A Statistical Study of Mashhad׳s Air Polluted Days

For a precise study of polluted days in terms of persistence and stability , this paper statistically studies the air pollution of Mashhad.The data related to the pollution was provided daily by environment department of Razavi Khorasan province from 2003 to 2009. After collecting the data and specifying statistical period , the pollutants with the most impact on the air pollution of Mashhad ( carbon monoxide , nitrogen dioxide , sulfur dioxide , ozone and particulate matters ( PM10 ) were selected among these data for specifying air quality. Then , statistical analysis was made in order to specify persistence and number of the polluted days and finally , these results were obtained that the air pollution has been ranging from 2003 to 2009 with a reduction trend. In addition , during the desired period , particulate matters (PM10 ) had the maximum amount.The most polluted seasons of Mashhad are autumn and winter. In the terms of annual distribution , the year 2007 with 29 days had the maximum amount of pollution. December with 18 days has been specified as the most polluted and June the cleanest months of the year. In addition , after studying the number of polluted days with the persistence of two days and more , it was revealed that the years 2007 and 2008 were more significant in terms of persistence than the other years.