Ricardo Energy & Environment, Oxon, UK.
ExxonMobil Petroleum & Chemical, Machelen, Belgium; Concawe, Brussels, Belgium.
Sci Total Environ. 2020 Aug 25;732:139293. doi: 10.1016/j.scitotenv.2020.139293. Epub 2020 May 11.
Biodegradation is a major determinant of chemical persistence in the environment and an important consideration for PBT and environmental risk assessments. It is influenced by several environmental factors including temperature and microbial community structure. According to REACH guidance, a temperature correction based on the Arrhenius equation is recommended for chemical persistence data not performed at the recommended EU mean surface water temperature. Such corrections, however, can lead to overly conservative P/vP assessments. In this paper, the relevance of this temperature correction is assessed for petroleum hydrocarbons, using measured surface water (marine and freshwater) degradation half-time (DT50) and degradation half-life (HL) data compiled from relevant literature. Stringent screening criteria were used to specifically select data from biodegradation tests containing indigenous microbes and conducted at temperatures close to their ambient sampling temperature. As a result, ten independent studies were identified, with 993 data points covering 326 hydrocarbon constituents. These data were derived from tests conducted with natural seawater, or freshwater, at temperatures ranging from 5 to 21 °C. Regressions were performed on the full hydrocarbon dataset and on several individual hydrocarbons. The results were compared to the trend as predicted by the Arrhenius equation and using the activation energy (E) as recommend in the REACH Guidance. The comparison shows that the correction recommended in REACH Guidance over predicts the effect of temperature on hydrocarbon biodegradation. These results contrast with temperature manipulated inocula where the test temperature is different from the ambient sampling temperature. In these manipulated systems, the effect of temperature follows the Arrhenius equation more closely. In addition, a more striking effect of temperature on the lag phase was observed with longer lag phases more apparent at lower temperatures. This indicates that the effect of temperature may indeed be even lower when considering hydrocarbon biodegradation without the initial lag phase.
生物降解是化学物质在环境中持久性的主要决定因素，也是对 PBT 和环境风险评估的重要考虑因素。它受到包括温度和微生物群落结构在内的几个环境因素的影响。根据 REACH 指南，对于未在建议的欧盟平均地表水温度下进行的化学物质持久性数据，建议基于阿伦尼乌斯方程进行温度修正。然而，这种修正可能会导致对 P/vP 评估过于保守。本文使用从相关文献中汇编的测量地表水（海洋和淡水）降解半衰期 (DT50) 和降解半衰期 (HL) 数据，评估了这种温度修正对于石油烃的相关性。使用严格的筛选标准，专门选择了在接近环境采样温度的温度下进行且含有土著微生物的生物降解测试数据。结果，确定了 10 项独立的研究，其中包含 326 种烃成分的 993 个数据点。这些数据是在天然海水或淡水在 5 至 21°C 的温度下进行的测试中得出的。对完整的烃数据集和几种单独的烃进行了回归分析。将结果与由阿伦尼乌斯方程预测的趋势进行了比较，并使用 REACH 指南中推荐的活化能 (E) 进行了比较。结果表明，REACH 指南中推荐的修正方法过高估计了温度对烃类生物降解的影响。这些结果与温度操纵接种物的结果形成对比，在这些接种物中，测试温度与环境采样温度不同。在这些操纵系统中，温度的影响更接近阿伦尼乌斯方程。此外，在没有初始滞后期的情况下考虑烃类生物降解时，还观察到温度对滞后期的影响更为显著，低温下滞后期更长。这表明在考虑没有初始滞后期的烃类生物降解时，温度的影响实际上可能更低。
