PARENT SESSION
PW7 - Biotransformation / Metabolisms / Degradation
Wednesday, 20 November 2002
8:00 AM to 6:30 PM
Exhibit Hall

(P788) Mineralization of ¹⁴C-atrazine in coastal sediments: Impacts of sorption to humic substances.

Smalling, Kelly^*,1, Aelion, C. Marjorie^1,2, ¹ University of South Carolina, Department of Environmental Health Sciences, Columbia² University of South Carolina, Marine Science Program, Columbia

ABSTRACT- Atrazine, a persistent triazine herbicide, has the potential to bind tightly to soil organic matter minimizing degradation and ultimately becoming unavailable to microorganisms. Sediments high in organic carbon content may thus be a significant sink for atrazine in coastal aquatic systems. The removal and recovery of aged atrazine is difficult due to its irreversible sorption to organic carbon, especially humin. Mineralization of atrazine was monitored over time and subsequently an extraction method was developed incorporating a series of solvent washes followed by an alkali hydrolysis reaction to remove aged atrazine from South Carolina coastal sediments. Radiolabeled ¹⁴C-atrazine was added to field collected sediments, allowed to age in the dark at room temperature, extracted with ethyl acetate and dichloromethane and the radioactivity in each fraction was quantified using a liquid scintillation counter. Preliminary results indicated that minimal mineralization, measured as ¹⁴CO₂, occurred (< 2%) across all test sediments. Between 40 and 50% of the spiked ¹⁴C-atrazine was recovered from the sediment and water fraction during extensive solvent extraction. Another 20 to 25 % was removed from the humin fraction via alkali hydrolysis, in which the majority of the sorbed atrazine was recovered from the soluble fraction consisting of humic and fulvic acids. Only 10 to 15 % of the ¹⁴C-atrazine was not recovered at the end of the experiment. These results suggest that sorption, not biodegradation, plays a major role in determining the fate of atrazine in South Carolina coastal sediments with high organic carbon content.

Key words: atrazine, sorption, bioavailability, humic acids