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The effects of urbanization on water quality:
Toxic metals

Small amounts of some toxic metals tend to accumulate in the food chain and can damage living things. In the past, most toxic metal pollution came from mining activities and individual sources, such as wastewater-treatment plants and smoke-stack emissions. Federal and State regulations have resulted in the reduction of toxic metals from these sources. Metals tend to attach themselves to dirt and sediment, and thus, they are still present in the stream beds and banks of many urban streams.

Concentrations of toxic metals in stream sediments could be reduced if:

• Trash is properly disposed of or recycled
• Major streets and parking lots are routinely cleaned
• Stormwater is caught and kept in ponds to trap metal-laden sediments

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Effects of urbanization  Ground-water quality