Lead in Texas wetlands and its relationship to waterfowl hunting
Price, Linda Havighurst
Fisher, Frank M.
Master of Arts
Lead shot deposited in wetland ponds by waterfowl hunters over a number of years may be a significant source of lead in localized areas in this environment. To determine whether such shot contributes to the overall lead content of marshes, samples of soils, plants, fishes, crustaceans and ducks were collected in Chambers County, Texas, for lead analysis. Soil from sites near a waterfowl blind in a heavily hunted pond had significantly more extractable lead than soil collected in the same pond out of shotgun range of the blind; however, no differences in lead, attributable to spent shot, were noted between three ponds which had experienced different hunting pressures over the past ten years. Rather, the amount of lead in sections of core samples from the three ponds (mean of 66 ppm, dry wt) was related to clay content of the soils and was high compared to the average amount of lead reported in soils throughout the world. The level of lead, did not diminish down to 7 cm in two of the ponds examined. From the increase in extractable lead, noted 75 days after seeding pond soil with varying amounts of shot, a release rate of extractable lead from shot was calculated. The amount of lead found in plant tissue was correlated with the lead in the soil from which the plant was collected. More lead was found in plant roots than plant stems and blades. Mean amounts of lead in Eleocharis parvula (17.3 ppm), Paspalum virgatum (7.5 ppm) and the overall levels of lead in fishes (19.9 ppm) and crustaceans (37.6 ppm) were much higher than previously reported for such organisms. The mean amount of lead in ducks analyzed (5.7 ppm) was slightly above that reported for waterfowl in other surveys and 5$ of the ducks collected during hunting season had levels of lead characteristic of birds suffering from lead-poisoning.