Look, Mom! I grew me some biomarkers!: Cooking up some paleohydrology data in the lab with Iris and Jesse
As part of our contract to be a participant in an ITN funded by the Marie Curie Actions each PhD student is required, but ultimately encouraged to plan and implement a collaborative project with another student of iTECC. Some of the PhD students in iTECC have already planned and implemented a number of these “secondements” such as Gwladys Govin (University of Lancaster) and Natalie Vogeli (UJF Grenoble).
However, it was my turn to make a trip and I decided to visit Iris van der Veen in Potsdam, Germany at the Institute of Earth and Environmental Science. Here at the institute, Iris works with her supervisor Dirk Sasche using lipid biomarkers in samples such as soil, sediment and plants as a means to track the composition and details about the water that formed the plant at the time of its growth from O and H-isotopes in various regions of the Himalaya. And of course, at a later date, Iris will come to Nancy to work on the second half of the project that can be accomplished at CRPG.
Iris has completed a number of field campaigns in the very northwestern regions of India and Nepal focused around the Sutlej Valley and its tributaries. This area is in the rain shadow of the Himalaya and is thus characterized by very dry conditions. So, we sat down and had a meeting of the minds with our advisors and came up with the idea that it would be interesting to compare this very dry region of the Himalaya with a very wet region such as the Khudi Khola and Marysandi catchment using the lipid biomarkers techniques available at Potsdam.
So, I arrived at the end of January to a very cold, but welcoming Berlin. And thus, I am began the preparation of approximately 50 soil samples that comprise an elevation transect within the Khudi Khola from ~800 meters to just a bit above 4,000 meters. It is a long and grueling road to preparing samples for this technique, so here is quite an abbreviated description. First all of the lipids from a sample must be extracted and this is accomplished by using a machine called the ASE (Accelerated Solvent Extraction). Basically, a certain amount of the sample is loaded into metal cells and then fitted onto the ASE, which then injects the solvent Dichloromethane into the cell, heats its to ~100°C and exerts between 1400 and 1600 Psi for a period of 30 minutes. These protocols extract the lipids from the sample and push them into a collection vial for each sample. After the run on the ASE is complete, the samples are evaporated in a nitrogen Turbo-Vap. They are then transferred to smaller vials, evaporated again, silica gel columns are prepared and the samples are separated into different fractions. These fractions can be the alkane fraction, the fatty acid fraction, the alkanone fraction, etc. depending on the type of information that is needed.
The separated samples are then analyzed on the gas chromatography mass spectrometer (GC-MS) to determine how much of each compound is present. This is to ensure there is enough compound present for the later analysis of H isotopes, which is the next step. I am still somewhere in the middle of this process but work is progressing nicely and according to Iris my samples look very “lipidy.” So here’s to some good results!