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A revision of the Birkenes model of streamwater acidification has been attempted to incorporate additional chemical and hydrologic information gained in the last 6 years since its original construction. The first stage of this effort has been an analysis of the hydrologic submodel with the goal of extending it to predict concentrations of a conservative tracer in streamwater. An objective calibration of the model indicated that the model is overparameterized. Only one passive store is identifiabile, not two as currently contained in the model and the routing between the two reservoirs is not determined by the data. Inclusion of the conservative tracer improved the identifiability of the dimensional parameters, but had little effect on the rate or routing parameters. If the hydrologic structure is to be determined from the hydrograph and conservative tracer alone, it must be simplified to eliminate unidentifiable parameters. The validity of using more complex rainfall‐runoff models in hydrochemical models which seek to test chemical mechanisms is called into question by this analysis.

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Alternatives assessment has emerged as a science policy field that supports the evaluation and adoption of safer chemistries in manufacturing processes and consumer products. The recent surge in the development and practice of alternatives assessment has revealed notable methodological challenges. Spurred by this need, we convened an informal community of practice comprising industry experts, academics, and scientists within government and nongovernmental organizations to prioritize a research and practice agenda for the next 5 years that, if implemented, would significantly advance the field of alternatives assessment. With input from over 40 experts, the agenda outlines specific needs to advance methods, tools, and guidance in 5 critical areas: hazard assessment, comparative exposure characterization, life cycle considerations, decision making, and professional practice. Fifteen research and practice needs were identified, ranging from relatively simple efforts to define a minimum hazard data set to the development of more complex performance and decision-analytic methods and data integration tools. Some research needs involve adapting existing approaches to the alternatives assessment context, while others will require the development of entirely new methods and tools. The proposed research and practice agenda is ambitious. Implementing it will require expanding the current network of researchers from academia, government, and industry, as well as increased funding for methodological, application, and evaluation research. Integr Environ Assess Manag 2018;00:000-000. © 2018 SETAC.

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