APPENDIX 



ANALYSES OF SEDIMENTS 



I. INTRODUCTION 



Experimental work during Project Years I and II used artificial 

 (commercially available) mineral solids to provide base-line data for 

 biological effects of (a) concentrations of solids, (b) different 

 particle-size distributions, and (c) different mineral types of 

 solids. 



Work during Year III concentrated heavily on the biological 

 effects of naturally occurring sedimentary material which was 

 collected by anchor dredge at Long Point (38°29'30"N. , 76°39'45"W.) in 

 the Patuxent River, Maryland. This material was stored in large 

 polyethylene tanks prior to use in our experiments. The sediment 

 surface was covered with a layer of water (salinity range 4 to 6 parts 

 per thousand! to maintain natural ionic equilibria between the sediment 

 and water, as would naturally occur in the Patuxent River. A micro- 

 oxidized sediment layer developed at the sediment-water interface in 

 these tanks after a few days of storage. 



This appendix contains the results of analyses which were per- 

 formed on both the mineral (commercially available) solids and the 

 naturally occurring sediments. Sediment characteristics measured 

 were organic matter content (weight loss on ignition), inorganically 

 bound heavy metals (atomic absorption analysis) , and particle-size 

 distributions (settling diameter analysis). 



The particle-size distributions presented in this appendix were 

 determined in distilled water, and may represent the basic or funda- 

 mental unit particles which can form aggregates with other units and 

 be strongly bound by molecular and atomic forces. These composite 

 units are stable under dispersion methods. Also, the basic particles 

 may form agglomerates in saline water. These composites are relatively 

 weakly bonded by electrostatic forces, surface tension, and "sticky" 

 organic matter. 



II. MATERIALS AND METHODS 



1. Size Distribution . 



Artificial sediments (mineral solids) used in this study were 

 Fuller's earth (^Fisher No. F-90) and silica (Si02, Fisher No. S-135). 



Particle-size distributions of these materials were determined by 

 the sedimentation method (American Society for Testing Materials, 1968) 



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