You have two options. In first place, you can work with elutriate and to extract the chemicals in solution and then, analyze the elutriate as a water sample. The other option is work with sediments directly. In this case, you need to do a review on specific technics about sediments. It is important that you check your equipmet before you decide the analytical method to use. Likewise, you need to think about the sensitivity of the results you need. You should to review the EPA web page and other webpages about analytical methods of chemical parameters. Also, you should think about the statistical analysis to be performed on the data.

Manjushree... Please decide about the methodology you want to adopt for your sample sets. There are destructive and non-destructive methods to measure the geochemistry of the sediments. Are you handling sediments from modern deposits  from oceans or from ancient deposits? Carbon and Nitrogen contents can be measured using CNS Elemental Analyzer , where sample is lost (few mgs only) while the major, minor and REE elements concentration can be determined by different instruments including ICP-MS, ICP-OES, AAS (sample is digested chemically) and XRF (sample pellets are made and samples are not lost). Each of these methods have varying accuracy ranging from a few ppm to  several hundred ppm. So  you should  select a method suitable to you having desirable analytical accuracy. 

BRRao

Kenneth M Towe,

Sir,

The diatom frustules are present in the soil sediment and the soil samples were collected from the estuarine area.

Thank you for your responds.

B R Rao,

Sir,

Actually sir the soil sediment sample were collected from the estuarine area. The  deposition time are still unknown, but the sample were collected (1) newly silted up island and other  (2) the area which was a mature land mass. I can spend few mgs of sediment samples for chemical analysis.

Thank you for suggestion.