NITROGEN DEPOSITION ONTO THE UNITED STATES AND WESTERN EUROPE: SYNTHESIS OF OBSERVATIONS AND MODELS

摘要: The documented acceleration of NH3 and NOx (NO NO2) emissions over the last 150 years has accelerated N deposition, compromising air water quality altering functioning terrestrial aquatic ecosystems worldwide. To construct con- tinental-scale budgets, we produced maps deposition fluxes from site-network observations for United States Western Europe. Increases in rates cycling these two regions world are large, they have undergone profound modification biospheric-atmospheric exchanges, ecosystem function. necessarily restricted to network measured quantities consist statistically interpolated fields aqueous NO3 NH4, gaseous HNO3 NO2 (in Europe), particulate NH4. There remain a number gaps including organic de- position. spatially continuous allow estimation regionally inte- grated budget terms. Dry-deposition were most problematic because low station density uncertainties associated with exchange mechanisms. We estimated dry position by multiplying surface-air concentrations each chemical species model-calculated, explicit velocities. Deposition ox- idized species, by-products fossil-fuel combustion, dominate U.S. 2.5 Tg NOy-N out total 3.7-4.5 deposited annually onto conterminous States. reduced which farming animal husbandry, European N-deposition 4.3-6.3 year 8.4-10.8 N. Europe receives five times more precipitation than does Estimated exceed 5.3- 7.81 N, suggesting significant export or under-sampling urban influence. In Europe, better balance an imbalance between 0.63 2.88 that much emitted is there, possible import sampling includes influences greater population Our analysis both was limited density. framework present quantification patterns provides constraint on our under- standing continental cycles. These wet also provide tool verifying regional global models atmospheric chemistry transport, represent critical inputs into bio- geochemistry.