Influência dos fatores socioespaciais na ocorrência de microplásticos no escoamento pluvial de Fortaleza (CE)

Abstract

Microplastics (MPs) are synthetic polymers ranging in size from 1 μm to 5 mm. Stormwater runoff has been recognized as one of the main transport routes for these pollutants. However, studies relating socio-spatial factors to the abundance and characteristics of MPs present in stormwater runoff are still incipient, especially in developing countries of the Global South. This research aims to evaluate the influence of socio-spatial factors, such as land use and population density, on the distribution and characteristics of microplastics present in stormwater runoff in different coastal areas of the city of Fortaleza (CE). The study area includes four neighborhoods: i) Praia do Futuro I, ii) Cais do Porto, iii) Meireles, and iv) Barra do Ceará. Land use and occupation maps for each area were created using QGIS software. Stormwater runoff samples were collected between January and March 2025 from four stormwater outfalls in each neighborhood. The samples were analyzed through sieving, digestion of organic matter, density separation, filtration, counting, visual identification, and polymer analysis of MPs. The results indicate differences in the intensity and pattern of activities in the four areas. The abundance of MPs differed significantly between areas (p < 0.05), with the highest median observed in Meireles (1,824 items/L) and Barra do Ceará (688 items/L), both characterized by higher population density. Lower abundances were recorded in less inhabited areas, such as Praia do Futuro I (118 items/L) and Cais do Porto (100 items/L). Fibers, rubbers, and fragments predominated, with polyethylene, polypropylene, and polyethylene terephthalate being the main polymers identified. Significant differences were observed in the composition of shapes, colors, and sizes of MPs between neighborhoods (p < 0.05). Population density and residential and mixed land uses explain 66% of the morphological variability of microplastics, with greater heterogeneity of MPs occurring in more densely populated neighborhoods and those with higher intensity of residential and mixed land use. This study concludes that socio-spatial variables are fundamental to understanding MPs contamination in urban drainage systems, being related to the diversity of sources and the qualitative and quantitative characteristics of MPs.