Communications - Earth and Environment, a new journal of nature magazine, published Zhang Xi's latest research on the black carbon of the abyss online. Courtesy of Shanghai Ocean University
On February 16, the reporter learned from Shanghai Ocean University on the 16th that under the guidance of Xu Yunping, a researcher at the School of Marine Sciences of Shanghai Ocean University, Zhang Xi, a doctoral student at the university, revealed the secret of the abyssal sedimentary black carbon, and reported the source, distribution and buried flux of the abyssal sedimentary black carbon for the first time in the world.
The latest research, "The hadal zone is an important and heterogeneoussink of black carbon in the ocean," was published online in Communications Earth & Environment, a new journal of Nature.
This is also another important research progress made by the research group in the field of abyss science after the report on mercury pollution in the trenches in 2021 in the proceedings of the National Academy of Sciences of the United States (PNAS), an internationally renowned academic journal.
Black carbon (blackcarbon) is the product of incomplete combustion of biomass and fossil fuels, which directly affects global climate change, carbon cycle, environmental health hazards and many other issues, and is a hot spot in the research fields of climate and environment at home and abroad. Although the ocean has long been considered an important black carbon sink, there have been few studies of deep-sea black carbon, and black carbon from abyssal sediments has never been reported.
Zhang Xi is doing experiments. Courtesy of Shanghai Ocean University
Using trench voyages organized by the School's Abyss Center and shared voyages by international collaborators, the research team obtained sediment samples from six trenches: Atacama, Kemadek, New Britain, Bougainville, Marceau and Mariana. The research group analyzed the black carbon and total organic carbon content and their stable and radiocarbon isotopes (δ13C and Δ14C), and obtained three important findings:
First, the black carbon deposited in the trenches is a contribution from terrestrial vegetation and fossil fuels rather than from the ocean, and the discovery basically solves the debate in recent years about whether the black carbon in the ocean is a land source or an autologous source of the ocean.
Second, the contribution of biomass and fossil fuels to trench black carbon is related to the distance of trenches to land, the distribution of vegetation in nearby countries, and the level of socio-economic activity. In the New Britain Trench and Bougainville Trench, close to the less developed country of Papua New Guinea, vegetation burning contributes more than 50 per cent on average, while in the Kemadek Trench, close to developed countries Australia and New Zealand, and in the nearby Atacama Trench, where there is significant mining activity, fossil fuel combustion can contribute more than 80 per cent.
Third, based on the estimation of six trenches, the annual buried amount of black carbon in the global abyss is 1.0±0.5×106 tons, which is twice the amount of deep-sea black carbon buried by previous estimates. This means that early neglect of the abyss is likely to have significantly underestimated the potential of the deep sea for black carbon sinks.
It is reported that Zhang Xi is the co-first author of the paper, and researcher Xu Yunping and Dr. Xiao Wenjie (now a postdoctoral fellow of Southern University of Science and Technology) are the co-first and corresponding authors of the paper. Professor Fang Jiasong, Associate Researcher Luo Min, Dr. Fang Yin, and collaborators from Ocean University of China, Qingdao National Laboratory for Marine Science and Technology, Southern University of Science and Technology, Southern University of Technology, University of Southern Denmark, Japan Marine Science and Technology Center, New Zealand Institute of Water and Atmosphere Research participated in the work. The research was funded by the National Natural Science Foundation of China, the State Key Laboratory of Estuarine Coastal Science of East China Normal University, the Danish National Research Foundation, and the Shanghai Sheshan National Field Science Observation Station Open Fund. The Shanghai Municipal Science and Technology Commission, the EU Research Fund and the New Zealand National Institute of Water and Atmosphere provided funding support for the voyage.
Previously, the Proceedings of the National Academy of Sciences (PNAS) published online the latest research results of Xu Yunping's team and their collaborators on mercury burial in the abyss trench, "The massive accumulation of mercury in the deepest parts of the ocean and its significance for the environmental mercury cycle." The study found that although the area of the abyss trench accounts for only about 1% of the global ocean, it has buried a large amount of mercury since the second industrial revolution, playing an important role in the entire ocean and even the global mercury cycle. The analysis found that the buried flux of mercury per unit area of the trench is tens or even hundreds of times higher than the global deep-sea average; mercury on the surface of the ocean (mainly caused by anthropogenic activities) can quickly settle and be preserved in the sediment of the abyss trench; and the mercury content in sediment has shown a rapid increase trend since the second industrial revolution, indicating that mercury pollution released by human activities has reached the deepest seas in the world. (End)