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.
Trace metal pollution of Tsurumi River, Yokohama, Japan
the trace metal pollution of water and sediments downstream of Tsurumi River, Yokohama, Japan was studied. Twenty samples of water and sediments were collected from the river starting from Tokyo bay side up to the junction point of the Yagami River. The mean concentrations of chromium, cupper and nickel in water greatly exceeded (>100 times) the surface water standard. The concentration of molybdenum and lead was also higher than standard values; iron and manganese were lower than that of surface water standard. The mean concentration of zinc, cupper, cadmium, lead, chromium, vanadium, bromine and iodine was 381.1, 133.0, 1.0, 40.8, 102.9, 162.0, 71.5 and 10.6 microg/g sediments greatly exceeded the average worldwide shale concentrations and average Japanese river sediment values. Mean concentrations of arsenic, nickel and strontium were 11.0, 36.6 and 164.6 microg/g sediments, lower than the average shale value. Other analyzed trace metals, including barium, zirconium, rubidium, yttrium, tin, antimony, cesium, lanthanum, cerium, praseodymium and neodymium were detected in river sediments; their concentration was close to the Japan's river sediment average values. Pollution load index (PLI) values of the sites were from 1.24 to 7.65 showing that the river sediments are polluted. The PLI value of the area was high (6.53) as the concentration of trace metals like zinc, cupper, cadmium, lead and chromium were very high and were the major pollutants
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Mohiuddin, K. M., Zakir, H. M., Otomo, K., Sharmin, S., and Shikazono, N., Geochemical distribution of trace metal pollutants in water and sediments of downstream of an urban river, International Journal of Environmental Science and Technology, 2010, 7, 17-28.
Water Sediment-Water Interface
Laguna Caren is a small shallow freshwater system located 20 km from downtown Santiago, Chile. Diffusive fluxes through the sediment-water interface were measured by diffusive dialysis. Dissolved Fe and Mn showed decreasing concentrations from -6.0 cm to 0.0 cm, while concentrations of Mo and Sb increased at this depth. Soluble species of Fe(II) and Mn are available by diffusive transport to the overlying waters, whereas Mo and Sb species are not available in this zone. The fluxes were (in pmol cm-2 s-1): Fe(II): 0.05; Mn: 0.28; Mo: -1.2 x 10-4; Sb: -3.9 x 10-4
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Pizarro, J., Rubio, M. A., and Matta, A., Difussion of Fe, Mn, Mo and Sb in the Sediment-Water Interface of A Shallow Lake, Laguna Caren, Santiago (Chile), Fresenius Environmental Bulletin, 2009, 18, 2336-2344.
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.
Firdaus, M. L., Norisuye, K., Nakagawa, Y., Nakatsuka, S., and Sohrin, Y., Dissolved and labile particulate Zr, Hf, Nb, Ta, Mo and W in the western North Pacific Ocean, Journal of Oceanography, 2008, 64, 247-257.
Isotopic Analysis of molybdenum in seawater
The ocean is a reservoir of molybdenum. The natural isotopic variation of molybdenum tells us about the geochemical circulation of molybdenum. A preconcentration technique using 8-hydroxyquinoline bonded covalently to a vinyl polymer resin (TSK-8HQ) was developed and enabled molybdenum in seawater to be separated from matrix elements, alkali, alkaline earth, and transition metals. An accurate ratio for every pair of stable molybdenum isotopes was then determined using multiple collector-inductively coupled plasma mass spectrometiy (MC-ICPMS),.
Four kinds of seawater samples were analysed. The molybdenum compositions were constant among them, with average delta(98)/molybdenum-95 and delta(92)/molybdenum-98 values of 2.45 ± 0.11 and -4.94 ± 0.09 parts per thousand (± 2 SD). Seawater is more enriched in heavy molybdenum isotopes than previously reported.
Nakagawa, Y., Firdaus, M. L., Norisuye, K., Sohrin, Y., Irisawa, K., and Hirata, T., Precise Isotopic Analysis of Mo in Seawater Using Multiple Collector-Inductively Coupled Mass Spectrometry Coupled with a Chelating Resin Column Preconcentration Method, Analytical Chemistry, 2008, 80, 9213-9219.
Water sea Mo isotopic composition in sedimentsChesapeake Bay
Manganese oxyhydroxides (MnOx) are a major sink for molybdate
in oxygenated seawater. Molybdate adsorbed onto MnOx is isotopically light relative to dissolved MoO42− in the source solution
Fractionation of molybdenum isotopes during adsorption
to MnOx is primarily responsible for the heavy isotopic composition of
seawater Dissolved molybdenum in seawater present almost entirely as MoO42− has an isotopic composition (δ98Mo) as much as two parts per thousand (2‰) heavier than molybdenum delivered from continental sources, such as clastic sediments and igneous rocks.
However, authigenic molybdenum deposited in suboxic environments is also 1 to 2‰ lighter than seawater. Since MnOx is not deposited under suboxic conditions, at least one additional process for selectively removing light molybdenum isotopes from seawater must exist. A second process that might influence δ98Mo values in sediments from suboxic zones is fractionation during thiomolybdate formation.
This process probably contributes to the modern, heavy δ98Mo value
of seawater, and will have contributed to past seawater δ98Mo values.
Molybdenum isotope data for sediments and waters of the seasonally anoxic Chesapeake Bay, and its primary tributary, the Susquehanna River were measured.
Scheiderich, K., Helz, G. R., and Walker, R. J., Century-long record of Mo isotopic composition in sediments of a seasonally anoxic estuary (Chesapeake Bay), Earth and Planetary Science Letters, 2010, 289, 189-197.
[Background:
Authigenic : descriptive of rock constituents and minerals which are formed or generated in the location where they are found;materials usually are formed subsequent to deposition, but might be formed at the time of deposition.
http://www.spwla.org/library_info/glossary/reference/glossa/glossa.htm
Stable molybdenum isotopes as tracers of paleoredox conditions in the oceans
http://www.geol.umd.edu/faculty/WALKER/walker_homepage/paleoredox.htm
Quantum mechanical calculation of the binding differences of different molybdenum isotopes.
Isotopic fractionation equilibrium constants for exchange of light and heavy molybdenum isotopes between the molybdate species dominant in seawater and a range of oxidic and sulfidic molybdenum species were calculated from the difference in the vibrational, rotational and translational contributions to the free energy in the gas phase for the gas-phase reaction involving different isotopomers with different molybdenum isotopes. This requires calculationofthe equilibrium geometries and vibrational freqencies for all the species involved. The different isotopomers of these species will have the same force constants within the standard Born-Oppenheimer approximation, but their vibrational frequencies will be different for those vibrations involving molybdenum motion since such vibrational normal modes will have different reduced masses.
J. A. Tossell, Geochimica et Cosmochimica Acta, 69, 2981–2993, 2005: Calculating the partitioning of the isotopes of Mo between oxidic and sulfidic species in aqueous solution].
Sediments metal distribution Gulf of Finland
This study is the first of its kind, as a systematic mapping of the whole coastal area of the Finnish part of the Gulf of Finland. This area was sampled with a relatively even spacing and the distributions of heavy metals and arsenic in the modem soft surface sediments are presented as circular symbol maps. Data on cobalt and molybdenum are reported for the first time from a total digestion from samples from this area. The sediments are strongly enriched by some of the studied elements due to the anthropogenic load, while others are only moderately present. High or relatively high levels of cadmium, copper, mercury, molybdenum, and zinc were found in the easternmost part of the study area
Vallius, H., Heavy metal distribution in the modern soft surface sediments off the Finnish coast of the Gulf of Finland, Baltica, 2009, 22, 65-76.
Water sea molybdenum enrichment in scallop shells in temperate coastal environments
Skeletal molybdenum/calcium ([Mo]/[Ca])(shell) ratios were examined in shells of the Great Scallop Pecten maximus collected in temperate coastal environments of Western Europe (42 to 49 degrees N). Variations of ([Mo]/[Ca])(shell) ratios were significant and reproducible for scallops from the same population, from different years (1998-2004) and temperate coastal locations (NW France). Both the intense monitoring survey in 2000 and over the 7-year period indicates that the ([Mo]/[Ca])(shell) maximum is directly influenced by spring changes of environmental conditions at the sediment water interface, occurring subsequent to the intense and periodic spring bloom. Spring maxima of ([Mo]/[Ca])(shell) ratios are closely correlated to the extent of silicic acid and nitrate depletion in seawater between winter and late spring that reflects diatom uptake and productivity in the Bay of Brest. The [Mo]/[Ca])(shell) records thus reveal unexpected biogeochemical cycles of Mo influenced by coastal spring productivity, faithfully recorded in scallop shells
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Barats, A., Amouroux, D., Pecheyran, C., Chauvaud, L., Thebault, J., and Donard, O. F. X., Spring molybdenum enrichment in scallop shells: a potential tracer of diatom productivity in temperate coastal environments (Brittany, NW France), Biogeosciences, 2010, 7, 233-245.
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 |
Seiler, R.L., Synthesis of data from studies by the national irrigation water-quality program, Water Resources Bulletin, 1996, 32, 1233-1245.
Molybdate in ground water – wetlands
The role of wetlands in the retention or release of trace elements to streams was investigated. Temporal and spatial patterns of concentrations of trace elements were determined by ICP-MS and geochemical drivers in five streams and wetland rivulets draining natural wetlands in a northern Wisconsin watershed and in their groundwater sources (terrestrial recharge, lake recharge, and older lake recharge). The low levels Cu and Mo in the rivulets were attributed to redox cycling and precipitation and dissolution reactions involving Fe and Mn.Variance in Fe, Mn and the metal oxy-anions was associated with redox cycling and adsorption reactions in the wetland sediments
A wetland is an area of land consisting of soil that is saturated with moisture, such as a swamp, marsh, or bog. Some of the time water saturates the soil; the result is a hydric soil, one characterized by an absence of free oxygen some or all of the time, and therefore called a "reducing environment. (Wikipedia).
Kerr, S. C., Shafer, M. M., Overdier, J., and Armstrong, D. E., Hydrologic and biogeochemical controls on trace element export from northern Wisconsin wetlands, Biogeochemistry, 2008, 89, 273-294.
Mo in water treatment residuals - wetlands
Biomass of Phragmites australis growing in four constructed wetlands with horizontal subsurface flow (HF CWs) designed for treatment of municipal sewage in the Czech Republic have been analyzed for 19 trace elements. The biomass was harvested during the peak standing crop in early September and divided into stems, leaves, flowers, roots and rhizomes. Concentrations of elements in both aboveground and belowground plant tissues were similar to those found in plants growing in natural stands. The highest concentrations were Al, Fe, Mn, Ba and Zn and the lowest concentrations were Hg, U and Cd. Concentrations decreased roots > rhizomes > leaves > stems. The root/leaf ratio averaged 70 and varied between 1.4 for molybdenum and 392 for cobalt. The belowground/aboveground concentration ratio ranged between 0.9 and 69.5 with an average value of 19. Due to average aboveground/belowground biomass ratio > 1, the belowground/aboveground standing stock ratios were lower with six elements (Ba, Zn, Se, Hg, Mo, and Mn) having this ratio < 1.
