| NSF Org: |
EAR Division Of Earth Sciences |
| Recipient: |
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| Initial Amendment Date: | June 21, 2019 |
| Latest Amendment Date: | June 21, 2019 |
| Award Number: | 1853680 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Jonathan G Wynn
jwynn@nsf.gov (703)292-4725 EAR Division Of Earth Sciences GEO Directorate for Geosciences |
| Start Date: | August 1, 2019 |
| End Date: | July 31, 2024 (Estimated) |
| Total Intended Award Amount: | $683,756.00 |
| Total Awarded Amount to Date: | $683,756.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
500 W UNIVERSITY AVE EL PASO TX US 79968-8900 (915)747-5680 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
500 W. University Ave. El Paso TX US 79968-8900 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): |
Geobiology & Low-Temp Geochem, Instrumentation & Facilities, XC-Crosscutting Activities Pro |
| Primary Program Source: |
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| Program Reference Code(s): | |
| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.050 |
ABSTRACT
Marginal aridlands have been converted to farmlands to support increasing demand of food production. In these areas, intensive irrigation, coupled with high evapotranspiration and limited groundwater recharge, has led to accumulation of pedogenic carbonate and production of abiotic CO2 in agricultural lands. This project will be among the first to quantify such an abiotic CO2 efflux, and to define key linkages between flood irrigation, salt loading and soil-atmosphere CO2 exchange in desert agricultural soils. This project is transformative in that it examines how pedogenic carbonate formation in irrigated agricultural systems, an under-studied process but continuously magnified by human activities, impacts C cycling in one of the largest biomes on Earth. More importantly, this project has significant socioeconomic relevance at global scales, because irrigation-induced salt accumulation and elevated CO2 efflux need to be remediated through improved agricultural practice and management. This project is also highly relevant for advancing STEM education to representative population of the southwestern U.S. It will provide interdisciplinary training opportunities in Critical Zone Science, environmental geophysics and isotope geochemistry, and advanced sensor technology for both graduate and undergraduate students from primarily under-represented groups at the University of Texas at El Paso (UTEP) where 80% of student body is Hispanic. This project will directly support two Ph.D. and four undergraduate students, and provide field experience and learning opportunities to environmental science and geology majors, including two-week summer field trips. For education and outreach, hands-on activities will be presented at the annual "Earth Science Day" at UTEP, which generally attracts ~2000 visitors from the general public.
Three agricultural sites and one natural site along the Rio Grande valley, that are typical and representative of aridland settings worldwide, will be examined in the study. Geochemical, geophysical and isotopic tools will be combined with newly designed CO2 sensors to test the overarching hypothesis that "pedogenic carbonate accumulation in irrigated desert soils emits an important anthropogenically induced flux of CO2 to the atmosphere." The project will identify "naturally formed" versus "irrigation-induced" pedogenic carbonate in agricultural soils, separate "abiotic" and "oil respired" CO2 in soil gases, and monitor the spatiotemporal variation of abiotic CO2 efflux from land to atmosphere at field scales. By identifying the major controls (including irrigation intensity and chemistry, soil texture, and type of crops), expected datasets from this field-based study can be extrapolated to large regional scales and provide the first essential assessment on the potential of irrigated agriculture to modify the land-atmosphere carbon exchange.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
Agricultural fields in drylands are challenged globally by limited freshwater resources for irrigation and also by elevated soil salinity and sodicity. It is well known that pedogenic carbonate (CaCO3) is less soluble than evaporate salts and commonly forms in natural drylands. This is one of the few studies that have evaluated how irrigation loads dissolved calcium and bicarbonate to agricultural fields, accelerating formation rates of secondary calcite and simultaneously releasing abiotic greenhouse gas CO2 to the atmosphere. Our research team at University of Texas at El Paso has combined geochemical, geophysical, and isotopic tools, and different soil sensors, as well as reactive transport models, to investigate this process.
We observed much faster accumulation rates of pedogenic carbonate and much younger carbon ages in agricultural soils than those in natural soils. More importantly, the Sr isotope and C isotope ratios of these pedogenic carbonates in bulk soils are controlled by those of irrigation water, another line of evidence that most pedogenic carbonate were formed in the last 100 years and driven by soil cultivation. The production of abiotic CO2 in accompaniment with pedogenic carbonate accumulation is evident in soil gases becomes it is isotopically differently from the soil respired or biotic CO2. The project further investigated the controls in abiotic soil CO2 production and transport. Soil texture, irrigation intensity and irrigation water quality are identified as the major variables. Finer soil particles lower the water infiltration and subject the soil to more evaporation, leading to more salt buildup, accumulation of pedogenic carbonate and abiotic CO2 release than coarse soils. The amount of water used for each irrigation, numbers of irrigation events for each growing season, and water quality of irrigation dictate the maximum loading of dissolved ions, and thus are positively correlated to the annual accumulation rates of pedogenic carbonate and emission of abiotic CO2.
Our project has not only reported one of the first studies of such “anthropogenic” pedogenic carbonates and CO2 emissions from irrigated drylands of southwestern United States, but also improved our understanding of the complex dynamics of water-soil-carbon-salt interaction. It serves as an important baseline to guide future changes in agricultural practices, as limited water resources, changes in climate, and elevated soil salinity and sodicity will challenge the future of dryland agriculture.
These results are disseminated via 19 conference presentations, 3 published papers, and 6 MS theses. We also have 3 manuscripts in review and 4 in preparation. This project supported or partially supported 1 postdoctoral scholar, 6 MS students, 1 PhD student, and 7 undergraduate students (14 female, 10 Hispanic). We have also provided field experience and learning opportunities to many environmental science majors at UTEP, a minority serving institute. Hands-on activities were presented to K-12 students and the general public in the El Paso region for education and outreach.
Last Modified: 05/28/2024
Modified by: Lixin Jin
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