A Water Quality Field Study

By

Paul EylerKenya Trimble-McCullough

Zelia McGahaDavid Peacock

ObjectivesPrimary TEKS – 8.11 B, 8.4 A-BSubsequent TEKS – 8.1 A, 8.2 A-E, 8.3 A-C

In this experiment, you will:• Compare and contrast water quality between freshwater

aquatic systems.• Use Vernier LabQuest and probes:

1. Use a Temperature Probe to measure water temperature.

2. Use a Conductivity Probe to measure the conductivity of water.

3. Use a pH Sensor to measure the pH of water.4. Use a Dissolved Oxygen sensor to measure dissolved

oxygen.• Make visual observations at the test sites of plant, animal,

and insect life.• Sample macroinvertibrates populations• Draw a map of your location

The Freshwater Biome

Freshwater is defined as having a low salt concentration (less than 1%). Plants and animals in freshwater regions are adjusted to the low saltPonds, lakes, streams, rivers, and wetlands

IntroductionWhen finding water quality, there are many measurements that can be made. In this experiment, you will measure the water:1.Temperature2.Conductivity3.pH4.Dissolved oxygen

TemperatureWater temperatures in streams can range from 0C in the winter to above 30C in the summerCooler water in a stream is generally considered healthier than warmer waterProblems generally occur when changes in water temperature are noted along one stream on the same day Some sample data are listed in Table 1

ConductivityConductivity values in lakes and streams are typically found to be in the range of 100 to 500 µS/cm. Some sample data are listed in Table 1In areas of especially hard water or high salinity, conductivity values may be as high as 1000 µS/cm Drinking water usually has conductivity in the 50 to 1000 µS/cm range Some sample data are listed in Table 2

Conductivity is a measurement of the ability of an aqueous solution to carry an electrical current. An ion is an atom of an element that has gained or lost an electron which will create a negative or positive state. For example, sodium chloride (table salt) consists of sodium ions (Na+) and chloride ions (Cl-) held together in a crystal. In water it breaks apart into an aqueous solution of sodium and chloride ions. This solution will conduct an electrical current.

There are several factors that determine the degree to which water will carry an electrical current:

1. the concentration or number of ions 2. mobility of the ion 3. oxidation state (valence) 4. temperature of the water

Used as a measure of the mineral or other ionic concentration. Conductivity is a measure of the purity of water or the concentration of ionized chemicals in water

pH

The best pH range for most aquatic organisms is pH 6.5 to 8.2. The pH values of streams and lakes are usually between pH 7 and 8. Hard water will often have pH values between 7.5 and 8.5. It is used to measure the acidity of liquids represented by a scale of numbers from 0 to 14. The pH of pure water is 7.0, which is neither acidic nor basic. When the pH is less than 7.0 it is identified as acidic; and at a pH greater than 7.0, it is considered basic or alkaline.Aquatic organisms’ ability to survive is reduced if the pH of the water becomes greater than 9.0 or less than 5.0. The pH of water is very important in order to sustain a healthy aquatic ecosystem.

The main factors that could affect pH are:

Dissolved mineral substances (e.g. hard water-pH greater than 7.0)Aerosols and dust from the airMan-made wastes (e.g. waste from mining operations)Photosynthetic organisms (plants remove carbon dioxide CO2-increasing pH)

Underlying rock and soil type in a watershed determines the general pH of the system

pH

Dissolved Oxygen

The dissolved oxygen (DO) is oxygen that is dissolved in water. Therefore, DO analysis measures the amount of gaseous oxygen (O2) dissolved in water. Oxygen gets into water by diffusion from the surrounding air, by aeration (rapid movement), and as a waste product of photosynthesis.

Oxygen is a necessary element to all forms of life. DO is important to fish and other aquatic life. Adequate dissolved oxygen is necessary for good water quality. Natural stream purification processes require adequate oxygen levels in order to provide for aerobic life forms. As dissolved oxygen levels in water drop below 5.0 mg/l, aquatic life is put under stress. The lower the concentration, the greater the stress. Oxygen levels that remain below 1-2 mg/l for a few hours can result in large fish kills.

When performing the dissolved oxygen test, only grab samples should be used, and the analysis should be performed immediately. Therefore, this is a field test that should be performed on site.When doing this experiment, you might choose to compare water quality at two or more points on the same stream, in two or more different streams or lakes, or in a lake and a stream that runs into it.

Data and Observations

Site

Temperature (°C)

Conductivity (µS/cm)

pH

Clarity

Macroinvertibrates

Other Observations

Map

Materials

• LabQuest • LabQuest App• Temperature Probe • Vernier Conductivity Probe • Vernier pH Sensor • Colorless plastic bottle • Plastic cup or beaker • Dissolved Oxygen probe

Problem

How do we determine and compare the health of aquatic systems?

Hypothesis

State a valid Hypothesis

Example:Site 1 will have a higher water quality than site 2 due to the chemical and physical composition.

Paul Eyler

James Hogg Middle SchoolIB Science 6-8

David PeacockHubbard

Middle School8th Grade Science

Kenya Trimble-

McCulloughMoore MST Magnet

Middle School8th Grade Science

Zelia McGahaChapel Hill

Middle School7th Grade Science