Phosphates are mostly found on places where organic materials have decomposed, for example remains of meat or fish in settlements. The phosphates are insolutible in water and generally stay where they are disposed. Still, it can happen that they are transported with water.
An amount of soil (minimum 0,5l) is taken from the relevant sampling spot, and the location is marked with coordinates. The phosphates are separated with acid. High amount of organic material disposed on the spot will give a high amount of phosphates.
The density of samplingspots will form the basis of how detailled the result will be. While stone age settlements often have high and uneven values, iron age settlements often have uneven values, and the samples here must have higher density. Graves can be investigated in detail by dense sampling, and in some cases it is possible to determine where the body has been placed.
In Sundfjaera we aimed to collect samples every 10th meter in the area being excavated. Inside the dwellings samples were collected every 2nd meter. In mounds, cooking pits, firespots etc. the samples were collected denser and from profiles.