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Proposed relationships between the surfactant properties and the developmental toxicity induced in frog embryos of Humic acid.

Humic acid (HA) is as an anionic surfactant that promotes the mobilization of a non-aqueous phase liquid (NAPL) in a porous medium. HA is extracted from peat by a simple series of acid/base extractions. The critical micelle concentration (CMC) was determined as the lowest concentration of HA needed to produce maximal effect on the surface tension in distilled water. Short-column tests of a HA solution at the critical micelle concentration (CMC) of 3.4 mg/ml were used to evaluate the applicability of HA as a surfactant. HA improved the NAPL removal efficiency up to about 81% as measured by simple column flushing tests. HA developmental toxicity was also tested using the Frog Embryo Teratogenesis Assay-Xenopus (FETAX) methods. ToxTools[R] was used to estimate 50% effect levels, 30% and 10% effect levels for HA. The 96-hr LC50 was approximately 4.0 mg/ml and the 96-hr EC50 (malformation) was greater than 4.05 mg/ml and therefore could not be estimated accurately. Although malformations were observed, no significant teratogenic effect is evident for HA in Xenopus embryos. The HA has an LC50 in the vicinity of the CMC, which is the optimum concentration for using the HA as a surfactant. This indicates that the toxicity maybe due to the disruption of cell membranes. This work was supported in part by a Faculty Research Grant from JSU.

James R. Rayburn, David Steffy, And Cody St. John. Biology Department, Jacksonville State University, Jacksonville, AL. 36265
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Title Annotation:Biological Sciences
Author:Rayburn, James R.; Steffy, David; St. John, Cody
Publication:Journal of the Alabama Academy of Science
Article Type:Brief Article
Date:Apr 1, 2003
Words:244
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