Re: Would melted icebergs be the purest water on earth?

Ryan,

I am not an expert on icebergs, but I do know a little about claims for
pure water.  While it is true, snow that fell thousands of years ago are 
free of practically all human conatmination (especially for the snow that 
fell on Antarctica), snow or precipitation of any kind for that matter, is 
not chemically pure.  First, small droplets of water or ice crystals that 
form in the upper atmosphere form around a nucleus.  That means that there 
must be a dust particle for the water to begin condensing around.  This 
dust particle may have been a microcrystal of salt placed in the 
atmosphere when waves sent spray into the air.  It may be a particle of 
ash from a forest fire or from a volcanic eruption.

The water cycle has been in operation for billions of years and 
precipitation has been interacting with atmospheric particulates and 
compounds for all that time.  For instance, all rain is acid rain.  Always 
has been, always will be.  The atmosphere contains aproximately 350 ppm 
CO2.  The meteorological information has demonstrated a steady rise in the 
background CO2 since the industrial revolution started in the 1850's from 
280 ppm, but a good sized volcanic eruption can place millions of tons of 
the gas into the atmosphere in a shrot period of time.  When rain falls 
from the sky, some of the CO2 naturally dissolves in the rain drops, 
making carbonic acid rain with a pH as low as 5.5 (Neutral is 7.0).  
Higher CO2 concentrations lower the pH to the 4.3 to 4.5 range.  This 
excessively low pH is referred to as industrial acid rain.  

I have collected rain from all over the United States (including Hawaii) 
and have measured the electrical conductivity.  This is a measure of the 
charge-carrying ions dissolved in the rain and can be used as an 
indication of the purity of water.  Everything else being equal, the 
closer one is to the sea, the higher the conductivity.  The sea spray 
contributes significant amounts of salt to the rain.  The farther inland, 
the lower the salt content.  Chemically pure water has a conductivity of 
0.055 uS/cm.  Rain water samples are usually in the range of 4 to 10 
uS/cm.  For comparison, the City of Phoenix municipal water has an 
electrical conductivity of between 800 and 1,100 uS/cm. and distilled 
water you buy in the store is in the range of 3 to 5 uS/cm. from the 
dissolved carbon dioxide (CO2) dissolved in it.

Some groundwater that passes over "green sand" has been naturally softened 
by ion exchange.  This is similar to the processes used in your home water 
softener.  Water from these aquifers was deposited underground thousands, 
tens of thousands or more years ago.  Much of it is also free of human 
contamination.  Withe the additional filtering and potential ion exchange, 
this is not a bad source for drinking water.

Do I think melted glacier water is the purest on the Earth?  Absolutely 
not.  Any high school student could prepare better water with a 
distillation apparatus in a simple laboratory.  Homeowners all over the 
world are making water that good under thier kitchen sinks.  Do I think it 
is better than most of the municipal water sources available in the U.S.? 
Probably.  You can get water as chemically pure by simply passing any 
municipal water through a carbon filter and a reverse osmosis unit.  These 
devices remove up to 99% of everything dissolved in the water.  That puts 
it into the good rainwater category, with much more control over the pesky 
trace chemicals left in it.  The carbon filter will remove the organics 
and the chlorine.  

Some people point to the fact that glacier water makes very clear ice and 
cite this fact to support its purity.  Ice primarily is cloudy from 
dissolved air in the water at the time it freezes.  Snow that has formed 
glaciers has had time to exclude the dissolved air from it, thereby making 
crystal clear ice.  Just boil the water before you freeze it for ice cubes 
and you can make crystal clear ice as well.

If all of this sounds like too much human intervention and refining of the 
water, remember, the hydrologic cycle naturally sand filters, biologically 
modifies, and distills all of the water on the surface of the Earth in its 
process of purifying and recycling it.  Chemists have simply standardized 
the final purification of the water.  It can't be too bad, because it is 
this process of water purification that has stopped almost all of the 
waterborne epidemics that took place when people left water purification 
to nature alone.

Melted glacier water sounds good but I think it is playing on the romantic 
side of people's good sense.  Remember, some of the snow that makes up 
glaciers in Alaska and Canada could have easily come in contact with wooly 
mammoths or early migrating hunters.  It never hurts to remember the 
adage, "Don't eat (or drink) yellow snow!"   

Other pollutants have been added by humans, but the Earth weather system 
does a good job adding some of its own.

I hope this helps.

Encyclopedia Britannica, Macropedia, Atmosphere