PROTECT Study evaluates how CVOC chemicals are distributed and travel through the Karst System of Northern Puerto Rico

Chlorinated Volatile Organic Compounds (CVOCs) are a type of chlorinated solvent that are commonly used in industrial, business, and home settings. Some examples of common products which contain CVOCs include industrial solvents, metal surface degreasers, paint removers, and textile cleansing agents.. They are highly volatile, slightly soluble in water, and resistant to degradation, meaning they can easily dissipate, become absorbed into water, and will not break down for many years. Because of these properties, CVOCs can be transported in many ways over long distances and periods of time, and are especially difficult to remove from groundwater. Due to leakage from homes, businesses, and industries it is difficult to protect and preserve the groundwater supply from these contaminants.

The northern region of Puerto Rico has terrain characterized by the Eogenetic karst aquifer, which provides freshwater for thousands of islanders in domestic, agricultural, and industrial sectors. Karst systems are a specific type of landscape which is formed when dissolution occurs in soluble rocks[1], creating air pockets within the earth that produce a porous environment of caves and underground caverns where natural springs and water aquifers can form. Unfortunately, this region is home to many Superfund Sites and has a long history of toxic spills, chemical waste and industrial solvents released into the subsurface. Due to the porous nature of this region, the groundwater is highly vulnerable to contamination and likely a route for long-term exposure to Superfund-related contaminants.

a Location of Puerto Rico, b major streams and aquifers in Puerto Rico, c aquifer hydrogeology of the KA-NPR study area; location of potential sources of contamination in the study area; location of CVOC sampling sites. Superfund sites are identified with numbers from 1 to 12, and the name, enlisted year and contaminants are on the shown table

Recently, PROTECT Project 4 researchers published a study in the Journal of Environmental Earth Sciences where they found extensive, far reaching, and long term CVOC contamination in the Karst Region just outside of Arecibo, which could affect millions affect millions of people for years to come. The presence and distribution of contaminants throughout this region is significantly influenced by the characteristics of the aquifer, sources of contamination, and properties of the contaminant.

To complete this study, researchers used many different methods to implement analysis of CVOC data to account for the complexity of karst water systems. Using Geographical Information Systems (GIS) techniques and the kriging method of interpolation, scientists were able to determine the distribution of the different CVOCs in the aquifer and approximate the concentrations of the contaminants in the system. The temporal analysis of the data was performed near Superfund Sites where scientists observed that contamination persists more than 40 years after the original contamination occurred.

a Percent of total samples with one or more of the 7 most detected CVOCs as single entities or mixtures, b most prevalent mixtures (from the total number of mixtures)

The first author on this recent publication, PROTECT Trainee Norma Torres, explains the significance of these findings and what that means for our future. “The results of this study show how vulnerable the karst aquifers are to contamination. Contaminated groundwater in karst aquifer may affect the availability of water resources for human consumption…. People need to be aware of the importance of preserving our water resources and avoid exposition with any kind of those contaminants, which may affect people’s health. It is important to be aware that the residues of solvents, paints, or degreasers, that people may have at home, need to be properly discarded in order to avoid those chemical products reaching the aquifer.”

This study is important because it builds upon current knowledge of the fate and transport process that occurs in the highly complex karst aquifer of northern Puerto Rico. This will ultimately help researchers better understand how the system works and combat the unique and diverse set of challenges which make identifying the contamination sources and chemical behaviors of the different contaminants in the aquifer so difficult. With a better understanding of the location of the sources of contaminants and their distribution in the system, it would be possible to identify areas for remediation in the aquifer and help minimize exposure to people and surrounding ecosystems. 


[1] https://karstwaters.org/educational-resources/what-is-karst-and-why-is-it-important/

Publication Link: https://www.researchgate.net/publication/336254325_Effect_of_hydrogeological_and_anthropogenic_factors_on_the_spatial_and_temporal_distribution_of_CVOCs_in_the_karst_system_of_northern_Puerto_Rico