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.