dissolved solids concentration decreased slightly between sampling 

 events. The pH was a full point higher in the September, and the 

 proportional sodium concentration (as measured by the sodium 

 adsorption ratio) was moderately lower. Orthophosphorous and 

 ammonium concentrations were essentially unchanged over this 

 period; the total organic carbon concentration increased by a 

 factor of 5 between the two sample collections. Trace element 

 concentrations were also essentially unchanged, with mid-range 

 concentrations of arsenic and boron and most others below detection 

 limits. 



Note, however, that this degree of seasonal stability may not be 

 representative of the usual trends at Bowdoin. USFWS records from 

 monitoring stations at the inlet and outlet ends of the lake show 

 specific conductance increasing by as much as a factor of three, 

 and decreasing by as much as a factor of 4 within a given year in 

 response to evaporation and episodic inflows of dilute water. 



Chemical history. See above. 



Sediments. The sediment samples collected at this site showed 

 greater differences than did water, probably due to local spatial 

 heterogeneity in sediment characteristics rather than temporal 

 variability. Arsenic concentrations were similar, but boron 

 concentrations differed by more than a factor of three, with the 

 September sample the lower of the two. Copper differed by more 

 than a factor of 2, again with September showing the lower value. 

 Copper, reported at slightly above the detection limit in the May 

 sample, was reported as below detection in September. Selenium 

 showed the opposite pattern. Only the boron concentration of the 

 May sample was above the mean concentration for soils of the 

 western United States, by a factor of only 1.3. 



