Morphological Taxonomy Of Heavy Metals In River Sediments

The chemical and toxicological characteristic of heavy metals, which association with the organic matter and sulphide, is different. The two different speciations of heavy metals have different influences on the migration, conversion and toxicity of metals. In this paper, the simulative samples and sediment samples were used as the objects. Through the theoretical calculations and comparative experiments, a new sequential extraction procedure, called four-grade-five-step sequential extraction procedure, was established, based on the BCR sequential extraction procedure.In the four-grade-five-step procedure, the extraction reagent of the reducible fraction was adjusted. The new reagent was 0.1 mol 1^-1 NH₂OH · HCl (adjusted pH=3 with nitric acid). It could efficiently avoid the extraction of the speciation bound to the organic matter ahead of schedule.The NaOH and NH₂OH · HCl were chosen as the extraction reagents. With the dissolving experiments on the sulphide and the residue of oxidisable fraction, the acidity and alkaline threshold value was determined.With the condition and comparison experiments, the 0.01 mol 1^-1 NaOH and 0.1 mol 1^-1 NH₂OH · HCl(0.02mol/L HCl) were chosen as the separation reagents.GBW07310 was treated with four-grade-five-step procedure with the intention to indicate the high accuracy of the procedure. Similarly, five sediment samples were also treated with this procedure. The results indicated that the fraction of different biological availability could be separated; the pre-extraction of the fraction bound to the organic matter was eliminated. And so, the new procedure could distinguish the metal speciation bound to organic matter from that to the sulphide completely on different sediment samples, showing the good adaptability on different locations.