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There is a growing concern that nanoplastic pollution may pose planetary threats to human and ecosystem health. However, a quantitative and mechanistic understanding of nanoplastic release via nanoscale mechanical degradation of bulk plastics and its interplay with photoweathering remains elusive. We developed a lateral force microscope (LFM)-based nanoscratch method to investigate mechanisms of nanoscale abrasive wear of low-density polyethylene (LDPE) surfaces by a single sand particle (simulated by a 300 nm tip) under environmentally relevant load, sliding motion, and sand size. For virgin LDPE, we found plowing as the dominant wear mechanism (i.e., deformed material pushed around the perimeter of scratch). After UVA-weathering, the wear mechanism of LDPE distinctively shifted to cutting wear (i.e., deformed material detached and pushed to the end of scratch). The shift in the mechanism was quantitatively described by a new parameter, which can be incorporated into calculating the NP release rate. We determined a 10-fold higher wear rate due to UV weathering. We also observed an unexpected resistance to initiate wear for UV-aged LDPE, likely due to nanohardness increase induced by UV. For the first time, we report 0.4–4 × 10–3 μm3/μm sliding distance/μN applied load as an initial approximate nanoplastic release rate for LDPE. Our novel findings reveal nanoplastic release mechanisms in the environment, enabling physics-based prediction of the global environmental inventory of nanoplastics. 

Peracetic acid (PAA) is being considered as a disinfectant in membrane-based wastewater reuse systems, but its compatibility with polyamide membranes has not been thoroughly investigated. In this work, we showed that PAA induced much less change in the performance and material characteristics of NF90 membranes than the traditional disinfectant free chlorine (NaOCl). The change in membrane water flux and the rejection of salt and neutral organic compounds after PAA exposure (1–180 g h L −1 ) is significantly less than that resulting from NaOCl exposure at levels as low as 1 g h L −1 . The presence of two wastewater constituents, chloride or Fe( ii ), did not significantly impact membrane performance upon exposure to PAA. Surface characterization showed that oxygen was incorporated into polyamide by PAA, some of which was attributed to the formation of carboxylic acid groups. Experiments using a model aromatic amide, benzanilide, indicated an unexpected role of PAA in protecting the membrane from radicals formed by Fe( ii ) and the H 2 O 2 present in commercial PAA formulations. Furthermore, product identification suggests that both amide bond breakage and ring oxidation are possible reaction mechanisms for PAA. Our findings support that PAA is a viable disinfectant candidate for wastewater reuse and warrants further evaluation.