Page 432 - Environment: The Science Behind the Stories

be many years or decades. The long-lived pesticide DDT, for
instance, is found widely in U.S. aquifers even though it was
banned over 35 years ago. Moreover, chemicals break down
much more slowly in aquifers than in surface water or soils.
Decomposition is slower in groundwater because it is not
exposed to sunlight, contains fewer microbes and minerals, and
holds less dissolved oxygen and organic matter. For example,
concentrations of the herbicide alachlor decline by half after 20
days in soil, but in groundwater this takes almost four years.

There are many sources
of groundwater pollution

Some chemicals that are toxic at high concentrations, includ-
ing aluminum, fluoride, nitrates, and sulfates, occur naturally
in groundwater. After all, groundwater is in contact with rock
for thousands of years, and during that time all kinds of com-
pounds, both toxic and benign, may leach into the water.
However, groundwater pollution resulting from human Figure 15.25 Leaky underground storage tanks are a
activity is widespread. Industrial, agricultural, and urban major source of groundwater pollution. Underground tanks
wastes—from heavy metals to petroleum products to solvents housing radioactive waste at the Hanford Nuclear Reservation in
to pesticides—can leach through soil and seep into aquifers. Washington were found in 2013 to be leaking, threatening ground-
Pathogens and other pollutants can enter groundwater through water and the nearby Columbia River.
improperly designed wells and from the pumping of liquid haz-
ardous waste below ground (p. 645). A recent 17-year study of
volatile organic compounds (VOCs; p. 477) detected 42 types 2000, the groundwater supply of Walkerton, Ontario, became
of VOCs from manufactured products and industrial processes contaminated with the bacterium Escherichia coli, or E. coli.
in nearly all U.S. aquifers and in 18% of wells sampled (p. 386). Two thousand people became ill, and seven died.
Leakage of carcinogenic pollutants (such as chlorinated
solvents and gasoline) from underground tanks of oil and indus- Legislative and regulatory efforts
trial chemicals also poses a threat to groundwater. Across the have helped to reduce pollution
United States, the U.S. Environmental Protection Agency (EPA)
has embarked on a nationwide cleanup program to unearth and As numerous as our freshwater pollution problems may seem,
repair leaky tanks. After more than 15 years of work, by 2013 it is important to remember that many were worse a few dec-
the EPA had confirmed leaks from 510,000 tanks, and had com- ades ago, when the Cuyahoga River repeatedly caught fire
pleted cleanups on over 430,000 of them. (p. 193). Citizen activism and government response during
The leaking of radioactive compounds from underground the 1960s and 1970s in the United States resulted in legisla-
tanks is also as source of groundwater pollution. In 2013, fed- tion such as the Federal Water Pollution Control Act of 1972
eral and state officials revealed that an underground storage (later amended and renamed the Clean Water Act in 1977).
tank at the Hanford Nuclear Reservation in Washington was These acts made it illegal to discharge pollution from a point
leaking 568–1135 L (150–300 gal) of radioactive waste into source without a permit, set standards for industrial waste-
the soil each year (Figure 15.25). Shortly thereafter, leaks were water, set standards for contaminant levels in surface waters,
found in another five tanks. The site is the most radioactively and funded construction of sewage treatment plants. Thanks
contaminated area in the United States, and stores 60% of the to such legislation, point-source pollution in the United States
United States’ high-level radioactive waste in 177 underground was reduced, and rivers and lakes became notably cleaner.
tanks. It has been storing wastes since the 1940s, and billions In the past decade, however, enforcement of water qual- CHAPTER 15 • Fr E shwat E r s yst E m s and rE sour CE s
of dollars have been spent on remediation efforts at the facility. ity laws grew weaker, as underfunded and understaffed state
Its cleanup has experienced delays and cost overruns, however, and federal regulatory agencies succumbed to pressure from
and the radioactive material in aging underground tanks is not industry and from politicians who receive money from indus-
scheduled to be completely removed until 2040. try. A comprehensive investigation by The New York Times in
Agriculture contributes to groundwater pollution in sev- 2009 revealed that violations of the Clean Water Act have risen
eral ways. Pesticides were detected in most of the shallow and that documented violations now number over 100,000 per
aquifer sites tested in the United States in the 1990s, although year (to say nothing of undocumented instances). The EPA
levels generally did not violate EPA safety standards for and the states act on only a tiny percentage of these violations,
drinking water. Nitrate from fertilizers has leached into aqui- the Times found. As a result, 1 in 10 Americans have been
fers in Canada and in 49 U.S. states. Nitrate in drinking water exposed to unsafe drinking water—for the most part unknow-
has been linked to cancers, miscarriages, and “blue-baby” ingly, because many pollutants cannot be detected by smell,
syndrome, which reduces the oxygen-carrying capacity of taste, or color. In response, EPA Administrator Lisa Jackson
infants’ blood. Agriculture can also contribute pathogens; in promised at the time to strengthen enforcement. 431

M15_WITH7428_05_SE_C15.indd 431 12/12/14 2:20 PM