The beautiful weather here is a blessing and a curse. How do you expect me to accomplish anything inside when it looks like this every day?
Yes, this is the paradise that’s been my home for two months, and this valley is a ten minute walk from my apartment.
The standard for being productive in San Luis Obispo, which the locals refer to as “SLO”, is quite different than in Philadelphia. If you conquer the temptation to frolic outdoors in the sunlight and instead stay seated at your desk for half the day, you were productive. So, in order to accomplish something today (Friday), I took on a vampire’s mentality and found a dark cubicle in the library away from all windows and sunlight. I lasted two hours. Thankfully, the plants in the greenhouse needed watering, so I found myself in the bright outdoors, breathing the fresh air once again. Speaking of fresh air, the green fungus on top of the rocks pictured below is lichen. This microorganism thrives in good air quality, which is why it’s growing on practically every tree here.
Enough about nature, let’s talk about contaminants. If you haven’t read my previous posts, I’m basically studying whether native California plants translocate chemicals in contaminated soil through their roots, stems, and into the air as a gas. This is known as phytovolatilization. To capture any volatile chemical the plant is emitting, we secured an inert bag to the jar holding the plant and pump air through it into an activated carbon sorbent tube. Inert material is material that will not react or alter any chemicals that encounter it. Everything that the air from the plant headspace encounters must be inert so we know that the chemicals we find after analysis aren’t products of reactions that happened with the bag or tube.
How do I see what chemicals the activated carbon is catching? First I use a solvent, methylene chloride, to extract the activated carbon. Okay well first I put on the massive solvent gloves to prevent any spills from leaking into my skin. The captured organic contaminants adsorbed to the activated carbon should be more soluble in the methylene chloride and therefore detach from the carbon granules. Next, I sonicate the mixture. A sonicator uses high frequency noise to break the carbon granules into really small pieces. This ensures that all chemicals sorbed to it get dissolved into the solvent. Then the solution goes through some filtration and finally into the gas chromatograph, pictured below:
A gas chromatograph is basically an oven with thin hollow tubing on the inside, called a capillary column, that a gas carries your unknown sample through. The inside of the capillary column is coated, usually with silica, and the carrier gas in my case is helium. Depending on the mass of each unknown chemical and its attraction to the capillary column, each chemical will reach the detector at a different time, indicated by a graph with peaks at different times. Next, the mass spectrometer basically shoots electrons at each molecule, breaking them apart. The fragments a molecule breaks into are basically its finger prints, because it will break into those fragments every time. Using these two machines and the database of chemicals, I can determine which unknown chemicals were in my sample. Since this sample came from air that the plant was transpiring in, ideally the chemicals it volatilized will be captured and discovered. It’s pretty amazing that we have the technology to do this!