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  1. Understanding not only microplastic (MP) concentration but also size distribution, morphology, and polymer profiles is desirable for stormwater, which is an important pathway of entry for MP into the aquatic environment. A challenge is that subsampling is often required for analysis of environmental samples and the impact of subsampling on the stormwater MP concentration determined and the polymer types identified is poorly characterized. To address this, MP were extracted from urban and suburban stormwater, including from green infrastructure. Fourier Transform Infrared microscopy was performed to characterize MP. In addition, particle dimensions and morphology were recorded. Varying the number of 63–250 μm particles subsampled per sample demonstrated the coefficient of variation for concentration (standard deviation/mean) for most samples was <0.3 when 20 particles (0.8–15% of total particles) or <0.2 when 30 particles (1.2–24% of total particles) per sample were analyzed. MP concentrations in the 63–250 μm size class ranged from 15 to 303 MP/L, one to two orders of magnitude greater than observed in previously reported paired samples from the 250–500 or 500–2000 μm size classes. A total of 25 plastic polymer types were observed across samples, more than observed in the large size classes. Spectral signatures of surface oxidation indicative of weathering were observed on most polyethylene, polypropylene, and polystyrene particles, which were the most abundant polymer types. Fragments were the dominant morphology with an average maximum length of 158 ± 92 μm. Overall, these results may help inform subsampling methods and be useful in future exposure assessments for aquatic organisms or design of MP removal technologies for urban and suburban stormwater. 
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  2. Microplastics (MP) have been proposed as a vector for pathogenic microorganisms in the freshwater environment. The objectives of this study were (1) to compare the fecal indicator growth in biofilms on MP and material control microparticles incubated in different wastewater fractions and (2) to compare MP biofilm, natural microparticle biofilm, and planktonic cell susceptibility to disinfection by peracetic acid (PAA). Biofilms were grown on high‐density polyethylene, low‐density polyethylene, polypropylene MP or wood chips (as a material control) and incubated in either wastewater influent or pre‐disinfection secondary effluent. Reactors were disinfected with PAA, biofilms were dislodged, and fecal coliform and E. coli were cultivated. Fecal indicators were quantifiable in both MP and wood biofilms incubated in the wastewater influent but only on the wood biofilms incubated in secondary wastewater effluent. More fecal coliform grew in the wood biofilms than MP biofilms, and the biofilms grown on MP and woodchips were more resistant to disinfection than planktonic bacteria. Thus, it may be possible to refer to the disinfection literature for fecal indicators in biofilm on other particles to predict behavior on MP. Treatments that remove particles in general would help reduce the potential for fecal indicator bypass of disinfection. 
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