TRACING FLOW PATHS USING CONTAMINANTS IN THE COASTAL KARST AQUIFER SYSTEM ALONG THE CARIBBEAN COAST OF THE YUCATAN PENINSULA, MEXICO

The intensive tourism development and urbanization of the “Riviera Maya” along the Caribbean coast of the Yucatan Peninsula is based on the dual-use of the density-stratified aquifer. The fresh meteoric lens is the only regional source of potable water, while effluent disposal is by infiltration, or by injection into the intruding marine water. Effective water and waste management is required to maintain human and environmental health, and to achieve sustainable development. Common with many coastal carbonate aquifers, the Yucatan Peninsula has undergone multiple and over-printed phases of karstification tied to eustatic sea level fluctuations. Over 1000 km of conduit networks have been documented along the Caribbean coastline with depths ranging down to 120 m below water table, and fresh and saline groundwater velocities of km/day. Two types of passive samplers were concurrently deployed for ~1 month in each of five fresh groundwater sites to assess concentrations and distributions of anthropogenic compounds. The semipermeable membrane devices (SPMD) were analyzed for PCBs, organochlorine pesticides, PAHs, PBDEs, synthetic musks, alkylphenols, and antibacterials, while the polar organic chemical integrative samplers (POCIS) were analyzed for chlorophenoxy, stimulants, pharmaceuticals, and illicit drugs. The geographical distribution and relative concentrations of anthropogenic compounds are consistent with patterns of urbanization, land modifications including paving, and even social-cultural-economic aspects of distinct neighborhoods and tourist zones. Our test deployment substantiates the value of a network of passive sensors to map the geographical extent of urban impact zones, but also to identify active versus eustatically or otherwise abandoned flow paths. Mitigation efforts may therefore be targeted to the principal routes of land-based impact on coastal waters and the Meso-American Barrier Reef System.