Research in Yellowstone National Park

Voltammetric probes to measure intermediate sulfur species were used at Yellowstone National Park:
Au-amalgam microelectrodes were used in YNP this past August at thermal springs in Norris and Sylvan basins, as well as in Alluvium Creek in Brimstone Basin.
They were able to identify H2S, HS-, polysulifdes, S2O32-, S4O62-, metal sulfide complexes, Fe2+, Fe3+, Mn2+, and As3+ at temperatures up to 90 degrees C.
We were working with Dan Rogers, a Ph.D. student at Woods Hole Oceanographic Institute in Dr. Katrina Edwards' lab.

Dan took microbial samples at these locations in the exact spots we were measuring the redox chemistry with the voltammetric probes.

You can see us working at cinder pool in the Norris Basin here - the retractable pole runs the wires to the probes and a tube run by peristaltic pump for sampling. Our potentiostat, batteries, and computer are in and on top of the wood box

Norris Basin - Cinder Pool
Cinder Pool was 89 C, pH 4.03 and largely covered with cinders. The cinders are made of elemental sulfur and pyrite, the result of CO2 and H2S gases bubbling through a liquid elemental sulfur layer at depth
Cyclic voltammetry at this site indicates the presence of significant polysulfides - we are currently working on quantifying these signals in the lab
Norris Basin - Realgar Springs
Realgar Springs actually contains more iron than arsenic, but does contain significant arsenic. Of the springs we looked at this season in the park, the voltammetric signals here were the most unusual. We are working on reproducing these signals at these conditions with additions of different forms of reduced S, As, and Fe.

Sylvan Springs Geyser Basin - Evening Primrose Spring
Results here showed the presence of significant quantities of thiosulfate, H2S, and polysulfides. We were able to significantly lower the detection limit for thiosulfate analyses by using a square wave scan at 500 mV/sec with a 50 mV pulse height. Thiosulfate (S2O32-), is present at a potential of approximately -0.2 to -0.3 V vs. Ag/AgCl (depending on concentration and scan rate).