Hi Mike,

Before to give my opinion, As I deduced that your subject related to determining water quality in terms of plants health (as some of plant macro and micro nutritions; N,P,K and Fe) right? Actually, in my opinion also you may study water quality for aquatic ecosystem (Measuring parameters: DO, NH4, NO3, Ph, Temp., EC, TDS etc.) smiltaneously. And the study you want to work on, it will be better that getting sample each month in vegetation period in which time plants physiologically active. In north hemisphere, vegetation period mostly covers: march to October. If your region has shorter period then you may get to sample twice or more per month. It doesnt meet your demand about question but I would say one of the my little  opinion:)

Good luck in your study.

Hi Mike

This is another communication platform to test :-)

We are likely going to install some of these in the marsh systems along the Scheldt. I haven't tested them myself, as we don't have them, but we heard some good references.

http://www.unityscientific.com/products/chem-analyzers-and-sample-prep/wiz-probe.asp

Only dissolved N and P though... but on request they also have other parameters including dissolved Fe and dissolved Si...

Don't know about K...

Hi Mike

I don't know about the precise measurement or chemistry, but I do a lot of remote measurement of various variables (temperature, humidity, light levels etc) cheaply using android phones.  If you can get your environmental variable into a voltage, its then quite simple to get it via the phone to a central server.

Regards

Russ

I agree with Russell, if you can, try to get your data via telemetry. If you are going out to download only once a month you risk large data gaps in case of instrument failure. When you get it telemetrically, you immediately notice when a sensor/station is not working and can react quickly.

Russell, we would love to learn more about how you utilize android phones for telemetric purposes!

Thanks very much to all for replies - the Okavango is rather large and we really don't have any telemetry networks that cover the area in question - as Eric Struyf will appreciate ;-).

Sorry, I guess that I wasn't very clear about the actual problem - which is really one of finding an instrument with VERY low limitis of detection - the data logging part I think we can handle.

Eric, that WTZ instrument you gave the link to looks great. Let me know how it goes on the Scheldt. If we can get N & P that should at least give us an idea when ag pollution kicks in in the upstream part of the basin. Now I need to start looking for some money....

All the best and cheers

Mike

Hi, Mike.

We've had that problem forever in the very oligotrophic waters in the south-western Cape. We have used (and Oceanography at UCT still does use) an autoanalyser that takes very small quantities of sample and really does have low detection limits for all the common dissolved nutrients. You can probably get details from Howard Waldron ([email protected])  or ask him who to talk to. Unfortunately I don't use the machine myself and I can't remember the name of the manufacturers.  

It's not cheap but it's the best we have been able to find. 

Good luck. Analysing really pure waters is a frustrating game! The only thing that is worse is analysing highly saline waters (and I know, having attempted both).

All the best,

Jenny

Hi Jenny - good to hear from you! I gave your name to Heather McGinness from CSIRO  who's interested in hydrology-ecology links in the Murray-Darling basin - hope you don't mind - she might get in touch... Anyway, this is a bit off course - Thanks for the potential WQ contact, I'll shoot him an e-mail.

Cheers

Mike

Colleagues used an on-line analyser produced by Systea http://www.systea.it/ deployed in northern Tasmania. It was serviced monthly and after some teething problems performed reasonably well for a remotely deployed instrument. It had the required detection limits for Ammonia-N, TN (uv digestion), TP and reactive P - it was hard to find instruments with low enough dls, I think the TN measurement may have had instrumental problems. It did however use mains power for the instrument and pumped sampling loop and had telemetry  direct to the web via the gsm network. Other power & data options may be available. There are publications by Ulrike Bende-Michl describing the work.

Hi Warren - Thanks for the info. Indeed, mains power is a bit of a hurdle for us in many locations, but we can probably set up something with solar... Thanks too for the suggestions for literature from Ulrike B-M - I'll track them down!

Cheers

Mike