Centre for Atmospheric Research Experiments, Science and Technology Branch, Environment Canada, 6248 Eighth Line, Egbert, L0L 1N0 Ontario, Canada.
Environ Sci Technol. 2012 Mar 6;46(5):2668-74. doi: 10.1021/es203287x. Epub 2012 Feb 14.
As the uses of polybrominated diphenyl ethers (BDEs) are being phased out in many countries, soils could become a secondary emission source to the atmosphere. It is also anticipated that the demand for alternative brominated flame retardants (BFRs) will grow, but little is known about their environmental fate in soils. In this study, the volatility and degradation of BFRs and organochlorine pesticides (OCPs) in soil was investigated. A low organic carbon (5.6%) urban soil was spiked with a suite of BFRs and OCPs, followed by incubation under laboratory condition for 360 days. These included BDE- 17, -28, -47, -99; α- and β-1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane (TBECH), β-1,2,5,6-tetrabromocyclooctane (TBCO), and 2,3-dibromopropyl-2,4,6-tribromophenyl ether (DPTE), OCPs: α-hexachlorocyclohexane (α-HCH) and (13)C(6)-α-HCH, trans-chlordane (TC), and (13)C(10)-TC. The volatility of spiked chemicals was investigated using a fugacity meter to measure the soil-air partition coefficient (K(SA)). K(SA) of some spiked BFRs and OCPs increased from Day 10 to 60 or 90 and leveled off afterward. This suggests that the volatility of BFRs and OCPs decreases over time as the chemicals become more strongly bound to the soil. Degradation of alternative BFRs (α- and β-TBECH, β-TBCO, DPTE), BDE-17, and α-HCH ((13)C-labeled and nonlabeled) was evident in soils over 360 days, but no degradation was observed for the BDE-28, -47, -99, and TC ((13)C-labeled and nonlabeled). A method to separate the enantiomers of α-TBECH and β-TBCO was developed and their degradation, along with α-HCH ((13)C-labeled and nonlabeled) was enantioselective. This is the first study which reports the enantioselective degradation of chiral BFRs in soils. Discrepancies between the enantiomer fraction (EF) of chemicals extracted from the soil by dichloromethane (DCM) and air were found. It is suggested that DCM removes both the sequestered and loosely bound fractions of chemicals in soil, whereas air accesses only the loosely bound fraction, and these two pools are subject to different degrees of enantioselective degradation. This calls for caution when interpreting EFs obtained from DCM extraction of soil with EFs in ambient air.
随着多溴联苯醚（BDEs）的用途在许多国家逐渐淘汰，土壤可能成为大气的二次排放源。预计对替代溴化阻燃剂（BFRs）的需求将会增长，但人们对它们在土壤中的环境归宿知之甚少。本研究调查了 BFRs 和有机氯农药（OCPs）在土壤中的挥发性和降解性。用一套 BFRs 和 OCPs 对低有机碳（5.6%）城市土壤进行了接种，然后在实验室条件下培养 360 天。这些 BFRs 和 OCPs 包括 BDE-17、-28、-47、-99；α-和β-1,2-二溴-4-(1,2-二溴乙基)环己烷（TBECH），β-1,2,5,6-四溴环辛烷（TBCO）和 2,3-二溴丙基-2,4,6-三溴苯基醚（DPTE）；OCPs：α-六氯环己烷（α-HCH）和（13）C-标记的α-HCH、反式氯丹（TC）和（13）C-标记的 TC。使用逸度计测量土壤-空气分配系数（K（SA））来研究添加化学品的挥发性。一些添加的 BFRs 和 OCPs 的 K（SA）从第 10 天到 60 天或 90 天增加，然后趋于稳定。这表明，随着时间的推移，BFRs 和 OCPs 与土壤的结合越来越紧密，其挥发性逐渐降低。替代 BFRs（α-和β-TBECH、β-TBCO、DPTE）、BDE-17 和α-HCH（（13）C 标记和非标记）在 360 天内明显降解，但 BDE-28、-47、-99 和 TC（（13）C 标记和非标记）没有观察到降解。开发了一种分离α-TBECH 和β-TBCO 对映异构体的方法，并发现它们与α-HCH（（13）C 标记和非标记）一起具有对映选择性降解。这是首次报道土壤中手性 BFRs 对映选择性降解的研究。从二氯甲烷（DCM）和空气中提取的化学物质的对映体分数（EF）之间存在差异。建议 DCM 去除土壤中被隔离和松散结合的化学物质，而空气仅接触松散结合的化学物质，这两个池受到不同程度的对映体选择性降解。这就要求在解释从 DCM 提取的土壤中获得的 EF 时要小心，因为这些 EF 与环境空气中的 EF 不同。
