Linking agricultural crop management and air quality models for regional to national-scale nitrogen assessments

[摘要] While nitrogen (N) is an essential element for life, human population growthand demands for energy, transportation and food can lead to excess nitrogenin the environment. A modeling framework is described and implemented topromote a more integrated, process-based and system-level approach to theestimation of ammonia (NH₃) emissions which result from the application ofinorganic nitrogen fertilizers to agricultural soils in the United States.The United States Department of Agriculture (USDA) Environmental PolicyIntegrated Climate (EPIC) model is used to simulate plant demand-drivenfertilizer applications to commercial cropland throughout the continental US.This information is coupled with a process-based air quality model to producecontinental-scale NH₃ emission estimates. Regional cropland NH₃emissions are driven by the timing and amount of inorganic NH₃fertilizer applied, soil processes, local meteorology, and ambient airconcentrations. Initial fertilizer application often occurs when crops areplanted. A state-level evaluation of EPIC-simulated, cumulative planted areacompares well with similar USDA reported estimates. EPIC-annual, inorganicfertilizer application amounts also agree well with reported spatial patternsproduced by others, but domain-wide the EPIC values are biased about 6%low. Preliminary application of the integrated fertilizer application and airquality modeling system produces a modified geospatial pattern of seasonalNH₃ emissions that improves current simulations of observed atmosphericparticle nitrate concentrations. This modeling framework provides a moredynamic, flexible, and spatially and temporally resolved estimate of NH₃emissions than previous factor-based NH₃ inventories, and willfacilitate evaluation of alternative nitrogen and air quality policy andadaptation strategies associated with future climate and land use changes.

[学科分类] 地球化学与岩石