Dutch JGOFS - Nutrients measured during the North Atlantic Pilot Project (NAPP)

The North Atlantic Pilot Project (NAPP), also known as the North
Atlantic Bloom Experiment (NABE), was the first field work of JGOFS
(Joint Global Ocean Flux Study) and it served as pilot study for the
proposed North Atlantic Process Study. Six countries participated in
this study: Canada, France, Germany, The Netherlands, UK and USA

The Netherlands contributed to NAPP with four cruises on board
R.V. Tyro:
1. Leg 1, 31 July-11 September 1989 (Upper Ocean Processes)
2. Leg 2, 13-28 September 1989 (Benthic Processes)
3. Leg 3, 17 April-31 May 1990 (Upper Ocean Processes)
4. Leg 4, 2-29 June 1990 (Benthic Processes)

The present nutrient dataset derives from Leg 1. Orthophosphate,
nitrite and nitrate, ammonia and silicic acid were measured in 75 out
of a total of 76 stations at or neaby 20W between 33N and
61.5N. Seawater was drawn directly from the Rosette samplers into high
density polyethylene bottles which were rinsed twice with seawater
before filling. The seawater was not filtered and stored cool (4 deg
C) and dark prior to analysis within 12 hours. Standards made up in
sewater matrix were run along the sample determinations. All analyses
were done with Technicon Traacs 800 autoanalyzers employing the
following colorimetric methods:
* Orthophosphate. Formation of the reduced molybdophosphate complex at pH
0.9-1.1. PotassiumAntimonylTartrate as catalyst and Ascorbic Acid as
reductant. Final measurement at 885 nm wavelength
* Nitrite and Nitrate. Diazotization with sulfanylamide and naftylethylene-
diammoniumchloride, measurement at 540 nm.
* Ammonia. Fenol-hypochlorite and citrate as a buffer and complexing agent.
Measurement at 630 nm
* Silicic acid. Measured as the reduced molybdenum complex at 810 nm.
Ascorbic Acid as reductant.

>From station 20 cast 1 onwards we also measured surface water samples
for nitrate and nitrite in the low level range with a specially
modified Technicon aa II analyzer. The wet chemical methods is
otherwise the same as described above. Levels of NO3 below 1
micromol/kg and of NO2 below 0.01 micromol/kg were analyzed with this
procedure. The total number of samples analyzed on the two TRAACS 800
systems is about 1500, of which about 400 samples had to be rerun for
phosphate.

(Methodology extracted from Rommetz et al., Data Report, 1991)