Soil and Acid Rain

Introduction

Acid rain can be very harmful to the environment. It can kill fish by lowering the pH of lakes and rivers. It can harm trees and plants by burning their leaves and depriving them of nutrients. In addition, it can weather away stone buildings and monuments. But why is it more of a problem in some places than others?

To answer this question, let’s first look at how rain becomes acidic. Carbon dioxide, CO₂, is a gas found naturally in the air. When CO₂ dissolves into rain droplets, it produces a weak acid called carbonic acid, H₂CO₃. This makes rain slightly acidic naturally. Rain of pH 5 to 6 is common and does not generally cause any problems. When fossil fuels are burned, however, gases such as sulfur dioxide, SO₂, are released into the air. When sulfur dioxide dissolves into rain droplets, sulfuric acid, H₂SO₄, is formed. This rain can be as acidic as pH 4.

In this experiment, you will use a pH Sensor to measure the pH of acid rain. You will then allow the acid rain to filter through two different types of soil. The run-off will be collected and its pH retested to determine your soil’s buffering capacity.

Objectives

In this experiment, you will

• Use a pH Sensor to measure the pH of acid rain.
• Use a pH Sensor to measure the change in pH as acid rain passes through soil.
• Interpret your results.