EPA/600/4-89/030
METHODS MANUAL FOR
PERDIDO BAY CITIZENS MONITORING
PROGRAM
Prepared By
David A. Flemer
Environmental Research Laboratory
ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
GULF BREEZE, FLORIDA 32561
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PREFACE
Citizens monitoring programs have become an important mechanism
to involve citizens in environmental decision-making processes and
provide data that are often otherwise unavailable to environmental
managers.1 This Methods Manual and its companion quality assurance/
quality control plan were developed in response to a request made by
the Friends of Perdido Bay, Inc. (FPB). This document is part of
the Gulf Breeze Laboratory's effort to support regional and local
technology transfer efforts in addition to direct research
activities.
The FPB plan to implement a citizens1 volunteer monitoring
project includes water quality and weather-based data. The
monitoring and other activities of the FPB form an important
component of the Agency's Perdido Bay Cooperative Management Project
(PBCMP). The PBCMP is a pilot project of the Agency's Near Coastal
Waters Initiative and the pilot project is geographically within the
Agency's Gulf of Mexico Program. Thus, data obtained by the
citizens volunteer monitoring project will be of interest to the
local community and to various levels within the Agency.
The technical documents described herein are a key to a
successful monitoring project. However, no manual is a substitute
for experience. Therefore, to optimize on the investment (e.g., the
citizens time and enthusiasm and limited Agency resources), it is
essential that all interested parties acknowledge the continuing
need for citizen training with regard to environmental monitoring.
¦'•Directory of National Citizen Volunteer Environmental Monitoring
Programs, EPA 503/9-88-001, U.S. EPA, Office of Water, Washington,
DC.
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DATE: April 15, 1989
Standard Operating Procedures
Methods Manual for
Perdido Bay Citizens Monitoring Program
INTRODUCTION
This manual contains standard operating procedures (SOP's) for
the measurement of dissolved oxygen (DO), Secchi disk, a measure of
light penetration, temperature and salinity. Do not be over-
whelmed by the detail in these instructions; they are sequential, -
just follow the steps. With training you will be able to perform
the measurements without a line by line checking of instructions.
The instructions are no more complicated in many respects than
programming your VCR or operating a digital home microwave oven!
Protocol for Dissolved Oxygen
Use
Dissolved oxygen in milligrams per liter (or parts per million
- ppm) is measured in the field with a YSI model 57 oxygen meter
calibrated periodically (see Quality Assurance and Quality Control
Procedures) against standard analyses by the Winkler technique.
The oxygen meter is air calibrated in the field. Note: a salinity
measurement is required as input before dissolved oxygen can be read
on the Model 57 system.
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Operating Instructions
Instructions are adopted from the YS1 Model 57 Oxygen Meter
Manual with notes and additional precautions provided. These
instructions are involved and require careful reading and
familiarity with the instrument. The instrument is rugged but avoid
excessive shock (e.g., dropping it on dock or bottom of boat). It
can be operated in the rain but as a precaution cover the
instrument with a large plastic bag during heavy rain. The
instructions are divided into three (3) steps which are described
below. However, logic tells us that one must prepare the sensor
(probe) before the instrument is functional. For simplicity, these
instructions assume that you have gone through the numerous steps to
prepare the probe and are ready to take the oxygen meter to the
field. Therefore, the instructions are summarized as follows:
Step l. Battery check before taking instrument to the field.
Step 2. Calibration
Measurement
General Care
Step 3. Probe preparation.
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STEP 1. Before taking instrument to the field, check red-line
reading, and batteries including magnetic stirrer batteries.
STEP 2. Calibration, measurement and general care.
1. CALIBRATION
A. Switch instrument to OFF and adjust meter mechanical zero.
B. Switch to RED LINE and adjust.
C. Prepare probe for operation, plug into instrument, wait up to 15
minutes for probe to stabilize. (Keep in shade in air).
D. Switch to ZERO and adjust.
E. Adjust SALINITY knob to FRESH.
F. Switch to TEMP and read (if boatrocking causes needle to swing,
then take average but note this event on data sheet notes) .
6. Use probe temperature and true local atmospheric pressure (or
feet above sea level) to determine correct calibration values from
Table I and II. (See pages 13 and 14 of Manual) . (Disregard Table
II - you are "at sea level".)
EXAMPLE: Probe temp = 21 °C. From Table I the calibration value for
21°C is 9.0 PPM.
H. Switch to desired dissolved oxygen range 0-5, 0-10, or 0-20 and
with calibrate control adjust meter to correct calibration value
determined in Step G.
NOTE: It is desirable to calibrate probe in a high humidity
environment. See instruction manual for more detail on calibration
and other instrument and probe characteristics. Thus, at this stage
keep probe in bottomless plastic bottle with damp cotton).
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2. MEASUREMENT
A. Adjust the SALINITY knob to the salinity of the sample. (NOTE:
you must take a salinity measurement from the water sample collected
from the Bay at a known depth. If you have a salinity meter with
probe (e.g., YS1 Model 33), then tape salinity probe to D.O. probe
and tie the two (2) probes and cords to a third support line .that is
counter-weighted with a kilogram lead sinker. Mark support line as
described for Secchi disc. Do not attache this heavy weight
directly to electrical cable(s). Salinity probe should be separated
by 6 inches from metallic D.O. probe, otherwise you may get an
erronerous salinity reading because of electrical interference.
B. Place the probe and stirrer in the Bay and switch the STIRRER
control to ON.
C. When the meter has stabilized switch to the appropriate range
and read D.O. (Rocking boat may cause needle swings so take
average and record. Note on data sheet if needle was swinging
(e.g., between 5.0 and 5.8 mg/L if so, your best estimate of the
average value is 5.4 mg/L).
D. Record data to nearest tenth of a mg/L (e.g., 6.1). Note: read
scale on meter that matches RANGE SELECTOR SWITCH.
E. We recommend the instrument be left on between measurements to
avoid necessity for repolarizing the probe; turn to red line and
turn off stirrer (it uses up the battery power rather quickly).
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3. GENERAL CARE
A. Replace the instrument batteries when unable to adjust to red
line. Use (2) Everready No. 935 "C" size or equivalent. Keep a set
of batteries on hand.
B. In the BATT CHECK position the voltage of the stirrer batteries
is displayed on the red 0-10 scale. Do not discharge below 6.0
Volts. Recharge for 14-16 hrs. if instrument is supplied with a
YSI No. 5728 charger or replace batteries as needed.
C. Membranes will last indefinitely, depending on usage. Average
replacement is 2-4 weeks. Probe should be stored in humid
environment to prevent drying out.
D. Air calibrate hourly, or more often if calibration value drifts
from earlier determination. Amount of drift is meter-specific
including how well the membrane was prepared.
E. Before putting instrument away, the probe assembly should be
rinsed with tape water to remove corrosive sea salt.
STEP 3. Probe Preparation
ALL PROBES ARE SHIPPED DRY - YOU MUST FOLLOW THESE INSTRUCTIONS
1. Prepare the electrolyte by dissolving the KC1 crystals in the
dropper bottle with distilled water. Fill the bottle to the top.
2. Unscrew the sensor guard or stirrer unit from the probe and then
remove the "O" ring and membrane. Thoroughly rinse the sensor with
KC1 solution. (See Figure 1).
3. Fill the probe with electrolyte as follows (this will take
practice):
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A. Grasp the probe in your left hand. When preparing the YS1 5739
probe the pressure compensating vent should be to the right (for the
right-handed). Successively fill the sensor body with electrolyte
while pumping the diaphragm with the eraser end of a pencil or
similar soft, blunt tool. Continue filling and pumping until no
more air bubbles appear. (With practice you can hold the probe and
pump with one hand while filling with the other.) When preparing
the YS1 probes, simply fill the sensor body until no more air
bubbles appear.
B. Secure a membrane under your left thumb. Add more electrolyte
to the probe until a large meniscus (dome of liquid) completely
covers the gold cathode (sensor). NOTE: Handle membrane material
with care, keeping it clean and dust free, touching it only at the
ends.
C. With the thumb and forefinger of your other hand, grasp the free
end of the membrane.
D. Using a continuous motion stretch the membrane UP, OVER, and
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DOWN the other side of the sensor. Stretching forms the membrane to
the contour of the probe. (This looks easy but it is not for most
people; it requires nimble fingersl). The membrane often becomes
electrostatically charged and becomes somewhat difficult to control.
E. Secure the end of the membrane under the forefinger of the hand
holding the probe.
F. Roll the "0" ring over the end of the probe. There should be no
wrinkles in the membrane or trapped air bubbles, some wrinkles may
be removed by lightly tugging on the edges of the membrane beyond
the "0" ring.
G. Trim off excess membrane with scissors or sharp knife. Check
that the stainless steel temperature sensor iis not covered by excess
membrane.
4. Shake off excess KC1 and screw probe into stirrer.
5. A bottomless plastic bottle is provided with the YSI 5739 probe
for convenient storage. Place a small piece of moist towel or
sponge in the bottle and insert the probe into the open end. This
keeps the electrolyte from drying out. As an alternative the YSI
5739 probe can be stored in a wide mouth bottle containing about 1"
water.
6. Membranes will last for days to months, depending on usage.
Average replacement is 2-4 weeks. However, should the electrolyte
be allowed to evaporate and an excessive amount of bubbles form
under the membrane, or the membrane become damaged, thoroughly flush
the reservoir with KCI and install a new membrane. (If bubble is
larger than the diameter of a No. 2 lead of a pencil (about 3 mm),
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then replace membrane).
7. Also replace the membrane if erratic readings are observed or
calibration is not stable.
8. "Home brew" electrolyte can be prepared by making a saturated
solution of reagent grade KCI and distilled water, and then diluting
the solution to half strength with distilled water. Adding two
drops of Kodak Photo Flo per 100 ml of solution assures good wetting
of the sensor, but is not absolutely essential.
9. The gold cathode should always be bright and untarnished. To
clean, wipe with a clean lint-free cloth or hard paper. NEVER USE
ANY FORM OF ABRASIVE OR CHEMICAL. Rinse the sensor several times
with KCI, refill, and install a new membrane.
10. Some gases contaminate the sensor, evidenced by discoloration
of the gold. If the tarnish cannot be removed by vigorous wiping
with a soft cloth, lab wipe, or hard paper, return the probe to the
factory for service.
11. If the probe has been operated for extended periods with a
loose or wrinkled membrane the gold cathode may become plated with
silver. In this event return the probe to the factory for
refinishing.
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Standard Operating Procedure
Light Penetration
Secchi Disc
USE:
The Secchi disk is lowered into the water slowly until it is
no longer visible, then slowly raised until barely visible. Record
the average value to nearest tenth of meter (e.g. 1.30 and 1.34
meters equals 1.3 meters). The secchi disc may be also used to
determine water depth.
Conditions of Use
1. Deploy on shady side of boat. Note: at high noon in June your
boat will not cast a shadow except directly under the boat but the
boat will cast a shadow at 3:00 p.m. if it is sunny. However, at
high noon the sun angle offers less glare than at other times, thus
you will be necessity read at this time on the sunny side of the
boat.
2. Do not make readings with sun-glasses (shades) on.
3. Do not read until 2 hrs after sun rise or 2 hrs before sun set.
Preferably read between 9:00 am and 3:00 pm.
Temperature
Water temperature (surface)
Dial or stem thermometer:
Use
1. Immerse bulb or sensor 2.5 cm (about 1.0 inch) below surface;
hold in position in shaded area for about 30 seconds or until
reading is stable. Read while immersed to nearest small graduation
(it varies with thermometer but frequently equals one (1) degree.
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Note: direct sun light on sensor will bias reading upwards.
2. Record other ancillary data on data sheet as indicated.
Air temperature
Dial or stem thermometer:
Use
1. Hold in shade of your body in open area on station (e.g., end of
pier, boat, or yard, if in inland station). Record to nearest whole
degree Celsius (e.g., 25.0 C) after reading stabilizes. NOTE: the
term Celsius is now used instead of centigrade.
2. Record other ancillary data on data sheet as indicated.
Condition of use:
Thermometers are delicate instruments. Do not leave exposed to
full summer sun and attempt to use because it could damage
instrument and it often takes excessive time for thermometer to
equilibrate when deployed.
Glass stem thermometers should be provided with a metal case to
prevent breakage.
Thermistor:
IF you have access to a Y.S.I, oxygen or salinity, conductivity
and temperature meter, then the temperature can be read by following
instructions in manual.
USE
Deploy thermistor probe which is built into the oxygen sensor
as per dissolved oxygen measurement. An advantage is that this
method can conveniently measure dissolved oxygen and temperature at
depth.
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Salinity
Introduction:
The salt content of sea water is usually expressed as its
salinity or S o/oo (part per thousand or ppt), a convention which
approximates to the weight in grams of dry salts contained in 1000
grams (roughly one liter) of seawater. Open ocean water's salinity
often approximates 35 to 37 ppt but in bayous and estuaries it is
diluted and may range from zero (actually a trace) in a the river-
end of an embayment to about 25 to 30 ppt near the mouth or inlet
(e.g., Perdido Pass). Salinity is known as a "Master Factor" in
marine biology and is a key factor that determines the distribution
of the biota; salinity contributes to and affects the chemistry of
marine waters (e.g., see dissolved oxygen measurement for an example
of importance of salinity.
Operating Instructions:
I. LaMotte Chemical Titration Kit
These instructions are taken from ^the LaMotte salinity
titration kit. The titration method utilizes chemical reactions and
a colored precipitate to determine the amount of chloride-like
materials in the sample. The so-called chloride content or
chlorinity is roughly proportional to the total salt content or
salinity.
step l. Carefully read the instruction manual for the LaMotte
Direct Reading TITRATOR before performing the titration described
below. The TITRATOR is calibrated in parts per thousand (ppt. or
0/00) Salinity. Each minor division on the TITRATOR scale equals
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0.4.ppt. salinity. NOTE: Silver nitrate is toxic, especially if
swallowed. Thus, it must be kept out of reach of children.
Step 2. See test procedure supplied with the kit. The procedure is
reproduced here with some additional guidance or pointers.
TEST PROCEDURE
1. Fill the titration tube to the 10 ml. line with distilled water.
Tap water with no chloride content may be used if necessary. With
practice you may slightly overfill the mark and hold the titration
tube so slight flicks of the wrist will spill a few drops. This
procedure will allow you quickly to fill to the mark precisely.
2. Fill the 1.0 ml burette (scale printed in black) with the water
to be tested. Hold the tip of the burette in the water sample and
slowly withdraw the plunger until the tip is opposite the 0 mark.
Wipe any excess sample water from the tip of the filled burette with
tissue paper. If a bubble is pulled into the burette, push the
plunger to the bottom and repeat.
3. Dispense 0.5 ml of the sample water into the titration tube by
slowly pressing the plunger until the tip is opposite the 0.5 mark.
Then discard the water sample remaining in the burette by forcing
plunger to bottom of the barrel of burette. NOTE: this 1.0 ml
burette is used in other tests. Otherwise a 0.5 ml burette could be
used. If you forget, and add the full 1.0 mL, then your results
will be in error by a factor of 2.
4. Add 3 drops of Salinity Indicator Reagent A to the titration
tube. Cap and gently shake to mix the contents.
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5. Fill the Direct Reading TITRATOR (scale printed in blue) with
Salinity Titration Reagent B. Insert the TITRATOR in the center
hole of the titration tube cap. Do not reverse burets because
erroneous results will occur.
6. While gently swirling the tube, slowly press the plunger to
titrate until the color of the solution changes from yellow to pink-
brown. Read the test result directly in ppt. salinity where the
plunger tip meets the TITRATOR scale. NOTE: high salinity values
will require that you refill the burette and add more Regent B.
EXAMPLE: Plunger tip is 3 minor divisions below line 10. The test
results is 10 plus (3 divisions X 0.4) equals 11.2 ppt. Each small
division = 0.4 ppt.
Precaution: Contact with the Salinity Titration Reagent B will
cause a dark stain on the skin. Handle with care.
7. Record salinity value to nearest tenth (e.g., 17.4 ppt.)
8. Important ancillary data includes water temperature if the
density of the water is to be determined at a later time.
II. YSI Model 3 3 Salinity. Conductivity and Temperature Meter
YSI PortaW* 3-C-T,
SaMntty Mctar.
Modal 33
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This instrument is a field-proven system but as for all
electronic instruments, it must be handled with care. The
instrument actually measures the electrical conductance of the
sample. The probe consists of a plastic conductivity cell and a
precision thermistor temperature sensor combined in a single unit.
Salinity measurements are calibrated within the meter to electrical
conductance. Salinity values are manually temperature compensated
by direct dial (conductivity measurements are not temperature
compensated; however, a temperature function is provided on the
instrument to aid with calculation corrections). In tidal water,
where conductance is relatively high, the salinity measurement is
usually made with this instrument instead of conductance. In fresh
water, conductance is usually measured.
The measurement of salinity assumes the sample contains a
"standard" seawater salt mixture. In waters highly contaminated
with sulfates, halides (e.g., fluorides, bromides, chlorides) or
other highly conductive chemical forms (i.e., ions), errors will
result. This problem is addressed in the quality assurance and
quality control section.
Operation Procedure:
(This procedure omits the section in the manual that describes
measurement of conductance).
Step l. Measurement of Salinity.
1. Setup
(a) Adjust meter zero (if necessary) by turning the bakelite screw
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on the meter face so that the meter needle coincides with the zero
on the conductivity scale. Use a small screw driver or pocket
knife.
(b) Calibrate the meter by turning the MODE control to REDLINE and
adjusting the REDLINE control so the meter needle lines up with the
redline on the meter face. If this cannot be accomplished, replace
the batteries. Allow meter to warm up on Redline for 15 minutes.
(c) Plug the probe into the probe jack on the side of the
instrument.
(d) Put the probe in the solution to be measured. (See Probe
Use) .
2. Temperature
Set the MODE control to TEMPERATURE. Read the temperature on the
bottom scale of the meter in degrees Celsius. Allow time for the
probe temperature to come to equilibrium with that of the water
before reading usually 30 seconds will do.
3. Salinity.
(a) Transfer the temperature reading from Step 2 to the #C scale on
the instrument.
(b) Switch the MODE control to the SALINITY position and read
salinity on the red 0-40 °/oo meter range.
(c) Depress the CELL TEST button. The meter reading should fall
less than 2% (example: 0.01 x 20 - 0.4 ppt; if reading is 0.5, then
you have a measurement error). Clean the probe and re-measure.
Step 2. Probe use.
(a) Obstructions near the probe can disturb readings. At least two
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inches of clearance must be allowed from non-metallic underwater
objects. Metallic objects such as piers or weights should be kept
at least 6 inches from the probe. IF you inadvertently fill holes
in probe with mud, you will not get a true reading.
(b) Weights are attached to the cable of the YSI Probe. The YSI
Weights are supplied in pairs with a total weight of 4 ounces per
pair. Should it become necessary to add more weight to overcome
water currents, we suggest limiting the total weight to two pounds
(8 pairs). For weights in excess of two pounds use an independent
suspension cable. In either case, weights must be keep at least 6
inches away from the probe. ,
(c) Gentle agitation by raising and lowering the probe several
times during a measurement insures flow of specimen solution
through the probe and improves the time response of the temperature
sensor but read at desired depth because the oxygen probe has a
stirrer and does not need agitation on the line.
Step 3. Probe Calibration and Maintenance
• See Quality Assurance/Quality Control for calibration.
Also, a full discussion is provided in technical manuals.
* Maintenance
(a) Cleaning
When the cell test indicates low readings the probable cause
is dirty electrodes. Hard water deposits, oils and organic
matter are the most likely contaminants.
For convenient normal cleaning soak the electrodes for 5
minutes with a locally available bathroom tile cleaning
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preparation such as: Dow Chemical "Bathroom Cleaner",
Horizon Industries "Rally, Tile, Porcelain, and Chrome
Cleaner", Johnson Wax "Envy, Instant Cleaner", or Lysol Brand
"Basin, Tub, Tile Cleaner."
For stronger cleaning a 5 minute soak in a solution made of
10 parts distilled water, 10 parts isopropyl alcohol and 1
part HCI can be used. (It is recommended that a specialist
perform this procedure).
Always rinse the probe after cleaning and before storage.
CAUTION: Do not touch the electrodes inside the probe.
Platinum black is soft and can be scraped off.
If cleaning does not restore the probe performance, re-
platinizing is required.
CAUTION: Before proceeding to this step, contact your
Program Technical Advisors:
Dr. Jackie Lane
10738 Lillian Hwy.
Pensacola, FL 32506
(904-453-5488)
or
Dr. David A. Flemer
U.S. EPA
Environmental Research Laboratory
Sabine Island
Gulf Breeze, FL 32561
(904-932-5311)
(b) Re-Platinizing
Equipment Required -
(1) YSI #3140 Plantinizing Solution, 2 fl oz. (3% platinum
chloride dissolved in 0.025% lead acetate solution).
(2) YSI Model 33 or 33M S-C-T Meter.
(3) 50 ml glass breaker or equivalent bottle.
(4) Distilled water.
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Procedure -
(1) Clean the probe as in Section (a) - either method.
(2) Place the cell in the beaker and add sufficient YSI #3140
solution to cover the electrodes. Do not cover the top of
the probe.
(3) Plug the probe into the Model 33 or 33M, switch to the
X100 scale to platinize the electrode. Move the prove
slightly to obtain the highest meter reading and continue
platinizing for the approximate time shown below:
Meter Reading Time
/imhos/cm mS/m (minutes)
30,000 3,000 5
25,000 2,500 6
20,000 2,000 8
15,000 1,500 11
10,000 1,000 16
It is best to store conductivity cells in deionized water.
Cells stored in water require less frequent plantinization. Any
cell that has been stored dry should be soaked in deionized water
for 24 hours before use.
Step 4. Check Battery Condition
Replacement
Use two (2) D-signed alkaline Everready E95 or equivalent.
They provide about 200 hrs. of operation. This assumes that they
were "fresh" from the store!
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Water Sampling Device
(LaMotte Chemical)
Introduction
This water sampler (see Figure) has a removal inner tube which
is flused 10 times before the entire water sampler is filled, the
inner tubing begins filling immediately upon being submerged in the
water. If the wate sampler is lowered to the desired depth quickly
enough, only water from the desired depth will fill the inner
chamber.
Method
1. Make sure the inner collecting tube is in the center well of the
collecting device.
2. Attach weight to the bottom, and lower the sampler into the
water.
3. Lower the sampler quickly but make sure the rope is always taunt
and the sampler is upright.
4. When you feel the weight hit the bottom, stop lowering the
sampler.
5. Pull the sampler up about one (1) inch and allow the sampler to
fill completely with water. You will know when the sampler is full
when you do not see any more air bubbles. Wait about 15 seconds
after you see the air bubbles stop. Note the depth of the water
from the marked rope.
6. After 15 seconds, life the sampler from the water, making sure
to keep the sampler upright.
7. Remove the plastic center plug and lift out the inner glass tube
by pushing a cork with a handle into the glass tube.
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Water Sampling Device
Weight
Tubing
Thermometer
Clip
Collecting
Tube
Inner
Chamber
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Appendix
Perdido Bay Citizens Monitoring Program Water Quality Notes
Dissolved Oxygen
Dissolved oxygen is a critical factor for the survival and well
being of aquatic life (e.g., fishes and their food web require
dissolved oxygen but anaerobes, i.e., some microbes including
nitrifying bacteria are poisoned by dissolved oxygen).
The salinity of the water affects the solubility of dissolved
gases (e.g., dissolved oxygen) and is why it is important to
measure salinity before dissolved oxygen.
For air calibration the temperature vs. dissolved oxygen value
is printed on the back of the meter and is given in Table 1 of the
manual. It is convenient to type or print with indelible ink this
scale and tape to top of meter (e.g., average seasonal range here is
from 10 to 34°C; a very cold winter will require you to read back of
meter).
The operating procedure recommends air calibration daily in the
manual. It is better to do it hourly but the stability of
calibration is a function of how well you put the membrane on the
probe and battery strength. If the reading drifts more than 0.2 ppm
in 5 minutes, then you should replace membrane and repeat the
measurement. It should hold steady.
Note: dissolved oxygen readings usually will be higher near the
surface than near the bottom, especially during the summer. If
strong vertical stratification exists in salinity (e.g., salinity
reads 10 °/oo at 0 m, 11 °/oo at 1 m, 11.5 °/oo at 1.2m, 20 °/oo at
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1.5m and 20 °/oo at 1.8 and 20.5 at 3m), then you might expect for
the dissolved oxygen concentration from 1.8m (big change in salinity
with depth) and deeper to read lower. During the summer, the deeper
water may read less than 1.0 mg/Liter, and the concentration may
approach or reach 0.0 mg/liter. Algae or other submerged plants may
cause the D.O. reading to reading quite high (e.g., 10 mg/liter at
summer temperatures would generally be a high reading). We
recommend the oxygen membrane approach to measureing dissolved
oxygen over the Winkler method ("wet" chemistry). The stain in the
paper mill effluent often masks the color change in the winkler
test. Also, strong acids and bases are used which are hazardous and
require additional training.
Secchi Disk
Additional Information:
Background
"The Secchi disk is a device used to visually measure the clarity of
nature waters. It is usually a circular white disk of 30-cm
diameter that is lowered vertically into the water, disk plane
horizontal, until it disappears from sight. The depth of
disappearance of the disk is inversely proportional to the average
amount of organic and inorganic materials including color along the
path of sight in the water. The technique, systematically studied
by the Italian physicist Angelo Secchi (1866) is, interestingly,
still in use today. It is one of the few instruments remaining in
the armory of modem science for which the visual sense of the human
operator is an integral part of the measurement procedure.
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The Secchi disk procedure is valued by many aquatic biologists
as a useful and informal visual index of the trophic activity of a
lake or oceanic region. The accumulated listings of the depth of
disappearance of the disk, as a function of season and location
within a given lake, estuarine, or coastal region can over the years
provide a readily understood and quite useful record of the growth
and decay of aquatic plant life in such media. It is also useful
in tracking visually the movements of suspended detritus and the
migration of sediment influxes from tributary streams and rivers.
In these modes of its use the white disk continues, just as it did
in Secchi's day and before, to be a handy, robust, visual indicator
of the variations of water clarity and biologic activity."
Adopted from R.W. Preisendorfer. 1986. Secchi disk science:
visual optics of natural waters. Limnology and Oceanography
31(5):909-926.
Construction:
The disk diameter typically is 20 or 30 cm (11.8 inches) and
varies from all white to a surface showing alternate black and white
quadrates. What really matters is to choose a size and surface
pattern and use the chosen design in all of one's work. It enhances
comparability of data. (D. Flemer, US EPA Environmental Research
Laboratory, Gulf Breeze, FL) uses an all white 30 cm Secchi disk).
The disk can be bought from a scientific supply house (e.g., Ward's
Scientific) or fabricated.
A stainless steel or brass I-bolt is attached to the center of
the disk (1/4 inch thick white plexiglass backed up with 1/4 inch
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Page 24 of 28
black plexiglass). The threaded portion of the I-bolt should
protrude below the disk far enough to hold a small piece of molded
lead (e.g., 3.0 kilograms or 6.6 lbs. for Perdido Bay; the weight is
a function of water current strength) . Attach a length of rope
(e.g., 15 ft. or 4.6 meters; polyproprelene or nylon parachute size
chord will do) to the I-bolt with a bowline knot whose knot is
within several inches of the I-bolt. Wrap the knot with "marine
wire" or plastic electrical tape so the knot will not become untied!
Place Secchi disk in a vise held by the I-bolt and gently pull
firmly on the rope; it helps to have another person pull firmly on
rope and mark off from surface of disk using a meter stick and an
indelible magic marker at intervals of 10 cm up to 3.0 meters. Mark
each full meter location (e.g., 1,2 and 3) with a piece of heavy
thread that is pushed through the rope and tied off with loose ends
clearly viable (e.g., 1.0 inch, or 2.5 cm). IF you are not colored
blind you might supplement a different color magic marker for the
thread but thread should last longer. Note: electric tape often
slips on the line and should not be used as primary marker.
Editors Note:
The participation of Dr. Robert S. Livingston, E.P. & A., Inc.,
Tallahassee, FL., in the data reduction is appreciated.
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AIR MEASUREMENTS:
Air Temp
Wind: Speed (mph)
Page 25 of 28
Field Data Sheet
Perdido Bay Citizens Monitoring Program
Investigator: Date:
Station: Time:
Direction (circle one) N. NE. E. SE. S. SW. W. NW
Rainfall (inches)
WATER MEASUREMENTS:
Depth (m) Salinity (°/oo) Temp (C) D.O. (mg/L) Secchi (m)
NOTES/UNUSUAL OBSERVATIONS:
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Page
26
of 28
So/dlor
Crook
Palm of to
Crook
Bayou Gar eon
/Intrarlty
UILES
ALABAMA
f- Ptrdido Rivir
Eltvnm/l* Crook
Bayou Marcus
Hwy. 98
Bridfl#
Bridgo Crook
FLORIOA
Tar kiln
Bayou
gulf
oF
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Page 27 of 28
STATION LOCATIONS
PERDIDO BAY STUOY
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WEATHER RECORD
Observer
Location
Page 28 of 28
Month
Year
Day
Rain-fall
(inches)
Wind Speed
(fliDh)
Wind Dir.
Notes
\
2
3
4
5
7
a
9
io
u
12
1?
14
16
17
18
19
20
21
22
23
24
25
26
27
-
28
29
30
31
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•
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GUL£BR£EZEENVROftMGMnLlttKMttH LABORATORY
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GuITroazE,
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