Abstract
PURPOSE: We aimed to investigate the spatial O(3) indices (SOMO35: annual sum of maximum daily 8-h ozone means over 35 ppb, AOT40: the accumulated exposure over an hourly threshold of 40 ppb during daylight hours between 8:00 and 20:00 in the growing seasons of plants) in Tehran (2019-2020). METHODS: The data of ambient O(3) concentrations, measured at twenty-three regulatory ambient air quality monitoring stations (AQMSs) in Tehran, were obtained. RESULTS: The annual mean O(3) concentrations were found to be 15.8-25.7 ppb; the highest and lowest annual mean concentration of ambient O(3) were observed in Shahrdari 22 and Shahr-e-Rey stations, respectively. Spatial distribution of exposure to O(3) across Tehran was in the range of 1.36-1.64; the highest O(3) concentrations were observed in the northern, west and south-western parts of Tehran, while the central and south areas of Tehran city experienced low to moderate concentrations. The indices of SOMO35, AOT40f and AOT40v across AQMSs in Tehran was in the range of 1830-6437 ppb. Days, 10,613-39,505 ppb.h and 4979-16,804 ppb.h, respectively. For Tehran city, the indices of SOMO35 and AOT40f were 4138 ppb. days and 27,556 ppb.h respectively. Our results revealed that the value of SOMO35 across AQMSs of Tehran was higher than the recommended target value of 3000 ppb. days. CONCLUSIONS: To reduce O(3) pollution and its effects on both human and plants health, the governmental organizations should take appropriate sustainable control policies.