Short-Term Effects of Commercial Fire Retardants on Water Quality Parameters: A Laboratory-Scale Study

This study evaluates the short-term effects of nine commercially available fire retardants (FRs) on water quality under controlled laboratory conditions. FRs were diluted to a 1:10 FR:water stock solution to approximate readily water-extractable fractions, and ion solubility was quantified together with key physicochemical parameters, including pH, electrical conductivity (EC), and dissolved oxygen (DO). Results revealed substantial heterogeneity among formulations in the concentrations of solubilized ions. Notably, FR4 (NP+) exhibited exceptionally high concentrations of NH4+, NO3−, NO2−, PO43−, and Br−, as well as elevated Ca2+ and Na+. Other formulations also released considerable loads of common nutrients, particularly NO3− and PO43−, although at lower magnitudes. Despite the pronounced ionic enrichment, pH and DO remained relatively stable across most treatments. However, DO decreased in several cases at higher FR concentrations, suggesting increased oxygen demand associated with dissolved constituents. EC displayed strong, concentration-dependent increases across treatments, reflecting the rapid dissolution of ionic components in water. Cluster analysis identified three distinct groups of FRs based on their water-quality responses. The PCA biplot further revealed two main gradients structuring the formulations: mineralization and compositional diversity (PC1), and physicochemical solution conditions (PC2), which together distinguish the chemical and physicochemical signatures of the tested products. Overall, the results highlight substantial formulation-specific differences in nutrient and metal release, with potential short-term implications for aquatic chemistry and ecosystem functioning. Although derived from controlled laboratory conditions, these findings provide a first-order assessment of FR impacts on water quality and underscore the importance of considering formulation composition in watershed risk assessments and post-fire water quality management strategies.