Michigan Test for Teacher Certification (MTTC) Secondary Integrated Science Practice test

How do contaminants typically enter bodies of water?

1. Through evaporation

2. By ground runoff or leaching

3. Via aerial spraying

4. By direct dumping

The correct answer is: By ground runoff or leaching

Contaminants typically enter bodies of water primarily through ground runoff or leaching, which refers to the process where water transfers pollutants from the land into streams, rivers, lakes, and other water bodies. When it rains or when snow melts, the water runs off the surface of the ground, and as it does so, it can pick up various substances such as fertilizers, pesticides, waste materials, and other pollutants. This runoff can travel across agricultural fields, urban areas, or industrial sites, thereby bringing harmful contaminants into adjacent water bodies. Leaching occurs when water seeps downward through soil and rock layers, carrying dissolved substances with it. This can lead to the contamination of groundwater, which can subsequently flow into surface water sources. Therefore, ground runoff and leaching are significant pathways for contaminants to reach aquatic environments, impacting water quality and ecosystem health. The other methods of contamination, while they exist, are typically less common. For example, evaporation does not directly introduce contaminants into water bodies. Aerial spraying primarily involves airborne application of pesticides or herbicides, which could lead to localized contamination but is less direct compared to ground runoff. Direct dumping can introduce contaminants as well but is usually a more obvious and intentional act rather than a typical means of contamination in the