MODELING BIO-ATMOSPHERIC COUPLING OF THE NITROGEN-CYCLE THROUGH NOX EMISSIONS AND NOY DEPOSITION

The tropospheric and terrestrial nitrogen cycles are connected to one another through the emissions of NOx and NHx from soils and vegetation and the subsequent redeposition of these compounds and their products elsewhere. These connections play an important role in the Earth syst em influencing tropospheric concentrations of NOx, O-3, and CO2. Estim ates of the biogenic sources of NOx, soil emissions and biomass burnin g, are amongst the most variable terms in the global budget of NOx and are eclipsed only by lightning. A 3-D chemistry transport model, IMAG ES, was used to examine how soil emissions and biomass burning influen ce tropospheric concentrations of NOx and O-3 as well as NOx depositio n. Soil and biomass burning emissions of NOx contributed the most to a tmospheric NOx concentrations closest to the surface and south of 30 d egrees N. The influence of these emissions on tropospheric O-3 and NOx concentrations dissipated with height suggesting that these surface e missions are most important to surface ozone concentrations. The remov al of either the soil or biomass burning source resulted in a 5-20% di fference in tropospheric O-3 concentrations over large regions of the atmosphere. Both sources are also important contributors to N depositi on, particularly south of 30 degrees N which, in turn, can generate si gnificant carbon storage. These exercises demonstrate both the importa nce and complexity of the connections between atmospheric chemistry an d the terrestrial biosphere.