Which of the following is an example of how a water system is contaminated by non-point source pollution?

a. hikers toss food packaging into a mountain stream.
b. chemicals from batteries in a landfill leach into the groundwater supply.
c. several inches of acid rainfall over a lake.
d. an oil pipeline bursts along the ocean floor.
e. fertilizers applied to a crop field run off the soil and into a river.

C. Several inches of acid rainfall over a lake.

Explanation:

Nonpoint source pollution refers to pollution resulting from many diffuse sources (a combination of pollutants from a large area). Point source pollution is the opposite, as it results from one source, such as power plants and factories. Common causes of nonpoint source pollution are land runoff, precipitation, drainage, seepage, or even rainfall and snowmelt, in cases when it's not possible to trace pollution back to a single source.

All of the given examples, except for acid rainfall, are examples of point source pollution, as there is only one known source in each case: food packaging, chemicals from batteries, the burst of the oil pipeline, and fertilizers. Acid rain occurs when compounds like sulfur dioxide and nitrogen oxides are released into the air, where they mix and react with water, oxygen, and other chemicals. This process results in acid rain. The sources of these harmful compounds are multiple (e.g. many factories and power plants), so this is an example of nonpoint source pollution.