台灣西南海岸平原環境變遷後續研究─(總計畫及子計畫五)台灣西南烏腳病區沈積物與地下水地球化學研究(III)

The southwestern coastal plain area of
Taiwan was well known for its high
concentrations of arsenic and humic
substances in deep groundwater. In order to
explain the origin of arsenic and humic
substances, cations and total organic carbon
(TOC) of sediments, and cations, anions and fluorescence intensity of porewater of
sediments cores from Sin-wen and Kang-wei
were analyzed. The good correlation among
TOC , As, Fe and Mn contents of sediments
suggests that they may have the same
enrichment mechanism. Sediments with the
highest arsenic concentration from Kang-wei,
occur at the horizon deposited in the marine
(lagoon) environment during the Holocene
transgression. It is proposed that the strongly
anoxic environment shown by the deeper part
of the sediment column underneath the coastal
area of southwestern Taiwan was induced by
oxygen-consuming organic matters. The high
concentrations of groundwater might be
attributed to the reduction of iron oxides and
the mineralization of organic matters.