How long does it take a river to break down gold-mine cyanide?

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I tried to research this but could only find that cyanide breaks down in water. What would happen to the cyanide if it leaked into a natural flowing river? Does it still break down? Would it kill all the wildlife before it broke down?

A gold mine has leaked cyanide ponds into a river and I want to understand the effects that will now take place. If there is a more appropriate thread for this question please let me know! Thanks 🙂

In: Chemistry

2 Answers

Anonymous 0 Comments

It’s hard to give an exact answer because it will depend on initial conditions.

Cyanide chemistry is fairly complicated and it is removed from the water through several pathways:

Evaporation as hydrogen cyanide gas will pull much of it out within a few days – this is a function of temperature and water turbulence, hotter and more mobile water will discharge it faster than cold, still slag ponds.

Reaction with other chemicals will degrade some of it into insoluble metal complexes and sulfates. Those can persist for a long time in the soil, with varying degrees of harmfulness.

Some is consumed and metabolized by microbes. Cyanide may be incredibly toxic to us fancy multicellular oxygen-breathers, but primordial soil-dwelling bacteria that pre-date us all know how to use it for metabolic processes. Some environmental cyanide is consumed and converted into less-harmful chemicals by these bacteria.

Whether it causes a mass die off of wildlife before it’s removed from the system will depend on how high the initial concentrations are and how quickly it disperses downstream. Fish will tolerate a low dose for a while, but they won’t tolerate a huge dump.

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