Highly variable soil dissipation of metaldehyde can explain its environmental persistence and mobility

Area of Science:

• Environmental Science
• Ecotoxicology
• Soil Science

Background:

• Persistent, mobile, and toxic (PMT) substances pose risks to drinking water.
• Metaldehyde molluscicide use leads to surface and drinking water contamination exceeding limits.
• Existing assessments underestimated metaldehyde's environmental persistence.

Purpose of the Study:

• Investigate metaldehyde degradation rates under various soil conditions.
• Determine factors influencing metaldehyde persistence in the environment.
• Assess if current risk assessments underestimate metaldehyde's environmental fate.

Main Methods:

• Conducted a series of soil degradation experiments.
• Used diverse soil types and environmentally relevant conditions in Northern Europe.
• Generated a distribution of DT50 values for metaldehyde.

Main Results:

• Metaldehyde DT50 values ranged from 3.0 to 4150 days, indicating potential persistence.
• Identified lack of prior exposure, high moisture, low temperature, and localized high concentrations as high-risk conditions.
• Observed low pesticide biodegradation in UK soils under specific conditions.

Conclusions:

• Metaldehyde can persist in the environment, contrary to previous predictions.
• Current environmental risk assessments may underestimate metaldehyde's persistence.
• Understanding degradation variability is crucial for protecting water resources from pesticide contamination.