Distribution and adsorption of metals on different particle size fractions of sediments in a hydrodynamically disturbed canal.

Sediment resuspension widely occurs in environments with hydrodynamic disturbances, where particles are sieved into different grain size groups. The particles of different grain size exhibit heterogeneity of their physical, chemical or biological features. This research addressed the association of metals on size fractional particles sieved by sediment resuspension in a canal of Taihu basin, a highly urbanized and human-impacted area. Surface sediment samples were collected from upstream to downstream sections of the canal to analyze the concentrations and fractionation of lead (Pb), zinc (Zn), and copper (Cu). One sediment sample was sieved into five different particle size groups (50-150 μm, 30-50 μm, 10-30 μm, 5-10 μm and <5 μm) through the wet sedimentation method. The strong adsorption ability of metals on fine particles is attributed to enrichment with organic matter and iron/aluminum (Fe/Al) oxides, with the increase in Pb, Zn, and Cu concentrations from 34.2 mg/kg, 263 mg/kg, and 32.5 mg/kg of 50-150 μm size group particles to 71.4 mg/kg, 698 mg/kg, and 137 mg/kg of <5 μm size group particles, respectively. The fine particles showed stronger sorption ability on Pb than Zn and Cu, with the Freundlich isotherm constant (K) values of the adsorption isotherms in the <10 μm size particle group ranging from 3.7 to 5.9 g/kg for Zn and Cu versus from 11 to 18 g/kg for Pb, probably causing difference on metals accumulation and releasing risk among metals in the downstream lakes with changeable environments.