Effect of chemical synergy and larval stage on the toxicity of atrazine and alachlor to amphibian larvae

摘要

We determined the acute toxicity of field-grade formulations of atrazine, alachlor and a 50:50 mixture of the chemicals to early and late larval stages of northern leopard frogs (Rana pipiens) and American toads (Bufo americanus). We conducted identical tests with rainbow trout (Onchorhynchus mykiss) and channel catfish (Ictaluru punctatus) to compare their sensitivity as bioindicators. The acute toxicity (96-h median lethal concentrations [LC50s]) of herbicides to amphibian larvae ranged from 47.6 mg/L for early-stage R. pipiens exposed to atrazine to 3.3 mg/L for late-stage B. Americanus exposed to alachlor.