جستجوی مقالات مرتبط با کلیدواژه "ambient air" در نشریات گروه "پزشکی"

The upward movement of Carbon dioxide (CO2) mass into the air and downwards towards the earth's surface, especially vegetative areas, affected the variability of CO2 concentration in the ambient air. In this pattern, this study aimed to determine the net cumulative value of CO2 concentration (Net_CO2-Con) in an urban area to assess the adequacy of greenspace.

This research method uses CO2 concentration observations within 24 h in 137 observation locations covering an area of 350 km2 in Surabaya city. The sampling location was set at a height of 2 m above the local ground. The CO2 concentration observations were carried out in the dry season and the rainy season for a total of 640 air samples.

The results of this study obtained Net_CO2-Con values for ambient CO2 concentrations in a daily pattern. Starting at night there was a flow of CO2 flux into the air, which reached its peak in the morning, in about 90% of the city area. This event was evidence of a lack of CO2 absorption due to the lack of extensive vegetative areas. On a bright day the CO2 flux flows towards the land, which indicated the presence of vegetation absorption in addition to soil absorption. The seasonal time variability of CO2 flux density had the same pattern for the daily time variability.

Mapping for CO2 flux could be an approach to determine the adequacy of greenspace. Areas of upward movement of CO2 flux density were priority areas for greenspace intensification.

Exposure to formaldehyde in ambient air has attracted a great attention, due to harmful health effects. This study was aimed to determine formaldehyde concentration in winter and spring seasons, in Azadi square region, Tehran, and the relation of variations of CO, NO2, O3, temperature and humidity with formaldehyde concentration was modeled based on Response Surface Methodology.  This cross-sectional study was conducted in 2014–2015 in Tehran. For measuring the formaldehyde concentration, NIOSH3500 method was employed. The concentration of formaldehyde was detected at 580 nm wavelengths by PerkinElmer LAMBDA spectrophotometer model of 25UV/Vis. Data of CO, NO2 and O3 concentration were attained from Tehran Air Quality Control Company. SPSS 16 and Design Expert (version 7) were used for analyzing data. Results showed the concentration of formaldehyde in the spring was on average 4.7 ppb more compared to winter season. The Model fitted for the prediction of formaldehyde showed a significant p-value (<0.001). Moreover, the R2 and Adj-R2 values were obtained about 0.8237 and 0.7607. In this model, it is observed the parameters of CO, NO2, O3 and temperature has a direct relation with the variations of formaldehyde, and humidity has an indirect relation.

 Results indicated formaldehyde concentration in spring season is on overage higher than winter spring. The fitted model showed the CO, NO2, O3 and temperature is in a direct correlation with formaldehyde changes in ambient air, and humidity is in an indirect correlation.

Benzene has been classified as group 1 human carcinogens in the environment by the International Agency for Research on Cancer (IARC) mainly because of its ability to cause acute myeloid leukemia (AML). This study was conducted to detect any probable association between urban benzene pollution concentration and occurrence of AML in different regions of Tehran.
In this descriptive study, demographic data of AML cases recorded in cancer registry centers of Tehran city since March 2006-2011 who met the inclusion criteria were extracted. Eligible criteria included residing in Tehran city for at least 5 years prior to diagnosis of AML. Collected data were correlated with concentration of benzene in ambient air available since March 2001 to March 2011.
The majority of AML subjects were male in the age range of 20-30 years. Maximum concentration of benzene was reported from southern (11.35-106.57 ppb) and central (5.5-60.18ppb) regions of Tehran. The association between benzene concentration with occurrence of AML was observed significant for the period between March 2010 to March 2011 for male patients (Pearson correlation=0.906, P=0.05) in the age range of 30-40 years (Pearson correlation=0.893, P=0.041).
This study suggested probable evidence for the association between the incidence of AML and concentration of benzene in southern and central areas of Tehran city.

The AERMOD is one of the EPA preferred and recommended air quality dispersion models. The AERMOD is a steady state dispersion model for estimating the concentration of pollutants in urban, rural, flat and elevated, ground level and elevated receptors from different volumes, areas or point sources. In this study, in order to evaluate the accuracy of software results, the AERMOD was used for estimating the air pollution concentrations at different locations in Emam Hossein Square and Darvazeh Kazeroun Square of Shiraz City, where there are two DOE air quality monitoring stations. The modeling was performed based on hourly annual metrological data of Shiraz airport. The variable air pollutants’ emission rates were used based on different traffic loads at different hours at night and during the day. The modeling results are compared with the values measured at DOE air quality monitoring stations. The results showed that for the maximum daily concentration of pollutants, the AERMOD estimated values were about 5 and 20 percent higher than the values measured for SO2 and CO; also, the estimated values were two times higher than the measured values for NOx and PM10. Furthermore for the average daily concentration of pollutants, the AERMOD estimated values were about 17, 41, 42 and 38 percent lower than the values measured for NOx, CO, SO2 and PM10, respectively. The quality of ambient air in Shiraz City seems to be good since, except for the PM10, the concentrations of CO, NOx and SO2 were in the range of clean air standard. The maximum daily concentrations of PM10, CO, NOx and SO2 were reported as 0.497 mg/m3, 4246 mg/m3, 0.206 mg/m3and 0.037 mg/m3, respectively.

 This research was conducted to measure the concentration of asbestos fibers in the ambient air of high traffic areas of Isfahan and to evaluate their spatio-temporal variation during summer 2015. 

 Air samples were collected from eleven points covering traffic areas of the Isfahan city including Enghelab square, Azadi square, Bozorgmehr bridge, Ghods square, Ahmedabad square, Artesh square, Emam Hossein square, Nazar junction, Vafaei junction, Felezzi bridge, and Tayyeb fork during 3 months of summer 2015. Scanning electron microscope (SEM) coupled to an energy dispersive X-ray system was utilized to count and identify the asbestos fibers. 

 Seasonal average concentration of airborne asbestos fibers in the studied region was 10.04 ± 4.90 SEM f/l. The results of this study showed that the highest concentration of asbestos fibers was measured in Azadi square (18.08 ± 3.863 SEM f/l) and that the lowest was found in Nazar junction(3.92 ± 1.749 SEM f/l). There was a significant correlation between the concentration of asbestos fibers and atmospheric temperature and humidity (P < 0.05). The mean concentration in September was higher than August and July (11.08 ± 4.66). 

 Heavy traffic in the dense areas of the city, and topographical and meteorological features of the city have a major contribution in asbestos fiber emission which resulted in its exceeded levels from the WHO guideline (2.2 SEM f/l). Therefore, effective strategies such as traffic management, industrial movement, and products replacement can be effective in reducing airborne asbestoses fibers concentrations.

 Levels of asbestos fibers in ambient air of dense areas of Shiraz, Iran, were monitored in winter 2014. 

 Sampling was carried out by directing air flow to a mixed cellulose ester membrane filter mounted on an open-faced filter holder using a low flow sampling pump. Fiber counting on the filters was conducted using both phase contrast microscopy (PCM) method to determine total fibers and scanning electron microscopy (SEM) method to identify nonasbestos from asbestos fibers. 

 The average concentration of asbestos fibers in the ambient air of the study in different areas of Shiraz were 1.18 ± 0.28 PCM f/L and 13.64 ± 2.87 SEM f/L, in which a maximum level was measured in Valiasr square (1.89 ± 0.54 PCM f/L [20.37 ± 5.55 SEM f/L]), and that of in Moallem square was in minimum (1.05 ± 0.47 PCM f/L [12.24 ± 3.04 SEM f/L]). 

 The averages of asbestos fibers in all sampling points were higher than the WHO suggested standards for ambient air (0.05 PCM f/L, 2.2 SEM f/L). This may be attributed to the frequent occurrence of heavy traffic, the existence of relevant industries in and around the city, and the topographic characteristics of the city. Therefore, immediate courses of action such as product substitution, traffic smoothing, and industrial sites relocating should be taken to eliminate asbestos fibers emission.

 In this study, the temporal variations of Benzene, Toluene, Ethyl benzene and Xylene (BTEX) in the atmosphere of Tehran city was investigated. 

 Two air quality monitoring stations, Aghdasieh and Ray, in different locations of the city were selected. Sampling was carried out hourly from Nov 23, 2007 to Dec 22, 2007 in Aghdasieh air monitoring station and from Dec 10, 2007 to Jan 9, 2008, in Ray's air monitoring station by an online BTEX monitoring system. The correlations, repeated measures variance and regressions tests were used for statistical analysis. 

 Results indicated that, concentrations of these compounds were sometimes higher than standard limits and were significantly different in selected stations. However, an approximately similar increasing and decreasing trend was seen among them. In most cases, equations for concentration variations were sinusoidal or fourth-order. 

 According to the results, sinusoidal and fourth-order are most suitable equations for BTEX concentration variations in the ambient air of the city, and the trends of variations are similar in different places of the city.