Occurrence and seasonal distribution of microplastics and phthalates in sediments from the urban channel of the Ria and coast of Campeche, Mexico

Microplastics (MPs) are part of a global problem affecting all countries including those with smaller populations. Coastal sediments are a reservoir of pollutants generated in basins. Phthalate esters (PAEs) are used as additives to make plastics stronger and more flexible. Urban ecosystems are the most susceptible to receive and transport pollutants. In this study, we determined the presence of MPs and PAEs in coastal sediments and in an urban and natural drainage system, known as the "Ria" in San Francisco de Campeche city. Plastics were detected in all samples taken from both regions, with plastics ranging in size from 0.3 to 5 mm in diameter. This indicates that they are particles of plastics, paints, and fibers, which may come from boats and nylon nets or synthetic products. The greatest abundance of MPs was detected on the coast with quantities of 1392 items/m (dry weight), which is double than that seen in the urban channel. As for PAEs, the highest concentrations were determined in two sites: M7A with 18.292 μg g dw and PE with 21.702 μg g dw, with the Ría channel being the area with the highest concentration of PAEs totaling 49.315 μg g dw. The amounts of MPs detected in the sediments of the coast and the Ria vary significantly among the sites (p = 0.001) and seasons (p = 0.001), with the rainy season being the season where the greatest amount of MPs were detected. Likewise, the concentrations of ∑PAEs varied significantly among seasons (p = 0.0002) and sampling sites (p = 0.0001), with the west sub-basin being the site where the greatest concentration of PAEs was detected. A strong correlation was found between the ∑PAEs and MPs, which indicates that the conditions of the system favor the release and extended presence of PAEs on the coast.