Geochemical Characterization of Eutrophication within a Cenote (Sinkhole) in the Yucatán Peninsula

Groundwater is the primary source of freshwater for the Yucatán Peninsula. Cenotes, which are popular recreational sites, expose groundwater to the surface and to potential sources of contamination. This study examines a cenote that has displayed signs of eutrophication previously, with recent observations indicating high levels of turbidity and water discoloration by algae. Little is known about what is causing these conditions (natural or anthropogenic) within the cenote and what potential solutions might be. To address these questions, this project focuses on the aqueous geochemical characterization of the cenote, including measurements of nutrients (nitrate, phosphate, ammonia), major anions and cations, dissolved oxygen, pH, temperature, turbidity, and conductivity. Samples were collected to examine parameters on the surface and at depth to provide a full picture of the conditions of the cenote as they relate to eutrophication. Analyses performed include spectrophotometry, ion chromatography, and on-site measurements of field parameters with a data sonde. Given the current observations of this cenote, we expect to find high nutrient levels and low dissolved oxygen within parts of the cenote, indicating some level of eutrophication. Analysis of the data obtained has yet to be performed. Geochemical models will also be used to delineate oxidizing and reducing conditions within the cenote, examine changes in nutrient speciation with depth, and compare measured values with thermodynamic equilibrium conditions to evaluate nutrient inputs. The results will provide insights into the potential causes and reduction of eutrophic conditions and augment our understanding of water quality within cenotes since they are important both as a source of freshwater and income to support the economy in this part of the Yucatán Peninsula.