When minimizing groundwater contamination, which sources are considered major?

The major sources of groundwater contamination include point and non-point sources. Point sources are specific, identifiable sources of pollution, such as a pipe discharging waste from a factory or a leaky underground storage tank. These sources can be monitored and managed more easily because they are localized. On the other hand, non-point sources are diffuse sources of pollution, often associated with agricultural runoff, urban stormwater, or atmospheric deposition. These are more challenging to control and track due to their widespread nature.

Understanding the distinction between these sources is crucial for effective groundwater protection strategies. Addressing both point and non-point sources is necessary to minimize the risk of groundwater contamination, which can have significant implications for public health and the environment.

The other options, while they may influence water safety, do not classify as the major sources of groundwater contamination in the context provided. Rain, snowmelt, and sinkholes can contribute to groundwater quality issues but are not primary sources like those categorized as point and non-point. Additionally, while accidents involving trains and trucks can lead to localized contamination, they are not consistent sources of groundwater contamination on a broader scale like the two categories in the correct answer.