Effect of hydrogeological and anthropogenic factors on the spatial and temporal distribution of CVOCs in the karst system of northern Puerto Rico

Abstract

This study evaluates factors affecting the spatial and temporal distribution of chlorinated volatile organic contaminants (CVOCs) in the highly productive aquifers of the karst region in northern Puerto Rico (KR-NPR). Historical records from 1982 to 2016 are analyzed using spatial and statistical methods to evaluate hydrogeological and anthropogenic factors affecting the presence and concentrations of multiple CVOCs in the KR-NPR. Results show extensive spatial and temporal distributions of CVOCs, as single entities and as mixtures. It is found that at least one type of CVOC is present above detection limits in 64% of the samples and 77% of the sampling sites during the study period. CVOC distribution in the KR-NPR is contaminant-dependent, with some species being strongly influenced by the source of contamination and hydrogeological characteristics of the system. Persistent presence of CVOCs in the KR-NPR system, even after contaminated sites have been subjected to active remediation, reflect the high capacity of the system to store and slowly release contaminants over long periods of time. This study shows that karst aquifers are highly vulnerable to contamination and can serve as a long-term route of contaminants to potential points of exposure.

Storage and distribution of organic carbon in cave sediments: examples from two caves in the northern karst region of Puerto Rico

“…The high solid-water partition coe cients, controlled by the concentration of natural organic matter, lead to higher retardation factors (Table 2). Concentrations of CCl 4 , and PCE are among the highest detected contaminants in Puerto Rico's groundwater (Torres et al 2019). The fraction of organic carbon (f oc ) within the cave sediments collected in this study ranged from 0.0002-0.0236.…”

“…Groundwater contamination in this region of Puerto Rico includes chlorinated volatile organic compounds (CVOCs), pesticides, and heavy metals. Although concentrations have decreased over time, contamination has persisted for more than 40 years (Yu et al 2015, Torres et al 2019). The concentration of organic matter present in a sediment is one of the primary controls on how organic contaminants are partitioned between the sorbed and dissolved phase (Schwarzenbach et al 2016).…”