Call us toll-free

Quick academic help

Don't let the stress of school get you down! Have your essay written by a professional writer before the deadline arrives.

Calculate the price

Pages:

275 Words

$19,50

Blending hypothesis explanation free

Manganese can be released to water by discharge from industrial facilities or as leachate from landfills and soil (US EPA, 1979, 1984; Francis & White, 1987; TRI91, 1993). Sea disposal of mine tailings and liquor is another source of manganese to the marine environment, particularly in tropical areas (Florence et al., 1994). Nriagu & Pacyna (1988) estimated that total worldwide anthropogenic inputs of manganese to aquatic ecosystems during 1983 ranged from 109 000 to 414 000 tonnes, with the predominant sources being domestic wastewater and sewage sludge disposal. In the USA, reported industrial discharges of manganese in 1991 ranged from 0 to 17.2 tonnes for surface water, from 0 to 57.3 tonnes for transfers to public sewage, and from 0 to 0.114 tonnes for underground injection (TRI91, 1993). An estimated total of 58.6 tonnes, or 1% of the total environmental release of manganese in the USA, was discharged to water in 1991 (TRI91, 1993). In 1996, the estimated release of manganese to water was 870 tonnes (TRI96, 1998).

Looking for online definition of Blending hypothesis in the Medical Dictionary

Crustal rock is a major source of manganese found in the atmosphere. Ocean spray, forest fires, vegetation, and volcanic activity are other major natural sources of manganese in the atmosphere (Schroeder et al., 1987; Stokes et al., 1988). Stokes et al. (1988) estimated that two-thirds of manganese air emissions were from natural sources. Atmospheric particulate matter collected in the Antarctic indicated that manganese was derived from either crustal weathering or the ocean (Zoller et al., 1974). Air erosion of dusts and soils is also an important atmospheric source of manganese, but no quantitative estimates of manganese release to air from this source were identified (US EPA, 1984). An important source of dissolved manganese is anaerobic environments where particulate manganese oxides are reduced, such as some soils and sediments, wetlands, and the anaerobic hypolimnia of lakes and fjords. Other possible sources include the direct reduction of particulate manganese oxides in aerobic environments by organics, with or without ultraviolet light, the natural weathering of Mn(II)-containing minerals, and acid drainage and other acidic environments. The major pool of manganese in soils originates from crustal sources. Addition of manganese to soils can also result from direct atmospheric deposition, wash-off from plant and other surfaces, leaching from plant tissues, and the shedding or excretion of material such as leaves, dead plant and animal material, and animal excrement (Stokes et al., 1988).

Related to blending inheritance: Particulate ..

The major anthropogenic sources of environmental manganese include municipal wastewater discharges, sewage sludge, mining and mineral processing (particularly nickel), emissions from alloy, steel, and iron production, combustion of fossil fuels, and, to a much lesser extent, emissions from the combustion of fuel additives.

Meneses et al. (1999) and Llobet et al. (2002) used ICP mass spectrometry with a detection limit of 0.02 mg/kg for soil and herbage. Pandey et al. (1998) used a sequential ICP optical emission spectrometer with an ultrasonic nebulizer for atmospheric particulates at a detection limit of 0.001 µg/litre, whereas ICP with atomic emission spectrophotometry was used for atmospheric particulates (Brewer & Belzer, 2001; Espinosa et al., 2001), sediment (Leivuori, 1998; Leivuori & Vallius, 1998), shellfish (Blackmore et al., 1998; Blackmore, 1999; Rainbow & Blackmore, 2001), feathers (Connell et al., 2002), and liver tissue (Mason & Stephenson, 2001).

Great Red Comet-Earth Science Chronicles

The manganese content in ore produced worldwide was estimated to be 8.8 million tonnes in 1986. Production levels of manganese ore and its total manganese metal content remained nearly the same through 1990 (US Department of the Interior, 1993). Levels of ore produced worldwide in 1995, 1996, and 1997 declined slightly, with total manganese metal content declining proportionately to 8.0, 8.1, and 7.7 million tonnes, respectively (US Department of the Interior, 1996, 1998). Sites of substantial workable manganese–iron deposits include the former USSR, South and North Africa, South America, India, and China (Schiele, 1991). Most manganese is mined in open-pit or shallow mines (NAS, 1973). Although modern steelmaking technologies call for lower unit consumption of manganese, worldwide demand for steel is projected to increase moderately in the future, particularly in developing countries (US Department of the Interior, 1995, 1998). The demand for manganese in other industries (e.g., dry-cell battery manufacturing) might also increase, but the overall effect of these other uses on global trends in manganese production and use is minor (EM, 1993; US Department of the Interior, 1995, 1998).

The main anthropogenic sources of manganese release to air are industrial emissions (such as ferroalloy production and iron and steel foundries, power plants, and coke ovens), combustion of fossil fuels, and re-entrainment of manganese-containing soils (Lioy, 1983; US EPA, 1983, 1984, 1985a,b; Ruijten et al., 1994; ATSDR, 2000). Problems with air pollution — especially dust and smoke containing manganese dioxide and manganese tetroxide — arise during the mining, crushing, and smelting of ores as well as during steel production (Schiele, 1991). Approximately 2 tonnes of manganese ore are required to make 1 tonne of ferromanganese alloy (NAS, 1973). Steel emissions were found to be the predominant source of manganese in urban particulate matter (Sweet et al., 1993). Manganese can also be released to the air during other anthropogenic processes, such as welding and fungicide application (Ferraz et al., 1988; MAK, 1994; Ruijten et al., 1994). Nriagu & Pacyna (1988) estimated that total worldwide emissions of manganese in 1983 ranged from 10 560 to 65 970 tonnes, with the predominant sources being coal combustion, secondary non-ferrous metal production, and sewage sludge incineration. Total emissions to air from anthropogenic sources in the USA were estimated to be 16 400 tonnes in 1978, with about 80% (13 200 tonnes) from industrial facilities and 20% (3200 tonnes) from fossil fuel combustion (US EPA, 1983). Air emissions by US industrial sources reportable to the Toxics Release Inventory (TRI) for 1987 totalled 1200 tonnes (TRI87, 1989). In 1991, air emissions from TRI facilities in the USA ranged from 0 to 74 tonnes, with several US states reporting no emissions (TRI91, 1993). Estimated releases of manganese to air in 1996 were 4000 tonnes, representing 15% of total environmental releases (TRI96, 1998). Figures in Table 2 (see section 6) show decreasing emissions of manganese to air in the USA as a result of air pollution control.

Order now
  • UNMATCHED QUALITY

    As soon as we have completed your work, it will be proofread and given a thorough scan for plagiarism.

  • STRICT PRIVACY

    Our clients' personal information is kept confidential, so rest assured that no one will find out about our cooperation.

  • COMPLETE ORIGINALITY

    We write everything from scratch. You'll be sure to receive a plagiarism-free paper every time you place an order.

  • ON-TIME DELIVERY

    We will complete your paper on time, giving you total peace of mind with every assignment you entrust us with.

  • FREE CORRECTIONS

    Want something changed in your paper? Request as many revisions as you want until you're completely satisfied with the outcome.

  • 24/7 SUPPORT

    We're always here to help you solve any possible issue. Feel free to give us a call or write a message in chat.

Order now

Comprehensive news and events on our changing planet

Most toxicity tests have been carried out using ionic manganese. Little is known about the aquatic toxicity of colloidal, particulate, and complexed manganese; in general, however, toxicities of metals bound into these forms are assumed to be less than those of the aquo-ionic forms. For algae and protozoa, there is a wide range of toxicity values; the most sensitive species appear to be the marine diatom , with a 5-day EC50, based on growth inhibition, of 1.5 mg/litre, and a freshwater alga , with a 12-day EC50, based on total chlorophyll reduction, of 1.9 mg/litre. Tests on aquatic invertebrates reveal 48-h LC50/EC50 values ranging from 0.8 mg/litre () to 1389 mg/litre (), the lowest LC50 being observed under soft water conditions (25 mg calcium carbonate/litre). A significant reduction in survival and hatching of yellow crab () embryos at >0.01 mg manganese/litre was found in 7-day tests in seawater. For fish, 96-h LC50s range from 2.4 mg manganese/litre for coho salmon () to 3350 mg/litre for Indian catfish (), with the lowest LC50 values obtained under soft water conditions (25 mg calcium carbonate/litre). Significant embryonic mortality was observed in rainbow trout () eggs exposed to 1 mg manganese sulfate/litre for 29 days. A single embryo-larval test with a 7-day LC50 of 1.4 mg manganese/litre was identified for amphibians. Acute toxicity in aquatic invertebrates and fish decreased with increasing water hardness; the addition of chelating agents can reduce the toxicity of manganese. There is evidence that manganese can protect organisms against the effects of more toxic metals.

Environment International - Journal - Elsevier

Combustion of MMT leads to the emission of manganese phosphates and manganese sulfate, with manganese oxides such as manganese tetroxide a minor component (NICNAS, 2003). The size of particles emitted to the atmosphere varies from 0.1 to 0.45 µm (Waldron, 1980). Combustion products of MMT also include manganese phosphate and manganese sulfide (Zayed et al., 1999; Zayed, 2001). One of the principal sources of inorganic manganese as a pollutant in the urban atmosphere is the combustion of MMT, particularly in areas of high traffic density (Sierra et al., 1998). MMT was used as a gasoline additive in the USA for a number of years, resulting in manganese emissions. Davis et al. (1988) found that motor vehicles made a significant contribution to levels of airborne manganese in areas such as southern California (around 40% of total airborne manganese) compared with, for example, central and northern California, where the addition of manganese to gasoline was much lower. According to a statistical model of source apportionment, the calculated average vehicular contribution of manganese in southern California was about 13 ng/m3, around 4 times the value calculated for both central and northern California.

Environmental Health and Toxicology (EHT)

Manganese is released to air mainly as particulate matter, and the fate and transport of the particles depend on their size and density and on wind speed and direction. Some manganese compounds are readily soluble in water. Manganese exists in the aquatic environment in two main forms: Mn(II) and Mn(IV). Movement between these two forms occurs via oxidation and reduction reactions that may be abiotic or microbially mediated. The environmental chemistry of manganese is largely governed by pH and redox conditions; Mn(II) dominates at lower pH and redox potential, with an increasing proportion of colloidal manganese oxyhydroxides above pH 5.5 in non-dystrophic waters. Primary chemical factors controlling sedimentary manganese cycling are the oxygen content of the overlying water, the penetration of oxygen into the sediments, and benthic organic carbon supply. Manganese in soil can migrate as particulate matter to air or water, or soluble manganese compounds can be leached from the soil. In soils, manganese solubility is determined by two major variables: pH and redox potential.

Order now
  • You submit your order instructions

  • We assign an appropriate expert

  • The expert takes care of your task

  • We send it to you upon completion

Order now
  • 37 684

    Delivered orders

  • 763

    Professional writers

  • 311

    Writers online

  • 4.8/5

    Average quality score

Order now
  • Kim

    "I have always been impressed by the quick turnaround and your thoroughness. Easily the most professional essay writing service on the web."

  • Paul

    "Your assistance and the first class service is much appreciated. My essay reads so well and without your help I'm sure I would have been marked down again on grammar and syntax."

  • Ellen

    "Thanks again for your excellent work with my assignments. No doubts you're true experts at what you do and very approachable."

  • Joyce

    "Very professional, cheap and friendly service. Thanks for writing two important essays for me, I wouldn't have written it myself because of the tight deadline."

  • Albert

    "Thanks for your cautious eye, attention to detail and overall superb service. Thanks to you, now I am confident that I can submit my term paper on time."

  • Mary

    "Thank you for the GREAT work you have done. Just wanted to tell that I'm very happy with my essay and will get back with more assignments soon."

Ready to tackle your homework?

Place an order