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What Are the Worst US Cities for Acid Rain?

September 4, 2020

We've made progress on acid rain. That's a very good thing because in the 1980s, the damage was taking a toll. In the Adirondacks alone, acid rain caused the fish to die in a quarter of all lakes, and one-third of all red spruce trees were killed. Luckily, we changed course.

Last year, the recovery from acid rain reached another milestone. Trout were discovered in an Adirondack lake after being absent for 32 years. 

Despite the progress, there are still some concentrations of acid rain in the country. Let's look at the changing geography of acid rain and what type of damage it causes.

What Is Acid Rain?

Let's start with the basics to get a better understanding of the problem. 

Acid rain is a bit of a slang term that deals with a wider ecological cycle. It's not just a water problem, and it can easily move across state lines and even country borders. 

It starts with air quality issues. The major problematic gases are sulfur dioxide (SO2) and nitrogen oxides (NOx). These pollutants could come from natural sources such as volcanoes, but the more common source is from emissions, industrial factories and power plants. 

Once in the air, these two gasses can combine with water vapor. Then when it rains, diluted forms of sulfuric acid and nitric acid fall from the sky. Even if rainwater is slightly more acidic than is typical, the cumulative effects over the decades can be significant. 

Acid rain doesn't always involve rain. The term also includes when snow or fog is contaminated with nitric and sulfuric acids. There's also dry deposition when the contaminants fall as airborne particles. 

There's also a wild card in the system, and that's wind; contaminants can be carried hundreds of miles away. For example, the tall smokestacks of coal-burning power plants of the Ohio Valley caused acid rain to fall in Canada. 

Where Is Acid Rain the Worst?

The geography of acid rain must consider both the location where the contaminants originated and the location where they fell back to the ground. 

This phenomenon has created a concentration of acidity in the Northeast. Here, several large urban cities have demanding power-production needs. On top of this, the eastern winds carry the pollution from the Midwest to the east coast, increasing the local acidification.

The National Atmospheric Deposition Program (NADP), hosted at the University of Wisconsin-Madison, monitors the chemistry of precipitation. The most recent report from the National Trends Network revealed average pH levels from across the country. 

These latest measurements show there is a new cluster of acid rain concentrations in the southeast.

15 Cities with the Most Acidic Rain
pH measurement (hydrogen ion concentration)

  1. Lafayette, LA: 4.9
  2. Tampa, FL: 4.9
  3. Tallahassee, FL: 5.0
  4. Cambridge, OH: 5.0
  5. Albany, NY: 5.0
  6. Charleston, SC: 5.0
  7. Montgomery, AL: 5.1
  8. Morgantown, WV: 5.1
  9. Boston, MA: 5.1
  10. Pittsburgh, PA: 5.1
  11. Portland, ME: 5.1
  12. Harlan, KY: 5.1
  13. El Dorado, AR: 5.1
  14. Houston, TX: 5.1
  15. Williamsport, PA: 5.1

Note: A lower pH means it's more acidic.

How Has Acid Rain Changed Over Time?

Sulfur and nitrogen levels are two of the primary indicators of acid rain since they are the elements that contribute to the acidification of waterways. By measuring the quantities of these indicators, researchers can identify the progress being made in the fight against acid rain. 

The good news is that when it comes to sulfur, we're in a much better place now than when we were just 20 years ago. Using the EPA's long-term monitoring data, we can see exactly how much progress has been made. 

acid rain sulfur levels

There is a shocking difference between the two sets of readings. During the 2017-2018 readings, the eastern U.S. had a 76 percent reduction in the total sulfur deposition as compared to readings during 2000 and 2002.

The other key element that contributes to acid rain is nitrogen. Improvements have been made on lowering nitrogen oxides; however, the impact is less than that of sulfur dioxide.

acid rain nitrogen levels

The measurements taken during the 2016-2018 timeframe show a 29 percent reduction in nitrogen deposition in the east coast, as compared to measurements taken between 2000 and 2002.

How Does Acid Rain Affect the Environment and Buildings?

Small changes in water’s pH can have a big impact. 

A healthy lake has a neutral pH of 6.5. If lake water acidifies to a 5.5 pH, tadpoles and crayfish die. At a pH of 5.0, most fish eggs cannot hatch, and if the pH reaches 4.2, all fish die. But it's not only the aquatic life that's affected — trees will die from acid rain as it strips nutrients from the soil. 

Acid rain also affects man-made objects. It corrodes metal and deteriorates stone. The rate of decay will vary by material. For example, granite is resistant to acid rain, while limestone or marble dissolves more readily. 

In Washington, DC, the monuments in the National Mall have been impacted by acid rain. The statues have become less detailed and surfaces have changed. It's an inevitable result of the city's rain pH at 4.3 pH in 1997 and 4.9 pH in 2010. 

Acid rain can also impact buildings. Both concrete and masonry can begin to deteriorate when exposed to acidic solutions. Older homes that experienced the severe acid rain of the 1980s could be especially at risk. 

In thinking about acid rain's effect on a concrete foundation, the chemistry of construction materials comes into focus. For example, many home foundations in New England have been identified as having the mineral pyrrhotite included in the concrete mixture. As these foundations are exposed to rain and air, they will swell, crack, and crumble. This prompts homeowners to think more broadly about the ways homes can be damaged. 

The chemical interaction between acid rain and concrete can have a cumulative impact on the health of your home. As concrete deteriorates, its strength could be reduced and the surface could become more porous. 

This puts your home at immediate risk for moisture problems in addition to the broader question of structural stability. 

Worried that your foundation or cement surfaces could be at risk? Get a free inspection from your local basement waterproofing and foundation repair experts.