sediments sampled in the Swedish Marine Environmental Monitoring - PowerPoint PPT Presentation

Concentrations and inventories of 137 Cs in dated sediments sampled in the Swedish Marine Environmental Monitoring Program Mats Eriksson, Pål Andersson Swedish Radiation Safety Authority

Swedish Marine Environmental Monitoring Program - aimed to study trends in pollutions Sampling • SGU ship, Ocean Surveyor • Gemini sediment corer used • 7 double cores at each station • Cruises, 2003,2008,2014

Samples collected 2008 • SGU collected and freeze-dried the sediments • SSM contracted DTU NUTECH in Denmark to measure selected sediment layers for their content of 137Cs, 210Pb and 208Tl • SSM analyzed the results and performed the dating of the cores

Sediment model • Three independent models were used • Cs-137 time marker in the sediment profile (Chernobyl peak assumed to represent the year 1986) • Pb-210 sediment model (assuming constant flux and concentration of Pb-210) • Th-228 sediment model (where sedimentation rate was high, assuming constant flux and concentration of Th-228)

Sediment model, Pb-210 (assuming constant flux and concentration of Pb-210) SE-1 08_0163, Ref.dato: 01-07-2008 1890 +/- 11 1877 +/- 12 1865 +/- 14 1852 +/- 15 2005 +/- 1 1998 +/- 1 1992 +/- 2 1979 +/- 3 1967 +/- 4 1954 +/- 5 1941 +/- 6 1928 +/- 8 1916 +/- 9 + + 800 • Pb-210 sediment model (assuming A x A 0 exp depth sed.rate Pb sup constant flux and concentration of Ex.Pb (at x=0), A0 = 822.6 +/- 37.1 Bq/kg 600 Sedimentation rate = 0.16 +/- 0.01 cm/y + + Activity [Bq/kg] Pb-210): Supported Pb = 60.4 +/- 12.8 Bq/kg Cs-137 Sedimentation rate = 0.14 +/- 0.05 cm/y – A(x)=A (0) exp(- λ * x / sed.rate) + Pb sup 400 • Using nonlinear (weighted) least- squares fitting in R 200 • Fitted A0, sedimentation rate and + supported Pb-210 + + + • 0 Advantage: Ra-226 not necessary, easy and fast method 0 5 10 15 20 25 Depth [cm]

Sediment model, Th-228 (assuming constant flux and concentration of Th-228) SE-16 08_0025, Ref.dato: 01-07-2008 Sedimentation model, A = A0*exp(-lambda*depth/sed.rate)+supported Th-228 Th-228 2008 +/- 0 2007 +/- 0 2006 +/- 0 2005 +/- 1 2004 +/- 1 2002 +/- 1 2001 +/- 1 2000 +/- 2 1998 +/- 2 1997 +/- 2 1996 +/- 3 1994 +/- 3 1993 +/- 3 1992 +/- 3 1.91 y 250 • Th-228 (t 1/2 = 1.9 y) determined from its daughter Tl-208 Ra-224 3.66 d • Th-228 sediment model (assuming 200 constant flux and concentration of Th- Ex.Th-228 (at x=0), A0 = 222.7 +/- 19.3 Bq/kg Rn-222 228): Activity [Bq/kg] Sedimentation rate = 1.49 +/- 0.3 cm/y 55.6 s 150 Supported Th-228 = 34.6 +/- 8.2 Bq/kg – A(x)=A (0) exp(- λ * x / sed.rate) + Th sup Po-216 • 0.14 s Using nonlinear (weighted) least-squares 100 fitting in R Pb-212 • Fitted A0, sedimentation rate and 10.6 h supported Th-228 50 • Advantage: can be used where Bi-212 sedimentation is high (over 1cm/y) 60.6 s 0 Tl-208 212Po 3.05 m 0.30 µs 0 5 10 15 20 25 Depth [cm] Pb-208 stable

Results: Bothnian Bay and Bothnian Sea SE-17 08_0170, Ref.dato: 01-07-2008 1960 +/- 10 1949 +/- 12 1938 +/- 14 1927 +/- 17 1915 +/- 19 1893 +/- 24 1882 +/- 26 1870 +/- 28 2005 +/- 1 2000 +/- 2 1994 +/- 3 1983 +/- 5 1971 +/- 8 600 500 A x A 0 exp depth sed.rate Pb sup Ex.Pb (at x=0), A0 = 548.9 +/- 40.4 Bq/kg 400 Sedimentation rate = 0.18 +/- 0.04 cm/y Activity [Bq/kg] SE-1 08_0163, Ref.dato: 01-07-2008 Supported Pb = 27.6 +/- 27.7 Bq/kg + Cs-137 Sedimentation rate = 0.18 +/- 0.05 cm/y 1890 +/- 11 1877 +/- 12 1865 +/- 14 1852 +/- 15 300 2005 +/- 1 1998 +/- 1 1992 +/- 2 1979 +/- 3 1967 +/- 4 1954 +/- 5 1941 +/- 6 1928 +/- 8 1916 +/- 9 + + + + + 800 200 A x A 0 exp depth sed.rate Pb sup 100 Ex.Pb (at x=0), A0 = 822.6 +/- 37.1 Bq/kg 600 + + Sedimentation rate = 0.16 +/- 0.01 cm/y Activity [Bq/kg] + Supported Pb = 60.4 +/- 12.8 Bq/kg + Cs-137 Sedimentation rate = 0.14 +/- 0.05 cm/y + 0 400 0 5 10 15 20 25 Depth [cm] 200 SE-2 08_0156, Ref.dato: 01-06-2008 + 2007 +/- 0 2006 +/- 0 2004 +/- 1 2001 +/- 1 1998 +/- 2 1995 +/- 2 1992 +/- 3 1989 +/- 3 1986 +/- 4 1983 +/- 4 1980 +/- 5 1977 +/- 5 1974 +/- 6 1971 +/- 6 + + 500 + 0 0 5 10 15 20 25 A x A 0 exp depth sed.rate Pb sup 400 Ex.Pb (at x=0), A0 = 254.2 +/- 17.6 Bq/kg Depth [cm] Sedimentation rate = 0.67 +/- 0.12 cm/y Activity [Bq/kg] Supported Pb = 128.7 +/- 13.7 Bq/kg 300 Cs-137 Sedimentation rate = 0.66 +/- 0.09 cm/y SE-3 08_0149, Ref.dato: 01-06-2008 + + 500 + 200 + 2007 +/- 0 2004 +/- 1 2001 +/- 1 1996 +/- 1 1990 +/- 2 1985 +/- 2 1979 +/- 3 1974 +/- 4 1968 +/- 4 1963 +/- 5 1957 +/- 5 1952 +/- 6 1946 +/- 6 1941 +/- 7 + + + + + Note: Cs-137 act is devide by 5 + 100 400 A x A 0 exp depth sed.rate Pb sup + + + Ex.Pb (at x=0), A0 = 369 +/- 16.1 Bq/kg + 0 + 300 Sedimentation rate = 0.37 +/- 0.04 cm/y Activity [Bq/kg] Supported Pb = 47.1 +/- 9.9 Bq/kg 0 5 10 15 20 25 Cs-137 Sedimentation rate = 0.39 +/- 0.09 cm/y + Depth [cm] 200 SE-4 08_0095, Ref.dato: 01-06-2008 + + + + 500 2007 +/- 0 2004 +/- 0 2002 +/- 1 1997 +/- 1 1993 +/- 2 1988 +/- 2 1983 +/- 3 1978 +/- 3 1974 +/- 4 1969 +/- 4 1964 +/- 5 1959 +/- 5 1955 +/- 6 1950 +/- 6 100 + 400 Note: Cs-137 act is devide by 5 A x A 0 exp depth sed.rate Pb sup + + + 0 + + + + Ex.Pb (at x=0), A0 = 260.9 +/- 13.4 Bq/kg Sedimentation rate = 0.42 +/- 0.05 cm/y Activity [Bq/kg] 300 Supported Pb = 138.2 +/- 9.6 Bq/kg 0 5 10 15 20 25 Cs-137 Sedimentation rate = 0.39 +/- 0.09 cm/y Depth [cm] 200 + + + Note: Cs-137 act is devide by 5 100 + + + + + + + + + + + 0 0 5 10 15 20 25

Results Baltic Proper SE-8 08_0081, Ref.dato: 01-07-2008 1984 +/- 10 2008 +/- 0 2007 +/- 1 2006 +/- 1 2004 +/- 2 2002 +/- 3 2000 +/- 3 1998 +/- 4 1996 +/- 5 1994 +/- 6 1992 +/- 7 1990 +/- 7 1988 +/- 8 1986 +/- 9 SE-5 08_0088, Ref.dato: 01-06-2008 1000 1500 2008 +/- 0 2007 +/- 1 2006 +/- 1 2004 +/- 2 2002 +/- 2 2000 +/- 3 1998 +/- 4 1996 +/- 4 1994 +/- 5 1992 +/- 6 1990 +/- 7 1988 +/- 7 1986 +/- 8 1984 +/- 9 A x A 0 exp depth sed.rate Pb sup 800 Ex.Pb (at x=0), A0 = 677.6 +/- 116.6 Bq/kg Sedimentation rate = 1.03 +/- 0.42 cm/y Activity [Bq/kg] A x A 0 exp depth sed.rate Pb sup Supported Pb = 93.7 +/- 85.5 Bq/kg 1000 Ex.Pb (at x=0), A0 = 835.2 +/- 122.6 Bq/kg 600 Cs-137 Sedimentation rate = 1.02 +/- 0.09 cm/y Sedimentation rate = 1.03 +/- 0.37 cm/y Activity [Bq/kg] Supported Pb = 38.8 +/- 94.6 Bq/kg Cs-137 Sedimentation rate = 0.93 +/- 0.09 cm/y 400 500 200 + + + + + + + + + + + + + + + + + + + + + + + + + + + + 0 0 0 5 10 15 20 25 0 5 10 15 20 25 Depth [cm] Depth [cm] SE-9 08_0074, Ref.dato: 01-07-2008 SE-6 08_0067, Ref.dato: 01-07-2008 800 1862 +/- 11 1817 +/- 15 1772 +/- 18 1727 +/- 22 1682 +/- 25 1637 +/- 29 1592 +/- 32 1547 +/- 36 1502 +/- 39 1458 +/- 42 2007 +/- 0 2006 +/- 0 2005 +/- 0 2003 +/- 1 2001 +/- 1 1998 +/- 1 1996 +/- 1 1994 +/- 1 1991 +/- 2 1989 +/- 2 1987 +/- 2 1985 +/- 2 1982 +/- 3 1980 +/- 3 1997 +/- 2 1974 +/- 3 1952 +/- 5 1907 +/- 8 1200 1000 A x A 0 exp depth sed.rate Pb sup A x A 0 exp depth sed.rate Pb sup 600 Ex.Pb (at x=0), A0 = 896.5 +/- 33.6 Bq/kg Ex.Pb (at x=0), A0 = 776.9 +/- 38.3 Bq/kg Sedimentation rate = 0.88 +/- 0.09 cm/y Activity [Bq/kg] 800 Supported Pb = 99.2 +/- 16 Bq/kg Sedimentation rate = 0.045 +/- 0.003 cm/y Activity [Bq/kg] Cs-137 Sedimentation rate = 0.75 +/- 0.09 cm/y Supported Pb = 88.8 +/- 5.8 Bq/kg 600 Cs-137 Sedimentation rate = 0.02 +/- 0.05 cm/y 400 400 + + + 200 + 200 + + + + + + + + + + + 0 + + + 0 5 10 15 20 25 + + 0 Depth [cm] 0 5 10 15 20 25 SE-7 08_0060, Ref.dato: 01-07-2008 Depth [cm] 1953 +/- 10 1929 +/- 14 1904 +/- 18 1880 +/- 22 1855 +/- 26 1831 +/- 31 1806 +/- 35 1782 +/- 39 1758 +/- 43 1733 +/- 47 1200 2002 +/- 2 1990 +/- 3 1977 +/- 5 1000 A x A 0 exp depth sed.rate Pb sup Ex.Pb (at x=0), A0 = 1155.9 +/- 100.5 Bq/kg 800 Sedimentation rate = 0.08 +/- 0.01 cm/y Activity [Bq/kg] Supported Pb = 60.9 +/- 28.4 Bq/kg Cs-137 Sedimentation rate = 0.02 +/- 0.05 cm/y 600 400 200 + + + + + + 0 0 5 10 15 20 25 Depth [cm]