Impact assessment of solid runoff on heavy metals migration during high floods on the Amur river

Abstract

Inhomogeneity of the concentrations of chemical elements in the cross-section of the Amur River is considered as a function of the state of their soluble and suspended forms. Flooding of wetlands and urbanized areas contributes to the removal of pollutants into the river channel. The wide spread of fens on the left bank contributes to the concentration of organic matter along the left bank of the river. Terrigenous material mostly comes from the right bank, where agricultural fields are concentrated. The ratio of their concentrations is maintained by the duration of the flood. The mechanisms of redistribution of elements between their suspended and soluble forms have been studied. The mechanisms of sorption of chemical compounds on mineral and organic colloids are described. It was found that mineral colloids with a negative charge due to electrostatic attraction sorb electrically neutral compounds (hydroxoaqua complexes [Mn(OH)2(OH2]0, ammonia [Cu(NH3)4(OH)2]0. The role of organic material in the redistribution of chemical compounds between soluble and suspended forms is shown. Organic colloids with molecular mass > 5.0 kDa precipitate complex cations – [FeHSO4]+, [FeHSO4]2+, [CuHSO4]+. An organic substance with a molecular mass of <2.0 kDa has a greater complexing ability for Fe(2)3+, Cu2+, Zn2+, Mn2+ ions. They bind metals to organo-mineral complexes by chemical interaction and form mobile organo-mineral complexes and heteropolar salts.