0508S: Discrete Dissolved Inorganic Nutrients Sampling Document
Data originator
Dr George Slesser, Marine Laboratory (MARLAB), Marine Scotland.
Originator's Protocol for Data Acquisition and Analysis
Discrete water samples were taken from Niskin bottles attached to the CTD frame used during the cruise. Bottles were triggered whilst the CTD package was descending through the water column on each cast.
Analysis was performed on unfiltered samples whilst onboard, typically within 10 hours of sample collection. Nutrient concentrations were determined colorimetrically using a QuAAtro autoanalyser. Calibration was carried out relative to stock solutions of nitrite, nitrate and phosphate. Silicate calibration utilised lab-prepared stock solutions. The full methods for nutrient analysis were supplied to BODC by the data originator.
BODC processing
Nutrient samples collected at Extended Ellett Line stations during the cruise were supplied to BODC in an Excel spreadsheet. The nutrient concentrations were supplied together with the approximate (pre-allocated) sampling depths. The raw Sea-Bird files were also supplied. These were used to regenerate bottle firing (.btl) files which could be used to determine precise sampling depths. Nutrient values were merged with the associated information harvested from the Sea-Bird files and loaded to BODC's Oracle relational database.
Contents of data series
| Originator variable | Originator units | Description | BODC parameter code | BODC units | Comments |
|---|---|---|---|---|---|
| NO3 | µg-at/l | Concentration of nitrate+nitrite | NTRZAATX | µmol/l | No unit conversion required |
| PO4 | µg-at/l | Concentration of phosphate | PHOSAATX | µmol/l | No unit conversion required |
| Si | µg-at/l | Concentration of silicate | SLCAAATX | µmol/l | No unit conversion required |
| NH3 | µg-at/l | Concentration of ammonia | AMONAATX | µmol/l | No unit conversion required |
