, surrounded by small trees and shrubs, lies at the bottom of the slope (about 39m below the tower level). The soil type is yellow

latosol (Raimundo Cosme,EMBRAPA, personal communication). When the field was used for grazing, the field was planted in a commonly used grass species, Brachiara brizantha. When in pasture, the cattle density was approximately one animal per hectare. In the process of introducing upland rice, the pasture was burned on November 14, 2001, and over the next few days the field was plowed. Rice predominantly of the type cirad (Oryza sativa L.), a nonirrigated

rice, was planted on February 24, 2001. The field was not replanted in 2002. For more details on the km 77 site see Sakai et al. 2004.



Km 67 Tower

The site is located in the Tapaj6s National Forest accessed by an entrance road at kilometer 67 along the Santarem-Cuiaba Highway (BR-163). The eddy-flux tower was installed 1 km east of the access road.





Methods

Continuous Rn-222 activity profiles within and above the forest canopy were measured with detector array systems of eight or more flow-through detectors controlled by custom software on portable computers.The same computers were also used for data storage.The flow-through detectors proved to have a precision of better than plus or minus 0.74 Bq per m3 [95% confidence limits,based on a bootstrap analysis (Efron and Gong, 1983)] of Rn activity based on binning 15 min of counts. The detector arrays included a nafion tubing

water removal system that utilized recirculated pump air to exhaust water vapor removed from ambient air arriving from eight sampling heights on the tower.



The flow-through detector is based on a pulse-ionization Rn counting air chamber. The counting chamber consists of a large sealed aluminum vessel (approximately 20 L active sample volume) with coaxially mounted ion collection electrode. The air sample to be analyzed is introduced into the chamber at flow rates (approximately 1 L per min) consistent with an adequate sample exchange rate. Up to eight counting chambers may be connected in a single detector system. Alpha particles released through decay of Rn-222 in the air sample volume and Po-218 and Po-214 in the air sample or adsorbed on the central

electrode provide the fundamental basis for Rn assay. Negative and positive ions produced along alpha-particle ionization tracks drift towards chamber walls and a central electrode, respectively, producing pulses in the central electrode. After amplification these pulses are counted. Control of the detector system and compilation and management of accumulated

data files is performed by a standard notebook-format MSDOS-compatible PC.



At the km 67 tower 8 detectors were installed in April 2000. In October 2003 4 additional detectors were added and the original detectors redistributed to cover the profile between 0.1 m and 62.24 meters above the ground.



Similarly at the km 83 tower 8 towers were installed in May 2000 and 4 additional detectors were added on June 4 2001 with the original detectors redistributed on the same date.

At the km 77 tower there were 4 detectors installed on January 1 2001. The detector originally placed at 10 m above the ground was relocated to 11.5 m above ground on December 12 2001 but no additional detectors were added.

References:

Efron B, Gong G (1983) A leisurely look at the bootstrap, the jackknife, and cross-validation. American Statistician, 37:36–48.



Keller, M., M. Palace, and G. Hurtt. (2001) Biomass estimation in the Tapajos National Forest, Brazil-examination of sampling and allometric uncertainties. Forest Ecology and Management 154:371-382.





Sakai, R. K., D. R. Fitzjarrald, O. L. L. Moraes, R. M. Staebler, O. C.

Acevedo, M. J. Czikowsky, R. da Silva, E. Brait, and V. Miranda (2004),

Land-use change effects on local energy, water and carbon balances in an

Amazonian agricultural field, Global Change Biol., 10: 1– 13.



Silver, W. L., J. Neff, M. McGroddy, E. Veldkamp, M. Keller, and R. Cosme. (2000). Effects of soil texture on belowground belowground carbon and nutrient storage in a lowland Amazonian forest ecosystem. Ecosystems 3:193-209.

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