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Fine particulates in two size ranges were monitored at the International 

 Boundary site and the Hanrahan site. Although there are presently no 

 ambient standards for fine particulates, the U.S. Environmental Protection 

 Agency has proposed standards for particulate matter with diameters less 

 than 10 microns (PM-10). The proposal calls for an annual average in the 

 range of 50-65 ug/m^ and a 24-hour standard in the range of 150-250 

 ug/m^. Montana did not actually sample the 10 micron and less category; 

 however, the data from the less than 2.5 and less than 15 micron diameter 

 categories provides a good indication that PM-10 levels would be in 

 compliance with the proposed standards. 



During 1985, the Montana Department of Health and Environmental Sciences 

 continued to operate an extended network of lead dioxide sulfation plates 

 in the Poplar River area. The sulfation plate network includes the 

 existing three primary monitoring sites and five additional locations: 

 the Microwave Tower, Flaxville, the TV Tower, Four Buttes, and Scobey 

 Downtown. The objective of the sulfation plate network is to obtain a 

 broad geographical indication of sulphur dioxide concentrations and to 

 investigate the relationship between sulfation rate and sulphur dioxide 

 concentrations. Montana anticipates that funding will not be available in 

 the future for continuous sulphur dioxide monitoring. Therefore, Montana 

 hopes that sulfation rate will prove to be an inexpensive substitute. 



