OPEN FILE REPORT NO. 85


 Physical Field Parameters

 Measurements of field analytes are taken directly in the field prior to water sampling.
They include dissolved oxygen, pH, specific conductance, water temperature and discharge.
Other data collected in the field include local geology, weather conditions and adjacent land
use practices.

Dissolved Oxygen Oxygen readily dissolves in water. The source of oxygen can be atmos-
pheric or biological. Typically, springs that discharge water from a deep aquifer source have
a low dissolved oxygen content. On the other hand, relative to springs, the dissolved oxygen
content in river rise water is high. This is due to a greater exposure to the atmosphere and
an increase in biological activity.

pH pH measures the acidity or
alkalinity of water. It is defined
as the negative log of the activity
of the hydrogen ion in a solution.
Values range between 0 and 14.
A low pH represents acidic, and a
high pH represents alkaline con-
ditions. A pH near 7 indicates
the water is near neutral condi-
tions.

 Rainwater has a low pH and is ..
naturally acidic. As moisture
passes through the atmosphere, J,
it picks up dissolved carbon diox-
ide, forming carbonic acid. In
Florida, as rainwater passes
through soil layers it incorpo-
rates organic acids and the acidi- -
ty increases.

 When acidic water enters a
limestone aquifer, the acids react
with calcium carbonate in the ii.
limestone and dissolution occurs. ... -
Generally, most spring water Figure 7. An FGS Spring Sampling Team, 2001
falls within a pH range of 7 to 8. (photo by Tom Scott)
During heavy rain events, spring water can drop in pH as tannic acids, from nearby surface
waters, are flushed into the spring system. It should be noted that sampled river rises tend
to have a lower pH than the spring systems, due to the surficial component of the water.

Specific Conductance Specific conductance is a measure of the ability of a substance, in
this case spring water, to conduct electricity. The conductance is a function of the amount
and type of ions in the water. The variability of the specific conductance of spring water can
be quite high when the spring is discharging saline water or when the spring is discharging
into the marine environment.