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美国宾州溪流沉积物中放射性令人担忧

已有 945 次阅读 2018-1-26 23:37 |个人分类:新观察|系统分类:海外观察| 放射性, 油气废水, 溪流沉积物

美国宾州溪流沉积物中放射性令人担忧

诸平

据美国杜克大学(Duke University2018119日提供的消息,在美国宾夕法尼亚州的河流沉积物中持续存在来自油气废水的放射性Radioactivityfrom oil and gas wastewater persists in Pennsylvania stream sediments)。下面的图片是在美国宾夕法尼亚州西部某地,处理过的石油和天然气废水流入了一条小溪。杜克大学的一项新研究发现,像这样的处理地点的溪流沉积物,其放射性水平比未受影响的上游地区高出650倍。其安全性实在令人担忧。

Treated oil and gas wastewater flows into a stream in western Pennsylvania. A new Duke study finds stream sediments at disposal sites such as this one have levels of radioactivity that are 650 times higher than at unaffected upstream sites. Credit: Avner Vengosh, Duke University
就在美国宾夕法尼亚州的有关部门要求将含放射性镭(Ra)的压裂废水未经处理,直接排放到地表水系禁令颁布之后7年多时间里,杜克大学的一项研究发现,在3个处理地点的沉积物中,高水平的放射性物质仍然存在。这种污染来自于常规的即非水力压裂的油气废水的处理,根据目前美国的国家规定,这些污水仍然可以被处理后再排放到当地的河流中。

杜克大学环境学院(Duke's Nicholas School of theEnvironment)的地球化学与水质教授Avner Vengosh说:“不仅是压裂液会造成一定的风险;来自传统或者非压裂的油气井中产生的水也含有高浓度的Ra,它本身就是一种放射性元素。这种废水导致了河流沉积物中Ra的积累,这些放射性物质随着时间的推移而会逐渐衰变,并转化为其他放射性元素。”

在处置地点的溪流沉积物中发现的放射性水平比上游沉积物的放射性水平高出大约650倍。在某些情况下,它甚至超过了仅在美国联邦指定的放射性废物处理地点的放射性水平。杜克大学尼古拉斯环境学院的一名博士生,也是这项研究的领导者Nancy Lauer说:“我们的分析证实,这种放射性物质的积累源于2011年之后,也就是非传统的油气废水处理遭受当局限制之后。”

Nancy Lauer她解释说:“我们在沉积物中测量的放射性核素比率,以及受影响沉积物中放射性元素的衰变速率和生长速度,使我们基本上可以在2011年以后的时间段中对污染物进行年代测定。”其研究成果于201814日在《环境科学与技术》(Environmental Science and Technology)杂志上发表——Nancy E. Lauer, Nathaniel R. Warner, Avner Vengosh. Sources of Radium Accumulation in Stream Sediments near Disposal Sites in Pennsylvania: Implications for Disposal of Conventional Oil and Gas Wastewater. Environmental Science and Technology, 2018. DOI: 10.1021/acs.est.7b04952.

参与此项研究的除了美国杜克大学的研究人员之外,还有美国宾夕法尼亚州立大学( Pennsylvania State University)更多信息请注意浏览原文或者相关报道。

Abstract

Abstract Image

In Pennsylvania, Appalachian oil and gas wastewaters (OGW) are permitted for release to surface waters after some treatment by centralized waste treatment (CWT) facilities. While this practice was largely discontinued in 2011 for unconventional Marcellus OGW at facilities permitted to release high salinity effluents, it continues for conventional OGW. This study aimed to evaluate the environmental implications of the policy allowing the disposal of conventional OGW. We collected stream sediments from three disposal sites receiving treated OGW between 2014 and 2017 and measured 228Ra, 226Ra, and their decay products, 228Th and 210Pb, respectively. We consistently found elevated activities of 228Ra and 226Ra in stream sediments in the vicinity of the outfall (total Ra = 90–25,000 Bq/kg) compared to upstream sediments (20–80 Bq/kg). In 2015 and 2017, 228Th/228Ra activity ratios in sediments from two disposal sites were relatively low (0.2–0.7), indicating that a portion of the Ra has accumulated in the sediments in recent (<3) years, when no unconventional Marcellus OGW was reportedly discharged. 228Ra/226Ra activity ratios were also higher than what would be expected solely from disposal of low 228Ra/226Ra Marcellus OGW. Based on these variations, we concluded that recent disposal of treated conventional OGW is the source of high Ra in stream sediments at CWT facility disposal sites. Consequently, policies pertaining to the disposal of only unconventional fluids are not adequate in preventing radioactive contamination in sediments at disposal sites, and the permission to release treated Ra-rich conventional OGW through CWT facilities should be reconsidered.




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