Fathom QiQuac M5, Руководство по эксплуатации

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The QiQuac uses the closed-form approximation from Appendix 1 of
Richardson et al. It is
(7)
Where CF
T,corr
is the corrected CF.T, CF
T,est
is the estimated CF.T without the
distilled water correction based on Equation 4. EC
T,d
is the EC.T of the distilled
water (or diluent used in the salt standard), EC
BG
is the background EC.T of the
streamwater, and [s] is the concentration of the salt standard in mg/lt ie. 5000
mg/lt. These values are all entered into the Setup menu of the QiQuac.
In low conductivity streams (<100 µ S/cm) the distilled water correction is
small, around 1%, but in high conductivity streams it can be >5%. The QiQuac
reports the CF.T correction after each CF.T calibration.
Properties of Water
and NaCl
Water is a mysterious substance. We take it for granted, but it’s actually quite
unusual, as liquids go.
1. It has the highest surface tension (besides liquid mercury). This facilitates
critical biological function such as the capillary action that allows trees to
heft several kilograms of water 10s of m in the air.
2. It has the highest specific heat (energy required to heat one gram of
a substance by 1˚C) of any liquid which provides an energy buffer for
ecosystems, keeping temperatures relatively steady, and also promotes
circulatory actions of weather
3. It is one of the few substances that becomes less dense as it cools.
It’s weird behavior has made life possible on earth. If the density of water
didn’t increase below 4˚C, then ice wouldn’t float to the surface of water
bodies and insulate the seething life below from the sub-zero temperatures of
a hostile environment. This is shown in Figure 4. The mass of water is also the
reference for the metric system. 1 Litre of water at 4˚C weighs 1 kg. 1 Litre is
10cm by 10cm by 10cm. We can use this fact to our advantage when calibrat-
ing our volumetricware.
Figure 4: The density of water
The temperature of maximum density is 4˚C, a feature that allows cooling water to fall to the bot-
tom of lakes and prevents eutrophocation, and freezing water to float, thereby trapping heat (albeit
chilly 4˚C) in the water and thereby preserving life on land. It’s very lucky for us. It’s no coinci-
dence that water weighs 1000g at 4˚C; the metric system is based on the density of water. At room
temperature (25˚C) water weighs 997g. In most field conditions (between 10˚C-15˚C) the water is
so close to 1000g we recommend directly translating its mass to volume when calibrating.
C H A P T E R 2 : T H E ORY