Toward Optimizing Microplastic Transport Models through Biofouling Experiments.

Area of Science:

• Environmental Science
• Fluid Dynamics
• Microplastic Research

Background:

• Biofilms form on microplastics, influencing their transport in aquatic environments.
• Current freshwater microplastic transport models often lack validated biofouling parametrizations.

Purpose of the Study:

• To provide empirically supported guidelines for incorporating biofouling into freshwater microplastic transport models.
• To experimentally assess the influence of microplastic properties on biofilm development.

Main Methods:

• Laboratory experiments using diverse microplastics (varying polymer type, size, shape).
• Mass-based and image-based approaches to quantify biofilm development.
• Analysis of biofilm impact on microplastic vertical velocity.

Main Results:

• Biofouling significantly affects vertical velocity (>50% change) for particles <10 μm or with density close to fluid density (<4 months simulation).
• Biofouling effects are negligible for simulations of a few days with microplastics >400 μm.
• Linear or exponential models adequately describe biofilm growth within the first four months.
• Measured linear biofilm growth rate: 0.061–0.170 μm/week.

Conclusions:

• Experimental data supports the implementation of biofouling in microplastic transport models.
• Specific conditions (particle size, density, simulation duration) determine the significance of biofouling.
• Simplified biofilm growth models are applicable for short-term simulations (first four months).