Chemical history. Prior to the DHES sampling, two water quality 

 samples were collected from Bent Flat in November of 1993. One 

 sample came from the immediate area of the springs supplying the 

 fen. The other was collected from near the lower end of the fen, 

 bracketing the WET04 site. Generally, major ion chemistry varied 

 little between the three samples; the springs probably provide 

 quite stable inlet water chemistry. Minor differences should be 

 expected due to dilution and concentration effects and possibly 

 because of changing rates of carbonate precipitation. 



Nutrients, however, are more directly tied to biological activity 

 within the fen and appear to show important spatial and seasonal 

 variability. In November of 1993, nitrate and ammonium 

 concentrations both decreased substantially (and disproportionately 

 to minor dilution effects) between the inlet and lower fen sites, 

 while total phosphorous and total organic carbon concentrations 

 increased by factors of four and five respectively. In September 

 1994, the WET04 site showed total phosphorous and TOC 

 concentrations respectively seven and ten times higher than the 

 lower fen site of November 1993. 



Sediments. An exceptionally high concentration of extractable 

 calcium (24%) reflects the marly nature of Bent Flat sediments. 

 Arsenic, boron, mercury, selenium and zinc occurred in detectable 

 concentrations in the sample of Bent Flat sediment. All were found 

 at low concentrations in comparison to the rest of the data set, 

 with the exception of mercury and selenium. The reported mercury 

 concentration was slightly above the western U.S. mean for soils 

 and other surficial materials, and the selenium concentration 

 exceeded the western U.S. mean by a factor of about 2. 



