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首页> 外文学位 >Measurement of sulfur hexafluoride and CFCs in the environment: Application to groundwater dating, soil air dynamics and atmospheric mixing .
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Measurement of sulfur hexafluoride and CFCs in the environment: Application to groundwater dating, soil air dynamics and atmospheric mixing .

机译：环境中六氟化硫和CFC的测量：在地下水测年，土壤空气动力学和大气混合中的应用。

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This thesis investigates the application of SF6 and CFCs for dating of recent groundwater, and as tracers of soil air dynamics and atmospheric mixing. To identify processes, which control SF6 and CFCs in soil air, mixing ratios were observed over several years at Sparkill, NY (near NYC) and compared to atmospheric levels. SF6 in soil air was also measured near six large cities. To observe temporal trends as well as sources and transport of these gases, a long atmospheric time series of SF6 and CFCs collected at LDEO was analyzed. Lastly, SF6 and CFCs were applied to date groundwater at urban-influenced sites in southern NJ.; Soil air SF6 mixing ratios were controlled by diffusive transport and corresponded to atmospheric levels averaged over several months. In contrast, CFC mixing ratios were lows in winter and high in summer not explained by diffusion alone and attributed primarily to changing air/water partitioning of the gases with temperature. For shallow water tables or seasonal recharge, this can significantly effect tracer ages, and hinders observation of atmospheric mixing ratios from soil gas profiles. Within large cities and through much of the northeastern U.S. strong emissions result in atmospheric SF6 20% or more elevated above remote atmosphere levels hindering application of SF6 for groundwater dating near urban areas.; The atmospheric time series collected at LDEO indicates that from 1996 to 2004 mixing ratios of CFC 12 decreased rapidly, those of CFC 11 slowly in parallel with the remote atmosphere. From 1998 to 2004 SF6 decreased in parallel with known emissions from NYC. Estimates of local emissions derived from the time series indicated similar trends. Regional scale transport of these gases over 200 km to central Massachusetts was observed. In southern NJ, SF6 appeared to function successfully as a transient tracer giving groundwater ages in agreement with those derived from CFCs. Tracer ages indicated that CCl4 is slowly broken down in this aquifer with a half-life on the order of 20 years.
机译：本文研究了SF6和CFCs在近期地下水测年中的应用，以及作为土壤空气动力学和大气混合的示踪剂。为了确定控制土壤空气中SF6和CFC的过程，在纽约州Sparkill（纽约市附近）观察了几年的混合比例，并将其与大气水平进行了比较。在六个大城市附近也测量了土壤空气中的SF6。为了观察这些气体的时间趋势以及来源和传输，对在LDEO处收集到的SF6和CFC的长时间大气时间序列进行了分析。最后，在新泽西州南部受城市影响的地点使用了六氟化碳和氟氯化碳来记录地下水。土壤空气中SF6的混合比是通过扩散运输来控制的，对应于数月平均的大气水平。相反，CFC的混合比在冬季较低，而在夏季较高，这不能仅通过扩散来解释，而主要归因于气体随温度的空气/水分配变化。对于浅水位或季节性补给，这可能会显着影响示踪剂的年龄，并妨碍从土壤气体剖面观察大气混合比。在大城市中以及在美国东北部大部分地区，强烈的排放导致大气SF6升高到偏远大气水平之上20％或更多，从而阻碍了SF6在市区附近的地下水中的应用。 LDEO收集的大气时间序列表明，从1996年到2004年，CFC 12的混合比迅速下降，而CFC 11的混合比则与偏远大气平行缓慢下降。从1998年到2004年，SF6的下降与纽约市的已知排放量平行。从时间序列得出的当地排放量估计值显示出相似的趋势。观察到这些气体向马萨诸塞州中部区域迁移超过200公里。在新泽西州南部，SF6似乎可以作为瞬态示踪剂成功发挥作用，其地下水年龄与CFCs的年龄一致。示踪剂年龄表明，该含水层中的CCl4缓慢分解，半衰期约为20年。

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