Three-dimensional modeling of nitrate-N transport in vadose zone: Roles of soil heterogeneity and groundwater flux

Authors

Simin Akbariyeh, Northern Arizona UniversityFollow
Shannon L. Bartelt-Hunt, University of Nebraska-LincolnFollow
Daniel D. Snow, University of Nebraska - LincolnFollow
Xu Li, University of Nebraska - LincolnFollow
Zhenghong Tang, University of Nebraska - LincolnFollow
Yusong Li, University of Nebraska–LincolnFollow

Date of this Version

2018

Citation

Published in Journal of Contaminant Hydrology 211 (2018), pp 15–25.

doi 10.1016/j.jconhyd.2018.02.005

Comments

Copyright © 2018 Elsevier B.V. Used by permission.

Abstract

Contamination of groundwater from nitrogen fertilizers in agricultural lands is an important environmental and water quality management issue. It is well recognized that in agriculturally intensive areas, fertilizers and pesticides may leach through the vadose zone and eventually reach groundwater. While numerical models are commonly used to simulate fate and transport of agricultural contaminants, few models have considered a controlled field work to investigate the influence of soil heterogeneity and groundwater flow on nitrate-N distribution in both root zone and deep vadose zone.

In this work, a numerical model was developed to simulate nitrate-N transport and transformation beneath a center pivot-irrigated corn field on Nebraska Management System Evaluation area over a three-year period. The model was based on a realistic three-dimensional sediment lithology, as well as carefully controlled irrigation and fertilizer application plans. In parallel, a homogeneous soil domain, containing the major sediment type of the site (i.e. sandy loam), was developed to conduct the same water flow and nitrate-N leaching simulations.

Simulated nitrate-N concentrations were compared with the monitored nitrate-N concentrations in 10 multilevel sampling wells over a three-year period. Although soil heterogeneity was mainly observed from top soil to 3m below the surface, heterogeneity controlled the spatial distribution of nitrate-N concentration. Soil heterogeneity, however, has minimal impact on the total mass of nitrate-N in the domain. In the deeper saturated zone, short-term variations of nitrate-N concentration correlated with the groundwater level fluctuations.