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Table 8. Sulphur Dioxide in Ambient Air, Montana 

 (Parts per Million) 



Table 9 shows the sulfation rate data collected at eight locations 

 in the Poplar River area. The highest monthly average was 

 0.05 milligrams of sulphur trioxide per 100 square centimetres per 



day. 



The DHES generally considers monthly averages above 



0.5 mg SO_/cm /day as indicating areas of possible concern. 



Although the air quality monitoring project has been terminated, 

 the DHES will continue to collect sulfation plates in the Scobey 

 area. This will allow the DHES to note any changes in the existing 

 air quality and to determine its geographic extent. 



Wind data were also collected at the Marlenee Ranch site. The 

 predominant wind directions for all three quarters at this site 

 were northwest (NU & NNW) and southwest (SSW & SW) . The wind 

 speeds from the northwest sector averaged around 5 m/s 

 (11 miles/hour) while the wind speeds from the southwest sector 

 averaged around 2 ra/s (4.5 miles/hour). The wind roses are 

 considered by the DHES to fairly represent winds in the Scobey area. 



