Distribution Characteristics and Assessment of Heavy Metals in the Surface Water of the Syr Darya River, Kazakhstan

The distribution characteristics and pollution assessment of aquatic environment and human health of eight heavy metals (Zn, Cu, Pb, Cd, Ni, Co, Mn and Fe)were measured in surface water of the Syr Darya River within Kazakhstan. The distribution characteristics results showed that the high content of Zn, Cu and Pb samples concentrated in southern Kazakhstan, and another high content of Cu samples concentrated at the entrance to the Aral Sea, the high contents of Fe and Cd samples mainly concentrated in the downstream area of Kyzylorda, the high contents of Co and Ni samples distributed throughout the study area, and the high contents of Mn mainly concentrated upstream in the Kyzylora. A comparison with strict maximum permissible concentration standards for fisheries showed that the impact of current heavy-metal concentrations on fisheries is worrying. The heavy metal pollution index showed that the heavy metal pollution in the research area is high. The health risk assessment of heavy metals in the surface water indicated that Cd can cause a significant carcinogenic risk to human health and it should be a priority target of heavy-metal pollutant control in the region. The results have reference significance for regional water environment and repair of the Aral Sea.