We all hear and preach this, but my question is, what about in nature? The silt/ mud can be pretty deep. Why isn't it so catastrophic in nature?
I keep asking those Power sand zealots, the heater cable zealots the same things...............
Never have ever gotten a straight answer.
In answer to your specific question, it very well can be a huge issue, or not.
The main thing driving the anaerobic nature in sediment is carbon, the reduced organic kind, you know........carbs, fats etc, same stuff we eat for energy.
Bacteria consume is so fast, the O2 is depleted.
So this is the central cycle in sediments that are flooded. There's a massive amount of research and peer reviewed articles about this single topic.
If you have no organic matter, the sediment can be 10 ft thick, the O2 will be the same ............It's a biology question, not an engineering question. That's marketing gets the folks who do not know any better(zealots and belief).
You have to have a certain amount of redox to get anaerobic conditions, they just do not appear out of the thin air. These are defined by bacteria and organic carbon.
Then............this is not the rest of the story............we have plants.
They add a lot of O2 to the root zones and they have all adapted to well to flooded soils..............they use a few methods, but most use channels to pump O2 to these sediments where they naturally grow.
Again, why folks skip this part(plant's effect), and focus soley on engineering is beyond me. Insane.
Some aquatic plants can't grow at all in anoxic sediment,
Okay, you brought this up, name one aquatic plant, that cannot grow in such a sediment? Entertain me.
I've only had anaerobic sediment(black H2S) pockets where a rotting Aponogeton bulb was placed, or due to no CO2/really really poor plant health (plants, melting, slowly dying etc)
Bubbles alone could be and are also from aerobic sediments, generally CO2. Just like us.
Bubbles alone do not imply anaerobic conditions.
Plants and good growth, imply good sediment O2 supply, regardless of the particle size, this pathway is never resistricted since it's inside the plant, not defined by the physical characters of the grain sizes.
If you do not look at the plant's role here and their influence, you miss a huge part of the ........cough cough...........planted
Be careful in how you look at this. This stuff is not opinion, it's very well studied and they have many text books and research papers on wetland soils with and without plants.
Cables and powersand ARE NOT part of any natural system.
So they are not studied, however, the general models and relationships used for wetland soils are very well studied.
R. Reddy's latest book(2008) is certainly the best text on the subject as it addresses plants, wetland anaerobic soils, cycling of each nutrient, etc.
If you want to learn about sediments and how they interact with soil, then you should read this book if you wish to learn more. Then you also will know how to test the system to see if the effects are significant and how to do this for aquatic plant tanks as well.