A 



WATER 



CLAMP- 



CLAMP. 



• PLASTIC GUIDE 



■ WOODEN SUPPORT 



-WOODEN HANDLE 



• VINYL STOPPER 



DETACHABLE POLYETHYLENE 

 CYLINDER 



Figure 11.— Corer for taking sample of sediment and overlying water. The detachable cylinder is 35-40 cm. long. 



a 50.8 mm. sodium iodide crystal detects only 

 the radiation passing through a narrow slit 

 (1.6 cm. high) which is "focused" on a limited 

 portion of the sample cylinder. The detector 

 is hooked to a rate meter and 10 mv. recorder. 

 The radioactivity from a narrow wedge of the 

 water column can thus be measured and re- 

 corded instantaneously and continuously. 



Carrier-free radioactive tracer is added to 

 the column of water through a plastic pipette 

 positioned so that the tracer is released 8 cm. 

 below the surface and in the center of the water 

 column. A "J" shaped plastic aeration tube is 

 attached to the inside wall of the cylinder and 

 extends to the midpoint of the water column. 

 Filtered compressed air is pumped through the 



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