ABSTRACT
Background: inhalation of radon and its short-lived decay products is one of the most significant sources of exposure to natural radiation. Radon is the second cause of lung cancer in the populations. The present study was carried out under the projects of national radon, with the aim of determining the concentration of indoor in the city of Qom located in the central semi-arid region of Iran
Materials and Methods: radon measurements were carried out in 123 dwellings using passive sampling with CR-39 detectors for 90 days. The map of radon concentration distribution was prepared using Arc GIS software and the statistical analysis was performed with SPSS version 20
Results: indoor radon concentrations in Qom dwellings ranged from 15-259 Bq m[-3]. The arithmetic mean of indoor radon concentrations on basement, ground floors, first floors and second and upper floors were 123.43, 87.94, 63.72 and 40.69 Bq m[-3], respectively
Conclusion: a correlation was found between the distances from fault zones and measured indoor radon concentration. In most of cases, radon values were lower in well- ventilated dwellings in comparison with poorly-ventilated ones. Moreover, high radon concentration levels were observed in basements. The results indicated that in 30 places [24.3% of cases], the radon concentrations were higher than the reference levels recommended by the World Health Organization [100 Bq m[-3]]
ABSTRACT
Nickel [II] and cadmium [II] are important in environmental pollutant. Biosorption of heavy metals can be an effective process for the removal and recovery of heavy metal ions from aqueous solutions because of the decrease in sludge problems, economical issues, high efficiency and compatibility with the environment. Power of wasted activated sludge have been contact with nickel [II] and cadmium [II] solutions in 0.25 and 0.75 milli molar invarious pHs and mixing pace, at 24-26 [degree sign]C temperature on batch reactor system .After two hours [continuously 5-420 min in kinetic study] samples were analyzed with atomic absorption spectrophotometer. The kinetic study results show that equilibrium adsorption time for nickel [II] and cadmium [II] reached within 2 hr, but the profile curve of cadmium [II] biosorption was smoother than nickel [II] biosorption. Both metals adsorption followed the Langmuir model and the maximum adsorption capacity [q[max]] for nickel [II] and cadmium [II] was 0.195 and 0.37 milli mole per gram respectively. The increase in pH resulted in adsorption increase for both metals. For cadmium [II] at 0.25 and 0.75 mMinitial concentration there was no adsorption at pH 2 where as nickel [0.25 mM] adsorption was observed at the same pH. The optimum mixing rate for both metals was 200 rpm and this effect was more obviously in greater concentration. Like other biosorbents, wasted activated sludge showed greater capacity for cadmium [II] biosorption than nickel [II]. Cadmium [II] in modeling and biosorption characteristics study had more conformity than nickel [II]