Data Processing:
Nitrate = (Nitrate+nitrite) – nitrite

Samples were measured in triplicate (flag =6).

Samples out of linear calibration range for LWCC (flag = 10).

Related files and references:
Karl, D. M. and G. Tien (1992). "MAGIC: A sensitive and precise method for measuring dissolved phosphorus in aquatic environments." Limnology and Oceanography 37(1): 105-116.

Li, Q. P. and D. A. Hansell (2008). "Intercomparison and coupling of magnesium-induced co-precipitation and long-path liquid-waveguide capillary cell techniques for trace analysis of phosphate in seawater." Analytica Chimica Acta 611(1): 68-72.

Li, Q. P., D. A. Hansell, et al. (2008). "Underway monitoring of nanomolar nitrate plus nitrite and phosphate in oligotrophic seawater." Limnology and Oceanography: Methods 6: 319-326.

Murphy, J. and J. P. Riley (1962). "A modified single solution method for the determination of phosphate in natural waters." Analytica Chimica Acta 27: 31-36.

Patey, M. D., M. J. A. Rijkenberg, et al. (2008). "Determination of nitrate and phosphate in seawater at nanomolar concentrations." TrAC Trends in Analytical Chemistry 27(2): 169-182.

Zhang, J.-Z. (2000). "Shipboard automated determination of trace concentrations of nitrite and nitrate in oligotrophic water by gas-segmented continuous flow analysis with a liquid waveguide capillary flow cell." Deep Sea Research Part I: Oceanographic Research Papers 47(6): 1157-1171.

BCO-DMO Processing Notes
- Generated from original spreadsheet file "GEOTRACES Knorr199-4 and -5 nanomolar nutrients.xls", sheet: "St. 1-12 depth profile" contributed by Greg Cutter
- Parameter names modified to conform to BCO-DMO convention
- cruise_id added
- Cast, Type, Event, date and time added from cast and event logs
- longitude values converted to negative (West)
- "nd" (no data flag) inserted into blank cells
- Changed event number of sample 6000 from 'nd' to '2215'. (correct event number confirmed by GT10 event log).
- Corrected event number of sample 5622 from 2157 to 2171 (14 March 2013).

Additional GEOTRACES Processing:
After the data were submitted to the International Data Management Office, BODC, the office noticed that important identifying information was missing in many datasets. With the agreement of BODC and the US GEOTRACES lead PIs, BCO-DMO added standard US GEOTRACES information, such as the US GEOTRACES event number, to each submitted dataset lacking this information. To accomplish this, BCO-DMO compiled a 'master' dataset composed of the following parameters: station_GEOTRC, cast_GEOTRC (bottle and pump data only), event_GEOTRC, sample_GEOTRC, sample_bottle_GEOTRC (bottle data only), bottle_GEOTRC (bottle data only), depth_GEOTRC_CTD (bottle data only), depth_GEOTRC_CTD_rounded (bottle data only), BTL_ISO_DateTime_UTC (bottle data only), and GeoFish_id (GeoFish data only). This added information will facilitate subsequent analysis and inter comparison of the datasets.

Bottle parameters in the master file were taken from the GT-C_Bottle_GT10, GT-C_Bottle_GT11, ODF_Bottle_GT10, and ODF_Bottle_GT11 datasets. Non-bottle parameters, including those from GeoFish tows, Aerosol sampling, and McLane Pumps, were taken from the Event_Log_GT10 and Event_Log_GT11 datasets. McLane pump cast numbers missing in event logs were taken from the Particulate Th-234 dataset submitted by Ken Buesseler.

A standardized BCO-DMO method (called "join") was then used to merge the missing parameters to each US GEOTRACES dataset, most often by matching on sample_GEOTRC or on some unique combination of other parameters.

If the master parameters were included in the original data file and the values did not differ from the master file, the original data columns were retained and the names of the parameters were changed from the PI-submitted names to the standardized master names. If there were differences between the PI-supplied parameter values and those in the master file, both columns were retained. If the original data submission included all of the master parameters, no additional columns were added, but parameter names were modified to match the naming conventions of the master file.

See the dataset parameters documentation for a description of which parameters were supplied by the PI and which were added via the join method.

Nutrients_Profiles_joined.csv