Distribution of microplastics in soil and freshwater environments: Global analysis and framework for transport modeling

Vera S Koutnik; Jamie Leonard; Sarah Alkidim; Francesca J DePrima; Sujith Ravi; Eric M V Hoek; Sanjay K Mohanty

doi:10.1016/j.envpol.2021.116552

Distribution of microplastics in soil and freshwater environments: Global analysis and framework for transport modeling

Environ Pollut. 2021 Apr 1:274:116552. doi: 10.1016/j.envpol.2021.116552. Epub 2021 Jan 23.

Authors

Vera S Koutnik¹, Jamie Leonard², Sarah Alkidim², Francesca J DePrima², Sujith Ravi³, Eric M V Hoek⁴, Sanjay K Mohanty⁵

Affiliations

¹ Department of Civil and Environmental Engineering, University of California, Los Angeles, CA, USA. Electronic address: vsmirnova@g.ucla.edu.
² Department of Civil and Environmental Engineering, University of California, Los Angeles, CA, USA.
³ Department of Earth & Environmental Science, Temple University, Philadelphia, PA, USA.
⁴ Department of Civil and Environmental Engineering, University of California, Los Angeles, CA, USA; UCLA Institute of the Environment & Sustainability, Los Angeles, California, USA; UCLA California NanoSystems Institute, Los Angeles, California, USA.
⁵ Department of Civil and Environmental Engineering, University of California, Los Angeles, CA, USA; UCLA Institute of the Environment & Sustainability, Los Angeles, California, USA. Electronic address: mohanty@ucla.edu.

PMID: 33545526
DOI: 10.1016/j.envpol.2021.116552

Abstract

Microplastics are continuously released into the terrestrial environment from sources where they are used and produced. These microplastics accumulate in soils, sediments, and freshwater bodies, and some are conveyed via wind and water to the oceans. The concentration gradient between terrestrial inland and coastal regions, the factors that influence the concentration, and the fundamental transport processes that could dynamically affect the distribution of microplastics are unclear. We analyzed microplastic concentration reported in 196 studies from 49 countries or territories from all continents and found that microplastic concentrations in soils or sediments and surface water could vary by up to eight orders of magnitude. Mean microplastic concentrations in inland locations such as glacier (191 n L^-1) and urban stormwater (55 n L^-1) were up to two orders of magnitude greater than the concentrations in rivers (0.63 n L^-1) that convey microplastics from inland locations to water bodies in terrestrial boundary such as estuaries (0.15 n L^-1). However, only 20% of studies reported microplastics below 20 μm, indicating the concentration in these systems can change with the improvement of microplastic detection technology. Analysis of data from laboratory studies reveals that biodegradation can also reduce the concentration and size of deposited microplastics in the terrestrial environment. Fiber percentage was higher in the sediments in the coastal areas than the sediments in inland water bodies, indicating fibers are preferentially transported to the terrestrial boundary. Finally, we provide theoretical frameworks to predict microplastics transport and identify potential hotspots where microplastics may accumulate.

Keywords: Biodegradation; Concentration gradient; Fiber percentage; Microplastic shape; Terrestrial plastics; Transport models.

Publication types

Review

MeSH terms

Environmental Monitoring
Fresh Water
Microplastics*
Oceans and Seas
Plastics
Soil
Water Pollutants, Chemical* / analysis

Substances

Microplastics
Plastics
Soil
Water Pollutants, Chemical