جستجوی مقالات مرتبط با کلیدواژه « heavy metals » در نشریات گروه « علوم »

In this study, concentrations of heavy metals in soils around a Zn-smelter in Qeshm island, Iran, are investigated. Calculated geoaccumulation index (Igeo), contamination factor (Cf), and contamination degree (Cdeg) values indicate surface soil contamination by toxic metals (As, Cd, Pb, and Zn). The results also indicate that most contaminated areas are located in the vicinity of the smelter and waste pile. However, concentrations of soil metals decrease with increasing distance from the pollution sources. Results from a potential ecological risk assessment indicate high risk in areas around the smelter. Statistical analysis also confirms the role of the Zn-smelter in soil contamination in the study area.

In this study, eight bacterial isolates showing a suitable resistance to heavy metals were obtained from electroplating effluents. The isolates were grown on nutrient agar including 1 mM of each heavy metal of cobalt (Co), chromium (Cr), mercury (Hg), zinc (Zn) and copper (Cu). The minimum inhibitory concentrations (MICs) of the isolates were determined using different concentrations of heavy metals (1-5 mM) by broth dilution method. One of the isolates showed higher MICs of 5, 5, 4, 3 and 3 mM when grown on Co, Cr, Hg, Zn and Cu, respectively and selected for further study. The bacterial identity was determined by various biochemical and physiological experiments. The optimum temperature and pH for the growth of the strain were 30˚C and 7, respectively. The isolate was resistant to ampicillin, cephalotin, amikacin and gentamicin. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the isolate belongs to the genus Comamonas with 99% similarity to Comamonas testosteroni; it was then designated as Comamonas sp. HM_AF12. Atomic absorption spectrometer analysis showed that 80% of chromium was removed from 5 mg/L of chromium solution after 1 h. The results suggest that Comamonas sp. HM_AF12 obtained from effluent owing to its high resistance to toxic heavy metals has great potential to be employed for bioremediation of chromium contaminated effluents.

During this research, bacteria resistant to metals were evaluated in the soil of Isfahan Province. According to the sampling locations the soils are classified as agricultural soils, non-agricultural soils and sediments of the Zayanderood Riverbank. The bacteria resistant to lead (2 mM), copper (5 mM), cadmium (0.5 mM) and arsenic (5 mM) were identified, and then during later stages, the minimum inhibitory concentration (MIC) for the growth of the bacteria resistant to metals were determined. The dry cellular weight and the metal uptake rate were also defined for the bacteria resistant to metals.

The removal of copper (II), zinc (II), and chromium (III) from wastewater by carrot residues (CR) was investigated to evaluate cation exchange capacity. The effects of solution pH and co- ions were studied in batch experiments. Adsorption equilibria were initially rapidly established, and then decreased markedly after 10 min. Column experiments were carried out in a glass column filled with CR to evaluate the metal removal capacity. The influences of the feed concentration and feed rate were also studied in order to compare the dynamic capacity for metal binding in different feed concentrations.