In order to evaluate the impact of the Fukushima nuclear accident on the China Seas, seawater samples from the South China Sea (SCS), the East China Sea (ECS) and the Yellow Sea (YS) were collected in April-June 2011, and their 137 Cs activities were measured using low-background -spectrometry. 137Cs activities in the study area ranged from 0.75±0.07 to 1.43±0.08 Bqm 3 with an average of 1.12±0.08 Bq m 3 . 137Cs activities initially increased from the nearshore to the inner shelf, and subsequently decreased from the inner shelf to the outer shelf. Vertical profiles showed higher 137Cs activities at the surface but lower activities at depth in the ECS, suggesting atmospheric input of 137Cs. As such, the distribution pattern of 137Cs in the region was presumably determined by a combination of atmospheric deposition and subsequent mixing between different water masses including the coastal currents, the Yangtze River plume and the Taiwan Warm Currents. Based on the inventory of 93 Bq m2 and the atmospheric deposition flux of 137Cs in the ECS of 32.2 mBq m2 d1 (5.4-42.9 mBq m 2 d1 ) which we estimated, we derived the residence time of 137Cs in the upper water column to be 66d (45-95 d). We concluded that in terms of 137Cs, the ECS was less impacted by the Fukushima accident as compared to the Chernobyl accident. The released amount of 137Cs into the ECS from the Fukushima accident was minute.
The first regional mapping of the averaged turbulent kinetic energy dissipation rate <εp> in the upper pycnocline of the northern South China Sea is presented and discussed.At φ=20°N and to the north of this latitude,<εp> appears to be more than two times larger than that to the south of 20°N.It is suggested that this asymmetry is associated with the predominant northwestward propagation and dissipation of the internal waves originated in the Luzon Strait area.An approximately linear relationship between <εp> and the available potential energy of the waves P IW,suggests a characteristic time of the P IW dissipation of about 6 h.
