Effect of Water Level and Salinity on Metal Fractionation in Sediments of the Yellow River Delta

In estuarine wetland ecosystems, the heavy metal content and especially the metal fractionation are influenced by water and salinity conditions. We collected sediments from the intertidal zone of the Yellow River Delta, where the water and salinity conditions changed frequently. The incubation experiments at different water and salinity levels were carried out in the laboratory to investigate the migration of Cr, Cu, Zn, Cd and Pb in the intertidal sediments. The results showed that the proportions of the residual fractions of Cr, Cu, Zn and Pb in the intertidal sediments were high, and the exchangeable Cd fraction was the highest. The Cr and Pb fractionations were significantly associated with the water level conditions. Different water level conditions were significantly related to the contents of the oxidizable fractions of Cr, Zn, and Cd. Except for the oxidizable Cu fraction, all Cu fractions were significantly correlated with the water conditions. Increasing salinity enhanced the migration risk of Cd and Pb. High salinity reduced the migration risk of Cr, Cd and Cu. The results of this study demonstrated that tidal floods increased the migration risk of Cd and Pb, and high salinity reduced the migration of Cr, Cd and Cu.