Top-Down Evaluation of Nitrous Oxide Emissions in Los Angeles Basin

Abstract:

Nitrous oxide (N₂O) is a potent long-lived greenhouse gas (GHG) that accounted for 3% of California’s GHG emissions in 2013^{1, 2}. It has been postulated that anthropogenic N₂O emissions may be larger than previously estimated. To evaluate this hypothesis, long-term measurements of N₂O and carbon monoxide (CO) concentrations were obtained at Mt. Wilson Monitoring Site between 2012 and 2015. This site provided a suitable location to study the regionally well-mixed urban emissions from the Los Angeles Basin. The resulting dataset was analyzed to investigate the monthly N₂O trends and seasonal variability of urban N₂O emissions in the region. N₂O:CO orthogonal regression slopes, integrated with regional CO emissions data³ (as an urban pollution surrogate), were used to estimate the top-down N₂O emissions from the Los Angeles Basin. The results from this top-down analysis were also analyzed to evaluate the various source sectors in the Los Angeles Basin.