## 3 Results
### River Water  
Radioactive concentrations of \({}^{137}\)Cs and \({}^{134}\)Cs in unfiltered river water during 2012-2016 are given in Table 2. The results of river mouth samples were not included in the table because the \({}^{137}\)Cs and \({}^{134}\)Cs concentrations were low, and they were a mixture of river water and sea water containing salt. The averaged \({}^{137}\)Cs concentrations in unfiltered river water for each year are shown in Figure 4b. Temporal changes of the \({}^{137}\)Cs concentration in river water were observed, similar to the sediments. Figure 4: (**a**) Temporal decrease of average concentration of \({}^{137}\)Cs in sediments for the four rivers in 2012–2016. (**b**) Temporal decrease of average concentration of \({}^{137}\)Cs in unfiltered river water for the four rivers in 2012–2016. +++ ==ERROR: No output for this page== \begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**River**} & \multirow{2}{*}{**Site**} & \multicolumn{2}{c}{**October 2012**} & \multicolumn{2}{c}{**November 2013**} & \multicolumn{2}{c}{**December 2014**} & \multicolumn{2}{c}{**November 2015**} & \multicolumn{2}{c}{**October 2016**} \\ \cline{3-11}  & & \multicolumn{2}{c}{**137 Cs**} & \multicolumn{2}{c}{**134 Cs**} & \multicolumn{2}{c}{**137 Cs**} & \multicolumn{2}{c}{**134 Cs**} & \multicolumn{2}{c}{**137 Cs**} & \multicolumn{2}{c}{**134 Cs**} & \multicolumn{2}{c}{**137 Cs**} & \multicolumn{2}{c}{**134 Cs**} & \multicolumn{2}{c}{**137 Cs**} & \multicolumn{2}{c}{**134 Cs**} \\ \hline \multirow{4}{*}{Odaka} & DS & 104(10) & 69(9) & 83(10) & 27(8) & 61(6) & 8(3) & 80(8) & ND * & 80(4) & ND \\  & DQ & 114(11) & 51(8) & 92(13) & 24(9) & 38(5) & ND & 85(9) & 7(2) & 55(3) & ND \\  & DQ & 89(9) & 48(7) & 102(14) & 29(11) & 50(6) & 11(4) & 53(6) & 8(6) & 52(3) & ND \\  & D2 & 95(9) & 39(7) & 117(15) & 27(11) & 33(5) & 8(4) & 22(5) & ND & 25(1) & ND \\ \hline \multirow{4}{*}{Otha} & OS & 446(38) & 287(28) & 265(27) & 81(21) & 203(8) & 55(7) & 116(11) & 33(8) & 119(6) & 10(1) \\  & Q4 & 290(27) & 205(18) & 258(28) & 85(17) & 126(12) & 30(6) & 70(7) & 25(8) & 113(6) & 13(1) \\  & O3 & 232(30) & 17(17) & 154(18) & 35(14) & 76(8) & 17(4) & 50(6) & 15(7) & 77(4) & ND \\  & O2 & 242(22) & 182(19) & 113(17) & 39(16) & 71(6) & 14(4) & 48(6) & ND & 88(4) & ND \\ \hline \multirow{4}{*}{Niida} & NS & 419(38) & 316(31) & 159(16) & 72(11) & 58(6) & 15(4) & 52(6) & ND & 10(1) & ND \\  & N4 & - & 229(22) & 95(13) & 27(4) & ND & 56(5) & ND & 9(1) & ND \\  & N3 & 110(13) & 75(8) & 59(8) & 30(7) & 29(4) & ND & 31(4) & ND & 13(1) & ND \\  & N2 & 95(9) & 38(7) & 85(10) & 47(8) & 15(3) & ND & 47(7) & 11(6) & 15(7) & ND \\ \hline \multirow{4}{*}{Mizunashi} & P4 & - & - & 222(21) & 78(12) & 108(10) & 68(15) & 137(9) & 36(8) & 63(3) & ND \\  & P3 & 385(34) & 271(28) & 98(13) & 21(11) & 116(11) & 80(16) & 86(6) & 26(9) & 49(4) & ND \\  & P2 & 140(14) & 118(14) & 138(14) & 63(11) & 74(7) & 39(12) & 53(5) & 8(4) & 42(2) & ND \\  & P1 & - & - & - & - & 87(9) & 70(14) & 47(5) & 13(5) & 33(3) & ND \\ \hline \multirow{4}{*}{[PERSON]} & MS & 109(7) & 44(2) & 38(5) & 14(5) & 31(4) & ND & 24(3) & ND & ND & ND \\  & M4 & 166(7) & 81(4) & 28(5) & 11(7) & 15(3) & ND & 10(2) & ND & 7(2) & ND \\ \cline{1-1}  & M3 & 68(5) & 31(2) & 32(5) & ND & 21(3) & ND & ND & ND & 12(2) & ND \\ \cline{1-1}  & M2 & 132(8) & 60(3) & 24(5) & ND & 14(3) & ND & 7(3) & ND & ND & ND \\ \hline \hline \end{tabular}
* ND indicates under detection limit  
\end{table} 
Table 2: Concentrations of \({}^{137}\)Cs and \({}^{134}\)Cs in unfiltered river water sampled in the Minami-Soma City during 2012-2016. (Units: Bq.L\({}^{-1}\)). Since unfiltered water sample was utilized for the \({}^{137}\)Cs measurement in the present work, the \({}^{137}\)Cs concentration might be higher compared to the dissolved component only. We compared the \({}^{137}\)Cs concentration in filtered/unfiltered, i.e., the dissolved component to the total amount for river water samples at D2 (the Odaka River), O2 (the Ohta River), N5 (the Niida River), and M5 (the Mano River) in 2015.