0703S Discrete CTD Inorganic Nutrient Sampling Document
Originator's Protocol for Data Acquisition and Analysis
Sample collection
An occupation of the Extended Ellett Line (Stations A to 15G) was carried out as part of FRV Scotia cruise 0703S. 20 CTD casts in total were performed on the transect between 15 April and 5 May 2003. Discrete dissolved inorganic nutrients were drawn from water bottles fired ar a range of depths during these casts.
Dissolved silicate, nitrate and phosphate, were collected in plastic bottles and stored on ice until analysis, which occurred within 10 hours of sample collection.
Sample analysis
The unfiltered samples were analysed on board via continuous flow analysis using a QuAAtro autoanalyser or a SPX Bran+Luebbe colorimetric Autoanalyser 3.
The samples were calibrated against stock solutions of nitrite, nitrate and phosphate and a lab prepared stock solution of silicate. These stocks were diluted into a mixed working stock each day of analysis in nutrient depleted sea water. Additional dilution of this daily stock with more nutrient depleted sea water gave the working calibrants.
The full methods for nutrient analysis were supplied to BODC by the data originator.
BODC Data Processing Procedures
Inorganic nutrient data, together with associated metadata, were supplied to BODC in Excel format during June 2014. Values were extracted and loaded into BODC's relational database. Any data that were considered unrealistic were flagged suspect.
Content of data series
| Originator's Parameter | Unit | Description | BODC Parameter code | BODC Unit | Comments |
|---|---|---|---|---|---|
| Si | µg-at/l | Concentration of silicate {SiO4} per unit volume of the water body [dissolved plus reactive particulate phase] by colorimetric autoanalysis | SLCAAATX | µmol/l | µg-at/l = µmol/l, no unit conversion necessary |
| NO3 | µg-at/l | Concentration of nitrate+nitrite {NO3+NO2} per unit volume of the water body [dissolved plus reactive particulate phase] by colorimetric autoanalysis | NTRZAATX | µmol/l | µg-at/l = µmol/l, no unit conversion necessary |
| PO4 | µg-at/l | Concentration of phosphate {PO4} per unit volume of the water body [dissolved plus reactive particulate phase] by colorimetric autoanalysis | PHOSAATX | µmol/l | µg-at/l = µmol/l, no unit conversion necessary |
