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Abstract: Radioisotopes from dry and wet atmospheric deposition (i.e., 7Be, 210Pb and 137Cs) can be used to determine the sources, fluxes and rates of internal processes in sedimentary compartments such as rivers, estuaries and oceans. The activities of 7Be, excess 210Pb (210Pbex) and 137Cs in surface sediments collected in the Changjiang Estuary during May and June of 2007 were measured to elucidate the routes and budgets of these radionuclides and the sediment transport. The ranges of the activities of 7Be, 210Pbex and 137Cs were 0.0–34.6, 0.39–2.90 and 8.0–214.0Bqkg−1, with averages of 9.8, 1.56 and 43.5Bqkg−1, respectively. Based on the material balance of inputs (riverine loading, atmospheric deposition) and outputs (decay, burial into sea bed) of 7Be, 210Pb and 137Cs, the calculated results indicate that around 35% of both the 210Pbex and 7Be total inputs in the Changjiang Estuary should be exported out of this area. However, the evaluated results showed that 83% of the 137Cs total input into the Changjiang Estuary should be from offshore and/or the south. These phenomena can be explained by the current structure of the water mass around this region. Changjiang Dilute Water (CDW), with sediment, is first moved to the south and northeast. Then, the Zhejiang–Fujian Coast Current (ZFCC), with sediment, can travel farther south. Moreover, the Jiangsu Coast Current (JCC), with sediment from the Yellow Sea, can approach the Changjiang Estuary. However, both the Taiwan Warm Current/upwelling and the ZFCC can carry fine sediment with 137Cs to the Changjiang Estuary. [ABSTRACT FROM AUTHOR]

The behavior and source of 90 Sr in the coastal ocean remain uncertain. Here, we investigated the distributions of 90 Sr in coastal fresh groundwater, river water, pore water, and seawater in three bays along the southeastern coast of China between 2019 and 2021 and evaluated the potential of submarine groundwater discharge (SGD) as a source of coastal 90 Sr. The 90 Sr activity in coastal fresh groundwater was higher than that in river water and seawater, while the 90 Sr activity in pore water was comparable to that in adjacent seawater. In addition, nonconservative mixing behavior of 90 Sr along the salinity gradient between river water and seawater was observed. These observations indicated that fresh SGD may serve as an additional source of 90 Sr in coastal seawater. Combining our groundwater 90 Sr data with the reported fresh SGD flux data, the estimated fresh SGD-derived 90 Sr fluxes into the three bays were comparable to or even higher than those supplied by riverine sources. These results revealed that fresh SGD is a major but overlooked source of 90 Sr in the coastal ocean. This subterranean pathway for transport of 90 Sr to the coastal ocean should be considered in the monitoring and risk assessment of coastal areas, especially those near nuclear facilities.

The 90 Sr activities of seawater were investigated in the high-latitude region of the Arctic Ocean from August-September 2017. The 90 Sr activities in seawater in the Chukchi Sea, central Arctic Ocean and East Greenland Sea were 0.31-2.42, 0.12-1.86 and 0.13-1.20 Bq m -3 , respectively. The average 90 Sr activity (0.92 Bq m -3 ) below 500 m in the central Arctic Ocean was higher than those in previous reports. Our study provided high-resolution baseline 90 Sr activity data for the whole water column in the high-latitude region of the Arctic Ocean (~85°N). The inventory of 90 Sr in the central Arctic Ocean was higher than those in the Chukchi Sea and East Greenland Sea. The results of our study indicated that 90 Sr could be transported to the deep seawater and remain in the Arctic Ocean for a long time., (Copyright © 2019 Elsevier Ltd. All rights reserved.)