129I and its species in the East China Sea: level, distribution, sources and tracing water masses exchange and movement

Abstract

Anthropogenic 129I as a long-lived radioisotope of iodine has been considered as an ideal oceanographic tracer due to its high residence time and conservative property in the ocean. Surface water samples collected from the East China Sea (ECS) in August 2013 were analyzed for 129I, 127I and their inorganic chemical species in the first time. The measured 129I/127I ratio is 1–3 orders of magnitude higher than the pre-nuclear level, indicating its dominantly anthropogenic sources. Relatively high 129I levels were observed in the Yangtze River and its estuary, as well as in the southern Yellow Sea, and 129I level in seawater declines towards the ECS shelf. In the open sea, 129I and 127I in surface water exists mainly as iodate, while in Yangtze River estuary and some locations, iodide is dominated. The results indicate that the Fukushima nuclear accident has no detectable effects in the ECS until August 2013. The obtained results are used for investigation of interaction of various water masses and water circulation in the ECS, as well as the marine environment in this region. Meanwhile this work provides essential data for evaluation of the possible influence of the increasing NPPs along the coast of the ECS in the future.

Spatial and vertical distribution of 129I and 127I in the East China Sea: Inventory, source and transportation

“…The temporal distribution pattern can be established by combining with the data from our previous study (Liu D. et al, 2016). These results are expected to promote our understanding of not only the movement of iodine isotopes in estuarine and continental shelf areas but also the long-term transport of other conservative radionuclides by oceanic current.…”

“…In our previous work (Liu D. et al, 2016), by observing the spatial distribution of iodine isotopes (i.e., 129 I and 127 I) concentration and species in the seawater of the ECS in August, we found that 129 I decreased from the coast to offshore and the species of 129 I and 127 I were dominated by iodate in the shelf water but existed mainly as iodide in the Changjiang Estuary. We also found that the influence of Fukushima nuclear accident in the 129 I level of the ECS was not detectable until August 2013.…”

“…Instead, 129 I is widely utilized as a tracer for the biogeochemical cycle of iodine, the movement and exchange of water masses, and the interactions between atmosphere and seawater in marine environments (Hou et al, 2007;Zhang and Hou, 2013;Xing et al, 2017). Due to its high solubility (Kd: 5-30 L kg -1 , Takata et al, 2013) and long residence time in the ocean (~300 kyrs) compared to the turnover time of ocean water (~1000 kyrs, Broecker and Peng, 1982), it can be utilized to trace the cycling of dissoluble organic carbon and phytoplankton blooming associated with reductive conditions (Schwehr et al, 2005;Hou and Hou, 2012;Liu D. et al, 2016).…”

Temporal variation in <sup>129</sup>I and <sup>127</sup>I in aerosols from Xi'an, China: influence of East Asian monsoon and heavy haze events

“…ozone depletion and new particle formation from condensable iodinecontaining vapours), drawing increasing attention in not only atmospheric science but also environmental fields in recent years (Saiz-Lopez et al, 2012). A number of studies on atmospheric iodine just focus on the processes and mechanisms in marine boundary layer since over 99.8 % of iodine is derived from ocean (McFiggans et al, 2000). Other sources of iodine in air are comprised of volatile iodine and resuspended particles from soil, as well as combustion of fossil fuel (Fuge and Johnson, 1986).…”

Water Circulation and Marine Environment in the Antarctic Traced by Speciation of 129I and 127I

“…However, some biological processes including bacteria, enzyme and plankton activity have been suggested to control the formation of iodide 14 . Therefore, the transformation of iodine species, and in particular the 129 I species, can reflect the change of marine primary production and marine environment 14 , 15 .…”