Abstract
The objective of the study was to determine the kinetic model that best fit observed nitrate removal rates at the mesocosm scale in order to determine ideal loading rates for two future wetland restorations slated to receive pulse flow agricultural drainage water. Four nitrate removal models were investigated: zero order, first order decay, efficiency loss, and Monod. Wetland mesocosms were constructed using the primary soil type (in triplicate) at each of the future wetland restoration sites. Eighteen mesocosm experiments were conducted over two years across seasons. Simulated drainage water was loaded into wetlands as batches, with target nitrate-N levels typically observed in agricultural drainage water (between 2.5 and 10 mg L−1). Nitrate-N removal observed during the experiments provided the basis for calibration and validation of the models. When the predictive strength of each of the four models was assessed, results indicated that the efficiency loss and first order decay models provided the strongest agreement between predicted and measured NO3-N removal rates, and the fit between the two models were comparable. Since the predictive power of these two models were similar, the less complicated first order decay model appeared to be the best choice in predicting appropriate loading rates for the future full-scale wetland restorations.
Highlights
Over the decade the United States is expected to continue and intensify its focus on ecological systems and their capacity to store water and improve water quality [1,2]
The primary objectives of this study were to: (1) Create a dataset of NO3 -N removal observations over varying seasons, N loadings, and antecedent conditions for two pulse flow wetland environments at the mesocosm scale; (2) Evaluate the fit of four NO3 -N removal models with observed daily NO3 -N removal observations; and (3) Provide predictions for the maximum drainage water volumes that can be pumped into the future restored wetlands based on the kinetic model that best fit and was most practical for observed NO3 -N
The potential removal rates of NO3 -N for two distinct pulse flow wetland environments slated to receive agricultural drainage water in future wetland restoration projects were evaluated at the mesocosm scale
Summary
Over the decade the United States is expected to continue and intensify its focus on ecological systems and their capacity to store water and improve water quality [1,2]. The impacts of increased pollutant loads from non-point sources continue to threaten important economic and recreational aquatic ecosystems. These growing pollutant loads have the potential to further impair drinking water, as well as continue to threaten important aquatic dependent industries and recreational water-based environments [3]. Reactive nitrogen in drainage water entering sensitive freshwater and marine ecosystems has been found to harmfully alter these systems (e.g., acidification, toxic algae blooms, hypoxia, contamination of drinking water aquifers, loss of biodiversity) [3,9,10,11,12]
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