Question

Manganese is an important minor element in aquatic chemistry. Why? Touch on its general chemistry in water as well as what impact it has on other species and why.

Answer 1

Natural waters for example lakes streams, rivers, oceans contain variable amount of Mn ranging from 10 to 10,000 micro grams per liter. Mn constitutes about 0.1% of earths crust.Hence Mn is a natural contaminant in our environment. Due to natural presence in rocks Mn dissolves in water and accumuates in plants and subsequently transported to animals. Human sources include municipal waterdischarge, sewage, mining perticularly of Nickel,etc. Mn is an emerging toxic contaminent. It can demage. Mn toxicity is found in marine invertebrates. It is found in their their tissue and is an indication of concentration of mangnese in the water.

In aquatic environment Mn exists as either Mn⁺² or Mn⁺⁴ which are interconverted by oxidtion and reduction, either by biotic or abiotic sources. These two forms have important role to play as Mn⁺² forms are soluble and Mn⁺⁴ exists as insoluble oxide MnO₂. Mn as chlorides nitrates and sulphates in(+II)  oxidation state dissolves in water and is mobilized to living system. Solubiity of Mn increases with pH. concentration of Mn in wter is primarily controlled by pH and oxidation-reduction atmosphere. Solubility increases in acidic as well as anaerobic conditions, Because in Aerobic conditions Mn exists as stable highly insoluble MnO₂.