| 摘要: | 第一階段在大屯火山地區利用自然梯度執行小範圍的溴示蹤劑施放計畫，初步已有幾個重大發現。首先，利用自然梯度所進行的示蹤劑測試在大屯火山安山岩區域證實是可行的而且利用單裂隙模式對解釋本區地下水傳輸機制是值得一試；但基於地質的非均向與非均質性則需要進一步修正，尤其是水傳輸特性的估算方面；另外，基於火山區域之岩性不均勻之天性，及地下水系統與示蹤劑的複雜性，我們體認到要進一步解釋示蹤劑破裂曲線則必須以不同強度或以多種示蹤劑來輔助；因此我們提出第二階段計畫，希望利用不同的自然梯度來施放示蹤劑，除了增加小範圍溴示蹤劑來建立區域地下水流向並以氫氧同位素當做輔助示蹤劑，更結合水位、水溫來建構大屯火山區中七星山南北兩麓之淺層地水分佈與傳輸，以其進一步建立大屯火山區之淺層地下水架構與機制。 長久以來，我們藉由地下水體氫氧同位素分析和水位與水溫分布，對大屯火山地區的淺層地下水探討已經初步掌握與了解。在大屯火山地區之地下水，大致可以分成北磺溪與南磺溪流域兩大區塊。南磺溪流域大致上由北往南流而北磺溪流域大致上游南往北流，其分水嶺大約位於七星山，但詳細流向有待進一步探討確認。本計畫除了持續收集大屯火山地區之地表水與地下水樣並分析其氫氧同位素值之外，為了掌握地下水在區域岩層中之行為，將選兩個區域利用自然水位坡度先行進行井與井之間示蹤劑施放來探討大屯火山區域淺層岩石水層中的地下水流動途徑並進一步建立區域地下水的流動模式，經初步測試，我們目前選擇以非反應式之溴示蹤劑為本計畫之示蹤劑。我們除了分別在北磺溪與南磺溪流域各一條測線施放溴示蹤劑，並在南磺溪流域加測一組橫向測線，每組必須至少施放2次，估計每次完整施放需耗時2-3個月，收集人力與時間需求頗大。 本次研究將使用水氣氧同位素儀器（Picarro Isotopic Water Liquid Gas Analyzer L1102-i）來測氫氧同位素和四組地下水微量追蹤量測器(Temphion Submersible Smart pH/ISE/Redox Sensor)，其中溴的解析度可達0.01ppm。我們希望透過密集量測在不同地質岩層中地下水、溪水、以及泉水中之18O 與D值並同時在井下施放溴示蹤劑來進一步瞭解地下水在安山岩區的循環機制行為與地下水流動模式，並利用本計劃的機會提供研究生與大學生對地科環境的訓練，而且也希望本研究的結果能提供有效的訊息給予大屯火山監測之用與溫泉水資源，地熱開發與國家公園之管理的重要訊息。
This proposal is the second phase of the pioneer tracer test study in hardrock. We intend to continue conducting inter-well natural gradient tracer test in two profiles of two regions in the Tatun Volcano group with an additional profile. Tracer tests will be conducted in two watersheds in two different periods, dry and wet, using multiple-well natural-gradient tests methods to ensure the result. One is in the relative same geologic formation, TB-MW26 to 30. The other one, TB-MW-11 to 25 and TB-MW-21 to 8, will cross two distinct geologic formations. These two different settings will provide more comprehensive and better quality information form environmental tracers. We also possess several advantages to enable us to propose this project, the location of our department, well-equipped instruments and experience. First, we have acquired and installed a Picarro Isotopic Water Liquid Analyzer L1102-/ to enable us to measure water samples in the Andesitic volcanic bedrocks. Secondly, we have purchased and well tested 4 sets of AquiStarmTempHionTMS mart Sensor which is a submersible water quality sensor and data logger for tracking pH, specific ions, redox, and temperature. The bromide concentration can be detected as low as 0.01ppm. Finally, we are located right nearby the study area and we have done preliminary studies on bromide tracer test in wells. It allows us to sample effectively whenever it necessary. We hope this project will serve as a platform for training students on sampling and measurements skill in hydrogeological parameters. The results gained from this project will provide useful insights for geothermal exploration projects, hot spring resource management and National park management as well. |
