Distribution and Source Identification of Pu in River Basins in Southern China

Abstract

The 239+240Pu activities and 240Pu/239Pu atom ratios in surface sediments from the major river basins in southern China were analyzed to investigate the distribution and source of Pu. We clarified that the 239+240Pu activities in these river basins were very similar, however, only the 239+240Pu activities in the Jinjiang Basin were generally higher than other samples. Because of river transport function, the distribution of 239+240Pu activities in these river basins presented an increasing trend from the upstream region to the estuary. According to the 240Pu/239Pu atom ratios, the Pu source in the inner river basins might be from global fallout, and the Pu in river estuaries might be from the global fallout and the Pacific Proving Grounds (PPG) in the Marshall Islands. Using a mass balance of the Pu model, we quantified in the Pearl River Estuary and the Pu contribution from the Pearl River Basin to Pu inventory was 13 ± 5%. These data not only filled in a knowledge gap of Pu in these river basins but also served as background data for Pu contamination from a nuclear reactor. Also, there are several planned and operating nuclear power plants in these river basins and these data could provide some indications for dealing with nuclear accidents in different parts of river basins in the future. In this study, we also analyzed some factors that would affect the distribution of 239+240Pu activities; however, only total organic carbon (TOC) content and the heavy metal As had a positive correlation with the 239+240Pu activity.

237Np and 241Am as Fingerprints in the Major River Basins of Southern China and North South China Sea: A Land–Sea Perspective

“…As we stated in Section , the current 237 Np/ 239 Pu atom ratio and 241 Am/ 239+240 Pu activity ratio are quite different from the reference values, so it is hard to identify the source directly. Previous studies , on Pu isotopes showed that the sources of Pu this study are PPG and global fallout (including Pearl River input) and the contribution of PPG was approximately 60–71% in NSCS, 49–69% in Pearl River Estuary, and 30 ± 10% in the major river basins of southern China. Due to the inseparable relationship between feature fingerprints of 237 Np and 241 Am and 239,240 Pu, we continue to use the reported data on the Pu isotope ratio in this study area and believed that the sources of Am and Np in this study area are also global sedimentation and PPG.…”

“…North Equatorial Current (NEC) and Kuroku Current (KC) transport the Pu to the north South China Sea (NSCS) continuously supplied by Pacific Proving Ground (PPG). In addition to the ocean current input, the terrestrial nuclides brought by the Pearl River input also have a certain effect on the distribution of radionuclides in the downstream estuarine area . The sediments in NSCS are mainly terrigenous materials imported from Pearl River and coastal water systems, and their distribution is affected by coastal currents and tides. , Besides, Taishan and Yangjiang nuclear power plants are built on the coast of the NSCS.…”

Distribution and source of Pu in the sediments of the seas and estuaries of China—a review

“…Therefore, the transport of coastal currents and sediment dynamics of fine particles might play an important role in controlling the spatial distribution of Pu isotopes in the surface sediment of the northern Yellow Sea (Xu et al 2018). In addition, the fine particles might absorb more total organic carbon content, and the total organic carbon content also has a certain influence on the distribution of 239+240 Pu activity (Wang et al 2019b).…”

“…Relationship between 239+240 Pu activity and 240 Pu/ 239 Pu atom ratio in the surface sediments of different seas and estuaries of China. Su and Huh 2002;Lee et al 2003;Wang and Yamada 2005;Hong et al 2006;Zheng and Yamada 2006;Liu et al 2011a;Pan et al 2011;Wu et al 2014;Wang et al 2017;Wang et al 2019b;Zhuang et al 2019).…”

“…There are two main input channels of Pu isotopes in the ocean: one is global fallout from atmospheric nuclear tests ( 240 Pu/ 239 Pu = 0.179 ± 0.019) (Kelley et al 1999), and the other is from the United States nuclear test sites in the Marshall islands in the Pacific Ocean (Pacific Proving Grounds, PPG) (Muramatsu et al 2001) ( 240 Pu/ 239 ). In the past decades, numerous studies have been carried out to investigate source terms, transport, and scavenging and deposition processes of Pu isotopes in an inland sea (Bohai Sea), three marginal seas (Yellow Sea, East China Sea, and South China Sea), and some estuaries of China (Huh and Su 1999;Su and Huh 2002;Lee et al 2003;Wang and Yamada 2005;Hong et al 2006;Zheng and Yamada 2006;Dong et al 2010;Liu et al 2011a;Pan et al 2011;Wu et al 2014Wu et al , 2020Wang et al 2017;Wang et al 2019aWang et al , 2019bXu et al 2018;Guan et al 2020;Zhang et al 2020) (Table 1). In particular, many previous studies have also reported that the sources of Pu in the marginal seas of China are mainly from extensive atmospheric nuclear weapons tests since 1945 and close-in fallout from the PPG (where a series of US nuclear tests were conducted in the 1940s-1950s) through ocean currents and water masses based on 240 Pu/ 239 Pu atom ratios (0.30-0.36) (Huh and Su 1999;Su and Huh 2002;Lee et al 2003;Wang and Yamada 2005;Hong et al 2006;Zheng and Yamada 2006;Dong et al 2010;Liu et al 2011a;Pan et al 2011;Wu et al 2014…”