INTEGRATING FIELD WORK, LABORATORY TECHNIQUES AND INSTRUMENTAL ANALYSIS INTO A RESEARCH COMPONENT OF AN UNDERGRADUATE ENVIRONMENTAL GEOCHEMISTRY COURSE (Invited Presentation)

Classes in environmental geochemistry present the opportunity to expose students to a broad spectrum of field, laboratory and analytical methods, from designing a sampling strategy and sample collection/preservation to various forms of chemical extraction, instrumental analysis and data interpretation. One obvious benefit of this approach is that students become exposed to hands-on skills that they might apply to careers in geoscience, but from a deeper teaching and learning perspective, this approach effectively requires that students carry out the full range of planning, preparation and critical analysis required of geochemical research. This presentation will highlight examples of hands-on activities in the field, lab and classroom that seek to integrate concepts, hands-on skills and analysis. One example that makes use of regional geology as well as the instrumental capabilities available at Middlebury College is a chemical speciation lab in which students (1) plan and conduct field work to obtain samples (e.g. ultramafic rock and soil or Pb-rich particulates filtered out of well water), (2) carry out XRD analysis on unextracted samples to determine bulk mineralogy, (3) prepare reagents (for sequential chemical extraction and also for ICP-AES chemical analysis), (4) carry out extractions, including replicate samples, (5) perform XRD analysis of extracted powders to assess mineral dissolution (internal standard-based), and (6) conduct ICP-AES analysis of extracted solutions. By examining compositions of extracted solutions in conjunction with XRD evidence of mineral dissolution, students are exposed to real datasets that require them to interpret results that provide insight into chemical speciation. The extraction stages are usually limited to a 4-step process involving 1M NH4NO3, 0.11 M HOAc, aqua regia and LiBO2-fusion for bulk composition, and students work in groups of 3 or 4 on small sample suites (4 or 5 specimens including replicates and a USGS or NBS standard). Students ultimately present data using typical graphical approaches (e.g. Eh-pH, ternary plots, mineral stability diagrams) and they also construct mineral stability diagrams from first principles and carry out similar calculations in class to complement the hands-on lab work.