population can have a range of metal concentrations up to an order of 

 magnitude, thus obscuring differences between techniques that may be small 

 but real. Comparison of clam homogenate values, however, will render obvious 

 differences of less than 25% which would be arduous or impossible to discern 

 using natural populations. 



CONCLUSIONS 



We have shown that a satisfactorily homogeneous reference material can be 

 prepared with a minimum of specialized equipment. The material has a low 

 relative standard deviation for the 10 metals Cd, Cr, Cu, Fe, Mg, Mn, Ni, Pb, V, 

 and Zn. For reasons that are not always clear, the other metals analyzed Al, Ca, 

 Co, and Ti have higher relative standard deviations. The material is useful as a 

 benchmark reference material so that analyses at different times can be shown 

 to be intercomparable. Thus, legal defensibiUty of time series studies of 

 pollution sites can be greatly enhanced. The material is also ideal for methods 

 development and intercalibrations because of its very low relative standard 

 deviation. Therefore, with cooperation from a cafeteria kitchen, it becomes a 

 relatively simple task to prepare such a reference material when a certified 

 standard from a recognized supplier such as NBS is not available. 



ACKNOWLEDGEMENTS 



We gratefully acknowledge the statistical consulting of Drs. J. Callahan and 

 J. Heltshe of the University of Rhode Island, Mrs. M. Boyce of the Roger Williams 

 Dining Hall, University of Rhode Island, and the assistance of Dr. R. Payne 

 and Messrs. B. Reynolds. D. D'Alessio, F. Storti, E. Truesdell, and C. Young of 

 this lab. 



REFERENCES 



1. Eisler, R. 1973. Annotated Bibliography on Biological Effects of Metals in 

 Aquatic Environments, 287 pp. Washington, D.C.: U.S. Government Printing 

 Office (U.S. Environmental Protection Agency, Rep. No. R3-73-007). 



2. Eisler, R. and M. Wapner. 1975. Second Annotated Bibliography on 

 Biological Effects of Metals in Aquatic Environments, 400 pp. Springfield, 

 Virginia: National Technical Information Service. (U.S. Environmental 

 Protection Agency Rep. No. 600/3-75-008). 



3. Pesch, G., B. Reynolds, and P. Rogerson. 1977. Trace Metals in Scallops 

 from Within and Around Two Ocean Disposal Sites. Mar. Pollut. Bull. 8 p. 

 224. 



4. Anonymous. 1975. Catalog of NBS Standard Reference Materials. NBS 

 Special Pubhcation 260. p. 32. 



8 



