Peroxycarboxylic Nitric Anhydrides Research Articles

An investigation of petrochemical emissions during KORUS-AQ: Ozone production, reactive nitrogen evolution, and aerosol production

Emissions and secondary photochemical products from the Daesan petrochemical complex (DPCC), on the west coast of South Korea, were measured from the NASA DC-8 research aircraft during the Korea-United States Air Quality campaign in 2016. The chemical evolution of petrochemical emissions was examined utilizing near-source and downwind plume transects. Small alkenes, such as ethene (C2H4), propene (C3H6), and 1,3-butadiene (C4H6), dominated the hydroxyl (OH) radical reactivity near the source region. The oxidation of these alkenes in the petrochemical plumes led to efficient conversion of nitrogen oxides (NOx) to nitric acid (HNO3), peroxycarboxylic nitric anhydrides (PANs), and alkyl nitrates (ANs), where the sum of the speciated reactive nitrogen contributes more than 80% of NOy within a few hours. Large enhancements of short-lived NOx oxidation products, such as hydroxy nitrates (HNs) and peroxyacrylic nitric anhydride, were observed, in conjunction with high ozone levels of up to 250 ppb, which are attributed to oxidation of alkenes such as 1,3-butadiene. Instantaneous ozone production rates, P(O3), near and downwind of the DPCC ranged from 9 to 24 ppb h−1, which were higher than those over Seoul. Ozone production efficiencies ranged from 6 to 10 downwind of the DPCC and were lower than 10 over Seoul. The contributions of alkenes to the instantaneous secondary organic aerosol (SOA) production rate, P(SOA), were estimated to be comparable to those of more common SOA precursors such as aromatics at intermediate distances from the DPCC. A model case study constrained to an extensive set of observations provided a diagnostic of petrochemical plume chemistry. The simulated plume chemistry reproduced the observed evolution of ozone and short-lived reactive nitrogen compounds, such as PANs and HNs as well as the rate and efficiency of ozone production. The simulated peroxy nitrates (PNs) budget included large contributions (approximately 30%) from unmeasured PNs including peroxyhydroxyacetic nitric anhydride and peroxybenzoic nitric anhydride. The large, predicted levels of these PAN compounds suggest their potential importance in chemical evolution of petrochemical plumes. One unique feature of the DPCC plumes is the substantial contribution of 1,3-butadiene to ozone and potentially SOA production. This work suggests that reductions in small alkene, especially 1,3-butadiene, emissions from the DPCC should be a priority for reducing downwind ozone.

Efficient photochemical generation of peroxycarboxylic nitric anhydrides with ultraviolet light-emitting diodes

Abstract. Photochemical sources of peroxycarboxylic nitric anhydrides (PANs) are utilized in many atmospheric measurement techniques for calibration or to deliver an internal standard. Conventionally, such sources rely on phosphor-coated low-pressure mercury (Hg) lamps to generate the UV light necessary to photo-dissociate a dialkyl ketone (usually acetone) in the presence of a calibrated amount of nitric oxide (NO) and oxygen (O2). In this manuscript, a photochemical PAN source in which the Hg lamp has been replaced by arrays of ultraviolet light-emitting diodes (UV-LEDs) is described. The output of the UV-LED source was analyzed by gas chromatography (PAN-GC) and thermal dissociation cavity ring-down spectroscopy (TD-CRDS). Using acetone, diethyl ketone (DIEK), diisopropyl ketone (DIPK), or di-n-propyl ketone (DNPK), respectively, the source produces peroxyacetic (PAN), peroxypropionic (PPN), peroxyisobutanoic (PiBN), or peroxy-n-butanoic nitric anhydride (PnBN) from NO in high yield (> 90 %). Box model simulations with a subset of the Master Chemical Mechanism (MCM) were carried out to rationalize product yields and to identify side products. The present work demonstrates that UV-LED arrays are a viable alternative to current Hg lamp setups.

A gas chromatograph for quantification of peroxycarboxylic nitric anhydrides calibrated by thermal dissociation cavity ring-down spectroscopy

Abstract. The peroxycarboxylic nitric anhydrides (PANs, molecular formula: RC(O)O2NO2) can readily be observed by gas chromatography (PAN-GC) coupled to electron capture detection. Calibration of a PAN-GC remains a challenge, because the response factors differ for each of the PANs, and because their synthesis in sufficiently high purity is non-trivial, in particular for PANs containing unsaturated side chains. In this manuscript, a PAN-GC and its calibration using diffusion standards, whose output was quantified by blue diode laser thermal dissociation cavity ring-down spectroscopy (TD-CRDS), are described. The PAN-GC peak areas correlated linearly with total peroxy nitrate (ΣPN) mixing ratios measured by TD-CRDS (r > 0.96). Accurate determination of response factors required the concentrations of PAN impurities in the synthetic standards to be subtracted from ΣPN. The PAN-GC and its TD-CRDS calibration method were deployed during ambient air measurement campaigns in Abbotsford, BC, from 20 July to 5 August 2012, and during the Fort McMurray Oil Sands Strategic Investigation of Local Sources (FOSSILS) campaign at the AMS13 ground site in Fort McKay, AB, from 10 August to 5 September 2013. The PAN-GC limits of detection for PAN, PPN, and MPAN during FOSSILS were 1, 2, and 3 pptv, respectively. For the Abbotsford data set, the PAN-GC mixing ratios were compared, and agreed with those determined in parallel by thermal dissociation chemical ionization mass spectrometry (TD-CIMS). Advantages and disadvantages of the PAN measurement techniques used in this work and the utility of TD-CRDS as a PAN-GC calibration method are discussed.

On quantitative measurements of peroxycarboxylic nitric anhydride mixing ratios by thermal dissociation chemical ionization mass spectrometry

Thermal dissociation chemical ionization mass spectrometry (TD-CIMS) has become an increasingly popular tool for rapid and sensitive quantification of peroxycarboxylic nitric anhydrides (PANs), which are important trace gas constituents of the troposphere. In TD-CIMS, the PANs are thermally dissociated in a heated inlet to NO 2 and peroxyacyl radicals, which are converted in electron transfer reactions with iodide reagent ions to the corresponding carboxylate anions. Here, we evaluate the performance of the TD-CIMS method in the presence of interferences that occur in polluted air masses. Response factors of the TD-CIMS were determined using laboratory-generated air samples and parallel measurements of NO 2 and ΣPAN by blue diode laser thermal dissociation cavity ring-down spectroscopy (TD-CRDS) and of NO y by NO-O 3 chemiluminescence (CL). The TD-CIMS was less sensitive to peroxymethacryloyl nitric anhydride (MPAN) than to other PANs tested, which was rationalized by differences in the temperature dependent loss rates of the peroxyacyl radicals in the heated inlet. To track matrix effects, photochemically generated 13C-labeled PAN was continuously added as an internal standard. The presence of NO or NO 2 in the sample gas mixture resulted in signal suppression, which could be corrected using the internal standard. The presence of organic acids resulted in a redistribution of count intensity between carboxylate anions, impacting the instrument's ability to accurately quantify PANs other than peroxyacetic nitric anhydride under moderately polluted conditions.

Absolute Measurements of Total Peroxy Nitrate Mixing Ratios by Thermal Dissociation Blue Diode Laser Cavity Ring-Down Spectroscopy

Peroxycarboxylic nitric anhydrides (PANs) have long been recognized as important trace gas constituents of the troposphere. Here, we describe a blue diode laser thermal dissociation cavity ring-down spectrometer for rapid and absolute measurements of total peroxyacyl nitrate (SigmaPAN) abundances at ambient concentration levels. The PANs are thermally dissociated and detected as NO2, whose mixing ratios are quantified by optical absorption at 405 nm relative to a reference channel kept at ambient temperature. The effective NO2 absorption cross-section at the diode laser emission wavelength was measured to be 6.1 x 10(-19) cm2 molecule(-1), in excellent agreement with a prediction based on a projection of a high-resolution literature absorption spectrum onto the laser line width. The performance, i.e., accuracy and precision of measurement and matrix effects, of the new 405 nm thermal dissociation cavity ring-down spectrometer was evaluated and compared to that of a 532 nm thermal dissociation cavity ring-down spectrometer using laboratory-generated air samples. The new 405 nm spectrometer was considerably more sensitive and compact than the previously constructed version. The key advantage of laser thermal dissociation cavity ring-down spectroscopy is that the measurement can be considered absolute and does not need to rely on external calibration.

Measurements of PANs during the New England Air Quality Study 2002

Measurements of peroxycarboxylic nitric anhydrides (PANs) were made during the New England Air Quality Study 2002 cruise of the NOAA RV Ronald H Brown. The four compounds observed, PAN, peroxypropionic nitric anhydride (PPN), peroxymethacrylic nitric anhydride (MPAN), and peroxyisobutyric nitric anhydride (PiBN) were compared with results from other continental and Gulf of Maine sites. Systematic changes in PPN/PAN ratio, due to differential thermal decomposition rates, were related quantitatively to air mass aging. At least one early morning period was observed when O3 seemed to have been lost probably due to NO3 and N2O5 chemistry. The highest O3 episode was observed in the combined plume of isoprene sources and anthropogenic volatile organic compounds (VOCs) and NOx sources from the greater Boston area. A simple linear combination model showed that the organic precursors leading to elevated O3 were roughly half from the biogenic and half from anthropogenic VOC regimes. An explicit chemical box model confirmed that the chemistry in the Boston plume is well represented by the simple linear combination model. This degree of biogenic hydrocarbon involvement in the production of photochemical ozone has significant implications for air quality control strategies in this region.

Measurement of peroxycarboxylic nitric anhydrides (PANs) during the ITCT 2K2 aircraft intensive experiment

Measurements of peroxycarboxylic nitric anhydrides (PANs), peroxyacetic nitric anhydride (CH3C(O)OONO2; PAN), and peroxypropionic nitric anhydride (CH3CH2C(O)OONO2; PPN) were made in the spring of 2002, off the west coast of North America, as part of the Intercontinental Transport and Chemical Transformation 2002 (ITCT 2K2) project. Long‐range transport of Asian emissions was observed in which PAN and PPN mixing ratios were as high as 650 pptv and 90 pptv, respectively. Moreover, these two species constituted as much as 80% of the odd nitrogen (NOy) in those air masses, and median PAN/NOy was more than 60% at altitudes of 4 km and above. Systematic differences in the ratio of PPN to PAN were observed in air masses that had been impacted by Asian urban emissions relative to those impacted by biomass burning. Mixing ratios of PAN and PPN were also elevated in the marine boundary layer close to the west coast of California, possibly because of photochemical production driven by maritime NOx emissions.

An examination of the chemistry of peroxycarboxylic nitric anhydrides and related volatile organic compounds during Texas Air Quality Study 2000 using ground‐based measurements

Measurements of peroxycarboxylic nitric anhydrides (PANs) along with related volatile organic compounds (VOCs) were made at the La Porte super site during the TexAQS 2000 Houston study. The PAN mixing ratios ranged up to 6.5 ppbv and were broadly correlated with O3, characteristic of a highly polluted urban environment. The anthropogenic PAN homologue concentrations were generally consistent with those found in other urban environments; peroxypropionic nitric anhydride (PPN) averaged 15%, and peroxyisobutyric nitric anhydride (PiBN) averaged 3% of PAN. Some periods were noted where local petrochemical sources resulted in anomalous PANs chemistry. This effect was especially noticeable in the case of peroxyacrylic nitric anhydride (APAN) where local sources of 1,3‐butadiene and acrolein resulted in APAN as high as 30% of PAN. Peroxymethacrylic nitric anhydride (MPAN) was a fairly minor constituent of the PANs except for two periods on 4 and 5 September when air masses from high biogenic hydrocarbons (BHC) areas were observed. BHC chemistry was not a factor in the highest ozone pollution episodes in Houston but may have an impact on daily average ozone levels in some circumstances.

Ground‐based measurements of peroxycarboxylic nitric anhydrides (PANs) during the 1999 Southern Oxidants Study Nashville Intensive

Peroxycarboxylic nitric anhydrides (PANs) were measured at Cornelia Fort Airpark during the 1999 Nashville Intensive of the Southern Oxidants Study. The observed concentrations were similar to those measured in the 1994 and 1995 Nashville Intensives. The average daytime ratio of peroxypropionic nitric anhydride (PPN) to peroxyacetic nitric anhydride (PAN) was 13.7%. Extensive measurements were also made of peroxyisobutyric nitric anhydride (PiBN), which confirm the anthropogenic origin of this compound, and its ratio to PAN was 2.4% on average. The daytime ratio of peroxymethacrylic nitric anhydride (MPAN) to PAN was as high as 25% during periods of high biogenic hydrocarbon (BHC) impact. A simple linear combination model was used to estimate anthropogenic hydrocarbon (AHC) and BHC contributions to O3 production. On average, 80% of the O3 observed over 80 ppbv was attributed to AHC chemistry and 20% to BHC chemistry. An exception to this was a plume derived from a combination of power plant NOx and isoprene emissions from west of the city, in which the BHC contribution was at least 50 to 75%.

Application of a sequential reaction model to PANs and aldehyde measurements in two urban areas

Measurements of the peroxycarboxylic nitric anhydrides (PANs = peroxyacetic nitric anhydride, PAN, peroxypropionic anhydride, PPN, and peroxymethacrylic nitric anhydride, MPAN) and aldehydes (acetaldehyde, propanal, and methacrolein) were made at Nashville, TN. in 1999 and Houston, TX. in 2000. The data were interpreted with a sequential reaction model that included reaction of aldehydes with hydroxyl radical and formation or loss of PANs mediated by peroxyacyl radicals {RC(O)OO}. The comparison of the measured ratios with those predicted by the model showed a disagreement for PAN/acetaldehyde and PPN/propanal in Nashville, but agreement in Houston. The Nashville data set also showed a disagreement in the case of PAN/acetaldehyde and MPAN/methacrolein, but agreement for PPN/propanal and MPAN/methacrolein. These features were consistent with the relative importance of isoprene to PAN formation at each site. The ratios were found to be highly correlated with ozone mixing ratios at each site.

Observations of APAN during TexAQS 2000

Measurements of peroxycarboxylic nitric anhydrides (PANs) made in Houston, Texas during TexAQS (Texas Air Quality Study) 2000 showed a relatively abundant PAN compound that had not been identified in previous studies in North America [cf. Williams et al., 2000]. This compound was hypothesized to be peroxyacrylic nitric anhydride {CH2=CH‐C(O)OONO2, APAN} based on the work of Tanimoto and Akimoto, [2001]. APAN was synthesized and characterized on one of the two GC systems used to make those measurements, subsequent to the TexAQS 2000 field study, confirming that APAN was observed during TexAQS 2000, both on the ground and in airborne measurements. Mixing ratios of APAN were estimated from the response of the system to PAN and PPN and ranged up to 502 pptv, which was 30% of PAN. High APAN values were associated with the precursor species 1,3‐butadiene and acrolein, which had local petrochemical sources. The presence of APAN at these unprecedented levels demonstrates the impact of these reactive VOC species, and may have associated health effects.

Intercomparison of ground‐based NOy measurement techniques

An informal intercomparison of NOy measurement techniques was conducted from June 13 to July 22, 1994, at a site in Hendersonville, Tennessee, near Nashville. The intercomparison involved five research institutions: Brookhaven National Laboratory, Environmental Science and Engineering, Georgia Institute of Technology, NOAA/Aeronomy Laboratory, and Tennessee Valley Authority. The NOy measurement techniques relied on the reduction of NOy species to NO followed by detection of NO using O3‐chemiluminescence. The NOy methods used either the Au‐catalyzed conversion of NOy to NO in the presence of CO or H2 or the reduction of NOy to NO on a heated molybdenum oxide surface. Other measurements included O3, NOx, PAN and other organic peroxycarboxylic nitric anhydrides, HNO3 and particulate nitrate, and meteorological parameters. The intercomparison consisted of six weeks of ambient air sampling with instruments and inlet systems normally used by the groups for field measurements. In addition, periodic challenges to the instruments (spike tests) were conducted with known levels of NO, NO2, NPN, HNO3 and NH3. The NOy levels were typically large and highly variable, ranging from 2 ppbv to about 100 ppbv, and for much of the time was composed mostly of NOx from nearby sources. The spike tests results and ambient air results were consistent only when NOx was a substantial fraction of NOy. Inconsistency with ambient air data and the other spike test results is largely attributed to imprecision in the spike results due to the high and variable NOy background. For the ambient air data, a high degree of correlation was found with the different data sets. Of the seven NOy instrument/converters deployed at the site, two (one Au and one Mo) showed evidence of some loss of conversion efficiency. This occurred when the more oxidized NOy species (e.g., HNO3) were in relatively high abundance, as shown by analysis of one period of intense photochemical activity. For five of the instruments, no significant differences were found in the effectiveness of NOy conversion at these levels of NOy with either Au or Mo converters. Within the estimated uncertainty limits there was agreement between the sum of the separately measured NOy species and the NOy measured by the five of the seven techniques. These results indicate that NOy can be measured reliably in urban and suburban environments with existing instrumentation.

Measurement of alkyl nitrates at Chebogue Point, Nova Scotia during the 1993 North Atlantic Regional Experiment (NARE) intensive

Measurements of six alkyl nitrates, methyl‐, ethyl‐, 1‐propyl‐, 2‐propyl‐, 2‐butyl, and 3‐pentyl nitrates, and two peroxycarboxylic nitric anhydrides, peroxyacetic nitric anhydride (PAN) and peroxypropionic nitric anhydride (PPN) were made at Chebogue Point, Nova Scotia, during the 1993 North Atlantic Regional Experiment campaign. The correlation of alkyl nitrates (RONO2) with carbon monoxide makes it clear that the chemistry at this site is being driven by continental emissions, since RONO2 compounds are known to be by‐products of HC‐NOx photochemistry. Comparison of the ratios of alkyl nitrates to their parent hydrocarbons to that of 2‐butyl nitrate/butane showed significant deviations from trends predicted from rate constants, branching ratios, and loss rates. For ethyl nitrate this deviation is likely due to a combination of many additional pathways to the intermediate peroxy radical from the decomposition of larger alkoxy radicals. The propyl nitrates showed trends that differed from one another; 2‐propyl nitrate was a factor of 2 to 3 higher than predicted, while 1‐propyl nitrate was a factor of 8 to 10 higher than predicted. The trend of 3‐pentyl nitrate/pentane was relatively close (about 50% lower) to the predicted trend. The relationship between PAN and PPN showed unexpectedly high ratios of PPN to PAN in air masses coming from the south and west of the site, implying a slight local source of PPN.

Capillary gas chromatographic separation of alkyl nitrates and peroxycarboxylic nitric anhydrides

The measurement of peroxycarboxylic nitric anhydrides (so-called PAN-type compounds) has become a crucial part of atmospheric chemical research. One such compound, peroxyacetic nitric anhydride (PAN), has been shown to comprise a large fraction of photochemically active nitrogen, which is often referred to as reactive odd-nitrogen (NO/sub y/). PAN, while originally discovered and measured by IR spectroscopy, is routinely measured by gas chromatography with electron capture detection (GC/ECD). The packed columns used for this analysis have changed little in the past 25 years and have consisted mainly of low-molecular-weight Carbowax liquid phases on deactivated solid supports. Alkyl nitrates (RONO/sub 2/) have emerged as another class of compounds likely to contribute to atmospheric NO/sub y/, and preliminary measurements of them have been made by capillary GC/ECD. The authors wish to report here preliminary studies on use of capillary gas chromatographic columns for the simultaneous analysis of both PAN-type compounds and alkyl nitrates in the presence of ambient atmospheric halogenated hydrocarbons. The goal of this research has been the development of a single method for the atmospheric measurement of PAN and peroxypropionic nitric anhydride (PPN), as well as alkyl nitrates in the size range C/sub 1/-C/sub 5/. Capillary columns are a logical choicemore » for such a method due to increased resolution and potentially shorter analysis times relative to packed columns.« less