MUD VOLCANIC ACTIVITY IN THE SOUTHWESTERN TAIWAN AND THEIR POSSIBLE INFLUENCE ON ARSENIC MOBILIZATION

Mud volcanoes distributed in the southern part of Taiwan are believed to be sourced from accretionary prism located at the collision boundary between the Philippine Sea plate and the Asian Continental plate. Mud and fluid samples have been collected from Wu-Shan-Ting mud volcano during October 2004, March and June 2005, and analyzed for major ion and stable isotope composition. Major ion (cation and anion) composition shows the dominance of Na and Cl contents in fluids, while, Na, NH4, K, Mg and Cl contents in muds, indicating marine depositional source (rich in NaCl, MgCl and NH4Cl). δD and δ18O values of the fluids indicate that mud volcano fluids have been modified by chemical exchange with 18O-rich crustal rocks and possibly originated from mixing of deep brines with circulating meteoric water. Moreover, isotopic studies indicate that arsenic in groundwater has not been evolved from seawater but likely originated from the deep crustal fluids or rock sources (chemical weathering). This also demonstrates the possible influence of mud volcanic activity on arsenic mobilization. The bacterial isolate study demonstrates that most of the bacteria are gram-negative sphericals and rods, which includes three different Genera, e.g., Bacillus, Halomonas and Acinetobactor. However, phylogenetic relationship of the bacterial isolates can be grouped into Firmicutes and γ-Proteobacteria.