高緯度土壤儲存著的碳至少是大氣中的2倍,，但是一項研究發(fā)現(xiàn)這種土壤中的碳可能被釋放出來并且在接觸陽光的時候轉化成溫室氣體,。Rose Cory及其同事分析了34個北極地點，其中一些地區(qū)目前正在經(jīng)歷著顯著的永凍土融化,。
當這種富含冰的土壤融化的時候,，它會崩潰而且常常導致侵蝕和滑坡。這種穩(wěn)定性的喪失會向地表水釋放溶解的有機碳,，在那里這些碳與微生物相互作用,，而且能夠轉換成二氧化碳。這組作者確定了當接觸到陽光的時候,，新釋放的碳比未接觸陽光的碳轉化成二氧化碳的可能性高40%,，二氧化碳是與氣候變化有關聯(lián)的一種溫室氣體。這些發(fā)現(xiàn)意味著暴露在陽光下能放大土壤中冷凍儲存的碳向大氣中的二氧化碳氣體進行轉化的效應,。
由于這些碳以凍結的狀態(tài)已經(jīng)儲存了至少數(shù)千年,，這組作者提出這種轉化對全球變暖率的影響可能是意義重大的。這組作者說,，氣候變化影響著我們這個行星的演化,；因此，理解這類新釋放出來的碳的命運可能有助于預測未來的氣候和環(huán)境結果,。(生 物 谷Bioon.com)
doi: 10.1073/pnas.1214104110
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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.
