Impact of accelerated weathering on the leaching kinetics of stabiliser additives from microplastics

James H Bridson; Robert Abbel; Dawn A Smith; Grant L Northcott; Sally Gaw

doi:10.1016/j.jhazmat.2023.132303

Impact of accelerated weathering on the leaching kinetics of stabiliser additives from microplastics

J Hazard Mater. 2023 Oct 5:459:132303. doi: 10.1016/j.jhazmat.2023.132303. Epub 2023 Aug 14.

Authors

James H Bridson¹, Robert Abbel², Dawn A Smith², Grant L Northcott³, Sally Gaw⁴

Affiliations

¹ Scion, Titokorangi Drive, Private Bag 3020, Rotorua 3046, New Zealand; School of Physical and Chemical Sciences, University of Canterbury, Christchurch 8041, New Zealand. Electronic address: jamie.bridson@scionresearch.com.
² Scion, Titokorangi Drive, Private Bag 3020, Rotorua 3046, New Zealand.
³ Northcott Research Consultants Limited, 20 River Oaks Place, Hamilton 3200, New Zealand.
⁴ School of Physical and Chemical Sciences, University of Canterbury, Christchurch 8041, New Zealand.

PMID: 37595471
DOI: 10.1016/j.jhazmat.2023.132303

Abstract

The release of additives from microplastics is known to harm organisms. In the environment, microplastics are exposed to weathering processes which are suspected to influence additive leaching kinetics, the extent and mechanism of which remain poorly understood. We examined the impact of weathering on stabiliser additive leaching kinetics using environmentally relevant accelerated weathering and leaching procedures. Nine binary polymer-additive formulations were specifically prepared, weathered, analysed, and evaluated for their leaching characteristics. Cumulative additive release (Ce) varied widely between formulations, ranging from 0.009 to 1162 µg/g. Values of Ce generally increased by polymer type in the order polyethylene terephthalate < polyamide 6 < polyethylene. The change in leaching kinetics after accelerated weathering was incongruous across the nine formulations, with a significant change in Ce only observed for three out of nine formulations. Physicochemical characterisation of the microplastics demonstrated that additive blooming was the primary mechanism influencing the leaching response to weathering. These findings highlight the dependency of additive fate on the polymer type, additive chemistry, and the extent of weathering exposure. This has significant implications for risk assessment and mitigation, where the general assumption that polymer weathering increases additive leaching may be too simplistic.

Keywords: Artificial aging; Mass spectrometry; Plastic additives; Plastic pollution; Polymer degradation.