Mobile Source and Livestock Feed Contributions to Regional Ozone Formation in Central California

Hu, Jianlin; Howard, Cody J.; Mitloehner, Frank M.; Green, Peter G.; Kleeman, Michael J.

doi:10.1021/es203369p

Cited by 38 publications

(33 citation statements)

References 31 publications

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“…We note that it has been previously speculated that a missing source of VOCR is important when O 3 is high in the SJV (Steiner et al, 2008;Hu et al, 2012;Pusede and Cohen, 2012). Organic sources with this temperature dependence include molecules with emission rates controlled by their vapor pressures, biogenic VOCs from forests The temperature-dependent VOCR is equal to the measured OH reactivity minus the temperature-independent i VOCR i and minus the OH reactivities of NO 2 , NO, HONO, HNO 3 , NH 3 , and SO 2 .…”

Section: Organic Reactivity and Temperaturementioning

confidence: 58%

On the temperature dependence of organic reactivity, nitrogen oxides, ozone production, and the impact of emission controls in San Joaquin Valley, California

et al. 2014

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Abstract. The San Joaquin Valley (SJV) experiences some of the worst ozone air quality in the US, frequently exceeding the California 8 h standard of 70.4 ppb. To improve our understanding of trends in the number of ozone violations in the SJV, we analyze observed relationships between organic reactivity, nitrogen oxides (NO x ), and daily maximum temperature in the southern SJV using measurements made as part of California at the Nexus of Air Quality and Climate Change in 2010 (CalNex-SJV). We find the daytime speciated organic reactivity with respect to OH during CalNex-SJV has a temperature-independent portion with molecules typically associated with motor vehicles being the major component.Published by Copernicus Publications on behalf of the European Geosciences Union. S. E. Pusede et al.: Temperature-dependent impacts of emission controlsAt high temperatures, characteristic of days with high ozone, the largest portion of the total organic reactivity increases exponentially with temperature and is dominated by small, oxygenated organics and molecules that are unidentified. We use this simple temperature classification to consider changes in organic emissions over the last and next decade. With the CalNex-SJV observations as constraints, we examine the sensitivity of ozone production (P O 3 ) to future NO x and organic reactivity controls. We find that P O 3 is NO x -limited at all temperatures on weekends and on weekdays when daily maximum temperatures are greater than 29 • C. As a consequence, NO x reductions are the most effective control option for reducing the frequency of future ozone violations in the southern SJV.

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Section: Organic Reactivity and Temperaturementioning

confidence: 58%

On the temperature dependence of organic reactivity, nitrogen oxides, ozone production, and the impact of emission controls in San Joaquin Valley, California

et al. 2014

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“…The UCD/CIT is a regional chemical transport model that has been extensively used to simulate the emissions, transport, chemistry, deposition and source contribution of pollutants in the lower troposphere (Kleeman and Cass, 2001) and evaluated against meteorological and gas-and particle-phase measurements (Hu et al, 2012(Hu et al, , 2015Jathar et al, 2015Jathar et al, , 2016 , 2010). Gas-phase chemistry was modeled using SAPRC-11.…”

Section: Chemical Transport Modelingmentioning

confidence: 99%

“…Gas-phase chemistry was modeled using SAPRC-11. For more details, we refer the reader to previous model applications (Hu et al, 2012;Jathar et al, 2016) and evaluations (Jathar et al, 2015. Primary emissions of HNCO were calculated by first determining a source-specific HNCO : CO ratio (see Table 1) and then combining them with source-specific, spatiotemporally resolved CO emissions to build an inventory for HNCO emissions.…”

Section: Chemical Transport Modelingmentioning

confidence: 99%

Investigating diesel engines as an atmospheric source of isocyanic acid in urban areas

et al. 2017

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Abstract. Isocyanic acid (HNCO), an acidic gas found in tobacco smoke, urban environments, and biomass-burningaffected regions, has been linked to adverse health outcomes. Gasoline-and diesel-powered engines and biomass burning are known to emit HNCO and hypothesized to emit precursors such as amides that can photochemically react to produce HNCO in the atmosphere. Increasingly, diesel engines in developed countries like the United States are required to use selective catalytic reduction (SCR) systems to reduce tailpipe emissions of oxides of nitrogen. SCR chemistry is known to produce HNCO as an intermediate product, and SCR systems have been implicated as an atmospheric source of HNCO. In this work, we measure HNCO emissions from an SCR system-equipped diesel engine and, in combination with earlier data, use a three-dimensional chemical transport model (CTM) to simulate the ambient concentrations and source/pathway contributions to HNCO in an urban environment. Engine tests were conducted at three different engine loads, using two different fuels and at multiple operating points. HNCO was measured using an acetate chemical ionization mass spectrometer. The diesel engine was found to emit primary HNCO (3-90 mg kg fuel −1 ) but we did not find any evidence that the SCR system or other aftertreatment devices (i.e., oxidation catalyst and particle filter) produced or enhanced HNCO emissions. The CTM predictions compared well with the only available observational datasets for HNCO in urban areas but underpredicted the contribution from secondary processes. The comparison implied that diesel-powered engines were the largest source of HNCO in urban areas. The CTM also predicted that dailyaveraged concentrations of HNCO reached a maximum of ∼ 110 pptv but were an order of magnitude lower than the 1 ppbv level that could be associated with physiological effects in humans. Precursor contributions from other combustion sources (gasoline and biomass burning) and wintertime conditions could enhance HNCO concentrations but need to be explored in future work.

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“…We employed the condensed form of the SAPRC-11 gas-phase chemical mechanism; the SAPRC-11 mechanism differs from the SAPRC-07 version used in earlier versions of the UCD/CIT model (Hu et al, 2012) in that it has an improved treatment of chemistry of aromatic VOCs. The uptake of N 2 O 5 to the aqueous phase was parameterized using the work of Davis et al (2008).…”

Section: Chemical Transport Modelmentioning

confidence: 99%

Water uptake by organic aerosol and its influence on gas/particle partitioning of secondary organic aerosol in the United States

Jathar

Mahmud

Barsanti

et al. 2016

Atmospheric Environment

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h i g h l i g h t sOrganic-phase water is predicted in eastern US and California using the same model. Organic-phase water enhances SOA formation in the eastern US. Organic-phase water has small effect on SOA formation in California. Different behavior is driven by regional emissions profiles. Particle mixing state changes the impact of organic-phase water. a r t i c l e i n f o Organic aerosol (OA) is at least partly hygroscopic, i.e., water partitions into the organic phase to a degree determined by the relative humidity (RH), the organic chemical composition, and the particle size. This organic-phase water increases the aerosol mass and provides a larger absorbing matrix while decreasing its mean molecular weight, which can encourage additional condensation of semi-volatile organic compounds. Most regional and global atmospheric models account for water uptake by inorganic salts but do not explicitly account for organic-phase water and its subsequent impact on gas/particle partitioning of semi-volatile OA. In this work, we incorporated the organic-phase water model described by Pankow et al. (2015) into the UCD/CIT air quality model to simulate water uptake by OA and assessed its influence on total OA mass concentrations. The model was run for one summer month over two distinct regions: South Coast Air Basin (SoCAB) surrounding Los Angeles, California and the eastern United States (US). In SoCAB where the OA was dominated by non-hygroscopic primary OA (POA), there was very little organic-phase water uptake (0.1e0.2 mg m À3) and consequently very little enhancement (or growth) in total OA concentrations (OA þ organic-phase water): a 3% increase in total OA mass was predicted for a 0.1 increase in relative humidity. In contrast, in the eastern US where secondary OA (SOA) from biogenic sources dominated the OA, substantial organic-phase water uptake and enhancement in total OA concentrations was predicted, even in urban locations. On average, the model predicted a 20% growth in total OA mass for a 0.1 increase in relative humidity; the growth was equivalent to a 250 nm particle with a hygroscopicity parameter (k) of 0.15. Further, for the same relative humidity, the exact extent of organic-phase water uptake and total OA enhancement was found to be dependent on the particle mixing state. When the source-oriented mixing state of aerosols was considered, generally, less organicphase water uptake was predicted than when simple internal mixing approximations were made. Overall, the results indicated that organic-phase water can significantly influence predicted total OA concentrations under certain conditions. Regional models applied in areas with high humidity and significant SOA formation should include calculations for organic-phase water in order to capture this effect.

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Mobile Source and Livestock Feed Contributions to Regional Ozone Formation in Central California

Cited by 38 publications

References 31 publications

On the temperature dependence of organic reactivity, nitrogen oxides, ozone production, and the impact of emission controls in San Joaquin Valley, California

On the temperature dependence of organic reactivity, nitrogen oxides, ozone production, and the impact of emission controls in San Joaquin Valley, California

Investigating diesel engines as an atmospheric source of isocyanic acid in urban areas

Water uptake by organic aerosol and its influence on gas/particle partitioning of secondary organic aerosol in the United States

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