Mechanisms of Arsenic Release into Groundwater in Seino Basins, Nobi Plain

Abstract

 Arsenic has been frequently detected over the Japanese environmental standard (0.01mg/L) in groundwater in western part of Nobi Plain. Arsenic leaching experiments using sediments samples in which arsenic was detected over or under the standard, by water, humic acid and calcium ion solution were carried out to investigate the mechanisms of arsenic release into groundwater.
 Dissolved organic carbon (DOC) leached from Nobi formation might enhance arsenic release, which arsenic sorbed onto iron oxide in the sediments, into groundwater constantly by competition of DOC and arsenic sorption and by arsenic-DOC complexation. Lower concentration of calcium ion in groundwater, south-western part of Nobi Plain might result in higher concentration of arsenic in the groundwater.