Elementary, said he
|80s-tastic plasma lamp (Wikipedia)|
The sample (dissolved in liquid) is sprayed into the argon flame, and also becomes ionised. As different components in the sample become ionised they gave off a characteristic energy. The MS and OES parts is the bit that detects the elements present. MS does this by measuring their atomic mass, whilst OES measures the wavelengths of energy emitted by the elements. Each element produces a characteristic wavelength, so we can identify them on this basis.
|Preparing samples from Lake Nineris, Latvia|
And why do we want to measure elements you may ask? ICP is another one of those lab methods that has been developed for forensic and environmental applications then adopted by archaeologists. It is used routinely to look for metal toxicity in human blood and tissue samples, and to identify levels of pollutants in water. In archaeology, the idea is the same, but we are looking at the past history of such 'contamination' events. In the lake cores we have from the Baltic for the Ecology of Crusading project, we are measuring a range of elements in the sediments which can be linked to human activity. The lakes are located close to crusader castle sites, and pilot studies have linked signals such as increased lead to the castle construction. Other signals can be linked to activities such as landscape clearance.
|Dissolving sediments in HNO3|
So far I estimate there are about 60 samples per lake core, and maybe 15 lake cores. Eep.