The Tellus geochemistry field programme requires the careful collection of soil samples.
Care should be taken when selecting a soil sample site.
Ensure the site is representative of the surrounding area.
If possible, aim for a site central to your grid square, choosing undisturbed and unforested
land where possible.
Stay away from any evident sources of contamination.
The sample site must fulfil a number of distance criteria.
For example, at least 100 metres away from any features that are present or are
mapped including minor roads, streams, buildings and electricity pylons,
and at least 200 metres away from rivers, large water bodies, quarries, railway lines and major roads.
At the chosen sample collection site, note the exact location
using your handheld GPS unit.
Both samplers should cross check the location on the 1:50,000-scale field map and confirm
that the site meets all criteria and is suitable.
Before beginning any sampling, all the large brown Kraft® paper sample bags need to be
labelled at the same time, by the same sampler.
Label bags with the six figure site number,
approximately one third down the front of the bag.
On one, write the letter ‘A’ below the site number
and, on the other, the letter ‘S’.
Underneath, write your own initials, followed by the initials of your field partner.
Before collecting any samples, the auger must be used once to remove material from any previous
site and to pre-contaminate ahead of sampling at this site.
To do this, collect one full auger flight of material and discard this material.
Kick away the top rootlet or leaf litter zone before inserting the auger.
The first sample is collected from the top layer of soil, to a nominal depth of 20 cm.
Ensure the auger is upright and your back is kept straight.
Use a pushing and clockwise rotating motion until the top of the auger flight is level
with the ground surface.
Remove the auger and take note of the sample characteristics.
These include colour, texture, water and organic content, clasts lithology and the presence
of any contaminants.
Describe the characteristics to your partner and note these observations.
Place the sample in the bag labelled ‘A’.
Return the auger to the same hole and turn it several times until the flight is filled.
Remove the auger and note any changes in the soil characteristics such as colour and texture.
This intermediate auger material should then be discarded.
Once again, return the auger to the same hole.
Turn the auger until the tip reaches a depth of 50 cm.
This depth is reached when the coloured tape on the shaft of the auger is in line with
the surface.
Remove the auger and, as before, note your observations about the sample.
Place the soil sample material into the bag labelled ’S’.
Always make an effort to fill the hole after sampling.
Soil samples are a composite taken from five independent auger holes
in a 20 metre by 20 metre square arrangement, with the first hole in the centre of the square, which is also where
the GPS coordinates are recorded.
This formation resembles the number 5 on a die.
At each hole, collect the same set of samples.
First, a topsoil sample from an auger flight from just below the surface, nominally to
20 cm depth, known as sample type ‘A’.
Next, an intermediate flight, which is discarded.
Finally, a subsoil sample aiming to reach 50 cm depth, known as sample type ‘S’.
To measure the distance between sampling holes, count the number of strides taken.
In order for this to be accurate, you should know your stride length in advance.
Remember that your stride length will vary on different types of terrain.
For every auger flight sampled, the soil must be inspected and any variations recorded by
your field partner.
After samples have been collected from all five auger holes, assess the fullness of the
sample bags.
If necessary, additional auger holes from applicable depths can be collected from anywhere
within the 20 m by 20 m square to fill the bag.
Note this in your observations.
Seal each bag by folding the metal tab and bending the tabs to the front.
Always place the sample bag into a polybag to avoid any sample loss or cross-contamination
during transportation.
Before leaving a soil sample site, both samplers must ensure that all required
observations and notes about the site and the samples are made.
When leaving a site, always check you have all samples and equipment and that you leave
the site as undisturbed as possible.