Diuron sorption isotherms in freshwater biofilms

Area of Science:

• Environmental Science
• Ecotoxicology
• Aquatic Microbiology

Background:

• Biofilms serve as crucial bioindicators for water quality due to their contaminant integration and foundational role in aquatic food webs.
• Pesticides are prevalent in aquatic environments, leading to continuous exposure of aquatic organisms, including biofilm communities, at varying concentrations.

Purpose of the Study:

• To characterize pesticide sorption isotherms and uptake mechanisms within biofilms.
• To concurrently assess the bioaccumulation and toxic impacts of diuron on biofilms.

Main Methods:

• Mature biofilms were exposed to a range of diuron concentrations (1–500 μg·L⁻¹) under controlled flow conditions.
• Diuron bioaccumulation was modeled using Langmuir isotherm equations.
• Toxic impact, specifically photosynthetic inhibition, was assessed using an Emax model.

Main Results:

• Diuron bioaccumulation in biofilms was found to be nonlinear, with a calculated maximum accumulation of 17,771 μg·g⁻¹.
• Photosynthetic inhibition exhibited a dose-response pattern, with an EC50 of 75 μg·L⁻¹.
• A continuous diffusion phenomenon was observed, but it did not linearly correlate with bioaccumulation, indicating complex uptake mechanisms.

Conclusions:

• Pesticide behavior in biofilms is complex, involving nonlinear sorption and uptake mechanisms.
• The study provides a coupled toxicokinetic and toxicodynamic approach to understand pesticide impact on periphytic microorganisms.
• Findings offer novel insights into the behavior and ecological impact of pesticides in aquatic biofilm communities.