Chemical Oceanographic Measurements

From Ocean Teacher Library

Jump to: navigation, search

Refresh Page

Contents

Background

This very brief description is not intended to provide fundamental instruction in chemical oceanography; as with all OceanTeacher materials, we leave basic marine education to the colleges and universities. This article merely provides a conceptual framework and terminology for data managers who may have a slightly different specific background, but who have marine data responsibilities.

Principal Constituents of Sea Water

Historically, these are the most frequently made chemical measurements, hence the term "principal." The first three listed here are the classical hydrochemistry parameters universally measured by physical oceanographers and hydrographers for water mass studies.

  • Temperature - Customarily listed with chemical parameters
  • Salinity
  • Oxygen
  • Phosphate (dissolved, particulate, total)
    • Older data used umol/l for units; many modern programs use umol/kg
    • [Good overview needed]
  • Silicate
    • Older data used umol/l for units; many modern programs use umol/kg
    • [Good overview needed]
  • Nitrate, nitrite, nitrate+nitrite, total nitrogen
    • Older data used umol/l for units; many modern programs use umol/kg
    • [Good overview needed]
  • Hydrogen sulfide
    • Older data used umol/l for units; many modern programs use umol/kg
    • [Good overview needed]
  • Ammonium
    • Older data used umol/l for units; many modern programs use umol/kg
    • [Good overview needed]
  • pH
    • Pure number; no units
    • [Good overview needed]
  • Alkalinity
    • Older data used milliequivalents/l; many modern programs use umol/kg
    • [Good overview needed]
  • Chlorophyll a
    • Older data used ug/l; many modern programs use ug/kg
    • [Good overview needed]

Other Constituents of Sea Water

Essentially all naturally occurring elements and isotopes, some artificial isotopes, and most ionic and molecular inorganic species, together with thousands of organic and biochemical compounds have been analyzed in the sea. Whether to test analytical methods to their limits or as legitimate research objects associated with articulated hypothesis, this work has yielded vast amounts of data. In only a limited number of cases have the data been sufficiently widespread and reliable to synthesize global mass balances and/or process models. One notable example of a practical application is the use of Tritium (an isotope of Hydrogen released into the atmosphere during nuclear testing prior to the ban in 1962) to track slow water movement in the deep sea.

Overview of Shipboard and Laboratory Analytical Methods

[Good overview needed]

Overview of In-Situ Probes and Remote-Sensing Methods

[Good overview needed]

Evolution of Chemical Units

During the 20th century, there was a major evolution in the way that chemical constituents were reported, indicated in the notes above. In brief, the custom of reporting principal constituents "per liter" was replaced by the use of "per kg" (of seawater). Additionally, the problem-prone use of terms such as "per million" or "per billion" used for trace chemical reporting was abandoned completely, in favor of either molar quantities per kg, or "mass-per-mass" units. The following articles have been prepared to explain these issues:

Chemical Parameter Lists

Creating master lists of all chemical species analyzed in the sea is practically a cottage industry in oceanography, thus there are many to choose from. By far, the most comprehensive list is that developed by the BODC (below).

  • See Parameter Name Standards for Marine Data for the current status of discussions to adopt a standard parameter list
  • Resources on the UK NERC Data Grid Vocabulary Server - The Vocabulary Server is a Web Service API implemented both as SOAP and pseudo-restful HTTP-POX interfaces, containing many vocabularies gathered by UK scientists
    • BODC Use Metadata Parameters List - List P011 contains all measurement terms, including chemistry. This list is enormous (~19,000 terms), so should not normally be downloaded. The surprising number is due to the fact that the BODC register includes both parameters and methods to measure the parameters. Physical, biological and geological parameters are included, so a simple count of chemical parameters is impossible, but it is probably the largest category of parameters.[Similarly named lists contain working datasets, and should not be consulted]
    • BODC Discovery Metadata Parameters List - List P021 contains all measurement terms, including chemistry. This list is relatively manageable in size, because the terms are more generalized than the use metadata link above. [Similarly named lists contain working datasets, and should not be consulted]

Additional Resources

Subsections of this article

Pagename Short title Description
Conversion Formulas for Chemistry Measurement Units Conversion Formulas for Chemistry Measurement Units Conversion Formulas none
History of Chemical Measurement Units History of Chemical Measurement Units History of Units none
Mole Concept in Chemical Measurements Mole Concept in Chemical Measurements Mole Concept none
Obsolete Parts-per-X Chemistry Units Obsolete Parts-per-X Chemistry Units Parts-per-X none


Information about this article

Short title: Chemical Measurements

Description: This article is intended to provide a brief introduction to the types of data and products involved in this discipline. It is not a general introduction to the discipline itself.

Expertise level: beginner

Author: Murray.Brown

Approval status: approved

Approved by: Murray.Brown

Last change: 2009-9-24

Subsection of: Marine Data Concepts

Contact

If you have any direct comments or suggestions for the author of this page then please feel free to send an email to the author (listed above). For discussions on this page please use the discussions page.,  


Retrieved from "http://library.oceanteacher.org/OTMediawiki/index.php/Chemical_Oceanographic_Measurements"
Personal tools