 Incredible, Christoph. Almost spooky that we find this phenomenon of the white aluminum precipitates now in nature. This is after we made careful experiments in the lab and we were predicting this since decades, but we were not able to find it. Yes, the reason why these white aluminum precipitates are so rare in nature is that many factors have to play together that these precipitates can actually form here. And they want to do now is we will walk upstream to the source of this little stream and there we can actually see and discuss all the different ingredients that are required for the formation of these white aluminum sulfide precipitates down here. Now at the very end of the Laviroun Valley at the origin of the stream called Ova Laviroun and the water now is very clear. We don't see any white precipitates anymore and with this electrode I can measure the pH value and it yields value of about 4.4. This is quite a low pH so we have quite acidic conditions here. Normally drinking water has a pH between 6 and 8.5 so you see quite below that value here. And from chemical analysis we know that we have quite elevated aluminum concentration in this stream here and also the sulfate concentration is quite high. In addition these chemical analysis also show that sometimes you have quite elevated arsenic concentration that may reach values about twice the drinking water threshold value. To understand why the pH is so low we need to have a look at the rocks here in the area and it turns out that these rocks are pyrite bearing. Pyrite is an iron sulfide mineral like this very nice piece here. This doesn't come from here it's from a big iron sulfide mine but here you see the nice pyrite crystals. In the rocks here the pyrite grains are very small and they are finally dispersed in the rocks but when oxygen saturated water gets in contact with the pyrite the sulfuric acid is produced so very acidic conditions are produced and these acid conditions in a second step then dissolve a lot of the aluminum from the host here. And the high sulfate concentration are due to the oxidation of the pyrite. So the oxidation of pyrite produces sulfuric acid but sulfuric acid normally in the underground is not at really high concentrations. Yes Gary we are absolutely right there is still one parameter missing for fully understanding our phenomenon and to better understand it we have to go to this little hole here we prepared a couple of minutes ago. And here you see that we have kind of water saturated condition in a shallow depth here so we have a little aquifer here despite that we are at an altitude above 2800 meters above sea level. And the reason for these water saturated condition is first because the topography is quite flat for a mountainous area here in second. We have a permafrost area up here and the ice in that permafrost melts quite slowly drop by drop and these drops then accumulate to this little aquifer. And groundwater flow in this aquifer is rather slow which means there is a high contact time between the water the oxygenated water and the pyrite. So there is enough time to produce a lot of sulfuric acid being able to dissolve a lot of the rock and creating these high aluminum concentrations. On its way down the hill the pH of our acidic stream has increased to about 5.0. So the tributary behind me has a pH significantly above 6 which means at this conflict point the acidic stream is neutralized and the pH increases to a pH of about 5.5. And this neutralization is the last important factor for the precipitation of the white aluminum sulfur precipitates. The reason is that these precipitates as an extremely pH dependent solubility and due to this neutralization they became super saturated and they form eventually and this is what we see here in the stream bed. Ok so we are now back at the same spot as we have been this morning and from our little journey to the origin of this acidic stream we have now learned that several factors have to play together to enable the formation of this white aluminum sulfate precipitates. First we need pyro bearing rock. Second we need slow moving groundwater. This enables the solution of the rock of the aluminum. And fourth we need the neutralization by a neutral tributary which increases the pH and lowers the solubility of these white aluminum sulfate precipitates. Well so far so good. What happens to the arsenic? That's indeed an excellent question Gary from our chemical analysis. We know that we have quite an elevated arsenic content in these white precipitates. So and this means that the toxic arsenic that might get dissolved near the origin of the stream is then co-precipitated together with these white aluminum sulfate precipitates. And in analogy the same happens to iron you might have seen the slightly yellow precipitates and this is from the co-precipitation of iron together with the aluminum sulfate precipitates. This wonderful example shows us that sometimes a hunter is needed to bring us environmental scientists on the right track. The publication we had a year ago brought us additional 20 messages from other sites in the alpine areas and now we are challenged to prove whether the appearance of this phenomenon is also related to loss of permafrost.