Hydrogeophysical Characterization of Swine Effluent Amended Soils in Mantled Karst

Abstract

Highlights Animal effluents can be detected in soils after minimal applications using non-intrusive characterization techniques. Swine effluent in soil produces measurable electrical signatures in the absence of chemical signatures. Electrical resistivity imaging can determine soil thickness and identify rapid transport pathways in the subsurface. Dietary additives may be good proxies to detect swine effluent in soils. Abstract. Land application of animal manures is useful for increasing many beneficial properties of soil that include fertility, productivity, and overall soil health, but can pose risks to water quality if not properly applied, especially in karstic formations. A study was carried out to assess the use of electrical resistivity and soil sampling to better characterize the transport of applied swine effluent within a mantled karst system and to assess the potential for rapid transport of swine effluent represented by Zn and other metals commonly found in effluent. This hydrogeophysical investigation was conducted at three sites, all permanent pastures, along Big Creek near Mount Judea, AR, USA, that are underlain by the Boone Limestone formation that is home to the Buffalo National River. To determine if surface electrical geophysics could be utilized to monitor the applied swine effluent within a mantled karst riparian system, this study measured the bulk electrical properties of the subsurface, characterized soil properties at the surface, and used reactive transport modeling. Electrical resistivity imaging (ERI) showed soils at sites with applied effluent were more electrically conductive than a background site. A comparison of ERI and soil sampling bulk datasets demonstrated strong trends between bulk resistivity and fluid conductance. These results enabled a more accurate definition of soil characteristics, the epikarst zone, and bedrock, along with anticipated subsurface chemical transport. Keywords: Electrical Resistivity Imaging, Epikarst detection, Soil characterization, Swine Effluent.