Impact of Lagoon Leakage at Confined Animal Feeding Operations in Nebraska on Shallow Ground Water Nitrate Concentrations and N-Isotope Variability

Authors

Sadayappan Mariappan, University of Nebraska-Lincoln

Date of this Version

12-2001

Document Type

Thesis

Citation

Thesis (M.S.)—University of Nebraska—Lincoln, 2001. Department of Agronomy.

Comments

Copyright 2001, the author. Used by permission.

Abstract

The two-year study of the environmental impact of waste lagoons on ground water quality as 13 CAFOs in the eastern two-thirds of Nebraska is complete. The investigation used the δ¹⁵N values of NH₄-N and NO₃-N as source indicators.A N-isotope response to different lagoon designs and management practices was apparent as the δ¹⁵N values in the lagoons, which ranged from +2.0%₀ to 59.0%_0.

Results indicated that the anomalously low δ¹⁵N values at lagoon HB-3 were associated with continuous N-isotope dilution by the addition of fresh waste and short residence time in the lagoon. Its δ¹⁵N values in the lagoons, which ranged from +2.0%₀ to +59.0%_0.

Results indicated that the anomalously low δ¹⁵N values at lagoon HB-3 were associated with continuous N-isotope dilution by the addition of fresh waste and short residence time in the lagoon. Its δ¹⁵N enrichment factor was -17.6. The anomalously high δ¹⁵N value (+59%₀) at wastewater overflow lagoon at Wayne (HW-9-O) appears to result from volatilization during warm season when waste overflow ceases from the primary lagoon. The enrichment factor for the overflow lagoon was -15.4 and the primary lagoon was -35.9.In a newly constructed lagoon, δ¹⁵N values increased from +6.4%₀ to +16.7%₀ within a year and a half of operation.

A strong correlation coefficient (r=0.97) between the δ¹⁵N of NH_4-N and δ¹⁵N of TKN indicated that there is little isotopic fractionation in the ammonification of urea and other organic amines in the waste and / or the δ¹⁵N contribution from ammonia in much greater than that organic-N.The δ¹⁵N values of lagoon surface samples indicated that there was not a significant difference in δ¹⁵N values regardless of sampling location.During the warmer months, vertical stratification of the lagoon developed with the surface δ¹⁵N values being higher than those at the bottom.

Ground water beneath ten of 13 CAFOs was not adversely impacted by lagoon leakage.NH₄-N with enriched δ¹⁵N values occurred in downgradient shallow ground water at two CAGO lagoons.From a standpoint of soil texture and depth to ground water, these lagoons were constructed in highly vulnerable areas. Beneath three CAFOs, ground water DOC from lagoon leakage promoted in-situ biodenitrification and reduced downgradient NO₃-N concentrations. The ground water quality beneath a decommissioned lagoon was severely contaminated by high NO₃-N with enriched δ¹⁵N values leached from beneath the filled-in lagoon.

Advisor:Roy F. Spalding