PHYTOAVAILABILITY AND BIOACCUMULATION OF CADMIUM IN DUCKWEED PLANTS (SPIRODELA-POLYRHIZA L SCHLEID)

The aquatic vascular plant Duckweed (Spirodela polyrhiza L. Schleid) w as investigated as a potential biological filter for wastewater Cd rem oval. Duckweed plants were grown in and harvested weekly from 0.10 M H oagland nutrient solutions containing 0.04-7.63 mu g Cd/mL. Dry weight s of plants significantly decreased when exposed to 7.63 mu g Cd/mL. F or both the 1.03 and 7.63 mu g Cd/mL treatments the greatest Cd accumu lation in plants occurred during week 1 and decreased through week 4. It was also interesting to note that tissue P was observed to be suppr essed for one week at higher Cd treatments, and thereafter increased a s the tissue Cd levels decreased. Frond production was decreased by th e lowest Cd treatments by the second week. These results suggest that Duckweed can tolerate and accumulate Cd for one week even when exposed to 7.63 mu g Cd/mL. However, after one week the plants needed to be r emoved fron 1 the Cd solution to avoid tissue Cd loss and to achieve m aximum removal from solution.