Chlorine Isotope Effects and Composition of Naturally Produced Organochlorines from Chloroperoxidases, Flavin-Dependent Halogenases, and in Forest Soil

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• 作者：Christoph Aeppli ; David Bastviken ; Per Andersson ; 脰rjan Gustafsson
• 刊名：Environmental Science & Technology (ES&T)
• 出版年：2013
• 出版时间：July 2, 2013
• 年：2013
• 卷：47
• 期：13
• 页码：6864-6871
• 全文大小：380K
• 年卷期：v.47,no.13(July 2, 2013)
• ISSN：1520-5851

文摘

The use of stable chlorine isotopic signatures (未³⁷Cl) of organochlorine compounds has been suggested as a tool to determine both their origins and transformations in the environment. Here we investigated the 未³⁷Cl fractionation of two important pathways for enzymatic natural halogenation: chlorination by chloroperoxidase (CPO) and flavin-dependent halogenases (FDH). Phenolic products of CPO were highly ³⁷Cl depleted (未³⁷Cl = 鈭?2.6 卤 0.9鈥?; significantly more depleted than all known industrially produced organochlorine compounds (未³⁷Cl = 鈭? to +6鈥?. In contrast, four FDH products did not exhibit any observable isotopic shifts (未³⁷Cl = 鈭?.3 卤 0.6鈥?. We attributed the different isotopic effect to the distinctly different chlorination mechanisms employed by the two enzymes. Furthermore, the 未³⁷Cl in bulk organochlorines extracted from boreal forest soils were only slightly depleted in ³⁷Cl relative to inorganic Cl. In contrast to previous suggestions that CPO plays a key role in production of soil organochlorines, this observation points to the additional involvement of either other chlorination pathways, or that dechlorination of naturally produced organochlorines can neutralize 未³⁷Cl shifts caused by CPO chlorination. Overall, this study demonstrates that chlorine isotopic signatures are highly useful to understand sources and cycling of organochlorines in nature. Furthermore, this study presents 未³⁷Cl values of FDH products as well of bulk organochlorines extracted from pristine forest soil for the first time.