FIELD METHODS IN ENVIRONMENTAL GEOLOGY

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FIELD METHODS IN ENVIRONMENTAL GEOLOGY GEOS 3110
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WATER QUALITY MEASUREMENTS
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Water quality measurements
- Introduction - Parameters to be measured -
Methodology
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Introduction
- determine the chemical states of natural
waters - understand how waters will react with
minerals, gases and fluids of the Earth?s crust
and hydrosphere - define relationships between
drainage basins - water managers and regulators
commonly make these types of measurements to
determine the flux of contaminants into
drinking water supplies.
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Water quality measurements
- Introduction - Parameters to be measured -
Methodology
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Parameters
- Temperature
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Temperature
- controlling variable once it begins to change,
so do other parameters - variable of interest
- tracking a warm plume - differentiating
two carst systems - delineating recharge and
discharge areas Measuring devices -
thermometer - during other parameters
determination which require temperature
calibration
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Parameters
- Temperature - pH
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pH
H2O can act as both a proton donor and acceptor
for itself. A proton can be transferred from one
water molecule to another, resulting in the
formation of one hyroxide ion (OH-) and one
hydronium ion (H3O).
2H2O(l) H3O(aq) OH-(aq)
This is called the autoionization or
dissociation of water. This equilibrium can also
be expressed as H2O(l)
H(aq) OH-(aq)
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The pH scale
DEFINITION The negative logarithm of the
hydrogen ion activity in water is called the pH
of the water.
pH - log H From this it is obvious
that at 25 C
pH lt 7
solution is acidic
pH 7
solution is neutral
pH gt 7
solution is basic
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Parameters
- Temperature - pH - Turbidity
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Turbidity
DEFINITION Turbidity is a measure of the lack
of clarity of the water sample. High turbidity
makes it difficult to treat water for
microbial contaminants, and therefore is
regulated in drinking water supplies by the
EPA. Measuring devices - portable
turbidimeter (Hach 2100 P)
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Parameters
- Temperature - pH - Turbidity - Dissolved
gases
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Dissolved Gases
May affect important characteristics such as its
corrosivity, taste, toxicity, potability,
solubility of other components in contact with
the sample. Dissolved gases may include -
oxygen - carbon dioxide - hydrogen sulfide -
methane, etc. Dissolved oxygen (D.O.) is
importantfor determining the solubility of metals
and for the viability of fish and other
organisms. Measuring devices - YSI-85 DO meter
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Parameters
- Temperature - pH - Turbidity - Dissolved
gases - Electrical conductivity
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Electrical Conductivity
DEFINITION Electrical conductivity
(conductance) is a measure of the ability of a
water to conduct electricity. In general, the
higher the concentration of dissolved salts in
the water, the easier it is for electicity to
pass through the water. Measuring devices -
YSI-85 DO meter
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Parameters
- Temperature - pH - Turbidity - Dissolved
gases - Electrical conductivity - Nitrates
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Nitrates
Nitrate concentration is one of the principal
contaminants in urban surface water. The
maximum concentration allowed in drinking water
is 10 ppm. In general, nitrates represent a
remnant of fertilizer application. Measuring
devices - spectrophotometer (colorimeter)
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Water quality measurements
- Introduction - Parameters to be measured -
Methodology
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pH Methodology
1. CALIBRATION 2. TAKING THE MEASUREMENT
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pH Calibration
1. Press MODE key until the pH mode indicator is
displayed 2. Place the electrode(s) into the 4.0
buffer. 3. Press CAL key. CALIBRATE will be
displayed above the main field. After the
calibration slope is displayed, P1 will be
displayed in the lower field. P 1 indicates that
the meter is ready to accept the first
buffer point. 4. When the electrode is stable,
the meter will beep and READY will be
displayed along with the temperature corrected
value for the buffer (flashing). Press YES key
to accept this point. 5. The display will remain
fixed momentarily, then P2 will be displayed
in the lower field. The meter is now ready for
the second buffer (7.0).
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pH Calibration
6. Rinse the electrode(s) and place them in the
second buffer (7.0). Wait for a stable pH
reading (the meter will beep) and for READY to
be displayed. Press the YES key to accept the
second point. The electrode slope will be
displayed in pH units. SLP will appears in the
lower field. The advances to the measure mode and
MEASURE appears above the main display. The
meter is now ready to take pH measurements. The
EC10 retains this calibration until a new
calibration is entered or until power is
disconnected from the instrument. NOTE To
view the current slope value at any time, press
CAL key. Press the MODE key to return to measure
mode without changing the current
calibration. Always use buffer solutions that
have a pH in the same range of measurements
expected.
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pH Measurement
1. Take the reading directly in the field or
immediately after sampling. 2. Use the MODE
button to switch between different types of
readings (pH, mV, T) 3. Record the values in
your field notebook. NOTE The pH measurement
should be accompanied by a temperature
measurement. EC10 pH meter records a pH already
temperature compansated.
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Turbidity Methodology
1. CALIBRATION 2. TAKING THE MEASUREMENT
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Turbidity Methodology
CALIBRATION The 2100P Portable Turbidimeter was
been calibrated at the factory and does not
require recalibration before use. TAKEING THE
MEASUREMENTS 1. Collect a representative sample
in a clean container. Fill a sample to the
line (about 15 mL), taking care to handle the
sample cell by the top. Cap the cell. 2.
Wipe the cell with a soft, lint-free cloth to
remove water spots and fingerprints. 3.
Press I/O - the instrument will turn on. Place
the instrument on a flat surface. Do not hold
the instrument while making readings.
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Turbidity Methodology
4. Put the sample cell in the instrument cell
compartment so the diamond or orientation
aligns with the raised orientation mark in
front of the cell compartment. Close the
cover. 5. Automantic range by pressing the RANGE
key. The display will show ?AUTO RNG? when
the instrument is in automatic range
selection. 6. Press READ - the display will show
?----NTU? then the turbidity in NTU (
Nephelometric Turbidity Units, a standard
measurement). Record the turbidity after the
lamp symbol turns off. NOTE Always wipe any
fingerprints, spots, etc. from the outside of
the vial, and be sure to close the
vial-compartment lid when taking a measurement.
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D.O. Conductivity Methodology
1. CALIBRATION 2. TAKING THE MEASUREMENT
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D.O. Calibration
To accurately calibrate the YSI Model 85 you
will need to know the approximate altitude of the
region in which you are located. 1. Ensure that
the sponge inside the instrument?s callibration
chamber is wet. Insert the probe into the
calibration chamber. 2. Turn the instrument on
by pressing the ON/OFF button on the front of
the instrument. Press the MODE button until
dissolved oxygen is displayed in mg/l or .
Wait for the dissolved oxygen and temperature
readings to stabilized (usually 15 minutes
is required). 3. Use two fingers to press and
release both the UP ARROW and DOWN ARROW
buttons at the same time. 4. The LCD will prompt
you to enter the local altitude in hundreds of
feet. Use the arrow keys to increase or
decrease the altitude. When the proper
altitude appears on the LCD, press the ENTER
button once.
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D.O. Calibration
5. The Model 85 should now display CAL in the
lower left of the display, the calibration
value should be displayed in the lower right of
the display and the current reading (large
display) is stable, then press ENTER button.
The display should read SAVE then should return
to the Normal Operation Mode. NOTE Each
time the Model 85 is turned off, it may be
necessary to re-calibrate before taking
measurements. All calibration should be
completed at a temperature which is as close as
possible to the sample temperature. Dissolved
oxygen readings are only as good as the
calibration.
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Conductivity Calibration
System calibration is rarely required because of
the factory calibration of the Model 85.
However, from time to time it is wise to
check the system calibration and make adjustments
when necessary.
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D.O Conductivity Measurements
1. Press the ON/OFF button to turn on the
machine. The instrument will activate all
segments of the display for a few seconds, which
will be followed by a self-test procedure and
will last for several more seconds. The Model
85 will display the cell constant of the
conductivity probe when the self-test is
complete. The Model 85 is designed to provide
six distinct measurements - Dissolved Oxygen -
a measurement of oxygen in percent of
saturation - Dissolved Oxygen mg/L - a
measurement of oxygen in mg/L - Conductivity - a
measurement of the conductive material in the
liquid sample without regard to temperature -
Specific Conductance - also known as compensated
conductivity which automatically ajusts the
reading to a calculated value which would have
been read if the sample had been at 25 C. -
Temperature - which is always displayed -
Salinity - a calculation done by the instrument
electronics, based upon the conductivity and
temperature readings.
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D.O Conductivity Measurements
2. To choose one of the measurement modes above,
simply press and release the MODE button.
Carefully observe the small legends at the far
right side of the LCD. If the instrument is
reading Specific Conductance the large numbers on
the display will be followed by either a uS or an
mS (micro Siemens). flashing on and off. If the
instrument is reading Conductivity (not
temperature compensated) the large numbers on the
display will be followed by either a uS or an
mS. Additionally the small portion of the display
will show the C (temperature) NOT flashing. If
the instrument is reading Salinity the large
numbers on the display will be followed by a ppt
(parts per thousand).
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Nitrates Methodoloy
The spectophotometer uses indicator compounts to
determine the concentration of the desired
species. Use of the Hach Test kit involves
mixing a pre-measured amount (a ?pillow?) of the
indicator compound with a measured amount of
sample water, then measruring the absorption of
light of a particular wavelength. After mixing
and delay of reaction, a color will appear (for
nitrates it is amber color), the darkness of
which is measured in the spectophotometer. The
sample is introduced to the spectophotometer
via a pour-through-cell aparatus, to minimize
interferece?s from sample handling. The
CALIBRATION is working in the same way as the
actual reading, but have to be done on samples
with known concentration in nitrates. Two such
kind of samples will be used, and the real values
will be obtained by a linear interpolation
between the standard samples.
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Nitrates Measurement
1. Enter the stored program number for high range
nitrate nitrogen (NO3--N). Press 355 ENTER.
The display will show Dial nm to 500. 2. Rotate
the wavelength dial until the small display
shows 500 nm . When the correct wavelength
is dialed in, the display will quickly show
Zero Sample, then mg/L NO3--N HR. 3. Fill
a sample cell with 25 mL of sample. 4. Add the
contents of one NitraVer 5 Nitrate Reagent Powder
Pillow to the cell (the prepared samples).
Stoppper. 5. Press SHIFT TIMER. Shake the cell
vigorously until the timer beeps in one
minute. 6. When the timer beeps, press SHIFT
TIMER A five minute reaction period will
begin.
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Nitrates Measurement
7. Fill another sample cell with 25 mL of sample
(the blank). 8. When the timer beeps, the
display will show mg/L NO3--N HR. Place the
blank into the cell holder. Close the light
shield. 9. Press ZERO. The display will show
Zeroing ? then, 0.0 mg/L NO3--N HR. 10.
Remove the stopper. Place the prepared sample
into the cell holder.Close the light
shield. 11. Press READ The display will show
Reading ? then the result in mg/L nitrate
nitrogen (NO3--N) will be displayed. 12. Press
SHIFT STORE to store the result. Type in the
sample number and record the value in your
notebook.
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Field Procedures
1. Collect Sample (a) using sample bottle,
bucket, or long-handled sampler collect 200-500
ml sample (b) place in 500 ml amber glass
bottle, cap the bottle, bring to analysis table
2. Measure Chemical State as soon as possible
measure the following in the sample (a)
temperature (by thermometer or meter) (b)
pH (follow pH-meter procedure) (c)
dissolved oxygen content (equivalent to Eh) 3.
Prepare Filtered Split (a) obtain a filter
funnel and filter paper (fold this in 1/4, spread
and place in funnel) (b) fill filter cone
2/3's full (c) repeat (once) 4. Measure
Turbidity (a) fill turbidity sample vial to
bottom of white line (vial has white line around
top with upside-down triangle on it,
avoid touching sides!) (b) follow the
turbidity measurement procedure 5. Measure
Nitrate Content (a) pour 25 ml of filtered
sample into clear, glass-stoppered bottle (25 ml
is marked on bottle side) (b) follow
colorimetry procedure 6. Measure Electrical
Conductivity (can be done at any point during
lab, in stream or in sample) (a) use the
YSI-85 DO meter (b) press MODE'' button
until display shows units of micro-Siemens (S)
(c) be sure probe is fully immersed in
unfiltered sample or stream (or display will show
zero) (d) record reading when it becomes
stable