Microplastic diversity, risks and soil impacts: A multi-metric assessment across land-use systems

Area of Science:

• Environmental Science
• Soil Science
• Ecotoxicology

Background:

• Soil microplastic (MP) pollution is a growing environmental concern with poorly understood spatial patterns and ecological risks.
• Land use land cover (LULC) types are suspected to influence MP contamination and its subsequent effects on soil ecosystems.

Purpose of the Study:

• To assess MP abundance, diversity, ecological risks, and influence on soil properties across seven LULC types in the Brahmaputra Valley.
• To identify the relationship between LULC, MP characteristics, and soil physicochemical properties.

Main Methods:

• Integrated microscopy, spectroscopy-based MP identification, ecological diversity indices, and APCS-MLR modelling.
• Collected and analyzed 15 composite topsoil samples per LULC type.
• Utilized PCA and NMDS analyses to understand polymer composition's control on risks and soil properties.

Main Results:

• MP concentrations ranged from 5 to 57 particles kg⁻¹, peaking in built areas. Forest soils showed the highest polymer hazard score due to high-risk polymethylmethacrylate MPs.
• High-density polyethylene, polybutylene, and polyethylene terephthalate were dominant polymers. Black MPs and fibre/fragment shapes were most prevalent.
• Polymer composition significantly influenced soil properties (porosity, bulk density, SOC). Specific MPs (e.g., polyethylene, polystyrene fragments) positively impacted soil, while others (e.g., PVC, fibres) had negative effects.

Conclusions:

• LULC significantly influences the quantity, characteristics, and ecological risks of terrestrial MPs.
• Terrestrial MP pollution has implications for soil function and pollutant transport, necessitating polymer-specific monitoring and mitigation.
• The study provides a framework for understanding land-based pollution impacts on soil ecosystems.