Environmental evaluation of estuarine sediments

Neutron induced prompt γ ray analysis (PGA) and instrumental neutron activation analysis (INAA) is applied to analyse estuarine sediments. These simultaneous multielement analytical methods are both non-destructive, which is advantageous because they can save much labour in sample preparation and avoid contamination or loss of some constituents due to chemical destruction. In addition, PGA is characterized by its capability for analysing light elements, such as boron, hydrogen, sulphur and silicon, which cannot readily be analysed by INAA. By using these methods to complement each other, many elements, including trace elements, whose distribution in estuarine sediments has not been well understood, can be determined simultaneously. The article describes a case study of the Tama River, which is located in the southwestern part of Tokyo and which has been heavily polluted with municipal sewage. The vertical distributions of elements in the Tama River estuarine sediments and in the sediment of Lake Okutama were determined by INAA and PGA. The behaviour of rare earth elements and boron in the sediments, which has not been well known, was investigated in this study. Finally, PGA and INAA were successfully applied to the Tama River estuarine sediments so as to investigate the distribution and migration of chemical elements under such conditions. PGA is a relatively new analytical method and gives data complementary to those of INAA. Being simultaneous multielement analysis methods, PGA and INAA are quite useful techniques for the basic study of environmental samples