Abstract
The release and transport of heavy metals (Ni, Cr, Cu and Pb) from Liangshui River sediments into the overlying water column during the resuspension event were determined using an annular flume with a velocity ranging from 0.15 to 0.35 m/s. It is shown that the suspended particulate matters (SPM) increased as much as nearly 25 times from 165 to 4220 mg/L as the velocity increased. Heavy metals showed an increase in dissolved phase as the velocity increased due to their desorption from the SPM. Acid-soluble heavy metals increased as the velocity increased, indicating that part of the heavy metals transformed from stable phase to labile phase during resuspension. Heavy metal concentrations in the SPM on volume normalization increased by approximately 2–6 times. However, on the mass weighted basis they decreased, approaching the bulk-sediment contents at high velocity, due to the “particle concentration effect”. The distribution coefficients (K D) of heavy metals were higher at slower velocity during the sediment resuspension, which could be attributed to the decrease of fine particles (silt/clay fraction) during resuspension.
Highlights
The release and transport of heavy metals (Ni, Cr, Cu and Pb) from Liangshui River sediments into the overlying water column during the resuspension event were determined using an annular flume with a velocity ranging from 0.15 to 0.35 m/s
Annular flume is more suited to investigating the cohesive sediment dynamics, as the flocculated suspensions are not disrupted by re-circulating pumps and filters [12], and this is beneficial to the measurement of suspended particulate matters (SPM) characteristics
The aim of the present study was to evaluate the effects of different current velocities on the mobilization and distribution of heavy metals using an annular flume during sediment resuspension
Summary
The release and transport of heavy metals (Ni, Cr, Cu and Pb) from Liangshui River sediments into the overlying water column during the resuspension event were determined using an annular flume with a velocity ranging from 0.15 to 0.35 m/s. The contaminants may not be permanently sequestered in sediments When events such as storms, ship traffic or remedial dredging occur, the metals can potentially be released into the water column due to sediment resuspension, which would cause second river pollution. The main factors that determine the magnitude and duration of resuspension are the shear stress exerted on sediments, and the characteristics of sediments, e.g. grain size, organic content, etc All these variables influence the resettling velocities of the particles, and, their residence time in the water column [3]. Annular flume is more suited to investigating the cohesive sediment dynamics, as the flocculated suspensions are not disrupted by re-circulating pumps and filters [12], and this is beneficial to the measurement of SPM characteristics
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