Evans Lake has one of the highest water column arsenic 

 concentrations of the sample sites. Most other trace elements were 

 below detection limits. 



Chemical history. A single previous chemical analysis is known 

 from Evans Lake. This sample, collected in September of 1972, 

 showed a total dissolved solids concentration of 6310 mg/1 

 (compared to 9743 mg/1 in 1993). The overall sodium - sulfate 

 character of the water was similar the 1993 analysis; the calcium 

 concentration was slightly higher but still very low. 



Specific conductance measurements in September of 1994 were 

 approximately 15% higher than in August of 1993. Shoreline 

 evidence of substantially higher water levels in the historic(?) 

 past indicate significantly higher lake volume and more dilute 

 water chemistry. 



Winter measurements through a continuous ice cover showed near- 

 complete oxygen depletion of the water column above the lake's 

 deepest point. Winter sampling showed ammonium concentrations 7 

 to 8 times the concentration measured at WET19 in August of 1993. 



Sediments. Evans Lake sediments contain arsenic and iron 

 concentrations near mid-range for hydrologically similar sites and 

 zinc concentration near the lower end for sample sites of this 

 class. Other trace element concentrations were below detection 

 limits. High calcium concentrations probably reflect the 

 precipitation of authigenic carbonate minerals. 



