Microplastics pollution: From continental sources to marine systems

Abstract

Microplastics are amongst the contaminants of emerging concern for aquatic systems. These ubiquitous environmental contaminants began to be reported since the 1970s, with increasing studies about their distribution and impacts from 2004. Although marine microplastics research remains at the forefront, studies on freshwater and terrestrial environments have begun to occur in this field as a matter of priority in recent years. This chapter addresses the influence of plastic pollution on marine environments through continental water bodies. Rivers and effluents have been identified as significant pathways from terrestrial sources releasing between 4.8 and 12.7 million metric tons of microplastics per year that reach the ocean. Microplastics are present in different sizes, colors, shapes and textures influencing their behavior in the environment. Also, their interaction with the biotic and abiotic systems influence the final fate and transport of them. The varied hydrological characteristics (water flow velocity, water flow seasonal variation, water depth) in lakes and rivers significantly affect plastics transport within freshwater systems towards the ocean. In estuarine environments, the combined effect of turbulence and salinity can interact with particle density, size, and charge. Added to this, storms, floods and runoff contributes to microplastics incorporation in the watersheds from soil and atmosphere. Therefore, the study of continental microplastics sources and pathways are critical to understanding them as emerging global contaminants.