What is the situation that the cave water surface is covered with dust?

The ash on the surface of the cave may have the following reasons:

1. A large amount of lime slag will be produced in the process of limestone dissolution inside the cave, which will enter the water with the water flow and form white ash on the water surface.

2. Water may contain high hardness. When the concentration of calcium and magnesium ions in water is too high, calcium carbonate, magnesium carbonate and other substances will be generated, which will precipitate in water to form gray substances.

There may be creatures in the cave, such as algae and bacteria. These creatures will reproduce in the water and produce substances similar to ashes.

4. Weather problem: On cloudy or rainy days, the air humidity in the cave increases, resulting in gray matter.

I hope the above information is helpful to you.