RESUMO
The acute toxicities of a commercial dispersant (Corexit 9527) and four experimental dispersant formulations were evaluated using the 96-h mysid (Mysidopsis bahia) test and two rapid screening tests, Microtox and the Mysid IQ Toxicity Test. During 96-h toxicity tests, survival observations were recorded at 3, 6, 9, 12, and 24 h to document mortalities from short-term exposures more consistent with field exposure times and more approximate to exposure times used in Microtox and the Mysid IQ Toxicity Test. At nominal concentrations (6.25 and 12.5 mg/liter) and exposure times (3-24 h) near the upper range of predicted field conditions, mysid mortalities were =5% for all test materials. Microtox and Mysid IQ Toxicity Test were evaluated for their ability to differentiate test materials compared with that of the 96-h mysid test. Dispersant formulations were ranked by relative toxicities based on LC50 or EC50 values and ranks compared among test methods. Microtox ranked the test materials similar to the 96-h mysid test. Ranks from the Mysid IQ Toxicity Test were dissimilar to those of the other tests. Early mortality observations during 96-h tests did not provide a better basis for comparing results of the rapid screening tests.
Assuntos
Lipídeos , Tensoativos/toxicidade , Testes de Toxicidade , Animais , Crustáceos , Dose Letal Mediana , Espectrofotometria Ultravioleta , Fatores de TempoRESUMO
The compartmentalization and persistence of endothall, an aquatic herbicide, was studied using static greenhouse experimental pools. An overall aqueous pseudo-first-order decay rate coefficient of 0.173 day-1 and a half-life of 4.01 days were observed at endothall treatment levels of 0.03, 1.6, and 4.5 mg liter-1. Instantaneous sediment partition coefficients (Kp) were calculated at maximum endothall concentrations in sediments and ranged from 51.4 to 127.7. Bioconcentration factors (BCF) for the submerged aquatic macrophyte, Myriophyllum spicatum, ranged from 3.9 to 768.9. These instantaneous BCF values were calculated at the maximum M. spicatum endothall concentrations. The short aqueous half-life for endothall compares well with previous studies; however, both the Kp and BCF were one to three orders of magnitude higher than observed in a previous laboratory study and calculated from regression equations based on endothall solubility. Experimental pool studies can be important steps in translation of data from the laboratory to field and in the development of field sampling protocols that require understanding of expected behavior of a chemical in aquatic systems.