Ground Water Remediation Project
B.S. Miller, M.P. Russelle, J.F.S. Lamb, C.P. Vance, and A.L. Malan
In February of 1989 a train derailment in central North Dakota impacted ground water with nitrate and ammonium nitrogen. Since the derailment, excavation of impacted soil along with irrigating wheat and corn crops with impacted ground water has not significantly reduced nitrate concentrations. In 1996 a new remediation method was implemented to clean up the spill site by utilizing impacted water to produce a high value agricultural crop while minimizing potential increased ground water contamination. The work is a cooperative effort between USDA-ARS, Carrington Research Extension Center, and Braun Intertec Corporation and involves four principle components:
1) Use a deeply rooted long season perennial crop that has high yield, water use, and nitrogen uptake potential;
2) Pump impacted ground water on relatively large areas at rates that do not greatly exceed the N uptake capacity of the crop and that minimize yield reductions due to water stress;
3) Optimize irrigation management to minimize nitrate concentration and water movement beneath the root zone; and
4) Evaluate the ability of standard (effective) and ineffective alfalfa to remove nitrates from the subsoil.
Alfalfa was selected due to its high water requirements, high yield potential, its ability to remove nitrates from deep in the soil profile, and its ability to reduce nitrates in irrigation water as the water passes through the root zone. A potential limitation to nitrate removal by alfalfa, like all legumes, is its ability to fix N from the atmosphere. For this reason ineffective types of alfalfa, alfalfa which can not fix N from the atmosphere, were developed by USDA-ARS in the early 1980's as a research and remediation tool. Ineffective alfalfa needs supplemental N, much like grass crops, and will yield as much high quality forage as standard alfalfa when inorganic N supply is not limiting. Ineffective alfalfa has also been found to be 30% better in the removal of nitrates from the subsoil than standard, effective alfalfa.
This remediation project offers the opportunity to test how well ineffective and standard alfalfa can remove inorganic N from an impacted shallow aquifer. This is being done by irrigating large, replicated blocks of both effective and ineffective alfalfa with the impacted ground water and monitoring hay yield, N uptake, and soil water quality as it percolates from the root zone. This project is slated to continue for five years and should demonstrate the effectiveness of this new remediation method, providing both industry and regulatory agencies the evidence needed to recommend this approach on future spill sites.
Affiliation of co-authors and non-CREC staff: M.P. Russelle, J.F.S. Lamb, C.P. Vance- USDA-ARS, St. Paul, MN; A.L. Malan-graduate student at Southern Illinois University-Edwardsville.