Stroebe Maximilian, Scheringer Martin, Hungerbühler Konrad
Institute for Chemical and Bioengineering, Swiss Federal Institute of Technology Zürich, CH-8093 Zürich, Switzerland.
Environ Sci Technol. 2004 Nov 1;38(21):5665-73. doi: 10.1021/es035443s.
The overall persistence, Pov, has been suggested as an indicator that integrates single media half-lives and phase partitioning. However, the application of this indicator is hindered by the fact that there are different definitions of Pov and that the most common measure of Pov, the residence time at steady state, depends heavily on the release pattern. Here, different measures are compared that can be used to compute Pov from the mass of a chemical in the environment as a function of time in a dynamic multimedia model. These measures include the equivalence width, which corresponds to the residence time at steady state, the mean value of the function of mass vs time ("mean time"), and the clearance time. The temporal remote state is defined as the state of the model system long after the stop of emissions; it is independent of the release pattern of a chemical. The mean time in the temporal remote state reflects the long-term removal rate of a chemical and is used as a persistence benchmark. Correlations of the three measures of Pov to the persistence benchmark are analyzed. The maximum equivalence width, which is obtained with release to one of the media air, water, or soil, is a good approximation of the mean time in the temporal remote state. Because the maximum equivalence width is identical to the maximum residence time at steady state, the mean time in the temporal remote state can be estimated with existing steady-state models.
总体持久性Pov已被提议作为一个整合单一介质半衰期和相分配的指标。然而，该指标的应用受到以下因素的阻碍：Pov有不同的定义，并且Pov最常用的衡量标准——稳态停留时间，在很大程度上取决于释放模式。在此，对不同的衡量标准进行了比较，这些标准可用于在动态多介质模型中根据环境中化学物质的质量随时间的变化来计算Pov。这些衡量标准包括等效宽度（对应于稳态停留时间）、质量随时间变化函数的平均值（“平均时间”）和清除时间。时间远程状态被定义为排放停止很久之后模型系统的状态；它与化学物质的释放模式无关。时间远程状态下的平均时间反映了化学物质的长期去除率，并被用作持久性基准。分析了Pov的三种衡量标准与持久性基准的相关性。通过向空气、水或土壤等介质之一释放所获得的最大等效宽度，是时间远程状态下平均时间的良好近似值。由于最大等效宽度与稳态下的最大停留时间相同，因此可以使用现有的稳态模型来估计时间远程状态下的平均时间。
