HR: 1340h
AN: H13G-1678    [Abstracts]
TI: A method for determining ultra-low concentration of acid-volatile sulfides in sediments and its implication for redox status of aquifer
AU: * Chen, W
EM: chenwenfu@ntu.edu.tw
AF: Taiwan Hot Spring Reaearch Center, Chia-Nan University, 60 Erh-Jen Rd., Sec 1, Pao-An, Jen-Te, Tainan, 717, Taiwan
AU: Liu, T
EM: tkliu@ntu.edu.tw
AF: Department of Geosciences, National Taiwan University, 245 Choshan Rd., Taipei, 106, Taiwan
AU: Shieh, Y
EM: ynshieh@purdue.edu
AF: Department of Earth and Atmospheric Sciences, Purdue University, 550 Stadium Mall Dr, West Lafayette, IN 47907, United States
AB: Relatively high concentrations (7~140 £gmoleg-1) of acid volatile sulfides (AVS), commonly found in marine or organic-rich sediments, were generally determined by methods with detection limit of 1 £gmoleg-1. However, AVS in pristine fresh-water sediments is much lower than 1 £gmoleg-1 and is undetectable by existing conventional methods. We report a new method, the detection limit of which is as low as 1 nmoleg-1, for measuring ultra-low AVS in sediments. The improved experimental procedures include: (1) adding an anti-oxidant buffer to prevent samples from oxidation, (2) shortening the time of trapping hydrogen sulfide gas, and (3) using ¡§methylene blue method¡¨ instead of ¡§iodometric titration¡¨ to detect sulfide concentration. By using the method, we found that AVS in sediments from freshwater aquifers at the Huwei site on the Choshui fan-delta, western Taiwan, falls in the range of 1~61 nmoleg-1. We suggested that the vertical variations of sediment AVS were controlled by redox reactions occurred in each aquifer, groundwater table fluctuations induced by Quaternary sea level change, and lithology of each aquifer. The data of ultra-low concentration of AVS can provide a new insight into hydrochemical evolution of coastal fresh-water aquifers.
DE: 1831 Groundwater quality
SC: Hydrology [H]
MN: 2007 Fall Meeting