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CTD
Chemistry
Definitions
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WATER Institute Data Sets
Monthly Monitoring of Lake Michigan
Lake Michigan Buoy
Other Data Sets
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UW-Milwaukee
Great Lakes WATER Institute
600 East Greenfield Avenue
P.O. Box 413
Milwaukee, WI 53201-0413
Phone: (414) 382-1700
Fax: (414) 382-1705
Monthly Lake Michigan Monitoring
Details of measurements
A variety of field and laboratory methods are used to produce the WATER Institute data presented here.
CTD Measurements
Measurements were taken using an SBE 25 Logger manufactured by Sea-Bird Electronics. The instrument specifications and manual can be viewed at their site http://www.seabird.com/. The table below summarizes the measurements taken and how they are stored in the database.
| Field name | Parameter | Units | Description, comments |
|---|---|---|---|
| depth | Depth | m | |
| pressure | Pressure | db | |
| cond | Conductivity | uS/cm | Measurement of ionic species present in the water |
| temp | Temperature | deg C | used to detect the location of the thermocline (seasonal layering of water) |
| oxC | Oxygen, current | uA | raw current measurement |
| oxT | Oxygen, temperature | deg C | temperature reading, used to correct dissolved oxygen concentration |
| xmiss | Transmissometer | indictor of water clarity | |
| flS | Fluoresence | measure of chlorohyll present | |
| par | Irradiance | measure of depth of light penetration | |
| pH | pH | none | indicates acid/base balance |
| orp | Oxidation/Reduction potential | mv | indicator of aerobic (oxygen rich) or anaerobic (oxygen poor) conditions |
| oxMgC | Dissolved Oxygen | mg/L | calculated DO concentration |
| oxMGT | Dissolved Oxygen | mg/L | concentration corrected for temperature |
| flag | |||
| nbin | Number of scans per bin | ||
| station | Station ID | two letter abbreviation | added by DBA for compatibility with other tables |
| date | Date | YYYY-MM-DD | added by DBA for compatibility with other tables |
Chemical Measurements
These are tests done at the WATER Institute after the water samples are returned to the lab. They are done using a variety of methods and intrumentation.
| Field Name | Parameter | Units | Analysis Method |
|---|---|---|---|
| INORGANIC_CARBON |
Dissolved Inorganic Carbon
(total CO2) |
mM | Allen Method, diffusion across a teflon membrane |
| CHLOROPHYLL | Chlorophyll A | ug/L | EPA method |
| PHAEOPIGMENT | Phaeopigments | ug/L | Acid extraction |
| TOTAL_PIGMENT | Total Chlorophyll pigments | ug/L | |
| PIGMENT_RATIO | Ratio of Chlorophyll A to Phaeopigments | calculation | |
| AMMONIA | Ammonium ion, NH4+ | uM | EPA phenate colorimetric method |
| NITRATE | Nitrate and Nitrite, NO3- + NO2- | uM | EPA cadmium reduction method, FIA |
| NITRITE | Nitrite ion, NO2- | uM | Sulfanilimide method, FIA |
| SILICA | Reactive soluble silica, SiO2 | uM | Molybdate with sulfite reduction, FIA |
| CHLORIDE | Chloride ion, Cl- | uM | IC |
| SULFATE | Sulfate ion, SO42- | uM | IC |
| SRP | Soluble reactive phosphorus | uM | Molybdate method |
| TOTAL_P | Total Phosphorus | uM | Persulfate digestion followed by molybdate method. |
| DISSOLVED_P | Dissolved phosphorus | uM | Molybdate method following filtration with 0.2 um membrane filtration |
| PARTICULATE_P | Particulate phosphorus | uM | Difference between total phosphorus and dissolved phosphorus measurements. |
| UV_P | Ultraviolet labile phosphorus, bound to organic particulate matter | uM | Residue from filtering sample is irradiated with 254 um light from a Hg lamp before molybdate method is applied. This method excludes inorganic polyphosphates. |
| PROTEIN | Protein | ug/L | Residue on glass fiber filter is reacted with coumassie blue (Bradford method). |
| PART_ORGANIC_C | Particulate organic carbon | ug/L | Residue on glass fiber filter is analyzed for carbon using a Carlo-Erba CHN analyzer instrument. |
| PART_ORGANIC_N | Particulate organic nitrogen | ug/L | Residue on glass fiber filter is analyzed for nitrogen using a Carlo-Erba CHN analyzer instrument. |
| NO3 | Nitrate ion, NO3- | uM | Difference between nitrate plus nitrite and nitrite measurements. Not part of original data set, calculated by the project DBA after data was received from the investigators. |
Abbreviations, Definitions, and Footnotes
- FIA
- Flow Injection Analysis - a continuous flow method of automation. See Ian McKelvie's description
- IC
- Ion Chromatography, separation of ions on an HPLC ion exchange column followed by conductivity detection.
- uM
- Micromolar, micromoles per liter
- mM
- Millimolar, millimoles per liter
- ug/L
- Micrograms per liter, used where the results are not from a unique molecular species.
- uA
- Microamps.
- mv
- Millivolts.
- DBA
- Database Administrator, person responsible for managing data submitted by investigators.
Contacts
Russell Cuhel, PhDUW-Milwaukee WATER Institute
email: rcuhel@uwm.edu
Carmen Aguilar-Diaz, PhD
UW-Milwaukee WATER Institute
email: aguilar@uwm.edu
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