Presence of microplastics in riparian sediments of the urban stretch of the Milagro River, Milagro Canton, Ecuador

Abstract

The objective of the study was to determine the presence, spatial distribution, and morphological characteristics of particles consistent with microplastics in riparian sediments along the urban stretch of the Milagro River, in the Milagro canton, Ecuador. A quantitative, descriptive, non-experimental, cross-sectional study was conducted. The study area covered approximately 48,000 m² between both banks, from San Miguel Bridge to Vasija de Barro. Five sampling zones were established: San Miguel Bridge, Parque de la Familia, Central Church Bridge, Valdez Bridge, and Vasija de Barro, with nine stations distributed along both banks. At each station, a 1 m² quadrant was delineated, and surface sediment was collected to a depth of 10 cm. The samples were processed using 5 mm and 0.5 mm stainless steel sieves. The recovered particles were counted, weighed, and visually classified by type and morphology through direct observation, a monocular magnifying glass, and an optical microscope. The analysis was descriptive, using frequencies, percentages, and mass per station. The total mass recovered was 103 g; 37.65 g corresponded to particles visually classified as primary and 65.28 g as secondary. A total of 594 particles were identified, with fragments predominating at 447 units, equivalent to 75.3 %. The highest accumulation was recorded in Zone 3, particularly at Station E6. The results indicate the presence of particles consistent with microplastics in the section studied; however, identification was based on visual and morphological characteristics, without instrumental polymeric confirmation, which limits the interpretive scope of the findings.