Microplastics in agricultural drainage water: A link between terrestrial and aquatic microplastic pollution.

Microplastic (MP) contamination has been reported to be higher in terrestrial compared to aquatic environments. This is probably due to the fact that plastic items are mostly produced and used in terrestrial environments and have a longer residence time. However, there are several links between the terrestrial and aquatic environments. We analyzed drainage water samples from agricultural soils in the Seeland, a heavily drained agriculturally intensive area in Switzerland for its MP (>100 µm) concentration and composition. We found MP in relevant numbers (mean 10.5 ± 9.5 N L-1). The polymers were mainly PA and PE, and the size distribution showed an exponential increase with decreasing particle size. The results show considerable MP concentrations in drainage water and imply a transport of MP in soils down to the drainage pipes. Given the large areas drained both in Switzerland and globally, it is proposed that MP leaching from soil can be a significant source of MP to aquatic ecosystems. Such a contribution should be considered when dealing with MP cycling on a local to global scale.

How small is the big problem? Small microplastics <300 µm abundant in marine surface waters of the Great Barrier Reef Marine Park.

Particle size plays an important role in determining the behaviour, fate and effects of microplastics (MPs), yet little is known about MPs <300 µm in aquatic environments. Therefore, we performed the first assessment of MPs in marine surface waters around the Whitsunday Islands region of the Great Barrier Reef Marine Park, Australia, to test for the presence of small MPs (50-300 µm) in-situ. Using a modified manta net, we demonstrate that MPs were present in all marine surface water samples, with a mean sea surface concentration of 0.23 ± 0.03 particles m-3. Microplastics were mainly blue, clear and black fibres and fragments, consisting of polyethylene terephthalate, high-density polyethylene and polypropylene plastic polymers. Tourism and marine recreation were considered the major contributing sources of MPs to surface waters around the Whitsunday Islands. Between 10 and 124 times the number of MPs exist in the 50 µm-300 µm size class, compared with the 1 mm-5 mm size range. This finding indicates that the global abundance of small MPs in marine surface waters is grossly underestimated and warrants further investigation. Research into the occurrence, characteristics and environmental fate of MPs <300 µm is needed to improve our understanding of the cumulative threats facing valuable ecosystems due to this smaller, potentially more hazardous size class.