Temporal changes of particulate concentration in the ambient air over the city of Zahedan, Iran

Abstract

Air pollution in developing countries has recently become a serious environmental problem which needs more active air quality monitoring and analyses. To assess air quality characteristics over the city of Zahedan, southeast Iran, airborne Particulate Matter (PM) concentrations with aerodynamic diameters of < 10 µm, < 2.5 µm and < 1.0 µm were measured during the period July 2008 to March 2010 using an Environmental Dust Monitor (EDM-180). The data were analyzed on daily, monthly and seasonal basis. The highest monthly mean PM 10 levels (172 gm -3 ) were recorded during the summer period (JuneAugust), presumably due to frequent dust storms from the nearby Sistan desert located to the north, while less PM 10 concentrations are recorded in winter (December-February) (101 gm -3 ). Linear regression analysis between the PM 2.5 and PM 10 time series reveals high correlation coefficients (r>0.82) for all seasons, implying that PM 10 and PM 2.5 may have the same source regions, or that they are influenced by the same local conditions. In contrast, neutral correlation is found between PM 10 and PM 1.0 in autumn and winter. Taking into account that the annual variation of PM 1.0 exhibits a clear pattern of peaking in winter and dropping in summer (in contrast to PM 10 ), it is suspected that PM 1.0 is of different origin than PM 10 and mainly influenced by local anthropogenic emissions. The daily PM 10 variation is strongly seasonally defined. The maximum PM 10 concentrations occur in the morning hours during winter, autumn (September-November) and early spring (March), while in summer PM 10 concentrations increase significantly in the afternoon closely associated with the intense northerly winds blowing from the desert. As far as the Air Quality Index (AQI) is concerned, its highest monthly values occur in summer, while they are reduced in winter. Desert dust 2 aerosols are found to be the major component in determining the AQI in Zahedan. The analysis shows that 15.3 % of the days are unhealthy for sensitive people, while 2 % are considered as hazardous.

Changes of Permanent Lake Surfaces, and Their Consequences for Dust Aerosols and Air Quality: The Hamoun Lakes of the Sistan Area, Iran

“…Assessment of air quality in Zabol shows that 243 days out of 370 (65%) exhibit air pollution levels of above the air quality standards (>155 μg.m -3 ), a fraction that is much higher than that (26.5%) reported for Zahedan city located also in Sistan about 200 km south of Zabol [52]. The most significant finding is the 129 days (34.9%) that are characterized as hazardous (Table 4), which in combination with the adverse effects on human health, make it clear that environmental conditions in the Sistan region are r a th er p o or fo r hum an w el l -b e i ng .…”

“…The hourly measured PM10 data were daily-averaged, from which the monthly values and seasonal variations were obtained. For further assessing the air quality over Zabol, the PM10 concentrations were used to calculate an Air Quality Index (AQI) [52].…”

“…During summer, the area is under the influence of a low pressure system attributed to the Indian thermal low that extends further to the west as a consequence of the south Asian monsoon system. These low pressure conditions are the trigger for the development of the Levar northerly wind, commonly known as the "120-day wind" [73], causing frequent dust and sand storms, especially during summer (June to August) [74,56] and contributing to the deterioration of air quality [52]. Therefore, one of the main factors affecting the weather conditions over the region is the strong winds rendering Sistan as one of the windiest deserts in the world.…”

“…[93] also studied AQI in Tehran reporting that on 273 days in 2001 the values were higher than those set for the air quality standards; 13% of the days were considered as very unhealthy and 0.27% were classified as dangerous. [52] found that 15 % of the days were unhealthy for sensitive people in the city of Zahedan thatwas affected by Sistan dust storms, while 2 % were associated with a high health risk or were even hazardous.…”

“…One spectacular example of such dust effects is the Hamoun (dry) lakes in the eastern part of Iran that has attracted scientific interest during recent years, since it constitutes a major dust source region in southwest Asia, often producing intense dust storms that cover the Sistan region in eastern of Iran and the southwest of Afghanistan and Pakistan and influencing the air quality, human health and ecosystems as well as aerosol loading and climate from local to regional scales [50][51][52]12]. Particles from the Hamoun dust storms might also cover farm and grasslands to result in damage to crops and fill the rivers and water channels with aeolian material.…”