UNDERGRADUATE RESEARCH ON THE BIOGEOCHEMISTRY OF A NATURALLY EFFERVESCENT SPRING NEAR MT. RAINIER

Yakima Valley College has a strong, summer undergraduate research experience (SURE) program. We believe that early undergraduate students are capable of original research and benefit from the experience and mentoring by faculty and non-teaching professionals. Mentors are encouraged to allow students to design their research questions as much as possible. Students are asked to complete pre- and post-experience surveys to gauge the impact of their experience.

The importance of making observations before interpretations is emphasized in our undergraduate research. Our study site, Soda Springs, is located just southwest of Hwy 410 between Naches and Mt. Rainier in Yakima County, WA. This project began with an initial site description using photos, sketches and descriptions of the site and surrounding area. Water chemistry was determined on site using the Vernier sensors temperature (T,°C), pH, specific conductivity (μS), salinity (ppm), dissolved oxygen (mg/L), turbidity (NTU) and CO₂ (ppm). Total dissolved solids (TDS) was done in the lab by quantitative evaporation. Testing of the mineral crust was done with dilute hydrochloric acid under a microscope. The flocculated mats downstream of the main springs were examined under a microscope.

Soda Springs is a cool (10°C), pH neutral spring, with profuse CO₂ effervescence, and an oxidized iron surface below the flow. It is thought that CO₂ can be naturally generated by several geologic processes: carbonic acid decomposition of carbonate rocks; outgassing from volcanic processes; entrapment in oil and gas rich (carboniferous) rocks. There are no carbonate or carboniferous rocks mapped in this area, and the proximity to Mt. Rainer and the Cascade subduction zone hints at a volcanic source for the gas. The effervescent water outflow leads to oxidation of iron, whether superficial or deep, chemical or biological, is yet to be determined. Left undisturbed, a carbonated mineral crust which traps the gas bubbles, grows on the surface waters just on top of the mud. Both sheath-shaped and spiraled-stalk filaments are observed in the flocked mats slightly down from the main springs. The morphology of these filaments is indicative of iron-oxidizing bacteria found at other iron-oxidized springs world-wide.