Stir bar sorptive extraction TDU-GC-QToF-HRMS for screening 230 pesticides in waters surrounding banana plantations in Costa Rica through community engagement

"The Gems of Water" citizens' engagement activity united the Joint Research Centre (JRC) of the European Commission with the Costa Rican based NGO Coral Conservation to screen for pesticides in local rivers using wide-screening technology. Citizens used stir bar sorptive extraction to collect and extract samples from three rivers and two wells in the south Caribbean region of Costa Rica, an area known for export-based banana agriculture. The advanced wide-screening method provided by the JRC Water Laboratory enabled the assessment of 230 agrochemicals. While the JRC supplied the technical equipment and protocols, the pesticide screening to be investigated and the monitoring scheme were co-designed with Coral Conservation group members, a local NGO. The pilot study collected new data on pesticide occurrence and their toxicity in the local tropical environment, complementing on-going studies in the region. The study found 23 pesticides, the majority of which are fungicides registered for use in banana cultivation (azoxystrobin, difenoconazole, fluopyram, thiabendazole). Cumulative pesticide concentrations ranged from 5.3 ng/L in the upper catchment of the Estrella River (E-a) to 954.9 ng/L in the lower catchment of the Sixaola River (S-c), where the highest individual compound concentration was also recorded for fungicide azoxystrobin (425.0 ng/L). At the sampling sites along the Carbon River and in the lower catchment of the Sixaola River, compounds fenamiphos, fenpropathrin and azoxystrobin were the main responsible for the elevated toxic units (Toxic Units >0.01) for crustacean daphnia magna. Beyond highlighting the link between agrochemical occurrences in surface waters and surrounding land use, the citizens' engagement aspect promotes alternative water quality monitoring methods, raising awareness and scientific literacy in local communities and underscoring the value of bottom-up approaches.