Krypton Isotope Hydrology

氪同位素水文学

• 批准号: 0409756
• 负责人: Neil Sturchio
• 金额: $ 19.74万
• 依托单位: University of Illinois at Chicago
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-07-01 至 2007-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0409756&HistoricalAwards=false
• 关键词: Krypton; Isotope; Hydrology

0409756SturchioThe age of groundwater is one of the most elusive geologic parameters to quantify, despite itscrucial significance for water resources, waste management, subsurface reactive transport, andpaleoclimate studies. It has long been recognized that 81 Kr is a nearly ideal tracer fordetermining residence times of old groundwater in the 5 10 4 10 6 year range, yet because of itslow abundance ( 81 Kr/Kr 10 -12 ) it has been nearly impossible to measure. However, a newtechnique for measurement of 81 Kr/Kr ratios in small quantities of Kr (as little as 50 micromoles)was recently reported (Atom-Trap Trace Analysis, or ATTA; Chen et al., 1999; Du et al., 2003),and its application to old groundwater was demonstrated successfully by the PI and colleagues intheir NSF-funded study of the Nubian Aquifer, Egypt (Sturchio et al., 2003). That studyestablished the feasibility of using the ATTA technique for routine 81 Kr/Kr measurement inhydrologic investigations of systems having long groundwater residence times. The ATTAtechnique, which can also be used for measuring 85 Kr/Kr, is thus an ideal tool with which toaddress a range of fundamental questions in hydrology.This proposal requests support for a graduate student to work with the PI and colleagues(Z. T. Lu's group at Argonne National Laboratory) in developing further applications of the traceKr isotopes ( 81 Kr and 85 Kr) in hydrologic investigations. The intellectal merit of this research isthat it will lead to an enhanced understanding of the water cycle within the Earth's crust.Specific investigations that we propose are: (1) to determine the residence time of salinegroundwaters in the central U.S.A., which on the basis of stable isotope data are believed to havetraveled more than 1,000 km from a recharge area in the Rocky Mountains (Musgrove andBanner, 1993), and which should therefore have a residence time on the order of 10 6 years; (2) toconstrain the residence time of hydrothermal waters at Yellowstone National Park, for whichlittle information is available (Pearson and Truesdell, 1978); (3) to determine the residence timeof groundwater in the Milk River aquifer of southern Alberta, which was the subject of an earliermulti-tracer study sponsored by the IAEA that was focused on dating very old groundwater(Ivanovich, Frohlich, and Hendry, 1991); and to investigate residence times of young (50 yr)groundwaters where other tracers such as tritium-helium and CFC's do not provide coherentresults. These investigations are representative of the broad range of potential applications oftrace Kr isotopes in groundwater hydrology.The broader impact of the proposed research is that it will provide opportunities forresearch, training, and education at the University of Illinois at Chicago (UIC), which has thenation's fifth most diverse student population; it will establish enhanced local Chicago-areapartnership for routine application of trace Kr isotopes in hydrology, because the Kr separationswill henceforth be performed in a laboratory at UIC (rather than in Switzerland as in the previousNSF-funded study) with ATTA measurements performed nearby at Argonne NationalLaboratory; it will help establish the new subdiscipline of Kr isotope hydrology, which may havesignificant impact on hydrologic investigations and water resources management worldwide.

地下水年龄是最难以量化的地质参数之一，尽管它对水资源、废物管理、地下反应运移和古气候研究具有重要意义。长期以来，人们一直认为81Kr是测定5×10~4×10~(-6)年范围内古老地下水停留时间的近乎理想的示踪剂，但由于其丰度较低(81Kr/Kr 10~(-12))，几乎不可能测量到。然而，最近报道了一种在少量Kr(仅50微摩尔)中测量81Kr/Kr比值的新技术(Atom-Trap痕量分析，或ATTA；Chen等人，1999；Du等人，2003)，PI和他的同事在他们由NSF资助的埃及努比亚含水层研究中成功地展示了它对旧地下水的应用(Sturchio等人，2003)。这项研究确定了在地下水停留时间较长的系统的水文调查中使用ATTA技术进行常规81Kr/Kr测量的可行性。ATTA技术也可用于测量85Kr/Kr，因此是解决水文学中一系列基本问题的理想工具。这项建议要求支持一名研究生与PI和同事(Argonne国家实验室的Z.T.Lu小组)合作，开发示踪Kr同位素(81Kr和85Kr)在水文调查中的进一步应用。这项研究的学术价值在于它将导致对地球地壳内水循环的更深入的了解。我们建议的具体调查是：(1)确定美国中部咸水周围水域的停留时间，根据稳定的同位素数据，这些海水被认为已经从落基山脉补给区(Musgrove and Banner，1993)穿过1000多公里，因此应该有大约106年的停留时间；(2)限制黄石国家公园热水的停留时间，这方面的信息很少(Pearson和Truesdell，1978)；(3)确定阿尔伯塔省南部Milk River含水层地下水的停留时间，这是原子能机构早些时候赞助的一项多示踪剂研究的主题，该研究的重点是测定非常古老的地下水的年代(Ivanovich、Frohlich和Hendry，1991年)；并调查年轻(50年)地下水的停留时间，在这些地下水中，氚-氦和氟氯化碳等其他示踪剂无法提供一致的结果。这些研究代表了痕量Kr同位素在地下水水文学中的广泛潜在应用。拟议研究的更广泛影响是，它将为伊利诺伊大学芝加哥分校(UIC)的研究、培训和教育提供机会，该大学拥有全国第五大多样化的学生人口；它将加强芝加哥当地在水文学中常规应用痕量Kr同位素的合作关系，因为从今以后Kr的分离将在UIC的实验室进行(而不是之前NSF资助的研究中在瑞士进行的)，Atta测量在附近的Argonne国家实验室进行；它将有助于建立Kr同位素水文学这一新的分支学科，这可能对全世界的水文调查和水资源管理产生重大影响。