Impact of artificial water and sediment discharge regulation in the Huanghe (Yellow River) on the transport of particulate heavy metals to the sea

Abstract Variations in the concentrations of major particulate heavy metals (PHMs) (Mn, Pb, Zn, V, Cr, and Ni) and fluxes into the sea during the water–sediment regulation scheme (WSRS) in the Huanghe (Yellow River) were examined based on observational and measured data during June and July of 2009. Two stages of variations in the concentrations of PHMs were observed in the WSRS with lower values in the early stage and higher values in the late stage. The early stage corresponded to a high water discharge with coarser sediment that was largely scored from the riverbed, and the late stage corresponded to a low water discharge with much finer sediment that was released from the Xiaolangdi reservoir. The significant increase in PHM concentrations by 2–4 fold from the early to the late stage largely resulted from a decrease in the suspended-sediment grain size and an increase in the quantity of anthropogenic pollutants caused by changes in the sediment sources from riverbed in the lower reaches to the Xiaolangdi reservoir during the WSRS. The concentrations of PHMs, particularly in the late stage of the WSRS, were approximately two times as high as those during the pre-WSRS period as the anthropogenic pollutants have been increasing in recent years. More than 57% of the annual quantity of PHMs was transported to the sea during the WSRS, and over 34% of that from the Xiaolangdi reservoir was delivered to the sea during the late stage of the WSRS over a period of approximately 4–5 days. This large quantity of heavy metals, with a high proportion of labile components because of the increasing contribution of anthropogenic pollutants, emptied into the sea over a short period and may thus drastically alter the eco-environment in the river mouth and its adjacent seas.