<i>Geospatial upscaling of atrazine’s transport using electromagnetic induction across point to field scales</i>

Abstract

Abstract. Atrazine is an herbicide commonly used to control weeds in corn crops. When it moves offsite to surface and groundwater, Atrazine becomes an environmental concern. Understanding how Atrazine moves at the field scale is vital for developing management controls. However, it is unclear if the estimation of Atrazine movement across multiple scales and depths can contribute to mitigate its effect on ecosystem services and human health across environmental managements scales. Our goal is to conceptualize the geospatial upscaling of Atrazine‘s leaching potential from point measurements to field-scale simulations in agricultural landscapes. We hypothesize that geophysical attributes of soils across point to point across a field -estimated through the use of electromagnetic induction (EMI), vadose-zone modeling, and geospatial analytics- can be used to determine and upscale the magnitude of attrazine‘s transport and uncertainties across the point-to-field scale. The study‘s objectives are three-folded: (1) estimate and simulate Atrazine‘s transport using laboratory and EMI-based transport parameters for HYDRUS 2D; (2) estimate the differences between lab- and model-based values of Atrazine; and (3) quantify the Atrazine‘s transport using geophysical attributions of soils geospatially aggregated. EMI-based estimations of Atrazine‘s transport in a silage cornfield at the Northern High Plains in the US are mapped across a field. Results indicate that each transport parameter builts a statistical significant interdependence with the apparent electrical conductivity (ECa) measured by the EMI, which leads to a robust methodology to trace atrazine‘s movement. HYDRUS 2D esimates the atrazine‘s leaching across which is not significantly different from the lab-based estimations. Also, coupling EMI technology and HYDRUS 2D modeling and the application of a geophysically-based-aggregation algorithm lead to a gradient of Atrazine transport from Silt Loams to Clay. Upscaled estimations of Atrazine loss in a season are in average 6 mg ha-1, Silt Loams have atrazine loss of 40 mg ha-1 and Clay have accumulation of atrazine of 26 mg ha-1. The errors from the upscaling process are an accumulation of +/-33%. The presented approach enables the design of improved Atrazine management practices reducing surface water and human health risks. Further studies are needed to determine the effectiveness of this approach across a wider diversity of soil types and geospatial scales.