Phosphorus amendment reduces bioavailability of lead to mallards ingesting contaminated sediments

Area of Science:

• Environmental Toxicology
• Wildlife Health
• Environmental Chemistry

Background:

• Waterfowl lead poisoning is a persistent issue in the Coeur d'Alene River Basin due to lead-contaminated sediments.
• Ingestion of these sediments by waterfowl leads to lead accumulation in their tissues.

Purpose of the Study:

• To investigate the efficacy of phosphoric acid amendments in reducing lead bioavailability to mallards (Anas platyrhynchos).
• To assess lead reduction in mallard tissues after dietary exposure to amended sediments under laboratory and field conditions.

Main Methods:

• Laboratory experiments involved amending sediments with phosphorus and feeding them to mallards.
• Field studies treated sediments with phosphorus and allowed them to age before assessing lead bioavailability.
• Lead concentrations were measured in mallard blood, liver, and kidney tissues.

Main Results:

• Phosphoric acid amendments significantly reduced lead concentrations in mallard tissues in both laboratory and field settings.
• Reductions varied by lead concentration and amendment method, with field applications showing higher efficacy.
• Despite reductions, lead levels in tissues of mallards fed amended sediments remained above harmful thresholds.

Conclusions:

• Phosphoric acid effectively reduces lead bioavailability in contaminated sediments.
• The effectiveness of this method is contingent on sediment lead levels, with benefits most significant for sediments containing less than 1,000-2,000 microg/g lead.
• Further research may be needed to optimize amendment application for higher lead concentrations to fully protect waterfowl.