decline 1 4c how do we know that it is anthropogenic

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Unformatted text preview: 4C] in atmosphere should ... decline 1 4C How do we know that it is anthropogenic factors? Model predictions based on... natural factors only combination of natural and anthropogenic factors anthropogenic factors only Nitrogen: Atmosphere is largest reservoir (78% of atmosphere is N), but.... ... inaccessible for most organisms N enters cycle only via micro-organisms or lightning biological fixation: N2 ➡ NH3 ( Ammonia) free-living bacteria, cyanobacteria; symbionts (e.g., legumes, alders) Rhizobium in legumes symbiotic lichens (cyanobacteria + fungi) atmospheric fixation: N2 ➡ NO, dissolve in water & form nitrates (5-8% of total fixation) Nitrogen cycle Atmosphere N 2, N2 ➡ Organisms proteins Fungi Bacteria Plants NO Denitrification Fixation N H3 N 2 ➡ N O NO3- specialized bacteria, Nitrate anaerobic conditions (esp. in ocean, wetlands) removal of excess nitrate from groundwater (excessive agricultural or residential fertilizer) => sewage treatment, wetlands NO2Nitrite Decay NH3 Ammonia Nitri...
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