Tips of the Week
We have worked together with our groundwater monitoring instructors to sum up some environmental technique into tips which we believe you would find useful.
If you or your colleagues have some interesting tips and wish to display on our website with acknowledged to you or your company, we are very happy to do so - please click here.
- Even the best suction pump (like a peristaltic pump) cannot lift water for more than 9, 5 meters (at sea level). You can however, without any problem, take a water sample at -50 m depth. The only condition is that the groundwater table needs to be closer than 9.5 meters below the pump!
- Reduce friction when pumping water through long lengths of tubing (e.g. when pumping with a 25 or 50 m long tubing) by choosing a tube with a larger internal diameter. Flow rate may increase by a factor four when you double the diameter.
- Use benzine to rinse any oil from the probe of an electronic LNAPL or DNAPL detector. Use an additional benzine soaked tissue to clean the tape if it was submerged.
- In addition pH and Redox probes have a diafragm that gets clogged. The internal electrolyte can get poisonned when the probe is exposed to, or even submerged in dirty water. Lengthen the lifetime of these probes by, after rinsing, storing them in absolutely fresh 3 M KCL liquid in an absolutely clean storage bottle.
- Sending a pH, EC, Redox or DO meter to a workshop for calibration is like sending your car to a garage to inflate tyres. Calibration needs to be done prior to every set of important measurements which is at least every day you start working with this equipment!
- Conductivity, pH, DO and Redox measurements are temperature sensitive. Check the temperature probe is working before measurement by holding the probe in your hand and see if the temperature goes up.
- EC calibration liquid, which is an accurate but simple diluted KCl salt solution in not stable for a long time. Funghi may grow in it, the water evaporates which makes it saltier and so on. This will cause calibration error messages! Refresh at least weekly from a spare bottle stored in a cooler.
- A DO measurement is useless when the water has been collected in a beaker or flask, due to air contact. Use a flow through cell + pump to create a constant air-contactless flow of water in which you can accurately measure D.O.; Redox and other parameters.
- You can avoid any risk on cross-contamination between wells by simply renewing the tubing of a pump prior to starting the purging procedure. Use tube with a QA/QC Hallmark and store them in a place which is hydrocarbon free. Generators, petrol cans and motor-powered pumps in your van are very risky!
- Never overfill a Dutch auger, especially in plastic soils (wet clays and loams). Overfilling will cause soil to be squeezed out of the auger body back to the wall of the augered hole! A perfect piston cylinder that will seriously frustrate pulling the auger up!
- If pulling up an auger in a borehole is difficult because of friction (generally caused by overfilling the auger). Lower an empty auger slowly and simultaneously rotate it many times scraping off any soil collected to the wall of the borehole. After this you can proceed drilling without this friction. Preferably use a course sand auger for this since cuttings won't drop out.
- Moist sticky soils can be hard to remove from an auger body. If tapping on a wooden plate does not work anymore try the following: After lifting the filled auger 10 cm or so lower it again and push it down with your full body weight while making only a 20°-30° clockwise twist (as if you restart augering for a second). The sample will have moved upward in the auger body. A little tapping will empty the auger!
- Volatiles tend to disappear from a soil sample quickly. Take these samples at least at a certain depth (e.g. -1 m) and use special zero-headspace non-lined coring tubes. Wrap the tubes in aluminium foil to zero all chances. In the lab sub-samples are taken from both ends and analysed
- Stony soils that should be analysed on volatiles should be collected in a completely filled glass jar (and rapidly extracted in the lab) or be collected in a vial with 50% soil and 50% lab-grade methanol.
- So called inertia (or foot-valve) pumps are the only solution for purging and sampling very narrow wells with a water table deeper than 9.5 m. There even exists a 9 mm inertia pump that is able to pump some 1 l/min in a mini- or multi-well with an access tube of only 10 mm.
- Leave inertia (or foot-valve) pumps overnight in a detergent after use. Rinse it the day later with ample water and fit a new tube to have a "new" contaminant free pump.
- Use an in-line filter for your groundwater when sampling for dissolved (trace) metals. This prevents over exaggeration of the concentration of (trace) metals, due to metals which where adsorbed to clay, sand and organic particles.
- When using a 0.45 micron filter to remove soil particles from well water for later analyses on metals make sure to have no air collected on the membrane. Fully de-aerate the tubing coming out of the well; stick on a filter and keep the outlet upward while activating the pump.
- There is no set time limit for a multi-meter calibration. An instrument could be out of calibration for many reasons, such as shocks to the instrument and quality of your samples. You should check the calibration against fresh standards before starting your measurement. If the result is materially different you should recalibrate.
