Source: NEW MEXICO STATE UNIVERSITY submitted to
CO2 EMISSIONS FROM THE DISSOLUTION OF SOIL CARBONATE AS A CONTRIBUTOR TO GREENHOUSE GASES
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
TERMINATED
Funding Source
NRI COMPETITIVE GRANT
Reporting Frequency
Annual
Accession No.
0186539
Grant No.
2001-35107-09943
Project No.
NM-1-5-28211
Proposal No.
2000-00568
Multistate No.
(N/A)
Program Code
(N/A)
Project Start Date
Dec 1, 2000
Project End Date
May 31, 2004
Grant Year
2001
Project Director
Monger, H. C.
Recipient Organization
NEW MEXICO STATE UNIVERSITY
1620 STANDLEY DR ACADEMIC RESH A RM 110
LAS CRUCES,NM 88003-1239
Performing Department
AGRONOMY & HORTICULTURE
Non Technical Summary
The amount of CO2 in the Earth's atmospheres continues to rise at a rate of about 0.5% per year. In the United States, carbon emission from burning fossil fuels is about 1442 x 1012 grams of carbon per year. The consequences of CO2 increase as a greenhouse gas are controversial. This controversy, however, has stimulated much scientific research on the Earth's carbon cycle. For example, research on carbon sequestration in agricultural soils has shown that U.S. cropland might be capable of sequestering about 75 to 208 x 1012 grams of atmospheric carbon per year. Grazingland soils in the U.S. might be capable of sequestering an additional 36 to 111 x 1012grams of carbon per year. In grazingland soils that occur in arid regions, most of the carbon exists as soil carbonate (CaCO3). Soil carbonate, however, in addition to being a potential sink for atmospheric CO2, is a potential source for atmospheric CO2. Carbonate as a source of CO2 could result when it is dissolved by acidic rain or acids produced by microbiotic crust. The objective of this study, therefore, is to determine if CO2 is released into the atmosphere from soil carbonate in an arid region of southern New Mexico. Subsequent studies will focus on rangeland management that can curtail CO2 losses from carbonate and promote carbon sequestration in vast areas used for grazing in the United States and similar dryland regions of the world.
Animal Health Component
(N/A)
Research Effort Categories
Basic
90%
Applied
10%
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
1010110206140%
1010430200040%
1010499207020%
Knowledge Area
101 - Appraisal of Soil Resources;

Subject Of Investigation
0110 - Soil; 0499 - Atmosphere, general/other; 0430 - Climate;

Field Of Science
2070 - Meteorology and climatology; 2000 - Chemistry; 2061 - Pedology;
Goals / Objectives
When acid is applied to calcium carbonate a chemical reaction occurs in which bubbles of carbon dioxide are released. This is perhaps one of the most familiar chemical reactions known to people with even a minor exposure to chemistry. The question addressed in this study centers around this reaction. When acid from acidic rain or microbiotic crust comes in contact with soil carbonate is carbon dioxide released into the atmosphere? The objective of this study, therefore, is to determine if this reaction occurs. And if so, how much carbon dioxide is released annually? This measurement is important because if we are to determine the potential of arid and semiarid soils to sequester carbon, we must know the amount of carbon released by these soils.
Project Methods
To answer the question of whether carbon dioxide is released by the dissolution of soil carbonate, we will use a statistical randomized block design of CO2 traps placed on the soil surface in an arid region of southern New Mexico. These traps will consists of a combination of soda lime powder and an infrared CO2 detector. The traps are inverted containers that allow water to enter and soak into the soil, yet due to a one-way valve, CO2 is not allowed to escape before being measured. In order to distinguish biologically-respired CO2 from carbonate-dissolved CO2, we will measure the carbon isotopes. From previous work on the soils we are studying, we know that biologically- respired CO2 has less 13C than carbonate-dissolved CO2. Therefore, we will be able to measure the relative contributions of CO2 from these two sources.

Progress 12/01/00 to 05/31/04

Outputs
We tested this hypothesis by comparing the amount of CO2 and the 13C of CO2 released from the three soil types. Using a randomized complete block design, CO2 emissions were measured using NaOH and soda lime traps from June 2002 to October 2003. Neither NaOH traps nor soda lime traps detected any statistical difference in cumulative CO2 emissions from the three soil types at the alpha = 0.05 level. Moreover, the isotopic analysis of CO2 did not match the isotopic values of pedogenic carbonate, nor were there any statistical differences (alpha = 0.05) in delta13C of CO2 among the three soil types. We conclude, therefore, that exhumed petrocalcic horizons are not actively emitting CO2 at a rate significantly greater than neighboring non-eroded petrocalcic soils or soils without petrocalcic horizons, and thus carbon stored in petrocalcic horizons can be considered a recalcitrant reservoir within the decadal timeframes pertinent to carbon sequestration policies. Five papers summarizing this research are in review or preparation.

Impacts
Desert soils cover about 1/3 of the Earth's land surface. They contain large amounts of carbon stored as calcium carbonate (caliche). In order to understand the potential of desert soils for capturing and storing some of the carbon put into the atmosphere by burning fossil fuel, we need to also determine if desert soils are a source, as well as a sink, for carbon dioxide. This purpose of this study is measure the amount, if any, of CO2 released from desert soil to the atmosphere when rainfall falls upon caliche exposed at the land surface.

Publications

  • No publications reported this period


Progress 01/01/03 to 12/31/03

Outputs
We have completed weekly CO2 measurements since June 2002 at six study sites in the Jornada Basin. The measurements have been made using NaOH and soda lime traps. The NaOH is titrated and the soda lime is weighed to obtain CO2 emission rates. We have also monitored rainfall at the study sites and plotted CO2 emissions versus rainfall. In order to discern whether the CO2 is from dissolution of carbonates or plant and microbial respiration we have taken gas samples once each month for carbon isotope analysis. These samples are stored in vials and analyzed using our recently-purchased mass spectrometer. Plant types and their abundance have been measured for each of the study sites. CO2 emissions measured with soda lime and NaOH traps reveal that soils with exhumed carbonate do not have higher CO2 emissions than non-eroded soils with carbonate or soils without carbonate. The isotopic analysis reveals that CO2 emissions are from respiration rather than dissolution of carbonates. These data will be included in a Ph.D. dissertation, published in referred scientific journals, and made available to the public via the Jornada LTER web site.

Impacts
Storing carbon as the result of management practices has the potential to not only help curtail increases in atmospheric CO2, but also to increase the quality of New Mexico rangelands.

Publications

  • No publications reported this period


Progress 01/01/02 to 12/31/02

Outputs
We have completed weekly CO2 measurements since June 2002 at six study sites in the Jornada Basin. The measurements have been made using NaOH and soda lime traps. The NaOH is titrated and the soda lime is weighed to obtain CO2 emission rates. We have also monitored rainfall at the study sites and plotted CO2 emissions versus rainfall. The data show pulses of CO2 after rain. In order to discern whether the CO2 is from dissolution of carbonates or plant and microbial respiration we have taken gas samples once each month for carbon isotope analysis. These samples are stored in vials and will be analyzed this spring using our recently-purchased mass spectrometer. Plant types and their abundance have been measured for each of the study sites. CO2 emissions measured with soda lime and NaOH traps have been compared to CO2 emissions measured by Bowen Ratio methods at the Jornada Experimental Range. These data will be included in a Ph.D. dissertation, published in refereed scientific journals, and made available to the public via the Jornada LTER web site.

Impacts
Storing carbon as the result of management practices has the potential to not only help curtail global warming, but also to increase rangeland health.

Publications

  • Monger, H.C. 2002. Pedogenic carbonate: links between biotic and abiotic CaCO3. p. 897-1 to 897-9. In Transactions of the 17th World Congress of Soil Science, Bangkok, Thailand.
  • Monger, H.C. 2002. Pedogenic carbonate: links between biotic and abiotic CaCO3. p. 796 In Abstracts, Volume II, Symposia 13-21. 17th World Congress of Soil Science, Bangkok, Thailand.
  • Mitchell, K.A., D.B. Peters, H.C. Monger, and J. Herrick. 2002. Long-term changes in carbon pools accompanying shrub invasion of a desert grassland: the Jornada Experimental Range 1850-Today. Annual Meeting of the Ecological Society of America, 2002. Tucson, Arizona.


Progress 01/01/01 to 12/31/01

Outputs
The purpose of this study is to measure the amount of CO2 released from desert soils to the atmosphere. Specifically, we want to determine if emissions of CO2 from soil carbonate that have been exposed by erosion are greater than neighboring soils in which carbonate has not been exposed. To this end, we have completed our selection of plots and marked them with a GPS. We have also conducted lab experiments to determine the accuracy of our CO2 traps, which consist of liquid NaOH or solid soda lime. These experiments involved adding know amounts of CO2 to the traps then determining the amount indicated by the traps. From these experiments, NaOH traps showed more variability than soda lime traps. We have also used an infrared detector to measure CO2 fluctuations before and after rain. Values of CO2 ranged from 280 ppm during dry periods to 1000 ppm after rain.

Impacts
Storing carbon as the result of management practices has the potential to not only help curtail global warming, but also to increase rangeland health.

Publications

  • MONGER, H.C., J.J. Martinez-Rios, R.A. Gallegos. 2001. Carbon sequestration and global warming p 1-7. In J.M. Navarro, C.S. Calzada, and A. Martinez-Rios (eds.) Memoria de la XIII Semana Internacional de Agronomia.
  • MONGER, H.C. 2001. Carbonate-C sequestration in arid and semiarid soils. Soil Survey and Land Resource Workshop. Texas A&M University.