Unraveling key drivers of antibiotic fate and ecological risk in ice-covered lakes through multi-compartment analysis

Although ice-covered lakes account for over half of the world's lakes, they have received <2 % of the total research attention in freshwater system literature. Particularly, the fate, transport, and key drivers of antibiotics across multiple environmental compartments in these systems remain poorly understood. To address this critical knowledge gap, we investigated the transport pathways and key environmental drivers influencing antibiotic behavior in cold-region lake ecosystems. By quantifying distribution coefficients and integrating the physicochemical properties of antibiotics with seasonal variables, we applied statistical methods and data-driven models to identify the key drivers governing the multi-compartment partitioning of antibiotics across the ice column (ice water and ice suspended particles), water column (bulk water and water suspended particles), and sediment column (pore water and sediment particles). Our findings reveal that antibiotics exhibit distinct multi-compartmental patterns during the freezing period: (1) In the liquid phase, concentrations in pore water are approximately 36 and 54 times higher than in ice water and bulk water, respectively, while in the solid phase, antibiotics are predominantly associated with suspended particles, with concentrations about 25 times greater than those in sediment particles. (2) Distribution within the sediment column is primarily governed by the antibiotics' physicochemical properties, whereas partitioning within the ice-water column is mainly driven by freeze-thaw dynamics (30.27 %) and terrestrial inputs (21.35 %). (3) Low temperature can alter the adsorption capacity of organic carbon for antibiotics. Notably, ecological risks intensify during thawing, with risk levels increasing by 62.14 % compared with the ice-covered period. This study advances our understanding of antibiotic behavior across multi-compartments and seasonal transitions, contributing valuable insights into the environmental dynamics of antibiotics in ice-covered lake ecosystems.