Shannon & Wilson, Inc., Fairbanks, Alaska, USA.
J Contam Hydrol. 2011 Jun 1;124(1-4):1-13. doi: 10.1016/j.jconhyd.2010.11.002. Epub 2010 Nov 26.
At a site with discontinuous permafrost in Fairbanks, Alaska, releases of trichloroethene (TCE), an industrial solvent, have caused contamination of the groundwater. The objective of this study was to investigate the relationship between the migration pathway of the TCE groundwater plume and the distribution of the discontinuous permafrost at the site. The TCE plume configuration is substantially different than what regional hydrology trends would predict. Using GIS, we conducted a geostatistical analysis of field data collected during soil-boring installations and groundwater monitoring well sampling. With the analysis results, we constructed maps of the permafrost-table elevation (top of permafrost) and of the groundwater gradients and TCE concentrations from multiyear groundwater sampling events. The plume concentrations and groundwater gradients were overlain on the permafrost map to correlate permafrost locations with groundwater movement and the spatial distribution of TCE moving with groundwater. Correlation of the overlay maps revealed converging and diverging groundwater flow in response to the permafrost-table distribution, the absence of groundwater contamination in areas with a high permafrost-table elevation, and channeling of contaminants and water between areas of permafrost. In addition, we measured groundwater elevations in nested wells to quantify vertical gradients affecting TCE migration. At one set of nested wells down gradient from an area of permafrost we measured an upward vertical gradient indicating recharge of groundwater from the subpermafrost region of the aquifer causing dilution of the plume. The study indicates that the variable distribution of the permafrost is affecting the way groundwater and TCE move through the aquifer. Consequently, changes to the permafrost configuration due to thawing would likely affect both groundwater movement and TCE migration, and areas that were contaminant-free may become susceptible to contamination.
在阿拉斯加费尔班克斯的一个不连续永久冻土区，三氯乙烯（TCE）——一种工业溶剂——的排放导致了地下水的污染。本研究的目的是调查 TCE 地下水羽流的迁移途径与该地点不连续永久冻土分布之间的关系。TCE 羽流的配置与区域水文趋势预测的有很大不同。我们使用 GIS 对土壤钻孔安装和地下水监测井采样过程中收集的现场数据进行了地质统计分析。根据分析结果，我们构建了多年地下水采样事件的永久冻土顶高程（永久冻土顶）、地下水梯度和 TCE 浓度图。将羽流浓度和地下水梯度叠加在永久冻土图上，以将永久冻土位置与地下水运动以及随地下水移动的 TCE 的空间分布相关联。覆盖图的相关性表明，由于永久冻土表的分布，地下水呈现出汇聚和发散的流动趋势，在永久冻土表高程较高的地区，地下水没有受到污染，并且在永久冻土之间形成了污染物和水的通道。此外，我们还测量了嵌套井中的地下水高程，以量化影响 TCE 迁移的垂直梯度。在一组从永久冻土区下游的嵌套井中，我们测量到了一个向上的垂直梯度，表明地下水从含水层的亚永久冻土区补给，导致羽流稀释。该研究表明，永久冻土的分布变化正在影响地下水和 TCE 在含水层中的运移方式。因此，由于融化而导致的永久冻土配置的变化可能会同时影响地下水运动和 TCE 迁移，而且曾经没有污染的地区可能会变得容易受到污染。
