ABSTRACT
Although the groundwater of Lanyang plain is regarded as slightly salinized groundwater, the δ34S[SO4] values in groundwater from proximal-fan to distal-fan are widely ranged from −7.5‰ to +60.5‰. The wide distributions of δ34S[SO4] val-ues suggest varied redox condition in the groundwater and/or mixing of different sources of sulfate. Following the classification of δ34S[SO4], δ
2.3 Conceptual models of as cycling in two catchments
This study investigated the sulfur cycling on As mobility in the salinzed-and non-salinzed-groundwater of two catchments. Figure 1(a) conceptually summarizes As cyclic redox reactions
1 INTRODUCTION
High arsenic (As) contaminated groundwater has been observed in coastal aquifers, world widely. The major control factors of geogenic As in groundwater are the site-specific geochemical characteristics, geogenic environment and anthropogenic influences. In Taiwan, As-contamination of groundwater occurred in the coastal area of the Choushui river alluvial fan and Lanyang Plain, mostly accompanied by critical salinization. Previous studies indicated that a possible source of aqueous arsenic was the reductive dissolution of As-bearing iron oxyhydroxides. However there are few reports have addressed the influence of sulfate-sulfide redox cycling on arsenic mobility due to the salinized. The objectives of this study are to evaluate the biogeochemical interactions between As and sulfur in As-polluted and salinized groundwater, and to quantify the natural/anthropogenic influences of sulfate/sulfide on As mobilization, using δ34S[SO4]and δ18O[SO4] sulfur isotopic analyses of groundwater, and geochemical model.
