Microplastics in Landfill Leachates in Three Nordic Countries

We investigated the occurrence of microplastics (size range 5,000-50 µm) in leachates at 11 landfills of different age and operational status in Finland, Iceland and Norway. Collective sampling was carried out by pumping leachate with a stainless-steel submergible pump through a custom-made, stainless-steel filter unit containing filter plates with decreasing pore sizes (5,000, 417 and 47 µm, respectively). Samples were pre-treated and split into particles size classes above 500 μm and above 50 μm, and screened for occurrence of microplastics made of PE, PP, PVC, PS, PET, PA, PU, PC, PMMA, POM, SBR (rubber) or PMB (polymer modified bitumen). Samples were analysed by FT-IR spectroscopy, both to identify and to count microplastic particles (SBR and PMB were merely identified). Most samples tested positive for multiple microplastics. Three leachates, including drinking water (blank), tested positive for SBR particles and/or PMB only. Treated leachate samples exhibited lower total microplastic’s counts than untreated, up to several orders of magnitude. National waste management practices over time, landfill age or operational status do not seem to explain differences in microplastic abundance or counts between leachates. Particle count and calculated loads of microplastic emissions through leachates differed several orders of magnitude between landfills. Results indicate that landfill leachates might be a relatively small source of microplastics (>50 µm) to surface waters compared to untreated and treated sewage or road runoff. Continued data acquisition, improved sample preparation and understanding of variability of microplastics in landfill leachate are necessary, including particles smaller than 50 µm.