Every year, seven tonnes of plastic waste are dumped on the Barcelona coastline
The concentration of floating microplastics on some beaches in Barcelona is very high, with values reaching 44 fragments per square metre, a magnitude higher than that found in areas with a high accumulation of marine litter, such as the South Pacific Gyre. Recently, the amount of microplastics and macroplastics leaving the Llobregat and Besòs rivers and the discharges of unitary systems (DSU) — the combined discharge points of sewage and stormwater along the coast — has been estimated at 40 billion particles per year. Most of this waste comes from the Llobregat river, which discharges some 28 billion particles per year (4.4 tonnes), followed by the Besòs river, with 11 billion particles (1.7 tonnes). The other 550 million particles (1.2 tonnes) come from the DSU.
The concentration of floating microplastics on some beaches in Barcelona is very high, with values reaching 44 fragments per square metre, a magnitude higher than that found in areas with a high accumulation of marine litter, such as the South Pacific Gyre. Recently, the amount of microplastics and macroplastics leaving the Llobregat and Besòs rivers and the discharges of unitary systems (DSU) — the combined discharge points of sewage and stormwater along the coast — has been estimated at 40 billion particles per year. Most of this waste comes from the Llobregat river, which discharges some 28 billion particles per year (4.4 tonnes), followed by the Besòs river, with 11 billion particles (1.7 tonnes). The other 550 million particles (1.2 tonnes) come from the DSU.
These are some of the conclusions of a study carried out by a team led by experts Anna Sanchez-Vidal, member of the Consolidated Research Group in Marine Geosciences at the Faculty of Earth Sciences of the University of Barcelona, and Jose Alsina Torrent, from the Maritime Engineering Laboratory of the Universitat Politècnica de Catalunya - BarcelonaTech (UPC).
Sampling campaigns on the coasts of Barcelona
The study is part of the project “Tools for better management of marine litter in coastal areas and accelerate the transition to a circular economy of plastic” (TRACE), funded by the Spanish Ministry of Science, Innovation and Universities and the State Research Agency (AEI) through the call for proposals for strategic projects aimed at the ecological transition and the digital transition. The TRACE project aims to develop floating litter prediction and monitoring tools to promote the conservation, sustainable use and management of coastal zones.
They have also taken samples at the mouth of the Llobregat and Besòs rivers and at the outlet of several DSUs.
The findings indicate that about 90% of the waste leaving DSUs and rivers returns to the coast within about 28 days. Currents and waves, as well as the orientation of the coast, determine the transport and accumulation of debris on the different beaches. It has also been observed that the amount of floating litter depends on the outflow: after heavy rainfall events, when the outflow is higher, the number of floating litter increases.
Regarding the types of plastics, the most frequent are fragments and transparent films, mostly composed of polyethylene and polypropylene. Other types of plastics with a clearly identifiable origin are wet wipes and artificial turf fibres, with 12 million entries per year.
A citizen science project
The pilot test included a citizen science initiative in which groups of volunteers sampled for microplastics on different beaches in Barcelona, both directly from the sand on the beach and by dragging a microplastic fishing net from paddle surfboards or kayaks. This sampling has been carried out in coordination with the Spanish delegation of Surfrider Foundation Europe.
The samples collected in this pilot test were analysed in the laboratories of the University of Barcelona, where the type of plastic, colour, and shape were established to determine their origin.
Based on the data obtained and the analysis of variables such as waves, currents and the type of beach, the UPC researchers have developed a numerical modelling tool that makes it possible to simulate the route of this waste from the river mouths and the points where water is discharged into the sea, as well as to determine the areas where the highest concentrations occur.
The results of the study were presented on 20 May at a conference at the UPC’s Campus Diagonal Nord.
Multimedia gallery
The team lead by Jose Alsina Torrent, from the Maritime Engineering Laboratory of the Universitat Politècnica de Catalunya - BarcelonaTech (UPC).
Currents and waves, as well as the orientation of the coast, determine the transport and accumulation of debris on the different beaches.
