Groundwater - The Changing Earth: Exploring Geology and Evolution - page 345

Geo-Focus

Arsenic and Old Lace

also harms the central and peripheral
nervous systems and may cause birth
defects and reproductive problems. In
fact, because of arsenic's prevalence
in the environment and its adverse
health effects, Congress included it in
the amendments to the Safe Drinking
Water Act in 1996. Arsenic gets into the
groundwater system mainly as arsenic-
bearing minerals dissolve in the natural
weathering process of rocks and soils.

A map published in 2001 by the
U.S. Geological Survey (USGS) shows
the extent and concentration of arsenic
in the nation's groundwater supply
(

Many people probably learned that arse-
nic is a poison from either reading or see-
ing the play Arsenic and Old Lace , written
by Joseph Kesselring. In the play, the
elderly Brewster sisters poison lonely old
men by adding a small amount of arsenic
to their homemade elderberry wine.
Arsenic is a naturally occurring
toxic element found in the environ-
ment, and several types of cancer have
been linked to arsenic in water. Arsenic

Figure 1). The highest concentra-
tions of groundwater arsenic were
found throughout the West and in
parts of the Midwest and Northeast.
Although the map is not intended to
provide specifi c information for indi-
vidual wells or even a locality within a

◗

Concentration of arsenic:

At least 50 µ g/L

10-50
5-10
3- 5
1- 3

Alaska

Puerto Rico

Hawaii

◗

Figure 1 Arsenic concentrations for 31,350 groundwater samples collected from 1973 to 2001.

water in an aquifer, and (3) the solubility of rocks and miner-
als. These factors account for the amount of dissolved materi-
als in groundwater, such as calcium, iron, fl uoride, and several
others. Most pose no health problems, but some have undesir-
able effects such as deposition of minerals in water pipes and

water heaters, an offensive taste or smell, or they may stain
clothing and fi xtures or inhibit the effectiveness of detergents.
A good example that everyone is familiar with is hard wa-
ter , which is a problem in many areas, especially those underlain
by limestone and dolostone. Hard water is caused by dissolved