AMT1 Nutrient (micromolar) measurements from CTD bottle samples
Originator's Protocol for Data Acquisition and Analysis
This data originates from analyses of bottle samples taken from 25 CTD casts.
The samples were taken from vertical profiles at each station. They were stored in the dark at less than 4°C in a laboratory refrigerator and were analysed as a batch shortly after the CTD samples were obtained. Thus, the vertical profile samples were usually analysed within one hour of collection.
Nutrients were analysed using a four-channel segmented-flow auto-analyser. The determinations were made using a Technicon Autoanalyser II running conventional chemistries: phosphate and silicate as described by Kirkwood (1989) and nitrate and nitrite using a modified version of Grasshoff's method as described by Brewer and Riley (1965). The nitrate was determined as nitrite using a copper-cadmium reduction column to reduce nitrate to nitrite and is, therefore, measured as nitrate plus nitrite.
References Cited
Brewer, P.G. and J.P. Riley (1965) The automatic determination of nitrate in sea water. Deep-Sea Res., 12, 765-772.
Kirkwood, D.S. (1989) Simultaneous determination of selected nutrients in seawater. ICES CM1989/C:29, 12pp.
Instrumentation Description
Technicon Autoanalyser II
BODC Data Processing Procedures
Data were submitted to BODC in Microsoft Excel spreadsheet format. Sample metadata were checked against information held in the database. Originator's sample ID was matched based on latitude/longitude and bottle firing depth. Originator file provided latitude labelled as longitude and longitude labelled as latitude. Station/Sample reference provided is the Julian day that sampling took place on. These were matched to the CTD casts that took place at midday (ship's time) each day on the cruise.
There was no phosphate data for 1 sample (CTD24/Sample 296 at depth 40m) - indicated by ND in originator's file. There was a replicate measurement provided at 140 m on CTD16 (Station/Sample 284). The mean of these 2 measurements for each parameter was entered into the database for the bottle sampled at this depth.
Parameter codes defined in BODC parameter dictionary were assigned to the variables. The data were assigned parameter codes defined in BODC parameter dictionary. Data loaded into BODC's database using established BODC data banking procedures.
A parameter mapping table is provided below;
| Originator's Parameter | Units | Description | BODC Parameter Code | Units | Comments |
|---|---|---|---|---|---|
| Nitrate+Nitrite | µmol l -1 | Concentration of nitrate+nitrite {NO 3 +NO 2 } per unit volume of the water body [dissolved plus reactive particulate phase] by colorimetric autoanalysis | NTRZAATX | µmol l -1 | - |
| Nitrite | µmol l -1 | Concentration of nitrite {NO 2 } per unit volume of the water body [dissolved plus reactive particulate phase] by colorimetric autoanalysis | NTRIAATX | µmol l -1 | - |
| Phosphate | µmol l -1 | Concentration of phosphate {PO 4 } per unit volume of the water body [dissolved plus reactive particulate phase] by colorimetric autoanalysis | PHOSAATX | µmol l -1 | - |
| Silicate | µmol l -1 | Concentration of silicate {SiO 4 } per unit volume of the water body [dissolved plus reactive particulate phase] by colorimetric autoanalysis | SLCAAATX | µmol l -1 | - |
Data Quality Report
The dataset has been checked by the data originator - any suspect data values were removed from the data set before submission to BODC. The data originator highlighted samples with concentrations below the specified detection limits and these are flagged in the database with a flag of "<".
Problem Report
Not relevant to this data set.
