Anthropocene 129I Record in the Yellow Sea Sediments and Its Indication for River-Delivered Radioactive Pollution to Marginal Seas

Abstract

As the number of coastal nuclear facilities rapidly increases and the wastewater from the Fukushima Nuclear Plant has been discharged into the Pacific Ocean, the nuclear environmental safety of China’s marginal seas is gaining increased attention along with the heightened potential risk of nuclear accidents. However, insufficient work limits our understanding of the impact of human nuclear activities on the Yellow Sea (YS) and the assessment of their environmental process. This study first reports the ¹²⁹I and ¹²⁷I records of posthuman nuclear activities in the two YS sediments. Source identification of anthropogenic ¹²⁹I reveals that, in addition to the gaseous ¹²⁹I release and re-emission of oceanic ¹²⁹I discharged from the European Nuclear Fuel Reprocessing Plants (NFRPs), the Chinese nuclear weapons testing fallout along with the global fallout is an additional ¹²⁹I input for the continental shelf of the YS. The ¹²⁹I/¹²⁷I atomic ratios in the North YS (NYS) sediment are significantly higher than those in the other adjacent coastal areas, attributed to the significant riverine input of particulate ¹²⁹I by the Yellow River. Furthermore, we found a remarkable ¹²⁹I latitudinal disparity in the sediments than those in the seawaters in the various China seas, revealing that sediments in China’s marginal seas already received a huge anthropogenic ¹²⁹I from terrigenous sources via rivers and thus became a significant sink of anthropogenic ¹²⁹I. This study broadens an insight into the potential impacts of terrigenous anthropogenic pollution on the Chinese coastal marine radioactive ecosystem.