La Pineda beach in Vila-seca (Tarragona) records the highest concentration of microplastics in Catalonia

There are no surprises. La Pineda beach in Vila-seca has, by far, the highest concentration of microplastics in Catalonia. This black spot on the Catalan coast was already well known to the Tecnatox research group at the Universitat Rovira i Virgili (URV), which for years has been studying the presence of microplastics in the environment and their effects on health. Now, however, they have analysed the 580 kilometres of the Catalan coast from Cap de Creus to Vinaròs and the data are clear: this beach has up to 2,000 microplastics per kilogram of sand, a figure that almost doubles that of the second beach on the list, one in Badia del Fangar in the Ebro delta, which has over 1,100.

"What surprised us was to see that the beaches of Barcelona, the most populous city in Catalonia, have a lower concentration of microplastics than other points further south such as between Castelldefels and Vilanova i la Geltrú or a large part of the coast of Tarragona," said Joaquim Rovira, a researcher at the URV's Department of Basic Medical Sciences. The study is the most exhaustive one to be carried out on the coast of Catalonia and analysed seventy samples from around fifty beaches, which provided a very accurate picture of the state of microplastics contamination along the coastline and identified the most affected areas.

The samples were collected from the intertidal fringe, which is the area of wet sand between the highest point reached by the waves and the water level. The microplastics found were classified according to their size and chemical composition; that is, those microplastics identifiable to the naked eye (up to 5 millimetres) were mainly polyethylene and polypropylene and were either industrial pellets or the result of the degradation of everyday objects such as plastic bottles. Smaller microplastics, measuring less than 0.5 millimetres, came from textile fibres made from polyester and polyamide, which are released into the environment through the process of washing clothing.

The most affected points

Much of the pollution on the beach at La Pineda, which took first place in the classification, was in the form of plastic pellets, mainly from the petrochemical industry, but the most alarming figure (more than 60%) represented the quantity of textile fibres found, mainly polyester. These owe their presence to the fact that they are not retained by washing machine filters and therefore reach the sea through wastewater. "Once they reach the coast, they ought to be dispersed into the sea, but the location of the underwater wastewater outlets between the Port of Tarragona and the cape of Salou prevents this from happening", Rovira clarified.

A significant concentration of microplastics was also found washed down the river at the mouth of the River Ebre, especially at the Badia del Fangar, with more than 1,100 units per kilogram. The Miracle and Arrabassada beaches in Tarragona also registered a high number of pollutants (more than 700 and more than 600, respectively), followed by the Cala Vallcarca beach, located between Castelldefels and Sitges. "We attribute this figure to the microplastics that reach the sea via the River Llobregat and which are carried along by the currents to the southern beaches" explained the researcher.

The type of sand plays a decisive role

The research has also shown how microplastics are distributed according to the characteristics of the sand. "On the beaches of the Costa Brava we found lower levels of microplastics. We attribute this to the fact that the sand is coarser and that it does not retain as many microplastics as fine sand beaches", says Nora Expósito, a researcher at the Department of Chemical Engineering, who also took part in the research

The research team pointed out that the results were to some extent to be expected due to the large volume of plastic production and because plastic does not easily biodegrade. "The misuse of plastics, the poor management of waste and uncontrolled dumping, etc., mean that the plastics break down, forming the micro and nanoplastics that we find everywhere", say Esther Marí and Jordi Sierra, who took part in the study. "We have found them in continental, marine, waste and drinking water, in soils and sediments, in molluscs and even in human waste. We can confidently say that plastics are probably the most abundant xenobiotic pollutants on Earth," they warn.

A faster and cheaper technique

One benefit to have come from study by the Tecnatox team is that they have demonstrated the viability of a technique that until now had never been used to collect microplastic samples. The technique was found to be reliable and cheaper and uses fluorescence microscopy to detect the microplastics. The technique irradiates the filters with a specific wavelength that causes the small plastic fragments to glow, thus making it faster and easier to detect them.

Once all the samples had been obtained, one subset was analysed using this new method and the other using the traditional system based on spectroscopy. On comparing the results, it was found that using fluorescence microscopy is a good initial method for identifying the most contaminated areas.