Temperature and DO

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Temperature and DO

• Field Manual for Water Quality Education
• Ch.2 pp.18-24

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Temperature and DO

• Temperature
• A measure of heat
• Dissolved Oxygen (DO)
• The concentration of oxygen (gas) which is
  dissolved in water.
• Both are important individually and to one another

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Why is Temperature Important?

• Most aquatic organisms are poikilothermic
  (cold-blooded), which means they dont
  internally regulate their core body temperature.
• The rate of many chemical reactions increases at
  higher temperatures.
• Oxygen solubility

4
Temperature Influences

• the amount of oxygen that can be dissolved in
  water
• the rate of photosynthesis by algae and larger
  aquatic plants
• the metabolic rates of aquatic organisms
• the sensitivity of organisms to toxic wastes,
  parasites, and diseases.

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Temperature - Units

• Fahrenheit (F), Celsius (C), Kelvin (K)
• Celsius (C) used for most science (SI unit)
• a.k.a. centigrade, where centi- hundredth
• Water Freezes at 0C 32F 273.15 K
• Water Boils at 100C 212F 373.15 K

0C
100C
32F
212F
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Temperature - Units

• Conversion Factors
• (F 32)
• 1.8
• F (C x 1.8) 32

C
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Temperature Q10 Rule

• General rule which predicts
• Growth rates of cold-blooded aquatic organisms
  and many biochemical reaction rates will double
  for every 10C (18F) temperature increase within
  their "preferred" range.

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Fig.3.15, p.41
9
Temp Biological Effects
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Temperature Standards
Rolling 7-day average of maximum daily
temperatures
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Temperature Deep Cr (Clack)
21.3
21.0
20.9
20.9
20.9
20.5
20.2
19.4
7-day max AVG 20.6C
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Temperature Causes

• Loss of riparian shading
• Warm water inputs
• Retention ponds
• Municipal or industrial wastewater
• Stormwater runoff
• Groundwater inputs
• Weather
• Air temperature, cloud cover, day length
• Turbidity

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Temp. Testing Procedure

• At the site where the other water quality tests
  are being performed, lower the thermometer four
  inches below the water surface.
• Keep the thermometer in the water until a
  constant reading is attained (approximately two
  minutes).
• Record your measurement in Celsius.
• Repeat the test approximately one mile upstream
  as soon as possible.
• Subtract the upstream temperature from the
  temperature downstream using the following
  equation temp. downstream - temp. upstream
  temp. change
• Record the change in temperature.

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DO Solubility

• Inverse, non-linear relationship to temperature
• Decreases with decreasing barometric pressure
• Weather, elevation
• High salinity reduces solubility

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DO Solubility
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DO Units

• Concentration
• mg/L µg/mL ppm (parts per million)
• Percent Saturation
• DO Sat.

Measured DO (mg/L) Solubility (mg/L)
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DO Sources

• Photosynthesis
• Influenced by sunshine, temperature, water
  velocity
• Atmospheric Re-aeration
• Turbulent mixing
• Water velocity and depth
• Oxygen deficit
• Inflow of oxygenated water

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DO Sinks

• Respiration
• Greatest source of DO loss in summer
• Biochemical Oxygen Demand (BOD)
• Decomposition of organic wastes
• Standard measure is 5-day BOD BOD5
• Nitrification (NBOD)
• NH3 O2 NO3

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DO Diel Fluctuations
PM
Dissolved Oxygen
AM
Time of Day
21
DO Standards
22
DO and Temp Data Quality
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Measuring DO and Temp

• Measure Immediately - In Field
• Measure Both at Same Time
• Recording Time is Crucial
• Sample Collection
• Below surface 4 inches (or ½ way to bottom of
  shallow stream)
• Cap DO bottle underwater

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Percent Saturation

• The percent saturation of water with dissolved
  oxygen at a given temperature is determined by
  pairing temperature of the water with the
  dissolved oxygen value, after first correcting
  your dissolved oxygen measurement for the effects
  of atmospheric pressure. This is done with the
  use of the correction table and the percent
  saturation chart.

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Percent Saturation (Fig.3.1, p.21)

• To calculate percent saturation, first correct
  your dissolved oxygen value (milligrams of oxygen
  per liter) for atmospheric pressure. Look at the
  correction chart. Using either your atmospheric
  pressure (as read from a barometer) or your local
  altitude (if a barometer is not available), read
  across to the right hand column to find the
  correction factor. Multiply your dissolved oxygen
  measurement by this factor to obtain a corrected
  value.

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Fig.3.2, p.22 Level of Oxygen Saturation Chart
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Example

• Let's say that your dissolved oxygen value was 10
  mg/L, the measured water temperature was 15'C,
  and the atmospheric pressure at the time of
  sampling was 608 mmHg. From the table in Figure
  8, the correction factor is ___ percent, which
  multiplied by ___mg/L gives a corrected dissolved
  oxygen value of___mg/L. Drawing a straight line
  between this value and 15C gives a percent
  saturation of about ___ percent.How might you
  interpret these results?

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Fig.3.3, p.23 D.O. Test Kit Items