Evaluating the Effect of Chemical Digestion Treatments on Polystyrene Microplastics: Recommended Updates to Chemical Digestion Protocols

Establishing the toxicity and exposure consequences of microplastics (MPs) on marine organisms relies on the nondestructive isolation of plastics from biological matrices. MPs are commonly extracted from these matrices by chemical digestion using alkali (e.g., potassium hydroxide (KOH) and sodium hydroxide (NaOH)), oxidative (e.g., hydrogen peroxide (H2O2)) and/or acidic (e.g., nitric acid (HNO3)) reagents. Although these digestion conditions can be highly effective for MP extraction, they can also react with the plastics. This can attribute an inaccurate representation of plastic contamination by altering MP visual characteristics (size, shape, color), thereby impeding identification and potentially returning erroneous numbers of ingested particles. In this study, the degradative impacts are assessed of the routinely applied digestion reagents (i) KOH, (ii) NaOH, (iii) H2O2, and (iv)HNO3 on polystyrene (PS) based MPs sized between 200 μm and 5 mm. Degradation of the PS MPs is evaluated using FT-IR, gel permeation chromatography, NMR, photoluminescence spectroscopy, and microscopy. These studies reveal HNO3 to be the most destructive for PS MPs, while the alkali and oxidative reagents result in negligible changes in plastic properties. These results are recommended to be used as a guideline to update current protocols to ensure the nondestructive treatment of MPs

Comparing capability of scenario hazard identification methods by the PIC (Plant-People-Procedure Interaction Contribution) network metric

Comparing the results of hazard identification (HAZID) methods is a complex task, but the question that drives this activity is vitally important: which HAZID method should be used to best identify an accident scenario? Despite many efforts to address this, effective metrics do not yet readily exist for clearly comparing HAZID results for a particular scenario. The complexity of socio-technical systems is often cited as a key factor that limits effective scenario identification, calling into question traditional HAZID efforts. Motivated by the observation that interactions between multiple component types, such as People, Plant and Procedures (P3), often significantly contribute to major process system accidents, being an expression of the complexity of the system, a novel, precise, network topology-based metric for calculating the contribution of P3 Interactions to accident scenarios is presented. This metric, called the P3 Interaction Contribution (PIC), is intended to be used for comparing the HAZID results. An illustrative example of using the PIC for HAZID comparison is included, whereby Failure Mode and Effects Analysis (FMEA), Blended Hazard Identification methodology (BLHAZID) and Systems Theoretic Process Analysis (STPA) were each applied to a heat exchanger start-up operation. The results show initial promise that the PIC can be effective as a HAZID comparison tool. The main outputs of this paper are the presentation of the PIC calculation process and the method for applying the PIC to HAZID results. The paper concludes with recommendations for further experimental work to explore the validation and assess the true value of the PIC