<p>The co astal karstic aquifer of Puerto Morelos, Mexico, is under constant environmental stress due to leakage from poorly constructed and managed septic systems and unregulated solid waste disposal sites within and around the town. The presence of the aforementioned pollution sources in the region motivated the implementation of a contaminant transport model and particle tracking analysis, based on results from a previously constructed groundwater flow model of the local aquifer. Simulations of contaminant plumes revealed a high dilution capacity, with chloride concentrations declining to background concentration levels within approximately 300&#xa0;m from the pollution sources (disposal sites and septic systems). This dilution is attributed to the high hydraulic conductivities in the regional aquifer and the presence of a groundwater dome located beneath the urban area. The dome was shown to significantly affect local flow patterns and gradients, as particle tracking analysis indicated longer travel times farther from its center. These findings suggest that the Puerto Morelos aquifer currently exhibits a high potential for contaminant attenuation under current pollution conditions. However, with expected population and tourism growth, improvement in wastewater and solid waste disposal management practices will be paramount to minimize the risk of groundwater contamination, which is the sole source of fresh water for the Puerto Morelos community.</p>