The pH Scale

This week’s blog was written by Sierra R., a Bass alumni. She attended the Wildlife Leadership Academy this summer because it looked like a good opportunity to further her education and to give her a deeper look into different career fields. Sierra’s hobbies include hiking, nature journaling, Girl Scouts, and theater.

pH stands for Potential Hydrogen. The measurement of pH is used to determine how acidic or alkaline a material is. It ranges on a scale of 0-14. Zero is extremely acidic, while fourteen is extremely alkaline. In the middle of the scale is seven, which means that the pH is neutral.

Our body has a variety of pH throughout its systems. The digestive system holds a strong stomach acid so it can digest our food, but our stomach is coated in alkaline bile as a way to keep the acid from burning through our stomach. Just like our digestive system, many other systems in nature require a balanced pH to function.

Both aquatic and land organisms require a balanced pH in their habitat. However, many species have a range of tolerance. For example, many fish and macroinvertebrates can live in slightly alkaline (7-9.0 pH) or slightly acidic waters(7-5.0 pH), and the optimum pH range for most plants is usually 7-5.5 (Perry, Leonard). These variations are a good thing; having a wide variety of pH tolerance allows for diversity in an ecosystem. What is not healthy, however, is when an ecosystem has a drastic shift outside of its normal pH levels.

The pH scale

What causes pH level differences?

Some natural things that would cause slightly acidic soil or water include: Decaying of plants like fall leaves and regular precipitation of rainwater, which normally has a pH of 5 to 5.5 (pH Scale).

Things can naturally become alkaline as well. Usually, alkaline soils form in dry climates when plant materials high in carbonate begin to decompose or when deposits of alkaline material such as limestone become exposed to sources of water (Landscape-Water-Conservation).

There are many ways that pH levels can un-naturally change:

  • Putting too much lime or peat in a yard
  • Not properly disposing of chemicals and cleaners
  • acidic rain caused by pollutants in the air
  • abandoned mine drainage caused by exposed metals oxidizing with water and air and then leaching into soils and streams
  • chemical leakage from a factory or pool

If you come across a chemical spill or incident of a similar nature, you should report it to your State’s designated environmental agency. Here is PA’s DEP (Department of Environmental Protection) page on reporting environment complaints:

Dramatically high and low pH levels can disrupt the environment. Unnatural pH levels often prevent plants from being able to pick up all the nutrients they need to grow. Many macroinvertebrates, amphibians, and fish eggs are sensitive to pH levels. It is important to keep an eye on your area’s pH-sensitive wildlife as a decline in their health could be an indicator of environmental problems in your area.

A while back, I came across a gardening site that had instructions on how to test the general pH level of your soil, and I decided to try it out. I enjoyed it a lot, so I thought I would share my version of it. The instructions below are similar to the instructions I found, but the measurements are scaled-down, and the instructions are changed based on how I did my test. If you would like to see the original version, here is the link:


  • Something to dig with (small shovel or metal spoon)
  • 1 spoon
  • 1 plastic snack bag
  • 2 medium to small bowls
  • ¼ cup of white vinegar
  • ¼ cup of room temperature water
  • 1 Tablespoon of baking soda
  • ½ cup of dirt (divided)


Using a shovel or metal spoon, fill a plastic snack bag with about half a cup of soil. Divide the contents equally into 2 separate bowls (about ¼ cup per bowl). Next, measure about ¼ cup of white vinegar and empty it into one bowl of dirt. Watch to see if the soil fizzes or gets foamy. If it does, that means your soil is probably slightly alkaline. If it does not, then you should continue to the next paragraph.

I used Walmart brand snack bags for my soil sample
The regular baking soda and white vinegar I used for my soil pH test

To test for acidic soil, measure ¼ of a cup of room temp water in a clean measuring cup. Then, dump 1 tablespoon of baking soda into the water. With a spoon, gently stir the water for a second and then pour the baking soda water into the other bowl of dirt. Watch it for a little while. If it fizzes or foams, then your soil is slightly acidic. If nothing happens at all during both tests, then you most likely have neutral soil.

After doing my test, I found out my soil was slightly acidic. Notice the sample on the right side tested with baking-soda-water is fizzing.

An important thing to note is that these are estimations and this in no way replaces the pH test you can buy at the store. Store-bought pH testing kits or strips are what you would want to get if you need precise and accurate pH measurements. But this do-it-yourself pH test can be a fun experiment to do with kids as an educational project.

The graphic image used in this blog was sourced from the internet! It can be found here. The rest of the photos belong to the author. The sources that the author used can be found here, here, here, and here.