P52

PHYTOREMEDIATION OF ATRAZINE-AND METOLACHLOR- CONTAMINATED WATER WITH SUBMERGED AND FLOATING AQUATIC PLANTS

The addition of the submerged aquatic plants, C. demersum and E. canadensis, significantly (p <0.01) reduced the concentration of [14C]metolachlor and [l4C]atrazine remaining in the water. After a 16-day incubation period only 1.4% and 41.3% of the applied [14C]metolachlor and [l4C]atrazine remained in the water of the incubations systems containing C. demersum, and 4.1% and 63.2% of the applied [l4C]metolachlor and [14C]atrazine remained in the incubations systems containing E. canadensis.

The nonvegetated incubations systems contained 61.2% and 85% of the applied [14C]metolachlor and [14C]atrazine, respectively. L. minor, a floating aquatic plant, only accelerated the removal of [14C]metolachlor from the treated water. The percent of applied [14C]atrazine remaining in the L. minor systems (85%) was comparable to the percent of applied [14C]atrazine remaining in the nonvegetated system (85%).

The herbicide-reduction efficiencies of the aquatic plants were, from most efficient to least efficient, C. demersum > E. canadensis > L. minor for both the metolachlor- and atrazine-treated systems. The accelerated degradation of metolachlor and atrazine was more important to the significant reduction of these herbicides in the water of the C. demersum systems than the sequestering of the herbicides in the plant. The quantities of metolachlor and atrazine degradates detected in the water of the vegetated incubation systems were, in descending order, C. demersum > L. minor = E. canadensis.

Herbicide accumulation in the plants followed the order of C. demersum = E. canadensis > L. minor for the metolachlor- and atrazine-treated systems. Our results provide evidence that the presence of herbicidetolerant aquatic plants can accelerate the removal and biodegradation of metolachlor and atrazine from herbicide-contaminated waters.

Key words: phytoremediation, bioremediation, aquatic plants, metolachlor, atrazine