אסיף מאגר המחקר החקלאי

Comparison of formation and biodegradation of bromacil oxidation products in aqueous solutions

Year:

1994

Source of publication :

Authors :

Volume :

42

Co-Authors:

Acher, A.J., Volcani Center, Institute of Soils and Water, Bet-Dagan 50250, Israel
Hapeman, C.J., Environmental Chemistry Laboratory, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, MD 20705, United States
Shelton, D.R., Environmental Chemistry Laboratory, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, MD 20705, United States
Muldoon, M.T., Soil Microbial Systems Laboratory, ARS
Lusby, W.R., Insect Neurobiology and Hormone Laboratory, ARS
Avni, A., Weed Science Laboratory, ARS
Waters, R., Environmental Chemistry Laboratory, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, MD 20705, United States

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Abstract:

A comparative study of several oxidation methods of aqueous bromacil (I) solutions was conducted as part of a series of investigations concerning the chemical and biological remediation of pesticide-laden wastes. Ozonation (A), UV photolysis at 254 nm (B), and sensitized sunlight photodegradation (C) methods were examined. The A products were isolated and their structures elucidated by mass spectroscopy, various 13C and 1H NMR techniques, and other chemical methods. Three main A products were identified: 3-sec-butyl-5-acetyl-5-hydroxyhydantoin (II, ca. 5%), 3-sec-butylparabanic acid (III, ca. 20%), and 3-sec-butyl-5,5-dibromo-6-methyl-6-hydroxyuracil (IV, ca. 5%), which was also synthesized via hydroxybromination of bromacil; a fourth product (VII) was obtained in minute amount but was not identified. The aqueous solutions of IV are unstable and its decomposition led to re-formation of I. The main products found in B [(3-sec-butyl-6-methyluracil (V) and a dimer compound, VI] and C (II and VI) were similar to those described previously. The biodegradation assays of I, A, B, and C solutions were investigated using activated sludge, a pure culture of Klebsiella terragena (DRS-I), or soil; they indicated that the B and C solutions were more biodegradable than A solutions, while the parent material (I) was nonbiodegradable. A phytotoxicity bioassay, using Nicotiana tabacum seedlings, showed complete detoxification of the B and C solutions but only partial detoxification of the A and IV solutions. An attempt has been made to evaluate the most suitable method of degradation of solutions of I.

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