In general Salicyate methods are worse at lower detection limits.
So that level of detection seems plausible at 0.1ppm.
Still, I'd want more as a researcher when doing this set up.
The Bioenzyme method is neat, but not practical.
Nessler's is phased out due to Hg issues.
So phenate seems pretty good.
I have a Hach DR 2800 and phenate here at home.
This can target pretty low NH4, but still not as a good as enrichment with N15 and it's smaller than a Cyclotron
A question that's dogged me is "who" gets what for each NH4 added to the system. How much goes to bacteria, periphyton and algae spores, adult algae and plants.
I could test many plant species within a community or ecosystem all at once and discriminate.
Reddy had a nice meter cube wetland soil sediment flooded system at his lab that was suited well for this. Adding enriched NH4 and NO3 would be ideal, but taking over it for a few months would be tough, but I was studying algae at the time
The mass spect was pretty good but they had it set for natural backgound levels, not enrichment studies so I was sort of talked out of it by the lab guys. Bastards
I could have used another spect, but they are squirrley.
I think the bottom line is much more basal. A simple test, something aquarist can and do. By already adding NH4 only, then trying NO3 only, then using both at once at say low NH4 and higher NO3, you can see if you can note a growth difference or not.
While accurate dry weight measures are good and certainly wise in research etc, for most aquarist, if they cannot see a difference visually in rates of growth they can definitively say is due to the treatment, they really will never be convinced.
I'm very much Socratic in this respect, I'd rather folks try it themselves, see what they think and can conclude. They need to ask the questions, then go about setting up a test to determine if the hypothesis may or may not hold true, or, if it remains inconclusive.
Simply thinking about what we can do, rather than what we cannot, and all the labor and resources involved, can answer most of the questions aquatic plant hobbyists may have.
Then the person convinces themselves, not merely taking my word for it.
I hate that when they do that. Then they can argue for it (or against it). If you have not done it, then you cannot talk much based on experience and observational data and test will only get you so far. Manipulative test can be done here fairly easily and are much more powerful.
But......Many do not want to induce algae, risk fish losses, to answer a question about what might cause algae blooms or if there's really that large of difference between N sources. I do, and I can get rid of algae and start anew easily. Most cannot. They get a tank stable and the last thing they wanna do is mess with it.
Diana's notions about Allelopathy have been falsified easily with respect to algae control. All it takes is a very simple test as a control, often used in terrestrial systems, add activated carbon to the filter at high flows and lots of Carbon vs tank volume.
Ho: algae will bloom
Ha: algae will not bloom
Algae did not bloom in non CO2 nor a CO2 enriched tanks.
Same type of thing with adding PO4, NO3, Fe etc to excess levels in both types of aquariums(CO2 or not, side note: Excel kills algae and bacteria directly, so it's not the best carbon source to consider).
I did not need to do a large scale study to figure out most of the relationships in plant, algae and fish interactions and interdependencies.
What was not considered nearly as much was why plant- plant allelopathic issues where not considered with the same zeal. These are common in terrestrial systems and AC is the control for those systems as well.
If it's dramatically significant enough to see it after a few months, then the results tend to be fairly strong. More subtle relationships are harder to differentiate, but fewer folks will see the same things also. Why put effort into something that does not yield good returns for the effort and the risk? More than Plant Biology, a lot of it is human sociology/behavior and common sense logic.
Adding CO2 gas vs not is a dramatic increase.
Adding PO4 to a limited tank is dramatic.
Adding N to an N limited tank is a dramatic increase, same for adding K+ and Mg.
Traces are more subtle, but still there.
Light is huge, the largest factor.
CO2 next and then on down the line for the nutrients.
Light drives the CO2 uptake which drives N which drives K+, PO4 and so on down the line.
Adding fish to the tank adds a fair amount of continuous low level NH4, ideal for fish tolerances and preventing algae and adding a source of cationic N.
I've never noted that much difference in health or growth however in Fish or non fish planted tanks after many years. Still, that is the typical case for most aquarist: fish + KNO3 dosing or a sediment nutrient source + fish.
FYI, plants can and do take up various amnio acids as well, then the N sources are no longer toxic and already usable. Eg Glycine.........
I detailed out a Nitrogen article here in the BarrReport about 3 years ago now, I addressed the adaptation issue with NO3 and various transporters in plants.
Also, the strong covariance between CO2 and Nitrogen in submersed aquatic plant growth and health.
Overall, most folks in the field know aquatic plants are opportunistic, they will take whatever form is around and wherever is might be(sediment of the water column, internally, organic vs inorganic) and grow like a weed.
They really do not seem to be that picky.
Regards,
Tom Barr