Primary microplastics can be the result of leakage from production facilities and accidental losses of plastic pellets during transport (Karlsson et al. 2018) while secondary microplastics, produced when larger pieces of plastic break up or fragment, are found, for example, in leachates from landfill sites, biosludge from wastewater treatment plants, and agricultural run-off (Mason et al. 2016; Mahon et al. 2017; Li et al. 2018; Cowger et al. 2019; He et al. 2019; Sun et al. 2019). Agricultural soils are now known to be sinks for microplastics as a result of intentional application of microplastic-coated seeds, chemicals and fertilizers (using new delivery technologies) intentional application of sewage sludge and effluents, plastic-coated seeds, chemicals and fertilizers (Nizzetto et al. 2016a; Nizzetto et al. 2016b; Piehl et al. 2018; Accinnelli et al. 2019; Corradini et al. 2019; Wang et al. 2019a; Wang et al. 2019b).
From collection: From Pollution to Solution: A Global Assessment of Marine Litter and Plastic Pollution