The Study of Aqueous Colloid in High Arsenic Groundwater: Insights in the Hetao Basin by Ultrafiltrating

Long time uptake As from drinking high As groundwater (>50 μg/L) has caused the residents in the Hetao basin of inner Mongolia suffering from endemic arsenicosis. Investigation of As geochemistry as impacted by colloids was carried out by using ultrafiltration technology. Results reveal that organic and inorganic colloid widely exists in the slightly alkaline and reductive groundwater. The organic colloids with molecular weight > 10 kDa exist as dominant particles in groundwaters. The inorganic colloids are mostly made up of Si, Al/Fe/Mn -oxide/hydroxide as minor components. The colloids slightly affect As(III) geochemical behavior, which proves that it mostly exists on free ions form. However, As(V) varied during successive ultrafiltration. The colloids would combine As(V) and act as As(V) carriers.