AN ASSESSMENT OF THE HAZARD OF A MIXTURE OF THE HERBICIDE RODEO~(R) AND THE NON-IONICSURFACTANT R-11~(R) TO AQUATIC INVERTEBRATES AND LARVAL AMPHIBIANS

摘要

This study was conducted todetermine whether theaquatic herbicide Rodeo~(R) (active ingredient: glyphosate) and the non-ionic surfactant R-11~(R) (active ingredient nonylphenol polyethoxylate or NPE) adversely affect aquatic species including invertebrates and larvalamphibians. A Rodeo-7 R-11~(R) mixture was applied directly to thesurfaceof a pond in a manner that would produce atypically high concentrations of these compounds in water. Water samples were collected from the treated pond for chemicalanalyses and toxicity tests with the aquatic invertebrate Ceriodaphnia dubia. A toxicity test with the Rodeo~(R)/R-11~(R) mixture was also conducted to determine the LC_(50)valuefor the larval life stage of the northern leopard frog, Rana pipiens. Watersamples collected one hour after application contained the following mean concentrations: glyphosate, 1.83 mg/L; NPE, 1.10 mg/L; and 0.02 mg/Lof the NPE breakdown product nonylphenol (NP). Concentrations of glyphosate's primary breakdown product, amino methyl phosphonic acid (AMPA), were below the laboratory detection limit of 0.020 mg/L. Water samples collected from the treated pond were not acutely lethal to Ceriodaphnia dubia. The 96-h toxicity test with the Rodeo~(R)/R-11~(R) mixture using Rana pipiens produced LC_(50) values of 6.5 mg/L forglyphosate and 1.7 mg/L for NPE, indicating thatthe mixture is moderately toxic to the amphibian. Acomparison of toxic units for the herbicide and surfactant in the mixture indicated that the toxicity to larvalfrogs was likely due to R-11~(R) and not Rodeo~(R).