APPENDIX D 

 ANALYSIS OF SEDIMENTS 



1. Introduction . 



Experimental work during 1971 and 1972 used artificial Ccomraercially 

 available) mineral solids to provide base-line data for biological effects 

 of (a) different concentrations of solids, (h) different particle-size 

 distributions, and ic) different mineral types of solids. 



Work during 1973 concentrated on the biological effects of naturally 

 occurring sedimentary material. The material was collected by anchor 

 dredge at Long Point (38°29'30" N. , 76°39'45" W.) in the Patuxent River 

 and stored in large polyethylene tanks before use in experiments. The 

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

 parts per thousand) to maintain the natural ionic equilibria between sedi- 

 ment and water occurring in the Patuxent River. A microoxidized sediment 

 layer developed at the sediment -water interface in these tanks after a few 

 days of storage. 



Analyses were performed on both the commercially available mineral 

 solids and the naturally occurring sediments. The sediment characteristics 

 measured were organic matter content (weight loss on ignition), inorgan- 

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

 tions (settling diameter). 



The particle-size distributions were determined in distilled water, 

 and may represent the basic particles which can be bound into aggregates 

 by atomic and molecular forces. The composite units are stable under dis- 

 persion methods. The basic particles also may form aggregates in saline 

 water; however, these units are relatively weakly bonded by electrostatic 

 forces, surface tension, and "sticky" organic matter. 



2. Materials and Methods . 



a. Size Distribution . Artificial sediments (mineral solids) were as 

 follows: 



(a) Kaolinite 



(1) Hydrite-10 (Georgia Kaolin Company) 



(2) Hydrite Flat-D (Georgia Kaolin Company) 



(3) Hydrite MP (Georgia Kaolin Company) 



(b) Fuller's earth (Fisher No. F-90) 



Particle-size distributions were determined by the sedimentation method 

 (American Society for Testing and Materials, 1968) for paper-coating clays. 



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