Mean Concentrations Of Cobalt Research Articles

Geochemical assessment of heavy metal pollution of river basin in Nigeria using stream sediment

Heavy metal pollution has been a source of health problems in humans. These metals are persistent, toxic, non-degradable and often take a long time to be eliminated from the body. This study is, therefore, designed to assess heavy metal pollution of River Basin in Nigeria. Seventy stream sediment samples were systematically collected from an area, approximately 400km2, latitude 7O 00’ and 7O 15’N and longitude 5O 11’ and 5O 19’E. The pollution status of the sediments by heavy metals were assessed by Enrichment Factor (EF), Pollution Load Index (PLI) and Geo-accumulation Index (Igeo). The concentrations of the heavy metals were also compared with United States Environmental Protection Agency (USEPA) Sediment quality guidelines (SQG). The samples were dried in the laboratory, disaggregated, sieved to minus 80 (<177 microns) mesh size using nylon sieve. The sieved samples were, then, digested and the concentrations of As, Co, Fe, Mn, Ni, Pb, V and Zn were determined by Wavelength Dispersive X-ray Fluorescence Spectrometry (WD-XRFS). Results revealed that the mean concentrations of the heavy metals are in the order V>Zn>Pb>As>Ni>Co>Fe>Mn. Furthermore, the mean concentration of lead exceeded both the average world shale and the USEPA SQG values. However, the mean concentration of cobalt, nickel, manganese and zinc were lower than the average world shale values for these elements. The Enrichment Factor (EF) revealed that cobalt was moderately enriched while arsenic and lead were significantly enriched in the sediments. On the basis of the geoaccumulation index, the stream sediments were largely uncontaminated except at some sites that were moderately to strongly contaminated by As and Pb.

Mid-term and long-term results of metal-on-metal total hip arthroplasty

To assess mid-term and long-term results of metal-on-metal total hip arthroplasty. There were 349 operations for the period 2006-2012 in our clinic. Sixty-four patients underwent a full examination. All patients underwent X-ray examination of the pelvis, MRI of hip joint with metal artifact reduction sequence (MARS). The concentration of cobalt and chromium metal ions was determined in blood serum. Each patient completed a questionnaire (Harris, Oxford, Womac, SF-36). 'Survival' of endoprostheses was calculated using the Kaplan-Meier method. According to the Oxford scale, 76.6% of patients had excellent clinical and functional outcomes, 10.9% - good, 9.4% - satisfactory, 3.1% - unsatisfactory. According to the Harris scale, 57.9% of patients had excellent results, 15.6% - good, 7.8% - satisfactory, 18.7% - unsatisfactory. Inclination less than 45 degrees was noted in 77.2% of acetabular components. It is optimal installation angle. According to MRI data, effusion was the main type of periprosthetic changes (16 cases). There were no periprosthetic changes in 33 cases. Pseudotumor was diagnosed in 5 cases. Mean concentrations of cobalt and chromium ions were 1.27 (13.57-0.12) and 0.59 (0.4-0.87) µg/l, respectively. Normal concentration of chromium ions was observed in all cases. Kaplan-Meier survival rate of endoprostheses was 89% (80-97%). There was no correlation between female sex, young age of patients and incidence of complications. It is necessary to exclude pseudotumor in case of pain syndrome and no signs of aseptic loosening of the components of the endoprosthesis.

Determination of Carbon/Nitrogen Ratio and Heavy Metals in Bulking Agents Used for Sewage Composting

Improving the soil quality with organic matter and N, P and K contents are some of sewage sludge benefits. Adjusting carbonaceous materials such as plant wastes to dewatered sludge compost results in increasing the moisture content and improving C/N ratio. This study was conduced for three months in 2005, in Laboratory of Chemistry of Water and Wastewater in the School of Public Health of Isfahan University of Medical Science, to determine the C/N ratio and heavy metals concentration of bulking agents in sawdust, leaves, rice hulls and dewatered sewage sludge. Dewatered sludge was collected from Isfahan sewage treatment plant. Sawdust was collected from sawmills. Leaves were collected from municipality of Isfahan and rice hull from rice mills, then in samples determined C/N ratio and heavy metal according to standard methods. The results showed that concentrations of chromium and cadmium in the mixture of dewatered sewage sludge and bulking agents were lower them those of the standard level. Means of cobalt (115.44 mg kg(-1)), nickel (57.44 mg kg(-1)) and zinc (273.48 mg kg(-1)) concentrations were maximum in dewatered sludge but mean concentration of cobalt (25.66 mg kg(-1)) in rice hull samples and mean zinc (8.99 mg kg(-1)) and nickel (5.106 mg kg(-1)) concentrations in sawdust samples were minimum. The optimal conditions sewage sludge composting, each kilogram of sludge needs 350 g of saw dust, 470 g of leaves and 388 g of rice hull. Amount of heavy metals present in the bulking agents is lower than the amount mentioned for the compost.

Exposure to airborne metals in the manufacture and maintenance of hard metal and stellite blades.

This study evaluated the exposure of Finnish workers to airborne metals. It was conducted in 16 workplaces; 8 tool manufacturing companies (3 of which specialize in the maintenance of hard metal blades) and 8 blade repair shops in the mechanical wood-processing industry. The main emphasis of the study was on exposure in servicing (resharpening), especially involving wet-tip grinding processes. The results show that workers grinding hard metal blades may be exposed to high levels of airborne cobalt even when airborne total dust concentrations are low. The respirable proportion of the total dust was found to be high, and the total dust concentrations correlated well with the cobalt concentrations. Most of the airborne cobalt was water soluble (ionized), but there was also solid particles containing cobalt and other materials in the air of the workplaces. The mean concentration of cobalt in the grinding coolants was high, though it varied considerably. Concentrations of all the other metals measured in the air (tungsten, chromium, cadmium, silver, and nickel) and in the coolants (tungsten and chromium) were low. To reduce workers' exposure to cobalt, it is recommended that grinding machines should be enclosed and equipped with local exhausts. Use of coolants that dissolve less cobalt is also recommended, and the coolants should be changed more often. Brazing should be done in a well-ventilated place, and only cadmium-free materials should be used.

Exposure to Airborne Metals in the Manufacture and Maintenance of Hard Metal and Stellite Blades

This study evaluated the exposure of Finnish workers to airborne metals. It was conducted in 16workplaces: 8 tool manufacturing companies (3 of which specialize in the maintenance of hard metal blades) and 8 blade repair shops in the mechanical wood-processing industry. The main emphasis of the study was on exposure in servicing (resharpening), especially involving wet-tip grinding processes. The results show that workers grinding hard metal blades may be exposed to high levels of airborne cobalt even when airborne total dust concentrations are low. The respirable proportion of the total dust was found to be high, and the total dust concentrations correlated well with the cobalt concentrations. Most of the airborne cobalt was water soluble (ionized), but there were also solid particles containing cobalt and other metals in the air of the workplaces. The mean concentration of cobalt in the grinding coolants was high, though it varied considerably. Concentrations of all the other metals measured in the air (tungsten, chromium, cadmium, silver, and nickel) and in the coolants (tungsten and chromium) were low. To reduce workers' exposure to cobalt, it is recommended that grinding machines should be enclosed and equipped with local exhausts. Use of coolants that dissolve less cobalt is also recommended, and the coolants should be changed more often. Brazing should be done in a well-ventilated place, and only cadmium-free materials should be used.

Trace element contents of some Queensland soils

The weighted mean concentrations of cobalt, copper, gallium, manganese, molybdenum, nickel, vanadium, zinc, and zirconium (and also of iron) are given for 28 soil profiles from Queensland. The concentrations of the same elements in 118 surface soils are presented as histograms. Soils of any one taxonomic group have characteristic, but not unique, trace element properties. The concentrations in surface soils of most of the elements have well-defined frequency distributions.