Hi there. Today I would like to tell you something about pigments.
We can see pigments everywhere nature. See all the plants with their green colour.
Pigments are used for photosynthesis.
This is the process in which plants capture the light from the sun and use this to produce oxygen,
so it is the basis for our life on this planet.
Now I would like to show you what we can do with the pigments,
how we can look at them in more detail to learn about our past and present environment.
Welcome to our organic geochemistry laboratory.
Here we can look in detail at a pigment composition.
For example, we can look for pigments in lake sediments.
In a lake we have a lot of organisms living there - algae, bacteria.
When these organisms die they sink to the bottom of the lake and there they become part of the mud.
in this mud we get a preservation of all the pigments that are produced by the algae and bacteria in the lake,
and we can use these to find out more about which kind of organisms were living in the lake.
We can use these lake sediments as a history book, as an archive to reconstruct our lake history.
What was the oxygen concentration like?
How warm was the water temperature? How polluted was the water?
In this mud sample there are pigments from organisms that live in the lake,
So we can use this to isolate our pigments.
We need to use organic solvents to get all the pigments, all our compounds, into solution.
In order to now better dissolve our compounds of interest, our pigments, we can use ultrasound.
So there's sound waves which help us to better dissolve the sample.
And this is what we obtain as a result.
You see here a solution with pigments that originated from a variety of organisms -
plants, algae, bacteria that live in the lake.
But this is a huge mixture. We want to now separate all these different compounds to make them visible.
For this we can use thin layer chromatography. By putting the pigments on these specific plates,
we can separate the mix of the pigments into their different components.
For this we put drops of our solution on the start line, then we put it into a specific solvent solution.
And then you already see the different pigments moving upwards.
It is like a slow race - some pigments are smaller and faster, some others need more time to move.
More and more, all our different pigments get separated.
All these different colors represent different species.
The microbes that are present in this lake system are very simple.
This is another example from another lake, and you see all these bright pigments from a very diverse community.
In this example we see a lake which has very low oxygen concentration. How do we know this?
We find this yellow pigment and this reddish pigment. And we only have these pigments if the lake was very low in oxygen.
So this is one example of how we can learn about pollution, low oxygen concentrations, in a lake system.
Now I am showing you a very different instrument which does basically the same as these plates.
It is called a gas chromatograph mass spectrometer.
So now imagine there are thousands of organic compounds in the environment
so many compounds that are not visible as pigments are.
In such cases we can use such sophisticated instrumentation.
For example in this case, we have one sample in which you don't see any colored components.
We use one microlitre, which is 1/1000 of a millilitre.
We inject with the syringe a tiny amount into this instrument.
It works pretty much the same as our experiment in the lab with our pigments,
but in this case it generates results that we can see on the computer.
You see all these different peaks. Each peak is one compound that we found in our sample.
This compound for example is a hopanoid, a typical indicator for bacteria in our lake.
and most of these compounds are steroids which trace algae in the lake.
This instrument gives us so much more than what we can just to visually as we have seen before in the lab.
So this is our method of choice. It gives us so much insight into our environment,
to learn more about pollution of our lakes, to learn about climate warming,
about environmental and climate change.