Return of Microplastics from the Rivers Depth

Rivers are the arteries of Earth, carrying water, sediments, and dissolved substances from the land to the oceans. The ecosystem of rivers harbors a large part of biodiversity, such as plants and animals. Rivers are also the starting point of the first human civilizations. Early civilization depended on drinking water, food, agriculture, and transportation provided by rivers. Later, industries such as large power plants, food, beverage manufacturers, etc., settled near rivers because of easy access to water, transportation of products, and labor.

Human anthropogenic activities around rivers have altered their quality and quantity by changing land use and releasing pollutants into the air, land, and water [1]. The pollutants emitted from land into the rivers have significantly affected the physicochemical and biological quality of the rivers. Some of these rivers are used as the sole source of drinking water supply, while the magnitude of pollution emissions has already surpassed advances in water and wastewater treatment technologies.

Microplastics are among the pollutants that continuously enter rivers and eventually the oceans from the atmospheric and terrestrial emissions and effluents. The emitted microplastics can float or settle due to their density, shape and size, and other factors such as surface adsorption capacity [2]. When the microplastics’ travel time in the river is long enough, most of them have the chance to settle in the sediments. For example, in a 10 km river, the probability of microplastic deposition could be as high as 50% [3]. The latter may illustrate why efforts to prevent the release of microplastics into rivers are more important than addressing the problem later.

Consequent to natural or artificial instability in river sediments, microplastics are displaced and may reach the surface layer of the water while triggering an event, I would call a microplastic critical pollution wave (MCPW). MCPW affects water quality and natural aquatic communities. During MCPW event, significant quantities of microplastics will surface on riverbanks or enter the oceans and seas.

Prevention is ultimately better than treatment. Environmental authorities should be influential in raising public awareness regarding the critical situation facing urban residents and industries. Subsequent actions could address illegal practices that have led to the release of microplastics and pursue technical methods for separating microplastics from limited drinking water resources. 

[1]  Peters, N.E., Meybeck, M. and Chapman, D.V., 2006. Effects of human activities on water quality. Encyclopedia of Hydrological Sciences.

[2] Nikpay, M., 2022. Wastewater Fines Influence the Adsorption Behavior of Pollutants onto Microplastics. Journal of Polymers and the Environment, 30(2).

[3] Drummond, J.D., Schneidewind, U., Li, A., Hoellein, T.J., Krause, S. and Packman, A.I., 2022. Microplastic accumulation in riverbed sediment via hyporheic exchange from headwaters to mainstems. Science Advances, 8(2).