The average influent concentration of Se was 10 ppb in Pry se pond, 570 ppb in Peck pond, 

 and less than 10 ppb in Barbizon. Using the Cl-based ECF, the measured concentration 

 of Se in pond cells was less than that predicted by ECF. This implies that some of the 

 Se was lost from the pond water by removal mechanisms such as volatilization, 

 adsorption or reduction to elemental Se. 



The average influent concentration of As was 1.080 ppb in Pryse pond , 620 ppb in Peck 

 pond, and 1,320 ppb in Barbizon pond (Note previous comment). Based on ECF 

 calculations, the measured concentration of As in pond cells was significantly less than 

 CI and had largest extent of immobilization among the trace elements. The removal 

 mechanisms are similar to those identified for Se, and As tends not to accumulate in the 

 water column. 



The average influent concentration of Mo was 2,790 ppb in Pryse pond, 640 ppb in Peck 

 pond, and 890 ppb in Barbizon pond (Note previous comment). Based on ECF calculaltions, 

 the degree of accumulation of Mo was intermediate between As and Se in most ponds. 



The above observations indicate that the reactivity of trace elements in pond facilities 

 are in the order of As > Se ^ Mo with B accumulating in direct proportion to CI, an 

 assumed nonreactive constituent. 



▲ Diurnal Monitoring - Evaporation Rates 



• The Peck, Pryse and Barbizon ponds were extensively monitored over 24-hour periods 

 in March and August 1989 to evaluate evaporation rates with above-the-pond weather 

 data as well as within-the-pond physicochemical changes. 



Diurnal monitoring of weather data was obtained with a portable Campbell Scientific 



weather station every half hour during a 24-hour period. Parameters measured were 



d speed, wind direction, gross solar radiation, relative humidity and air temperature. 



• 



win 



Solar radiation generally peaked before noon in the spring (March) and just before noon 

 in the summer (August) monitorings. Relative humidity tended to be low during the day 

 and increased significantly at night. The air temperature peaked at about noon and 

 reached a minimum around midnight. The direction of wind was more or less scattered 

 from all directions at Pryse and Barbizon ponds and predominantly from the northeast 

 at Peck pond. Wind speeds averaged between 0.4 to 0.6 meters per second. 



At the Peck pond facility, two floating Class A evaporation pans were installed 

 containing water within EC of 14 dS/m, and hourly evaporation rates were monitored 

 over a 47-hour period from August 18-20, 1989. Evaporation during the nighttime 

 contributed significantly to total evaporation. The average cumulative evaporation was 

 14.6 mm. 



In addition at Peck pond, daily evaporation rates were measured with three floating 

 evaporation pans containing waters of ECs ranging from 14 to 90 dS/m in the months of 

 August, September and November, 1989. The EC of water in the pans were increased 

 to correspond to increasing EC in the pond cells over this period. Evaporation rates 

 generally decreased as salinity increased. For example, on September 2, 1989 the daily 

 evaporation rate was 7.7. 6.6, and 6.3 mm per day, respectively, for pans containing 

 waters of EC 14, 20 and 47 dS/m. Moreover, daily evaporation rate wnth EC 14 db/m 

 water was 8.0, 6.2. 4.7, and 2.3 mm per day. respectively, for the months of August 

 through November, 1989. 



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