Fate of chlorpyrifos, atrazine, and metolachlor from nonpoint sources in wetland mesocosms.

摘要

Constructed wetland mesocosms (59--73 m x 14 m) were amended on two different occasions (one for the insecticide chlorpyrifos, the other for a mixture of the herbicides atrazine and metolachlor). Following each pesticide amendment, a simulated cropland runoff and rainfall event equal to three volume additions was imposed on each wetland. Targeted concentrations of chlorpyrifos were 73 mug/L, 147 mug/L, and 733 mug/L, while targeted concentrations for both atrazine and metolachlor were 73 mug/L and 147 mug/L in addition to an unamended control (0 mug/L). Water, sediment, and plant samples were collected weekly for the duration of each experiment (chlorpyrifos, 84 d; atrazine and metolachlor, 35 d). Samples were collected from sites longitudinally distributed within each wetland and analyzed for the respective pesticides using gas chromatography.; Chlorpyrifos rapidly sorbed to sediment and plant material, and the half-life in water, in this research, ranged from 5--13 d. Approximately 47--65% of measured chlorpyrifos was within the first 30--36 m (from inflow) of wetland mesocosms. Approximately 55% and 25% of measured chlorpyrifos mass were retained by sediments and plant material, respectively. Between 17 and 42% of the measured atrazine mass was within the first 30--36 m (from inflow) of wetlands. Atrazine concentrations were below analytical limits of quantification (0.05 mug/L) in all sediment and plant samples collected for this research. Atrazine aqueous half-lives ranged from 16--48 d. Between 7--25% of measured metolachlor mass was in the first 30--36 m (from inflow) of wetlands immediately following application and simulated rainfall. Approximately 10% of measured metolachlor mass was in plant samples.; According to results from this research, downstream or receiving system impacts could be mitigated by using constructed wetlands as "buffers" for agricultural pesticide runoff. This research provides fundamental answers concerning constructed wetland capabilities that are necessary for constructing field-scale systems within agricultural watersheds.