Samples for geochemistry are taken every 10th of the month according to a protocol defined by SNO Hybam since its creation. The observers (the people in charge of collecting the samples) are trained when the network is set up, and the quality of the sampling is regularly monitored by visiting the sampling sites and checking the collection and filtration protocols with the observers.
We send sampling/filtration equipment for 1 year to each observer. The filtration kit is packaged in a ziploc bag for 1 month and contains :
1 polystyrene filtration unit with a 0.22µm polyvinylidene fluoride (PVDF) filter
- 1 60mL “trace” bottle acidified with 5 drops of bidistilled HNO3
- 1 125mL “major” bottle
- 1 24mL “carbon” glass tube acidified with 60-70 µL ultrapure H3PO4
- Parafilm
- Aluminium foil
- Vinyl glove
The observer is also equipped with 1 x 500mL sampling bottle, 1 x hand pump or 1 x electric pump, a pH meter and a conductivity meter.
- Samples should be taken in the middle of the river wherever possible.
- The boat’s engine should be stopped and you should stand at the front of the boat against the current to avoid contamination of the collected water by petrol or engine fumes.
- To avoid mixing with surface water, open the bottles underwater and wash them 3 times with river water. Discard the rinsing water on the other side of the boat.
- Take a sample from approximately 30 cm below the surface of the water. Fill the sampling bottle to the brim and close the bottle underwate
- Measure the pH, the conductivity and temperature of the river using the pen pH / conductivity meter by immersing the instrument directly in the river.
- Place the sampling bottle in the cooler to keep the sample in the best possible conditions until filtration.
- Prepare the filtration area so that it is clean and well organised, wash your hands with soap (wear vinyl gloves). Leave the bottle on the table so that the water can start decanting.
- Connect the hand pump to the filtration unit. Pour 150 ml of water into the upper part of the Filtration system and filter it completely. When all the water has been filtered release the vacuum, remove the pump and discard the 150 ml of filtered water.
- Reconnect the pump. Put another 150 ml of water into the top of the filtration system and filter completely. Release the vacuum and remove the pump. With the filtered water, fill the glass tube marked “carbon” to the brim without air bubbles and put the rest of the water into the 125mL bottle marked “major”.
- Reconnect the pump. Repeat the operation, pouring in 100ml of water. Fill the 60ml bottle marked “traces” with the filtered water.
- Mix the remaining water in the bottle and filter all the water, discarding the filtered water.
- Write the date and river reference at the time of measurement on the labels, and apply transparent adhesive paper to the label. Wrap the glass tube marked “carbon” in aluminium foil. Put parafilm around all the bottle caps.