Abstract
A total of 43 seafloor surface sediment samples collected from the offshore region surrounding the Leizhou Peninsula were analyzed in terms of the total organic carbon content (TOC), total nitrogen (TN), organic carbon isotope (δ13Corg) and sediment grain size. Our results showed that the organic carbon content in the samples ranged from 0.12 to 0.79%, with an average of 0.42% which was lower compared with other offshore regions of China, whereas the δ13Corg was in the range of −22.47‰ to −19.18‰. The total nitrogen content ranged from 0.011 to 0.100% which was also low. The combination of δ13Corg and TOC/TN ratio (5.1–14.3) suggested that the organic matter is dominant by marine authigenic source input, as marine sourced organic matter accounts for 71%, 82%, and 75% in the sediments from the offshore areas of the east side, west side and the south (Qiongzhou Strait) of the Leizhou Peninsula, respectively. The weak/poor correlations between the organic carbon and clay, silt content, the pH and Eh value suggested that organic matter abundance and distribution were influenced by the source input of organic matter, the seafloor sediments’ redox status, and seawater’s hydrodynamic condition.
Highlights
The ocean is the most important carbon pool on the earth’s surface and a vital system of the global carbon cycle (Gao et al, 2008; Larowe et al, 2020; Yu et al, 2021)
It shows that the offshore area of the Liusha Bay is the high total organic carbon content (TOC) content area, and the northwest part of the Beibu Gulf in the west of the Leizhou Peninsula and southeast offshore areas in the east of the Leizhou Peninsula are two low TOC content areas
The TOC contents in the samples of the Leizhou Peninsula offshore fall within the range of that from the vast far offshore region of the Beibu Gulf which is 0.02∼0.95% (Cui et al, 2017)
Summary
The ocean is the most important carbon pool on the earth’s surface and a vital system of the global carbon cycle (Gao et al, 2008; Larowe et al, 2020; Yu et al, 2021). Guangzhou Marine Geological Survey had conducted a comprehensive research project of “Holocene Environmental Evolution and Anthropogenic impact of the Beibu Gulf, South China” since 2009 In this project, two joint expeditions with the Leibniz Institute for Baltic Sea Research of Germany were carried out in 2009 and 2011, respectively. After establishing a long-term topography evolution model for the Beibu Gulf and inverting paleotopographic changes since 6,000 BP, the sedimentary environment evolution history of Beibu Gulf was investigated (Cui et al, 2017) The outcome of this project and other previous studies had provided some new information on the organic carbon contents, some specific molecular compounds and heavy metal pollutants (Zhang et al, 2011; Zhang et al, 2012; Chen et al, 2014; Cui et al, 2015; Jin et al, 2019; Liu and Chao, 2019). The expedition and sampling area of this project-were mainly in the far offshore and relatively deep-water areas, and there is a lack of investigation on sedimentary organic matter in the near coastal region surrounding the Leizhou Peninsula
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
