Sources and Fate of Microplastics in Urban Systems

Abstract

We all use plastics for a variety of purposes, and the amount of plastic produced and used is increasing worldwide, now reaching over 380 million metric tons (MMT) annually. Waste management in highly populated areas is currently insufficient to prevent large amounts of municipal waste from entering the environment; currently, the estimated annual mass of mismanaged waste is 80 MMT. With time, much of the plastic litter will degrade into microplastics, and once distributed, it is essentially impossible to remove. An estimated 4.8-12.7 MMT of plastics reach the ocean every year, while terrestrial systems are expected to accumulate 4-23 times more than the ocean. Waste generation, including microplastics, invariably follows human activities and plastic use. High-population densities infer higher generation and release of microplastics, leading to higher concentrations in urban areas. This chapter deals with the generation and release of microplastics, the dominant transport routes from major sources, and their distribution and fate in the urban environment. Proposed mitigation measures are also discussed. Methods of sampling, analysis, and reporting vary across countries, regions, and environmental compartments, causing uncertainties in mass-balances for microplastics. A few recent studies in or near urban areas provide new insight into patterns and trends of microplastics that underline areas of concern in terms of production, release, fate, and potential monitoring of microplastics in urban terrestrial and aquatic systems. A better understanding of major sources, distribution, and fate of microplastics is essential to engage in effective and sustainable preventive or mitigative actions targeting sites of high levels of microplastics.