Forms and functions of inorganic carbon in the Jiaozhou Bay sediments

Inorganic carbon forms and their influencing factors, mutual transformation and contribution to carbon cycling in the Jiaozhou Bay sediments were discussed. The results show that inorganic carbon in sediments could be divided into five forms:NaCl form, NH₃·H₂O form, NaOH form, NH₂OH·HCl form and HCl form. Thereinto, NH₂OH·HCl form and HCl form account for more than 70% of total inorganic carbon. There was close relationship among every form of inorganic carbon and their correlativity was clearly different with different sedimentary environment except the similar strong positive correlation among NH₂OH·HCl form, HCl form and total inorganic carbon in all regions of the Jiaozhou Bay. All forms of inorganic carbon were influenced by organic carbon, pH, Eh, Es, nitrogen and phosphorus in sediments, but their influence had different characteristics in different regions. Every form of inorganic carbon transformed into each other continuously during early diagenesis of sediments and the common phenomenon was that NaCl form, NH₃·H₂O form, NaOH form and NH₂OH·HCl form might transform into steady HCl form. NaCl form, NH₃·H₂O form, NaOH form and NH₂OH·HCl form could participate in carbon recycle and they are potential carbon source; HCl form may be buried for a long time in sediments, and it may be one of the final resting places of atmospheric CO₂. Inorganic carbon which entered into sediments was about 4.98×10¹⁰ g in the Jiaozhou Bay every year, in which about 1.47×10¹⁰ g of inorganic carbon might be buried for a long time and about 3.51×10¹⁰ g of inorganic carbon might return into seawater and take part in carbon recycling.