LEAD ACCUMULATION IN AQUATIC PLANTS FROM METALLIC SOURCES INCLUDING SHOT

Ingestion of lead shot has coused the deaths of thousands of waterfowl during the past several decades. Toxicity of ingested shot is related to dietary factors such as fiber content, type of grit in the gizzard, and proportion of grain in the diet. Plants absorb lead from diverse sources such as lead additives in engine fuels released into the atmosphere, and geologic deposits of lead. Consequently, the authors decided to detemine if rooted aquatic plants could absorb enough lead supplied in metallic form to be a potential cause of plumbism in waterfowl. Root absorption from metallic sources was thought possible because native lead is geochemically unstable in the pH and oxidation potential (Eh) ranges expected in waterlogged soils. The specific salts formed and their solubility depend upon the activities of the various anions characteristic of a particular soil. However, several of the potential salts should become especially soluble at the root soil interface because the root surface may be more positive in Eh and higher in hydrogen ion activity than the waterlogged soil environment. The results indicate that those factors involving the availability, ingestion, and absorption of lead directly from shot should continue to occupy the primary attention of those investigating the etiology of plumbism in waterfowl.