School of Energy and Environmental Engineering, University of Science and Technology Beijing, Xueyuan Road No.30, Haidian District, Beijing 100083, PR China; Department of Isotope Biogeochemistry, Helmholtz Centre for Environmental Research-UFZ, Permoserstraße 15, Leipzig 04318, Germany.
Department of Isotope Biogeochemistry, Helmholtz Centre for Environmental Research-UFZ, Permoserstraße 15, Leipzig 04318, Germany.
Sci Total Environ. 2019 Apr 10;660:559-566. doi: 10.1016/j.scitotenv.2019.01.003. Epub 2019 Jan 4.
We systematically investigated the changes of carbon and hydrogen isotope signatures of three phthalate esters (PAEs) during (i) abiotic hydrolysis over the pH range of 2, 7 and 10, and (ii) aerobic biodegradation initiated by hydrolysis by Rhodococcus opacus strain DSM 43250. Significant carbon isotopic fractionation was exhibited under all investigated conditions. Hydrogen isotopic fractionation was observed in some experiments and is hypothesized to be a secondary isotope effect due to the absence of a hydrogen bond cleavage during hydrolysis. Dual stable isotope analysis (Λ = ΔδH/ΔδC) resulting from abiotic hydrolysis and aerobic biodegradation showed similar magnitudes for dimethyl phthalate (DMP) and diethyl phthalate (DEP). The calculated carbon apparent kinetic isotope effects (AKIE) for the hydrolytic pathway (CO bond cleavage) of PAEs fall within an expected range of 1.03-1.09, with the exception of lower AKIE values for dibutyl phthalate (DBP) during hydrolysis at pH 2 and aerobic biodegradation. The lower AKIE of DBP at pH 2 and aerobic biodegradation is likely related to a transition state from reactant-like to tetrahedral intermediate-like structure. Abiotic and biotic hydrolysis of PAEs resulted in similar AKIE and Λ values due to the CO bond cleavage pathway, indicating the potential of dual isotope analysis to detect and quantify hydrolytic processes of PAEs in the environment. The pronounced primary carbon and typically low secondary or absent hydrogen isotopic fractionation might form a typical pattern to identify the hydrolytic reaction of PAEs in the environment. The characteristic Λ values of the hydrolytic reaction were different from Λ values of chemical oxidation of PAEs and showed diagnostic potential of dual HC isotope analysis to analyze reactions.
我们系统地研究了三种邻苯二甲酸酯（PAE）在（i）pH 值为 2、7 和 10 时的非生物水解过程中和（ii）由 Rhodococcus opacus 菌株 DSM 43250 引发的水解引发的好氧生物降解过程中碳和氢同位素特征的变化。在所有研究条件下都表现出显著的碳同位素分馏。在一些实验中观察到氢同位素分馏，这被假设为二次同位素效应，因为水解过程中没有氢键断裂。非生物水解和好氧生物降解导致的双重稳定同位素分析（Λ=ΔδH/ΔδC）显示出邻苯二甲酸二甲酯（DMP）和邻苯二甲酸二乙酯（DEP）的相似幅度。PAE 水解途径（CO 键断裂）的计算碳表观动力学同位素效应（AKIE）落在预期范围 1.03-1.09 内，除了在 pH 值 2 时和好氧生物降解过程中二丁基邻苯二甲酸酯（DBP）的 AKIE 值较低。pH 值 2 时和好氧生物降解中二丁基邻苯二甲酸酯的较低 AKIE 值可能与反应物样到四面体型中间体样结构的过渡态有关。由于 CO 键断裂途径，PAE 的非生物和生物水解导致相似的 AKIE 和 Λ 值，这表明双重同位素分析有可能检测和量化环境中 PAE 的水解过程。明显的主要碳同位素分馏和通常较低的次要或不存在的氢同位素分馏可能形成一种典型模式，用于识别环境中 PAE 的水解反应。水解反应的特征 Λ 值与 PAE 的化学氧化的 Λ 值不同，并且表现出双重 HC 同位素分析分析反应的诊断潜力。
