Molybdenum in the Atmosphere

Release of molybdenum into the environment can occur through weathering, agricultural uses of molybdenum compounds, and industrial processes. Molybdenum in air has a range of values. Molybdenum concentrations in air are higher in urban areas than in rural areas. The combustion of fossil fuels is a constant source of molybdenum [Parker, 1986]. Relatively high concentrations are present in air-borne ash expelled usually during the combustion of fossil fuels.

[US DHEW, 1966; Adler, 1957; Adkins and Losee, 1970; Allaway et al., 1968; Anderson, 1966; Anderson and Grensfelt, 1973.]
Parker, G. A., Molybdenum in: Hutzinger, O. (ed.), Handbook of Environmental Chemistry , 1986, 3D, 217. Springer-Verlag, Berlin.
US DHEW, Air Quality Data, National Air Sampling Network, 1966, Public Health Service.
Adler, P., Odont. Révy Suppl., 1957, 48.
Adkins, B. L. and Losee, F. L., N.Y. State dent. J., 1970, 36, 618.
Allaway, W. H., Kubota, J., Losee, F. L. and Roth, M., Arch. Environ. Health, 1968, 16, 342.
Anderson, R. J., Brit. dent. J., 1966, 120, 271.
Anderson, G. and Grensfelt, P., IVL, Gothenburg B, 1973, 138.

Molybdenum in the Atmosphere
Description of AreaSourceConcentration /microg/m3
Atmosphere [1]   <0 - 0.03
Industrial UK [2] Air borne ash 10 - 40
Industrial UK [3] Light heating oil 0.1
Industrial UK [3] Heavy heating oil 0.5
Rural Sweden [4] Moss 1.0
Industrial Sweden [4] Moss 7.6
Heavy industrial Sweden [4] Moss 400
Steel works Sweden [4] Moss 560
Urban USA [5]   10 - 30
Uninhabited USA [5]   0.1 - 3.2
Municipal waste [6] Mo(CO)6 in landfill gas 0.2 - 0.3

[1] Sullivan, R. J., Pollution Aspects of Chromium and its Compounds, 1969, Technical Report, Litton Systems Inc., Environmental Systems Division, Bethesda, Md. (Quoted in Schroeder, H. A., Balassa, J. J. and Tipton, I. H., J. Chronic Dis., 1970, 23, 481).
[2] Smith, A. C., J. Appl. Chem., 1958, 8, 636.
[3] Anderson, G., Grensfelt, P., IVL, Gothenburg B, 1973, 138.
(Quoted in J. Lener and B. Bibr, J. Hygiene, Epidemiology, Microbiol. and Immunol., 1984, 28, 405).
[4] Lindan, L., and Sundderg, K., SNV PM, 1974, 428.
(Quoted in J. Lener and B. Bibr, J. Hygiene, Epidemiology, Microbiol. and Immunol., 1984, 28, 405).
[5] Air Quality Data, National Air sampling Network, Ed. 1966, US DHEW, Public Health service.
[6] Feldmann, J., Cullen, W.R..,Occurrence of volatile transition metal compounds in landfill gas: Synthesis of molybdenum and Tungsten carbonyls in the environment, Environmental Science & Technology, 1997, 31, 2125-2129.

Mo in ambient air urban areas 0.01 – 0.03 microg Mo/m3
Rural areas 0.001 – 0.0032

Schroeder, H.A., A sensible look at air pollution by metals, Arch. Environ. Health, 1970, 21, 798 – 806.

Concentrations of molybdenum and other metals were determined in ambient air as part of an ongoing air-quality monitoring programme.the mass concentrations and metals speciation of ambient aerosols collected in Oxford, OH were compared with those collected in three urban centers (Cincinnati, Middletown, and Hamilton) in the Greater Cincinnati region. PM2.5 particles (< 2.5 microm) typically originates from the combustion of fossil fuels for power and transportation and from manufacturing processes. The mean PM2.5, PM10 and TSP mass concentrations (microg m-3) of the samples collected in 2005 in Oxfordwere: PM2.5, 15.6±8.1, PM10, 16.2±7.3; TSP, 37.0±7.8. The PM2.5 contributed 95% to PM10 and 60% to TSP (total suspended solids). Arsenic, antimony, cobalt, and lead were predominantly contained in PM2.5; cadmium, chromium, iron, nickel, molybdenum, silicon, vanadium, and zinc in PM10.. Since these metals are typically associated with anthropogenic metals emissions (traffic, combustion of fossil fuels, industry) and it was expected that these metals would be present in the smaller particle size ranges.

Wojas, B. and Almquist, C., Mass concentrations and metals speciation of PM2.5, PM10, and total suspended solids in Oxford, Ohio and comparison with those from metropolitan sites in the Greater Cincinnati region, Atmospheric Environment, 2007, 41, 9064-9078.

Molybdenum atmospheric deposition in mosses

The deposition of manganese, molybdenum and nickel in the county of Obrenovac (Serbia) in four moss taxa (Bryum argenteum, Bryum capillare, Brachythecium sp., and Hypnum cupressiforme) is presented. The distribution of average heavy metal content in all mosses in the county of Obrenovac is presented on maps, while the long-term atmospheric deposition (in the mosses Bryum argenteum and B. capillare) and short term atmospheric deposition (in the mosses Brachythecium sp. and Hypnum cupressiforme) are discussed and given in tabular form. Areas of the highest contaminations are highlighted

Vukojevic, V., Sabovljevic, M., Sabovljevic, A., Mihajlovic, N., Drazic, G., and Vucinic, Z., Determination of Heavy Metal Deposition in the County of Obrenovac (Serbia) Using Mosses As Bioindicators. IV. Manganese (Mn), Molybdenum (Mo), and Nickel (Ni), Archives of Biological Sciences, 2009, 61, 835-845.

Airborne dust: Airborne concentrations of metals and total dust during solid catalyst loading and unloading operations at a petroleum refinery

Workers handle catalysts extensively at petroleum refineries throughout the world each year; however, little information is available regarding the airborne concentrations and plausible exposures during this type of work. In this paper, we evaluated the airborne concentrations of 15 metals and total dust generated during solid catalyst loading and unloading operations at one of the largest petroleum refineries in the world using historical industrial hygiene samples collected between 1989 and 2006.

The total dust and metals, which included aluminum, cadmium, chromium, cobalt, copper, iron, lead, manganese, molybdenum, nickel, platinum, silicon, silver, vanadium, and zinc, were evaluated in relation to the handling of four different types of solid catalysts associated with three major types of catalytic processes.

Consideration was given to the known components of the solid catalysts and any metals that were likely deposited onto them during use.

A total of 180 analytical results were included in this analysis, representing 13 personal and 54 area samples.

Of the long-term personal samples, airborne concentrations of metals ranged from <0.001 to 2.9mg/m3, and, in all but one case, resulted in concentrations below the current U.S. Occupational Safety and Health Administration's Permissible Exposure Limits and the American Conference of Governmental Industrial Hygienists' Threshold Limit Values.

The arithmetic mean total dust concentration resulting from long-term personal samples was 0.31mg/m3.

The data presented here are the most complete set of its kind in the open literature, and are useful for understanding the potential exposures during solid catalyst handling activities at this petroleum refinery and perhaps other modern refineries during the timeframe examined.

Quote:

“In conclusion, the data reported here, which are the most complete set in the open literature to date, consist of both personal and area measurements of 15 metals and total dust collected during the loading and unloading of four different types of solid catalysts (Ni–Mo, Co–Mo, Pt–Re, and zeolite) associated with three major types of catalytic processes (desulfurization, reformation, and fluidized catalytic cracking). The findings of this analysis suggest that the airborne concentrations of metals and total dust generated during solid catalyst loading and unloading at this petroleum refinery, and perhaps other modern refineries during the timeframe examined, were generally low. Further research is recommended, though, to help characterize the levels across the industry. Funding This work was partially funded by Hess Corporation, an energy company that has been involved in litigation related to possible catalyst exposure. Conflict of interest statement One of the authors has served as an expert witness for Hess Corporation on matters relating to industrial hygiene, exposure assessment, risk assessment, and/or toxicological issues related to catalysts.”
Molybdenum concentrations (mg/m3): Heavy distillate desulfurization area Sample result (mg/m3) Unloading Min. = 0.022 Mean = 0.034 Max. = 0.051.Loading Min. = 0.27 Max. = 0.61

Lewis, Ryan C., Gaffney, Shannon H., Le, Matthew H., Unice, Ken M., and Paustenbach, Dennis J., Airborne concentrations of metals and total dust during solid catalyst loading and unloading operations at a petroleum refinery, International Journal of Hygiene and Environmental Health, 2012, 215, 514-521.

See also

Hery, M., Gerber, J.M., Hubert, G., Hecht, G., Diebold, F., Honnert, B., Moulut, J.C., 1994.Exposure to metallic catalyst dust: manufacturing and handling of catalysts in the chemical industry. Ann. Occup. Hyg. 38, 119–135.

Methane sensor MoO3

Methane Gas Detection in Environment Using Shape Dependent alpha-MoO3 Nanosensor

In this work, one dimensional (1-D) orthorhombic molybdenum trioxide (alpha-MoO3) nanostructures were synthesized using sol-gel technique and deposited on alumina substrates pre-patterned with interdigitated gold electrodes. Microstructure characterization was done using X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), and Micro Raman spectroscopy techniques. Different morphology viz nanospheres, nanoplatelets (300-600 nm) and nanobars (average length of 1 mu m, width of 100 nm and thickness of 100 nm) which are predominantly orthorhombic (alpha-MoO3) were obtained. The growth along (001) direction of the nanobars was enhanced by increasing the annealing temperature to 550 degrees C. The fabricated sensors were tested with methane gas at elevated temperatures of 300 degrees C. The structural and gas sensing properties of alpha-MoO3 nanostructures are correlated

Rakkesh, R. A., Prasad, A. K., Dash, S., Tyagi, A. K., and Balakumar, S., Methane Gas Detection in Environment Using Shape Dependent alpha-MoO3 Nanosensor, Solid State Physics, Pts 1 and 2, 2012, 1447, 249-250.