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首页> 外文期刊>Nature >SPECTROSCOPIC EVIDENCE AGAINST NITRIC ACID TRIHYDRATE IN POLAR STRATOSPHERIC CLOUDS
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SPECTROSCOPIC EVIDENCE AGAINST NITRIC ACID TRIHYDRATE IN POLAR STRATOSPHERIC CLOUDS

机译：极性球面云团中硝酸三水合物的光谱证据

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HETEROGENEOUS reactions on polar stratospheric clouds (PSCs) play a key role in the photochemical mechanism thought to be responsible for ozone depletion in the Antarctic and the Arctic(1,2). Reactions on PSC particles activate chlorine to forms that are capable of photochemical ozone destruction, and sequester nitrogen oxides (NOx) that would otherwise deactivate the chlorine(3,4). Although the heterogeneous chemistry is now well established, the composition of the clouds themselves is uncertain. It is commonly thought that they are composed of nitric acid trihydrate(3), although observations have left this question unresolved(5-14). Here we reanalyse infrared spectra of type I PSCs obtained in Antarctica in September 1987(15,16), using recently measured optical constants of the various compounds that might be present in PSCs17. We find that these PSCs were not composed of nitric acid trihydrate but instead had a more complex composition, perhaps that of a ternary solution. Because cloud formation is sensitive to their composition, this finding will alter our understanding of the locations and conditions in which PSCs form. In addition, the extent of ozone loss depends on the ability of the PSCs to remove NOx permanently through sedimentation. The sedimentation rates depend on PSC particle size which in turn is controlled by the composition and formation mechanism(14). [References: 30]
机译：极地平流层云（PSCs）上的异质反应在光化学机理中起着关键作用，认为这是造成南极和北极臭氧消耗的原因（1,2）。 PSC颗粒上的反应将氯活化成能够破坏光化学臭氧的形式，并螯合氮氧化物（NOx）否则会使氯失活（3,4）。尽管现在已经很好地建立了异质化学，但是云本身的组成还不确定。人们普遍认为它们是由硝酸三水合物组成的（3），尽管观察结果尚未解决这个问题（5-14）。在这里，我们使用最近测得的PSCs17中可能存在的各种化合物的光学常数，重新分析1987年9月在南极洲获得的I型PSCs的红外光谱。我们发现这些PSC并非由三水合硝酸组成，而是具有更复杂的组成，也许是三元溶液。因为云的形成对其组成很敏感，所以这一发现将改变我们对PSC形成的位置和条件的理解。另外，臭氧损失的程度取决于PSC通过沉降永久去除NOx的能力。沉降速率取决于PSC的粒径，而PSC的粒径又受组成和形成机理的控制（14）。 [参考：30]

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