WP7 Bioavailability in Sediments / Water
Wednesday, 16 November 2005: 8:00 AM - 6:30 PM in Exhibit Hall

(REE-1117-852583) Effects of aquatic plants on metal bioavailability to benthic organisms.

Reed, E¹, Bailey, F¹, ¹ Middle Tennessee State University, Murfreesboro, TN, USA

ABSTRACT- Various methods have been evaluated to predict the bioavailability of metals in aquatic sediments. One well-known method uses the concentration of acid volatile sulfides (AVS) to predict the availability and toxicity of simultaneously extracted metals (SEM) to benthic organisms. Specifically, when the molar ratio of SEM/AVS is less than 1, no toxicity should occur because the metals should be bound to AVS. The SEM/AVS normalization does have limitations, however. For example, the SEM/AVS normalization cannot be applied to soils that may become oxidized (causing release of metals from AVS). It is well established that the American cattail, Typha latifolia, and other wetland plants form oxidized zones around their roots/rhizospheres. Limited research has been conducted to evaluate how this oxic root zone affects metal bioavailability to benthic organisms. The objective of this project is to address this issue. Typha latifolia plants were placed into glass microcosms (10"X14"X1") and were allowed to develop an oxic root zone in cadmium-contaminated soils (400ppm) with and without added AVS (AVS and Cd in equimolar amounts when AVS added). Typha root weights in the Cd treatment were significantly lower than in the Cd/AVS treatment, indicating that AVS may provide some protection to the plants from toxicity. However, there was no difference between the Cd and Cd/AVS treatments in the concentration of Cd in roots or shoots, which implies that an oxic root zone causes metals to be released from AVS and thus bioavailable to the plants. In a second set of experiments using the same treatments, Chironomas tentans larvae have been introduced into microcosms along with Typha to determine if the plants may render Cd available to benthic organisms even in the presence of AVS. Cadmium concentrations in T. latifolia and sediments as well as mortality and Cd concentration in C. tentans will be evaluated.

Key words: AVS, Typha latifolia, Cd, rhizosphere oxidation