Sanjiv G.
Chem. 1 Honors
5/15/02
Piney Z Narrative and Final Discussion
Natural and Cultural History: Piney
Z and I go back a long way, a whole year, but the history of this
lake itself begins when it was still a river (Piney Z is now a
small lake in the Lake Lafayette Chain.) A major landmark in its
development came in 1947, when, to serve the interests of duck
hunters and fishermen, it was dammed up. The downside appeared
later, as muck collected on the lake floor because the dam had
disturbed the “growth and decay processes” of living
things in the lake. And so abundant amounts of algae, other organisms,
etc. replaced some innocent inhabitants: fish! The fish population
decreased in number rapidly. What could be done? Though Piney
Z never was and still isn’t perfect, much of the accumulated
muck was used to build dikes. We took our experiments on the dikes,
in fact.
In 1995, the city of Tallahassee, Florida bought the 193-acre
Piney Z Lake and the 407 acres of property surrounding it. It
can be reached by means of east Apalachee Parkway. The lake gets
its name from the “z” shape of the land, covered with
pine trees. Piney Z water isn’t as murky as it was before,
and its turbidity varies from day to day, but only thanks to the
careful work of the Florida Fish and Wildlife Conservation, who
drained the lake and re-introduced game fish there (bass, bluegill,
and shellcracker are some examples.) They started in 1996 with
$150,000 and when the project is complete, it will provide for
a great place to bike, picnic, hike and view wildlife. Piney Z
isn’t open to the public now, but it’ll be a park
in the future.
Underneath Piney Z, and indeed under all of Florida, exists the
Floridan aquifer—a “layer of porous limestone or dolomite.”
This is where we get our drinking water, at one of the major American
aquifers, which really extends into three other states. The layer,
composed of areas that have gravel and sand, areas that are solid
limestone, and areas that have porous limestone tunnels where
water runs through. These are all features of Karst Topography
(“karst” means stone.) Sinkholes usually happen where
karst topography is present.
Piney Z, like all lakes, constantly undergoes a process called
eutrophication. Lakes age over time and become more productive.
The name for this: natural eutrophication. Cultural eutrophication
concurs with the expansion of nearby communities, since it is
defined as the water pollution “caused by excessive plant
nutrients.” Agricultural runoff, untreated sewage, and phosphates
(used as water softeners) contribute to significant changes. Algae
blooms, the direct result of excessive phosphates, bring down
the oxygen level of the water, killing fish. Oxygen depletion
and dead fish were specific problems relating to Piney Z.
Water Quality: Scientists break down water quality
into well-defined categories to easily assess the water’s
condition. Some classifications are…
|Temperature| Temperature influences the solubility of solids
in that the higher the temperature, the more will dissolve. Dissolved
oxygen, however, is inversely proportional to the temperature.
This second relationship is the reason why summertime heat can
mean death for many fish. Such temperature changes let a smaller
number of fish eggs hatch.
A thermometer, with electronic precision (calculator), gave our
research groups the temperature of the water.
|Dissolved Oxygen| By this term we mean the amount of (gaseous)
oxygen dissolved in the water. Necessary for aerobic metabolism,
DO comes from the outside air as well as from photosynthesis.
DO levels below 5.0 mg/L are considered stressful, while levels
of 1-2 mg/L are deadly. The water can’t hold too much oxygen
either, or aquatic life will experience gas bubble disease, when
blood circulation is blocked. Piney Z can’t be an urban
fishery without any fish; therefore we should try to keep the
right amount of dissolved oxygen in the lake.
To find DO levels, we first fixed the oxygen with a reacting chemical,
then added chemicals that would indicate certain properties according
to the mixture’s color, then added another substance drop
by drop until it altered the color of the fluid.
|pH| pH measures the acidity or “basic nature” of
a solution. Specifically,
pH = -log [H+]. Every downward step taken on the pH scale means
ten times as many positive hydrogen ions. Importantly, pH levels
affect how dangerous substances like iron are, for iron can be
more toxic in some cases, depending on the pH level. 6.0-9.0 is
a great range for the pH to be within for freshwater fish.
A titrimeter reads the pH using millivolts.
|turbidity| The question is, how clear is the water? Suspended
solids that cause murkiness include microscopic floating plants
(i.d. phytoplankton.) Less lights makes it through the water when
junk like this is in the way, so plants on the lake floor can’t
get enough sunlight to photosynthesize, which in turn depletes
the DO level, killing fish. People don’t like turbidity
either, basically because it’s ugly.
We eyeballed the lake to judge how clear it was.
|phosphates| Plants and animals need phosphorous to develop. The
three types of PO4 phosphates that come from phosphorous are orthophosphate,
metaphosphate, and organically bound phosphate. The first originates
in sewage, the second are used mainly for detergents, and the
third is involved with pesticides. Pesticides on lawns, etc. washes
off with rain, bringing beneficial nutrients to the water. But
too much of a good thing encourages a lot of algae growth, which
suppresses all other life forms.
|nitrates| Making up a large part of the generic protein, nitrogen
is a universal element. Nitrate is NO3-. Bacteria can and do manufacture
nitrate from nitrite (NO2-), which is potentially harmful to humans,
but nitrogen compounds are actually essentials to natural eutrophication.
Nitrates and nitrites are responsible for bolstering algae and
plankton growth, yet again, they’re sometimes too good for
the water and many lives of the lake are put in jeopardy.
