Microplastic Presence, Aging, and Potential Sources in Urban Runoff in a Large Piedmont Metropolitan Area:...

Area of Science:

• Environmental Science
• Hydrology
• Polymer Science

Background:

• Urbanization alters watershed hydrology, increasing urban runoff.
• Urban runoff is a significant source of microplastics (MPs), posing ecological and health risks.
• Identifying MP sources in large metropolitan areas is challenging.

Purpose of the Study:

• To conduct a polymer-type-specific exploration of MPs in a large metropolitan watershed (>16,000 km²).
• To identify the sources and influencing factors of microplastic pollution in urban runoff across diverse landscapes.

Main Methods:

• Collected 20,759 microplastics (MPs) from impervious surfaces, roof drainage, and soil slopes using laser direct infrared (LDIR) chemical imaging spectroscopy.
• Analyzed 11 polymer types across hilly and plain areas within a large metropolitan region.
• Employed multivariate statistical analyses, including partial least squares path modeling.

Main Results:

• Microplastic abundance was influenced by precipitation, topography, and rurality.
• Evidence indicated contributions from both local soil MPs and atmospheric deposition.
• Identified specific polymer types and their distribution across different sampling areas.

Conclusions:

• This study provides a comprehensive understanding of microplastic pollution dynamics in a large metropolitan area.
• Findings support the dual sources of microplastic pollution: local soil mobilization and atmospheric deposition.
• The methodology offers a promising approach for identifying microplastic sources in extensive regions.