In order to render mine water a whole lot less toxic, the key could be letting a fungus bloom. Some fungi produce a superoxide when they grow, which is instrumental in cleaning up polluting metals. This superoxide reacts with locally available Magnesium(II), and is oxidized to Mn(III) or Mn(IV), which in turn suck up the likes of arsenic, cadmium, and cobalt.
This reaction isn't news, but what is is how and when it takes place. Up until now, mines would often try and cause this reaction to happen more by dumping foods for the fungus, like straw, and hoping that would stimulate the reaction. A new study in PNAS has shown what really causes the reaction to occur, and it's all about breeding.
Stilbella aciculosa only produces the superoxide during cell differentiation, when it forms asexual reproductive structures. In other words, when it's making spores. It uses the superoxide as a cellular signal to moderate differentiation, its love affair with Mn(II) is potentially just a (good for us) side effect.
So if it's during blooming that the superoxide is created, how do we get the fungus to do that more often? Unfortunately, that's a very good question that we don't really know the answer to. But now we're a step closer along the way.
Photo courtesy of Colleen Hansel