Influence of microplastic colour on photodegradation of sorbed contaminants

Microplastics are ubiquitous in the environment, accumulate hydrophobic organic contaminants, and suppress the photodegradative loss of these contaminants. Thus, they have the potential to act as vectors for contaminant uptake by organisms and transport to remote regions. Our current understanding of microplastic-sorbed contaminant photodegradation is drawn from experiments with unpigmented microplastics, but the interaction of pigments with light may alter the loss and corresponding persistence of sorbed contaminants. To improve our ability to predict the fate of contaminants sorbed to the broad spectrum of coloured microplastics in the environment, therefore, we investigated the photodegradation (UVA light, λ_max = 350 nm) of the model organic contaminant anthracene sorbed to four coloured polyethylene microplastics. Anthracene loss kinetics were colour dependent (unpigmented ≫ orange > blue = white), which we attribute to differences in the pigment light absorption profiles for the different microplastics. The findings presented here highlight the need to consider the influence of microplastic pigmentation when evaluating the potential environmental impacts of their associated contaminants.