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OCEAN LAB 7 - Water Chemistry
Overview:
Students will identify the basic chemical and physical properties of seawater and their interconnectedness to each other and the marine life that they support
Physical Properties:
Salinity, temperature, light and turbidity, specific gravity, temperature
Chemical Properties and Dissolved Gases:
Salinity, nitrate, nitrite, ammonia, O2, phosphate, pH
Biological Considerations:
Phytoplankton/algae blooms, coral disease
Lab 07 WATER QUALITY ANALYSIS
PURPOSE
To measure dissolved solids in various samples of water to determine water quality
MATERIALS
· Chemical test kits
· Smart Spec
· water samples from various sources
· demineralized water
· Squeeze bottles for DI water
· Secchi disk
· Disolved O2 meter
· Salinometer or refractometer
· Lens paper to clean vials
· Waste containers
· Beakers (50, 100ml)
· Graduated cylinder (10, 25, 50 ml)
· Gloves
· Lab coats
· Collecting vials
· pH meter/paper
· eye droppers
· glass stirrer
PROCEDURE
Use sterile technique to test the water samples according to kit directions. Read about the levels of these substances in water to make your judgment about the safety of the samples and their potential for pollution.
The units of measurement for water can be confusing. Milligrams per liter (mg/l) is the same as parts per million (ppm). Parts per thousand is percentage multiplied by 10.
To convert percentage to ppt, multiply the percent by 10. For example, a 2% solution is the same as 20 ppt.
AMMONIA: Ammonia nitrogen is the product of microbiological activity. In natural waters, it is evidence of sanitary (fecal matter) pollution, industrial effluent or pesticide runoff. It is a source of nitrogen that contributes to excessive growth of algae and can be toxic to aquatic life.
DISSOLVED OXYGEN: It is one of the most important characteristics of water quality. Aquatic plants produce oxygen through photosyntheses, and it enters the water from the air. Standards for oxygen vary but fresh water fish need concentrations of 4-5 mg/l. Salt water holds less oxygen than fresh water, when measured at the same temperature. The solubility of oxygen is inversely proportional to water temperature. Oxygen is essential to sustain life in marine ecosystems.
NITRATE: Nitrogen is essential for plant growth and is a component of fertilizers. But the presence of excessive amounts in water supply presents a major pollution problem. Nitrogen compounds may enter water as nitrates or be converted to nitrates from agricultural fertilizers, sewage discharge from waste treatment facilities or septic tanks, drainage from livestock areas and farm manure. Nitrates in large amounts can cause methemoglobinemia
(blue babies), a fatal disorder for infants less than six months of age. The U.S. Public Health Service limits drinking water to 10 ppm nitrates.
NITRITE: While nitrites are present in natural water, they should be at lower levels than nitrate, because it is easily converted by bacteria to other forms of nitrogen. Excess nitrites can form nitrous acid at low pH levels. This is a health concern because nitrous acid can react with organic compounds to form nitrosamines, known carcinogens. High levels indicate decomposing organic matter, or discharge from industry or waste treatment facilities.
pH: pH refers to the acidity or alkalinity of a solution. The average pH of seawater is 8.4. The ocean uses a bicarbonate buffer to help stabilize its pH. Besides, the ocean is large and well mixed, which also contributes to a stable pH. However, in areas that receive much pollution from industrial activity or from active volcanoes, scientists are discovering that the oceans are becoming more acidic and less resistant to maintaining a stable pH. What does this mean for aquatic life? Acids dissolve calcium carbonate, which make up coral skeletons, plankton tests, mollusk shells, and algae and sponge frameworks. Acidic water also affects invertebrate and vertebrate development.
PHOSPHATE: Phosphorus is an important nutrient for aquatic plants, and is naturally occurring in rocks. It is used to manufacture pharmaceuticals and detergents. The amount found in water is generally not more than 0.1 ppm unless the water is polluted from agricultural drainage or detergents. When excess phosphorus is present in marine systems, eutrophication takes place. This creates a favorable environment for the increase in algae and weed nuisances. When algae cells die, oxygen is used in the decomposition and fish
die due to lack of oxygen. Rapid decomposition of dense algae scum cause foul odors and hydrogen sulfide gas. High concentrations indicate fertilizer runoff, discharge from industry or waste treatment facilities.
TURBIDITY : Turbidity is a state of reduced transmission of light through water caused primarily by the presence of suspended matter - either organic or inorganic. Increased turbidity results in a decrease in biomass due to the decrease in potential photosynthesis.
What is turbidity and why is it important?
Turbidity is a measure of water clarity how much the material suspended in water decreases the passage of light through the water. Suspended materials include soil particles (clay, silt, and sand), algae, plankton, microbes, and other substances. These materials are typically in the size range of 0.004 mm (clay) to 1.0 mm (sand). Turbidity can affect the color of the water. Higher turbidity increases water temperatures because suspended particles absorb more heat. This, in turn, reduces the concentration of dissolved oxygen (DO) because warm water holds less DO than cold. Higher turbidity also reduces the amount of light penetrating the water, which reduces photosynthesis and the production of DO. Suspended materials can clog fish gills, reducing resistance to disease in fish, lowering growth rates, and affecting egg and larval development. As the particles settle, they can blanket the stream bottom, especially in slower waters, and smother fish eggs and benthic macroinvertebrates. Sources of turbidity include:
· Soil erosion
· Waste discharge
· Urban runoff
· Eroding stream banks
· Large numbers of bottom feeders, which stir up bottom sediments
· Excessive algal growth.
Sampling and equipment considerations:
Turbidity can be useful as an indicator of the effects of runoff from construction, agricultural practices, logging activity, discharges, and other sources. Turbidity often increases sharply during a rainfall, especially in developed watersheds, which typically have relatively high proportions of impervious surfaces. The flow of storm water runoff from impervious surfaces rapidly increases stream velocity, which increases the erosion rates of stream banks and channels. Turbidity can also rise sharply during dry weather if earth-disturbing activities are occurring in or near a stream without erosion control practices in place.
Regular monitoring of turbidity can help detect trends that might indicate increasing erosion in developing watersheds. However, turbidity is closely related to stream flow and velocity and should be correlated with these factors. Comparisons of the change in turbidity over time, therefore, should be made at the same point at the same flow.
Turbidity is not a measurement of the amount of suspended solids present or the rate of sedimentation of a steam since it measures only the amount of light that is scattered by suspended particles. Measurement of total solids is a more direct measure of the amount of material suspended and dissolved in water.
Turbidity is generally measured by using a turbidity meter. Another approach is to measure transparency (an integrated measure of light scattering and absorption) instead of turbidity. Water clarity/transparency can be measured using a Secchi disk or transparency tube. The Secchi disk can only be used in deep, slow moving rivers; the transparency tube, a comparatively new development, is gaining acceptance in programs around the country but is not yet in wide use.
A turbidity meter consists of a light source that illuminates a water sample and a photoelectric cell that measures the intensity of light scattered at a 90 angle by the particles in the sample. It measures turbidity in nephelometric turbidity units or NTUs. Meters can measure turbidity over a wide range from 0 to 1000 NTUs. A clear mountain stream might have a turbidity of around 1 NTU, whereas a large river like the Mississippi might have a dry-weather turbidity of around 10 NTUs. These values can jump into hundreds of NTU during runoff events. Therefore, the turbidity meter to be used should be reliable over the range in which you will be working. Meters of this quality cost about $800. Many meters in this price range are designed for field or lab use.
Although turbidity meters can be used in the field, volunteers might want to collect samples and take them to a central point for turbidity measurements. This is because of the expense of the meter (most programs can afford only one and would have to pass it along from site to site, complicating logistics and increasing the risk of damage to the meter) and because the meter includes glass cells that must remain optically clear and free of scratches.
REFRACTOMETER AND SALINITY
Purpose
A refractometer measures how much light bends as it travels through a drop of water. The more saline the water (the denser the water), the more light bends as it travels through it. Since density is dependent on both salinity and temperature, this device has been calibrated for seawater in the range of 10-30oC, to give you the accurate density and salinity of the sample.
Materials
· Eye dropper and seawater sample
· Refractometer
· Distilled water and Kim Wipes
Method
1. BE CAREFUL with this instrument. It is expensive and fragile. Carefully lift up the plastic cover on the end of the instrument and ensure that surface is clean (visual inspection ok).
2. Place two drops of seawater on the glass, in the center.
3. Carefully close plastic cover. Drop should cover entire glass. If it doesn’t, clean surface gently with distilled water and a Kim Wipe and do over.
4. When drop coverage is complete, hold instrument to your eye and read the specific gravity (density) and salinity from the screen. (Move outer objective out or in to focus.)
5. CLEANING: With distilled water and a Kim Wipe, gently clean the glass surface and put instrument back in its box.
Date______Class ______Name ______
DATA CHART
PARAMETERS / Sample 1 / Sample 2 / Sample 3 / Sample 4 / Sample 5LOCATION:
AMMONIA NH3
DISSOLVED O2
NITRATE NO3
NITRITE NO2
pH
PHOSPHATE PO4
SALINITY
TURBIDITY
Assignment: LAB REPORT (due next class)
As part of a formal lab report, discuss each water sample in terms of its overall quality and potential risk to the environment. State in which samples pollutants were identified and what type of pollutants caused the quality to drop.
How to write a formal lab report:
Step 1 - The Title Page: The title should be centered on the paper. The course name should be centered and written two spaces below the title. The date is centered two spaces below the course name. Your first name, followed by the name of your lab partners, should be in the lower right-hand corner. Typed papers with computer spell-checking make the best presentation. However, if that is not available, use black pen and make sure that your handwriting is neat. Proof read and correct minor spelling errors. Major errors may warrant recopying the page.
Step 2 - Purpose Statement: State the purpose of the lab or the hypothesis to be tested. Provide background information to assist the reader in following your objectives. Define any terms that a reader may be unsure of.
Step 3 - Materials and Procedure: The materials are listed separately. Use a short paragraph, written in third person past tense, to describe the methods used to determine the data. The paragraph should be general rather than step by step instructions.
Step 4 – Data Analysis: Present the data is some organized manner - a graph, map or table. Every entry must be clearly labeled. Graphs must be titled and axes labeled. All calculations and formulas should be presented in an organized format, with corrects units of measurements.
Step 5 - Results: Use separate paragraphs to summarize what the data for each sample is showing, identify causes and effects, use comparison and contrast, and evaluate what you have observed.
Step 6 - Discussion: The conclusion section discusses the results in the context of the entire experiment. Usually, the objectives mentioned in the "Introduction" are examined to determine whether the experiment succeeded. If the objectives were not met, you should analyze why the results were not as predicted. You need to address the following: What is the significance or meaning of the results? What were you suppose to discover from this activity? How could you apply what you have learned? Could this information be useful in predicting results for similar circumstances?
Include any possible sources of error, either in the procedure or in your techniques, especially if you did not obtain the expected results. Would your results be reproducible for others? Do not “fix” the data to meet your expectations. Finish with a summary statement
- a final answer.
Step 7- References: In this section you will list any literature that you have cited in the text. List ONLY those references that you have specifically cited. References are listed in alphabetical order, by the first letter of the first author's last name.
Sample Citations:
For a Journal
Brown, E.K., Cox, E.F, Tissot, B., Jokiel, P.L., Rodgers, K.S., Smith, W.R., & Coles, S.L.(2004). Development of benthic sampling methods for the Coral Reef Assessment and Monitoring Program (CRAMP) in Hawaii. Pacific Science, 7, 145-158.
For a Book
Thurman, H. & Trujillo, A. (2008). Essentials of Oceanography (9th ed.). NJ: Prentice Hall.
For a Sample Lab Report visit: http://csm.jmu.edu/biology/garrisne/physiology/SampleReport.htm.