Air Quality Field Measurements in Las Vegas: Ozone Formation and Its Sensitivity to NO_x and VOCs

Las Vegas, Nevada is an urban center in the southwest US where the population is rapidly growing. In Las Vegas, surrounded by the Mojave Desert, biogenic emissions are low, but anthropogenic emissions, especially along the Las Vegas Strip, are a large source of volatile organic compounds (VOC) and nitrogen oxides (NO + NO₂ = NO_x) from volatile chemical products, cooking, and fossil fuel usage. This makes Las Vegas an ideal place to study anthropogenic VOC emissions and oxidation in the absence of a strong biogenic signal. The urban air quality in Las Vegas was measured at a stationary site and with a mobile laboratory. Biogenic VOC influence, VOC enhancement ratios, and weekday-weekend effects were evaluated. An Eulerian box model was constructed to evaluate the chemical processes impacting air quality in Las Vegas. The model showed that the daily ozone (O₃) enhancement, taken as the maximum O₃ produced midday above background, was approximately 30 ppb. The O₃ sensitivities to VOCs and NO_x showed that reductions in both would reduce O₃ production. Reducing NO_x or VOCs by half would reduce O₃ by 10.5 and 11.5 ppb, respectively. Reducing both NO_x and VOCs together would decrease O₃ by 15 ppb. The O₃ contribution from biogenic VOCs was ∼3.5 ppb, which is about 10% of the total produced O₃. This differs from other regions of the US, such as New York or Los Angeles, where biogenic VOCs contribute significantly to urban ozone.