Influence of microplastics on small-scale soil surface roughness and implications for wind transport of microplastic particles.

Microplastics are an anthropogenic contaminant widely recognized for their effect on marine and freshwater systems, but their terrestrial effects remain less well studied. The inclusion of microplastics in soils has the potential to affect a range of different soil properties, including bulk density, hydraulic conductivity and aggregation. Soil properties affect the susceptibility of soils to wind erosion, and it is therefore likely that where the quantity of microplastics present in soils is sufficient to change soil properties, it may also change the response of soils to wind erosion. This paper quantifies whether the presence of microplastics in sediments affects the development of small-scale soil surface roughness (SSR) properties during wind erosion, and whether there are any relationships between indices of SSR and microplastic flux due to wind erosion. Two contrasting substrates (well-sorted sand and poorly sorted soil) and two types of microplastic (polyethylene beads and polyester fibres) are used. SSR is quantified using geostatistically derived indicators calculated from high-resolution laser scans of the soil surface with and without microplastics, and before and after wind erosion simulated using a wind tunnel. Our results reveal the relative size of the microplastic to the mineral sediment is key to controlling microplastic flux.This article is part of the Theo Murphy meeting issue 'Sedimentology of plastics: state of the art and future directions'.