Macroplastic surface characteristics change during wind abrasion

Mechanical abrasion is an important wind driven process which can degrade plastic litter on sandy beaches, desert environments and in agricultural settings. Wind-driven particle impacts can cause surface roughening and chemical changes and eventually complete fragmentation in high stress environments. Aeolian abrasion has been considered in the context of microplastics (< 5 mm) which can be easily mobilised by wind. However, macroplastic (> 5 mm) abrasion has primarily been confined to engineering studies using high air velocities (> 25 m s^-1) and large abraders (> 6 mm) which generate greater impact forces than observed in the natural environment. Using laboratory abrasion experiments, we demonstrate that the surface microtextures and surface chemistry of three different types of plastic are substantially altered during the processes of aeolian abrasion at impact particle velocities of 0.6 m s^-1. After ten days of continuous abrasion with four different erodents the macroplastic surfaces developed textures resulting from micro-cutting, denting, flaking, micro-pitting and surface flattening. The prevalence of each surface texture was dependent upon the angularity of the erodent and the type of plastic. In all cases, polymer surface chemical compositions became more complex due to embedding of shattered abrasive and the replacment of carbon with oxygen and silica.