From watershed to lagoon: Occurrence and ecological risk of paracetamol in the Segara Anakan coastal ecosystem.

Pharmaceutical contamination in tropical coastal lagoons remains poorly characterized despite increasing anthropogenic pressures from watershed development. This study investigated the occurrence, spatial distribution, and ecological risk of paracetamol (acetaminophen) in the Segara Anakan Lagoon, Indonesia, a semi-enclosed tropical coastal ecosystem receiving substantial watershed inputs. Surface water samples were collected from 17 stations spanning West to East Plawangan during August 2023 and analyzed using solid-phase extraction (SPE) coupled with liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-Q-TOF/MS). Paracetamol was ubiquitously detected in all water samples at concentrations ranging from 5.11 to 886.44 ng L⁻1, with the highest levels observed near urban discharge points. Sediment samples showed paracetamol concentrations between 23.16 and 45.55 ng kg⁻1. Method validation demonstrated excellent analytical performance (recovery: 90.08-112.87%, method detection limit: 0.11 ng mL⁻1, linearity: R2 = 0.9962). Ecological risk assessment using the risk quotient (RQ) approach revealed low to high risk across trophic levels: algae (RQ = 0.04-6.62), invertebrates (RQ = 0.17-29.45), and fish (RQ = 0.03-5.54). Stations 5 and 16 exhibited high ecological risk (RQ > 1) for all three trophic groups, indicating potential adverse effects on aquatic biota. These findings provide the first comprehensive baseline data on pharmaceutical pollution in Indonesian tropical lagoon systems and underscore the urgent need for improved wastewater management strategies in coastal watersheds to protect these ecologically and economically important ecosystems.