Appendix: Data Quality 
Tarja K. Ikaheimonen, lisa Outola 
STUK, Radiation and Nuclear Safety Authority, Finland 
1 Introduction 
More than ten laboratories from the nine coun 
tries bordering Baltic Sea have contributed to 
the monitoring programmes of Baltic Sea by 
analyzing radionuclides from marine samples. 
The various analytical methods used in the 
different laboratories are summarized in the 
table below. Quality assurance is a fundamen 
tal part of radioanalytical work, needed to con 
firm the precision and the long-term repeata 
bility of analyses. Eight intercomparisons were 
organised during the project period 1999-2006 
for seawater and sediment samples, and their 
results are also presented below. 
2 Analytical procedures 
used by MORS laboratories 
The analytical methods in use (Table 1) 
have not changed notably since the last 
report (Ikaheimonen and Mulsow, 2003). 
Pretreatment of water samples is performed 
either by evaporation, adsorption on AMP, or 
using ferro-cyanide precipitation. Biota and 
sediment samples are generally dried and 
ashed. 137 Cs is measured by a high-purity Ge- 
detector, except in one country that used beta 
counting. 90 Sr is chemically separated using 
extraction, Sr-resin or various precipitations 
is monitored through proportional counting 
or LS counting. Traditional fuming nitric acid 
precipitation has generally been replaced by 
other chemical separation methods. U, Pu 
and Am are separated using anion exchange, 
extraction chromatography resins or liquid- 
liquid extraction followed by electroplating 
and alpha counting. A short description of 
the radiochemical methods used for natural 
radionuclides (Po, U, Th), 3 H and "Tc is also 
given in Table 1 for the first time. 
3 Quality assurance, internal 
and external checking 
The quality systems in use in different MORS 
laboratories are summarised in Table 2. 
Six laboratories have quality management 
systems in place, and four of these also 
employ accredited methods in their analytical 
work. All of the laboratories have participated 
in numerous intercomparisons during the 
study period, assuring good data quality. 
4 Intercalibration excercises (1999-2006) 
organized by the MORS group 
4.1 Sediment 
In June 2000 the MORS group arranged 
an intercomparison exercise together with 
IAEA using a sediment sample taken from 
the Bothnian Sea. A detailed description of 
the intercomparison is given by Ikaheimonen 
and Variti (2007). Eight laboratories from 
Denmark, Estonian, Finland, Germany, 
Latvia, Poland and Sweden participated in 
the intercomparison, and reported results 
for gamma nuclides, transuranic elements 
and natural radionuclides (Table 3). Results 
for 137 Cs and 239 240 Pu are shown in Figures 
1 and 2. The results indicated that the 
measurements by these eight laboratories are 
in quite good agreement. The difference from 
the mean value was statistically significant 
only in two cases among 41 results evaluated 
based on the z-scores. 
4.2 Seawater 
The capabilities of the MORS group in terms 
of analyzing seawater were tested with two 
different seawater samples. An IAEA-337 
sample was collected from the Gotland Deep 
(sampling site BY15) in July 1996 and then 
analyzed during the period 1999-2002 for 
137 Cs and 90 Sr. During the years 2004-2006 
the laboratories were asked to analyze 137 Cs 
and 90 Sr once a year from a seawater sample 
collected from the Bothnian Sea (sampling 
site EB1) in June 2004. The results of these 
intercomparisons are illustrated in Figures 3- 
6. The results indicate that the measurements 
are in very good agreement. The results 
were unsatisfactory only in 3 cases among 
68 results evaluated based on the z-scores. 
In addition to the intercomparisons organised 
by the MORS group, the laboratories