Turbidity

What is the name of the device lowered from bridges and boats to measure the transparency of water?

Secchi Disk

Measurements made with Secchi disks and turbidimeters can be roughly equated – true or false?

True

Describe a typical Secchi disk used in freshwater environments.

Is an 8 inch disk with alternating black and white quadrants.

Why are Secchi disks often not practical to use in many streams?

The current is too swift and many streams are too shallow.

What is the “Great American Dip in”?

An annual event held every July where volunteers from all over the U.S. monitor the clarity of lakes. Secchi disks are used to measure turbidity in this event.

What can particles suspended in water do?

They can clog fish gills.

How do suspended solids affect aquatic life?

Decrease resistance to disease, increase the amount of harmful microorganisms and pollutants that are found in a body of water, and decrease the amount and type of habitat available for aquatic invertebrates.

During periods of heavy precipitation the Rouge River often appears quite turbid after quick visual inspection, why is this?

The material (soil) that the river flows through is primarily clay (an easily erodible particle that stays in suspension even with very slow stream velocity).

How long should you wait before testing water for turbidity?

Can be stored for up to 24 hours in the dark if turbidity cannot be determined on the day of sampling.

Turbidity quantifies the amount of sediment in the water - true or false?

False

How should turbidity samples be taken?

Collect water in the middle of the stream a little below the surface of the water.

What is flocculation?

A process for treating water from a public water supply that helps to decrease turbidity.

What is alum?

Alum is a chemical mixture of iron, chloride, and lime. When added to water, it causes solids to settle to the bottom.

How is turbidity most accurately measured with in most rivers (what type of a device)?

Turbidimeter

How does turbidity affect the ability of photosynthetic organisms to carry out their life processes?

Photosynthesis decreases in turbid water because there is less light to carry out the process.

How does the speed that water is moving affect the suspended solids it can carry?

The faster water is moving, the more suspended solids it can carry.

A turbidimeter reads turbidity in what units?

NTUs

What are some things that can cause high turbidity?

Carp and other bottom feeding fish that stir up sediments, soil erosion, urban runoff, etc.

What can turbidity do to oxygen levels as water warms?

Turbidity can cause oxygen levels to decrease as water warms.

Why was a small drop of silicone oil spread evenly over the glass sample cells with a soft, lint free cloth?

To mask or cover any scratches or imperfections in the glass that the turbidimeter would read as turbidity.