Read the article, \"Ozone sensitivity to its precursor emissions in northeastern
ID: 284203 • Letter: R
Question
Read the article, "Ozone sensitivity to its precursor emissions in northeastern Mexico for a summer air pollution episode, " by A. Sierra, A. Y. Vanoye & A. Mendoza. Answer the following questions: What were the primary objective(s) of the study? What major emission sources are considered in the modeling? Why do they use a "base case" and what was it? What are the predicted effects on ozone concentrations of reducing VOC emissions by 50%? Are these predicted effects uniform across the modeled area? Why or why not? What are the predicted effects on ozone concentrations of reducing NOx emissions by 50%? Are these predicted effects uniform across the modeled area? Why or why not? Was an optimal VOC or NOx control strategy identified?Explanation / Answer
A) objective
1. To create a summer episode model to address the expected response of ambient air O3 to hypothetical emission control scenarios in northeastern Mexico, and in particular in the Monterrey Metropolitan Area (MMA).
2. To understand the O3–NOx–VOC relationship that exists at several locations of its airshed at different times using CTMs.
3. To demonstrate the difficulties that arise when trying to predict the response of O3 to emission control strategies, and highlights the need to keep addressing this issue with new and revised models as emissions change over time as a response to evolving conditions in the airshed.
B) The following major source of emmission are considered in the study
1.) Huge number of facilities of different productive sectors (cement, glass, metallurgy, petrochemical, food processing, electric utilities, and assembly, among others) that are located inside or nearby the metropolitan area .
2.) Non road mobile sources
3.) Onroad mobile sources.
4.) Area sources.
C) The base case
The basecase was selected as the location had a non-negligible response under VOC reduction scenarios.
In contrast to the VOC control scenarios, NOx control scenarios result in increments of O3 concentrations in the MMA and reductions at downwind locations of this area (preferentially to the north and south of the MMA), as depicted. Maximum O3 increments were 14 ppbv (25% NOx emissions reduction) and 20 ppbv (50% NOx emissions reduction), both at the same location within the MMA (west of the downtown area). Maximum reductions were registered to the south of the MMA (4 pbbv for the 25% NOx reduction scenario and 11 ppbv for the 50% reduction scenario). Both positive and negative responses appear to be nonlinear in nature, in contrast to what was observed in the VOCs control scenarios.
D) The largest reduction percentage (due to a 50% reduction in VOC emissions) occurred at the NW station This represents changes of –2 ppbv to þ5 ppbv.
These predicted effects were not same across all places, as some of the places are in high wind area and they were not strongly effected by tranportation emmissions.
E) Maximum increments and reductions in the peak O3 concentration occurred for the 50% NOx (VOCs unchanged)
F) The result estimated that O3 could be reduced by 20% with a 20% VOC reduction, but it could be increased by 11% with a 20% reduction in NOx emissions.
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