The Applications of Chemical Analyses of Sediments and Soils in ...

investigated based on HNO 3 HClO 4 / MgNO 3 oxidation followed by HI reduction to H 2 S(Norwitz, 1971) but was subject to high blanks.Extractable metals have been analyzed by shaking the sample with N ammoniumacetate, adjusted to pH 4.8 with acetic acid, in 1:5 ratio for 30 minutes on a wristaction shaker. The extraction is followed by filtration or 'centrifugation and aqua regiadigestion of the filtrate prior to metal analysis.Study is in progress on a satisfactory method for selenium. The hydride-nonflame AAS method developed by Vijan and Wood (unpublished) has shownconsiderable promise for water samples and will be evaluated shortly for sediments.The standard addition technique would have to be used for sediment samples to allowfor interferences such as copper. Most important appears to be a boil-up step with HClfollowing acid digestion.A gas chromatograph method has been found to give good agreement forselenium in NBS fly ash and hence is expected to satisfactory for sediments, althoughmore time consuming that the hydride method.At present, the Jarrell Ash emission spectrograph has not demonstratedsatisfactory agreement with AAS analysis for sediment and soil samples.*_______________* More recently encouraging correlations have been found for some elements.37