Impact of water-sediment regulation on the transport of heavy metals from the Yellow River to the sea in 2015

Variations in particulate and dissolved heavy metal (Cu, Co, Ni, Zn, Pb, Cr, Cd and As) concentrations and fluxes as well as their response to the Water-Sediment Regulation Scheme (WSRS) process in 2015 were studied based on a daily water and sediment survey at Lijin gauge. The results showed that the water and sediment flux increased rapidly in the first stage of the WSRS, which was characterized by high water discharge and suspended sediment concentration (SSC). The suspended sediment was coarser than the natural state, while the particulate and dissolved heavy metal contents increased. In the second stage, the SSC decreased rapidly followed by a gradual reduction in water discharge, the suspended sediment became even coarser and both the particulate and dissolved metal contents showed a decreasing trend. The heavy metal flux during the WSRS period accounted for 42%-54% of the total year, and the transport form was dominated by the particulate form. Dissolved metal contents were affected by the release of heavy metals derived from the channel in the lower reaches, while particulate heavy metals mainly came from erosion of the riverbed and their contents were much lower than Xiaolangdi reservoir sediment. Heavy metal transportation was influenced significantly by the WSRS process. Changes in sediment flux resulted in significant differences in the flux of heavy metals and the distribution of metals in different transport forms between the first and second stage of WSRS. (C) 2018 Elsevier B.V. All rights reserved.