达里诺尔湖沉积物中无机碳的形态组成

Abstract

Sediments play an important role in carbon cycle as the important sources and sinks of carbon.The role of sediments in the carbon cycle is closely related to the forms and distribution of inorganic carbon in the sediments.The forms of inorganic carbon have different capacity in the carbon cycle and recycle.Forms and changes of inorganic carbon in the sediments were essential for the fluxes and processes of carbon across the water-sediment interface.The study of inorganic carbon forms is the basis and premise for discussing their contribution to carbon cycling.In this wok,the sequential extraction method was employed to extract inorganic carbon forms in sediments from Dali Lake.The form distribution characters of inorganic carbon in surface sediments and sediment cores were studied.The correlations between inorganic carbon and physical-chemistry characteristics such as total organic carbon(TOC),total nitrogen(TN),total phosphorus(TP) and biogenic silicate(BSi) were discussed in sediment cores.The results showed that the dominant form of inorganic carbon was NH2OH·HCl form both in surface sediment and sediment cores;The content of NH2OH·HCl form in sediments ranges from 6.26 to 17.51 mg/g,with mean content of 14.02 mg/g,accounted for 82.77% of the total inorganic carbon in the sediments.The contents of inorganic carbon forms in surface sediment are rank as: NH2OH·HCl form HCl form NaCl form NH3·H2O form NaOH form.In terms of the horizontal characteristics,the central area was the high value area of inorganic carbon form,the east and north area were the low value area in the lake.Water depth and inorganic carbon present a good positive correlation(R2=0.86,P0.01).The correlationship and the horizontal characteristics of inorganic carbon implied that the terrigenous material which were carried by inflowing rivers have dilute effect on sediments.The supersaturation coefficients of Calcium carbonate in different year in Dali Lake are far greater than 1(31.59IAP/Ksp166.92).The calculation results showed that calcium carbonate was supersaturation in the lake and implied that the aquatic environmental conditions were beneficial to authigenic carbonate precipitation in Dali Lake.In sediment cores,the content of NH2OH·HCl form ranges from 5.29 to 21.72 mg/g,with mean content of 12.90 mg/g,accounted for 82.21% of the total inorganic carbon in the sediments.The contents of NH2OH·HCl form in sediment cores of DLNE-3 and DLNE-5 are obviously higher than DLNE-8 and DLNE-10.The former lied in deep water area are weakly affected by the dilution effect of terrigenous input,which is beneficial to authigenic carbonate precipitation.The latter lied in shallow water area are strongly affected by the dilution effect of terrigenous input,which is not helpful for authigenic carbonate precipitation.The correlations between inorganic carbon and nitrogen,phosphorus,biogenic silicate in the sediments implied that nutrients rising can promote the formation of calcium carbonate supersaturation.In addition,the physical and chemical properties changes in aquatic environment caused by photosynthesis was one of the important factors leading to precipitation of carbonate.