Which scenario is an example of nonpoint-source contamination of groundwater?

The scenario involving pesticides dissolving and leaching through soil after it rains is a classic example of nonpoint-source contamination of groundwater. Nonpoint-source contamination occurs when pollutants are not traced to a single, identifiable source. In this case, the pesticide application in the general area leads to rainfall washing the chemicals into the soil, which then percolate down into the groundwater system.

This type of contamination is characterized by its diffuse nature, often arising from widespread activities such as agricultural practices, urban runoff, or landscaping, rather than from a specific spill or leak at a defined location. The process often makes it challenging to pinpoint the precise origin of the contamination, which complicates remediation efforts.

In contrast, the other scenarios present more direct or point-source contamination where the origin of the pollution can be easily identified, such as a direct spill or improper storage of pesticides. These situations typically lead to targeted pollution effects that can be managed more readily than nonpoint-source issues.