Wintertime Nitrous Oxide Emissions in the San Joaquin Valley of California Estimated from Aircraft Observations

Abstract

Nitrous oxide (N 2 O) is a long-lived greenhouse gas that also destroys stratospheric ozone. N 2 O emissions are uncertain and characterized by high spatiotemporal variability, making individual observations difficult to upscale, especially in mixed land use source regions like the San Joaquin Valley (SJV) of California. Here, we calculate spatially integrated N 2 O emission rates using nocturnal and convective boundary-layer budgeting methods. We utilize vertical profile measurements from the NASA DISCOVER-AQ (Deriving Information on Surface Conditions from COlumn and VERtically Resolved Observations Relevant to Air Quality) campaign, which took place January−February, 2013. For empirical constraints on N 2 O source identity, we analyze N 2 O enhancement ratios with methane, ammonia, carbon dioxide, and carbon monoxide separately in the nocturnal boundary layer, nocturnal residual layer, and convective boundary layer. We find that an established inventory (EDGAR v4.3.2) underestimates N 2 O emissions by at least a factor of 2.5, that wintertime emissions from animal agriculture are important to annual totals, and that there is evidence for higher N 2 O emissions during the daytime than at night.

Aircraft-Based AirCore Sampling for Estimates of N2O and CH4 Emissions

“…Performing high-precision continuous airborne measurements, especially for N 2 O, poses challenges. To date, airborne measurements of N 2 O have been achieved simultaneously with other trace gases like CH 4 by quantum cascade laser spectrometers (QCLSs) in the campaigns such as CalNex, 16 This article is licensed under CC-BY 4 FEAST, 17 ACT-America, 6,18 the NASA DISCOVER-AQ mission 15 in the U.S. and GAUGE and MAMM 19 in England.…”

“…Aircraft extensively serve as a valuable mobile platform for atmospheric observations, enabling the estimation of greenhouse gas (GHG) emissions from local to regional scales. A mass balance approach has been commonly used with airborne CH 4 measurements ,− but less used for N 2 O , due to its typically small enhancements over the background. The development of a mid-infrared absorption spectrometer in the past decade made it feasible for high-precision airborne N 2 O measurements, thereby improving the signal-to-noise ratio of N 2 O and allowing for the application of a mass balance approach to CH 4 and N 2 O.…”

“…Performing high-precision continuous airborne measurements, especially for N 2 O, poses challenges. To date, airborne measurements of N 2 O have been achieved simultaneously with other trace gases like CH 4 by quantum cascade laser spectrometers (QCLSs) in the campaigns such as CalNex, FEAST, ACT-America, , the NASA DISCOVER-AQ mission in the U.S. and GAUGE and MAMM in England. During the performance test of an onboard QCLS, the retrieved concentrations of N 2 O and CH 4 from optical spectrometers are severely affected by variations in cabin pressure, , and several calibration strategies have been developed to correct for this issue but with their own limitations. − Fluctuations in input sample pressure propagating to a QCLS’s cell were found to impact N 2 O measurements more prominently than other trace gases .…”

“…Recently, Gvakharia et al (2020) 14 applied the mass balance approach to quantify N 2 O emissions from fertilizer plants and fertilized croplands. Similarly, Herrera et al (2021) 15 employed a boundary layer budget approach with airborne observations to estimate N 2 O emissions from agricultural and urban areas.…”

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

“…Nitrogen is essential for plant growth, but almost half of the nitrogen applied via fertilizers is lost to the air, water, or sediments rather than being assimilated by plants. − Soil nitrogen emissions to the atmosphere include several reactive nitrogen (Nr) compounds: nitric oxide (NO) and nitrous acid (HONO), which contributes to the formation of tropospheric ozone (O 3 ) and particulate matter (PM); , ammonia (NH 3 ), which contributes to the formation of PM; and nitrous oxide (N 2 O), which contributes to global warming and stratospheric ozone depletion. − Tropospheric O 3 and PM are the leading targets of air quality management in the United States due to their health impacts , and ongoing non-attainment of national standards in many regions…”