Pesticide toxicity towards microalgae increases with environmental mixture complexity.

Area of Science:

• Environmental Chemistry
• Ecotoxicology
• Analytical Chemistry

Background:

• Complex environmental samples, such as those from landfill leachates, often contain numerous contaminants.
• Identifying specific toxic compounds within these mixtures is crucial for environmental risk assessment.
• Polar Organic Chemical Integrative Sampler (POCIS) is used to collect contaminants from water bodies.

Purpose of the Study:

• To apply Effect-Directed Analysis (EDA) to identify toxic compounds in a complex environmental mixture from River Ponteils.
• To assess the toxicity of the mixture using a microalgal bioassay with Nitzschia palea.
• To investigate potential mixture effects contributing to the overall toxicity.

Main Methods:

• Extraction of an environmental mixture using POCIS deployed in River Ponteils.
• Application of EDA to the extracted mixture.
• Microalgal bioassay using Nitzschia palea to measure photosynthetic capacities as a toxicity endpoint.

Main Results:

• The environmental extract exhibited significant toxicity, inhibiting Nitzschia palea photosynthetic capacities by over 85% at the highest concentration.
• Diuron and isoproturon were identified as the most concentrated herbicides in the extract.
• EDA did not pinpoint a single causative agent but indicated that multiple compounds contributed to the observed toxicity.

Conclusions:

• The environmental mixture from River Ponteils is toxic to microalgae.
• While specific herbicides were present, the toxicity appears to result from mixture effects involving multiple compounds.
• EDA highlights the complexity of assessing toxicity in real-world environmental samples.