Author
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JOHNSON, TERESA - UNIV OF ILLINOIS |
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Sims, Gerald |
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Submitted to: Letters in Applied Microbiology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 3/10/2000 Publication Date: N/A Citation: N/A Interpretive Summary: Results of laboratory environmental fate studies may be influenced by procedures used to conduct them. Limited solubility of pesticides in water often makes it necessary to use organic solvents to apply the compounds to soils. It is important to limit the volume of organic solvents applied to soil because most solvents are toxic to a variety of soil microorganisms. Conversely, application of a pesticide with too little solvent volume may result in uneven distribution. A study was conducted to examine the effects of commonly used laboratory solvents on degradation of the herbicide, 2,4-D in soil. The results showed that increasing the volume of organic solvent (or water) up to about two milligrams per kilogram of soil enhanced degradation, but above this value, no increase was gained from the use of additional water. Solvent toxicity dramatically reduced the degradation rate when more than two milligrams of solvent was used per kilogram of soil. These findings will be useful for improving the validity of laboratory degradation studies to better predict the fate of pesticides in the environment. Improved predictive tools are needed to reduce the impact of agricultural management practices on water quality. Technical Abstract: Xenobiotics are often dissolved in solvents to facilitate addition to soils in laboratory degradation studies. Due to potential toxicity effects, it is advisable to minimize carrier solvent volume; however, reducing solvent volume may detrimentally affect xenobiotic distribution in soil. The objective of this work was to investigate the relative effects of carrier solvent choice and volume on xenobiotic distribution, solvent toxicity, and degradation in soil. Incubations using six different carrier solvents were shown to affect the degradation of 2,4-D in soil. The overall fraction of 2,4-D mineralized generally decreased with increasing volumes of organic solvents (0.02-10 ul g-1 soil), while mineralization increased with increasing volumes of water used to introduce the pesticide. There may be substantial artifacts involved in mineralization studies, due to either limited distribution of xenobiotics or toxicity of organic solvents, depending upon the solvent and volume used to deliver a compound. When using organic solvents as carriers in xenobiotic degradation studies, both toxicity and uniformity of substrate distribution should be considered. |
