CAS Number: 7439-97-6. Mercury is a naturally occurring metal
which has several forms. The metallic mercury is a shiny,
silver-white, odorless liquid. If heated, it is a colorless,
odorless gas. Mercury is known to be harmful to the central
nervous system, and is readily absorbed through the respiratory
tract, the gastrointestinal tract, and through unbroken skin.

Highest observation.

CAS Number: 10028-15-6. A triatomic, very reactive form of
oxygen that is a bluish, irritating gas of pungent odor. It is
formed naturally in the atmosphere by a photochemical reaction.
It is a major air pollutant in the lower atmosphere but a
beneficial component of the upper atmosphere. Ozone is used for
oxidizing, bleaching, disinfecting, and deodorizing. Chemical
formula = O3. Molecular weight = 47.998 g/mol.

The amount of oxygen required by aerobic microorganisms to
decompose organic matter in a water sample, based on the maximum
rate of O2 consumption in a water sample over a five-day period
in the dark at 20 degrees C. It is used to estimate the total
amount of "biodegradable" organic matter in the
system and
therefore serves as a measure of the degree of water pollution.

Many organochlorine pesticides phased out since substantial use
began in the
1960's have properties that result in their increased
accumulation up the food
chain (bioaccumulation). Dichlorodiphenyl trichlororethane
(DDT), dieldrin, and
toxaphene are bioaccumulative pesticides that are no longer in
use in the
United States, but persist and are still detected in the
environment. Exposure
to bioaccumulative pesticides can affect nervous, reproductive,
and immune

Lead is a metal found naturally in the environment as well as
in
manufactured products. The major sources of lead emissions
have
historically been motor vehicles (such as cars and trucks) and
industrial sources. Due to the phase out of leaded gasoline,
metals processing is the major source of lead emissions to the
air today. The highest levels of lead in air are generally
found
near lead smelters. Other stationary sources are waste
incinerators, utilities, and lead-acid battery manufacturers.

Minnesota Department of Natural Resources lake identification
number. Lake ID numbers are taken from the Minnesota Department
of Natural Resources, 1968 publication "Bulletin 25: An
Inventory
of Minnesota Lakes." It is a six-digit code with the first two
digits indicating the county and the next four the lake number.
These numbers are used for storing/retrieving data in STORET
(EPA's STOrage and RETrieval database). Lakes with a 01, 02,
etc., suffix indicates that the lake has

The Clean Water Act requires states to publish, every two
years, an updated list of streams and lakes that are not
meeting their designated uses because of excess pollutants. The
list, known as the 303(d) list, is based on violations of water
quality standards. For a list and maps of impaired waters in
MN go to the <a
href="http://www.pca.state.mn.us/water/tmdl/index.html">TMDL</a&gt;
Web
page.

Photosynthetic pigment found in all green plants, and the main
pigment in algae. The concentration of chlorophyll a is used to
estimate the amount of algae (all phytoplankton in a given area)
in surface water. Measured in micrograms per liter
(&micro;g/L).
<br><br>
While it is normal to find algae in streams and lakes, high
levels of algae can lead to low levels of dissolved oxygen in a
water body.

The ability of a substance to conduct or transmit heat,
electricity, or sound. Relating to water quality, it is a
measure of dissolved minerals and/or ions in the water.
Typically measured in micromhos per centimeter (&micro;mhos/cm).
<br><br>
If baseline levels of conductivity are established for an area,
this measurement can be used to detect possible pollution
discharges that have a high ionic strength. This would include
manure directly from livestock in streams, land application, or