The Production of Atmospheric NO2 and N2O from a Fertilized Agricultural Soil

The source strength of atmospheric trace gases from rural or remote locations must be quantified in order to assess the effect of such inputs on the background tropospheric chemistry. To assess the importance of biological production of NOx and N2O from fertilized agricultural soil, enclosure techniques have been used to determine the emission fluxes of NOx and N2O at a site in Southern Ontario, Canada. NOx fluxes on the unfertilized soil range from 1.5 to 41.6 μg(NO) m−2 h−1. The corresponding N2O fluxes are 0–61.8 μg(N2O)m−2h−1. For the most fertilized soil NOx fluxes range from 3.1 to 583 μg(NO) m−2h−1 and the N2O fluxes from 0 to 446 μg(N2O) m−2h−1. The fluxes increase linearly with fertilizer application, with 11% of the nitrogen in the fertilizer converted to NOx and 5% to N2O. The emission rates were studied as functions of the soil parameters temperature, moisture, ammonium, nitrate and pH, to attempt to understand better the production mechanisms, although a model for the process could not be developed. In rural areas away from transportation corridors the increased NOx emission from fertilized soil may dominate local oxidant production but is not significant on the Province-wide scale