D340A Discrete Dissolved Inorganic Nutrients Sampling Document
Originator's Protocol for Data Acquisition and Analysis
Water samples were drawn from the CTD rosette bottles deployed during the cruise with the majority of the sampling effort concentrated in areas of the water column corresponding with changes in water mass and changes in algal mass.
Samples were collected in 250 ml acid cleaned polythene bottles directly from CTD spigots without the use of a tube. Samples were stored in a fridge prior to analysis. The analysis was carried out within 24 hours of sample collection with a Lachat Quick Chem 8500 flow injection autoanalyser using the manufacturer's recommended methods. Standards were prepared in deionised water and samples were run in a carrier stream of deionised water.
Salt corrections were performed by running a small number of Low Nutrient Sea Water samples during each sample batch run with the mean result being subtracted from sample results.
References Cited
Sherwin T. A. et al. , 2009. Cruise D340A Reykjavic to Dunstaffnage via Rockall and the Wyville Thomson Ridge. Internal Report No 264. Scottish Association for Marine Science.
Available - Cruise D430A Internal Report
BODC Data Processing Procedures
The nutrient data were supplied to BODC in Microsoft Excel format. Values were extracted from these and saved in ASCII format prior to being loaded into BODC's ocean database under the ORACLE Relational Database Management System. Data that were considered unrealistic were flagged suspect.
SAMS nitrate data quality warning
SAMS have notified BODC of a problem in the analytical procedure adopted for nitrate analysis on this cruise. The problem relates to the technique used to prepare the analytical standards, which results in nitrate (and consequently nitrite) values which are typically 10-15 % higher than they should be. Absolute data values should therefore be used with extreme caution.
Content of data series
| Originator's Parameter | Originator's Unit | Description | BODC's Parameter Code | BODC's Unit | Comments |
|---|---|---|---|---|---|
| Ammonium | µM | Concentration of ammonium in the water column by colorimetric autoanalysis (unfiltered) | AMONAATX | µM | n/a |
| Standard deviation of ammonium | µM | Concentration standard deviation of ammonium in the water column by colorimetric autoanalysis (unfiltered) | SDAMAATX | µM | n/a |
| Phosphate | µM | Concentration of phosphate in the water column by colorimetric autoanalysis (unfiltered) | PHOSAATX | µM | n/a |
| Standard deviation of phosphate | µM | Concentration standard deviation of phosphate in the water column by colorimetric autoanalysis (unfiltered) | SDPHAATX | µM | n/a |
| Silicate | µM | Concentration of silicate in the water column by colorimetric autoanalysis (unfiltered) | SLCAAATX | µM | n/a |
| Standard deviation of silicate | µM | Concentration standard deviation of silicate in the water column by colorimetric autoanalysis (unfiltered) | SLSDAATX | µM | n/a |
| Nitrate and nitrite | µM | Concentration of nitrate and nitrite in the water column by colorimetric autoanalysis (unfiltered) | NTRZAATX | µM | n/a |
| Standard deviation of nitrate and nitrite | µM | Concentration standard deviation of nitrate and nitrite in the water column by colorimetric autoanalysis (unfiltered) | SDNZAATX | µM | n/a |
Data Quality Report
A number of the values in the channels AMONAATX and SDAMAATX have negative values which have subsequently been flagged.
