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.