Groundwater salinization patterns in the Yucatan Peninsula reveal contamination and vulnerability of the karst aquifer

The Yucatan Peninsula is one of the largest coastal and lowland karst regions worldwide. This groundwater-dependent region is highly vulnerable to contaminants that spread easily due to the karst environment. Here, the spatio-temporal patterns of major ions in 1528 water samples sourced from a government institution suggest the main factors triggering salinization in the aquifer system. The hydrogeochemical analysis, supported by dimensional reduction and network-based clustering, linked one-third of the samples to contamination outbreaks from seawater intrusion, extensive gypsum dissolution in the south, and nitrate pollution in the ubiquitous carbonate aquifer matrix. Temporal variations of water quality indicated changes in regional recharge trends and increasing human impact in recent decades. Moreover, ~23% of water samples from human-use sources exceeded acceptable sulfate and nitrate limits for drinking water purposes. The study underscores the need for continuous water quality monitoring and enhanced regional knowledge to support management plans.