Future-Year Ozone Isopleths for South Coast, San Joaquin Valley, and Maryland

Susan Collet,Prakash Karamchandani,Tejas Shah,Toru Kidokoro

doi:10.3390/atmos9090354

Susan Collet, Prakash Karamchandani + Show 2 more

Open Access

https://doi.org/10.3390/atmos9090354

Copy DOI

Abstract

Many areas of the United States are working toward achieving the 2015 ozone National Ambient Air Quality Standard (NAAQS) attainment level. The objective of this study was to develop future-year (2030) volatile organic compounds and nitrogen oxides (VOC-NOx) isopleth diagrams of the 4th highest maximum daily 8-h average ozone design value concentrations at monitors of interest in the South Coast Air Basin (SoCAB) and San Joaquin Valley (SJV) in California, and in Maryland. The simulation results showed there would be attainment of the 2015 ozone NAAQS in 2030 without further controls at the selected monitors: 27% in SoCAB, 57% in SJV, and 100% in Maryland. The SoCAB ozone isopleths developed in this study were compared with those reported in the South Coast Air Quality Management District 2016 Air Quality Management Plan. There are several differences between the two modeling studies, the results are qualitatively similar for most of the monitors in the relative amounts of additional emission reductions needed to achieve the ozone NAAQS. The results of this study provide insight into designing potential control strategies for ozone attainment in future years for areas currently in non-attainment. Additional photochemical modeling using these strategies can then provide confirmation of the effectiveness of the controls.

Highlights

Many areas of the United States (U.S.) are trying to achieve the current National Ambient AirQuality Standards (NAAQS) attainment level for ozone
This study developed future-year (2030) volatile organic compounds and nitrogen oxides (VOC-nitrogen oxides (NOx)) isopleths of H4MDA8 ozone design values at selected monitors in the South Coast Air Basin (SoCAB) and San Joaquin Valley (SJV) in California, and Maryland
Photochemical grid modeling for a large number of volatile organic compounds (VOCs) and NOx emission reduction scenarios were conducted to develop the isopleths of ozone design values versus VOC and NOx emissions in each region

Summary

Introduction

Many areas of the United States (U.S.) are trying to achieve the current National Ambient AirQuality Standards (NAAQS) attainment level for ozone. The chemistry leading to ozone production from emissions of VOC and NOx is non-linear [2]. Contour plots of ozone versus NOx and VOC emissions (ozone isopleths) are often employed to illustrate the non-linear response of ozone levels to NOx and VOC changes, and have been used in the past in the empirical kinetic modeling approach (EKMA) developed by the U.S Environmental Protection Agency (EPA) to develop control strategies for ozone reduction [3]. Once the maximum measured ozone concentration at a monitor has been identified, the VOC and NOx reductions needed to achieve the NAAQS level are determined using the EKMA from the distance along the VOC and NOx axes to the isopleth that represents the desired peak ozone concentration mandated by the NAAQS. The VOC/NOx ratio is important in the behavior of the VOC-NOx -ozone system and has a major effect on how reductions in VOC and NOx affect ozone concentrations [4]

Objectives

Methods

Results

Discussion

Conclusion