Community engagement and screening of 447 pesticides in the Gellibrand River catchment, Victoria, Australia

The study presents a comprehensive water quality data collection along the Gellibrand River catchment, over three monitoring campaigns conducted in 2024, to investigate pesticides occurrence. Citizen scientists, guided by the Royal Melbourne Institute of Technology (RMIT) University and the European Commission Joint Research Centre (JRC), deployed and retrieved passive samplers (n = 10), collected grab composite samples (n = 10) and conducted Stir Bar Sorptive Extraction (SBSE) of the latter, while Solid Phase Extraction (SPE) of all the other samplers was performed by a PhD student. All samples were screened by Gas Chromatography Quadruple Time of Flight High Resolution Mass Spectrometry (GC-QToF-HRMS) for 447 pesticides. Passive samplers provided qualitative information on the presence/absence of pesticides, while grab composite samples provided quantitative information in form of pesticides concentrations. Concentrations were used to calculate Toxic Units (TU) to assess potential ecological risks for crustaceans Daphnia magna . A total of 18 different pesticides were detected in the first campaign, followed by 8 in the second, and 15 in the third campaign. The two different extraction methods deployed, SPE and SBSE, revealed different compounds. Across the campaigns, fungicides emerged as the most frequently detected class, although most screened chemicals were insecticides. Temporal and spatial analyses highlighted significant variability in pesticide presence, influenced by factors like weather conditions and surrounding land use, in particular, forestry. The study’s ecological risk assessment identified potential toxicity risks to Daphnia magna from specific insecticides, such as carbaryl. The study successfully combined advanced sampling and extraction technologies with citizens participation, finding pesticides that are registered for and applied in surrounding forestry activities, providing valuable new insights regarding pesticides occurrence in Australia. Citizen scientists have been enthusiastically engaged in the collection, deployment, retrieval and extraction of samples. They contributed to communication and sharing of the results with the broader community, thus confirming the potential of citizen science to expand water quality monitoring capacity.