adapted to HTML from lecture notes of Prof. Stephen A. Nelson Tulane
image from: http://compoundchem.com
Accumulates in our bodies over long periods of time. The US EPA, has set
maximum standards, or limits, for many of these.
Lead -- Less than .05 ppm in water.
Arsenic -- Less than .05 ppm in water.
Mercury -- Less than .002 ppm in water.
Nitrates -- Less than 10 ppm in water.
Main sources are fertilizers and sewage.
Inhibits blood ability to carry oxygen.
Can not boil water to remove, like you can with bacteria and virii --
boiling only concentrates nitrates, making them more toxic.
Epidimiology - Study of disease rates and what causes them. Often provide
a very valuable source of information on how deaths are related to other
It was found that taking into account all possible causes for the
differences in death that:
The hard water regions have the lower death rates.
The soft-water regions, which are the areas in the coastal plains, have
the higher death rates.
Water Pollution and How it Occurs
Point Source Pollutants
Pollutants that enter into the system at one single point.
Gas storage tanks -- Metal tanks set into the ground can sometimes
rust and develop a leak.
Sewage Treatment Plants -- Often discharge wastes into nearby water
source after treatment.
Laundromats and carwashes -- Detergents and chemicals dumped onto
the round seep down to contaminate groundwater source.
Industrial Plants -- often discharge waste products into nearby
Non-Point Source Pollutants
Fertilizers, pesticides, and herbicides applied to fields, gardens,
Leaking sewers in a city.
Flow of Pollutants
Ground water - flows along the gradient in the water table, taking a path
that is perpendicular to the contours. Pollutants in the groundwater will
flow in plumes along the same path. When a pollution source is introduced
into the groundwater, the resulting plume will only affect areas
downgradient from the source. Areas upgradient of the source, to the sides
of the plume or below the plume will not be contaminated. Groundwater
flows relatively slowly. On Long Island a typical rate of flow is about
one foot per day near the water table. As the contaminant plume travels it
becomes somewhat broader and more dilute as it slowly mixes with the
surrounding cleaner water. Depending upon the original concentration of
the plume and the distance the plume travels the contaminants may become
so diluted that eventually the concentrations are lower than drinking
Selected Water Pollutants
Oxygen Demanding Waste
Biochemical Oxygen Demand -- When waste uses up oxygen needed for
bacteria or other life.
Fecal Coloform Bacteria -- found in fecal matter. Used to measure
sewage presence in water.
Not dangerous for the most part.
Cryptosporidium -- Bacteria, can be lethal. Infested Milwakee water
supply at one point.
Giardin -- Found in deer and other animals. Why you shouldn't drink
from wild streams without filtering water first.
Overabundance of Nutrients -- can cause Eutrophication.
Anoxia -- When the overabundance of nutrients causes an algal bloom
in the spring and early summer. Later in the summer these algae settle
to the bottom and bacteria feed on the algae which uses up the free
oxygen in the bottom waters of the body of water.
Hypoxia -- When the algeal bloom results in a low level of oxygen
within the water body which will not sustain normal bottom dwellers or
The lack of oxygen causes the existing life within the water body to
die, and decay. This, in turn, allows time for the replenishment of
oxygen, as well as providing nutrients for later life.
Hazardous Chemicals (Toxic organic and Inorganic compounds).
Many used to come from Dry Cleaners waste products.
Heavy Metals -- Lead, Mercury, Zinc, Cadmium
Sediments -- In zones of high erosion, sediments can really clog up
many streams and ponds.
Thermal Pollution Many industries use water to cool their factory
machines. They then dump this warm water back into it's source. This is
pretty harmful to the native life of the region, as it has generally
evolved to survive in a particular range of temperatures.