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冰川冻土 ›› 2001, Vol. 23 ›› Issue (1): 22-27.

• 研究论文 • 上一篇    下一篇

利用多年冻土区湖相沉积物中埋藏植物稳定碳同位素组成重建大气CO2浓度

林清, 王绍令, 赵林   

  1. 中国科学院寒区旱区环境与工程研究所冻土工程国家重点实验室, 甘肃兰州730000
  • 收稿日期:2000-03-28 修回日期:2000-05-15 出版日期:2001-02-25 发布日期:2012-04-26
  • 基金资助:
    国家自然科学基金项目(49572117;49425304);中国科学院重大基金项目(Kj-b-3)资助

The Records of Atmospheric CO2 Derived from the Stable Carbon Isotopic Composition of Buried Plant Tissues in Perennial Frozen Lacustrine Sediments

LIN Qing, WANG Shao-ling, ZHAO Lin   

  1. State Key Laboratory of Frozen Soil Engineering, CAREERI, CAS, Lanzhou Gansu 730000, China
  • Received:2000-03-28 Revised:2000-05-15 Online:2001-02-25 Published:2012-04-26

摘要: 沉水植物碳同位素分馏同水中溶解无机碳浓度有一定的关系,因而可以通过青藏高原多年冻土区的湖相沉积物中埋藏沉水植物——龙须眼子菜(Potamogeton pectiniatus)植物屑的碳同位素组成重建该地大气CO2浓度的变化情形.研究结果表明,该地在9.17~6.77kaBP间,大气CO2浓度是整个研究时间段中最低的,其后在6.77~4.56kaBP时期大气CO2浓度增加,在4.56~2.17kaBP之间,大气CO2浓度是整个研究时间内CO2浓度最高的阶段.植物屑的碳同位素组成反映了溶解无机碳浓度的变化,从而可用以重建大气CO2浓度的变化情况.

关键词: 多年冻土, 湖相沉积, 沉水植物δ13C, 古大气CO2

Abstract: The stable carbon isotopic fractionation in submerged plant is dependent upon the concentration of dissolved inorganic carbon (DIC) which equilibrates with atmosphere CO2 by water gas exchange and indirectly provides an approach to rebuild the past atmospheric CO2 concentration. The Ngoring Lake is the largest outflow fresh water lake in the source region of the Yellow River and has well developed aquatic vegetation of submersed plants. Due to low air temperature (-4.5 ℃ in average), the lacustrine sediments are perennial frozen below the depth of 1.05 m, at which the temperature is-0.5 ℃. The plant tissues in the sediments are well preserved and can be separated. In this study, the well preserved plant tissues were separated from2 m thick perennial frozen lacustrine sediments which consist of fine silty clays. These tissues were apparently formed under relatively uniform water condition and mainly came from the same species of submerged plant——Potamogeton pectinatus by identification. The stable carbon isotope composition (δ13C) is calculated from stable carbon isotope ratio measured from a carbon dioxide by FINNIGAN MAT-251 mass spectrometer. The carbon dioxide is produced by combustion of an aliquot of plant tissues with a little pre cleaned cupric oxide and platinum filament in an evacuated fine quartz tube at 800℃ for 2 h. The study shows that the relationship between δ13C of Potamogeton pectinatus and the concentration of dissolved CO2 [CO2e] can be described as Equation (5). The concentration of dissolved CO2 [CO2e] is calculated as [CO2e] = a×p CO2, where p CO2 is atmospheric CO2 concentration and a is the solubility parameter which can be induced by the absolute temperature of water from ln a=(58.0931+90.5069×(100/T) + 22.294× ln(T/100).δCO2e can be calculated using the equilibrium isotope fractionation and mixing model among the inorganic carbon species as a function of temperature, carbon isotope composition and ratio of different sources. The water temperature calculation is consulted with the water temperature-time curve of the Lake Qinghai. The atmospheric CO2 fluctuations reconstructed from stable carbon isotopic composition of the samples show that the atmospheric CO2 concentration had an increasing tendency from 9.16 to 2.17 ka BP, and in the same time three main stages of low, middle and high atmospheric CO2 concentration are distinguished, which corresponded respectively to the time of 9.16~6.77 ka BP, 6.77~4.56 ka BP and 4.56~2.17 ka BP.

Key words: perennial frozen lacustrine sediment, submerged plant tissues, stable carbon isotopic composition, atmospheric CO2

中图分类号: 

  • P642.14