Mapping the Impact of Salinity Derived by Shrimp CulturePonds Using the Frequency-Domain EM Induction Method

Abstract

This study investigates groundwater salinization in a section of a coastal aquifer in RioGrande do Norte, Brazil, using frequency-domain electromagnetic (FDEM) measurements.With the global expansion of shrimp farming in ecologically sensitive coastal regions, thereis an urgent need to assess associated risks and promote sustainable management practices.A key concern is the prolonged flooding of shrimp ponds, which accelerates saltwaterinfiltration into surrounding areas. To better delineate salinization plumes, we analyzeddirect groundwater salinity measurements from 14 wells combined with 315 subsurfaceapparent conductivity measurements obtained using the FDEM method. Correlating thesedatasets improved the accuracy of salinity mapping, as evidenced by reduced variance inkriging interpolation. By integrating hydrogeological, hydrogeochemical, and geophysicalapproaches, this study provides a comprehensive characterization of groundwater salinityin the study area. Hydrogeological investigations delineated aquifer properties and flowdynamics; hydrogeochemical analyses identified salinity levels and water quality indicators;and geophysical surveys provided spatially extensive conductivity measurementsessential for detecting and mapping saline intrusions. The combined insights from thesemethodologies enable a more precise assessment of salinity sources and support the developmentof more effective groundwater management strategies. Our findings demonstratethe effectiveness of integrating geophysical surveys with hydrogeological and hydrogeochemicaldata, confirming that shrimp farm ponds are a significant source of groundwatercontamination. This combined methodology offers a low-impact, cost-effective approachthat can be applied to other coastal regions facing similar environmental challenges.