Acceptor acid rain

It is also used as an electron acceptor by microorganisms. Nitrihcation of ammonia N in soil is a source of nitrate. In addition, nonpoint and point source discharges from terrestrial ecosystems can be a major source of nitrate to wetlands and aquatic systems. In the atmosphere, nitrogen oxides can react with photochemically produced free radicals and produce nitric acid, which contributes to acid rain. Nitrate is also a common fertilizer used in agricultural ecosystems. 

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