Analyzing Land Use and Hydrological Influences on Metals and Nutrients Recorded in an Unconfined Coastal Karstic Aquifer, Yucatán Peninsula, México

Abstract

Unconfined coastal karst aquifers are highly susceptible to contamination from anthropogenic activities, particularly in regions lacking adequate wastewater treatment. Their open hydrological structure facilitates the input and dispersion of contaminants from both point and non-point sources. Furthermore, groundwater exerts a significant influence on coastal water quality through submarine discharge that could impact vulnerable ecosystems like seagrasses, mangroves, and coral reefs. Seasonal hydrological variability—especially between dry and rainy periods—affects contaminant transport, with increased groundwater flux potentially enhancing spatial dispersion. Additionally, the balance between the contributions from the coastal karst aquifer and the hydrodynamics of the coastal zone determines the extent and degree of salinization occurring at the interface between these two systems, which in turn influences aquifer water quality. This study presents a five-year dataset of metal and nutrient concentrations measured during dry and rainy seasons in surface waters (0.5 m depth) from 24 cenotes within the Ring of Cenotes (RC), Yucatán Peninsula, Mexico. The RC functions as a preferential groundwater flow path from inland to the coast via underwater conduits and submarine groundwater discharge (SGD), transporting contaminants present in groundwater into highly vulnerable coastal ecosystems. While most parameters remained below regulatory thresholds, concentrations of total Al, Cr, Pb, and N-NH3 exceeded limits established by NOM-127-SSA1-2021 at several sites measured within the RC. Spatial heterogeneity was observed across seasons and years, driven by groundwater flux dynamics, land use, and individual sinkhole characteristics. Notably, N-NH3 concentrations were higher during the dry season, particularly near agricultural and peri-urban zones. These findings underscore the need for mandatory wastewater treatment and integrated coastal karstic aquifer management to protect the region’s sole freshwater resource and the vulnerable ecosystems in the coastal area.

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