Plastic in the air?! - Spider webs as spatial and temporal mirror for microplastics including tire wear particles in urban air.

Studies concerning quantities of microplastics (MP) including tire wear particles (TWP) contamination in air samples are scarce. Spider webs have been suggested as a cheap and easily accessible biomonitor particularly for inorganic contaminates. Here, we emphasize the potential of spider webs to gain insights in the spatial and temporal trends of MP in urban air. The samples, collected in a mid-sized German city, were processed with Fentons reagent and measured using pyrolysis-gas chromatography-mass spectrometry for specific, polymer related indicator compounds. All samples contained TWP and other MP. The latter are detected and quantified as pyrolysis products of a polymer backbone. The results were expressed as clusters (prefix "C"). Determined polymer contaminations ranged from 11.4 μg/mg to 108 μg/mg spider web sample. The dominant polymer was C-PET (Ø 36.0% of total MP) derived most likely from textile fibers. Additionally, there was evidence for traffic-related contaminations. In particular car tire tread (Ø 40.8% of total MP) and C-PVC (Ø 12.0% of total MP) were found, with the latter presumably originating from paint used for road markings. Truck tire tread, C-PE, C-PP, C-PS, C-PMMA, and C-PC were also frequently found, but in much lower abundance (Ø <6.4% of total MP). Differences in contamination levels could be plausibly related to the sampling locations.