Integrated Modeling of U.S. Agricultural Soil Emissions of Reactive Nitrogen and Associated Impacts on Air Pollution, Health, and Climate

Abstract

Agricultural soils are leading sources of reactive nitrogen (Nr) species including nitrogen oxides (NO x ), ammonia (NH3), and nitrous oxide (N2O). The propensity of NO x and NH3 to generate ozone and fine particulate matter and associated impacts on health are highly variable, whereas the climate impacts of long-lived N2O are independent of emission timing and location. However, these impacts have rarely been compared on a spatially resolved monetized basis. In this study, we update the nitrogen scheme in an agroecosystem model to simulate the Nr emissions from fertilized soils across the contiguous United States. We then apply a reduced-form air pollution health effect model to assess air quality impacts from NO x and NH3 and a social cost of N2O to assess the climate impacts. Assuming an $8.2 million value of a statistical life and a $13,100/ton social cost of N2O, the air quality impacts are a factor of ∼7 to 15 times as large as the climate impacts in heavily populated coastal regions, whereas the ratios are closer to 2.5 in sparsely populated regions. Our results show that air pollution, health, and climate should be considered jointly in future assessments of how farming practices affect Nr emissions.

Methane-Derived Zero-Valent Carbon Solids Differentially Impact Model Nitrogen Cycling Bacteria and Significantly Inhibit Nitrification

“…Specifically, hindered nitrification would enhance N retention in soil (as NH 4 + ), potentially enhancing plant productivity and mitigating the transformation of NH 4 + to more mobile NO 3 – , reducing its contamination of water resources impacted by agricultural drainage. The benefits of ZVC would need to be evaluated against unintended negative consequences, such as potentially increased ammonia volatilization, which could lead to increased fine particulate aerosols, as has been inferred by air quality modeling . Additionally, via extrapolation from the biochar literature, it is important to ensure the absence of potential associated contaminants with ZVC (e.g., heavy metals, polycyclic aromatic hydrocarbons, and environmentally persistent free radicals) that could impact the growth of soil microbes and plants and assess whether ZVC exhibits electron shuttling properties that mitigate N 2 O emissions. , …”

“…The benefits of ZVC would need to be evaluated against unintended negative consequences, such as potentially increased ammonia volatilization, which could lead to increased fine particulate aerosols, 68 as has been inferred by air quality modeling. 69 Additionally, via extrapolation from the biochar literature, 70 it is important to ensure the absence of potential associated contaminants with ZVC (e.g., heavy metals, polycyclic aromatic hydrocarbons, and environmentally persistent free radicals) that could impact the growth of soil microbes and plants and assess whether ZVC exhibits electron shuttling properties that mitigate N 2 O emissions. 71,72 Although chemical nitrification inhibitors exist for improved nutrient retention and reduced NO x and N 2 O emissions, their effectiveness varies and potential exposure to such residual chemicals poses health risks to animals and humans.…”

Land-Use Decisions Have Substantial Air Quality Health Effects

“…Here we demonstrate that air quality health effects ought to be taken into account in land-use decision making, but more work would be needed to properly inform decision makers about which land-use decisions to consider. Such work could also incorporate other effects of how land is used, such as from nitrogen management decisions …”

Transcriptome Profiling and Chlorophyll Metabolic Pathway Analysis Reveal the Response of Nitraria tangutorum to Increased Nitrogen

“…N fertilization is known to increase plant yield and productivity [ 7 , 8 , 9 , 10 ]; however, over the years, it has also led to increased N fertilizer use by farmers and ranchers. Ecologically, the excessive application of fertilizer has disastrous effects, such as eutrophication [ 1 , 11 , 12 ], soil acidification [ 13 , 14 ], and air pollution [ 15 , 16 ], as well as changes in the structure and diversity of plant and soil microbials [ 17 , 18 ]. Conversely, N deficiency also affects the activities and processes of plant life by altering the levels of many amino acids and the biosynthesis of some carbohydrates [ 19 , 20 ].…”