The effects of atrazine on dissolved oxygen and nitrate concentrations in aquatic systems

Abstract

The effects of the herbicide atrazine, on nitrate-nitrogen (nitrate-N) and dissolved oxygen concentrations in aquatic microcosms were determined. Treatment levels consisted of a control, 50, 100, and 150 μg/1 atrazine with four replicates per treatment. From a stock atrazine solution serial dilutions were prepared for each treatment level. The serial dilutions were added as single daily doses in 150 mL increments to the appropriate treatment. Dissolved oxygen was measured twice daily for each ssytem. Nitrate-N concentrations were measured twice weekly for the duration of the experiment. Dissolved oxygen was not resistant to the atrazine perturbation and decreased to concentrations approximating 0.0 mg/L for all atrazine concentrations. However, dissolved oxygen concentrations were resilient to perturbation and recovered to pretreatment levels within 48 h following cessation of toxicant input. Nitrate-N concentrations also were not resistant to the atrazine perturbation and decreased to more than 90% of the pretreatment concentrations following atrazine introduction. Nitrate-N concentrations for atrazine treatments exhibited high resilience to the perturbation. Nitrate-N concentrations recovered to approximately 90% of the preperturbation nitrate-N concentrations 48 h after cessation of the toxicant. Although small amounts of atrazine may have a significant impact upon aquatic systems by reducing levels of dissolved oxygen and nitrate, there appears to be no permanent ecosystem damage since these systems recover rapidly when atrazine levels return to zero.