An experimental study about the effects of phosphorus loading in river sediment on the transport of lead and cadmium at sediment-water interface

Phosphorus (P) in the river sediment plays an important role in the fate and transport of heavymetals at sedimentwater interface of the aquatic eutrophication environment. To explicate the effect of P loading, the sediments with different P contents were employed in this study to experimentally investigate the adsorption/desorption of Pb2+ and Cd2+ and the releasing behavior of P during the adsorption/desorption processes. Results illustrated a strong affinity between Pb2+ ions and the P-containing sediments in both single Pb and binary Pb + Cd systems. In singlemetal systems, the Pb2+ adsorption capacities of all types of sediments (15.04-19.44 mg g-1) were higher than those for Cd2+ (4.68-5.56 mg g-1). While in binary-metal systems, the Pb2+ adsorption was slightly influenced by the coexisting Cd2+, but the Cd2+ adsorption capacities were decreased by over 5 times. Moreover, the adsorption amount and retention ability of Pb2+ on sediment were enhanced by increasing content of P in the sediment. Meanwhile, the releasing of Pwas also closely depended and significantly inhibited by the Pb2+ attached on the sediment. The P release amounts during the desorption processes of Pb-and Pb + Cd-loaded sediments were over 50 times lower than those from the raw sediments (sediments without heavy metals adsorbed), but the values decreased by a factor of two for the single Cd-loaded sediments. Furthermore, the results of X-ray photoelectron spectroscopy indicated the crucial role of P loading in Pb transport in the sediment and overlayingwater. The findings in this study showed important implications for the transport of heavy metals and P at the sediment-water interface and offered new insights for further explicating the mechanisms of secondary pollution caused by heavy metals and P in aquatic eutrophication environment. (C) 2020 Elsevier B.V. All rights reserved.