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Plastics have long been an environmental contaminant of concern as both large-scale plastic debris and as micro- and nano-plastics with demonstrated wide-scale ubiquity. Research in the past decade has focused on the potential toxicological risks posed by microplastics, as well as their unique fate and transport brought on by their colloidal nature. These efforts have been slowed by the lack of analytical techniques with sufficient sensitivity and selectivity to adequately detect and characterize these contaminants in environmental and biological matrices. To improve analytical analyses, microplastic tracers are developed with recognizable isotopic, metallic, or fluorescent signatures capable of being identified amidst a complex background. Here we describe the synthesis, characterization, and application of a novel synthetic copolymer nanoplastic based on polystyrene (PS) and poly(2-vinylpyridine) (P2VP) intercalated with gold, platinum or palladium nanoparticles that can be capped with different polymeric shells meant to mimic the intended microplastic. In this work, particles with PS and polymethylmethacrylate (PMMA) shells are used to examine the behavior of microplastic particles in estuarine sediment and coastal waters. The micro- and nanoplastic tracers, with sizes between 300 and 500 nm in diameter, were characterized using multiple physical, chemical, and colloidal analysis techniques. The metallic signatures of the tracers allow for quantification by both bulk and single-particle inductively-coupled plasma mass spectrometry (ICP-MS and spICP-MS, respectively). As a demonstration of environmental applicability, the tracers were equilibrated with sediment collected from Bellingham Bay, WA, United States to determine the degree to which microplastics bind and sink in an estuary based of grain size and organic carbon parameters. In these experiments, between 80 and 95% of particles were found to associate with the sediment, demonstrative of estuaries being a major anticipated sink for these contaminants. These materials show considerable promise in their versatility, potential for multiplexing, and utility in studying micro- and nano-plastic transport in real-world environments.

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Impinging liquid jets have been demonstrated to be an effective means of providing high heat transfer rates, and widely used in designing cooling systems for electronic modules, plastic manufacturing, and many other applications in the industry. It is very important to study the factors which govern the heat transfer rate in the liquid impingement on a heated surface to ensure cooling efficiency. The paper presents a numerical approach to study the convective heat transfer of circular liquid jet impingement on a heated surface where influencing factors like surface tension, gravity, viscosity, surface temperature etc. are considered. Finite volume method (FVM) with pressure based coupled solver implemented in commercial ANSYS Fluent CFD is used to solve Reynolds Averaged Navier Stokes equations. Free surface flow is modelled using Volume of Fluid (VOF) Method along with the compressive scheme and sharp interface modelling which accurately captures interfaces between immiscible fluids. The liquid film formation and the heat transfer phenomenon are examined in detail. The influence of jet velocity profiles on pressure distribution and heat transfer along the heated surface is presented. The results obtained from numerical solution are validated against experiment and previously published work with a close match.