There are many causes of water pollution – general
environmental conditions like overpopulation, individual incidents like
oil spills, specific pathogens in sewage or fertilizer. And there are
different categories: point source pollution, such as from a pipe at an
industrial plant, and nonpoint source pollution, in which contaminants
reach waterways through runoff, soil saturation, groundwater, and
rainfall. Because water problems are so local, with so many reasons
behind them, there is no single solution. Here are 12 common causes of
pollution to consider.
MINING OPERATIONS
King River, Australia
King River, Australia
Mining can contribute to water pollution in a variety of ways – and
not just when a containment dam holding pools of mine slurry sustains a
breach. Rainwater can wash tailings (mine waste) into nearby bodies of
water, and leach metals and sulfur compounds from rocks that are exposed
during the excavation process. In gold mining, cyanide used to extract
gold from ore often leaks into the water table, contaminating
groundwater. A classic example of a body of water polluted by mining is
the King River, in an area where copper was mined for more than a
century. Although mining was curtailed in 1995, its effects continue as a
result of discarded tailings and dissolved metals still present in the
river.
OIL SPILLS
Niger Delta, Nigeria
Niger Delta, Nigeria
Oil spills contaminate anything on the water’s surface, and kill
plants below the surface by blocking sunlight. Fish and wildlife
experience increased mortality rates, either from direct exposure or
from eating contaminated invertebrates. It is estimated that the Niger
Delta, on the west coast of Africa – home to more than 600 oil fields –
experiences the equivalent of the Exxon Valdez oil spill every year. The
spills can come from leaking terminals, pipes, pumping stations, and
oil platforms. Shell, which is reportedly working in partnership with
the Nigerian government, says that 98 percent of the spills are caused
by vandalism or theft, and a minimal amount is related to
infrastructural issues.
NUTRIENT POLLUTION (EUTROPHICATION)
Chesapeake Bay, North Carolina, USA
Chesapeake Bay, North Carolina, USA
Nutrients may sound good, but excessive amounts of those like
nitrogen and phosphorous can wreak havoc on coastal ecosystems. By
elevating algae levels and causing hypoxia – lack of oxygen – they can
result in widespread destruction of fish and other aquatic life. The
nutrients reach the water through fertilizer runoff and sewage discharge
as well as air pollution, and lead to overgrowths of toxic algae called
red tides or brown tides. Zooplankton eat the algae, and the toxins
work their way up the food chain, reaching humans through shellfish.
When the overgrowths die, the algae decomposes, creating severe hypoxic
conditions called dead zones. In 1997, several Chesapeake Bay tidal
creeks experienced an outbreak of Pfiesteria, a toxin-producing pathogen that caused a massive fish kill as well as human health problems.
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