Sources and temporal-spatial variations of sedimentary organic matter and black carbon in Zhanjiang Bay: Insights into coastal carbon burial

Yuanhao Zeng; Qibin Lao; Chunqing Chen; Hui Zeng; Fajin Chen

doi:10.1016/j.marenvres.2025.107711

Sources and temporal-spatial variations of sedimentary organic matter and black carbon in Zhanjiang Bay: Insights into coastal carbon burial

Mar Environ Res. 2026 Jan:213:107711. doi: 10.1016/j.marenvres.2025.107711. Epub 2025 Nov 13.

Authors

Yuanhao Zeng¹, Qibin Lao², Chunqing Chen¹, Hui Zeng¹, Fajin Chen³

Affiliations

¹ College of Ocean and Meteorology, Guangdong Ocean University, Zhanjiang, 524088, China; School of Chemistry and Environment, Guangdong Ocean University, Zhanjiang, 524088, China.
² College of Ocean and Meteorology, Guangdong Ocean University, Zhanjiang, 524088, China; School of Chemistry and Environment, Guangdong Ocean University, Zhanjiang, 524088, China; Key Laboratory for Coastal Ocean Variation and Disaster Prediction, Guangdong Ocean University, Zhanjiang, 524088, China; Key Laboratory of Climate, Resources and Environment in Continental Shelf Sea and Deep Sea of Department of Education of Guangdong Province, Guangdong Ocean University, Zhanjiang, 524088, China.
³ College of Ocean and Meteorology, Guangdong Ocean University, Zhanjiang, 524088, China; School of Chemistry and Environment, Guangdong Ocean University, Zhanjiang, 524088, China; Key Laboratory for Coastal Ocean Variation and Disaster Prediction, Guangdong Ocean University, Zhanjiang, 524088, China; Key Laboratory of Climate, Resources and Environment in Continental Shelf Sea and Deep Sea of Department of Education of Guangdong Province, Guangdong Ocean University, Zhanjiang, 524088, China. Electronic address: fjchen@gdou.edu.cn.

PMID: 41252898
DOI: 10.1016/j.marenvres.2025.107711

Abstract

Black carbon (BC) is a key oceanic carbon sink, particularly in coastal bays, owing to its persistent and refractory properties. However, understanding of the sources and temporal-spatial variations of sedimentary BC in coastal bays remains limited. Analysis of spatiotemporal variations in BC, total organic carbon (TOC), total nitrogen (TN), and their isotopic compositions (δ¹³C_TOC, δ¹⁵N, δ¹³C_BC), as well as C/N and BC/TOC ratios, in surface sediments of Zhanjiang Bay (ZJB) over four seasons were conducted to elucidate the seasonal dynamics of organic carbon in the bay. Our results showed that terrestrial organic matter was found to contribute 55 %-62 % of TOC in sediments across all four seasons. Fossil fuel combustion was the primary source of BC in the upper bay, while biomass burning dominated in the lower bay. Significantly higher TOC and BC concentrations in the upper bay than in the lower bay are driven by two primary factors. Firstly, the finer sediment grain size (the average content of silt and clay in the four seasons: 85.9 % ± 18.2 %) due to aquaculture activities in the upper bay promotes the preservation of TOC and BC. Secondly, a frontal system between the upper and lower bay traps organic matter derived from the terrestrial input and local anthropogenic activities, thereby enhancing the adsorption capacity of upper bay sediments. These factors have important implications for global carbon cycling and sequestration, and further highlight the considerable impact of oyster farming and weak hydrodynamic conditions on the burial of coastal sedimentary organic matter.

Keywords: Black carbon; Carbon and nitrogen stable isotopes; Sedimentary organic matter; Sources; Temporal-spatial variations.

MeSH terms

Bays
Carbon* / analysis
China
Geologic Sediments* / chemistry
Nitrogen / analysis
Soot / analysis

Substances

Soot
Carbon
Nitrogen