Study of a stream in Argentina with a high concentration of microplastics: Preliminary analysis of the methodology

This study presents for the first time results about the microplastic concentration and their origin in a stream of the Pampas region in Argentina, receiving wastewater of an intermediate city. The most appropriate procedure to analyze and quantify the microplastics in the studied system is the use of an oxidative digestion process using a 30% H₂O₂ solution to eliminate the organic matter in the samples. A high quantity of MPs, on the order of millions of microplastics per m³ of water, was estimated in the Langueyú stream. 56% of the microplastics correspond to fibers with diameters between 10 and 15 μm and lengths less than 500 μm, while 44% are fragments with sizes of tens of micrometers. Raman microspectroscopy was used to identify the type of fibers. The characteristics of the microplastic fibers released in a wash load test are comparable with those observed in the Langueyú stream, in particular, the average sizes and the distribution of the diameters of the MPFs are similar. The processes in the sewage treatment plant, prior to their discharge in the stream, would affect the color of the fibers and their length.