Sampling of surface water and sediment

Question 1

At which depths would you sample a lake that is 20 meters deep and why?

Answer 1

• 0,5 meter below the surface
• Thermocline
• 1 meter above the bottom

Question 2

What do you separate if you filter the water with 0,2 um filters?

Answer 2

You separate the particulate phase. It is the dissolved phase that will go through the filter.

Question 3

What could happen with the fractions if you don’t have the possibility to filter your sample on the site and instead ask the laboratory to filter the water?

Answer 3

The particles that were in dissolved phase can react with oxygen and turn into particulate phase during transport. This means that the laboratory will filter away the elements we want to know about and then the results will show us low concentrations when in fact we can have higher.

Question 4

How should you store water samples and sediment samples until they reach the laboratory for analysis and why?

Answer 4

Cold and dark. This is to avoid reactions in the sampling bottles.

Question 5

Name a situation/”identification of an environmental problem” when it is good to use a ruttner sampler?

Answer 5

• Good for measuring at different depths in a lake.
• You can also measure temperature at the same time
• Good for when you want to see if there is an eutrophication or not

Question 6

What is the difference between looking at the results from water samples and water moss samples?

Answer 6

• Water samples is more of a “stickprov” and tells us what’s in the water right now (nutrients, trace elements etc. etc.)
• Water moss works more like sediment. It will tell us what elements have been there before, example there has been a pollution of As but in the water sample that we are taking right now does not contain any As, does that mean that there has not been pollution?

Question 7

If you want to trace climate change by analysing the sediments - which sediment sampler would you use?

Answer 7

Corer, kayak corer, russian pit sampler. The sediment core will show you layering which are like tree rings.

Question 8

Explain how the lead concentration in sediments can be used to trace periods of economic development several 100 years ago.

Answer 8

Industry with lead, releasing during good economic years.

Question 9

A new harbour should be established and sediments needs to be dredged in order for the ships/boats to reach the harbour. Your task is to determine if there are any polutants that could be spread during the dredging. Which sampling equipment would you use and why?

Answer 9

• Grabber, easy and fast way, it doesn’t matter where the pollutants are, you just need to know “if?”. You can take more samples over a bigger area. Works if it’s a loose material.
• Corer, depending how deep you have to dredge- if you find a pollutant at 15 meters and you only have to dredge 7 meters, the pollutants are no problem.

Question 10

What is the difference between a direct and an indirect flow/discharge measurement method?

Answer 10

• Direct is in the actual water course

- Indirect is based on mathematical models

Question 11

Explain how a measurement using a rod suspended current meter is to be done

Answer 11

• From bride or boat
• Several sections
• Measure at two depths, 0,2depth, and 0,8depth

Question 12

How does the water flow affect the metal concentration in a river

Answer 12

• Spring flood: dilution of dissolved phase, lower concentrations
• The same for autumn
• Winter: wheathering under the snow cover, ironsulfides start to weather –> a lot of iron (III), which can oxidate more sulfides. During spring this will get washed out which could lead to higher concentrations, but this is not very common.