Atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine), a broad-leaf herbicide, is commonly detected in ground and surface waters above the maximum contaminant level (MCL) for drinking water of 3 μg/L (0.014 μM). The focus of this research was to develop a better
understanding of atrazine interactions with surface soils. Two soils of varying organic matter contents (an agricultural soil and a woodland soil) were compared in adsorption and desorption experiments using 14C-U-ring-labeled atrazine in sterile batch reactors. Aqueous atrazine
concentrations of 0.25, 1.0, 2.5, 10.0 and 25.0 μM were used to simulate residual atrazine in soil, normal application rates, and over-application or spill scenarios. Atrazine that sorbed to the soil was sequentially water-, solvent-, and alkali-extracted to quantify the water-extractable,
solvent-extractable, humic acid-bound, fulvic acid-bound and soil/humin-bound atrazine. Phase distribution relationships (PDRs) were described for contact times of 1 hour, 1 day, and 1, 2, 4, 8 and 12 weeks using the Freundlich model. The sorption capacity (KF) of both
soils was observed to increase with time, while the sorption linearity (n) generally decreased. As contact time increased, more atrazine remained bound to the soil and soil organic matter. Over 90% of the atrazine was removed with water after 1 hour of adsorption contact time,
however as little as 30% was water extractable after 12 weeks of adsorption.
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