Appraisal of the Temporospatial Migration and Potential Ecotoxicity of Phthalic Acid Esters in Municipal Effluents, Rivers and Dam—A Catchment-Wide Assessment

Abstract

Herein, the catchment-wide temporal dynamics and potential ecotoxicological risk of phthalic acid esters (PAEs) in aquatic ecosystems were assessed. Specifically, water samples were collected for a period of six consecutive months from seven selected sites, i.e., covering both dry and wet seasons for seasonal variabilities. The appraised PAEs comprised dimethyl phthalate (DMP), diethyl phthalate (DEP), di-n-butyl phthalate (DBP), benzylbutyl phthalate (BBP), diphenyl phthalate (DPP), di-n-hexyl phthalate (DHP), bis(2-ethylhexyl) phthalate (DEHP), di-n-octyl phthalate (DOP), diisodecyl phthalate (DiDP) and diisononyl phthalate (DiNP)) in municipal wastewater effluents, rivers and dam. Their concentrations were quantified using a gas chromatography–flame ionisation detector (GC–FID) via the liquid–liquid extraction mode. The appraised PAEs were ubiquitous in the selected sampling points, with DBP being the most abundant PAE homologue throughout the assessed localities. In particular, quantifiable concentrations were 18.9, 37.9 and 11.5 μg/L for DBP in wastewater effluents, rivers and the dam catchment, respectively, and for overall Σ10PAEs of minimum, mean and maximum of 0.492, 3.6 ± 9.82 and 63.2 μg/L, respectively. In addition, PAE concentrations in the effluents, rivers, and dam samples showed no significant differences with p < 0.05. The overall prominent sequence for ∑PAEs registered: 53.3 > 10.1 > 10.0 > 9.8 > 4.3 > 2.5 > 1.8 > 1.7 > 1.1 > 0.9% for DBP > DEHP > DiDP > DOP > DHP > DPP > BBP > DMP > DEP > DiNP, respectively. The ecotoxicological risk assessment (risk quotient method) showed that DBP and DiDP posed high risk (RQ ≥ 1), and DOP, DEHP, DHP, DiNP and BBP posed median risk to aquatic organisms (0.1 ≤ RQ < 1), while the risk from DMP and DEP was minimal (RQ < 0.1). Additionally, DBP, DEHP, DOP, DPP and DiDP were higher than the water criterion (3 μg/L) of PAEs recommended by the United States Environmental Protection Agency (USEPA) for the protection of aquatic life. Findings from this study should go a long way in guiding regulators, custodians and catchment management forums, along with interested and affected parties, regarding the status and potential ecotoxicological effects of PAEs in the receiving environment.