How does arsenic get into groundwater?

Arsenic is a relatively common element that occurs naturally in rocks and soil. more

Arsenic can also be a byproduct of some human activities, such as apple-orchard spraying, coal-ash disposal, or use of some pressure-treated wood. In Ohio, however, evidence indicates that arsenic in groundwater is released from rocks and soil, and is therefore considered to be a “natural contaminant.”

Under certain geochemical conditions, arsenic can be released from rocks and soil and enter the groundwater.more

The figures below illustrate how arsenic can get into the groundwater.



In Ohio, arsenic can be released from iron oxides if groundwater has these characteristics:

  • neutral to slightly alkaline pH (a pH of about 7 or slightly greater),
  • “reducing” redox conditions (indicated by low oxygen and high iron concentrations).

In other parts of the country, arsenic can be released from different minerals, under different geochemical conditions.

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