for the saline sample sites. Equilibrium calculations indicate 

 oversaturation with carbonate phases. The ammonium and total 

 organic carbon concentrations are among the highest for western 

 Montana sample sites (as are those for the adjacent WET35 site) 

 while the total and orthophosphorous concentrations rank mid-range 

 among sites in the same class. 



The arsenic concentration is the highest among western sites, and 

 is exceeded only by two hypersaline northeastern sampling sites. 

 Copper and iron concentrations rank toward the middle of the range 

 shown by sites in this class; most other trace element 

 concentrations were reported to be below detection limits. 

 However, interferences led to higher detection limits than typical 

 for several elements. 



Chemical history. No other quantitative chemical data for Lahrity 

 Lake are known. Field measurements collected in July 1993 showed 

 a pH of 9.92 and specific conductance > 20,000 microsiemens/cm. 

 Geomorphic indicators imply that Lahrity Lake has probably spilled 

 water during past climatic conditions. At such times, and at 

 intermediate lake stages where the solute load is diluted, salinity 

 can be much lower than during the modern observations. 



Sediments. Littoral sediments are composed of a gelatinous, highly 

 organic and reduced (H2S generating) muck up to 1 foot in depth, 

 overlying a firm cobbly surface of till. 



Among western sample sites, only mine-impacted sediments showed 

 higher concentrations of arsenic. Boron, copper, iron, selenium 

 and zinc concentrations ranked toward the middle of the ranges 

 shown for similar sites. The arsenic concentration exceeded the 

 mean value for western United States soils by a factor of 5. Boron 

 and selenium exceeded mean regional values by factors of 1.4 and 

 1.7, respectively; other trace element concentrations were below 

 their regional mean soil concentrations. 



