Backyard Aquaponics
A place to discuss aquaponics

1. What is the ph of normal rain?
Why is it not always neutral even in unpolluted places?
2. Rain is part of the water cycle. In which part of that cycle does a change in ph occur?
3.How large a range of ph is found in rain in different parts of the world and what causes this?
4.How is pollution related to this range?
5. What are the many problems caused by acid rain in the world and what are we trying to do about it?

Hi Faye.
My understanding is that ph of rain can change as it passes from the clouds to the ground, ie as rain. I think this is bc the rainwater can absorb some CO2 as it falls thru the atmosphere. This would tend to make the rain slightly more acid than neutral.
Thinking along these lines, trees are carbon sinks. It would be reasonable to expect less CO2 in the atmosphere above forests, so perhaps that rain would be slightly more alkaline.
I guess the level of CO2 in the atmosphere is the limiting factor on the potential acidity of rain. The higher the CO2 the more potentially acid the rain.

CO2 and heavy metals are present in ever increasing volumes in our atmosphere. It is only natural then that concentrations of these things are becoming higher in our rainfall. Think deforestation, melting ice caps, the end of the world...........

I am a novice and would appreciate someone with the relevant science background putting some hard answers in here. I have just been thinking aloud and could be totally off the track. I just wanted to bang a tentative theory up here for people with genuine knowledge to shoot holes in and expand upon further.

Many environmental discharges from industrial stacks contain high levels of Sulphur Dioxide.... with water this forms a weak sulphuric acid....

Or Nitrous Oxides ... with water this forms a weak nitric acid....

Acid rain... see wiki

http://en.wikipedia.org/wiki/Acid_rain

Water is the most complicated subject on the planet after maybe light and women.
The closer you look the more incredible it all becomes.
But ya pH is sorta a triad thing... co2 in ratio with kH and gH... all existing in a sort of complete fluid ballance...
Then you throw all the random chemicals mankind produces, and all the naturally occuring ones that water runs over/through and in.
Water also picks up charges, transforms into polymorphs and is syphoned off by plants while they trap sunlight energy as sugars....
It's all very interesting really.

SO2 is the worst of it. You get it naturally from volcanoes, and as a by-product of some processes. The worst cases are metal extraction processes that burn sulphur as part of a furnace for both the heat and chemical reaction. I have worked at both Kalgoorlie Nickel Smelter and Olympic Dam (Roxby Downs) that do this. Both require you to carry around a gas mask at all times, and have SO2 detection. When the siren goes off, don the mask before the SO2 reacts with water in your lungs and burns.
My parents grew up in Kal, and the rain that stings was not uncommon. They may have cleaned up there act in the last few decades.

i believe that heavy electrical storms can also cause a drop in rain ph due to some NOx being formed by the discharge through air (78%N2 , 21%O2)

I THINK!

Do some research on russia and surrounds.
In some smelting towns... the earth is dead. Not just the forests, grass and animals... but the very bacteria and fungi in the soil are gone.
You don't go in the rain....
couldn't find this great link, doh. we are talking seriously wacked out pH acid rain

Here in the US, and I am sure it is the same through out the world, the problem with acid rain is not the point where the rain falls or the H2O in the clouds are from. We have seen that the emissions from coal burning power plants, metal smelting operations, and even large metropolitan areas can spread over a larger area due to the wind patterns. Here in the Mid West we have problems with air pollution comming out of the West and Southwest. (Fortunately, the Rocky Mountains tend to act as a natural buffer and slows down the spread and amount we get.) The Eastern part of the US has problems from the emissions in the Mid West and of course the East ends up with thier air pollution going out over the Atlantic.
As far as the relevence of forest in the equation is two fold; the forest is involved in the transpiration of H2O back into the atmosphere, along with an absorption of CO2 from the atmosphere. The net effect is that trees remove gasses from the air, while returning water back. Because of this, if the air is highly toxic trees, and other vegetation will die off. However, as a side note, an increased level of CO2, without acidifing chemicals, actually results in a more rapid rate of plant growth, and therefore a higher amount of transpiration of water back into the atmosphere.