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首页> 外文学位 >Evaluating shallow groundwater age tracers: bromide, CFCs, tritium/helium-3, sulfur hexafluoride and HCFCs/HFCs.
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Evaluating shallow groundwater age tracers: bromide, CFCs, tritium/helium-3, sulfur hexafluoride and HCFCs/HFCs.

机译：评价浅层地下水年龄的示踪剂：溴化物，氟氯化碳、, /氦3，六氟化硫和六氯氟烃/六氟化碳。

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摘要

The use of chlorofluorocarbons (CFCs), tritium/helium-3 (3H/ 3He), and/or sulfur hexafluoride (SF6) to determine groundwater age was examined at three field sites in Ontario (Strathroy, Woodstock, and Sturgeon Falls). Also, a new set of potential tracers (HCFCs and HFCs) was evaluated because of the current difficulty in obtaining accurate CFC ages for waters recharged after 1990.; Strathroy, the primary site for this study, has an unconfined fine-sand aquifer with a predominately horizontal flow regime, which was evaluated to a depth of 15 m using a very detailed monitoring network of 67 small-screened piezometers. The aquifer is oxic but becomes NO3 reducing at a depth of ∼6 m, Mn reducing at ∼6.7 m, and then Fe reducing at ∼7.5 m. Based on the geochemistry and isotope data, it appears that pyrite oxidation is the primary source of electrons for the denitrification and Mn/Fe-reduction at depths below 6 m. CFCs, 3H/3He, and SF 6 have been evaluated at Strathroy in relation to the different redox environments.; The depth position of groundwater recharged during the past five years was known with certainty due to a concurrent bromide tracer study (Ryan et al., 1999). 3H/3He ages closely match the bromide derived ages in the shallow zone, and range from 0 at the water table to 27 years at the 12 to 15 m zone. CFC ages get older with depth as expected; however, all CFC ages, which were derived using three different sampling procedures (copper tube, glass ampoule, and glass bottle) and were analyzed at three different laboratories, indicate ages in the NO3 and Mn/Fe reducing zones that were up to 30 years older compared to the 3H/ 3He ages. In this zone the CFCs decline rapidly, suggesting degradation. Apparent first order degradation rates of 0.31, 0.66, and 1.18 yr-1 were derived for CFC-12, CFC-11, and CFC-113, respectively. Complete degradation of all three CFCs was observed in the Fe/Mn reducing zone. Concentrations of CFC-12, CFC-11, CFC-113 and SF6 were elevated in the vadose zone compared to expected North American air concentrations. Corrections of 1.1, 4.8, 4.2, and 46.3% were applied to CFC-12, CFC-11, CFC-113, and SF 6 ages, respectively, based on measured vadose zone excesses. These corrected SF6 data yielded ages that were a good match (within 2 years) to the 3H/3He derived ages to a depth of 7 m, but below this SF6 was apparently affected by degassing during sampling. (Abstract shortened by UMI.)
机译：在安大略省的三个田间地点（Strathroy，Woodstock和Sturgeon Falls）检查了使用氯氟烃（CFC），tri /氦3（3H / 3He）和/或六氟化硫（SF6）确定地下水年龄的方法。另外，由于目前难以为1990年以后的补给水获得准确的CFC年龄，因此对一组新的潜在示踪剂（HCFC和HFC）进行了评估。 Strathroy是这项研究的主要地点，拥有无约束的细砂含水层，主要为水平流态，使用67个小屏测压计的非常详细的监测网络对深水进行了评估，其深度为15 m。含水层是有氧的，但在约6m的深度处变为NO3还原，Mn在约6.7m处还原，然后Fe在约7.5m处还原。根据地球化学和同位素数据，似乎黄铁矿氧化是深度小于6 m的反硝化和Mn / Fe还原电子的主要来源。 Strathroy已针对不同的氧化还原环境对CFC，3H / 3He和SF 6进行了评估。由于同时进行的溴化物示踪剂研究，可以肯定地知道过去五年来补给的地下水的深层位置（Ryan等，1999）。 3H / 3He年龄与浅层地区的溴化物年龄密切相关，从地下水位的0到12至15 m区域的27岁。氟氯化碳的年龄随着预期的深入而变老；但是，使用三种不同的采样程序（铜管，玻璃安瓿和玻璃瓶）得出的所有CFC年龄，并在三个不同的实验室进行了分析，结果表明，NO3和Mn / Fe还原区的年龄可达30年。比3H / 3He年龄大。在这个区域中，CFC迅速下降，表明已经降解。 CFC-12，CFC-11和CFC-113的表观一级降解率分别为0.31、0.66和1.18 yr-1。在Fe / Mn还原区中观察到了所有三种CFC的完全降解。与北美的预期空气浓度相比，渗流区内的CFC-12，CFC-11，CFC-113和SF6浓度升高。根据测得的渗流带过量，分别对CFC-12，CFC-11，CFC-113和SF 6年龄进行了1.1、4.8、4.2和46.3％的校正。这些校正后的SF6数据产生的年龄与3H / 3He衍生年龄相匹配（在2年内），深度为7 m，但低于此SF6显然受到采样期间脱气的影响。 （摘要由UMI缩短。）

著录项

  • 作者

    Sebol, Lesley Allison.;

  • 作者单位

    University of Waterloo (Canada).;

  • 授予单位 University of Waterloo (Canada).;
  • 学科 Engineering Environmental.; Environmental Sciences.
  • 学位 Ph.D.
  • 年度 2005
  • 页码 190 p.
  • 总页数 190
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 环境污染及其防治;环境科学基础理论;
  • 关键词

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