科研之友
微信
新浪微博
Facebook
分享链接
摘要
Sources, abundance, isotopic compositions, and export fluxes of dissolved inorganic carbon (DIC), dissolved and colloidal organic carbon (DOC and COC), and particulate organic carbon (POC), and their response to hydrologic regimes were examined through monthly sampling from the Lower Mississippi River during 2006-2008. DIC was themost abundant carbon species, followed by POC and DOC. Concentration and delta C-13 of DIC decreased with increasing river discharge, while those of DOC remained fairly stable. COC comprised 61 +/- 3% of the bulk DOC with similar delta C-13 abundances but higher percentages of hydrophobic organic acids than DOC, suggesting its aromatic and diagenetically younger status. POC showed peak concentrations during medium flooding events and at the rising limb of large flooding events. While delta C-13-POC increased, delta N-15 of particulate nitrogen decreased with increasing discharge. Overall, the differences in delta C-13 between DOC or DIC and POC show an inverse correlation with river discharge. The higher input of soil organic matter and respired CO2 during wet seasons was likely the main driver for the convergence of delta C-13 between DIC and DOC or POC, whereas enhanced in situ primary production and respiration during dry seasons might be responsible for their isotopic divergence. Carbon export fluxes from the Mississippi River were estimated to be 13.6 Tg C yr(-1) for DIC, 1.88 Tg C yr(-1) for DOC, and 2.30 Tg C yr(-1) for POC during 2006-2008. The discharge-normalized DIC yield decreased during wet seasons, while those of POC and DOC increased and remained constant, respectively, implying variable responses in carbon export to the increasing discharge.
- 出版日期2015-11
- 单位近海海洋环境科学国家重点实验室; 海南省环境科学研究院; 厦门大学
