C and N Isotope Fractionation during Biodegradation of the Pesticide Metabolite 2,6-Dichlorobenzamide (BAM): Potential for Environmental Assessments

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• 作者：Sandra Reinnicke ; Allan Simonsen ; Sebastian R. S酶rensen ; Jens Aamand ; Martin Elsner
• 刊名：Environmental Science & Technology (ES&T)
• 出版年：2012
• 出版时间：February 7, 2012
• 年：2012
• 卷：46
• 期：3
• 页码：1447-1454
• 全文大小：355K
• 年卷期：v.46,no.3(February 7, 2012)
• ISSN：1520-5851

文摘

2,6-Dichlorobenzamide (BAM) is a metabolite of the herbicide 2,6-dichlorobenzonitrile (dichlobenil), and a prominent groundwater contaminant. Observable compound-specific isotope fractionation during BAM formation鈥攖hrough transformation of dichlobenil by Rhodococcus erythropolis DSM 9685鈥攚as small. In contrast, isotope fractionation during BAM degradation鈥攚ith Aminobacter sp. MSH1 and ASI1, the only known bacterial strains capable of mineralizing BAM鈥攚as large, with pronounced carbon (蔚_C = 鈭?.5鈥?to 鈭?.8鈥? and nitrogen (蔚_N = 鈭?0.7鈥?to 鈭?3.5鈥? isotopic enrichment factors. BAM isotope values in natural samples are therefore expected to be dominated by the effects of its degradation rather than formation. Dual isotope slopes 螖 (=螖未¹⁵N/螖未¹³C 鈮?蔚_N/蔚_C) showed only small differences for MSH1 (1.75 卤 0.03) and ASI1 (1.45 卤 0.03) suggesting similar transformation mechanisms of BAM hydrolysis. Observations are in agreement with either a tetrahedral intermediate promoted by OH^{鈥?/sup> or H₃O+ catalysis, or a concerted reaction mechanism. Therefore, owing to consistent carbon isotopic fractionation, isotope shifts of BAM can be linked to BAM biodegradation, and may even be used to quantify degradation of this persistent metabolite. In contrast, nitrogen isotope values may be rather indicative of different sources. Our results delineate a new approach to assessing the fate of BAM in the environment.}