The aims of this study are to monitor the geochemical variations of groundwater probably related to the earthquakes. The Chai-Nan ground waters, including groundwater, hot and cold springs were sampled regularly during September of 1999 to May of 2001. Dissolved anions (Cl-, Br-, NO3-, PO43- and SO42-) and cations (Na+, K+, Mg2+, Ca2+, Si4+,Al3+, Fe2+, Ti4+ and Mn2+) in samples were measured with an ion chromatograph (IC) and induced coupled plasma — atomic emission spectrometry (ICP-AES), respectively.The results show that the ion concentrations of ground water in Baolai, Meinong, Guosheng, Gaoyang and Chaozhou have no obvious anomalies during earthquakes. The Shuihoutongyuan groundwater has almost constant background, except two anomalous peaks around the date of April 12 and June 12, 2000, which occurred just before the major earthquakes, then quickly dropped to the background level in a few days. The Kuantzeling hot spring shows more fluctuated background and also have anomalous values around the date of September 21 and October 22, 1999, April 25, May 10 and November 1, 2000. Comparing to the oxygen isotope and rainfall records those anomalies occurred in the Shuihoutongyuan groundwater and the Kuantzeling hot spring, respectively might be caused by the major earthquakes.
