The spatial distribution of microplastics in topsoils of an urban environment-Coimbra city case-study

Due to their seemingly ubiquitous nature and links to environmental and human health problems, microplastics are quickly becoming a major concern worldwide. Artificial environments, such as those found in urban environments, represent some of the main sources of microplastic. However, very few studies have focused on the occurrence of microplastics in urban soils. The aim of the current research was to evaluate the microplastic contamination in urban soils from artificial and natural land uses throughout Coimbra city, Portugal. Sixty-seven spaces and ten land use areas were evaluated. The artificial land use areas were dumps, landfills, parking lots, industries and construction areas, and the natural land use areas were forests, urban parks, moors (wetlands), pastures and urban agricultural areas. Microplastic extraction was done by density separation. Quantification and size measurements of microplastics was carried out using a microscope. Polymer types were identified by mu-FTIR for 25% of the samples. The microplastic content ranged from 5 x 10(3) to 571 x 10(3) particles center dot kg(-1), with a mean of 106 x 10(3) particle center dot kg(-1). The green park was the land use with the highest concentration of microplastics (158 x 10(3) particle center dot kg(-1)) and the forest was the one with the lowest concentration (55 x 10(3) particle center dot kg(-1)). The landfill (150 x 10(3) particle center dot kg(-1)), industry (127 x 10(3) particle center dot kg(-1)) and dump (126 x 10(3) particle center dot kg(-1)) were the artificial spaces with the highest levels of microplastics. The main polymers detected were polypropylene and polyethylene, followed by polyvinyl chloride and rubber, and the main sizes measured between 50 and 250 mu m. Our results indicate that natural spaces can contain higher amounts of microplastics as compared to artificial spaces in the urban environment. This suggests that microplastics are easily transported through the urban landscape and that urban green spaces can retain microplastics in their soils. Land use planning may present an opportunity to better control the levels of microplastics in urban environments.

Automated summary

Microplastics, due to their widespread distribution and evident impact on the environment and human health, have become a global concern. However, little research has been conducted on the occurrence of microplastics in urban soils. This study evaluates microplastic contamination in urban soils in Coimbra city, Portugal, and finds that natural land use areas may contain higher levels of microplastics compared to artificial land use areas.