monitoring the presence of radioactive isotopes on the ocean floor as 

 the system is moving, large areas may be investigated. For these reasons 

 radioisotopic labeling of sediments provides a feasible and practical 

 method of working in the ocean without the disadvantages inherent in 

 laboratory procedures. 



In addition to fluorescent tracers, some work on the use of naturally 

 occurring radioactive materials as littoral tracers has been done, partic- 

 ularly at the University of California, Berkeley. Huston (1963) provides 

 a good review of this work. In general, the method is similar to heavy- 

 mineral tracing in littoral drift studies. Mineral sources must be 

 identified; samples must be taken and analyzed in the laboratory to 

 determine what quantities of the mineral are present. 



An enormous amount of experimental work has been done with both 

 radioactive and fluorescent tracers to determine sediment travel paths 

 in the vicinity of engineering or navigation projects. Generally the 

 approach has been to make an injection of the labeled material at point A 

 and to follow its movement to some resting place at point B. In addition, 

 several attempts have been made to quantify the volume of material moving 

 per unit of time along a given reach of shoreline. 



Of the various sediment tracers, glass, ground to an appropriate 

 size distribution and labeled by an incorporated radioactive isotope, has 

 been the most used. The method of preparation preferred by most investi- 

 gators is to incorporate an inactive isotope as the label in the glass 

 and activate it by irradiation in a nuclear reactor just prior to use. 

 In addition, natural sediment materials have been labeled with sorbed 

 (adsorbed or absorbed) isotopes by investigators interested in closer 

 simulation of the native sediment. Sorbed labels also have the advantage 

 of facilitating the preparation of large amounts of tracer. Disadvantages 

 of sorbed labels for sand tracing are the nonuniformity of sorption on 

 different minerals and the labeling amount being proportional to surface 

 areas rather than mass. 



A number of radioactive labels have been investigated and used. 

 Svasek and Engel (1961) report on the use of scadium-U6 in sedimentation 

 studies near the entrance to Rotterdam waterway, Netherlands. Campbell, 

 et al, (1967) report on the use of silt tagged with copper-6U to study 

 channel silting at Port Hunter, Newcastle, Australia. Sato, et al, (l96l) 

 and Kato, et al, (1963) report on the use of radioactive glass "sand" 

 using various labels to study sediment movement along various sections of 

 the Japanese Coast. For studying movement along the California Coast, 

 Inman and Chamberlain (1959) used quartz sands (with natural phosphorus 

 impurities) which had been subjected to slow neutron irradiation to pro- 

 duce phosphorus-32. To detect the radioactivity, sediment samples were 

 collected and used to expose film plates. Cummins (196k) and Ingram, 

 et al, (1965) report on U.S. Army Engineer Waterways Experiment Station 

 tracer tests using glass particles tagged with gold-198 at Cape Fear River, 

 North Carolina, and Galveston Harbor, Texas, respectively. Krone (1960a) 

 reports on the use of radioisotope tracers to study sedimentation in San 



