Superfund Research Program
Effect of Extreme Weather on Potential Exposure of Contaminant Mixtures in Karst Water Systems
Project Leader: Ingrid Y. Padilla (University of Puerto Rico at Mayaguez)
Co-Investigators: Damian E. Helbling (Cornell University), Philip Larese-Casanova, Raul Macchiavelli (University of Puerto Rico at Mayaguez), Dorothy Vesper (West Virginia University)
Grant Number: P42ES017198
Funding Period: 2010-2025
Research under Ingrid Padilla, Ph.D., and her team shows significant trends and factors affecting the fate, transport, distribution, and potential exposure of contaminants in karst regions. Laboratory work of non-aqueous phase (NAP) and aqueous trichloroethene (TCE) shows that concentration distributions are related to the limestone heterogeneity. Though TCE NAPs generally move downward, at high flow rates they also move through zones of non-vertical preferential flow (Carmona et al. 2020). TCE NAPs dissolves in the flowing water and is transported rapidly through conduit features. Transport in the porous rock matrix occurs through diffuse flow and rate-limited mass transfer and contribute to slow release of TCE over long periods of time. This work supports findings at the field level (Torres et al. 2019) showing widespread and persistent presence of chlorinated volatile organic contaminants in the karst regions of northern Puerto Rico (KR-NPR). Contaminant storage also occurs in in sediments containing significant fraction of organic carbon (Downey et al. 2019). Synthesis of field data show multiple contaminants present in the karst groundwater system of the KR-NPR that are reaching tap water points of exposure (Rodriguez et al. 2019 a,b). The presence is dynamic and dependent on contaminants types, source modes, and hydrogeologic characteristics of the system (Torres et al. 2018, 2019; Pantoja et al. 2020). Hydrometric (Torres et al. 2020) and tracer studies (Rodriguez et al. 2020) in the KR-NPR show transport and concentration distribution influenced by total rainfall and antecedent rainfall (TAR). Total rainfall affects rapid recharge into karst conduits, whereas TAR relates to groundwater storage component in these aquifers. Preliminary assessment using geographical information system, machine learning algorithms, and satellite imagery (Feliciano et al. 2019, 2020) identified nearly 40 percent of the areas contributing to recharge and contaminant sources to a discharge zone in the KR-NPR.