Acid Rain (Some Stay Dry While Others Feel the Pain)
Do you remember in high school when there was a special closet in the science lab where the teacher stored sulphuric acid? That’s because sulphuric acid is bad. If you were a supervillain, you might think up some evil scheme to put sulphuric acid into rain and terrorize the earth. Oh wait - that already happened in real life. Today we’re learning about the basics and history of acid rain, and why it both is and isn’t as terrible as I just made it sound.
First off, you need to know that acid rain is NOT pure acid falling from the sky. Instead, it’s any type of precipitation including snow, hail, and fog, that is mixed with acidic particles like sulphuric or nitric acid. These two components occur in the atmosphere when sulfur and nitrogen oxides, which scientists call SOx and NOx for short (pronounced “socks” and “knocks”), react with water, oxygen, and other chemicals to form acid. These acids then get mixed into precipitation and fall back down to earth’s surface. SOx and NOx get into the air almost entirely from industrial sources like electricity production and the transportation sector. Some SOx and NOx comes from volcanoes, but the overwhelming majority comes from the burning of fossil fuels. Normal rain is already slightly acidic, coming in at about 5.6 on the pH scale. Acid rain is more acidic than usual and has a pH between 4.2 and 4.4, with the most acidic rain occurring in industrial areas.
Some environments can bounce back easily from a little acid rain. For example, limestone makes a lot of soils slightly basic, so it can help balance out some acid rain and keeps things from getting too acidic. There are also bacteria in lakes that can help neutralize acid from rain and prevent the lake from acidifying quickly. On the other hand, there are some very important environments that can be devastated by acid rain, like the Rocky Mountains where there is no limestone in the soil, as well as forests and lakes around the world. Even statues and stone buildings get eaten away by acid rain. A history teacher once told me that the effects of acid rain were first noticed on an archaeological site in Greece when famous statues began eroding. While I can’t find any evidence that this exact fact is true, it helped illustrate the destructive power of acid rain for me.
When acid rain impacts a local environment, not all plants and animals are good at adapting. In lakes and rivers, more acidic water draws out more aluminum from surrounding soil and makes the water toxic to small animals like clams and crayfish. The effects then move up the food chain, because predators of these affected fish now don’t have enough food. When animals don’t have enough food, they have a hard time reproducing. Now the animals that eat them are short on food too, and the effects keep moving up one step at a time. In forests, acid in the rain or fog harms tree leaves, but it also changes the chemical composition of soil and makes it hard for trees to slurp up water. When ecosystems are weakened like this, diseases and temperature fluctuations become much bigger problems. You can think of a weakened ecosystem like a weakened immune system - even simple problems like catching a cold, or an early freeze, now have more devastating effects.
Acid rain and its effects first caught the attention of scientists in 1963, and 27 years later the Clean Air Act was passed in America. The 1990 Clean Air Act and subsequent environmental regulations have helped curb acid rain and placed restrictions on SOx and NOx emissions. Agreements with our neighboring countries have also helped reduce the problem of acid rain in America. However, acid rain is still a big problem in some parts of the world and may even be on the rise in Asia, especially in Eastern Asian ecosystems where the soil continues to receive more acid than it can naturally buffer. Some countries like China are implementing restrictions on SOx emissions, though levels continue to rise in other countries including India.
Even though the first American legislation having to do with Acid Rain was passed about 30 years ago, the environment is still trying to recover. Just as some species are more susceptible to acid rain, some species take longer to recover. Federal regulations have resulted in significant drops in SOx and NOx levels. And while environmental recovery is certainly encouraging, some are worried about the prospect of relaxing EPA standards and taking a step backwards. The northeastern US would be most threatened by lax regulation because of the high level of industry (and potential pollution) there; if this concerns you, consider writing a letter expressing yourself to your elected officials.
The air pollution that leads to acid rain has effects that reach beyond the environment. Several new studies have linked higher air pollution to higher rates of mental illnesses like depression, and acid precipitation and dust threaten historically and culturally significant works of art. In this way, acid rain is like many other problems facing the environment: advocates say that we need more regulation, corporations want regulators out of their hair, and in the meantime the environmental effects leak into aspects of social life and culture. When we zoom out from the specific topic of acid rain to the broad topic of climate change, acid rain is not at the top of my personal list of concerns. I feel that emissions standards should be strengthened, but the fact that there is already a regulatory framework in place takes a lot of pressure off of this problem in my eyes. Just like with ozone depletion, the world has already taken important steps to combat this widely known problem.
As with every topic in science, the details of acid rain can get a little complicated. I’ve distilled what I see as the basics here. Are you left with any questions? Did you see an article you’d like me to break down? Feel free to comment here or hop into the discussions in the Troop 7B Facebook group.
Here are the sources I consulted for this article. Feel free to check them out for more information on acid rain!
https://www.nationalgeographic.com/environment/global-warming/acid-rain/#close
https://www.epa.gov/acidrain/what-acid-rain
http://www.bbc.com/future/story/20190823-can-lessons-from-acid-rain-help-stop-climate-change
https://www.sciencedirect.com/science/article/pii/S1352231016305374
