Lecture 1 Flashcards
(35 cards)
What are research vessels used for?
They range from small ribs to deep sea drilling vessels
How may surface water samples be collected?
By hand from shore, small boats, or ship underway pumping systems
What is a primary use of divers in water sampling?
For precise short sediment cores
What is typically used to collect depth profiles?
Bottles attached to a CTD rosette
List the requirements for water bottles used in sampling.
- Rapid exchange with surrounding water
- Reliable closures
- Resistant to corrosion, no contamination
- Easy to handle
What is the most commonly used water bottle?
Niskin bottle
What is a Go-Flo bottle used for?
It passes the surface interface before opening at ~10m and closing at the required sampling depth
What is the purpose of a hydroline in bottle deployment?
To deploy bottles attached at set intervals using a thin cable
What are the advantages and disadvantages of using a hydroline?
Advantages: Simple
Disadvantages: No knowledge of water column structure, line unlikely to be vertical due to currents
Describe the deployment process using a rosette.
Bottles attached to a frame linked to the ship via a conducting cable, closed individually by signal from the ship
What are the benefits of using a rosette for sampling?
- Obtain a preview of water column structure
- Sample specific features
- Large volumes obtained by closing more than 1 bottle
How are water particles processed for chemical analysis?
Particles are filtered
What are common sources of particulate matter in water?
- Biology
- Dust
- Rivers
- Resuspension in coastal/estuarine environments
What is the typical range of particle concentrations in different environments?
From g/L in turbid estuaries to a few micrograms/L at intermediate water depths in the open ocean
What type of filter is usually used to separate dissolved phase from particulate phase?
0.2 microns filter
List the ideal characteristics of filters used in sample processing.
- High mechanical strength
- Uniform particle cut-off
- No contamination/adsorption
What is the importance of preventing changes in the composition of dissolved phases during sample storage?
To avoid biota adsorption and other alterations
What is the typical method for storing macronutrient samples?
Usually freeze
How should trace metals be treated for storage?
Usually acidify to pH~2
What is an in situ filtration method?
Allows filtration of several hundreds of litres of water
What are the two types of sediment traps?
- Eulerian (fixed on the seafloor)
- Lagrangian (free drifting)
What are the advantages of using sediment traps?
- Direct flux measurements
- Time series possible
- Can acquire a large mass of material
- Allows collection of rarer large particles
What is a disadvantage of sediment traps?
Potential for over and under trapping
What are the advantages of in situ pumps?
- Rapid deployment and recovery
- Allows collection of fine particles
- Can acquire large mass of material
