Dataset: nutrients_LMG
Deployment: LMG0104

Protocol for measuring nutrients (pdf)

Final data report for nutrients, LMG0205 (pdf)

Oxygen analysis: Prior to each series of analysis the titrator was standardized with a solution of KIO3 (standard solution concentrations are listed in the calculation workbook). Standards were titrated until agreement reached +/- 2 uL. A reagent blank determination was conducted at the start of the cruise and used throughout. Titrations performed on the Langford Amperometric system were logged during operation and the titration data stored.

Nutrient determinations were conducted on an Alpkem Flow Solutions segmented flow autoanalyzer. Operation and standardization of the system is described in detail in the Flow Solutions manual under the file "Alpkem manuals". Linearity checks were conducted at the beginning of the cruise for each of the ions and conducted at the start and completion of each sample sequence. Efficiency checks on the Nitrate reduction column (OTRC, Alpkem) were run after introduction of the column into the analytical stream. Analysis integrity was also checked by sampling surface and bottom water bottles in duplicate. This process was repeated on most casts.

Significant difficulty was experienced with the SBE oxygen sensor on the CTD instrument package. Agreement between the titration determinations of oxygen and logged values through the CTD instrument package was extremely variable and suggested several sources of error. Under the directory containing bottle data, two jpeg format files contain comparisons of the SBE output and other parameters taken by the CTD package and the Winkler determinations. In property:property comparisons with other parameters collected by the package (i.e. Temperature, Salinity) variability was obvious and difficult to explain. Investigation into this variability suggested dependence on the rate of decent as well as strong dependence on the extreme cold temperatures and ice problems. During the cruise a second sensor was installed as a secondary. This sensor reported higher concentrations but similar trends. An intercomparison with the CTD package operated on the NBP was carried out on September 1 (Event 201/LMG24402.001). Comparison of the data files showed significantly higher concentrations reported by the NBP system agreeing with the Winkler titration values.

Shortened Reagent Prep. list for Nutrient Analysis (pdf) Aug 2001

1. ANALYSIS OF  NO₂^- + NO₃^- / NO₂^-

Sulfanilamide: 10gm Sulf. dissolved and diluted to 1000ml in 10%HCl. Store at room temp.

NEDA (N-1-Napthylethylene-diamine dihydrochloride): 1.0 gm NEDA dissolved and diluted to 1000ml in DIW.  Store in amber bottle at room temp. for short term or refrigerate if long term.

Imidazole Buffer: 13.6gm Imidazole dissolved in approx. 3800ml DIW. Add 60ml of prepared NH₄Cl-CuSO₄ stock solution (stir for ~ 10 min.).  Dropwise, add 10% HCL to a final pH: 7.8-7.85.  Dilute to 4000ml with DIW.  Store at room temperature.

Copper Sulfate stock: 20gm CuSO₄ dissolved and diluted to 1000ml in DIW. Store at room temp.

Ammonium Chloride-Copper Sulfate stock (NH₄Cl-CuSO₄):  250gm NH₄Cl dissolved in approx. 950ml DIW.  Add 60 drops (~2.8ml) of CuSO₄ stock and then dilute to 1000ml in DIW.  Store at room temperature.

2. ANALYSIS OF SiO₄^4-

Ammonium Molybdate: 10.8gm NH₄Molyb. dissolved in approx. 900ml DIW. Add 2.8ml conc. H₂SO₄ and then dilute to 1000ml in DIW.  Store in amber bottle at room temperature for short term, otherwise refrigerate if long term.  Label as Ammonium Molybdate for Silicate analysis.

Tartaric Acid:  200gm Tart. dissolved and diluted to 1000ml in DIW.  Store at room temperature.

Stannous Chloride stock (SnCl₂):  10gm SnCl₂ dissolved and diluted to 20cc in 50% HCl. Dissolves faster if freshly made warm 50% HCl is used.  Store in freezer.

Stannous Chloride Working:  1ml of stock SnCl₂ diluted to 50ml in 10%HCl.

3. ANALYSIS of PO₄^3-

Hydrazine Sulfate:  5.0gm Hydrazine Sulf. dissolved and diluted to 500ml in DIW.  Store at room temperature for short term, otherwise refrigerate if long term.

Ammonium Molybdate:  27.25gm NH₄Molyb. dissolved and diluted to 250ml in DIW.  Add cooled H₂SO₄ stock solution.  Label as Ammonium Molybdate for Phosphate analysis.

Sulfuric Acid stock (H₂SO₄):  Slowly add 320ml conc. H₂SO₄ to 405ml DIW while stirring.  Caution: This solution gets HOT!  Place DIW in ice bath prior to addition of H₂SO₄.

4. ANALYSIS of NH₄⁴⁺

Complex Reagent:  140gm Sodium Citrate dissolved to approx. 950ml in DIW.  Adjust pH to 7.0 w/ 10%HCl  Bring to final volume of 1000ml with DIW.

Phenol:  Add 60ml of 10N NaOH to approx. 700ml DIW.  Add 12ml of liquefied phenol (88%).  Dilute to 1000ml with DIW. 10N NaOH:  400gm Sodium Hydroxide dissolved and diluted to 1000ml in DIW  (HOT!!!).

Sodium Nitroferricyanide:  .5gm NFeCN dissolved and diluted to 1000ml in DIW.

Sodium Hypochlorite:  Add 2.5ml of 5.25% NaOCl (household bleach, eg. CLOROX) to 75ml of DIW and dilute to 100ml with DIW.  If using extra-strength, dilute 2ml of NaOCl to 100 ml DIW.