An Interdisciplinary, Project-Based Inquiry into the Chemistry and Geology of Alkaline Surface Lake Waters in the General Chemistry Laboratory

摘要

A new project-based laboratory (PJBL) was developed for general chemistry students to tackle the steps involved in chemical water quality analysis using an accessible, real-world hydrologic system (the lakes of the Lower Grand Coulee, Washington). This PJBL was developed in a joint general chemistry and environmental geology course by a chemist-geologist teaching team, and it emphasized an interdisciplinary approach for a more complete understanding of the geochemistry of the lake system. Students worked through the project following industry protocols for sample collection in the field, chemical laboratory determination of dissolved solids, alkalinity, and dissolved metals, and interpretation of the results within the unique geological context of the lakes. Foundational concepts in solution chemistry, such as solubility product, pH, and alkalinity, were essential in the discussion of the lake water trends and broader geologic processes. In particular, students could relate chemical weathering of basaltic bedrock to the measured lake water constituents and could observe how the groundwater- and evaporation-controlled fluxes of water in the closed basin produced a downstream increase in alkalinity and dissolved load. Collectively, the steps involved in the project meet the essential criteria (as defined by other authors) for a complete chemistry PJBL. This PJBL can be readily adapted to a wide range of groundwater or surface water systems and can be framed in a more or less interdisciplinary context. Many students, without prompting and on confidential evaluations, rated this as the most valuable learning experience in the year-long academic coursework.