Inventarisatie aspecten rondom opruimen microplastics na maritieme incidenten

Samenvatting

The project Samenwerking Kustverontreiniging na Maritieme Incidenten (Cooperation Coastal Pollution after Maritime Incidents) explores how Rijkswaterstaat can better assist municipalities in cleaning up pollution that washes up on the coast after maritime incidents. In this context, an inventory has been made of methods that can be used to clean up the coastline from microplastics (particularly industrial pellets) that have ended up in the sea as a result of an incident. Broadly speaking, there are three methods used to remove microplastics, namely raking, shovelling or vacuuming, after which a sieve may or may not be used to separate materials. Shovelling or raking are suitable methods for removing plastics from soft sediments without vegetation, such as beaches and possibly tidal flats. On hard substrates, and on moist sand, the 'hoover' is an effective way to collect microplastics reasonably selectively, especially as long as the pellets are still on top of the sand. If the sand is dry, a combination with a sieving system is needed to separate the microplastics from the sand that is also collected. Vacuum cleaning can also be applied to overgrown areas, but as the overgrowth becomes denser, the efficiency with which microplastics are collected decreases. For the vacuum method to work effectively, it is also important to avoid vacuuming coarse (plant) material, as this can quickly clog the vacuum hose. All methods can be used on a small scale, manually, or on a large scale, motorised. Vacuum cleaning seems to be the most suitable method for cleaning up washed-up microplastics from the various substrates. There are a few companies that offer vacuum cleaning systems for the removal of microplastics on the market. These may or may not be equipped with systems that separate the waste, although separating microplastics and plant remains within a size fraction is not possible at present. It is inevitable that organisms will be damaged or removed during clean-up operations. However, if this takes place in a limited area, quick recovery from the surrounding terrain is possible, provided that the structure of the subsurface has not been changed by the clean-up operations. Therefore, vacuuming is preferable to excavating and mowing. To minimise the area that needs to be cleaned up, a fast response after an incident is important, as the plastic can then be cleared while still concentrated in the flood mark. Ideally, an affected beach should be closed to the public so that plastics do not end up deeper in the sand through foot traffic or vehicles. For salt marshes, it is important to act quickly if the plastics are still low on the marshes where the vegetation is less dense. Densely vegetated salt marshes (and silty tidal flats) are difficult to clean without substantial impact on the local system. Ideally, contamination of these areas is prevented by collecting the plastics from the water at an early stage, for example by using oil screens. If microplastics do end up in these areas, 'doing nothing' seems to be the best option, as the impact of the presence of plastic pellets on the ecosystem seems small. However, without specific research, this remains an assumption. It is possible that the ecological effects of pellets are too subtle to be observed under field conditions, but from an ethical and aesthetic point of view, lost waste should always be cleaned up as much as possible. For the further development of knowledge on how best to react after an incident with microplastics, the exchange of knowledge and experience in this field should be promoted within the Netherlands and possibly Europe. If various prototypes of clean-up systems can be tested in this context, a better picture of their actual effectiveness can be obtained. This cooperation may also provide the market perspective that can encourage commercial parties to invest in improving the clean-up methods.