Remember that Eh and ORP are properties of a half cell normally comprised of a metal surface in an electrolyte, such as soil.  Therefore, measurement of Eh and ORP requires a metal and the values will be dependent upon the metal used.  Measurements can be made with something as simple as a metal nail or rod driven into the soil, some sort of standard half cell (such as a commercial copper/copper sulfate electrode) and a high impedance voltmeter.  Depending upon the resistivity of the soil, the minimum contact area of the reference electrode will vary.  That is why a commercial Cu/CuSO4 electrode would probably work better than a laboratory SCE electrode with it's smaller glass frit electrolyte contact.

Dear Clinton,

There are needle to measure Eh and oxygen sensors in sediments. No brands have in mind right now, but you can measure after mm mm deep. Good Luck!

 Thanks for your help/advice.I have been looking at the literature as suggested. I see various products on the market. I'm looking to install probes at 10 - 20 soil moisture and climate stations across an area of Southern New Zealand. We have a minimum of 2 and up to  10 years continuous soil moisture, soil and air temperature and precipitation at these sites. Idea is to deploy for 12 months or more and integrate into our data logging platform at each site. The question is now one of cost. This will determine how many sites we can install. Carla very interested in the needle sensors. Do you have a brand name. Stephen and Junghong thanks for your advice on reference electrodes and meter types. Regards,  Clint

What is the method for measuring sediment ORP? which brand suggested?

I tried ExStik ORP meter which is good for sediment and does not damage the probe.

I have a YSI (ORP 15A) which costs quite a bit more than the ExStik. Dr Rezai, do you know the type of Electrode the ExStik uses ?

I have to ask YSI about the type of electrode used in the ORP 15A. Thanks

https://www.ysi.com/orp15a

https://www.amazon.com/Extech-RE300-ExStik-ORP-Meter/dp/B000S8UIVA

Which probe (and standard) would you recommend in case of measuring also

Redox/ORP in anaerobic liquid samples or in anaerobic suspension of solids in a liquid?

Epoxy Sure-Flow Combination Redox/ORP Electrodes, Cat. No. 9678BNWP and 967800

Glass Combination Redox/ORP Electrodes, Cat. No. 9778BNWP and 9778SC

Epoxy Refillable ORP/ATC Triode, Cat. No. 9180BNMD and 9180BN

Epoxy Low Maintenance ORP/ATC Triode, Cat. No. 9179BNMD and 9179BN

Try Ex-Stik, its accurate and relatively cheap

Thank you Hamid.

But the Ex-Stik is for liquid samples right? How do you use it in sediments?

Its not for liquid only, I used it for sea sediment for almost a year and if you look at the U Tube, they show that it can be even used for carpets, its quite strong but not so water tight as it is shown.Its price is also affordable.

Dear Clinton,

Check out the redox probe, our latest invention at Ejlskov:

https://www.ejlskov.com/ejlskov-redox-probe-new-tool-to-measure-redox-conditions-in-soil

With it you'll be able to measure redox conditions to a depth of down to 30m, with centimeter resolution.

Sincerely,

/Ivan Vela

Development Coordinator, Ejlskov A/S