Light Effects Measurement On Sedimentary Particles In Water
The purpose of this study plan is to
measure the effects of light on sedimentary
particles in water. This study
plan will include information pertaining to
equipment, procedures, and
analysis. This plan will also discuss problems that
could arise during the
sampling. Objectives The objective of this study is to
observe whether
sedimentary accumulation at various depths will effect the
penetration of
light energy. One reason for monitoring light penetration is to
determine if
sufficient energy is available for photosynthesis. This energy is
effected by
the amount of sedimentation that is suspended in the water. In order
to
ensure the data's scientific validity this study needs to include the
main
principles. These include selecting a control; a control will be the
measurement
that all other data is compared to. Second, the selection of the
sample sites
must be non-bias and random. This ensures that the experiments
are not
predictable or foreseeable. Finally the experiments must be described
in great
detail so that they can be replicated at a later date. Literature
Energy is
distributed throughout the world’s oceans in several usable forms.
The heat
transmitted during absorption is responsible for ocean waves,
temperature and
currents. Light penetration in water will measure in units of
quanta. This
measurement refers to the amount of sunlight that penetrates the
water at
various depths. The light energy is absorbed and scattered by
suspended
particles, dissolved substances, and the water itself (USGS). Other
factors
include attenuation coefficient: rate at which light decreases with
depth. This
means that each site studied may have a different attenuation
coefficient. An
example of a high coefficient would indicate a rapid decrease
in light
penetration, therefore, high sedimentation. Another factor to be
aware of is the
color of the water. Color can effect the light penetration
and intensity. Also
the turbidity which is a measure of water clarity and how
much material is
suspended in the water. Suspended material could include
soil particles, algae,
plankton, microbes, and other substances (EPA). The
sources of the turbidity
could include erosion, waste, runoff, and bottom
feeders (EPA). Equipment The
instruments used to make photosynthetic
measurements is called a Li-Cor
Quantum/Radiometer/Photometer model #189.
The sensory device is connected by a
long cord and is used to measure at
depth. It’s called an underwater PAR
sensor; Li-Cor #1925. This sensing
device or photocell can also be used to
measure surface PAR. Other devices to
be used during the data sampling include
lowering frame Li-Cor #20095,
various weights and cables. The cables and weights
will used to hold the
sensors in the water column at the proper depths. Another
instrument could be
used to calculate the amount of PAR that is received at the
surface. This
instrument is called a pryanometer. It is not a requirement to use
two
different instruments for surface PAR, but just a suggestion that might
give
more scientific validity to the data being collected. Procedure While
conducting
this experiment it is necessary to have at least two people
present to take the
measurements. One person will lower the sensor in the
selected site locations.
The other person will record the PAR
measurements from the display and calculate
range values. The measurements
will be taken within a four-hour period, two
hours on either side of the
solar noon. Solar noon is half way between sunrise
and sunset; not 12:00
noon. Solar noon is at 1:15 PM, Central Daylight Time.
This is the time
when light energy is at the maximum. Samples are taken between
11:15 AM
and 3:15 PM and are taken every 30 minutes; and data recorded at 10
second
intervals. Before the samples can be taken it is imperative that
the
Quantum Radiometer be clean and free of debris and calibrated. This
calibration
will correct errors that may occur. Also the collection of the
control data must
be present. This control must be free of errors and
represent the selected site.
Another measurement must be made of the
surface PAR. This data will help
determine the amount of light energy present
at the surface. Next the
determination of water columns is important. These
sites must be chosen randomly
and cover the entire site. Later others can
concentrate studies in points of
interest. These measurements are taken using
the underwater sensor attached to
the lowering frame. Each water column will
be measured at every 10 cm. These
recordings will continue until the
photometer can no longer detect light energy.
The underwater sensor must
be perpendicular to the bottom surface so that light
intensity will be
scattered at a 90-degree angle. Each column will be tested
twice so that
representative data is present. These samplings should be recorded
in a table
format, and be divided into proper water column, and depth
categories. The
temperature of the outside environment should be determined and
placed in the
table format along with the descriptions of the sample sites and
surface PAR
data. The number of water columns is dependent on the sample
site.
Remember sample columns must be representative of area being
tested. Analysis
Other factors that may effect the data collected include
not returning to the
same sample site later to measure the same water column.
This can be corrected
by placing some type of marker on the shore if the
sample column is near shore.
Other marking devices are needed if the
sample area is in the middle of the
water where no references can be
determined. These marking devices include
floating buoys, and floating balls.
These devices are necessary to make the data
consistent and accurate. Another
problem that can effect samples is shadows. It
is important not to take the
measurements when the area is being shaded. If
there is abundant cloud cover
out it is necessary to wait until clouds
dissipate, or discontinue taking
measurements for that period. Conclusion A high
sediment concentration in the
water will increase water temperature because the
material suspended absorbs
more heat. Unfortunately this also leads to the
decrease in light penetration
because the particles block the light from
reaching the bottom. Therefore
reducing the amount of photosynthesis that will
occur in the water. While
conducting this study plan it could be said that light
and depth are
proportionate to each other. This means that the depth of the
sensor effects
the amount of light that can be measured through the sediment
filled
water.