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Manganese is a natural occurring element that is found in rock, soil, and water. It exists in the environment only in its insoluble compounds, especially as oxides or carbonates, or as mixed in form of oxides/carbonates. It is ubiquitous in the environment and comprises about 0.1% of the Earth crust. Crustal rock is a major source of manganese found in the atmosphere. Ocean spray, forest fires, vegetation, and volcanic activity are other major natural atmospheric sources of manganese. Important sources of dissolved manganese are anaerobic environments where particulate manganese oxides are reduced, the direct reduction of particulate manganese oxides in aerobic environments, the natural weathering of Mn(II)-containing minerals, and acidic environments. Manganese exists in the aquatic environment in two main forms: Mn(II) and Mn(IV). The Mn(II) exist as Hexahydrate. 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.

 

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.

Manganese concentration in air tend to be lowest in remote location (about 0.5-14 ng/ m³) on average, higher in rural areas (40 ng/m³ on average), and still higher in urban areas (about 65-166 ng/m³ on 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 200-300 ng/m³ in air near foundries and to over 500 ng/m³ in air near ferro- and silico-manganese industries.

Manganese is a transition metal and therefore it cannot degraded in the environment. It can change its oxidation value states, it can form different compounds but it cannot be degraded.

 

In contrast, the acetate-ion /the acetic acid can be transformed by biotic and by abiotic processes in the environment. By photodegradation (sunlight /OH as sensitizer) ca. 50% is degraded in 21 day) Under aerobic conditions (OECD Guideline 301D) acetic acid is “ready biodegradable”. In air acetic acid will be converted to carbon dioxide, in microbes the acetic acid forms “activated acetate” and takes part in the normal metabolism and at the end it forms carbon dioxide, too.

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