Amount, distribution and composition of large microplastics in typical agricultural soils in Northern Germany

Highlights: • Microplastics were found at all of the 15 North German farmland sites sampled. • Mean microplastics' abundance was 3.7 ± 11.9 MP particles per kg DW (median: 0.0, interquartile range: 0.0–4.9). • Composition of microplastics was uniform across the farmland sites sampled. • The most abundant particles were black films made of polyethylene. • Microplastic pollution decreased with soil depths despite regular ploughing. The pollution of the aquatic and terrestrial environment with plastics is a fast growing phenomenon with potential threats to the functioning of ecosystems and organisms therein as well as for human well-being. So far, research activities have mainly focused on the occurrence of microplastics (MP) in marine habitats, while little is known about their distribution and composition in the terrestrial environment. Agricultural practices such as fertilization, mulching or ensilage make agriculture a likely path for MP into the environment. Here, we collected soil samples at 15 farmland locations in Schleswig-Holstein, Northern Germany, to study the amount, distribution and composition of MP in the size range between 1 and 5 mm. In total, 379 MP were identified in a total of ~84 kg of dry weight (DW). Particle abundances in the sampling units ranged from 0 to 217.8 MP per kg DW with a mean abundance of 3.7 ± 11.9 MP per kg DW (median: 0.0, interquartile range: 0.0–4.9) per site. Although MP were found at all study sites, only 34% of the sampling units contained synthetic particles. Our data contribute to the establishment of a baseline on the amount, type and size of MP in farmland soils. Such a baseline is important for future monitoring schemes and for the development of more environmentally friendly management systems that reduce the input of MP into the agricultural system.