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Archive for May, 2012

Chlorophyll analysis

Dr. Rakesh Mogul and students conducting chlorophyll analysis of soil crust samples using IR absorption

On our fourth day at the CSU Desert Studies Center on Zzyzx Road, we continued our analyses of the biological soil crusts and began to put together the results of our studies. The CSU students extracted chlorophyll from the crusts and the soils underneath, then measured amounts by looking at infrared absorption lines at several wavelengths that are characteristic for chlorophyll.

GPS data for soil samples

Mapping the GPS coordinates for our samples

 

I helped Mary Beth start mapping out the trends we saw in the various chemical analyses of the soils at the three main sites. She did most of the work, looking up geological maps of the area around Baker and the various types of rock outcroppings and unconsolidated valley fill deposits, then located all our sample sites from the GPS coordinates we’d recorded on Monday and created gradient arrows across the maps showing how the various elements and compounds trended between locations.

geologic map of area

Charting soil chemistry changes onto a geological map along Kelbaker Road

Most of the trends were to be expected, but a few were surprising. For example, there was more aluminum and calcium in the soil at the low density site than at the other two. We joked that all the pop cans left as trash scattered around the low density site (which was near Baker) might have been the source, but of course that would be impossible – it would take a huge number of cans, completely oxidized away, to leave any kind of aluminum residue. So we looked at the maps for possible sources. This site was in more of a playa lake bottom and probably has more clay in the soil (which we can confirm with the soil mechanics group), and clay is an aluminum silicate. The calcium could come from nearby limestone deposits.

Desert Studies Center

CSU Desert Studies Center on Zzyzx Road in the Mojave National Preserve. Baker, CA is in the distance.

Overall, our project is a good example of how field research is carried out –you start with a question and a site to test it at, consider the possible ways to isolate the data you need from all the other variables in the environment (such as pop cans), come up with experimental procedures and protocols, then travel to the site, collect the data, conducting both field and laboratory analyses, then analyze the results and try to make sense of it all. It isn’t quite the formal scientific method we teach in middle school science classes. Often the statistics aren’t as strong as you would like because you’re using ANOVA (analysis of variance) or MANOVA (multiple analysis of variance) techniques. Since many different conditions are being tested, and you have to see how they all stack up and compare, often there are only a few data points per data set.

Soda Lake playa

Soda Lake playa in the Mojave Desert

It’s not as neat and predictable and controllable as a lab experiment, but it’s a lot more fun. For us, our biggest problem was trying to draw conclusions from the tests we ran, which were more qualitative and less reliable than we would like. The one test kit was designed for gardeners to use, and had test strips that only showed low, medium, and high results without any kind of ratio data. We also had some more individual tests for specific elements and compounds (such as chlorides or sulfates) that were a bit more numeric (at least they had scales) but not much more reliable. Often when we tried to do a sample a second time, the results weren’t very consistent. So we’d have to run the test a third time, or try to filter the soil better, etc. For our final results, we can’t rely on these inaccurate field tests. We’ll have to send the samples in for detailed lab analysis to find out the precise percentages of different elements. It will be interesting to see if our field results match up.

Borax stripes

Stripes in salt falt where borax and soda have been scraped up.

I also took the opportunity to climb a low hill behind the lab with my camera equipment to get a good look at the surrounding desert. From up there, I could see back to Baker and I-15 in one direction and toward the Kelso Dunes and deeper into the Mojave National Preserve in the other direction. This research station was originally a way station on the overland stage route, then eventually became a center for borax mining. On the other side of the hill, parallel trenches can still be seen where the borax powder was scraped up and piled, to be shipped out by the famous 20-mule teams. This is the low point in this valley and a salt flat/playa lake surrounds the Soda Springs area. It probably looks pretty barren and inhospitable to most people, but this is the kind of scenery I’m used to growing up in the Pahvant Valley of western Utah, with Sevier Lake and frequent evaporated alkali deposits to the west of my father’s farm. The weather has gradually warmed up from the freezing wind that greeted me on Sunday night.

borax minerals

Borax minerals and a model of the 20-mule teams that hauled the borax.

The commons room has some displays showing borax crystals and brief descriptions of how the mining was done, as well as the natural history of the station with local flora and fauna. The boron compounds (usually borates such as sodium and calcium borate) are generally known as borax, and have many uses. Borosilicate glass is highly heat resistant and is used in chemical lab ware, where we know it as Pyrex. It is also being used to contain and store radioactive wastes; since glass is highly stable chemically, the spent nuclear fuel rods are mixed with the glass in the form of marble-sized spheres or as sheathed glass columns. Borax also helps to extend laundry detergent, and provides the green color for fireworks.

History of borax mining part 1

The history of borax mining, part 1

I use borax to create the cross-linked polymerization when I make “gak” in my chemistry classroom. Here’s the recipe: take two paper cups. In one, fill it about ¼ full of warm water and ¼ full of white glue, plus a little food coloring. In the second cup, fill it about 1/3 full of warm water and about 10-15 grams of borax powder. Stir it up well, then mix the two cups together and keep on stirring. At first it will be a sticky mess, but in a minute or so the cross-linking between the glue strands will begin and water molecules get trapped in the borate links, making the whole thing into a fun, gloopy concoction that can be kneaded and molded.

I am including here two photos of the poster that describes borax mining, which you can read to find out more of the history. I’ll create a dedicated post later on going into more detail after I do some more research.

Timeline for Soda Springs Station

Timeline for Soda Springs and Zzyzx station

History of borax mining part 2
History of borax mining, Part 2
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