Paper No. 1
Presentation Time: 8:10 AM


MCGUIRE, Molly M., Department of Chemistry, Bucknell University, Lewisburg, PA 17837 and HERMAN, Ellen K., Department of Geology, Bucknell University, Lewisburg, PA 17837,

Three fluviokarst streams in Centre County, PA, USA, were analyzed for changes in colloid mineralogy using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), which permits determination of colloid composition while the material remains in aqueous suspension. All of the colloids detected in ultra-filtered samples were silicates, predominantly quartz and layer silicates, but composition and concentration varied substantially among the three streams.

Elk Creek, Pine Creek, and Penns Creek all drain the Ordovician and Silurian carbonates and clastics that make up the fluviokarst of the Valley and Ridge of Central Pennsylvania. The three streams rise after travelling through carbonates and are perennial surface streams before they join together. Elk Creek drains northeast Brush Valley before flowing south through a gap in Brush Mountain to join Pine Creek in Penns Valley. The joined creeks then flow into Penns Creek, the primary drainage for west Penns Valley. The land use throughout the valleys is predominantly agricultural with forests occupying the surrounding ridges. Farming practices in the valleys range from organic farming to higher density/intensity animal operations with associated manure distribution.

Though the geology drained by each stream is very similar, the colloidal composition and load vary throughout. Elk Creek shows a decreasing colloidal load from its source at Smullton Sinks and Elk Creek Rising Spring with preferential removal of layer silicates as it flows to join Pine Creek. This is likely due to increasing ionic strength downstream from agriculture and aquaculture runoff. Comparatively Pine Creek has a higher colloidal load prior to joining Elk Creek. Though Pine Creek’s drainage is also dominated by agriculture at lower elevations, the water is of lower ionic strength. Penns Creek drains the largest basin and shows a substantial load with distinct mineralogy from the other streams.