I’ve been working on learning how to use PHREEQC for a couple weeks now (see previous post for more of an introduction to the program) by reading the manual, studying examples, and reading other papers that have used it. I have been playing around with my data from a Tolhuaca water sample by equilibrating it with different mineral assemblages, evaporating water to simulate boiling, and mixing a groundwater-like solution with it to see how the element speciation and mineral saturation indexes change. Until this week, I had been having trouble understanding how to use the data output commands to create spreadsheets or graphs of calculated concentrations and mineral stabilities. But this week I finally figured it out! I can now create unique graphs using values I calculate in the program.
I have also been working on narrowing and simplifying the exact reactions and steps that I want to simulate in PHREEQC. This has been a bit of a challenge because trying to model an extremely complex, real-life system is difficult. The Tolhuaca geothermal system has many unique areas due to the pervasive hydrothermal alteration. These zones have different mineral assemblages, temperatures, and depths and therefore affect the hydrothermal solution differently. Right now I am focusing on just simulating water-rock interactions at 3-4 depths and the water-steam partitioning of elements. This
consists of reacting the water solution with the mineral assemblages found at each depth together with the pressure and temperature as well as modeling boiling near the surface. I hope to eventually be able to add hydrothermal solution interactions with the local groundwater and also use the solutions obtained in the various water-rock models to create a comprehensive transport model all the way from the geothermal reservoir (~1500 m) to the surface.
More fun in Santiago
In the beginning of May I went to my second US Embassy event in Santiago. They’re hosted by the US ambassador to Chile, Mike Hammer, and his wife in their house in the Las Condes (fancy/business) neighborhood of Santiago. The Fulbright students get invited to these reception events when a group of senators or something similar come to do some work in Chile. This reception was held in honor of Nancy Pelosi and her delegation, as they had been in Chile for about a week working on things like environmental and LGBT policies with the Chilean government. The first time I went to one of these was during the first week I was in Chile, and this time my Fulbright friends and I knew
better than to expect a meal. They just have waiters walking around with plates of small bites of Chilean specialties like ceviche, quinoa salads, and even tiny empanadas! This time they also served really good desserts. Of course, drinks include lots of wine and pisco sours. I like to go just to see how all my Fulbright friends are doing and talk to them. I did meet Nancy Pelosi, though, so that was neat.
Last weekend my friend Cinthia and I hiked up Cerro San Cristobal, the tallest hill in Santiago. It’s located pretty much in the middle of the city and is a nice landmark to orient you if you can’t see the cordillera. We walked up a steep walking path on the south side to the top, which has a huge statue of “La Virgen”, like many South American cities. There’s also a small church and store that sells religious items near the summit. The actual hill itself is very big, with many smaller parks scattered throughout. Cinthia and I walked down the opposite side on the road, which was full of people biking, running, walking, and driving up/down. One of the smaller parks we saw was full of musical instruments! There were really cool views of the city from the top, but the smog was terrible so we couldn’t see the Cordillera de los Andes. The smog has been much worse lately as winter approaches, but there are days when the rain clears the air and it’s really beautiful. Then you take notice of how bad it really was.