Molybdenum in the Environment
Molybdenum in the Hydrosphere
One of the important methods of transport of molybdenum from the area of release is by water. Because of the effect of molybdenum on livestock the U.S. Committee on Water Quality Criteria has recommended a limit of 5 ug Mo/l in irrigation water for continuous use on all soils and 50 ug Mo/l for short term use on fine-textured soils., [U.S. Department of the Interior, 1968]. Other sources include the waste water from industrial processes, the transportation of ores and the distribution of sewage all of which can result in widespread addition of molybdenum in the environment.
U.S. Department of the Interior, 1968
Molybdate transport in groundwater is retarded by sorption, depending on the pH and the levels of phosphate and sulfate in the water.
Davis, J. A., Field Experiments. Proceedings Metal Speciation and Transport in Groundwaters, Jekyll Island, Georgia., 1989, Lewis Publ., Chelsea, Michigan.
Analysis
Trace amounts of molybdenum(VI) have been determined spectrophotometrically using 5,7-dibromo-8- hydroxyquinoline in alloys, steels, and environmental waters (inland and surface), biological samples (human blood and urine), and soil samples. The method has high precision and accuracy (S = +/- 0.01 for 0.5 mug mL(-1))
Ahmed, M.J. and Haque, M. E., A rapid spectrophotometric method for the determination of molybdenum in industrial, environmental, biological and soil samples using 5,7-dibromo-8-hydroxyquinoline, Analytical Sciences, 2002, 18, 433-439.
A chitosan resin functionalized with 3-nitro-4-amino benzoic acid moiety (CCTS-NABA resin) adsorbed metal ions vanadium, gallium, arsenic, selenium, silver, bismuth, thorium, tungsten, tin, tellurium, copper, and molybdenum. The resin was selective toward molybdenum at pH 3-4. The resin was used for the adsorption/collection of molybdenum in river water and seawater samples. Concentrations in river water samples were 0.84 and 0.95 ppb Mo (ng g-1) and in seawater about 9 ppb
Sabarudin, A., Oshima, M., Noguchi, O., and Motomizu, S., Functionalization of chitosan with 3-nitro-4-amino benzoic acid moiety and its application to the collection/concentration of molybdenum in environmental water samples, Talanta, 2007, 73, 831-837.
Molybdenum determination in drinking waters ― novel on-line pre-concentration method for inorganic molybdenum
A minicolumn was filled with ethyl vinyl acetate turnings
as the adsorbent. Molybdenum was retained on the minicolumn without further
complexation; sample throughput was 12 samples per hour; precision for six
replicate measurements of a solution containing 20 mu g L-1 Mo was 3.5%
relative standard deviation; limit of detection was 0.04 mu g L-1.
Escudero, L., Gil, R. A., Gasquez, J. A., Olsina, R. A., and Martinez, L. D., Trace molybdenum determination in drinking waters by USN-ICP-OES after solid phase extraction on ethyl vinyl acetate turnings-packed minicolumn, Atomic Spectroscopy, 2008, 29, 21-26.
Molybdenum in water
| Source |
Concentration /microg/l |
| Sweden, treated [1] |
3 |
| Sweden, raw [1] |
4 |
| Sweden - study of several towns [1] |
1.29 |
| Sweden-Summer [1] |
0.11 - 0.15 |
| Sweden-Winter [1] |
0.30 - 0.60 |
| Czechoslovakia [2,3] |
0.00 - 0.62 |
| Czechoslovakia - mineral spring [2,3] |
2.31 - 3.33 |
| Colorado - CLIMAX ore mine [4] |
200 - 400 |
| Colorado - groundwater [4] |
25,000 |
| Morava River basin [5] |
0.0102, 0.0014, 0.0011 kg/ha/year |
[1] Boström, H., and Wester, P. O., Acta Med. Scand., 1967, 181, 465.
[2] Osmolovakaja, E. V., Gig. Sanit., 1967, 32, 98.
[3] Nevoral, V., Fys. Vestnik , 1978, 53, 23.
[4] Chapell, W. R., Progress Report Univ. Colorado, Denver, 1974, 167.
[5] Kockova, E., Palat, M., Betusova, M., Bioelements And Heavy-Metals In Dry And Wet Depositions At Some Localities In The Morava River Basin, Water Science And Technology,1996, 33, 277-283.
Natural waters low in Mo < 2- 3 microg/l
Near Mo mining areas surface water 0.2 – 0.4 mg/l
groundwater 25 mg/l.
In streams < 6mg/l.
Chappell, W.B., Peterson, K.K., eds. , Molybdenum in the Environment Vol. 1 and Vol. 2, New York, Elsevier, 1977.
Mo in water – effect of pH
Elevated pH increases solubility and leachability of Mo in water.
Acidic conditions decrease the transfer of Mo from soil to water. Acidic groundwater in contact with soil containing 800 mg Mo/kg has < 0.2 mg Mo/l.
Runnells, D.D., Kaback, D.S., and Thurman, E.M., Geochemistry and sampling of molybdenum in sediments, soils and plants in Colorado in Chappell, W.B., Peterson, K.K., eds. , Molybdenum in the Environment Vol. 2, New York, Elsevier, 1977.
Mo in tap water and natural water
Mo(VI) in environmental samples; e.g., soil, natural water and indoor airborne particulate has been determined by cathodic linear sweep stripping voltammetry. Molybdenum species are concentrated on the hanging mercury drop electrode (HMDE) using mixtures of nitrate and phosphate as supporting electrolytes. The detection limit found was 1 x 10-8 M using 120 s as accumulation time. The precision ( relative standard deviation) was 1.4% with five replicates at 1 x 10-6 M Mo(VI).The data refer to Mo concentrations in potable water in Egypt:
range of values from different souces 0.48 - 9.58 microg l-1
tap water (Nile) 3.93
tap water (well) 5.76
natural water (Nile) after filtration 8.15
Ali, A.M.M., Ghandour, M. A., El Shatoury, S. A., and Ahmed, S. M., Adsorptive cathodic stripping voltammetric determination of molybdenum in synthetic solutions and environmental samples, Electroanalysis, 2000, 12, 155-158.
Mo in natural water Malinovsky, D., Hammarlund, D., Ilyashuk, B., Martinsson, O., and Gelting, J., Variations in the isotopic composition of molybdenum in freshwater lake systems, Chemical Geology, 2007, 236, 181-198.
A liquid core waveguide has been used to extend the sensitivity of conventional absorbance spectroscopy for chromium(VI) and molybdenum(VI). Analysis of Cr(VI) and Mo(VI) concentrations in water samples with a 5.0 m pathlength liquid core waveguide made of Teflon AF-2400 provided a detection limit for Cr 0.2 and for Mo 0.6 nM. No preconcentration is required in this analysis.
Concentrations of Mo(VI)/nM:
Surface seawater (Gulf of Mexico), 98
Rain water, <0.5
Spring waters (bottled)
Brand # 1,40.0, 39.2
# 2, 41.4, 43.5
# 3, 5,2, 6.8
# 4, 6.0, 5.7
# 5, 260 , 273
Yao, W.S., Byrne, R.H., Determination of trace chromium(VI) and molybdenum(VI) innatural and bottled mineral waters using long pathlengthabsorbance spectroscopy,Talanta, 1999,48,2,277-282.
The detection limit of molybdate in natural waters by coprecipitation and neutron activation analysis was about 1 ng L-1.
Sun, Y.C., Yang, J.Y., Tzeng, S.R., Rapid determination of molybdate in natural waters by coprecipitation and neutron activation analysis, Analyst, 1999, 124, 3, 421-424.
Eastern Sierra Nevada rivers
Concentration ranges were:
boron 2 mu mol/kg in the upper reaches of the Truckee River to 1,200 mu mol/kg in Pyramid Lake
molybdenum 12 nmol/kg to 3,200 nmol/kg (Walker Lake)
vanadium 9 nmol/kg to 470 nmol/kg
W 0.8 nmol/kg to 1,030 nmol/kg.
The ‘high concentrations’ of these oxyanion-forming trace elements in the rivers reflects the relative stability of the oxyanions in the alkaline, well oxygenated river and lake waters.
Johannesson,K.H., Lyons, B., Graham, E.Y., Welch, K.A., Oxyanion concentrations in eastern Sierra Nevada rivers - 3. Boron, molybdenum, vanadium, and tungsten Aquatic Geochemistry, 2000,6,19-46.
Houston Ship Channel
The molybdenum concentration in the surface water of the Houston ShipChannel determined using inductively coupled plasma/massspectrometry was mu g/L 6.66.
Saleh, M.A., Wilson, B.L., Analysis of metal pollutants in the Houston Ship Channel byinductively coupled plasma/mass spectrometry, Ecotoxicology And Environmental Safety, 1999,44,1,113-117.
Mo in natural water
Eastern Sierra Nevada rivers
Mo varied from a low of about 12 nmol/kg to a high of 3,200 nmol/kg (Walker Lake).The high concentrations of these oxyanion-forming trace elements in the rivers reflects the relative stability of these oxyanions (e.g., MoO42-, HVO42-, WO42-, B(OH)(3), and/or B(OH)(4)(-)) in the alkaline, well oxygenated river and lake waters, weathering of rocks/regolith with high concentrations of these elements. In the case of Mo, V, and W, each exhibited relatively conservative behaviour in the upper, oxygenated reaches of all three rivers. Reductive processes occurring in the low flow to stagnant reaches of each river (due to a prolonged drought) could have led to removal of Mo, V, and W from solution as coprecipitates with Fe monosulfides, or via sorption to Fe oxides/oxyhydroxides and/or organic matter.
Johannesson, K.H., Lyons, W. B., Graham, E. Y., and Welch, K. A., Oxyanion concentrations in eastern Sierra Nevada rivers - 3. Boron, molybdenum, vanadium, and tungsten, Aquatic Geochemistry, 2000, 6, 19-46.
UK rivers
A series of papers published in Science of the Total Environment, 2000, 251 report data on the water quality of rivers draining into the North Sea from the eastern UK using core information collected within the Land-Ocean Interaction Study (LOIS) and a companion study by the Institute of Hydrology. The analysis is based on weekly monitoring for periods from 1993 to 1999.
Neal, C. and Robson, A. J., A summary of river water quality data collected within the Land-Ocean Interaction Study: core data for eastern UK rivers draining to the North Sea, , 585-665.
In the River Trent acid available Mo in particulates in microg/l was: non tidal, 0.05; freshwater tidal, 0.06 to 0.02 at different locations. Dissolved Mo was 6.51 - 9.28.
Jarvie, H.P., Neal, C., Burton, J. D., and Tappin, A. D., Patterns in trace element chemistry in the freshwater tidal reaches of the River Trent, Science of the Total Environment, 2000, 251, 317-333.
In the River Thames 34 km downstream of Oxford average dissolved Mo was 35.1 microg/l with a maximum of 1588 microg/l (due probably to point source pollutant inputs from light industry).
Neal, C., Williams, R. J., Neal, M., Bhardwaj, L. C., Wickham, H., Harrow, M., and Hill, L. K., The water quality of the River Thames at a rural site downstream of Oxford, Science of the Total Environment, 2000, 251, 441-457.
Mo in water treatment residuals
Molybdenum (Mo) content was determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES) to evaluate suitability for land application under state regulatory policies that limit Mo to 18 mg kg(-1). Samples of of water treatment residuals were collected from 32 Pennsylvania facilities that employ aluminium salts, ferric chloride, and/or polymers for coagulation. Mean Mo content of all samples was 3.1 mg kg-1.
The water treatment residuals from plants using ferric chloride as a coagulant averaged 5.6 mg Mo kg-1
1.6 mg Mo kg-1 for utilities using alum.
Differences were related to coagulant purity: Mo content in liquid ferric chloride nas 10.0 mg L-1 but below detection by ICP-AES for alum.
The mean Cu to Mo ratio in these water treatment residuals was >100, well above the minimum dietary ratio (2:1) considered protective of grazing animals
Elliott, H.A. and Taylor, M., Molybdenum content of water treatment residuals, Journal of Environmental Quality, 2000, 29, 1835-1839.
Metal contamination of freshwater ecosystems is increasingly prevalent due to anthropogenic activities such as metal smelting and fossil fuel combustion. Cladoceran diapausing eggs (ephippia), which are abundant in nature and accumulate maternally derived metals, can be used to measure historical variations in biologically relevant metals that derive from the water column ( water, diet). Metals were incorporated into ephippia with little contamination from the sediment matrix. Some metals associated with urban sources (Cd, Cr, Mo) were preferentially concentrated in ephippia, whereas concentrations of other metals indicating landscape erosion (Al, Ca, Fe, Mn) exhibited greater concentrations in bulk sediments than in diapausing eggs. Past variation in the metal content of ephippia provided a unique history of food web exposure to metals in the water column
Wyn, B., Sweetman, J. N., Leavitt, P. R., and Donald, D. B., Historical metal concentrations in lacustrine food webs revealed using fossil ephippia from Daphnia, Ecological Applications, 2007, 17, 754-764.
Seawater
Mo in seawater collected from Salvador City, Bahia, Brazil. was determined by using atomic emission spectrometry with inductively coupled plasma (ICP-AES).after preconcentration (100) of Mo on activated carbon. Mo concentrations in seawater from 4 locations were: 7.9 +/- 0.9, 8.5 +/- 0.5, 8.0 +/- 0.7, 8.4 +/- 0.1 microg l-1.
dos Santos, H.C., Korn, M. G. A., and Ferreira, S. L. C., Enrichment and determination of molybdenum in geological samples and seawater by ICP-AES using calmagite and activated carbon, Analytica Chimica Acta, 2001, 426, 79-84.
Mo in snow and ice
Co, Cr, Mo, and Sb have been measured by DF-ICP-MS-MCN (double focusing inductively coupled plasma mass spectrometry with microconcentric nebulizer) in various sections of a 140 m snow/ice core drilled at a high altitude location near the summit of Mont Blanc in the French-Italian Alps. The bottom of the core is older than 200 years. Concentrations in recent snow are higher than concentrations in ice dated from before the middle of the 19th century Mo shows the greatest increase (x16), followed by Sb (x5), and Co and Cr (x2-3) For recent snow, contribution from oil and coal combustion is the dominating source for Co, Mo,and Sb. For Cr, on the other hand, the most important contribution is from iron, steel, and ferroalloy industries.
Mo 0.2 - 50 pg/g
Co 26 - 433 pg/g
Cr 8 - 469pg/g
Sb 0.2 - 109 pg/g
VandeVelde, K., Ferrari, C., Barbante, C., Moret, I., Bellomi, T., Hong, S.M., Boutron, C., A 200 year record of atmospheric cobalt, chromium, molybdenum,and antimony in high altitude alpine firn and ice, Environmental Science & Technology, 1999,33,3495-3501
Molybdenum in irrigation waters
| Irrigation guideline |
50 microgMo/l |
rarely exceeded |
| aquatic life protection chronic criterion |
19 microgMo/l |
75% exceeded |