ICP-MS Determination of Combination States of Heavy Metal Elements in Solidified Materials of Cement-Based Sediment with Separation by Modified BCR Sucessive Extraction

For determination of combination state of 4 heavy metal elements (i.e., Pb, Cu, Cr, Zn) in solidified materials of cement-based river sediment, testing samples were prepared as follows:cement was mixed thoroughly with river sediment by the mass ratio of 2 to 8, and the mixture was dried and moulded into solid cubes, which were then wet-cured in curing boxes for 3, 7, 14, 28, 45 and 60 days at (20±0.5)℃ with relative humidity of >95%. For use as an analytical sample, the solid cube should be crashed to pass through sieve with pore of 75 μm. For determination of total content of the 4 heavy metal elements. 0.100 g of the crashed sample was taken and digested with 3 mL of HNO₃ and 1 mL each of H₂O₂ and HF in a microwave oven. The digested solution was then heated at 150℃ to expel acids, and after cooling the solution was diluted to 50.0 mL with water and used for ICP-MS determination. Another portion of 0.800 g of the sample was taken and treated by the modified BCR successive extractions to obtain 4 sample solutions containing the 4 heavy metal elements in 4 combination states, i.e., (F1) acid extractable state, (F2) reducible state, (F3) oxidizable state and (F4) residual state, and contents of the 4 heavy metals were determined by ICP-MS in the same way. In the MS analysis, Sc, Ge, In and Bi were chosen as internal standards to calibrate changes of response signals and to eliminate instrumental drifts and matrix effects. It was shown that the proposed method gave results satifactory in accuracy and precision, and that characteristics and regulations of migrations of the 4 elements during the course of solidification were found, based on data of ICP-MS analysis with separation by the modified BCR successive extraction method.