A Study of the Impact of the Fukushima Nuclear Leak on East China Coastal Regions

Figures & data

Fig. 1 (a) Bathymetry (m) for the two-domain, one-way nesting model. The yellow and green dots mark the stations for OA, and the red ones are those listed in Table 6 for validation. The red box indicates the inner domain (L1). (b) Enlarged view of the ECS, namely, L1. The sections where the fluxes are calculated are shown. A: Taiwan Strait, B: East of Taiwan, C: Ishigaki to Naha, D: Naha to Amami, E: Tokara Strait, F: Tsushima Strait, G: from Ishigaki northward to 27.5°N. Also marked is a section of the East China coast (dashed purple line).

Table 1. Parameters for the two-domain nested ROMS model.

Domain	Maximum Depth (m)	Minimum Depth (m)	Latitude (°N)	Longitude (°E)	Resolution (km)	Time Step (s)
L0	5000	15	0–68	96–288	10.1	900
L1	5000	10	24–41	117–135	3.6	90

Table 6. ¹³⁷Cs concentrations from the IAEA observations in the North Pacific, Run 1, and Run 2 (January–March 2012)^a.

Date	Latitude (°N)	Longitude (°E)	Observation (Bq m^−3)	Run 1 (Bq m^−3)	Run 2 (Bq m^−3)
3 January 2012	22.11	191.46	1.6	0	1.49
5 January 2012	22.97	179.98	1.6	0	1.48
21 January 2012	34.45	130.08	1.7	0	1.22
21 January 2012	34.45	130.08	1.4	0	1.22
22 January 2012	32.53	132.98	1.6	0	1.34
22 January 2012	32.53	132.98	1.3	0	1.34
29 January 2012	26.89	182.06	1.6	0.01	1.75
30 January 2012	27.84	189.10	2.1	0	1.76
31 January 2012	32.98	197.06	1.7	4.08	2.55
1 February 2012	33.05	204.72	1.6	0	3.01
2 February 2012	34.26	213.10	2	0	1.69
3 February 2012	35.16	220.91	2.2	0	1.70
4 February 2012	48.99	219.18	1.3	0	1.41
4 February 2012	36.36	228.83	1.7	0	1.66
5 February 2012	47.53	228.13	1.4	0	1.41
17 February 2012	26.82	173.34	2.4	0.12	1.60
24 February 2012	32.29	206.67	1.6	0	4.08
29 February 2012	34.53	175.90	9.6	1.81	5.72
2 March 2012	33.42	196.11	2.1	1.61	2.18
2 March 2012	39.46	177.47	13.6	4.53	12.38
4 March 2012	30.09	211.27	1.7	0	1.58
9 March 2012	40.45	133.84	1.7	0	1.11
16 March 2012	31.92	223.18	1.6	0	1.71
21 March 2012	34.86	177.27	5.8	3.77	2.34

^aFor the data for a longer period (June 2011–September 2012), see http://www.ncoads.org/article/show/68.aspx

Table 2. Tidal constituents.

Symbol	Species	Period (hr)	Speed (° hr^−1)
M2	Principal lunar semi-diurnal	12.42060120	28.9841042
S2	Principal solar semi-diurnal	12.00000000	30.0000000
N2	Larger lunar elliptic semi-diurnal	12.65834751	28.4397295
K2	Lunisolar semi-diurnal	11.96723606	30.0821373
K1	Lunar diurnal	23.93447213	15.0410686
O1	Lunar diurnal	25.81933871	13.9430356
P1	Solar diurnal	24.06588766	14.9589314
Q1	Larger lunar elliptic diurnal	26.86835000	13.3986609
Mf	Lunisolar fortnightly	327.8599387	1.0980331
Mm	Lunar monthly	661.3111655	0.5443747

Table 3. Comparison of surface layer (0.5 m) ¹³⁷Cs radioactive concentration between observations (Wu et al., 2013) and simulations in this study.

Date	Latitude (°N)	Longitude (°E)	Observations (Bq m^−3)	Simulation results
				Concentration (Bq m^−3)	Relative Errors (%)
7 June 2011	32.01	126.48	1.01 ± 0.06	1.22	20
8 June 2011	36.05	123.50	1.10 ± 0.07	1.20	10
5 May 2011	20.50	122.29	1.14 ± 0.07	1.25	9
2 June 2011	29.64	123.04	1.32 ± 0.13	1.19	−10
7 June 2011	32.00	124.00	1.33 ± 0.10	1.19	−11
8 May 2011	18.00	116.00	1.42 ± 0.09	1.38	−2

Fig. 2 Annual mean sea surface temperature (SST) and velocity for 2011 in the North Pacific Ocean. The left and right columns show the distributions of SST and speed, respectively; the velocity vectors are superimposed on the maps. (a) and (b) show the results from our simulation, and (c) and (d) are derived from SODA. (e) and (f) show the difference between model outputs and SODA data.

Fig. 3 ECS SST (shaded) and velocity (vectors) in winter and summer. (a) ROMS outputs, February; (b) HYCOM result, February; (c) ROMS outputs, August; and (d) HYCOM result, August.

Table 4. Observations and the simulation output around ST-1 in 2012.

Date	Latitude (°N)	Longitude (°E)	Observation (Bq m^−3)	Simulation (Bq m^−3)
20 July 2012	36.005	155.01	1.3	1.5029
20 July 2012	38.010	155.08	1.8	1.4704
28 September 2012	44.575	156.08	2.2	1.6281
10 July 2012	44.000	155.01	3.0	2.0234
20 July 2012	37.010	155.01	1.1	1.5122
20 July 2012	36.462	155.06	1.1	1.5141
10 July 2012	43.012	155.01	2.8	1.4121
2 March 2012	37.500	161.82	9.4	4.9418
20 July 2012	35.002	155.01	3.6	1.4819
20 July 2012	40.002	155.01	3.6	1.4143
20 July 2012	40.512	155.01	6.5	1.9625
10 July 2012	40.997	155.06	8.0	4.6775
20 July 2012	39.505	155.05	5.5	1.4605
10 July 2012	42.530	155.10	6.5	1.5892
31 May 2012	38.500	160.00	9.3	5.1883

Fig. 4 Simulated surface distribution of ¹³⁷Cs in the North Pacific.

Fig. 5 Vertical profiles of ¹³⁷Cs at specific Pacific stations in our simulation.

Table 5. Observations and the simulation output around ST-2 in 2012.

Date	Latitude (°N)	Longitude (°E)	Observation (Bq m^−3)	Simulation (Bq m^−3)
1 February 2012	33.050	204.72	1.6	1.7778
1 February 2012	27.840	189.10	2.1	1.8100
2 March 2012	33.420	196.11	2.1	3.1536
1 February 2012	32.980	197.06	1.7	3.5128

Fig. 6 (a)–(f) Time series of the ¹³⁷Cs fluxes across the six waterways indicated in Fig. 1b (10⁶ Bq s⁻¹). Positive values indicate fluxes into the ECS; black lines are the moving averages with a window of 6 months. In (a) the red line (moving average in green) indicates the difference between the fluxes across the two sections B and G in Fig. 1b. (b) The red curve (moving average in green) is the flux across section G. (g) Total accumulation of nuclear pollutants in ECS (PBq). In all the panels, the April–September periods are shaded in yellow.

Table 7. Inflow flux through the six sections averaged over the period April 2011–December 2025. Negative values indicate outflow fluxes.

Section	Inflow Flux (10^6 Bq s^−1)	Section	Inflow Flux (10^6 Bq s^−1)
Taiwan Strait	2.81	East of Taiwan	37.01
Ishigaki to Naha	0.54	Naha to Amami	0.35
Tokara Strait	−38.99	Tsushima Strait	−2.18

Fig. 7 (a) Distribution of the simulated maximum surface ¹³⁷Cs concentration (lines, Bq m⁻³) and the year when it was attained (see colour bar). (b) Distribution of the maximum monthly mean ¹³⁷Cs radioactive concentration (lines, Bq m⁻³) and the months when the maximum was attained (shaded). The monthly mean is taken over the same months from 2014 to 2019. (c) Hovmöller diagram of ¹³⁷Cs concentration (shaded, Bq m⁻³) between 25°N and 37°N (green line in Fig. 1b) along the East China coast from 2011 to 2022.

Fig. 8 Distributions of monthly mean surface ¹³⁷Cs concentration in the ECS from 2014 to 2019 for (a) January, (b) April, (c) July, and (d) October.

Wu, J. W., Zhou, K. B., & Dai, M. H. (2013). Impacts of the Fukushima nuclear accident on the China Seas: Evaluation based on anthropogenic radionuclide 137Cs. Chinese Science Bulletin, 58(4-5), 552–558. doi: 10.1007/s11434-012-5426-2

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