AIR QUALITY 



Montana 



The State of Montana continued to operate three air monitoring sites in the 

 Poplar River area of Montana during I982. The parameters monitored include: 

 sulphur dioxide, Beta scattering coefficient, total suspended particulates, 

 sulphates and nitrates. 



During I982, sulphur dioxide concentrations remained below both Montana and 

 United States ambient air-quality standards. The maximum one-hour concentration 

 of 6.0 parts per hundred million (pphm) was recorded at the International Boundary 

 site during September. This concentration is approximately one-eighth of the 

 Montana standard. The highest Z't-hour concentration of 2.0 pphm occurred in 

 March, also at the International Boundary site. The Montana 2A-hour sulphur 

 dioxide standard is 10 pphm. A comparison of sulphur dioxide concentrations 

 with Class II Prevention of Significant Deterioration increment, demonstrates 

 that the 24-hour concentration is the averaging time which consumes the most 

 increment. The 2.0 pphm 24-hour average at the International Boundary site 

 would consume 57 percent of the available increment. 



The Montana 24-hour standard for total suspended particulates was exceeded 



on May 5, I982. On that date a concentration of 234 micrograms per cubic meter 



■I 

 (ug/m ) was recorded at the International Boundary site. An examination of 



the sample and Montana meteorological data indicated that May 5, 1982 was 



characterized by high winds, which resulted in excessive wind-blown dust off 



agricultural fields. This concentration also exceeded the United States 



secondary standard but did not exceed the health-based primary standard. 



2A. 



