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Measurements of delta^<13>C of atmospheric CO_2 and its application to the carbon cycle

大气CO_2δ13C测量及其在碳循环中的应用

基本信息

批准号：
05452076
负责人：
NAKAZAWA Takakiyo
金额：
$ 2.5万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1994
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-05452076/
关键词：
Carbon dioxide Carbon isotopic ratio Global carbon cycle 同位体比

项目摘要

The concentration of atmospheric CO_2 has been increasing steadily for the last 200 years, due to human activities such as fossil fuel combustion and deforestation. In order to elucidate the causes of such an increase of the concentration quantitatively, it is necessary to figure out the carbon cycle on the earth's surface. However, the roles of the biosphere and the oceans in the carbon cycle are not yet well understoond. To solve this difficulty, measurements are requireed for the carbon isotopic ratio delta^<13>C of atmospheric CO_2 as well as for its concentration.In this study, CO_2 samples collected in the troposphere over Japan and in the western Pacific and the Antarctic regions were analyzed for delta^<13>C with a precision of better than 0.02*. The seasonal cycle of delta^<13>C was clearly found at northern latitudes and the equator, due to the seasonal change in the biospheric activities, but it was hardly observable in the southern hemisphere. It was found that values of delta^<13>C decreased seculary at a rate of about 0.03*, due mainly to fossil fuel combustion. Interannual variations in the long-term trend of delta^<13>C were also found in association with ENSO event and other factors, which were almost opposite in phase with those of the CO_2 concentration. The analyzes of delta^<13>C and the CO_2 concentration with a box diffusion model and a 2-D atmospheric transport model showed that an imbalance of the CO_2 exchange between the atmosphere and the biosphere could be responsible for such interannual variations and that the biosphere does not act as a strong net source for atmospheric CO_2.

过去200年来，由于化石燃料燃烧和森林砍伐等人类活动，大气中CO_2的浓度一直在稳步增加。为了定量地阐明这种浓度增加的原因，有必要弄清楚地球表面的碳循环。然而，生物圈和海洋在碳循环中的作用尚不清楚。为了解决这一难题，需要测量大气CO_2的碳同位素比δ^<13>C及其浓度。本研究对日本上空、西太平洋和南极地区对流层采集的CO_2样品进行了δ^<13>C分析，精度优于0.02*。由于生物圈活动的季节变化，在北纬和赤道明显地发现了δ 13 C的季节周期，但在南半球几乎观察不到。发现δ 13 C值以约0.03*的速率长期降低，这主要是由于化石燃料燃烧。 δ^ 13 C长期趋势的年际变化也与ENSO事件等因素相关，与CO_2浓度的变化几乎反相。利用箱扩散模型和二维大气传输模型对δ 13 C和CO_2浓度的分析表明，大气与生物圈之间CO_2交换的不平衡可能是造成这种年际变化的原因，并且生物圈并不是大气CO_2的强大净源。