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ARS Home » Midwest Area » Ames, Iowa » National Laboratory for Agriculture and The Environment » Agroecosystems Management Research » Research » Publications at this Location » Publication #265597
Title: Dissipation of atrazine, enrofloxacin, and sulfamethazine in wood chip bioreactors and impact on denitrification

Author
item ILHAN, ZEHRA ESRA - Arizona State University
item ONG, SAY KEE - Iowa State University
item Moorman, Thomas

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/25/2011
Publication Date: 10/5/2011
Citation: Ilhan, Z., Ong, S., Moorman, T.B. 2011. Dissipation of atrazine, enrofloxacin, and sulfamethazine in wood chip bioreactors and impact on denitrification. Journal of Environmental Quality. 40:1816-1823.

Interpretive Summary: Wood chip bioreactors are receiving increasing attention as a means of reducing nitrate in subsurface tile drainage systems. These reactors convert nitrate to nitrogen gas through a microbial process called denitrification. Agrochemicals in tile drainage water entering wood chip bioreactors can be retained or degraded and may impact denitrification. The degradation of atrazine, a common herbicide, and two veterinary antibiotics, enrofloxacin, and sulfamethazine, was determined in a wood chip bioreactor. Initial half lives (time for 50% loss) for these chemicals were 0.98 days for atrazine, 0.17 days for enrofloxacin, and 6.2 days for sulfamethazine. Similar rates of disappearance in autoclaved and non-sterile wood chip solutions during the first 48 hours suggested sorption was the dominant mechanism. The presence of atrazine did not impair denitrification or affect the population of denitrifying microorganisms. The population of denitrifiers in sulfamethazine- and enrofloxacin-treated reactors were less than the reactors without the agrichemicals within the first 5 days after chemical addition, whereas the denitrification activities were not affected. However, after 45 days the denitrification rate, most probable number (MPN), and nitrous oxide reductase (nosZ) gene copy numbers for sulfamethazine and enrofloxacin were similar to that of the no-chemical control. This may indicate acclimation of the denitrifier population to the antibiotic or that reduced bioavailability over time allowed recovery of the denitrifier population. The study suggests that wood chip bioreators installed for nitrate removal may be effective in removal of pesticides and veterinary pharmaceuticals. This information may be useful to scientists, water quality specialists, and conservationists.

Technical Abstract: Wood chip bioreactors are receiving increasing attention as a means of reducing nitrate in subsurface tile drainage systems. Agrochemicals in tile drainage water entering wood chip bioreactors can be retained or degraded and may impact denitrification. The degradation of 5 mg L-1 atrazine, enrofloxacin, and sulfamethazine under denitrifying conditions in wood chips from an in situ reactor was determined. In addition, the impact of these chemicals on denitrifying microorganisms was assessed using the denitrification potential assay, most probable number (MPN) and quantitative polymerase chain reaction targeting the nosZ gene of the denitrifiers. Initial half lives for these chemicals in the aqueous phase were 0.98 days for atrazine, 0.17 days for enrofloxacin, and 6.2 days for sulfamethazine. Similar rates of disappearance in autoclaved and non-sterile wood chip solution during the first 48 hours suggested sorption was the dominant mechanism. The presence of atrazine did not impair denitrification potential, the MPN or nosZ copy number. The denitrifier MPN and nosZ copy number in sulfamethazine- and enrofloxacin-treated microcosms were less than the control within the first 5 days after chemical addition, whereas the denitrification potentials were not affected. However, after 45 days the denitrification rate, MPN and nosZ gene copy numbers for sulfamethazine and enrofloxacin were similar to that of the no-chemical control, indicating that acclimation of the denitrifier population to the antibiotic or reduced bioavailability over time allowed recovery of the denitrifier population.