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PNAS:阳光刺激北极土壤释放温室气体

来源:EurekAlert! 2013-02-12 20:12

高纬度土壤储存着的碳至少是大气中的2倍,但是一项研究发现这种土壤中的碳可能被释放出来并且在接触阳光的时候转化成温室气体。Rose Cory及其同事分析了34个北极地点,其中一些地区目前正在经历着显著的永冻土融化。

当这种富含冰的土壤融化的时候,它会崩溃而且常常导致侵蚀和滑坡。这种稳定性的丧失会向地表水释放溶解的有机碳,在那里这些碳与微生物相互作用,而且能够转换成二氧化碳。这组作者确定了当接触到阳光的时候,新释放的碳比未接触阳光的碳转化成二氧化碳的可能性高40%,二氧化碳是与气候变化有关联的一种温室气体。这些发现意味着暴露在阳光下能放大土壤中冷冻储存的碳向大气中的二氧化碳气体进行转化的效应。

由于这些碳以冻结的状态已经储存了至少数千年,这组作者提出这种转化对全球变暖率的影响可能是意义重大的。这组作者说,气候变化影响着我们这个行星的演化;因此,理解这类新释放出来的碳的命运可能有助于预测未来的气候和环境结果。(生 物 谷Bioon.com)

Surface exposure to sunlight stimulates CO2 release from permafrost soil carbon in the Arctic

Rose M. Cory, Byron C. Crump, Jason A. Dobkowski, and George W. Kling

Recent climate change has increased arctic soil temperatures and thawed large areas of permafrost, allowing for microbial respiration of previously frozen C. Furthermore, soil destabilization from melting ice has caused an increase in thermokarst failures that expose buried C and release dissolved organic C (DOC) to surface waters. Once exposed, the fate of this C is unknown but will depend on its reactivity to sunlight and microbial attack, and the light available at the surface. In this study we manipulated water released from areas of thermokarst activity to show that newly exposed DOC is >40% more susceptible to microbial conversion to CO2 when exposed to UV light than when kept dark. When integrated over the water column of receiving rivers, this susceptibility translates to the light-stimulated bacterial activity being on average from 11% to 40% of the total areal activity in turbid versus DOC-colored rivers, respectively. The range of DOC lability to microbes seems to depend on prior light exposure, implying that sunlight may act as an amplification factor in the conversion of frozen C stores to C gases in the atmosphere.

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