OK Tom this is what i am alluding to. Are there natural waterways that have high KH values say 6 degrees and above , but the pH below 7.0 . I know this seems to be a contraindication but is
it possible? Whould such a body of water have a higher concentration of CO2?
Tom let's have a body of water. If i artificially load the water with carbonates/bicarbonates and then reduce the pH by adding an organic acid like acetic or citric acid, am i then stimulating an in vitro biogenic decalcification model that will lead to an intrinsic build up of CO2 albeit with high TDS??
The Ichetucknee river had a pH of 6.7 and a KH of 6, about 25ppm, that was in the middle of the afternoon so some plant uptake should be factored in.
Plenty of ground water is loaded with CO2.
That's how caves are formed.
The acidic CO2 rich water dissolves the limestone.
As rain falls and percolates through the soil, the organic matter is decomposed in the soil, this uses up O2 and gives off CO2 by the bacteria in the soil.
The CO2 is absorbed into the rain water and descends into the water table below.
There is nowhere for the CO2 rich water to off gas underground, so it builds up.
Where there are springs, the water coming out is typically loaded with CO2 and plant growth is vigorous and stable for well over hundreds of years(500 years at least in Florida based on observations from Spanish monks in 1500's, even longer based on radio labeling and pollen and other indicators of dating in Paleolimnology).
In answer to the 2# question, the answer is a resounding "no".
CO2 is also an acid, ask yourself why that does not work also?
Because the acids you listed are "weak" acids.
If you used a "strong" acid, then the answer is yes.
H2SO4, HCL, HNO3, etc, nasty stuff, this will attack the bicarbonate and release CO2.
It'll also soften the KH
It's virtually always a much wiser idea to use RO if you want less KH than strong acids. I've had folks carry on about having it for their pool etc and how easy they claim it is on line..........but I've done it also, it's not this easy thing, the flumes are noxious and the acid is nasty stuff and many burn the heck out of themselves.
I asked this same person that claimed to know what they where doing whether or not you should add acid to water or water to acid to diluted.
They gave the wrong answer.
That told me either they are not really doing it and just wanting to make a stink and haggle, a common thing on the web really, or that they forget even though they claim to have been doing it.
I use long gloves, a fume hood, apron etc.
Look, bottom line, if you want more CO2 in the water, it is very simple: add more CO2 gas. Plants want CO2, so provide that.
Changing pH/KH etc does not add CO2.
Adding CO2 adds CO2.
It's much simpler than you are trying to over think it, don't fret, many folks do and go through this same thought process. But then they realize the simple aspect, if you want more CO2, add more CO2, it's much simpler than any other method.