What is often a source of pollution and is affected by runoff?

Surface water is often a source of pollution and is significantly affected by runoff because it collects water from rainfall and melting snow, which can carry various contaminants such as fertilizers, pesticides, and sediments from agricultural and urban areas. When there is heavy rain or storm events, runoff can increase dramatically, leading to the transport of these pollutants directly into lakes, rivers, and streams. This not only affects the quality of the water but can also disrupt aquatic ecosystems and harm wildlife.

In contrast, while groundwater can be impacted by surface runoff contaminants that seep through the soil, it operates under different dynamics and is less immediately affected by surface runoff itself. Air quality and soil health can be influenced by agricultural practices and pollutants, but they are not primarily characterized as being directly affected by runoff like surface water is.