在火山噴發(fā)過程中排放出的二氧化硫被氧化成硫酸鹽，并可進(jìn)而形成硫酸鹽氣溶膠,，后者能影響地球的輻射平衡。Bao等人利用對保存在巖石記錄中的大氣硫酸鹽進(jìn)行硫和三氧同位素測量,，來研究硫酸鹽形成的特定氧化通道,。生物谷啟用新域名www.bioon.net
他們發(fā)現(xiàn)，在新生代中期（距今3400萬至700萬年前）在北美洲高平原北部,，曾經(jīng)發(fā)生7次與噴發(fā)相關(guān)的硫酸鹽氣溶膠沉降事件,。
在這些沉積物中所發(fā)現(xiàn)的在同位素上不相關(guān)聯(lián)的硫酸鹽可能只是在堿性云水中產(chǎn)生的，這種云水有利于在對流層中形成一個由臭氧支配的二氧化硫氧化通道,。
這表明,，與今天的弱酸性條件不同的是，那個地區(qū)的云水在新生代中期經(jīng)常是堿性的,。 (生物谷Bioon.net)
生物谷推薦原文出處：
Nature doi:10.1038/nature09100
Massive volcanic SO2 oxidation and sulphate aerosol deposition in Cenozoic North America
Huiming Bao, Shaocai Yu & Daniel Q. Tong
Volcanic eruptions release a large amount of sulphur dioxide (SO2) into the atmosphere1, 2. SO2 is oxidized to sulphate and can subsequently form sulphate aerosol3, which can affect the Earth's radiation balance, biologic productivity and high-altitude ozone concentrations, as is evident from recent volcanic eruptions4. SO2 oxidation can occur via several different pathways that depend on its flux and the atmospheric conditions3. An investigation into how SO2 is oxidized to sulphate—the oxidation product preserved in the rock record—can therefore shed light on past volcanic eruptions and atmospheric conditions. Here we use sulphur and triple oxygen isotope measurements of atmospheric sulphate extracted from tuffaceous deposits to investigate the specific oxidation pathways from which the sulphate was formed. We find that seven eruption-related sulphate aerosol deposition events have occurred during the mid-Cenozoic era (34 to 7 million years ago) in the northern High Plains, North America. Two extensively sampled ash beds display a similar sulphate mixing pattern that has two distinct atmospheric secondary sulphates. A three-dimensional atmospheric sulphur chemistry and transport model study reveals that the observed, isotopically discrete sulphates in sediments can be produced only in initially alkaline cloudwater that favours an ozone-dominated SO2 oxidation pathway in the troposphere. Our finding suggests that, in contrast to the weakly acidic conditions today5, cloudwater in the northern High Plains may frequently have been alkaline during the mid-Cenozoic era. We propose that atmospheric secondary sulphate preserved in continental deposits represents an unexploited geological archive for atmospheric SO2 oxidation chemistry linked to volcanism and atmospheric conditions in the past.
