ATRAZINE SORPTION ON SURFACE SOILS –PHASE DISTRIBUTION AND AGING EFFECTS

摘要

Atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine), a broad-leaf herbicide, isrncommonly detected in ground and surface waters above the maximum contaminant level (MCL)rnfor drinking water of 3 μg/L (0.014 μM). The focus of this research was to develop a betterrnunderstanding of atrazine interactions with surface soils. Two soils of varying organic matterrncontents (an agricultural soil and a woodland soil) were compared in adsorption and desorptionrnexperiments using 14C-U-ring-labeled atrazine in sterile batch reactors. Aqueous atrazinernconcentrations of 0.25, 1.0, 2.5, 10.0 and 25.0 μM were used to simulate residual atrazine in soil,rnnormal application rates, and over-application or spill scenarios. Atrazine that sorbed to the soilrnwas sequentially water-, solvent-, and alkali-extracted to quantify the water-extractable, solventextractable,rnhumic acid-bound, fulvic acid-bound and soil/humin-bound atrazine. Phaserndistribution relationships (PDRs) were described for contact times of 1 hour, 1 day, and 1, 2, 4, 8rnand 12 weeks using the Freundlich model. The sorption capacity (KF) of both soils was observedrnto increase with time, while the sorption linearity (n) generally decreased. As contact timernincreased, more atrazine remained bound to the soil and soil organic matter. Over 90% of thernatrazine was removed with water after 1 hour of adsorption contact time, however as little asrn30% was water extractable after 12 weeks of adsorption.