在煤灰中發現放射性汙染物

原文網址：www.sciencedaily.com/releases/2015/09/150902111835.htm

Radioactive contaminants found in coal ash

在煤灰中發現放射性汙染物

Landfill, pond storage of coal ash is currently unregulated

然而目前尚未設立煤灰掩埋場和貯留池的相關規範

A new Duke University-led study has revealed the presence of radioactive contaminants in coal ash from all three major U.S. coal-producing basins.

杜克大學進行的新研究顯示來自美國三大產煤盆地的飛灰皆含有放射性汙染物。

The study found that levels of radioactivity in the ash were up to five times higher than in normal soil, and up to 10 times higher than in the parent coal itself because of the way combustion concentrates radioactivity.

研究顯示跟正常土壤相比，灰燼的輻射強度可強上5倍；且因為燃燒後放射性物質會濃縮，強度甚至可高達原本煤炭的10倍之多。

The finding raises concerns about the environmental and human health risks posed by coal ash, which is currently unregulated and is stored in coal-fired power plants' holding ponds and landfills nationwide.

此發現讓人們必須正視煤灰造成的環境污染與人體健康風險。目前煤灰儲存在美國各地燃煤發電廠的貯留池和掩埋場中，但並未制定相關規範。

"Until now, metals and contaminants such as selenium and arsenic have been the major known contaminants of concern in coal ash," said Avner Vengosh, professor of geochemistry and water quality at Duke's Nicholas School of the Environment. "This study raises the possibility we should also be looking for radioactive elements, such as radium isotopes and lead-210, and including them in our monitoring efforts."

「在已知煤灰含有的汙染物質中，目前為止是以金屬和硒、砷這類汙染物為主要監管對象。」杜克大學環境學院，專長為地球化學與水質相關的教授，Avner Vengosh說。「本研究提醒我們應該要去偵測放射性元素，像是鐳同位素和鉛-210可能造成的汙染，並將它們列入監管項目中。」

Rdium isotopes and lead-210 occur naturally in coal as chemical by-products of its uranium and thorium content. Vengosh's research team revealed that when the coal is burned, the radium isotopes become concentrated in the coal ash residues, and the lead-210 becomes chemically volatile and reattaches itself to tiny particles of fly ash. This causes additional enrichment of radioactivity in the fly ash.

作為煤炭本身含有的釷和鈾產生的化學副產物，鐳同位素與鉛-210原本就會在煤炭中出現。Vengosh領導的團隊顯示燃燒煤炭時，鐳同位素會集中在殘留的煤灰中；而鉛-210則會變得具有化學揮發性，並重新吸附在微小的飛灰顆粒上，造成飛灰中有額外的高濃度放射性物質。

"Radioactive radium and lead-210 ends up concentrated in these tiny particles of fly ash, which though individually small, collectively comprise the largest volume of coal ash waste going into holding ponds and landfills," said Nancy Lauer, a Ph.D. student in Vengosh's lab who was lead author of the study.

「放射性鐳和鉛-210最後會集中於這些微小的飛灰顆粒上。雖然單顆顆粒相當細小，但在棄置於貯留池和掩埋場的煤灰廢棄物中，這些顆粒集合起來後卻是體積最大的一部分。」本研究的第一作者Nancy Lauer說，她是Vengosh實驗室的博士生。

Vengosh, Lauer and their colleagues published their peer-reviewed paper Sept. 2 in the journal Environmental Science & Technology.

Vengosh、Lauer和他們的同僚將他們的論文發表在9月2日的同儕審定期刊《環境科學與技術》之中。

The study comes as the U.S. Environmental Protection Agency's first-ever regulations on coal ash disposal are set to go into effect in October.

促成本研究的原因為美國環境保護署將在十月開始實施首次針對煤灰處置的相關規範。

Currently, coal ash disposal sites are not monitored for radioactivity, Vengosh noted, "so we don't know how much of these contaminants are released to the environment, and how they might affect human health in areas where coal ash ponds and landfills are leaking. Our study opens the door for future evaluation of this potential risk."

Vengosh注意到目前煤灰處置場的放射性並未被監控，「因此我們無法得知這些汙染物中到底有多少已經排放到環境裡；以及在煤灰池和掩埋場有所滲漏的地區，它們可能會如何影響人體健康。我們的研究開創了對此潛在風險的評估。」

Smokestack scrubbers installed at U.S. power plants keep these contaminants from escaping into the air when the coal is burned, he stressed. But if the contaminated coal ash is spilled, or if effluents leak from ponds or landfills, it may pose a hazard.

他強調，美國的火力發電廠在燃燒煤炭時，都有配備煙囪刷洗器來避免這些汙染物排放至空氣。然而，若這些受汙染的煤灰從煤灰池或掩埋場滲出或溢出，就有可能造成危害。

"Because of the tiny size of the fly ash particles, they are much more likely to be suspended in air if they are disposed in a dry form. People breathing this air may face increased risks, particularly since tiny particles tend to be more enriched in radioactivity," Lauer said.

「若在乾燥狀態下處置這些飛灰，由於它們的顆粒十分細緻，使得它們很有可能會懸浮在空氣當中。人類若呼吸到含有這些微粒的空氣，受到的健康風險便會增加，尤其是這些微粒可能有較高的放射性。」Lauer說。

Vengosh said this study is the first systematic study to compare radioactivity in coal and coal ash from the Illinois, Appalachian and Powder River basins. The researchers collected multiple samples of coal and coal ash from all three coal-producing basins and then measured the radioactive elements in each sample.

Vengosh說這篇研究首度系統性地比較了伊利諾州、阿帕拉契州和保德河盆地的煤炭與煤灰中的放射性。研究人員分別從這三個產煤盆地中採集許多煤炭與煤灰的樣品，接著測量每個樣品中的放射性元素濃度。

Their tests showed that coal and coal ash from different basins exhibited different levels of radioactivity -- the Illinois basin had the most, followed by the Appalachian and then the Powder River, which is in Wyoming and Montana. The tests also showed that the ratio of radium to uranium in the parent coal was consistent with the ratio found in its residual coal ash.

測試結果顯示產自不同盆地中的煤炭和煤灰，會具有不同強度的放射性。三者中以伊利諾州最高，阿帕拉契州次之，最低則是位處懷俄明州和蒙大拿州的保德河盆地。測試結果也呈現出原本的煤炭以及殘餘煤灰中，鐳與鈾的比例會兩者相等。

"This means we can predict how much potential radioactivity will occur in coal ash by measuring the uranium content in the parent coal, which is easily discerned," Vengosh said. "This analysis can be applied to all coal ash worldwide, and is useful information for regulators, industries and scientists alike."

「這意味著藉由測量原本煤炭的鈾含量，我們可以預估煤灰的放射性可能會有多強，而煤炭的鈾含量是相當容易測量的。」Vengosh說。「此分析結果可以適用在全世界的煤灰，並且能提供相關產業的管理者、業界和科學家相當有用的資訊。」

Because the isotopic ratios of the coal and coal ash varied between basins but were consistent within each individual basin, researchers can also use them to determine the source of environmental contamination. "They allow us to not only distinguish between the three basins, but also to determine whether contaminants are coming from coal ash or some other naturally occurring source in the local environment," Lauer said.

雖然不同盆地中的煤炭和煤灰的同位素比例不同，但來自同一盆地的卻會一樣，因此研究人員可以利用同位素比例確認環境汙染的來源。「同位素比例不只能讓我們區分出煤灰來自三個盆地中的哪一個，也可以用來辨別汙染物究竟是來自煤灰或是當地自然產生的其他物質。」Lauer說。

引用自：Duke University. "Radioactive contaminants found in coal ash: Landfill, pond storage of coal ash is currently unregulated." ScienceDaily. ScienceDaily, 2 September 2015. 

證據顯示地球上首次生物大滅絕的元凶並非重大災害，而是生物本身

原文網址：www.sciencedaily.com/releases/2015/09/150902123456.htm

Evidence that Earth's first mass extinction was caused by critters not catastrophe

證據顯示地球上首次生物大滅絕的元凶並非重大災害，而是生物本身

A powerful analogy for what is happening today

對當今情況的強烈類比

In the popular mind, mass extinctions are associated with catastrophic events, like giant meteorite impacts and volcanic super-eruptions.

在大眾認知中，大滅絕事件通常會跟重大天災扯上關聯，像是巨型隕石撞擊，以及超級火山噴發。

But the world's first known mass extinction, which took place about 540 million years ago, now appears to have had a more subtle cause: evolution itself.

然而現在卻發現在約5億4000萬年前發生，世上已知的首次大滅絕事件成因相當微妙：即演化本身。

"People have been slow to recognize that biological organisms can also drive mass extinction," said Simon Darroch, assistant professor of earth and environmental sciences at Vanderbilt University. "But our comparative study of several communities of Ediacarans, the world's first multicellular organisms, strongly supports the hypothesis that it was the appearance of complex animals capable of altering their environments, which we define as 'ecosystem engineers,' that resulted in the Ediacaran's disappearance."

「人們過了相當久才認知到生物本身也能驅使生物大滅絕發生。」范德堡大學地球與環境科學系的助理教授，Simon Darroch說。「地球上第一種多細胞生物群稱作埃迪卡拉動物(Ediacaran)。我們研究並比較不同的埃迪卡拉動物群落，結果強烈支持牠們之所以消失，是因為複雜動物出現而導致的假說。由於這些複雜動物能夠改變牠們生存的環境，因此我們也稱呼牠們為「生態工程師」(ecosystem engineer)。」

The study is described in the paper "Biotic replacement and mass extinction of the Ediacara biota" published Sept. 2 in the journal Proceedings of the Royal Society B.

他們的研究記述在以《埃迪卡拉動物群的生物群演替與大滅絕》(Biotic replacement and mass extinction of the Ediacara biota)為題的論文中，刊登於9月2日的《皇家學會報告B系列》期刊。

"There is a powerful analogy between the Earth's first mass extinction and what is happening today," Darroch observed. "The end-Ediacaran extinction shows that the evolution of new behaviors can fundamentally change the entire planet, and we are the most powerful 'ecosystem engineers' ever known."

「眼下發生之事與地球首度發生的大滅絕事件彼此之間有許多相似之處。」Darroch觀察到。「消滅埃迪卡拉動物的大滅絕事件展現了生物演化出的新行為模式，能從基本層面改變整個星球，而我們是已知的生態工程師中最強而有力者。」

The earliest life on Earth consisted of microbes -- various types of single-celled microorganisms. They ruled the Earth for more than 3 billion years. Then some of these microorganisms discovered how to capture the energy in sunlight. The photosynthetic process that they developed had a toxic byproduct: oxygen. Oxygen was poisonous to most microbes that had evolved in an oxygen-free environment, making it the world's first pollutant.

地球上最早的生命由微生物組成，包括了各種單細胞微生物。在超過30億年的時光當中，地球由它們統治著。接著某些微生物發明出新方法來汲取陽光中蘊含的能量。它們發展出光合作用的同時卻產生了一種有毒副產物：氧氣。對在無氧環境下演化而成的大多數微生物來說，氧氣具有致命的毒性，因此氧氣導致了世上第一起汙染事件。

But for the microorganisms that developed methods for protecting themselves, oxygen served as a powerful new energy source. Among a number of other things, it gave them the added energy they needed to adopt multicellular forms. Thus, the Ediacarans arose about 600 million years ago during a warm period following a long interval of extensive glaciation.

然而，對那些研發出防禦機制保護自己的微生物來說，氧氣反倒成為了一種強力新型能源。除了一些其他的革新，氧氣能提供它們要實行多細胞生活所需的額外能量。因此，經過了歷時漫長而範圍廣大的冰河期後，埃迪卡拉動物於6億年前在接續而至的溫暖時期崛起。

"We don't know very much about the Ediacarans because they did not produce shells or skeletons. As a result, almost all we know about them comes from imprints of their shapes preserved in sand or ash," said Darroch.

「因為埃迪卡拉動物並不會形成甲殼或者骨骸，使得我們對牠們所知甚少。我們對牠們的相關知識，幾乎來自於牠們的身形拓印在砂粒或者火山灰之上的痕跡。」Darroch說。

What scientists do know is that, in their heyday, Ediacarans spread throughout the planet. They were a largely immobile form of marine life shaped like discs and tubes, fronds and quilted mattresses. The majority were extremely passive, remaining attached in one spot for their entire lives. Many fed by absorbing chemicals from the water through their outer membranes, rather than actively gathering nutrients.

科學家所知的是，在那段太平盛世，埃迪卡拉動物幾乎遍布整個地球。牠們大多是無法移動的海洋生物，外型狀似餐盤、水管、植物或者床墊。多數種類終其一生固著在某個地點之上，過著相當被動的生活。許多以吸收海水流過牠們的外膜時順道帶來的化學物質過活，而非主動去攝取營養。

Paleontologists have coined the term "Garden of Ediacara" to convey the peace and tranquility that must have prevailed during this period. But there was a lot of churning going on beneath that apparently serene surface.

古生物學家創造出「埃迪卡拉花園」這個詞彙，來傳達出當時瀰漫的和平寧靜氛圍。然而在這平靜的表象之下，實則暗潮洶湧。

After 60 million years, evolution gave birth to another major innovation: animals. All animals share the characteristics that they can move spontaneously and independently, at least during some point in their lives, and sustain themselves by eating other organisms or what they produce. Animals burst onto the scene in a frenzy of diversification that paleontologists have labeled the Cambrian explosion, a 25-million-year period when most of the modern animal families -- vertebrates, molluscs, arthropods, annelids, sponges and jellyfish -- came into being.

6000萬年之後，演化又產生了另一項重大革新：動物。所有動物都擁有相同特點：至少在生命史上的某個階段，牠們能夠自發且主動移動；並以攝食其他生物本體或製造物為生。在短短2500萬年的時光中，大多數現存的動物門，像是脊索動物、軟體動物、節肢動物、環節動物、海綿、水母先後出現在地球上。這起動物以各式各樣的姿態赫然出現於生命舞台上的事件，古生物學家稱為「寒武紀大爆發」。

"These new species were 'ecological engineers' who changed the environment in ways that made it more and more difficult for the Ediacarans to survive," said Darroch.

「這些新物種為「生態工程師」，牠們改變了環境而使得埃迪卡拉動物越來越難以生存。」Darroch說。

He and his colleagues performed an extensive paleoecological and geochemical analysis of the youngest known Ediacaran community exposed in hillside strata in southern Namibia. The site, called Farm Swartpunt, is dated at 545 million years ago, in the waning one to two million years of the Ediacaran reign.

他和他的同僚詳盡分析了已知最年輕的埃迪卡拉生物群所處地層的古生物及地球化學特徵。此地層出露位置為奈米比亞南部，稱作Swartpunt農場的山丘；年代約為5億4500萬年前，約是埃迪卡拉時代的最後一至兩百萬年。

"We found that the diversity of species at this site was much lower, and there was evidence of greater ecological stress, than at comparable sites that are 10 million to 15 million years older," Darroch reported. Rocks of this age also preserve an increasing diversity of burrows and tracks made by the earliest complex animals, presenting a plausible link between their evolution and extinction of the Ediacarans.

「相較於其他早了1000萬至1500年的場址，我們發現這個場址的埃迪卡拉物種多樣性低了許多，且證據顯示出牠們受到了十分強大的生態壓力。」Darroch發表道。保存在此年代岩石中，由最古老的複雜動物挖掘而成的軌跡和洞穴，種類也變得越來越豐富，顯現牠們的演化與埃迪卡拉動物的消失間有一定關聯。

The older sites were Mistaken Point in Newfoundland, dating from 579 to 565 million years ago; Nilpena in South Australia, dating from 555 to 550 million years ago; and the White Sea in Russia, dating also from 555 to 550 million years ago million years ago.

這些年代較老的場址包括了5億7900萬至5億6500萬年前，紐芬蘭的Mistaken Point；5億5500萬至5億5000萬年前，南澳的Nilpena，以及相同時代，位於俄羅斯的White Sea。

Darroch and his colleagues made extensive efforts to ensure that the differences they recorded were not due to some external factor.

Darroch和他的同僚盡力確保這些場址的化石差異並非來自於其他外在因素。

For example, they ruled out the possibility that the Swartpunt site might have been lacking in some vital nutrients by closely comparing the geochemistry of the sites.

舉例來說，他們仔細比較了各場址的地球化學性質，而排除了Swartpunt的物種多樣性低落，是因為缺少某些重要營養素的可能性。

It is a basic maxim in paleontology that the more effort that is made in investigating a given site, the greater the diversity of fossils that will be found there. So the researchers used statistical methods to compensate for the variation in the differences in the amount of effort that had been spent studying the different sites.

有一條古生物學名言是：在一個場址調查越久，就會發現越多種化石。因此研究人員利用統計方法，來彌補花費在不同場址的心力不同，而導致化石發現數量的差異。

Having ruled out any extraneous factors, Darroch and his collaborators concluded that "this study provides the first quantitative palaeoecological evidence to suggest that evolutionary innovation, ecosystem engineering and biological interactions may have ultimately caused the first mass extinction of complex life."

屏除了所有外在因素後，Darroch和他的同僚總結說：「本研究首度以定量化的古生態學方法，證實了演化革新、生態工程和生物之間的互動，可能最終導致了發生在複雜生命上的首度大滅絕。」

引用自：Vanderbilt University. "Evidence that Earth's first mass extinction was caused by critters not catastrophe: A powerful analogy for what is happening today." ScienceDaily. ScienceDaily, 2 September 2015. 

地球礦物，宇宙僅有

原文網址：www.sciencedaily.com/releases/2015/08/150826113615.htm

Earth's mineralogy unique in the cosmos

地球礦物，宇宙僅有

New research from a team led by Carnegie's Robert Hazen predicts that Earth has more than 1,500 undiscovered minerals and that the exact mineral diversity of our planet is unique and could not be duplicated anywhere in the cosmos.

由卡內基大學的Robert Hazen領軍的團隊發表的新研究，預測地球上還有1500種礦物尚待發現，且地球獨一無二的礦物多樣性在宇宙中可說絕無僅有。

Minerals form from novel combinations of elements. These combinations can be facilitated by both geological activity, including volcanoes, plate tectonics, and water-rock interactions, and biological activity, such as chemical reactions with oxygen and organic material.

化學元素以各種方式組合而形成了礦物。地質活動和生物活動都能夠幫助這些組合發生，前者包括了火山活動、板塊構造作用、水岩交互作用(water-rock interaction)；後者像是氧氣和有機物參與其中的化學反應。

Nearly a decade ago, Hazen developed the idea that the diversity explosion of planet's minerals from the dozen present at the birth of our Solar System to the nearly 5,000 types existing today arose primarily from the rise of life. More than two-thirds of known minerals can be linked directly or indirectly to biological activity, according to Hazen. Much of this is due to the rise of bacterial photosynthesis, which dramatically increased the atmospheric oxygen concentration about 2.4 billion years ago.

將近十年前Hazen發展出一套理論認為，地球的礦物種類能從太陽系剛形成時的寥寥無幾，暴增至現今將近有5000種的主因為生命出現在地球上。據Hazen說，三分之二的已知礦物或多或少都跟生物活動有直接或間接關連。其中大多數又因細菌發展出光合作用而生，此作用在24億年前大幅增加了大氣中的氧氣含量。

In a suite of four related, recently published papers, Hazen and his team--Ed Grew, Bob Downs, Joshua Golden, Grethe Hystad, and Alex Pires--took the mineral evolution concept one step further. They used both statistical models of ecosystem research and extensive analysis of mineralogical databases to explore questions of probability involving mineral distribution.

Hazen和他研究小組的組員，Ed Grew、Bob Downs、Joshua Golden、Grethe Hystad、Alex Pires最近發表了四篇彼此相關的論文，進一步發展礦物演化論的概念。他們利用了生態學研究用的統計模型，並大量分析礦物資料庫來探討礦物分布的概率。

They discovered that the probability that a mineral "species" (defined by its unique combination of chemical composition and crystal structure) exists at only one locality is about 22 percent, whereas the probability that it is found at 10 or fewer locations is about 65 percent. Most mineral species are quite rare, in fact, found in 5 or fewer localities.

他們發現在所有的礦物種類(定義上為擁有獨特的化學元素組成與結晶構造)中，僅分布在一個地點的礦物約為22%，分布在十個或以下地點的約為65%。事實上大多數的礦物都十分稀有，分布地點為五個或少於五個。

"Minerals follow the same kind of frequency of distribution as words in a book," Hazen explained. "For example, the most-used words in a book are extremely common such as 'and,' 'the,' and 'a.' Rare words define the diversity of a book's vocabulary. The same is true for minerals on Earth. Rare minerals define our planet's mineralogical diversity."

「礦物分佈的機率跟字彙在書中的分佈模式相去不遠。」Hazen解釋。「舉例來說，在一本書中會有些頻繁出現的單字，像是「and」、「then」、「a」。然而偶爾出現的單字才是決定一本書字彙豐富程度的關鍵。地球上的礦物也是如此，罕見礦物決定了我們星球的礦物豐富程度。」

Further statistical analysis of mineral distribution and diversity suggested thousands of plausible rare minerals either still await discovery or occurred at some point in Earth's history, only to be subsequently lost by burial, erosion, or subduction back into the mantle. The team predicted that 1,563 minerals exist on Earth today, but have yet to be discovered and described.

進一步統計分析礦物的分佈模式與多樣性，結果顯示可能還有數千種礦物等著我們去發現，或是它們曾存在於地球歷史中的某段時光，如今卻因為埋藏、侵蝕或隨著隱沒作用回到地函而消失。團隊預測當今在地球上還有1563種礦物未被人類發現及描述。

The distribution of these "missing" minerals is not uniform, however.

但這些消失的礦物並非均勻分佈在這個世界上。

Several circumstances influence the likelihood of a mineral having previously been discovered. This includes physical characteristics, such as color. White minerals are less likely to have been noticed, for example. Other factors include the quality of crystallization, solubility in water, and stability near the surface of the planet.

在已辨識出來的礦物中，有幾個要素會決定發現它們的可能性，這包括了幾項物理特徵。比方說顏色，白色的礦物相對而言不那麼引人注目。其它因素還包含了結晶的品質優劣、在水中的溶解度，還有接近地表時的穩定程度。

As such, Hazen and his colleagues predicted that nearly 35 percent of sodium minerals remain undiscovered, because more than half of them are white, poorly crystallized, or water soluble. By contrast, fewer than 20 percent of copper, magnesium, and copper minerals have not been discovered.

因為如此，Hazen與他的同僚預估有將近35%的含鈉礦物仍未被發現，它們的外觀多半為白色、結晶甚差，或者易溶於水。相較之下，含銅、鎂的礦物未被發現者則小於20%。

Further expanding the link between geological and biological evolution, Hazen's team applied the biological concepts of chance and necessity to mineral evolution. In biology, this idea means that natural selection occurs because of a random "chance" mutation in the genetic material of a living organism that becomes, if it confers reproductive advantage, a "necessary" adaptation.

Hazen的團隊將生物學中的偶然性和必然性概念應用在礦物演化上，而更加擴展了地質學與生物演化之間的關連。在生物學上，此概念意味著若生命體的基因物質中出現的「隨機」突變可以讓牠們更順利的繁衍後代，那麼這突變「必然」會成為生物體的適應(adaptation)，天擇因而發生。

But in this instance, Hazen's team asked how the diversity and distribution of Earth's minerals came into existence and the likelihood that it could be replicated elsewhere. What they found is that if we could turn back the clock and "re-play" Earth's history, it is probable that many of the minerals formed and discovered in this alternate version of our planet would be different from those we know today.

而在此情況下，Hazen的團隊提出了問題：地球礦物的分佈以及多樣性是如何形成？在其他地方有可能看到相同例子嗎？他們發現若我們將時間倒轉，並讓地球歷史重演，在這另一版本的地球上，我們很有可能會發現於此形成的礦物會與我們現今所認識的大相逕庭。

"This means that despite the physical, chemical, and biological factors that control most of our planet's mineral diversity, Earth's mineralogy is unique in the cosmos," Hazen said.

「這表示儘管物理、化學、生物法則控制了地球礦物的豐富程度，地球的礦物種類在宇宙中還是與眾不同的。」Hazen說。

The four papers are published in Canadian Mineralogist, Mathematical Geoscience, American Mineralogist, and Earth and Planetary Science Letters.

這四篇論文分別發表在《加拿大礦物學家》、《數學地球科學》、《美國礦物學家》、《地球與行星科學通訊》。

引用自：Carnegie Institution. "Earth's mineralogy unique in the cosmos." ScienceDaily. ScienceDaily, 26 August 2015.

4億1500萬年前的畸形浮游生物化石顯示了過去某些大滅絕事件的元凶，可能是重金屬污染

原文網址：www.sciencedaily.com/releases/2015/08/150825115031.htm

415-million-year-old malformed fossil plankton reveal that heavy metal pollution might have contributed to some of the world's largest extinction events

4億1500萬年前的畸形浮游生物化石顯示了過去某些大滅絕事件的元凶，可能是重金屬污染

Several Palaeozoic mass extinction events during the Ordovician and Silurian periods (ca. 485 to 420 to million years ago) shaped the evolution of life on our planet. Although some of these short-lived, periodic events were responsible for eradication of up to 85% of marine species, the exact kill-mechanism responsible for these crises remains poorly understood.

發生在奧陶紀以及志留紀之際的數次古生代大滅絕事件，塑造了地球生命的演化方向。這些短暫而週期性發生的事件，消滅了85%的海洋生命，然而我們仍然不甚了解它們危害生物的確切機制。

An international team led by Thijs Vandenbroucke (researcher at the French CNRS and invited professor at UGent) and Poul Emsbo (US Geological Survey) initiated a study to investigate a little known association between 'teratological' or 'malformed' fossil plankton assemblages coincident with the initial stages of these extinction events.

由Thijs Vandenbroucke(法國國家科學研究中心的研究員以及根特大學的訪問教授)和Poul Emsbo(美國地質調查所)領導的國際團隊進行的研究中，調查了畸形浮游生物化石群的組成，跟大滅絕事件的起始階段之間鮮為人知的關聯。

In a paper just published in Nature Communications, they present evidence that malformed fossil remains of marine plankton from the late Silurian (415 million years ago) contain highly elevated concentrations of heavy metals, such as iron, lead, and arsenic. These are well-known toxins that cause morphologic abnormalities in modern aquatic organisms; which led the authors to conclude that metal poisoning caused the malformation observed in these ancient organisms and may have contributed to their extinction and that of many other species.

在新發表於《自然通訊》(Nature Communications)的論文中，他們呈現的證據表達出晚志留纪的畸形海洋浮游生物化石，含有濃度相當高的重金屬，像是鐵、鉛、砷。這些惡名昭彰的毒素會讓現代的水生生物發育不正常，因此作者認為重金屬中毒扭曲了這些古海洋生物的外貌，甚至將牠們以及許多其他生物消滅殆盡。

Documented chemical behavior of these metals, which correlates with previously observed disturbances in oceanic carbon, oxygen and sulphur signatures, strongly suggests that these metal increases resulted from reductions of ocean oxygenation.

記錄到代表這些金屬元素的化學訊號的時間，與先前觀察中海洋碳、氧、硫突然變化的時間相當一致，強烈顯示這些金屬元素增加的原因是海洋從氧化狀態變成還原態。

Thus, metal toxicity, and its expressions in fossilized malformations, could provide the 'missing link' that relates organism extinctions to widespread ocean anoxia. As part of a series of complex systemic interactions accompanying oceanic geochemical variation, the mobilisation of metals in spreading anoxic waters may identify the early phase of the kill-mechanism that culminated in these catastrophic events.

因此，重金屬中毒還有它造成的畸形化石，可能就是生物滅絕與海洋大規模缺氧現象二者間的「失落環節」。隨著海洋的地球化學性質發生變化，不同系統之間會產生一連串複雜的連動，後果之一即為金屬元素到處充斥在缺氧的海水中。或許這就是滅絕事件在巔峰期剛開始時殺害大量生物的機制。

The recurring correlation between fossil malformations and Ordovician-Silurian extinction events raises the provocative prospect that toxic metal contamination may be a previously unrecognized contributing agent to many, if not all, extinction events in the ancient oceans.

奧陶紀-志留紀大滅絕事件與畸形化石之間反覆出現的關聯，讓這些科學家提出了較激進的想法：就算不是全部，但在許多古代海洋大滅絕事件中，毒性金屬污染也許是之前未被重視的重要因子。

引用自：Ghent University. "415-million-year-old malformed fossil plankton reveal that heavy metal pollution might have contributed to some of the world's largest extinction events." ScienceDaily. ScienceDaily, 25 August 2015. 

溫室氣體造成發生在上次冰河期的冰河後退現象

原文網址：www.sciencedaily.com/releases/2015/08/150821082727.htm

Greenhouse gases caused glacial retreat during last Ice Age

溫室氣體造成發生在上次冰河期的冰河後退現象

A recalculation of the dates at which boulders were uncovered by melting glaciers at the end of the last Ice Age has conclusively shown that the glacial retreat was due to rising levels of carbon dioxide and other greenhouse gases, as opposed to other types of forces.

重新計算上次冰河期末時因為冰河融化而露出來的礫石年代，確認了冰河後退的主因為二氧化碳以及其他溫室氣體的濃度上升，而非其他作用力。

Carbon dioxide levels are now significantly higher than they were at that time, as a result of the Industrial Revolution and other human activities since then. Because of that, the study confirms predictions of future glacial retreat, and that most of the world's glaciers may disappear in the next few centuries.

工業革命以及之後的其他人類活動，造成現今的二氧化碳濃度遠比上次冰河期末高上許多。這使得此篇研究也證實了未來冰河將會繼續後退，而世界上大多數的冰河也許在不久之後的數個世紀內就會融化殆盡。

The findings were published today in Nature Communications by researchers from Oregon State University, Boston College and other institutions. They erase some of the uncertainties about glacial melting that had been due to a misinterpretation of data from some of these boulders, which were exposed to the atmosphere more than 11,500 years ago.

此篇刊登在今日《自然通訊》(Nature Communications )的研究的作者來自於奧勒岡州立大學、波士頓學院以及其他機構。之前利用這些暴露在空氣中的時間已超過11,500年的礫石，來預估冰河融化的時間時，有可能會因為判讀錯誤而產生誤差。而這群科學家在這篇論文中成功降低了這些誤差。

"This shows that at the end of the last Ice Age, it was only the increase in carbon dioxide and other greenhouse gases that could have caused the loss of glaciers around the world at the same time," said Peter Clark, a professor in the OSU College of Earth, Ocean and Atmospheric Sciences, and co-author on the study.

「在上次冰河期末時，唯有二氧化碳以及其他溫室氣體的濃度上升，才能造成世界各地的冰河在同一時間開始融化。」本研究的共同作者，奧勒岡州立大學地球、海洋與大氣科學系的教授Peter Clark說。

"This study validates predictions that future glacial loss will occur due to the ongoing increase in greenhouse gas levels from human activities," Clark said. "We could lose 80-90 percent of the world's glaciers in the next several centuries if greenhouse gases continue to rise at the current rate."

「此研究證實了未來冰河將會因為人類活動造成的溫室氣體濃度持續上升而消失。」Clark說。「若溫室氣體的濃度繼續以現在的速率攀升，在未來的數世紀內我們可能就會失去世界上百分之80至90的冰河。」

Glacial loss in the future will contribute to rising sea levels and, in some cases, have impacts on local water supplies.

冰河的消失在未來將會造成全球海平面上升，而在某些地區當地的水源供應可能也會受到相當大的影響。

As the last Ice Age ended during a period of about 7,000 years, starting around 19,000 years ago, the levels of carbon dioxide in the atmosphere increased from 180 parts per million to 280 parts per million. But just in the past 150 years, they have surged from 280 to about 400 parts per million, far higher than what was required to put an end to the last Ice Age.

從19,000年前起，上次冰河期末的7,000年間，大氣中二氧化碳的濃度從百萬分之180(180 p.p.m.)升高至280 p.p.m.。但僅僅在過去的150年間，二氧化碳已從280 p.p.m.飆升至400 p.p.m.，遠比終結上次冰河期所需的濃度還要高上許多。

The new findings, Clark said, were based on a recalculation of the ages at which more than 1,100 glacial boulders from 159 glacial moraines around the world were exposed to the atmosphere after being buried for thousands of years under ice.

Clark說這項新發現建立於重新測量159層世界各地冰磧(glacial moraine)中的1100顆冰河礫石的年代。這些冰磧曾被深埋在冰層底下數千年，直到冰河融化後才重見天日。

The exposure of the boulders to cosmic rays produced cosmogenic nuclides, which had been previously measured and used to date the event. But advances have been made in how to calibrate ages based on that data. Based on the new calculations, the rise in carbon dioxide levels -- determined from ancient ice cores -matches up nicely with the time at which glacial retreat took place.

冰河融化後露出的礫石會暴露在宇宙射線的照射之下，而產生宇生核種(cosmogenic nuclide)，在先前的研究中可以測量其濃度來定年事件發生的年代。本研究改良之處在於如何以測量到的數據來換算成更精確的年代。根據他們新的計算方式而得出的冰河後退年代，與顯示在古老冰芯中的二氧化碳濃度上升時刻，兩者之間相當符合。

"There had been a long-standing mystery about why these boulders were uncovered at the time they were, because it didn't properly match the increase in greenhouse gases," said Jeremy Shakun, a professor at Boston College and lead author on the study. "We found that the previous ages assigned to this event were inaccurate. The data now show that as soon as the greenhouse gas levels began to rise, the glaciers began to melt and retreat."

「長久以來的疑惑在於為何這些礫石會在這個時間點開始暴露在地表，因為這與溫室氣體開始升高的時刻並不太符合。」本研究的第一作者，波士頓學院的Jeremy Shakun教授說。「我們發現之前對這起事件的年代的推估並不準確。現在的數據顯示溫室氣體的濃度一開始上升，冰河便會開始融化並後退。」

There are other forces that can also cause glacial melting on a local or regional scale, the researchers noted, such as changes in the Earth's orbit around the sun, or shifts in ocean heat distribution. These factors probably did have localized effects. But the scientists determined that only the change in greenhouse gas levels could have explained the broader global retreat of glaciers all at the same time.

研究人員注意到尚有其他因素會造成局部或區域性的冰河融化，像是地球繞日軌道的變化，或者海洋熱能分佈的改變。這些因素或多或少會造成區域性效應，然而科學家斷定唯有溫室氣體濃度的改變，才能在同一時間造成範圍廣至全球的冰河後退。

In the study of climate change, glaciers have always been of considerable interest, because their long-term behavior is a more reliable barometer that helps sort out the ups-and-downs caused by year-to-year weather variability, including short-term shifts in temperature and precipitation.

在氣候變遷的研究當中，冰河總是佔有一席之地，這是由於它們的長期變化並不會被年際氣候變化影響，包括溫度以及降雨的短週期變化，使得它們可以做為較可靠的長時間尺度氣壓計。

Other collaborators on this research were from the University of Wisconsin, Purdue University, and the National Center for Atmospheric Research. The work was supported by the National Oceanic and Atmospheric Administration and the National Science Foundation.

其他的協同研究人員來自威斯康辛大學、普渡大學以及美國國家大氣研究中心。本研究由美國國家海洋和大氣管理局及美國國家科學基金會所資助。

引用自：Oregon State University. "Greenhouse gases caused glacial retreat during last Ice Age." ScienceDaily. ScienceDaily, 21 August 2015.