全新世长江河口铁结合沉积有机碳的埋藏及其影响因素的研究

Deciphering the source, burial flux, and stability mechanism of organic carbon in diverse environments is of great significance for understanding the global carbon cycle. Estuary, which connects land and ocean, is a key area in global carbon cycle. Previous studies have found that reactive iron (FeR) plays an important role in the preservation of sedimentary organic carbon. Although a number of studies have been done on the carbon cycle in the Changjiang (Yangtze) River estuary and its adjacent East China Sea, it is still unclear how FeR affects the burial of sedimentary organic carbon on the geological time scale. Based on a 40 m-long sediment core (HSD22) collected in Hengsha Island (near the river mouth), we examined the total organic carbon (TOC) and δ¹³C of the sediments. Combined with the FeR data, the burial changes of FeR-OC in the Holocene were analyzed in tidal flat facies, estuary-shallow sea facies, and delta facies. Results show that the contents of FeR-OC were 0.04%±0.02%, 0.08%±0.04%, and 0.09%±0.06%, accounting for 6.73%, 12.73% and 12.06% of TOC, respectively. Therefore, an average of 11.72%±6.03% of the TOC in the estuary was preserved by iron binding, indicating that FeR minerals exert an important effect on the protection of organic carbon in the estuarine wetland and are an important“carbon sink”. The application of the carbon isotope endmember mixing model revealed that FeR-OC was mainly of terrigenous organic carbon, with varying weight contributions of marine and terrigenous organic carbon among different sedimentary facies. This study showed that FeR minerals in estuarine wetlands are affected by organic carbon sources and burial conditions during organic carbon conservation.