Radioactive Substance Fall Out in Tokyo

I have downloaded all the necessary data to draw the above graph (the data from 1957 to 2009 was from  Environmental Radioactivity Monitoring in Japan and the data from March to April 2011 was from Tokyo Metropolitan Government).

The total amount of the 137 Cs fall out from April, 1957 to December 2009 is 6,500 Bq/m2 (0.18 Ci/km2). On the other hand, the total amount of the 137 Cs fall out from March, 2011 to April, 2011 is 7,000 Bq/m2 (0.19 Ci/km2).

In the past, large amounts of 137 Cs fall out were observed from 1950s to 1960s in Tokyo due to intensive atmospheric nuclear testings in the world outside Japan. In addition, the 137 Cs fall out was also observed in May, 1986 one month after the Chernobyl nuclear disaster.

However, much more amounts of 137 Cs fall out were detected in the past two months. We are facing an unprecedented accident.

The situation gets much worse in Ibaraki Prefecture, which is located much closer to Fukushima Daiichi nuclear plant than Tokyo. The total amount of 137 Cs fall out from March, 2011 to April, 2011 in Hitachinaka city, Ibaraki Prefecture was 29,000 Bq/m2 (0.78 Ci /km2). The data of Hitachinaka city was obtained from MEXT.

I write the original data to draw the above graph as the followings;

 Year,Month,137Cs Monthly Fall Out in Tokyo [Bq/m2]
1957,1,0.00E+00
1957,2,0.00E+00
1957,3,0.00E+00
1957,4,4.07E+01
1957,5,7.25E+01
1957,6,1.48E+02
1957,7,3.81E+01
1957,8,1.92E+01
1957,9,7.18E+01
1957,10,1.59E+01
1957,11,9.99E+00
1957,12,1.04E+01
1958,1,7.40E+00
1958,2,1.52E+01
1958,3,4.44E+01
1958,4,3.40E+01
1958,5,4.96E+01
1958,6,4.66E+01
1958,7,5.37E+01
1958,8,3.15E+01
1958,9,3.66E+01
1958,10,4.85E+01
1958,11,1.78E+01
1958,12,3.70E+01
1959,1,4.00E+01
1959,2,4.70E+01
1959,3,1.35E+02
1959,4,1.44E+02
1959,5,1.93E+02
1959,6,1.31E+02
1959,7,4.59E+01
1959,8,2.85E+01
1959,9,2.66E+01
1959,10,1.37E+01
1959,11,2.37E+01
1959,12,1.55E+01
1960,1,1.33E+01
1960,2,2.59E+01
1960,3,2.66E+01
1960,4,3.74E+01
1960,5,2.37E+01
1960,6,2.37E+01
1960,7,1.52E+01
1960,8,8.88E+00
1960,9,7.40E+00
1960,10,1.30E+01
1960,11,5.18E+00
1960,12,3.70E+00
1961,1,3.33E+00
1961,2,3.33E+00
1961,3,7.40E+00
1961,4,1.26E+01
1961,5,7.40E+00
1961,6,3.40E+01
1961,7,4.07E+00
1961,8,2.96E+00
1961,9,1.11E+01
1961,10,1.19E+02
1961,11,1.18E+01
1961,12,2.63E+01
1962,1,2.41E+01
1962,2,1.96E+01
1962,3,6.99E+01
1962,4,9.51E+01
1962,5,1.42E+02
1962,6,1.43E+02
1962,7,5.92E+01
1962,8,2.59E+01
1962,9,9.99E+00
1962,10,5.40E+01
1962,11,1.07E+02
1962,12,5.55E+01
1963,1,2.22E+01
1963,2,3.77E+01
1963,3,1.79E+02
1963,4,2.15E+02
1963,5,1.94E+02
1963,6,5.29E+02
1963,7,1.89E+02
1963,8,1.02E+02
1963,9,9.21E+01
1963,10,1.16E+02
1963,11,2.07E+01
1963,12,1.55E+01
1964,1,4.59E+01
1964,2,2.63E+01
1964,3,7.18E+01
1964,4,8.88E+01
1964,5,3.85E+01
1964,6,5.70E+01
1964,7,3.00E+01
1964,8,1.96E+01
1964,9,2.11E+01
1964,10,1.70E+01
1964,11,1.33E+01
1964,12,1.07E+01
1965,1,1.44E+01
1965,2,1.92E+01
1965,3,6.22E+01
1965,4,5.70E+01
1965,5,7.84E+01
1965,6,6.73E+01
1965,7,1.85E+01
1965,8,3.59E+01
1965,9,9.25E+00
1965,10,1.15E+01
1965,11,8.14E+00
1965,12,7.77E+00
1966,1,7.40E+00
1966,2,2.00E+01
1966,3,8.88E+00
1966,4,1.44E+01
1966,5,4.11E+01
1966,6,4.07E+01
1966,7,9.99E+00
1966,8,7.03E+00
1966,9,4.07E+00
1966,10,7.40E+00
1966,11,3.33E+00
1966,12,1.85E+00
1967,1,1.07E+01
1967,2,9.25E+00
1967,3,6.29E+00
1967,4,1.04E+01
1967,5,8.14E+00
1967,6,1.22E+01
1967,7,2.59E+00
1967,8,1.48E+00
1967,9,1.85E+00
1967,10,3.33E+00
1967,11,1.48E+00
1967,12,3.70E-01
1968,1,3.70E+00
1968,2,2.22E+00
1968,3,7.77E+00
1968,4,1.59E+01
1968,5,1.26E+01
1968,6,5.92E+00
1968,7,1.85E+00
1968,8,6.29E+00
1968,9,5.18E+00
1968,10,6.29E+00
1968,11,1.48E+00
1968,12,3.70E+00
1969,1,2.22E+00
1969,2,3.33E+00
1969,3,3.33E+00
1969,4,7.03E+00
1969,5,1.18E+01
1969,6,7.40E+00
1969,7,1.26E+01
1969,8,4.81E+00
1969,9,4.44E+00
1969,10,7.03E+00
1969,11,1.85E+00
1969,12,1.11E+00
1970,1,2.59E+00
1970,2,1.48E+00
1970,3,4.44E+00
1970,4,1.15E+01
1970,5,1.26E+01
1970,6,3.37E+01
1970,7,1.11E+01
1970,8,4.44E+00
1970,9,4.07E+00
1970,10,3.70E+00
1970,11,2.96E+00
1970,12,1.11E+00
1971,1,1.44E+00
1971,2,1.92E+00
1971,3,3.33E+00
1971,4,1.69E+01
1971,5,1.37E+01
1971,6,1.77E+01
1971,7,1.18E+01
1971,8,3.40E+00
1971,9,3.70E+00
1971,10,2.66E+00
1971,11,7.40E-01
1971,12,7.40E-01
1972,1,5.18E+00
1972,2,4.44E+00
1972,3,2.22E+00
1972,4,3.70E+00
1972,5,3.70E+00
1972,6,8.14E+00
1972,7,4.44E+00
1972,8,1.85E+00
1972,9,4.44E+00
1972,10,1.11E+00
1972,11,7.40E-01
1972,12,1.11E+00
1973,1,8.51E-01
1973,2,1.85E+00
1973,3,1.11E+00
1973,4,2.74E+00
1973,5,2.55E+00
1973,6,2.66E+00
1973,7,1.59E+00
1973,8,5.92E-01
1973,9,9.25E-01
1973,10,2.59E-01
1973,11,5.92E-01
1973,12,2.59E-01
1974,1,7.40E-01
1974,2,1.85E+00
1974,3,5.18E+00
1974,4,6.66E+00
1974,5,7.40E+00
1974,6,1.59E+01
1974,7,9.99E+00
1974,8,2.26E+00
1974,9,1.92E+00
1974,10,1.85E+00
1974,11,1.11E+00
1974,12,1.85E+00
1975,1,2.41E+00
1975,2,2.00E+00
1975,3,3.00E+00
1975,4,7.18E+00
1975,5,4.81E+00
1975,6,2.41E+00
1975,7,1.30E+00
1975,8,3.70E-01
1975,9,6.29E-01
1975,10,2.11E+00
1975,11,8.88E-01
1975,12,2.59E-01
1976,1,2.22E-01
1976,2,1.07E+00
1976,3,1.44E+00
1976,4,2.07E+00
1976,5,1.30E+00
1976,6,1.18E+00
1976,7,4.44E-01
1976,8,4.81E-01
1976,9,5.18E-01
1976,10,1.63E+00
1976,11,5.18E-01
1976,12,1.48E-01
1977,1,3.70E-01
1977,2,4.07E-01
1977,3,1.92E+00
1977,4,2.63E+00
1977,5,1.63E+00
1977,6,5.18E+00
1977,7,4.81E+00
1977,8,6.29E+00
1977,9,1.70E+00
1977,10,8.51E-01
1977,11,1.63E+00
1977,12,1.44E+00
1978,1,7.40E-01
1978,2,2.78E+00
1978,3,2.89E+00
1978,4,8.51E+00
1978,5,7.77E+00
1978,6,3.07E+00
1978,7,4.81E-01
1978,8,4.07E-01
1978,9,1.67E+00
1978,10,7.40E-01
1978,11,1.11E+00
1978,12,7.77E-01
1979,1,6.66E-01
1979,2,1.04E+00
1979,3,1.96E+00
1979,4,2.70E+00
1979,5,3.22E+00
1979,6,5.18E-01
1979,7,1.26E+00
1979,8,5.92E-01
1979,9,4.44E-01
1979,10,6.29E-01
1979,11,4.81E-01
1979,12,2.22E-01
1980,1,3.70E-01
1980,2,1.48E-01
1980,3,8.88E-01
1980,4,1.26E+00
1980,5,1.30E+00
1980,6,9.62E-01
1980,7,9.99E-01
1980,8,2.96E-01
1980,9,4.07E-01
1980,10,2.59E-01
1980,11,3.70E-01
1980,12,2.59E-01
1981,1,1.48E-01
1981,2,5.92E-01
1981,3,3.07E+00
1981,4,4.07E+00
1981,5,5.55E+00
1981,6,2.70E+00
1981,7,1.96E+00
1981,8,9.99E-01
1981,9,5.92E-01
1981,10,3.70E-01
1981,11,2.59E-01
1981,12,1.11E-01
1982,1,0.00E+00
1982,2,4.07E-01
1982,3,8.51E-01
1982,4,1.04E+00
1982,5,6.29E-01
1982,6,8.88E-01
1982,7,5.18E-01
1982,8,1.48E-01
1982,9,1.48E-01
1982,10,1.11E-01
1982,11,1.11E-01
1982,12,0.00E+00
1983,1,1.11E-01
1983,2,1.11E-01
1983,3,2.59E-01
1983,4,2.59E-01
1983,5,2.59E-01
1983,6,2.22E-01
1983,7,1.11E-01
1983,8,7.40E-02
1983,9,0.00E+00
1983,10,1.11E-01
1983,11,1.85E-01
1983,12,7.40E-02
1984,1,0.00E+00
1984,2,1.11E-01
1984,3,4.44E-01
1984,4,1.11E-01
1984,5,1.85E-01
1984,6,1.11E-01
1984,7,0.00E+00
1984,8,1.11E-01
1984,9,0.00E+00
1984,10,7.40E-02
1984,11,0.00E+00
1984,12,7.40E-02
1985,1,0.00E+00
1985,2,1.11E-01
1985,3,1.11E-01
1985,4,1.48E-01
1985,5,0.00E+00
1985,6,7.40E-02
1985,7,0.00E+00
1985,8,0.00E+00
1985,9,0.00E+00
1985,10,7.40E-02
1985,11,0.00E+00
1985,12,0.00E+00
1986,1,0.00E+00
1986,2,7.40E-02
1986,3,1.11E-01
1986,4,1.11E-01
1986,5,1.78E+02
1986,6,0.00E+00
1986,7,1.70E+00
1986,8,5.92E-01
1986,9,2.96E-01
1986,10,2.22E-01
1986,11,1.11E-01
1986,12,5.18E-01
1987,1,6.66E-01
1987,2,9.62E-01
1987,3,2.59E-01
1987,4,1.11E-01
1987,5,1.85E-01
1987,6,1.11E-01
1987,7,1.85E-01
1987,8,1.48E-01
1987,9,7.40E-02
1987,10,7.40E-02
1987,11,0.00E+00
1987,12,1.11E-01
1988,1,7.40E-02
1988,2,0.00E+00
1988,3,1.48E-01
1988,4,1.00E-01
1988,5,9.00E-02
1988,6,0.00E+00
1988,7,0.00E+00
1988,8,0.00E+00
1988,9,0.00E+00
1988,10,0.00E+00
1988,11,0.00E+00
1988,12,0.00E+00
1989,1,7.00E-02
1989,2,0.00E+00
1989,3,0.00E+00
1989,4,1.00E-01
1989,5,0.00E+00
1989,6,0.00E+00
1989,7,0.00E+00
1989,8,0.00E+00
1989,9,0.00E+00
1989,10,0.00E+00
1989,11,0.00E+00
1989,12,0.00E+00
1990,1,5.00E-02
1990,2,5.00E-02
1990,3,0.00E+00
1990,4,5.20E-02
1990,5,0.00E+00
1990,6,0.00E+00
1990,7,0.00E+00
1990,8,7.90E-02
1990,9,0.00E+00
1990,10,0.00E+00
1990,11,0.00E+00
1990,12,0.00E+00
1991,1,0.00E+00
1991,2,0.00E+00
1991,3,0.00E+00
1991,4,0.00E+00
1991,5,0.00E+00
1991,6,0.00E+00
1991,7,0.00E+00
1991,8,0.00E+00
1991,9,0.00E+00
1991,10,0.00E+00
1991,11,0.00E+00
1991,12,0.00E+00
1992,1,0.00E+00
1992,2,0.00E+00
1992,3,0.00E+00
1992,4,7.40E-02
1992,5,0.00E+00
1992,6,0.00E+00
1992,7,0.00E+00
1992,8,0.00E+00
1992,9,0.00E+00
1992,10,0.00E+00
1992,11,0.00E+00
1992,12,0.00E+00
1993,1,0.00E+00
1993,2,0.00E+00
1993,3,5.63E-02
1993,4,9.18E-02
1993,5,0.00E+00
1993,6,0.00E+00
1993,7,0.00E+00
1993,8,0.00E+00
1993,9,0.00E+00
1993,10,0.00E+00
1993,11,0.00E+00
1993,12,0.00E+00
1994,1,0.00E+00
1994,2,0.00E+00
1994,3,0.00E+00
1994,4,0.00E+00
1994,5,0.00E+00
1994,6,0.00E+00
1994,7,0.00E+00
1994,8,0.00E+00
1994,9,0.00E+00
1994,10,0.00E+00
1994,11,0.00E+00
1994,12,0.00E+00
1995,1,0.00E+00
1995,2,0.00E+00
1995,3,0.00E+00
1995,4,0.00E+00
1995,5,0.00E+00
1995,6,0.00E+00
1995,7,0.00E+00
1995,8,0.00E+00
1995,9,0.00E+00
1995,10,0.00E+00
1995,11,0.00E+00
1995,12,0.00E+00
1996,1,0.00E+00
1996,2,0.00E+00
1996,3,0.00E+00
1996,4,0.00E+00
1996,5,0.00E+00
1996,6,0.00E+00
1996,7,0.00E+00
1996,8,0.00E+00
1996,9,0.00E+00
1996,10,0.00E+00
1996,11,0.00E+00
1996,12,0.00E+00
1997,1,0.00E+00
1997,2,0.00E+00
1997,3,0.00E+00
1997,4,0.00E+00
1997,5,0.00E+00
1997,6,0.00E+00
1997,7,0.00E+00
1997,8,0.00E+00
1997,9,0.00E+00
1997,10,0.00E+00
1997,11,0.00E+00
1997,12,0.00E+00
1998,1,0.00E+00
1998,2,0.00E+00
1998,3,0.00E+00
1998,4,0.00E+00
1998,5,0.00E+00
1998,6,0.00E+00
1998,7,0.00E+00
1998,8,0.00E+00
1998,9,0.00E+00
1998,10,0.00E+00
1998,11,0.00E+00
1998,12,0.00E+00
1999,1,0.00E+00
1999,2,0.00E+00
1999,3,0.00E+00
1999,4,0.00E+00
1999,5,0.00E+00
1999,6,0.00E+00
1999,7,0.00E+00
1999,8,0.00E+00
1999,9,0.00E+00
1999,10,0.00E+00
1999,11,0.00E+00
1999,12,0.00E+00
2000,1,0.00E+00
2000,2,0.00E+00
2000,3,4.90E-02
2000,4,4.80E-02
2000,5,0.00E+00
2000,6,0.00E+00
2000,7,0.00E+00
2000,8,0.00E+00
2000,9,0.00E+00
2000,10,0.00E+00
2000,11,0.00E+00
2000,12,0.00E+00
2001,1,0.00E+00
2001,2,0.00E+00
2001,3,0.00E+00
2001,4,0.00E+00
2001,5,0.00E+00
2001,6,0.00E+00
2001,7,0.00E+00
2001,8,0.00E+00
2001,9,0.00E+00
2001,10,0.00E+00
2001,11,0.00E+00
2001,12,0.00E+00
2002,1,0.00E+00
2002,2,0.00E+00
2002,3,3.70E-02
2002,4,3.50E-02
2002,5,0.00E+00
2002,6,0.00E+00
2002,7,0.00E+00
2002,8,0.00E+00
2002,9,0.00E+00
2002,10,0.00E+00
2002,11,0.00E+00
2002,12,0.00E+00
2003,1,0.00E+00
2003,2,0.00E+00
2003,3,0.00E+00
2003,4,0.00E+00
2003,5,0.00E+00
2003,6,0.00E+00
2003,7,0.00E+00
2003,8,0.00E+00
2003,9,0.00E+00
2003,10,0.00E+00
2003,11,0.00E+00
2003,12,0.00E+00
2004,1,0.00E+00
2004,2,0.00E+00
2004,3,0.00E+00
2004,4,0.00E+00
2004,5,0.00E+00
2004,6,0.00E+00
2004,7,0.00E+00
2004,8,0.00E+00
2004,9,0.00E+00
2004,10,0.00E+00
2004,11,0.00E+00
2004,12,0.00E+00
2005,1,0.00E+00
2005,2,0.00E+00
2005,3,0.00E+00
2005,4,0.00E+00
2005,5,0.00E+00
2005,6,0.00E+00
2005,7,0.00E+00
2005,8,0.00E+00
2005,9,0.00E+00
2005,10,0.00E+00
2005,11,0.00E+00
2005,12,0.00E+00
2006,1,0.00E+00
2006,2,0.00E+00
2006,3,3.90E-02
2006,4,7.00E-02
2006,5,0.00E+00
2006,6,0.00E+00
2006,7,0.00E+00
2006,8,0.00E+00
2006,9,0.00E+00
2006,10,0.00E+00
2006,11,0.00E+00
2006,12,0.00E+00
2007,1,0.00E+00
2007,2,0.00E+00
2007,3,0.00E+00
2007,4,6.00E-02
2007,5,0.00E+00
2007,6,0.00E+00
2007,7,0.00E+00
2007,8,0.00E+00
2007,9,0.00E+00
2007,10,0.00E+00
2007,11,0.00E+00
2007,12,0.00E+00
2008,1,0.00E+00
2008,2,0.00E+00
2008,3,0.00E+00
2008,4,4.30E-02
2008,5,0.00E+00
2008,6,0.00E+00
2008,7,0.00E+00
2008,8,0.00E+00
2008,9,0.00E+00
2008,10,0.00E+00
2008,11,0.00E+00
2008,12,0.00E+00
2009,1,0.00E+00
2009,2,0.00E+00
2009,3,0.00E+00
2009,4,0.00E+00
2009,5,0.00E+00
2009,6,0.00E+00
2009,7,0.00E+00
2009,8,0.00E+00
2009,9,0.00E+00
2009,10,0.00E+00
2009,11,0.00E+00
2009,12,0.00E+00
2011,3,6.56E+03
2011,4,3.59E+02