Causes And Sources Of Contamination

A groundwater contaminant is defined by most regulatory agencies as any physical, chemical, biological, or radiological substance or matter in groundwater. The contaminants can be introduced in the groundwater by naturally occurring activities, such as natural leaching of the soil and mixing with other groundwater sources having different chemistry. They are also introduced by planned human activities, such as waste disposal, mining, and agricultural operations. Because the contamination from naturally occurring activities is usually small, it is not the focus of this chapter. However, human activities are the leading cause of groundwater contamination and the focus of most regulatory agencies.

The most prevalent human activities that cause ground-water contamination are (1) waste disposal, (2) storage and transportation of commercial materials, (3) mining operations, (4) agricultural operations, and (5) other activities as shown in Figure 9.11.1.

This section discusses the principal sources and causes of groundwater contamination from these activities with regard to their occurrence and effects on groundwater quality.

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