What is an example of non-point source contamination of groundwater?

Non-point source contamination refers to pollutants that are released over a wide area rather than from a single, identifiable source. This type of contamination occurs when rain or snowmelt moves across the ground, picking up contaminants and carrying them into waterways or groundwater. The scenario where pesticides dissolve and leach through soil after it rains exemplifies this process.

When precipitation occurs, the water can infiltrate the soil, carrying with it the dissolved pesticides from a broad area, influenced by factors like land use, management practices, and geography. This dispersal makes it difficult to pinpoint a specific source for the pollutants, thus categorizing it as non-point source contamination.

On the other hand, other options like pesticides stored in drums, runoff from a treated lawn, and discharge from a waste facility typically have more identifiable sources of contamination. For instance, the runoff from a treated lawn, while it can lead to contamination of nearby water bodies, often originates from a specific site and can be traced back to where treatments were applied.