A comparative study of ozone production in five U.S. metropolitan areas

Abstract

. Ozone production rates P(O 3 ) and their sensitivity to NO x and volatile organic carbons (VOCs) are calculated using observed concentrations as inputs to a steady state box model. City to city comparisons are made to illustrate common features of urban photochemistry and features that are unique to specific cities. Ozone production rates vary from nearly zero to 155 ppb h À1 . Differences in P(O 3 ) depend on precursor concentrations, namely, radical sources, NO x and VOCs. Under conditions where P(O 3 ) is greater than 25 ppb h À1 , there is a potential to produce enough same-day O 3 to transform a typical regional background into a severe O 3 episode. Six such cases were observed, in Nashville, Philadelphia, and Houston, with elevated O 3 concentrations in the afternoon (130-211 ppb) following a morning in which P(O 3 ) was 25-140 ppb h À1 . High P(O 3 ) occurs when NO x concentrations are 5-25 ppb and OH-VOC reactivity is above 5 s À1 . These conditions are infrequent, and aside from a common dependence on calm winds, reasons vary from city to city. In Nashville, high P(O 3 ) was observed during a stagnation event over downtown and under the circumstance that an air mass with a high concentration of isoprene encountered a NO x source. In Houston, NO x and light olefins are coemitted from petrochemical facilities leading to the highest P(O 3 )s of the five cities studied. High values of P(O 3 ) did not occur in Phoenix because of low radical production, caused mainly by a dry atmosphere, and a low VOC to NO x ratio. The sensitivity of P(O 3 ) to its precursors varied from NO x limited in rural samples to VOC limited near emission sources. In Philadelphia, and especially Phoenix, the highest O 3 production rates occurred under VOC-limited conditions. In Nashville, New York City, and Houston the high-P(O 3 ) samples were near the ridge line where P(O 3 ) responds somewhat to VOC reductions but is insensitive to NO x changes.

Ozone production in remote oceanic and industrial areas derived from ship based measurements of peroxy radicals during TexAQS 2006

“…The higher ozone production rates in Houston compared to other urban areas were attributed to the co-location of NO x and highly reactive olefins emissions from the petrochemical plants in the Houston/Galveston area. Kleinman et al (2005) also noted, by looking at data from Philadelphia, Pennsylvania, and Phoenix, Arizona, that morning and afternoon ozone production rates were generally comparable. Although a straightforward comparison is not possible, this is consistent with the data presented in this work (Fig.…”

“…Ryerson et al, 2003;Jobson et al, 2004;Kleinman et al, 2005) have highlighted the special chemical characteristics of the Houston/Galveston area: co-located large emissions of NO x and of highly reactive VOC (particularly light alkenes) combined with the unique meteorology described above result in some of the highest concentrations of urban ozone in the United States. Measurements of peroxy radicals in such photochemically active air masses provide a unique look into their chemistry and assists in understanding the factors that influence ozone production across the region.…”

“…While high, these values are not uncommon. Kleinman et al (2005) reported ozone production rates on the order of tens of ppb/h in several US urban areas and, in particular, in Houston, Texas, where production rates were up to 155 ppb/h. The higher ozone production rates in Houston compared to other urban areas were attributed to the co-location of NO x and highly reactive olefins emissions from the petrochemical plants in the Houston/Galveston area.…”

Differences between measured and reported volatile organic compound emissions from oil sands facilities in Alberta, Canada

“…Volatile organic compounds (VOCs) are tightly coupled to atmospheric oxidative capacity, ozone formation, and secondary organic aerosol formation (9)(10)(11)(12). A large number of VOCs also have known toxic impacts on human health (13).…”

Sources of C2–C4 alkenes, the most important ozone nonmethane hydrocarbon precursors in the Pearl River Delta region

“…Also OH is involved in the oxidation of VOCs that leads to the formation of tropospheric ozone and secondary organic aerosol (SOA) (Brasseur et al, 2003), and thus among numerous OH sinks VOCs are the most significant. OH reactivity, calculated as the product of the rate constant with OH and the mixing ratio, is widely used as an estimate of the potential to consume OH for a single VOC (Kleinman et al, 2000(Kleinman et al, , 2005Lou et al, 2010):…”