Wintertime Vertical Variations in Particulate Matter (PM) and Precursor Concentrations in the San Joaquin Valley during the California Regional Coarse PM/Fine PM Air Quality Study

Brown, Samantha M.; Roberts, Paul T.; McCarthy, Michael C.; Hyslop, N. P.

doi:10.1080/10473289.2006.10464583

Cited by 44 publications

(29 citation statements)

References 32 publications

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“…The continuous aerosol nitrate concentrations at the surface were erratic and did not show the persistent increasing trends that were evident in the data from the 90-m elevation. 51 The apparent lack of nitrate formation at night at the surface is consistent with the near-zero O 3 levels and higher NO levels near the surface than aloft, and a number of studies that indicate NO 3 and N 2 O 5 levels decline dramatically near the surface. 45,[52][53][54][55][56][57][58] Meteorological transport of air containing differing amounts of nitrate undoubtedly contributes to the variations in nitrate concentrations; however, winds measured at 90 m during the December episode were light and variable, mostly Ͻ2 m/sec.…”

Section: Nitric Acid Formation Pathwayssupporting

confidence: 64%

Processes Influencing Secondary Aerosol Formation in the San Joaquin Valley during Winter

Brown

McCarthy

Roberts

2006

Journal of the Air & Waste Management Association

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Air quality data collected in the California Regional PM 10 / PM 2.5 Air Quality Study (CRPAQS) are analyzed to qualitatively assess the processes affecting secondary aerosol formation in the San Joaquin Valley (SJV). This region experiences some of the highest fine particulate matter (PM 2.5 ) mass concentrations in California (Յ188 g/m 3 24-hr average), and secondary aerosol components (as a group) frequently constitute over half of the fine aerosol mass in winter. The analyses are based on 15 days of high-frequency filter and canister measurements and several months of wintertime continuous gas and aerosol measurements. The phase-partitioning of nitrogen oxide (NO x )-related nitrogen species and carbonaceous species shows that concentrations of gaseous precursor species are far more abundant than measured secondary aerosol nitrate or estimated secondary organic aerosols. Comparisons of ammonia and nitric acid concentrations indicate that ammonium nitrate formation is limited by the availability of nitric acid rather than ammonia. Time-resolved aerosol nitrate data collected at the surface and on a 90-m tower suggest that both the daytime and nighttime nitric acid formation pathways are active, and entrainment of aerosol nitrate formed aloft at night may explain the spatial homogeneity of nitrate in the SJV. NO x and volatile organic compound (VOC) emissions plus background O 3 levels are expected to determine NO x oxidation and nitric acid production rates, which currently control the ammonium nitrate levels in the SJV. Secondary organic aerosol formation is significant in winter, especially in the Fresno urban area. Formation of secondary organic aerosol is more likely limited by the rate of VOC oxidation than the availability of VOC precursors in winter.

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Section: Nitric Acid Formation Pathwayssupporting

confidence: 64%

Processes Influencing Secondary Aerosol Formation in the San Joaquin Valley during Winter

Brown

McCarthy

Roberts

2006

Journal of the Air & Waste Management Association

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“…The influence of processes occurring in the aloft RL on NO − 3 (p) surface concentrations is evident in the NO − 3 (p) diurnal variability, specifically the occurrence of a midmorning peak in surface-level NO − 3 (p) . While the midmorning peak has been previously suggested as a signature of nocturnal nitrate production aloft (Watson and Chow, 2002;Brown et al, 2006a;Lurmann et al, 2006;Pusede et al, 2016;Young et al, 2016), the current study makes novel use of vertical profiles of NO − 3 (p) concentrations measured multiple times on individual days to quantitatively illustrate the importance of nocturnal processes on surface concentrations. The analysis shows that the NO − 3 (p) concentration in the morning-time mixed boundary layer can be dominated by nocturnally produced NO − 3 (p) ; vertical mixing in the early morning, which entrains air from the residual layer into the surface mixed layer, has a particularly large impact on the surface concentrations here due to the nocturnal boundary layer being exceptionally shallow.…”

Section: Resultsmentioning

confidence: 99%

“…Brown et al (2006a) observed that the number concentration of accumulation mode particles (0.32-1.07 µm) often increased above the surface at 90 m a.g.l. compared to surface (7 m a.g.l.)…”

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confidence: 94%

Observational assessment of the role of nocturnal residual-layer chemistry in determining daytime surface particulate nitrate concentrations

et al. 2017

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Abstract. This study discusses an analysis of combined airborne and ground observations of particulate nitrate ) concentrations made during the wintertime DISCOVER-AQ (Deriving Information on Surface Conditions from COlumn and VERtically resolved observations relevant to Air Quality) study at one of the most polluted cities in the United States -Fresno, CA -in the San Joaquin Valley (SJV) and focuses on developing an understanding of the various processes that impact surface nitrate concentrations during pollution events. The results provide an explicit case-study illustration of how nighttime chemistry can influence daytime surface-level NO 3 (p) in the RL, along with daytime photochemical production, can contribute substantially to the buildup and sustaining of severe pollution episodes. The exceptionally shallow nocturnal boundary layer (NBL) heights characteristic of wintertime pollution events in the SJV intensify the importance of nocturnal production aloft in the residual layer to daytime surface concentrations. The observations also demonstrate that dynamics within the RL can influence the earlymorning vertical distribution of NO − 3 (p) , despite low wintertime wind speeds. This overnight reshaping of the vertical distribution above the city plays an important role in determining the net impact of nocturnal chemical production on local and regional surface-level NO − 3 (p) concentrations. Entrainment of clean free-tropospheric (FT) air into the boundary layer in the afternoon is identified as an important process that reduces surface-level NO − 3 (p) and limits buildup during pollution episodes. The influence of dry deposition of HNO 3 gas to the surface on daytime particulate nitrate concentrations is important but limited by an excess of ammonia in the region, which leads to only a small fraction of nitrate existing in the gas phase even during the warmer daytime. However, in the late afternoon, when diminishing solar heating leads to a rapid fall in the mixed boundary layer height (BLH), the impact of surface deposition is temporarily enhanced and can lead to a substantial decline in surface-level particulate nitrate concentrations; this enhanced deposition is quickly arrested by a decrease in surface temperature, whichPublished by Copernicus Publications on behalf of the European Geosciences Union. 14748 G. Prabhakar et al.: Particulate nitrate formation in the wintertime drops the gas-phase fraction to near zero. The overall importance of enhanced late-afternoon gas-phase loss to the multiday buildup of pollution events is limited by the very shallow nocturnal boundary layer. The case study here demonstrates that mixing down of NO − 3 (p) from the RL can contribute a majority of the surface-level NO − 3 (p) in the morning (here, ∼ 80 %), and a strong influence can persist into the afternoon even when photochemical production is maximum. The particular day-to-day contribution of aloft nocturnal NO − 3 (p) production to surface concentrations will depend on prevailing chemical and meteorological ...

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“…NO at the 90 m level was near 0 throughout the night. A 7-day time series of NO − 3 data at 90 m showed clear increases in NO − 3 beginning at nightfall and persisting until sunrise of ∼ 10 µg m −3 (Brown et al, 2006). These diurnal patterns suggest that the NRL(s) decouple from the surface layer ∼ 3 h prior to sunset and that initial concentrations of the nocturnal chemistry reactants, NO 2 and O 3 , are also represented by surface concentrations 3 h prior to sunset.…”

Section: B1 No 3 -Initiated P No − 3 In the Nocturnal Residual Layermentioning

confidence: 90%

On the effectiveness of nitrogen oxide reductions as a control over ammonium nitrate aerosol

et al. 2016

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Abstract. Nitrogen oxides (NO x ) have fallen steadily across the US over the last 15 years. At the same time, NO x concentrations decrease on weekends relative to weekdays, largely without co-occurring changes in other gas-phase emissions, due to patterns of diesel truck activities. These trends taken together provide two independent constraints on the role of NO x in the nonlinear chemistry of atmospheric oxidation. In this context, we interpret interannual trends in wintertime ammonium nitrate (NH 4 NO 3 ) in the San Joaquin Valley of California, a location with the worst aerosol pollution in the US and where a large portion of aerosol mass is NH 4 NO 3 . Here, we show that NO x reductions have simultaneously decreased nighttime and increased daytime NH 4 NO 3 production over the last decade. We find a substantial decrease in NH 4 NO 3 since 2000 and conclude that this decrease is due to reduced nitrate radical-initiated production at night in residual layers that are decoupled from fresh emissions at the surface. Further reductions in NO x are imminent in California, and nationwide, and we make a quantitative prediction of the response of NH 4 NO 3 . We show that the combination of rapid chemical production and efficient NH 4 NO 3 loss via deposition of gas-phase nitric acid implies that high aerosol days in cities in the San Joaquin Valley air basin are responsive to local changes in NO x within those individual cities. Our calculations indicate that large decreases in NO x in the future will not only lower wintertime NH 4 NO 3 concentrations but also cause a transition in the dominant NH 4 NO 3 source from nighttime to daytime chemistry.

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Wintertime Vertical Variations in Particulate Matter (PM) and Precursor Concentrations in the San Joaquin Valley during the California Regional Coarse PM/Fine PM Air Quality Study

Cited by 44 publications

References 32 publications

Processes Influencing Secondary Aerosol Formation in the San Joaquin Valley during Winter

Processes Influencing Secondary Aerosol Formation in the San Joaquin Valley during Winter

Observational assessment of the role of nocturnal residual-layer chemistry in determining daytime surface particulate nitrate concentrations

On the effectiveness of nitrogen oxide reductions as a control over ammonium nitrate aerosol

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