PARENT SESSION
Poster Session 37: Toxicology and Disease
Thursday, August 11, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal

Out of sight, out of the food web? Uptake of contaminants from soil-covered coal fly ash by terrestrial invertebrates in a forested floodplain wetland.

DeBiase, Adrienne^*,1, Taylor, Barbara ¹, McLeod, Kenneth ¹, Jackson, Brian¹, ¹ Savannah River Ecology Laboratory, Aiken, SC, USA

ABSTRACT- At least 40 ha of forested floodplain wetland on the Savannah River Site near Aiken, South Carolina, received deposits of coal fly ash up to 2.75 m deep. The ash zone has become revegetated, and a very shallow organic soil layer presently covers the ash. We asked whether the natural formation of an organic soil cover has effectively removed the contaminants associated with these wastes, including arsenic and selenium, from the wetland food chain. We established a sampling grid in the floodplain, extending beyond the ash zone. Contaminants were higher at ash sites (As: median 24.7 mg/kg in soil; Se: 4.3 mg/kg in soil, n=27 stations) than at control sites (As: median 2.8 mg/kg in soil; Se: 0.8 mg/kg in soil, n=28 stations). Analysis of woody and herbaceous vegetation from sampling sites with and without ash revealed consistently low concentrations of arsenic and selenium, suggesting that formation of overlying soil might have removed the ash from the food chain. We measured body burdens in four species of large, long-lived, relatively immobile invertebrates: the earthworm Lumbricus rubellus, and the land snails Haplotrema concavum, Mesodon sp. 1, and Mesodon sp. 2 from 6 ash sites and 4 control sites. (No species was found at every site.) All species showed elevated concentrations of selenium (up to 20 mg/kg dry mass) at the ash sites relative to the controls. L. rubellus and Mesodon sp. 1 species showed elevated concentrations of arsenic at the ash sites (up to 15 mg/kg dry mass), but Haplotrema concavum and Mesodon sp. 2 did not. In this system, concentrations of contaminants in vegetation are a poor predictor of uptake by the invertebrate consumers and consequently of the availability of contaminants to their predators, including amphibians, reptiles, birds, and small mammals. Furthermore, formation of an overlying soil layer did not appear to prevent contaminants from moving into the food web.

Key words: contaminants, invertebrates, arsenic, selenium