www.bsh.de

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A *

A HgCl2B *

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F HgCl2

µmol/L

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A HgCl2

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z-score

-3,00 -2,00 -1,00 0,00 1,00 2,00

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A HgCl2

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z-score

-3,00 -2,00 -1,00 0,00 1,00 2,00

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z-score

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AA *A HgCl2B *B HgCl2C *C HgCl2D *D HgCl2E *E HgCl2F *F HgCl2

µmol/L

Interlaboratory Comparison of NutrientSeawater Samples in the German BightSieglinde Weigelt-Krenz*; Rita Kramer*; Thomas Raab e**

Conclusions• There are comparable results for onboard measureme nts as well as for analyses of deep frozen and HgCl 2 preserved samples.• The z-scores for almost all institutes are between -2 and +2.• The comparability of North Sea water analysis meth ods for dissolved nutrients is assured within the participating la boratories.

The results confirm that a common standard for nutr ient analysis exists amongGerman laboratories and thus, German monitoring tas ks are fulfilled in aneffectual way. However, some additional work on the storage and analysis ofammonium has to be done.

One aim for the near future will be to exten d this intercomparison project to the international community in order to ensu re comparability of nutrient results within the whole OSPAR region.

AbstractIn 2007 and 2008, an intercomparison exercise for n utrient analysis of seawater samples was carried out by six independent Ge rman laboratories. Mainobjective was to compare different conservation tec hniques (deep freezing orpoisoning with mercury chloride, HgCl 2) as well as the different analyticalmethods used by the investigators. The samples were analysed for dissolvednitrate+nitrite, nitrite, ortho-phosphate, silicate and ammonium.The sea water samples were taken in the German Bigh t during two monitoringcruises in March 2007 and March 2008. The samples w ere divided into 250-ml-aliquots, of which one was directly measured onboar d the research vessel withSFA (segmented flow analysis). The other aliquots w ere simultaneouslydistributed among the participating laboratories, h alf of them being conservedby deep-freezing at -18 °C, the other half being po isoned by HgCl 2 (stored at 4-8°C), respectively. All samples were processed with in a fixed time-frame.The analysed data were compared and evaluated accor ding to Gofino et al.(2004). One laboratory failed at the analysis of ph osphate and ammonium.Apart from that the interlaboratory variability was generally less than 10 % fornitrate+nitrite, nitrite, silicate and phosphate. F or ammonium the variabilityranged between 0.5 and 45 %. This clearly revealed methodic problems for thestorage and/or analysis of ammonium samples.

Results and statistical evaluation

Winteraverage(2004-2008)of DIN(dissolvedinorganicnitrogencompounds)in the bottomwater of theGermanBight.

Water sampling and sample processing

* Bundesamt für Seeschifffahrt und Hydrographie (Federal Maritime and Hydrographic Agency); Wüstland 2; 22589 Hamburg; Germany** AquaEcology; Marie-Curie-Straße 1; 26129 Oldenburg; Germany

Distribution pattern of DIN in the German Bight

The results [µmol/L] of six independant laboratorie s (A-F) are exemplarily summedup for nitrite, slilicate and ammonium at seven st ations in the German Bight (S =28,3-35,0). The differences are evaluated statistic ally according to Cofino et al. (2004).

Literature: D.E. Wells, W.P. Cofino and J.A. Scurfield (2004). The Application of the Cofino Model to evaluate LaboratoryPerformance Study Data using the Bandwith Estimator. Fisheries Research Services Collaborative Report No 04/04

1

Nitrite

Z-score (nitrite) at station 3 referring to the ass igned value (AV); AV = 0,88 µmol/L

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Intercalibration samples

Silicate

Z-score (silicate) at station 1 referring to the as signed value (AV); AV= 31,40 µmol/L

Z-score (ammonium) at station 1 referring to the as signed value (AV); AV= 3,68 µmol/L(without laboratory C)

Ammonium

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z-score

z-score

z-score