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Jingjing Yang bottles water samples
Jingjing Yang bottles water samples
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Week 3
17 July 2006

Searching for the Elusive Element Using Chemical Oceanography

Part II

Part I – Section II
The University of Hawaii Group

Chemical Oceanography – 
How Scientists Collect Data on Trace Minerals

Where does the iron in the ocean come from? Scientists collect water samples to identify and measure the trace elements found with the iron. The presence of manganese is one indication that the iron came from the coastal shelf. The presence of aluminum indicates the iron came from the land in the form of dust.

A simplified version of  the trace metal collection and analysis is as follows:

 

1. First, water is collected from various levels of the ocean using a trace metal clean CTD.
A "CTD" instrument is used to measure Conductivity, Temperature and Depth, and to collect water samples for later analysis.

The CTD Rosette is hoisted over the side of the ship and lowered 200-500 meters beneath the surface.
Link Link

The CTD Rosette on the R/V N.B. Palmer POP Goes Antarctica 2002. The gray bottles, Niskin bottles, can collect water samples at different depths. is the main sampling device.
Link Link

 

2. The Go - Flo bottles that are used to collect the water samples are taken off the CTD and put in a “clean room” in the van. (A note on the van follows at the end of the article.) Then the water is drained into various bottles or tubes.  One group of samples may be analyzed for salinity, another for chlorophyll, while still others are used to measure the trace metal concentrations.

The Go-Flo water sampling bottle is used whenever uncontaminated samples need to be taken, for instance for the chemical analysis of trace metals in sea water. The Go-Flo bottles are closed when they are lowered into the water column and open automatically at a depth of about 10 metres. As a result, these bottles are neither contaminated on deck nor as they are lowered into the water, by the uppermost layer of the seawater surface that is contaminated by interaction with the air. Several Niskin or Go-Flo bottles (12 or 24) can also be attached to a rosette, which is then lowered into the water column.
Link Link


3. For the trace metal determinations, and also for some of the others, the water is first filtered through a filter with very small holes, to make sure that the plankton and other particles in the seawater do not interfere with the analysis, or block the tubes of the equipment.


http://pal.lternet.edu/sci-research/physical/

The Go-Flow is a plastic cylinder used to sample lake water at discrete depths.
LinkLink



4. After filtering to remove particulates, the water samples are run through a machine that uses a chemical process to react with the trace elements, part of this process also involves adjusting the pH of the samples. The amounts of the metals in the samples are proportional to peaks that are produced as the samples pass through the analytical equipment and from this the concentrations can be calculated by the computer.

Looking for Fe - the elusive element

Two reasons for analyzing at sea are that:

  1. If there is a problem with a set of samples, you can collect more, you can find it and rectify the problem.


  2. Also, it is possible to see the results as you are sampling and to investigate interesting processes while you are still out at sea.

 

Staffing: It generally takes 6 people during a minimum of two watches (work shifts) to process the samples.

 

The van: Instead of setting up equipment each time he is at sea, Chris Measures received a grant to turn buy a van (a container like those on container ships) and to turn it into a mobile laboratory. That way, wherever he has a grant to do research, Chris is able to send his van and be ready to analyze samples. The disadvantage is that the cost of shipping the van must be included in the grant proposal. Also, if they send your van to the wrong place, you have nothing to do your research with!  Chris Measures is a Professor at the University of Hawaii. One of his next destinations for research is off Cape Town.

 

 

Week 3
17 July 2006
Searching for the Elusive Element
Using Chemical Oceanography
Part I – Section I

Part I Section I Part I – Section I

 The University of Hawaii Group
Part I – Section II Part I Section II Part I – Section II University of Hawaii Group
Chemical Oceanography – 
How Scientists Collect Data on Trace Minerals
Part II Part II Part II Woods Hole Oceanographic Institution Group



© 2001-2006 Polar Science Station
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NSF Office of Polar Programs, Antarctic Sciences Section
This special report was made possible by the NSF Office of Polar Programs, Antarctic Sciences Section, Award Nos. ANT04-44134 University of California-San Diego Scripps Institution of Oceanography (B. Gregory Mitchell, Farooq Azam, Katherine Barbeau, Sarah T. Gille, Osmund Holm-Hansen); ANT04-43403 University of Hawaii (Christopher I. Measures, Karen E. Selph); ANT04-44040 University of Massachusetts Boston (Meng Zhou); ANT04-43869 Woods Hole Oceanographic Institution (Matthew A. Charette),  for the study entitled "Collaborative Research: Plankton Community Structure and Iron Distribution in the Southern Drake Passage".