Qualitative analysis on contaminants of emerging concern in Swedish landfill leachates: a snapshot of occurrence and spatio-temporal variability.

Landfill leachate is a complex and understudied matrix increasingly recognized as a source of contaminants of emerging concern (CECs) to the environment. This study provides a snapshot of the occurrence of CECs in Swedish landfill leachates, investigating their spatial distribution across five landfills, and their temporal pattern over a one-year period at one site. To our knowledge, this is the first study using qualitative non-target and suspect screening to characterize the spatio-temporal profile of CECs in landfill leachate. In total, 79 CECs were identified, including industrial chemicals (ICs), pharmaceuticals and personal care products (PPCPs), per- and polyfluoroalkyl substances (PFASs), pesticides, stimulants, and sweetener. Several compounds, such as triisopropyl phosphate, 1,3-diphenylguanidine, and 1,3-di-o-tolylguanidine, were reported for the first time in landfill leachate. Spatial analysis revealed a consistent presence of CECs across all sites, with 34 compounds detected in both untreated and treated leachates, indicating limited removal efficiency of existing treatment systems. Temporal monitoring at one landfill showed moderate variation, with the highest number of CECs detected in the winter samples. Persistent detection of ICs, PFASs, and pesticides at all sampling time points suggests continuous leaching and highlights the limitations of current treatment approaches. This study offers important insights into the chemical composition of Swedish landfill leachate and underscores the need for improved monitoring and treatment strategies to mitigate environmental risks associated with CECs.