Light Effects Measurement On Sedimentary Particles In

Water Essay, Research Paper

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.


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