State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, CAS, Guiyang 550081, Guizhou, China; University of Chinese Academy of Sciences, Beijing 100049, China.
State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, CAS, Guiyang 550081, Guizhou, China; CAS Center for Excellence in Quaternary Science and Global Change, 710061 Xi'an, China.
Sci Total Environ. 2020 Jun 10;720:137539. doi: 10.1016/j.scitotenv.2020.137539. Epub 2020 Feb 26.
Recent studies show that the carbon sink attributable to the weathering of carbonate rocks may have been greatly underestimated if the biological carbon pump (BCP) effect in transferring dissolved inorganic carbon (DIC) to organic carbon (autochthonous OC) by aquatic photoautotrophs is neglected. The uptake of DIC by aquatic photoautotrophs may reach 0.2 to 0.7 Pg C/a globally, indicating that the carbon sink by the coupled carbonate weathering with aquatic photosynthesis mechanism (CCW) may be an important control in climate change. In order to understand the sensitivity of the CCW carbon sink to changes of climate and land-use, a systematic study of modern trap and 100-year-long core sediments was conducted in Fuxian Lake, (Yunnan, SW China), the second-deepest plateau oligotrophic freshwater lake in China. It was found that (1) the autochthonous OC in the lake sediments was characterized by lower C/N ratios and higher δC. By means of an n-alkanes compound calculation, the proportions of autochthonous OC were determined to be in the range, 60-68% of all OC; (2) increase in the autochthonous OC accumulation rate (OCAR) was accompanied by an increase in the inorganic carbon accumulation rate (ICAR) in both the trap and core sediments. In particular, the post-1950 OCAR was estimated to be about 6.9 times that for the period, 1910-1950; (3) OCAR in core sediments increased significantly with global warming and land-use change, from 1.06 g C m yr in 1910 to 21.74 g C m yr in 2017. The increasing carbon sink may act as a negative feedback on global warming if the trend holds for all lakes globally. This study is the first to quantify the burial flux of organic carbon generated by the BCP effect in lakes and may contribute to solving the problem of the missing carbon sink in the global carbon cycle.
最近的研究表明，如果忽视水生光自养生物将溶解无机碳（DIC）转移到有机碳（自生 OC）的生物碳泵（BCP）效应，那么归因于碳酸盐风化的碳汇可能被大大低估。水生光自养生物对 DIC 的吸收可能达到全球 0.2 到 0.7 Pg C/a，这表明通过碳酸盐风化与水生光合作用机制耦合的碳汇（CCW）可能是气候变化的一个重要控制因素。为了了解 CCW 碳汇对气候变化和土地利用变化的敏感性，在中国西南云南省抚仙湖进行了现代捕集器和 100 年长岩芯沉积物的系统研究。结果发现：（1）湖泊沉积物中的自生 OC 具有较低的 C/N 比值和较高的δC。通过 n-烷烃化合物计算，确定自生 OC 的比例在所有 OC 的 60-68%范围内；（2）在捕集器和岩芯沉积物中，自生 OC 积累率（OCAR）的增加伴随着无机碳积累率（ICAR）的增加。特别是，1950 年后的 OCAR 估计是 1910-1950 年期间的 6.9 倍；（3）与全球变暖及土地利用变化相比，岩芯沉积物中的 OCAR 显著增加，从 1910 年的 1.06 g C m yr 增加到 2017 年的 21.74 g C m yr。如果这一趋势在全球所有湖泊中持续下去，增加的碳汇可能会对全球变暖产生负反馈。本研究首次量化了湖泊中 BCP 效应产生的有机碳埋藏通量，可能有助于解决全球碳循环中缺失碳汇的问题。
