Surface properties of natural aquatic sediments

Eleven geographically and hydrologically diverse sediment samples were collected from major rivers of China and determined for the surface properties. The results indicate the sediments have a large variation in surface area (6.9–16.0 m2/g of SSAN2, 35.6–73.2 m2/g of SSACPB), surface site density (10.3–149.8 μmol/g) and surface acidity constants (1.56–2.50 of pKint5,a1 and 3.75–5.58 of pKint5,a2) but a small difference in PZSE (3.0–4.0). Within the pH range 3.0–9.0, all sediments present negative surface charges. Their surface charge distribution curves with pH extend between those of SiO2, montmorillonite, kaolinite, α-MnO2, calcite and γ-Al2O3. Correlation analysis reveals that surface area and surface site density of the sediments are correlated strongly with reactive and amorphous iron oxides, total aluminum, clay and total organic carbon, while surface acidity constants, PZSE and the permanent structural charge only show a weak correlation with total aluminum in the sediments.