sites with known mining impacts. The lead concentration reported 

 was also the highest for this class. 



Chemical history. No other water chemistry data from Lake Mason are 

 known . 



Sediments. Arsenic, copper and iron concentrations rank toward 

 the high end of the ranges shown by sites of the unglaciated 

 plains. Boron, chromium, nickel, vanadium and zinc concentrations 

 ranked low to mid-range. Most other trace elements were below 

 detection limits. Copper and boron concentrations exceeded mean 

 concentrations for soils and other surficial materials of the 

 western United States by factors of about 2; other trace elements 

 were below regional mean soil values. 



