Biochemodynamic Features of Metal Ions Bound by Micro- and Nano-Plastics in Aquatic Media

Abstract

A simple model, based on spherical geometry, is applied to the description of release kinetics of metal species from nano- and micro-plastic particles. Compiled literature data show that the effective diffusion coefficients, Deff, for metal species within plastic polymer bodies are many orders of magnitude lower than those applicable for metal ions in bulk aqueous media. Consequently, diffusion of metal ions in the aqueous medium is much faster than that within the body of the plastic particle. So long as the rate of dissociation of any inner-sphere metal complexes is greater than the rate of diffusion within the particle body, the latter process is the limiting step in the overall release kinetics of metal species that are sorbed within the body of the plastic particle. Metal ions that are sorbed at the very particle/medium interface and/or associated with surface-sorbed ligands do not need to traverse the particle body and thus in the diffusion-limiting case, their rate of release will correspond to the rate of diffusion in the aqueous medium. Irrespective of the intraparticulate metal speciation, for a given diffusion coefficient, the proportion of metal species released from plastic particles within a given time frame increases dramatically as the size of the particle decreases. The ensuing consequences for the chemodynamics and bioavailability of metal species associated with plastic micro- and nano-particles in aquatic systems are discussed and illustrated with practical examples.

Polyvinyl chloride in consumer and environmental plastics, with a particular focus on metal-based additives

“…27 However, release is more likely from environmental PVC that has weathered and become micronised and that is exposed to physico-chemical conditions favouring the dissolution of inorganic compounds. 28,50,51 The inadvertent ingestion and digestion of microplastics by aquatic organisms and birds provides a means by which these conditions are met, and examinations of the gastro-intestinal tracts of bivalves 42,[52][53][54][55][56] have conrmed that PVC particles are oen present. As part of previous research, selected consumer and environmental samples reported in the current paper were micronised (mm-sized) to study the release of metals from PVC (and other plastics) in simulated digestive uids.…”

Spatially resolved indiffusion behavior of Cu2+ and Ni2+ in polypropylene

“…Previous studies revealed that diffusion behavior of polymers is influenced by several factors for example, polymer morphology, polymer density, molecular weight distribution, crystallinity, glass transition temperature, or polymer melting temperature. [27,28,[32][33][34] Here, we used an imaging mass spectrometry based method as a tool to analyze chemical metal ion diffusion in polymers. [35] Therefore a cryo-approach was established successfully to stop the diffusion process for the subsequent analysis.…”

A Detailed Review Study on Potential Effects of Microplastics and Additives of Concern on Human Health

“…Though polymers were considered to be inert towards metals in the past [97], great attention has recently been paid to better understanding the interaction between heavy metals and microplastics [98][99][100][101][102][103][104][105][106][107][108].…”