A coastal karstic aquifer response to contamination. Puerto Morelos, México.

The coastal karstic aquifer of Puerto Morelos, in Mexico is under constant environmental stress due to intensive leakage of poorly constructed and managed septic systems, and unregulated solid waste disposal sites within and nearby Puerto Morelos town. The presence of the forementioned pollution sources in the region motivated the implementation of a contaminant transport model and particle tracking model based on the results of a previously implemented groundwater flow model in the local aquifer. From contaminant plume simulation it was evidenced the high dilution capacity of the aquifer as chloride concentrations greatly reduced to background concentration levels at a distance no greater than 300 meters away from the pollution sources (disposal sites and septic systems); this dilution is likely the consequence of high hydraulic conductivities in the regional aquifer and the presence of the groundwater dome. Additionally, the presence of the dome greatly influences flows and gradients in the immediate area of Puerto Morelos town, depicted by particle tracking exercise, as travel times become longer further from the epicenter of the dome. This leads to assume the local aquifer has a strong attenuation capacity for the current pollution conditions, but as population and tourism grows, wastewater and solid waste disposal practices should be improved to reduce the risk of aquifer pollution, which is the only source of fresh water for the Puerto Morelos community.