Enhanced vadose zone nitrogen removal by poplar during dormancy
Hayden Ausland1, Adam Ward, Louis Licht
1a Department of Civil and Environmental Engineering , University of Iowa , Iowa City , IA.
International Journal of Phytoremediation
|June 2, 2015
Summary
Engineered poplar trees significantly reduced nitrate contamination in groundwater by enhancing denitrification. Dormant roots improved soil hydraulic properties, leading to greater nitrogen removal.
Area of Science:
- Environmental Science
- Soil Science
- Hydrology
Background:
- Industrial food processing wastewater irrigation poses a risk of groundwater nitrate (NO3(-)) contamination, especially during plant dormancy.
- Sandy soils are vulnerable to NO3(-) leaching, necessitating effective remediation strategies.
- Engineered poplar tree systems offer a potential solution for mitigating agricultural and industrial non-point source pollution.
Purpose of the Study:
- To quantify the impact of engineered poplar trees on effluent nitrate and ammonium concentrations in sandy soils.
- To assess the role of dormant roots in altering soil hydraulic properties and nitrogen cycling.
- To evaluate the effectiveness of Hydrus modeling in simulating root impacts on groundwater vulnerability.
Main Methods:
- Utilized a pilot-scale engineered poplar tree vadose zone system with intermittent synthetic wastewater dosing at 4.5°C.
- Employed bromide tracer tests to analyze root effects on soil hydraulic properties like dispersion, water content, and residence time.
- Assessed Hydrus model parameterizations to simulate dormant root influences on nitrogen transport and transformation.
Main Results:
- Rooted treatments showed significantly lower effluent NO3(-) concentrations (1.0 ± 0.72 mg-N L(-1)) compared to non-rooted treatments (5.1 ± 3.5 mg-N L(-1)) on day 21.
- Bromide tracer data confirmed that roots increased effective dispersion, water content, and residence time in sandy soils.
- Model simulations predicted 8% nitrogen conversion to N2 in rooted treatments versus 3.3% in non-rooted treatments, indicating enhanced denitrification.
Conclusions:
- Engineered poplar trees provide a substantial "root benefit" in protecting groundwater from nitrate contamination.
- Dormant roots enhance soil hydraulic properties and promote denitrification, reducing nitrogen leaching.
- The Hydrus model effectively simulates the positive impact of dormant roots on mitigating groundwater pollution.
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