Climate change may be the hottest environmental issue splashed across the front pages of newspapers these days, but flip back a couple of decades and you will see widespread concern over a phenomenon called acid rain. Acid rain is any precipitation (rain, snow, fog, etc.) that has an unusually low pH. But, what is a low pH and why is this a problem?
The pH is a measure of the amount of dissolved positively charged hydrogen ions (H+) in a substance. pH is measured on a scale from 0 (lots of H+) to 14 (not many H+). Normal rain has a pH of 5.6, and acid rain 1-5. If you put vinegar on your French fries, you are eating something with a pH of 2-2.5. If you can eat at a low pH without any problems, acid rain can't be that bad right?
Did you know? The Canadian Government didn’t recognize the existence of acid rain until 1979, despite it first being observed in the 1850s.
Wrong! While it won’t melt your umbrella, it can disturb forest growth, kill fish and aquatic plants and can harm buildings too. Acid rain can ruin the paint job on your car, or the stone and metal of famous monuments.
Did you know? Acid rain doesn’t respect national boundaries. Efforts to minimize acid rain require cooperation between neighbouring countries.
So where does acid rain come from? Burning fossil fuels, like gasoline in cars or coal in power plants, releases many gases, including sulphur dioxide (SO2) and nitric oxides (NOx). Natural sources of these gases exist too, like volcanoes.
Did You Know?
China is the world’s largest user of coal.
When these gases combine with water and oxygen in the atmosphere, they produce sulphuric and nitric acids. The acids are then pulled out of air by falling rain or snow (wet deposition) or they can fall down to earth on their own (dry deposition).
While we are working the problem, we’re not out of the woods yet. It will take reduced dependence on fossil fuels to stop acid rain. In the meantime, it’s not all bad news. Some studies suggest that acid rain reduces methane productions in wetlands. Reducing this greenhouse gas could help reduce climate change.