Beyond legacy pollutants: glacier and snow melt as a relevant source for current-use pesticides in Alpine environments under climate pressure.

Persistent organic pollutants (POPs), such as DDT and PCBs, accumulate in glaciers through long-range atmospheric transport (LRAT) and are re-released during melting. However, the potential for current-use pesticides (CUPs) to exhibit similar behaviour remains less understood. In this study, we employed (i) time-integrative passive sampling of meltwater streams across seven consecutive intervals (July-October 2024), (ii) spatially resolved surface sediments, and (iii) a dated sediment core (covering the period from ∼1970 to present), to investigate the occurrence and re-emission processes of CUPs in Alpine aquatic environments, alongside selected POPs as control substances. By comparing a glaciated catchment with a nearby catchment with minimal glacier cover in the Bernese Alps, Switzerland, 13 CUPs and their transformation products (TPs) were detected in the meltwater creeks. Several compounds were identified for the first time in this area, including fungicides (fluopicolide, and metalaxyl), herbicides (clomazone, and propyzamide), and transformation products (desethylterbuthylazine, and terbuthylazine-2-hydroxy). Time-weighted average water concentrations ranged from 2 to 860 pg/L, with peak concentrations occurring in early July and decreasing throughout the melt season, pinpointing specific compounds in each catchment. In addition, the sediment core reconstructions revealed that ΣDDT and ΣPCBs in sediments followed the anticipated trends of the mid-20th century but showed a significant increase starting in the 2000s, coinciding with accelerated glacier retreat. Surface sediments suggest a preferential association with silt and clay fractions, and projections of sediment-bound contaminants indicate potential inputs of up to 3.6 g ΣDDT, 2.2 g ΣPCBs, and 2.9 g CUPs over the next decade. Overall, our findings enhance the understanding of how catchment development influences post-depositional processes and highlight the role of snow and glacier melt as a persistent, continuous secondary source of contaminants to otherwise pristine ecosystems.