We report on the production and transport of nitric oxide generated in the Siberian upper troposphere by the 1908 Tunguska object. The simulation uses a complex three-dimensional chemistry and transport model of the global troposphere. In its terminal explosion the stony asteroid released some 5 × 1016 J of energy, producing about 0.4 Tg (1 Tg = 1012 g) of NO. We find that much of the nitric oxide forms nitric acid that deposits downwind the blast site within the first month, with possibly no severe damage to the ecosystem caused by acid rain. Ozone and OH are totally scavenged locally soon after the impact, then they increase respectively by 20-25% and 35-40% during the first month downwind the explosion point. The overall quantity of nitrogen produced agrees with estimates from Greenland ice cores, but deposition just below the explosion point is much lower in our simulations if compared with peat samples analysis. Considering the details of the chemistry-transport model this may be the first reliable calculation on the acid deposition distribution, and could help in locating interesting sites for future peat samples collection.
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