火山活動的水銀造成生物大滅絕：科學家們說

2001年時一些科學家說生物大滅絕是由水星的軌跡擺動導致，現在新的說法是由地球上的水銀含量過高造成。奇怪的是，無論是水星抑或水銀，英文字詞都是一樣 - mercury，只是有大小楷之別。

水銀造成生物大滅絕：科學家們說
Mercury caused mass extinctions, say scientists
Posted Fri, 06 Jan 2012 15:56:39 GMT
Adrian Bishop
Translation by Autumnson Blog

Volcanic eruption via Shutterstock
通過 Shutterstock的火山噴發

Mass extinctions during catastrophic climate change were caused by huge mercury levels, Canadian scientists say. The Earth's greatest global loss of life, around 250 million years ago, wiped out almost all marine creatures and most land-dwellers.
在災難性氣候變化期間的生物大滅絕是由巨大的汞水平造成，加拿大的科學家說。地球上最大的全球性生命損失，約在二億五千萬年前，消滅了幾乎所有的海洋生物和大部分的陸地居民。
Now, researchers at the University of Calgary have published a paper in the Geology journal, which blames massive mercury levels from volcanic eruptions, 30 times greater than those seen today.
現在，在卡爾加里大學的研究人員在“地質學報”發表一篇論文，歸咎於來自火山爆發的大量汞含量，30倍大於今天所看到的。
Co-author, Dr. Steve Grasby, an adjunct professor at the University of Calgary and a research scientist at Natural Resources Canada, says, "No one had ever looked to see if mercury was a potential culprit.
在卡爾加里大學的兼職教授及在加拿大自然資源部的一名研究科學家、論文合著者史蒂夫Grasby博士說：“從來沒有人看看水銀是否一種有潛質的罪魁禍首。
"This was a time of the greatest volcanic activity in Earth's history and we know today that the largest source of mercury comes from volcanic eruptions.
“那是地球歷史上最大的火山活動的時間，和我們今天知道水銀的最大來源是火山噴發。
"We estimate that the mercury released then could have been up to 30 times greater than today's volcanic activity, making the event truly catastrophic."
“我們估計，那時釋放的汞可能已經達到30倍於今天火山活動的，使得事件真正的災難性。”

Caption: This graphic shows historical variations of Mercury (Hg) deposition before and after the Latest Permian Extinction event as recorded in a sedimentary section in the High Arctic, Canada. The vertical axis demonstrates the depth of the sedimentary section relative to the extinction boundary while the horizontal looks at the amount of mercury accumulation (concentration in the rock) as measured in milligram per kilogram; Credit: Hamed Sanei, Steve Grasby and Benoit Beauchamp. (Sanei et al., 2012, Geology).


This is the first study to blame mercury for the Permian extinctions, says co-author and University of Calgary Geology Professor, Dr. Benoit Beauchamp. "Geologists, including myself should be taking notes and taking another look at the other five big extinction events."

The loss of marine life occurred after the oceans were contaminated by the mercury, explains Dr Hamed Sanei, adjunct professor at the University of Calgary and research scientist at Natural Resources Canada.

"Typically, algae acts like a scavenger and buries the mercury in the sediment, mitigating the effect in the oceans. But in this case, the load was just so huge that it could not stop the damage."

The mercury deposit levels could have been comparable with modern-day levels recorded at highly polluted bodies of water near smelters. Dr. Benoit Beauchamp, says, "We are adding to the levels through industrial emissions. This is a warning for us here on Earth today." adds Beauchamp. He says Canada has led the way in cutting international emissions of mercury.

Caption: Dr. Hamed Sanei analyzes chemical records of the sedimentary rocks deposited during the Latest Permian Extinction event. Dr. Sanei is a research scientist with Natural Resources Canada and an adjunct professor at the University of Calgary; Credit: University of Calgary/Riley Brandt.

In the Permian period, the land was a single continent. It is commonly thought that the eruptions from the volcanoes released carbon dioxide and other deadly poisons after penetrating coal seams. The Calgary University team provided evidence for this in a paper previously published in the Nature Geoscience journal.

Even with the huge levels of mercury, some life on Earth was able to survive, says Dr Sanei. "The story is one of recovery as well. After the system was overloaded and most of life was destroyed, the oceans were still able to self clean and we were able to move on to the next phase of life."

http://www.earthtimes.org/pollution/mercury-caused-mass-extinctions-scientists/1744/

恐龍滅絕有新解 都是水星軌道擺動惹的禍
北京晚報 2001年7月24日

距今約6000萬到7000萬年前地球上發生過一件大事，那就是生物界“霸主”恐龍的突然消失。恐龍的滅絕是如此神秘，個中原因至今還眾說紛紜，尚無定論。有人說恐龍可能是得癌症死的，還有人說“兇手”可能是一場罕見的乾旱。目前科學界比較廣為接受的“外星撞擊說”認為，是一顆小行星撞擊地球導致了恐龍的滅絕。
美國科學家的研究最近又為恐龍的死因提供了一種新的可能，他們認為，恐龍之死是水星惹的禍。加利福利亞大學洛杉磯分校太空生物學中心的布魯斯·朗納加爾稱，他們的電腦模擬表明：6500萬年前，水星的軌道發生擺動，導致一顆小行星飛向地球，成為恐龍大滅絕的罪魁禍首。

朗納加爾和他的同事使用電腦模型對2．5億年前的太陽系進行了“還原”。他們特別著重於計算每個行星的近日點—運行軌道上最接近太陽的點。行星的近日點通常以數百萬年為週期圍繞著太陽運轉。由於星體間的作用力，這種週期會隨著時間的改變而發生輕微的改變。朗納加爾等的最新研究發現，近日點週期的這種改變，會對行星內部產生一種“敲擊效應”，並進而改變行星的軌道。他們的模型表明，6500萬年前，水星的軌道因此而發生擺動，並對太空中的一個小行星帶產生影響，增加了其中的小行星離開軌道的幾率。水星的擺動並不足以使大量小行星進入地球，但朗納加爾認為，它很有可能使單個的小行星走上與地球相撞之路。朗納加爾等人的解釋實際上仍可歸入“外星撞擊說”，不過是為毀滅恐龍的那場大撞擊找到了一個初始的“推動力”。儘管如此，還是有其他一些研究人員對把水星軌道擺動與恐龍滅絕之間聯繫起來持懷疑態度。

北愛爾蘭阿馬天文臺臺長馬克·貝利說，朗納加爾的理論是建立在一系列不太可能的事件的基礎上的。他認為水星不會對太陽系的東西產生影響，因為“它太小了”。貝利說，該研究小組的模型是非常棒的，但把它和恐龍聯繫在一起太勉強了。（郭可）

http://dinosaurs.pixnet.net/blog/post/24397177-010724-%e6%81%90%e9%be%8d%e6%bb%85%e7%b5%95%e6%9c%89%e6%96%b0%e8%a7%a3-%e9%83%bd%e6%98%af%e6%b0%b4%e6%98%9f%e8%bb%8c%e9%81%93%e6%93%ba%e5%8b%95%e6%83%b9%e7%9a%84

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