Submitted to: Symposium Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 7/23/2007
Publication Date: 7/23/2007
Citation: Hunter, W.J., Shaner, D.L. 2007. Atrazine Remediation with Soybean Oil Based Biobarriers: Laboratory Studies. Symposium Proceedings. Abstract. Interpretive Summary:
Technical Abstract: In the US almost 35 million kg of atrazine (2-chloro-4-ethylamino-6-isopropylamino s-triazine) are used annually making it the most extensively used agricultural herbicide. This high usage associated with its high mobility in many soils and recalcitrant nature in deeper soils and aquifers makes it a commonly encountered groundwater contaminant. Because of health concerns the United States Environmental Protection Agency has set a MCL for atrazine in water of 0.003 mg/L. We evaluated atrazine removal by biobarriers containing soybean oil that were bioaugmented with a soil inoculum containing atrazine degrading microorganisms. The soil was from a field where the half-life of atrazine was approximately 3.5 days. For this study biobarriers were formed in sand filled columns by coating the sand with soybean oil as the columns were packed. The porous matrix allowed water to flow freely through the biobarriers while the oil provided a carbon rich and nitrogen poor substrate to the microbial inoculum. A simulated groundwater containing 1 mg/L atrazine was pumped through the columns for 30 weeks. At intervals effluents from the biobarriers were collected and analyzed for atrazine and key atrazine degradation products. The results showed that the biobarriers were effective. Atrazine levels in the effluents from the biobarriers declined slowly with time and by the 24th week of the study no detectable atrazine was present in biobarrier effluents (limit of detection < 0.005 mg/L). Larger amounts of atrazine were also removed by the biobarriers; when biobarriers were fed 16.3 mg/L atrazine 97% of it was degraded. Small accumulations of hydroxyatrazine were detected in the effluents but neither deisopropylatrazine nor deethylatrazine were present. The addition of 5 mg/L nitrate-N to the influent water interfered with the biobarriers and reduced their efficiency by almost 60%. Poisoning of the biobarriers with mercury chloride reduced degradation by almost 76% confirming that the degradation was due to biological activity and not due to abiotic factors. The results suggest that permeable barriers might be formed in situ by the injection of innocuous vegetable oil emulsions into an aquifer or sandy soil. Such barriers, when inoculated with atrazine degrading bacteria, might be used in situ to remove atrazine from a contaminated aquifer or to protect an aquifer from contamination.