Hydrolysis of Organic Contaminants: Improving Laboratory Studies to Accurately Predict Environmental Transformation Rates

Abstract

Hydrolysis reactions comprise a widely studied class of abiotic transformation processes that impact the environmental fate of many organic contaminants. While hydrolysis rates are typically measured in buffered solutions in order to predict transformation rates in the environment, rate constants measured in laboratory buffers are often higher than values in corresponding natural water samples. In this Perspective, we summarize these discrepancies and prior explanations provided for their occurrence. Through modeling using two linear free energy relationships (i.e., the Swain–Scott and the Bro̷nsted relationships), we propose a simple but overlooked alternative explanation─namely, that hydrolysis reactions are often much more sensitive to constituents in laboratory buffers than often assumed. We suggest that buffers employed in standard practices (e.g., at 50 mM or higher concentrations recommended by regulatory guidelines) are expected to significantly catalyze many hydrolysis reactions by acting as nucleophiles or bases. Finally, we recommend strategies to successfully measure hydrolysis rates for more accurate predictions of contaminant transformation in environmental systems.