Beach-cast algae management issues: application on field as fertiliser and associated risks of environmental pollution with microplastic and associated pollutants.

, Putna-Nimane Ieva, Vecmane Elina, Skutele Kristiana, Spilva Liene, Meskis Sandijs.

Plastics have become an essential part of our everyday life since the beginning of their mass production in the 1940s. With the increasing world population, the demand for plastic products is rising. As a result, the amount of plastics (and microplastics) that enter the surrounding environment including beach-cast algae is increasing. Beach-cast algae is often seen as just another waste item to be managed by removing it thus removing also nutrients and plastic/microplastic from seaside and sea, but it has also an important role in the beach ecosystem in coastline of Baltic Sea, e.g., helps alleviate the effects of beach erosion, many species depend on beach wrack as a source of food, living space and nursery. Meanwhile, it has significant potential as a remediation measure to improve coastal water quality (by removing nutrients, heavy metals etc.) and as a resource., e.g., fertiliser. In fact, in Latvia beach-cast algae application on fields as fertiliser is one of the historical methods in order to improve the quality of the soil. Actually, it is proved that algae in soil works as a biostimulant for plant seeds to develop, but recent research shows that plastic abundance in soil negatively impacts cell development of plant seeds and roots. The aim of this study is to try to access pros and cons of beach-cast algae application on fields as fertiliser in Latvia taking into account their content of: nutrients (TotN, P, K, S, TotC), microplastics and associated pollutants (e.g.,heavy metals, plastic leachates etc.). Results show first in sight of Latvia's beach-cast algae management raising problematics,especially, if they're used as fertilisers, as national legislation ommit microplastic pollution issue, but microplastic were found in all beach-cast algae samples, meanwhile concentrations of associated pollutants (heavy metals) did not show any correlation between microplastic amount.

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