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The major pool of manganese in soils originates from crustal sources, with other sources including direct atmospheric deposition, wash-off from plant and other surfaces, leaching from plant tissues, and the shedding or excretion of materials such as leaves, dead plant and animal excrement.

Natura (“ background”) levels of total manganese in soils range from >1-4.000 mg/kg dry weight; with mean values around 300-600 mg/kg dry weight.

Manganese concentration in air tend to be lowest in remote location (about 0.5-14 ng/ m3) on average, higher in rural areas (40ng/m3on average), and still higher in urban areas (about 65-166 ng/m3on average). Manganese concentrations in air tend to be highest in source-dominant areas, where values can reach 8,000ng/m3). Annual averages of manganese concentrations may rise to 200-300ng/m3 in air near foundries and to over 500 ng/m3 in air near ferro-and silico-manganese industries

 

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

 

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). Transition 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. Chemical factors controlling sedimentary manganese cycling are the oxygen content of the overlying water, the penetration of oxygen into the sediments, the 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 variables: pH and redox potential.

 

Manganese in water

 

Concentrations of dissolved manganese in natural water that are essential free of anthropogenic inputs can range from 10 to 10.000µg/litre. However, dissolved manganese concentrations in natural surface waters rarely exceed 1.000µg/litreand are usually less than 200µg/litre Manganese in aquatic and terrestrial plants

 

Concentrations in seaweed range from 130-750 mg/kg dry weight, whereas concentrations in shellfish range from 3-660 mg/kg/dry weight; higher concentrations in shellfish are associated with manganese- rich sediment. Concentrations of manganese found in tissue of marine and freshwater fish tend to range from 0.2 to 19 mg/kg dry weight. Higher manganese concentrations- above 100 mg/kg dry weight-have been reported for fish in polluted surface waters.

 

Manganese in plants and wildlife

 

Concentrations of manganese in terrestrial plants tend to range from 20 to 500 mg/kg dry weight. Members of the Ericaceae family, which includes blueberries, are regarded as manganese accumulators. There are numerous reports of foliar manganese levels in excess of 2,000-4,000 mg/kg.

Mean manganese concentrations in bird´s eggs from a variety of geographical areas range from 1 to5 mg/kg dry weight, mean liver concentrations range from 3 to 11 mg/kg dry weight, and mean feather concentrations reach from 0.3 to 40 mg/kg dry weight. Mean manganese concentrations of up to 17 mg/kg dry weight have been found in tissues (liver, kidney and whole body) from a variety of reptiles and wild mammals.

 

Manganese is an essential nutrient for micro-organisms, plants and animals. Nutritional manganese requirements for terrestrial plants are around 10 - 50 mg/kg tissue. Critical nutritional levers vary widely between species and among cultivars of a species. Calcareous soils, especially those with poor drainage and high organic matter, are the types of soils that produce manganese deficient plants. Symptoms of manganese plants vary widely with species and include marginal chloroses, necrotic lesions and distorted development of the leaves. Toxic manganese concentrations in crop plant tissue vary widely, with critical values ranging from 100 to 5,000 mg/kg. Manganese toxicity is a major factor limiting crop growth on acidic, poorly drained, or steam-sterilized mineral soils. There is a wide range of variation in tolerance to manganese between and within plant species.

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