Labile Components of the Amur River Flood Silts

Abstract

The paper considers the possibility of inflow and accumulation of pollutants on the Amur River floodplain as a result of floods and deposition of the flood silts (FS). Labile components of FS – water-dispersible clays (WPC) – are a good indicator of transfer and removal of nutrients and contaminants. The study was focused on FS of the floodplain islands below the confluence of the Sungari River (near Khabarovsk, Far East, Russia). It is shown that, the content of major and trace elements in FS corresponds to the average values for sedimentary rocks independently of the flood power. However, after minor flood, there was a significant accumulation of calcium and phosphorus in WDC, which is accompanied by an abnormal accumulation of As up to 70 mg/kg. After the extreme flood, the As content in WDC fell by more than three times, which is associated with the duration of standing water in the floodplain. The latter causes the dissolution and leaching of apatite group phosphates and the arsenates contained in them as impurities. The process of As accumulation in WDC of the flood silts in low-water years (at minor floods) is not critical, but requires monitoring and further research.