A FIELD AND LAB EXERCISE DEMONSTRATING THE INFLUENCE OF SAMPLE TREATMENT ON ALKALINITY MEASUREMENTS

Students learn most effectively by hands-on activities. We designed an exercise to demonstrate to beginning geochemistry students the importance of proper sample collection, treatment, and storage as well as appropriate statistical treatment of data. During the first laboratory experience of the fall term on 29 August 2008, our neophytes collected samples along Fishing Creek, Bloomsburg, PA (Columbia Co.). Our nested sample design included four treatments over four time periods. Design included in situ measurements of temperature, pH, ORP, and conductivity. Students performed initial alkalinity analyses creek-side on triplicate samples from each of four sites (one site per team). They then filtered a second set of replicate samples (GFF with effective pore size of 0.8 μm), and a third set of replicate samples remained unfiltered. Half of both the filtered and unfiltered samples were kept at 4°C in the dark; the other half at room temperature in the light. At three intervals during the semester (1 week, 1 month, and 3 months), students analyzed samples for alkalinities in each of the treatments. Students performed statistical analysis (t-tests) of the on their analytical results for all treatments followed by classroom discussions of differences noted and possible reasons for those differences. The animated student discussions sparked by this exercise as well as student dedication to proper sample collection in later field projects (presented at another session of this GSA) indicated to us the effectiveness of this approach for emphasizing proper sample treatment.