The impact of microplastic weathering on interactions with the soil environment: a review

Abstract. Recent studies have reported the influence of microplastic on soil quality parameters. Mass concentrations of plastic particles as found in highly contaminated soils were shown to weaken the soil structure by reducing the proportion of water stable aggregates (WSA). In addition, parts of the edaphon are adversely affected by mainly the < 100 µm microplastic fraction. The specific interaction of soil microplastic with other particulate organic matter (POM) and the mineral phase during the formation of soil aggregates as well as the adverse effects of especially the small-sized fraction, which has low weight but high specific surface area, justify a focus on surface properties of the soil microplastic and their alteration during the plastic life cycle. Exposed to UV radiation, juvenile plastic undergoes photochemical weathering with embrittlement and the formation of surface charge. When plastic particles enter the soil environment, a second step takes place, that includes biogeochemical weathering with enzymes, biotic and abiotic acids, oxidants as well as bioturbation and feeding of soil fauna. This work integrates recent findings on the effects of microplastic on soil structure and biota, the genesis of its surface characteristics and discusses how to reproduce them to conduct laboratory experiments with close-to-nature designer microplastic.