Unraveling the Marine Microplastic Cycle: The First Simultaneous Data Set for Air, Sea Surface Microlayer, and Underlying Water

Abstract

Microplastics (MP) including tire wear particles (TWP) are ubiquitous. However, their mass loads, transport, and vertical behavior in water bodies and overlying air are never studied simultaneously before. Particularly, the sea surface microlayer (SML), a ubiquitous, predominantly organic, and gelatinous film (<1 mm), is interesting since it may favor MP enrichment. In this study, a remote-controlled research catamaran simultaneously sampled air, SML, and underlying water (ULW) in Swedish fjords of variable anthropogenic impacts (urban, industrial, and rural) to fill these knowledge gaps in the marineatmospheric MP cycle. Polymer clusters and TWP were identified and quantified with pyrolysis-gas chromatography−mass spectrometry. Air samples contained clusters of polyethylene terephthalate, polycarbonate, and polystyrene (max 50 ng MP m −3 ). In water samples (max. 10.8 μg MP L −1 ), mainly TWP and clusters of poly(methyl methacrylate) and polyethylene terephthalate occurred. Here, TWP prevailed in the SML, while the poly(methyl methacrylate) cluster dominated the ULW. However, no general MP enrichment was observed in the SML. Elevated anthropogenic influences in urban and industrial compared to the rural fjord areas were reflected by enhanced MP levels in these areas. Vertical MP movement behavior and distribution were not only linked to polymer characteristics but also to polymer sources and environmental conditions.

Exploring the Transport Path of Oceanic Microplastics in the Atmosphere

“…One important source of uncertainty is related to the existence of the sea surface microlayer (the boundary interface between the atmosphere and ocean, 10 –3 to 1 mm thick), where MP particles can accumulate in higher concentrations with respect to the underlying water . The enrichment factor in this layer is still not well-defined, and it has been observed to be variable, with values ranging from twice, up to hundreds of times the concentration in the underlying water. − This can potentially explain a large part of the difference we detected between the model and the observations. Collecting information at the sea surface in this size range is still particularly challenging; however, conducting more observational campaigns targeting MP in the nano and microscale, which also bears the most significant environmental and health impacts, , will be essential to properly constrain the presence of these particles in the marine and atmospheric environment.…”

“…One important source of uncertainty is related to the existence of the sea surface microlayer (the boundary interface between the atmosphere and ocean, 10 −3 to 1 mm thick), where MP particles can accumulate in higher concentrations with respect to the underlying water. 60 The enrichment factor in this layer is still not well-defined, and it has been observed to be variable, with values ranging from twice, up to hundreds of times the concentration in the underlying water. 61−63 This can potentially explain a large part of the difference we detected between the model and the observations.…”

Quantification and Characterization of Fine Plastic Particles as Considerable Components in Atmospheric Fine Particles

“…MNPs in the marine environment can be transferred from the sea to the atmosphere via bubble bursting. , With 2.7–7.2 million metric tons of plastic released into the ocean annually in the coastal countries of the Western Pacific, the ocean may become a significant source of FPPs to the atmosphere of coastal urban areas, such as Shanghai (Supplementary Note 6). The findings suggest that the transport of FPPs from the ocean , could be a constant process, while FPPs in high-pollution episodes are often closely related to the production location and to human activities.…”