2015Posted by Ruth Vingerhagen Feb 12, 2016 15:13
I still had a few remaining samples from my trip to Michigan where I hadn't measured the Sr isotopic composition. Since the machines in St. Andrews were still not up and running I went to the University of Cambridge
for a week and with the help of Hazel Chapman I filled in this missing gap in my data set.
My water data set is now complete but to properly interpret it I need to analyse the rocks and sediment samples that I collected. First I will need to find a good method for dissolving shale which is one of the harder rock types to fully dissolve.
2014Posted by Ruth Vingerhagen Feb 12, 2016 15:06
U data now in! Here too there are interesting differences between the two catchments.
2014Posted by Ruth Vingerhagen Feb 12, 2016 15:03
The new clean labs in St. Andrews are complete! They consist of two rooms for doing isotope work and one room for the instruments to measure the isotope ratios of samples. There is still some work to go though to make sure all the necessary equipment is there, but hopefully I can start to process my samples, especially the sediment samples, in the not too distant future.
2014Posted by Ruth Vingerhagen Feb 12, 2016 14:59
We had observed a positive correlation between the oxygen and sulfur isotopes of sulfate in the stream water from Dryadbreen (glaciated catchment). This is often attributed to sulfate reduction. At the temperatures found on the Earth's surface this reaction is microbially mediated so to see if any microbes were reducing sulfate we looked for the dsrAB
gene. But we didn't find any which means something else is causing that correlation...
2014Posted by Ruth Vingerhagen Feb 12, 2016 14:48
Poster presentation at EGU: the sulfur and bacteria data are coming together into a coherent story!
I also made a video for the EGU 'Communicate your Science' competition about this project which can be viewed here
2014Posted by Ruth Vingerhagen Feb 12, 2016 14:38
After talking to Eric Boyd (University of Montana) at the Goldschmidt conference last year we decided it would be interesting to look at the bacterial community present at my sampling sites with the expectation that they would influence the chemical composition of the stream water. I posted off four sediment samples and now the results are back! The analysis done is called 16S rRNA sequencing: bits of RNA are sequenced and compared with a database of known bacteria to see if they match. This approach gives an idea of which bacteria are there but not whether they are active or not. Now I have to read up on microbiology in order to understand this data!
2014Posted by Ruth Vingerhagen Feb 12, 2016 14:25
Just back from a two week visit to Sarah Aciego's group (GIGL
) at the University of Michigan. The aim of the trip was to do geochemical analysis of my water samples which I wasn't able to do in St. Andrews. The first week was spent in the lab separating out strontium (Sr), uranium (U) and neodymium (Nd) from the other elements in the water samples. This is done using a series of columns filled with a resin which binds to the elements with varying strength. In the second week I was able to do some measurements on the TIMS (thermal ionisation mass spectrometer) for Sr and Nd isotopes. The samples for U isotope analysis will be done later at the University of Wyoming.
Why these elements? Sr and Nd will provide information on the source of the water. Different minerals and rock types will have different isotopic compositions so we can use these measurement to tell what is weathering and contributing to the stream chemical composition and how that varies over time. Sr is also useful for giving information on the snowmelt contribution to the stream waters. The U data will be used to give information on erosion processes.
Thanks to the whole GIGL group for a successful trip!
2013Posted by Ruth Vingerhagen Feb 12, 2016 12:58
The solid samples haven't been neglected either. All the solid samples (river sediments and moraine samples) have been dried. Part of the sample has been used to obtain a clay separate for each sample and the rest of the sample has been gound to a fine powder in preparation for chemical characterisation.