EGEE 101
Energy and the Environment

Where's the Problem? and pH issues

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Map showing the west and south of the United States has less acidic rain than the northeast.
The natural pH of rain is slightly acidic. But clearly, there is an issue with increased acidity in the northeast of the United States due to the high population and industry concentration. The good news is that the acid rain problem has been much reduced by environmental legislation.
Credit: EPA

Much of Europe has been impacted by acid deposition, the famous Black forest has been severely hit and many lakes in Sweden no longer hold any fish. Europe is also a special case as this is where the industrial revolution started (also lots of high S-coal) and so it should be no surprise that the impacts have been felt there. The international aspect of pollution is also a major issue. Pollutants from the UK (SO2 & NOx) drift on the winds and pollute Sweden. Thus, even if you clean up your own backyard you are not tackling the issue of your neighbor's trash blowing into yours.

Here in the US, it is the Northeast that is suffering the most from the impact of acid deposition. Why?

  • The population is high in the NE
  • Coal was the major utility fuel (and still has a significant contribution)
  • Industrialization is heavier in the NE
  • Weather patterns

pH

So how do we measure the acidity of the rain? We use a pH meter and the pH scale to determine how acidic (or its opposite - alkaline) the water is.

Do you think you could put these relatively common household chemicals and bodily fluids into the correct order?

  • Ammonia cleaning solution (NH3 based)
  • Vinegar (carboxylic acid HCO3)
  • Urine
  • Clorox (cleaning solution, chlorine based)
  • Sulphuric Acid (H2SO4)
  • Nitric Acid (HNO3)
The pH scale
The pH Scale
Credit: USGS

Looking at this pH scale, can you tell what pH actually is?

Pregnancy tests are based primarily on pH readings (peeing on a stick)- a woman's urine changes pH when she is pregnant. This is actually old technology that has been rediscovered (modern tests now detect hormones.)

So what is the pH of pure rain?

Rain is naturally slightly acidic as it can absorb CO2 from the atmosphere which alters the ionic chemistry of the water. Thus, to be acidic, the rain (or snow, or............) must be below (more acidic) 5.3 on the pH scale.