Application o f 210 Pb, Carbon and Nitrogen Isotope in Tracing of Changes and Burial Effect of Endogenous and Terrigenous Organic Matter in the Bering Sea over the Past 100 Years

摘要

By using the multi-tube sediment samples collected from NB01 station in the Bering Sea during the period of the fourth Chinese Arctic research expedition in 2010, as well as the dating technique of radioisotope 210Pb in sedimentary strata, based on the exponential decay trend of 210Pbex with the column sample depth, relative stable modern sedimentary environment in the investigation area was reflected. The results show that the deposition rate of modern marine sediment S was 0.27 cm /a, and correlation coefficient R was0.96 (n = 17 ) , while time span was 107 a (1903一2010). Meanwhile, carbon, nitrogen and isotopes were used to trace the sources of materials in the Bering Sea. It is found that the content of organic carbon and nitrogen in the column samples from NB01 station in the Bering Sea was 1.18% -1.80 % and 0 .16% -0.28% respectively, and C/N ratio ranged from 5.13 to 8.31. Total organic carbon (TOC) and total organic nitrogen (TON) were preserved well in sedimentary strata and had good consistency, showing that sources of organic matter were consistent. Moreover, their changes positively correlated with 210Pb. Organic carbon isotope (813C) ranged from - 2 2 . 45%。 to -21.82%。, and its changing trend was similar to that of C/N ratio； organic nitrogen isotope (61SN) varied from 7.53%。 to 8 .54%。, indicating that organic matter was mainly from remaining marine organisms after being decomposed, into which a certain quantity of terrigenous materials were mixed. In the 100 years, the overall trend of terrigenous materials became increasingly obvious, showing that the input and burial of organic carbon from seas and land in the Bering Sea were changing. According to the burial rate of surface sediment and content of organic carbon, the apparent burial flux of sedimentary organic carbon in the column sample from NB01 station in the Bering Sea was estimated, about 1 450 mmol C /( m2 - a ) . It is suggested that the high burial flux of sedimentary organic carbon in the regions was mainly related to the high primary productivity of the water body, the high output efficiency of organic carbon in the photic zone, favorable preservation and metabolic mechanism of organic matter, and high deposition rate.