VARIATIONS IN CONTAMINANT LEVELS AND POTENTIAL EXPOSURE IN KARST AQUIFERS CHARACTERIZED BY COMBINED CONDUIT AND DIFFUSE FLOW

Karst aquifers are highly productive groundwater systems often associated with conduit flow and high matrix permeability. These systems can be highly vulnerable to contamination, resulting in a high potential for contaminant exposure. Of particular concern is the contamination with chlorinated volatile organic compounds (CVOCs) and phthalates because of their potential association with preterm birth, the leading cause of neonatal mortality in the US. CVOCs and phthalates have been found in the karst aquifer of northern Puerto Rico, which is the most important source of groundwater in the island. This aquifer system is characterized by both conduit and diffuse flow, and has an enormous capacity to mobilize, store, and release contaminants from sources to potential exposure zones. This study assesses spatial and temporal variations in groundwater contamination in the northern karst aquifer of Puerto Rico. The assessment is conducted through analysis of historical data and field samples using GIS and temporal series evaluation. Historical water quality and hydrogeologic data is collected from literature and governmental institutions. Groundwater and tap water samples are collected and analyzed for CVOCs, phthalates, nitrates, and common ions. Preliminary results show significant spatial and temporal variations in detection frequency and concentrations of CVOCs, phthalates, and nitrates. The variations are attributed to complex interactions between contaminant sources, aquifer heterogeneities, and hydrologic conditions. A direct correlation has not yet been established between these variables and contamination outcomes, indicating a need for geospatial multi-variate analysis. The results indicate that the contamination is reaching drinking water sources, leading to potential dynamic exposure of contaminants through this karst aquifer.