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Micro and nano plastics in the marine-atmospheric environment

Illustrasjonsfoto: Colourbox

Studies have shown that marine air, snow, sea spray and fog contain or convey atmospheric microplastics. In a new study, 33 international experts highlight the importance of including the atmosphere into the total plastic cycle and form a strategy to manage plastic pollution.

The marine environment extends over 70% of our planet. It forms a significant surface where atmospheric micro and nano plastic (MnP) are exchanged between the air and water environments.

Research on the marine plastic cycle has primarily focused on terrestrial discharges of plastic to the sea, without considering atmospheric influence. It has become clear today that the atmosphere is an important component of the plastic cycle, a potentially significant source of smaller plastic particles that are transported to and from the oceans.

Dr. Nikolaos Evangeliou and Dr. Sabine Eckhardt at NILU have been focusing on modelling long-range atmospheric transport of microplastics released from road dust, as well as quantifying the global sources of atmospheric microplastics and microfibers.

Figure 1: Atmospheric micro and nano plastics transport, potential annual flux, burdens and current knowledge gaps.

Microplastics travel 1000s of kilometres

Atmospheric MnPs are small in size, predominantly below 500 microns. A large proportion of the particles are at or below 10µm, the respirable particle size. These particles fall within the particle size of greatest concern for biotic, ecosystem and human health. Thus, quantifying how much of these small MnPs the atmosphere provides to the ocean and the ocean-atmosphere exchange is important to global health.

The recent Nature Reviews Earth and Environment paper “Plastic Pollution in the Arctic” highlights the extent of the plastic pollution problem, illustrating its pervasiveness even into the remote Arctic environments. In the last few years, studies have shown marine air containing atmospheric microplastics, Arctic snow composed by atmospheric microplastics, and sea spray and fog conveying atmospheric microplastics. Notable concentrations of atmospheric microplastic and nanoplastic have been quantified, from 0.06-1.37 MnP m-3 in offshore marine air to 5700 m-3 in dense city environments, and modelled to travel by air 100s to 1000s of kilometres – across countries, continents and oceans.

Estimating the ocean-atmosphere exchange

This new perspectives paper Microplastics and nanoplastics in the marine-atmosphere environment brings together 33 international expert scientists in atmospheric, oceanography and plastic pollution, supported by the UN GESAMP and the WMO, to highlight the importance of  the atmosphere in the total plastic cycle, as air transports small plastic particles to great distances potentially to and from the marine environment.

The global ocean presents a significant expanse where atmospheric MnPs may deposit. Conversely, bubble burst ejection of MnPs, an exchange mechanism similar to sea salt aerosol marine-atmosphere exchange, suggests the sea to be a potential source of atmospheric MnP. The ocean-atmosphere exchange or flux is estimated in this new perspective paper (0.013–25 million metric tons per year), but these values are highly uncertain due to the limited availability of consistent, comparable data.

Strategy to help manage plastic pollution

To combat this uncertainty and to advance global ocean-atmosphere MnP fluxes, the scientists behind the paper outline a global observation and research strategy. This strategy will provide not only a long-term observation network of atmospheric MnP, but also help quantify the ocean-atmosphere MnP fluxes. The perspective paper highlights the current ‘unknowns’ in atmospheric MnP science, such as offshore marine deposition or source specific MnP emission rates, and presents solutions to address these knowledge and data gaps moving forward.

The global strategy described in the paper aims to help create a cohesive, comparable dataset that will enable us to monitor atmospheric MnP fluxes in a similar manner to mercury, aerosol particles or CO2. It will enable not only quantification of ocean-atmosphere MnP fluxes and therefore the influence of ecosystem and human health, but also more effective prevention and/or management of plastic pollution.

The perspectives paper highlights the need to act now to initiate a global MnP observation network, operation procedures and globally comparable long-term observation datasets.

Mace Head observatory, Ireland
The Mace Head Observatory in Ireland is one example of a possible GAW observation site. Photo: Chris Lunder, NILU