distilled water was added to each beaker. The sediment was resus- 

 pended and allowed to settle. The clear supernatant was decanted and 

 the beaker containing the washed sediment made up to 500 milliliters 

 with fresh, deionized glass-distilled water was placed into an ultra- 

 sonic bath (45 Kilohertz) for 30 minutes. Then, the suspension was 

 placed into a glass cylinder, made up to volume with deionized 

 distilled water, and the analysis followed as described in American 

 Society for Testing Materials (1968), except that the dispersing 

 agent (Na4P207) was not added. 



Values are reported as percent by weight remaining in suspension 

 (percent finer than) plotted against equivalent spherical diameters 

 according to Stokes' Law. 



2. Organic Matter Content „ 



Samples of the natural sediment collected from the Patuxent River 

 at Long Point were oven-dried for 24 hours at 100° Celsius, ground fine 

 with a porcelain mortar and pestle, and ashed for 3 hours at 500° 

 Celsius. Organic matter values are reported as percent loss of dry 

 weight on ignition. There was no appreciable loss of inorganic 

 carbonate during the ashing procedure as evidenced by nonsignificant 

 weight losses of calcium carbonate (CaC03) samples which were ashed 

 along with the oven-dried natural sediments. 



3. Heavy Metals . 



Amounts of extractable cations in the mineral solids and the 

 natural sediment samples were determined with mild acid extraction and 

 atomic absorption analysis by Mr. David Boon, Seafood Processing 

 Laboratory, Crisfield, Maryland. Routine procedures for inorganically 

 bound cations as described by Perkin-Elmer Corporation (1971) and 

 Soil Testing and Plant Analysis Laboratory (1970) were conducted for 

 zinc, copper, iron, manganese, lead, cobalt, nickel, chromium and 

 cadmium. Mercury values reported are for total mercury from sediments 

 digested for 1 minute in boiling aqua regia (Dow Method, CAS-AM-70.13, 

 22 June 1970, revised. Chlorine Institute, Madison Avenue, New York, 

 New York). Metal values are reported as mg kg"^ dry weight of solids. 



III. RESULTS AND DISCUSSION 



1. Size Distributions . 



Particle-size distributions of the extremely fine mineral solids 

 and natural sediment used in this project are presented in Figure A-1 

 and Table A-1. Useful descriptions of these materials ranked coarsest 

 to finest by median size are as follows: Silicon dioxide (Fisher No. 

 S-153), median size = 17 micrometers, <2 micrometers = 6 percent; 

 Silicon dioxide (all particles <15 micrometers, median size = 6o2 



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