RADIOACTIVITY IN THE BALTIC SEA 1984 - 1991

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ID Helsinki Commission

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Table of Contents

PREFACE

EXECUTIVE SUMMARY

INTRODUCTION

SOURCES OF RADIOACTIVITY IN THE BALTIC SEA

Fallout

Global Fallout

Sr-90 and Cs-137 Deposition in the Baltic Sea Area

Contents of Sr-90 and Cs- 137 in Soil

Chernobyl Fallout

Source Estimation for Cs-137 Based on Cs-134 Measurements

Source Estimation for Cs-137 Based on Profiles in Seawater in 1986 and from Cs- 137 Increments

in Sediments

River Run-off 13

2.2. Discharges from Western European Nuclear Reprocessing Plants 13

2.3. Discharges from Nuclear Installations in the Baltic Sea Area 13

2.4. Conclusions 17

References 18

3. MONITORING NETWORK

Stations 19

Measured Parameters 22

Description of the HELCOM Databases 28

QUALITY OF DATA

4.1. Analytical Procedures Used by Laboratories Involved in MORS 30

4.1.1. Pretreatment of Marine Samples 30

4.1.2. Analytical Methods 31

4.1.2.1. Gamma Spectrometry 31

4.1.2.2. Radiochemical Determination of Caesium 35

4.1.2.3. Radiochemical Determination of Strontium-90 36

4.1.2.4. Radiochemical Determination of Transuranium Elements 37

4.2. Quality Assurance, Internal and External Checking 40

4.3. Intercalibrations Carried out 42

4.3.1. Historical Background 42

4.3.2. List of Exercises 43

4.3.3. Data Treatment 44

4.3.4. Discussion 45

4.4. Conclusion 57

References 57

RADIONUCLIDES IN SEAWATER

Introduction

Origin and Distribution of Radionuclide Concentrations in the Baltic Sea

Temporal Evolution

Inventories in Seawater

References

RADIONUCLIDES IN SEDIMENT AND SUSPENDED PARTICULATE MATTER

Introduction 69

Sampling Techniques 69

Description of Sediment Types 72

Sedimentation Rates 75

Activity Concentrations in Sediments and Time Trends 78

Activity Concentrations in Suspended Particulate Matter 86

Inventories in Sediments 90

References 91

7. RADIONUCLIDES IN BIOTA

Introduction

Some Important Biota in the Baltic Sea

Species Investigated

Sampling Methods

Radionuclides Studied

7.2. Fish 99

7.2.1. Cs-137 in Fish 99

7.2.2. Other Radionuclides in Fish 103

7.3. Invertebrates 105

7.3.1. Cs- 137 in Invertebrates 105

7.3.2. Other Radionuclides in Invertebrates 106

Algae

Concentration Factors

References 119

8. MODELLING THE TRANSFER OF RADIONUCLIDES IN THE BALTIC SEA

8.1. Description of Models 121

8.2. Source Terms

8.3. Model Results for Cs-137

8.4. Model Results for Sr-90 140

8.5. Conclusions

References

9. DOSE CALCULATIONS

9.1. Assumptions Concerning Seafood Consumption 149

Doses

Individual Dose Rates

Collective Dose Rates and Collective Doses

Comparison with Doses from Natural Radionuclides 156 9.3.

9.4 Conclusions 156

References 157

10. CONCLUSIONS 159

ACKNOWLEDGEMENTS 164

ANNEX 165

BALTIC SEA ENVIRONMENT PROCEEDINGS 176