Containers such as these usually contain industrial waste.
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Groundwater contaminants
Septic tanks, city dumps, and watery waste from human activity may contaminate groundwater. Among many things which contribute to contamination are chemicals found in laundry detergents.
Lots of salt on icy roads in the winter may lead to sodium chloride (NaCl) contamination.
Another very common contaminant to ground water is some fertilizers used in farming which are healthy for plants, but toxic to humans.
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