Method for the Determination of Trace Elements in the Carbonate Fraction of Marine Sediments

Trace elements in the carbonate of marine sediments carry abundant original geological information. However, there is no uniform standard method for the determination of carbonate in marine sediments. In this paper, an extraction method is described for five kinds of trace elements (V, Cr, Co, Ni and Sr) of carbonate phase in the marine sediments by using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS), which is based on the modified seven steps extraction processes by Tessier. Two extraction agents (EDTA and NaAc) were used to extract carbonate fraction for marine sediment samples and standard materials. The results indicate that the NaAc cannot be used to fully extract the trace elements from the carbonate phase in sediments. The EDTA can better extract the carbonate phase of marine sediments, but organic complex metals were also extracted based on the strong complexation ability for metallic elements. In this experiment, we initially removed the ion exchange state by using NaCl and excluding the organic material by pyrophosphate (pH=10) which was an extractant with strong selectivity. Next, the terragenous carbonate of marine sediments was extracted by EDTA. The precision of the method was less than < 5%, the detection limit of each element was in the range of 0.5-4.3 ng/g, and the recoveries were between 88.0%-101.6%. Selectivity and stability of the method meet the requirements of geochemical sample morphological analysis.