Stable Hydrogen and Oxygen Isotopes for Groundwater Sources of Penghu Islands, Taiwan
Department of Resources Engineering, National Cheng Kung University, Tainan 701, Taiwan
Department of Hydraulic and Ocean Engineering, Cheng Kung University, Tainan 701, Taiwan
Author to whom correspondence should be addressed.
Geosciences 2018, 8(3), 84; https://doi.org/10.3390/geosciences8030084
Received: 26 October 2017 / Revised: 1 February 2018 / Accepted: 26 February 2018 / Published: 1 March 2018
(This article belongs to the Special Issue Reconstitutions of Paleoenvironments and Paleoclimates using Stable Isotope Geochemistry)
This study used stable hydrogen and oxygen isotopes as natural tracers to investigate their isotopic composition in precipitation, and in shallow and deep groundwater in the Penghu Islands in the Taiwan Strait. We aimed to understand the differences and relationships in isotope compositions within various water bodies and to evaluate the source of groundwater recharge. The hydrogen and oxygen isotopic compositions of sampled groundwater are mainly distributed along the meteoric water line in the Penghu Islands, the variations in the distribution range being minor (the δD values are distributed from −48.2‰ to −37.7‰, with a mean value of −43.14 ± 2.4‰; the δ18O values are distributed from −6.96‰ to −5.46‰, with a mean value of −6.34 ± 0.34‰). The data suggest that the groundwater is sourced mainly from local precipitation. In addition, a comparison of the hydrogen and oxygen isotopic compositions of groundwater and precipitation in Taiwan shows that the δ values for groundwater are distributed between those for precipitation during the northeast monsoon and the southwest monsoon seasons. However, some of the δ values trends towards the isotopic composition of the precipitation during the southwest monsoon season. Thus, the source of groundwater may have a closer association with precipitation during this time.