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Maximilian Stroebe

Publications and source records attributed to Maximilian Stroebe.

7 recordsLinked to original sources
PubMed2006

Effects of multi-media partitioning of chemicals on Junge's variability-lifetime relationship.

Junge's variability-lifetime relationship describes the relation between the tropospheric residence time of a volatile trace gas and the coefficient of variation of the tropospheric mixing ratio at a remote location. However, no unique or universal quantification of this relationship exists. It can only be derived on a case-by-case basis for consistent data sets on substances with similar source and sink patterns. Using a multi-media model of the long-range transport of organic compounds, we determine variability-lifetime relationships for volatile substances. Next, we demonstrate how the variability-lifetime relationship can be obtained for semi-volatile organic compounds (SOCs) with the model and we investigate typical deviations from the Junge relationship for volatile compounds that are caused by the multi-media partitioning of SOCs. One cause of deviation from this relationship is substances undergoing significant transport in water so that their distribution in air is noticeably influenced by their distribution in water. The other, wider, deviation is caused by substances with a strong tendency for deposition and re-volatilization. Finally, we address the comparison of the model results with field data. Preliminary analyses of long-term monitoring data for polychlorinated biphenyls at remote sites have shown that the identification of Junge relationships in field data is not straightforward. We discuss possible strategies for the derivation of Junge relationships from field data on SOCs.

Air Movements↗
PubMed2006

Application of multimedia models for screening assessment of long-range transport potential and overall persistence.

We propose a multimedia model-based methodology to evaluate whether a chemical substance qualifies as POP-like based on overall persistence (Pov) and potential for long-range transport (LRTP). It relies upon screening chemicals against the Pov and LRTP characteristics of selected reference chemicals with well-established environmental fates. Results indicate that chemicals of high and low concern in terms of persistence and long-range transport can be consistently identified by eight contemporary multimedia models using the proposed methodology. Model results for three hypothetical chemicals illustrate that the model-based classification of chemicals according to Pov and LRTP is not always consistent with the single-media half-life approach proposed by the UNEP Stockholm Convention and thatthe models provide additional insight into the likely long-term hazards associated with chemicals in the environment. We suggest this model-based classification method be adopted as a complement to screening against defined half-life criteria at the initial stages of tiered assessments designed to identify POP-like chemicals and to prioritize further environmental fate studies for new and existing chemicals.

Air Movements↗
PubMed2005

Comparing estimates of persistence and long-range transport potential among multimedia models.

Overall persistence (Pov) and long-range transport potential (LRTP) of organic chemicals are environmental hazard metrics calculated with multimedia fate and transport models. Since there are several models of this type, it is important to know whether and how different model designs (model geometry, selection of compartments and processes, process descriptions) affect the results for Pov and LRTP. Using a set of 3175 hypothetical chemicals covering a broad range of partition coefficients and degradation half-lives, we systematically analyze the Pov and LRTP results obtained with nine multimedia models. We have developed several methods that make it possible to visualize the model results efficiently and to relate differences in model results to mechanistic differences between models. Rankings of the hypothetical chemicals according to Pov and LRTP are highly correlated among models and are largely determined by the chemical properties. Domains of chemical properties in which model differences lead to different results are identified, and guidance on model selection is provided for model users.

Environmental Monitoring↗
PubMed2004

Measures of overall persistence and the temporal remote state.

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.

Environmental Monitoring↗
PubMed2004

Inter-comparison of multimedia modeling approaches: modes of transport, measures of long range transport potential and the spatial remote state.

Several evaluative multi-media models have been developed during the recent years to determine the long-range transport potential, LRTP, of non-polar organic chemicals. Here, these models are categorized and compared with respect to the modes of transport and the measures used to compute LRTP. Differences concerning the mode of transport include the transport mechanism (advective vs. dispersive transport) and the number and coupling of transport media (transport in a single moving medium vs. coupled transport in air and water). Measures used include the characteristic travel distance and the spatial range. The spatial remote state is defined as a benchmark for the comparison of the different measures. This is the state of the model system far-off the source that is independent of the release pattern. With the expected value in the spatial remote state as a benchmark, the maximum of the spatial ranges in air and water and the maximum of the characteristic travel distances in air and water as well as the spatial range in air in combination with release into water prove to be reliable measures of the LRTP. The framework developed allows one to overview the features of the different models used in the ranking and assessment of chemicals.

Air Movements↗
PubMed2004

The effect of export to the deep sea on the long-range transport potential of persistent organic pollutants.

BACKGROUND: Export to the deep sea has been found to be a relevant pathway for highly hydrophobic chemicals. The objective of this study is to investigate the influence of this process on the potential for long-range transport (LRT) of such chemicals. METHODS: The spatial range as a measure of potential for LRT is calculated for seven PCB congeners with the multimedia fate and transport model ChemRange. Spatial ranges for cases with and without deep sea export are compared. RESULTS AND DISCUSSION: Export to the deep sea leads to increased transfer from the air to the surface ocean and, thereby, to lower spatial ranges for PCB congeners whose net deposition rate constant is similar to or greater than the atmospheric degradation rate constant. This is fulfilled for the PCB congeners 101, 153, 180, and 194. The spatial ranges of the congeners 8, 28, and 52, in contrast, are not affected by deep sea export. With export to the deep sea included in the model, the spatial ranges of the heavier congener are similar to those of the lighter ones, while the intermediate congeners 101 and 153 have the highest potential for long-range transport. CONCLUSIONS: Transfer to the deep ocean affects the mass balance and the potential for LRT of highly hydrophobic chemicals and should be included in multimedia fate models containing a compartment for ocean water.

Air Movements↗