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Robert J. Soreng - One of the best experts on this subject based on the ideXlab platform.

  • An updated checklist and key to the open-panicled species of Poa L. (Poaceae) in Peru including three new species, Poa ramoniana, Poa tayacajaensis, and Poa urubambensis.
    PhytoKeys, 2016
    Co-Authors: Steven P. Sylvester, Robert J. Soreng, Paul M. Peterson, Mitsy D. P. V. Sylvester
    Abstract:

    We provide an updated checklist and key to the 30 Poa species with open panicles from Peru which includes previously circumscribed Dissanthelium and Aphanelytrum species, new taxon records, and three undescribed species. Poa compressa, Poa grisebachii, and Poa leioclada are recorded from Peru for the first time. A number of species are placed in synonymy: Poa carazensis, Poa ferreyrae and Poa tovarii are synonymized under the name Poa fibrifera; Poa adusta (tentatively) and Poa pilgeri are synonymized under Poa candamoana; Poa superata is synonymized under Poa grisebachii; and Poa paramoensis is synonymized under Poa huancavelicae. Included within this treatment are three new species, Poa ramoniana, Poa tayacajaensis and Poa urubambensis, which are described and illustrated. Poa ramoniana, found growing near lakes in high elevation Puna grasslands of Junin, is similar to a small form of Poa glaberrima, but differs in having rhizomes and growing to only 5 cm tall. Poa tayacajaensis, found from shrublands on Andean slopes of Huancavelica and Huanuco, bears similarities to Poa aequatoriensis but differs in having shorter lemmas which are pubescent between the veins, densely scabrous sheaths with smooth, glabrous throats, and shorter ligules. Poa urubambensis, a common element of the undisturbed Polylepis forest understory of the Cordillera Urubamba, Cusco, is distinct from all other members of open-panicled Poa's by having glabrous lemmas with a smooth and glabrous callus, and notably small anthers. The type material for the name Poa adusta is discussed and a lectotype is selected.

  • A revision of Poa subsection Aphanelytrum (Poaceae, Pooideae, Poaeae, Poinae); and a new species, Poa auriculata.
    PhytoKeys, 2016
    Co-Authors: Paul M. Peterson, Robert J. Soreng
    Abstract:

    In this study the peculiar Andean grass genus Aphanelytrum, with two species, is reduced to Poa subsect. Aphanelytrum comb. & stat. nov. A third species, Festuca reclinata, is assigned to the subsection, which shows states transitional between a more typical Poa and Aphanelytrum. Poa subgen. Poa supersect. HomaloPoa sect. DioicoPoa subsect. Aphanelytrum comb. & stat. nov. is characterized in having stooling perennials with decumbent to spreading culm bases that continuously branch and often root at low to mid-culm nodes, glabrous spikelets with long rachillas 1.2-4.2 mm long, short glumes less than ½ the length of the florets, and lemmas with bifid apexes that are mucronate to short-awned. We provide for the three species taxonomic discussions, morphological and anatomical descriptions, keys, illustrations, and a list of specimens. Also, we provide two new names, Poa hitchcockiana nom. nov. and Poa sanchez-vegae nom. nov., and one new combination, Poa reclinata comb. nov. A new species, Poa auriculata sp. nov. from Peru, not thought to be a member of Poa subsect. Aphanelytrum, is presented. It is the first in the genus with prominent auricles. In addition, we place Poa apiculata in Poa subgen. Poa supersect. HomaloPoa sect. DioicoPoa subsect. Tovarochloa comb. & stat. nov.

  • Two new records and one confirmation of the genus Poa L. (Poaceae) for the Flora of Turkey
    TURKISH JOURNAL OF BOTANY, 2016
    Co-Authors: Evren Cabi, Robert J. Soreng
    Abstract:

    The ongoing revision of the genus Poa in Turkey has resulted in two new Poa records for the Flora of Turkey as Poa pratensis subsp. irrigata (Lindm.) H. Lindb. and Poa eigii Feinbrun. In addition, the presence of Poa palustris L. is confirmed. A brief discussion and an illustration for each taxon are provided.

  • Phylogeny of Poa (Poaceae) Based on trnT–trnF Sequence Data: Major Clades and Basal Relationships
    Aliso, 2007
    Co-Authors: Lynn J. Gillespie, Annie Archambault, Robert J. Soreng
    Abstract:

    Poa, the largest genus of grasses (Poaceae) with over 500 species, occurs throughout temperate and boreal regions in both hemispheres. A phylogenetic study of Poa based on trnT-trnF chloroplast DNA sequence data is presented focusing on basal relationships, major clades, generic boundaries, and placement of putatively closely related genera. Results support the monophyly of the main lineage of Poa if subgen. Andinae is excluded and Anthochloa, Austrofestuca, Dissanthelium (at least in part), and EremoPoa are included. The main Poa clade and subgen. Andinae resolve within a strongly supported Poinae-Alopecurinae-Miliinae clade (PAM). The subdivision of Poa into five major clades, proposed based on chloroplast restriction site data, is supported by sequence data. The basal-most clade (ArcSyl) comprises Poa subgen. ArctoPoa and subgen. Poa sect. Sylvestres, two groups having disparate morphology, but similar cpDNA. The next-diverging clade (BAPO), comprising sects. Bolbophorum, Alpinae, Parodiochloa, and OchloPoa, is strongly supported and characterized by highly divergent cpDNA. The majority of Poa species and sections form a strongly supported clade comprising major clades SPOSTA. PoM, and HAMBADD. Newly reported in this study is EremoPoa as a distinct lineage positioned between this higher Poa clade and BAPO. A revised infrageneric classification of Poa comprising five subgenera is proposed. Two new subgeneric divisions of Poa are proposed: subgen. StenoPoa for the SPOSTA clade and supersect. HomaloPoa for the HAMBADD clade. The monotypic genus Anthochloa is reduced to Poa sect. Anthochloa, and its one species recognized as Poa lepidula.

  • phylogeny of Poa Poaceae based on trnt trnf sequence data major clades and basal relationships
    Aliso, 2007
    Co-Authors: Lynn J. Gillespie, Annie Archambault, Robert J. Soreng
    Abstract:

    Poa, the largest genus of grasses (Poaceae) with over 500 species, occurs throughout temperate and boreal regions in both hemispheres. A phylogenetic study of Poa based on trnT-trnF chloroplast DNA sequence data is presented focusing on basal relationships, major clades, generic boundaries, and placement of putatively closely related genera. Results support the monophyly of the main lineage of Poa if subgen. Andinae is excluded and Anthochloa, Austrofestuca, Dissanthelium (at least in part), and EremoPoa are included. The main Poa clade and subgen. Andinae resolve within a strongly supported Poinae-Alopecurinae-Miliinae clade (PAM). The subdivision of Poa into five major clades, proposed based on chloroplast restriction site data, is supported by sequence data. The basal-most clade (ArcSyl) comprises Poa subgen. ArctoPoa and subgen. Poa sect. Sylvestres, two groups having disparate morphology, but similar cpDNA. The next-diverging clade (BAPO), comprising sects. Bolbophorum, Alpinae, Parodiochloa, and OchloPoa, is strongly supported and characterized by highly divergent cpDNA. The majority of Poa species and sections form a strongly supported clade comprising major clades SPOSTA. PoM, and HAMBADD. Newly reported in this study is EremoPoa as a distinct lineage positioned between this higher Poa clade and BAPO. A revised infrageneric classification of Poa comprising five subgenera is proposed. Two new subgeneric divisions of Poa are proposed: subgen. StenoPoa for the SPOSTA clade and supersect. HomaloPoa for the HAMBADD clade. The monotypic genus Anthochloa is reduced to Poa sect. Anthochloa, and its one species recognized as Poa lepidula.

Q Zhang - One of the best experts on this subject based on the ideXlab platform.

  • characterization of the sources and processes of organic and inorganic aerosols in new york city with a high resolution time of flight aerosol mass apectrometer
    Atmospheric Chemistry and Physics, 2010
    Co-Authors: Yele Sun, Q Zhang, James J Schwab, Kenneth L Demerjian, Weinai Chen, Minsuk Bae, Huiming Hung, Olga Hogrefe
    Abstract:

    Submicron aerosol particles (PM1) were measured in-situ using a High-Resolution Time-of-Flight Aerosol Mass Spectrometer during the summer 2009 Field Intensive Study at Queens College in New York, NY. Organic aerosol (OA) and sulfate are the two dominant species, ac- counting for 54% and 24%, respectively, of the total PM1 mass. The average mass-based size distribution of OA presents a small mode peaking at 150 nm (Dva) and an accumulation mode ( 550 nm) that is internally mixed with sulfate, nitrate, and ammonium. The diurnal cycles of both sulfate and OA peak between 01:00-02:00 p.m. EST due to photochemical production. The average (± ) oxygen- to-carbon (O/C), hydrogen-to-carbon (H/C), and nitrogen- to-carbon (N/C) ratios of OA in NYC are 0.36 (±0.09), 1.49 (±0.08), and 0.012 (±0.005), respectively, correspond- ing to an average organic mass-to-carbon (OM/OC) ratio of 1.62 (±0.11). Positive matrix factorization (PMF) of the high resolution mass spectra identified two primary OA (Poa) sources, traffic and cooking, and three secondary OA (SOA) components including a highly oxidized, re- gional low-volatility oxygenated OA (LV-OOA; O/C = 0.63), a less oxidized, semi-volatile SV-OOA (O/C = 0.38) and a unique nitrogen-enriched OA (NOA; N/C = 0.053) character- ized with prominent CxH2x+2N + peaks likely from amino compounds. Our results indicate that cooking and traffic are two distinct and mass-equivalent Poa sources in NYC, together contributing 30% of the total OA mass during this study. The OA composition is dominated by secondary species, especially during high PM events. SV-OOA and LV- OOA on average account for 34% and 30%, respectively, of the total OA mass. The chemical evolution of SOA in NYC appears to progress with a continuous oxidation from SV-OOA to LV-OOA, which is further supported by a grad- ual increase of O/C ratio and a simultaneous decrease of H/C ratio in total OOA. Detailed analysis of NOA (5.8% of OA) presents evidence that organic nitrogen species such as amines might have played an important role in the atmo- spheric processing of OA in NYC, likely involving both acid- base chemistry and photochemistry. In addition, analysis of air mass trajectories and satellite imagery of aerosol optical depth (AOD) indicates that the high potential source regions of secondary sulfate and aged OA are mainly located in re- gions to the west and southwest of the city.

  • highly time resolved chemical characterization of atmospheric submicron particles during 2008 beijing olympic games using an aerodyne high resolution aerosol mass spectrometer
    Atmospheric Chemistry and Physics, 2010
    Co-Authors: Xiaofeng Huang, Q Zhang, Lingyan He, M Hu, Manjula R Canagaratna, Liming Zeng, Y H Zhang, John T Jayne, Nga L Ng, D R Worsnop
    Abstract:

    As part of Campaigns of Air Quality Research in Beijing and Surrounding Region-2008 (CAREBeijing- 2008), an Aerodyne High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) was deployed in urban Beijing to characterize submicron aerosol particles during the time of 2008 Beijing Olympic Games and Paralympic Games (24 July to 20 September 2008). The campaign mean PM1 mass concentration was 63.1± 39.8 µg m 3 ; the mean composition consisted of organics (37.9%), sulfate (26.7%), ammonium (15.9%), nitrate (15.8%), black carbon (3.1%), and chloride (0.87%). The average size distributions of the species (except BC) were all dominated by an accumulation mode peaking at about 600 nm in vacuum aerodynamic diameter, and organics was characterized by an additional smaller mode extending below 100 nm. Positive Matrix Factorization (PMF) anal- ysis of the high resolution organic mass spectral dataset differentiated the organic aerosol into four components, i.e., hydrocarbon-like (HOA), cooking-related (COA), and two oxygenated organic aerosols (OOA-1 and OOA-2), which on average accounted for 18.1, 24.4, 33.7 and 23.7% of the total organic mass, respectively. The HOA was identified to be closely associated with primary combustion sources, while the COA mass spectrum and diurnal pattern showed similar characteristics to that measured for cooking emis- sions. The OOA components correspond to aged secondary organic aerosol. Although the two OOA components have similar elemental (O/C, H/C) compositions, they display differences in mass spectra and time series which appear to correlate with the different source regions sampled during the campaign. Back trajectory clustering analysis indicated that the southerly air flows were associated with the highest PM1 pollution during the campaign. Aerosol particles in southern airmasses were especially rich in inorganic and oxidized organic species. Aerosol particles in northern airmasses contained a large fraction of primary HOA and COA species, probably due to stronger influences from local emissions. The lowest concentration levels for all major species were obtained during the Olympic game days (8 to 24 August 2008), possibly due to the effects of both strict emission controls and favorable meteorological conditions.

  • highly time and size resolved characterization of submicron aerosol particles in beijing using an aerodyne aerosol mass spectrometer
    Atmospheric Environment, 2010
    Co-Authors: Junying Sun, Yele Sun, Q Zhang, Manjula R Canagaratna, John T Jayne, Yangmei Zhang, Xiaochun Zhang, Xiaoye Zhang, Douglas R Worsnop
    Abstract:

    Abstract Atmospheric aerosols are a major pollutant in Beijing—a megacity in China. To achieve a better understanding of the characteristics, sources and processes of aerosols in Beijing, an Aerodyne Aerosol Mass Spectrometer (AMS) was deployed at an urban site in July 2006 to obtain size-resolved chemical composition of non-refractory submicron particles (NR-PM 1 ) at 5 min resolution. During this study, NR-PM 1 was on average composed of 25% sulfate, 22% nitrate, 16% ammonium, 1.4% chloride and 35% of organic aerosol (OA) species. The average size distributions of sulfate, nitrate and ammonium were very similar and characterized by a prominent accumulation mode peaking at D va  ≈ 600 nm. The average size distribution of OA was significantly broader due to the presence of an ultrafine mode. Multivariate analysis of the AMS organic spectra with Positive Matrix Factorization (PMF) identified a hydrocarbon-like OA (HOA) and two oxygenated OA (OOA) components. The HOA component likely corresponded to primary OA material associated with combustion-related emissions. The two OOA components, which likely corresponded to more oxidized (OOA I) and less oxidized (OOA II) secondary OA materials, accounted for 45 ± 16% and 16 ± 7.2%, respectively, of the observed OA mass. OOA I correlated well with sulfate while OOA II correlated well with nitrate. The particle loading, composition and size distributions observed during this campaign were highly variable. Backtrajectory analysis indicates that this variability correlated with the varying impacts of regional and local sources and processes.

  • hydrocarbon like and oxygenated organic aerosols in pittsburgh insights into sources and processes of organic aerosols
    Atmospheric Chemistry and Physics, 2005
    Co-Authors: Q Zhang, Manjula R Canagaratna, D R Worsnop, Jose L Jimenez
    Abstract:

    A recently developed algorithm (Zhang et al., 2005) has been applied to deconvolve the mass spectra of organic aerosols acquired with the Aerosol Mass Spectrom- eter (AMS) in Pittsburgh during September 2002. The re- sults are used here to characterize the mass concentrations, size distributions, and mass spectra of hydrocarbon-like and oxygenated organic aerosol (HOA and OOA, respectively). HOA accounts for 34% of the measured organic aerosol mass and OOA accounts for 66%. The mass concentra- tions of HOA demonstrate a prominent diurnal profile that peaks in the morning during the rush hour and decreases with the rise of the boundary layer. The diurnal profile of OOA is relatively flat and resembles those of SO 2 and NH + . The size distribution of HOA shows a distinct ul- trafine mode that is commonly associated with fresh emis- sions while OOA is generally concentrated in the accumu- lation mode and appears to be mostly internally mixed with the inorganic ions, such as SO 2 and NH + . These observa- tions suggest that HOA is likely primary aerosol from local, combustion-related emissions and that OOA is secondary or- ganic aerosol (SOA) influenced by regional contributions. There is strong evidence of the direct correspondence of OOA to SOA during an intense new particle formation and growth event, when condensational growth of OOA was ob- served. The fact that the OOA mass spectrum from this event is very similar to that from the entire study suggests that the majority of OOA in Pittsburgh is likely SOA. O3 appears to be a poor indicator for OOA concentration while SO 2 is a relatively good surrogate for this dataset. Since the diurnal averages of HOA track those of CO during day time, oxida- tion/aging of HOA appears to be very small on the time scale of several hours. Based on extracted mass spectra and the likely elemental compositions of major m/z's, the organic mass to organic carbon ratios (OM:OC) of HOA and OOA are estimated at 1.2 and 2.2µg/µgC, respectively, leading to an average OM:OC ratio of 1.8 for submicron OA in Pitts- burgh during September. The C:O ratio of OOA is estimated at 1:0.8. The carbon contents in HOA and OOA estimated accordingly correlate well to primary and secondary organic carbon, respectively, estimated by the OC/EC tracer tech- nique (assuming POC-to-EC ratio=1). In addition, the total carbon concentrations estimated from the AMS data agree well with those measured by the Sunset Laboratory Carbon analyzer (r 2 =0.87; slope=1.01±0.11). Our results represent the first direct estimate of the OM:OC ratio from highly time- resolved chemical composition measurements.

  • Hydrocarbon-like and oxygenated organic aerosols in Pittsburgh: insights into sources and processes of organic aerosols
    Atmospheric Chemistry and Physics Discussions, 2005
    Co-Authors: Q Zhang, D R Worsnop, M. R. Canagaratna, J L Jimenez
    Abstract:

    A recently developed algorithm (Zhang et al., 2005) has been applied to deconvolve the mass spectra of organic aerosols acquired with the Aerosol Mass Spectrometer (AMS) in Pittsburgh during September 2002. The results are used here to characterize the mass concentrations, size distributions, and mass spectra of hydrocarbon-like and oxygenated organic aerosol (HOA and OOA, respectively). HOA accounts for 34% of the measured organic aerosol mass and OOA accounts for 66%. The mass concentrations of HOA demonstrate a prominent diurnal profile that peaks in the morning during the rush hour and decreases with the rise of the boundary layer. The diurnal profile of OOA is relatively flat and resembles those of SO42? and NH4+. The size distribution of HOA shows a distinct ultrafine mode that is commonly associated with fresh emissions while OOA is generally concentrated in the accumulation mode and appears to be mostly internally mixed with the inorganic ions, such as SO42? and NH4+. These observations suggest that HOA is likely primary aerosol from local, combustion-related emissions and that OOA is secondary organic aerosol (SOA) influenced by regional contributions. There is strong evidence of the direct correspondence of OOA to SOA during an intense new particle formation and growth event, when condensational growth of OOA was observed. The mass spectrum of OOA of this new particle formation event is very similar to the OOA spectrum of the entire study, which strongly suggests that most OOA during this study is SOA. O3 appears to be a poor indicator for SOA concentration while SO42? is a relatively good surrogate for this dataset. Since the diurnal averages of HOA tightly track those of CO during day time, oxidation/aging of HOA appears to be very small on the time scale of several hours. Based on extracted mass spectra and the likely elemental compositions of major m/z's, the organic mass to organic carbon ratios (OM:OC) of HOA and OOA are estimated at 1.2 and 2.2 ?g/?g C, respectively, leading to an average OM:OC ratio of 1.8 for submicron OA in Pittsburgh during September. The C:O ratio of OOA is estimated at 1:0.8. The carbon contents in HOA and OOA calculated accordingly correlate well to primary and secondary organic carbon, respectively, estimated by the OC/EC tracer technique (assuming POC-to-EC ratio=1). In addition, the total carbon concentrations calculated from the AMS data agree well with those measured by the Sunset Laboratory Carbon analyzer (r2=0.87; slope=1.01±0.11).

Andre S H Prevot - One of the best experts on this subject based on the ideXlab platform.

  • sofi an igor based interface for the efficient use of the generalized multilinear engine me 2 for the source apportionment me 2 application to aerosol mass spectrometer data
    Atmospheric Measurement Techniques, 2013
    Co-Authors: Francesco Canonaco, Jay G Slowik, Monica Crippa, U Baltensperger, Andre S H Prevot
    Abstract:

    Abstract. Source apportionment using the bilinear model through a multilinear engine (ME-2) was successfully applied to non-refractory organic aerosol (OA) mass spectra collected during the winter of 2011 and 2012 in Zurich, Switzerland using the aerosol chemical speciation monitor (ACSM). Five factors were identified: low-volatility oxygenated OA (LV-OOA), semivolatile oxygenated OA (SV-OOA), hydrocarbon-like OA (HOA), cooking OA (COA) and biomass burning OA (BBOA). A graphical user interface SoFi (Source Finder) was developed at PSI in order to facilitate the testing of different rotational techniques available within the ME-2 engine by providing a priori factor profiles for some or all of the expected factors. ME-2 was used to test the positive matrix factorization (PMF) model, the fully constrained chemical mass balance (CMB) model, and partially constrained models utilizing a values and pulling equations. Within the set of model solutions determined to be environmentally reasonable, BBOA and SV-OOA factor mass spectra and time series showed the greatest variability. This variability represents the uncertainty in the model solution and indicates that analysis of model rotations provides a useful approach for assessing the uncertainty of bilinear source apportionment models.

  • source apportionment of submicron organic aerosols at an urban site by factor analytical modelling of aerosol mass spectra
    Atmospheric Chemistry and Physics, 2007
    Co-Authors: V A Lanz, M R Alfarra, Urs Baltensperger, B Buchmann, Christoph Hueglin, Andre S H Prevot
    Abstract:

    Submicron ambient aerosol was characterized in summer 2005 at an urban background site in Zurich, Switzer- land, during a three-week measurement campaign. Highly time-resolved samples of non-refractory aerosol components were analyzed with an Aerodyne aerosol mass spectrometer (AMS). Positive matrix factorization (PMF) was used for the first time for aerosol mass spectra to identify the main com- ponents of the total organic aerosol and their sources. The PMF retrieved factors were compared to measured reference mass spectra and were correlated with tracer species of the aerosol and gas phase measurements from collocated instru- ments. Six factors were found to explain virtually all vari- ance in the data and could be assigned either to sources or to aerosol components such as oxygenated organic aerosol (OOA). Our analysis suggests that at the measurement site only a small (<10%) fraction of organic PM1 originates from freshly emitted fossil fuel combustion. Other primary sources identified to be of similar or even higher importance are charbroiling (10-15%) and wood burning ( 10%). The fraction of all identified primary sources is considered as pri- mary organic aerosol (Poa). This interpretation is supported by calculated ratios of the modelled Poa and measured pri- mary pollutants such as elemental carbon (EC), NOx, and CO, which are in good agreement to literature values. A high fraction (60-69%) of the measured organic aerosol mass is OOA which is interpreted mostly as secondary organic aerosol (SOA). This oxygenated organic aerosol can be sepa- rated into a highly aged fraction, OOA I, (40-50%) with low volatility and a mass spectrum similar to fulvic acid, and a more volatile and probably less processed fraction, OOA II (on average 20%). This is the first publication of a multiple component analysis technique to AMS organic spectral data and also the first report of the OOA II component.

Jose L Jimenez - One of the best experts on this subject based on the ideXlab platform.

  • chemical composition sources and aging process of submicron aerosols in beijing contrast between summer and winter
    Journal of Geophysical Research, 2016
    Co-Authors: Jose L Jimenez, Weiwei Hu, Min Hu, Wei Hu, B Yuan, Wentai Chen, Ming Wang
    Abstract:

    To investigate the seasonal characteristics of submicron aerosol (PM1) in Beijing urban areas, a high-resolution time-of-flight aerosol-mass-spectrometer (HR-ToF-AMS) was utilized at an urban site in summer (August to September 2011) and winter (November to December 2010), coupled with multiple state of the art online instruments. The average mass concentrations of PM1 (60–84 µg m−3) and its chemical compositions in different campaigns of Beijing were relatively consistent in recent years. In summer, the daily variations of PM1 mass concentrations were stable and repeatable. Eighty-two percent of the PM1 mass concentration on average was composed of secondary species, where 62% is secondary inorganic aerosol and 20% secondary organic aerosol (SOA). In winter, PM1 mass concentrations changed dramatically because of the different meteorological conditions. The high average fraction (58%) of primary species in PM1 including primary organic aerosol (Poa), black carbon, and chloride indicates primary emissions usually played a more important role in the winter. However, aqueous chemistry resulting in efficient secondary formation during occasional periods with high relative humidity may also contribute substantially to haze in winter. Results of past OA source apportionment studies in Beijing show 45–67% of OA in summer and 22–50% of OA in winter can be composed of SOA. Based on the source apportionment results, we found 45% Poa in winter and 61% Poa in summer are from nonfossil sources, contributed by cooking OA in both seasons and biomass burning OA (BBOA) in winter. Cooking OA, accounting for 13–24% of OA, is an important nonfossil carbon source in all years of Beijing and should not be neglected. The fossil sources of Poa include hydrocarbon-like OA from vehicle emissions in both seasons and coal combustion OA (CCOA) in winter. The CCOA and BBOA were the two main contributors (57% of OA) for the highest OA concentrations (>100 µg m−3) in winter. The Poa/ΔCO ratios in winter and summer are 11 and 16 µg m−3 ppm−1, respectively, similar to ratios from western cities. Higher OOA/Ox (= NO2 + O3) ratio (0.49 µg m−3 ppb−1) in winter study than these ratios from western cities (0.03–0.16 µg m−3 ppb−1) was observed, which may be due to the aqueous reaction or extra SOA formation contributed by semivolatile organic compounds from various primary sources (e.g., BBOA or CCOA) in Beijing. The evolution of oxygen to carbon ratio (O/C) with photochemical age allows to estimate an equivalent rate constant for chemical aging of OA in summer as kOH ~ 4.1 × 10−12 cm3 molecule−1 s−1, which is of the same order as obtained in other anthropogenic influenced areas and may be useful for OA modeling.

  • hydrocarbon like and oxygenated organic aerosols in pittsburgh insights into sources and processes of organic aerosols
    Atmospheric Chemistry and Physics, 2005
    Co-Authors: Q Zhang, Manjula R Canagaratna, D R Worsnop, Jose L Jimenez
    Abstract:

    A recently developed algorithm (Zhang et al., 2005) has been applied to deconvolve the mass spectra of organic aerosols acquired with the Aerosol Mass Spectrom- eter (AMS) in Pittsburgh during September 2002. The re- sults are used here to characterize the mass concentrations, size distributions, and mass spectra of hydrocarbon-like and oxygenated organic aerosol (HOA and OOA, respectively). HOA accounts for 34% of the measured organic aerosol mass and OOA accounts for 66%. The mass concentra- tions of HOA demonstrate a prominent diurnal profile that peaks in the morning during the rush hour and decreases with the rise of the boundary layer. The diurnal profile of OOA is relatively flat and resembles those of SO 2 and NH + . The size distribution of HOA shows a distinct ul- trafine mode that is commonly associated with fresh emis- sions while OOA is generally concentrated in the accumu- lation mode and appears to be mostly internally mixed with the inorganic ions, such as SO 2 and NH + . These observa- tions suggest that HOA is likely primary aerosol from local, combustion-related emissions and that OOA is secondary or- ganic aerosol (SOA) influenced by regional contributions. There is strong evidence of the direct correspondence of OOA to SOA during an intense new particle formation and growth event, when condensational growth of OOA was ob- served. The fact that the OOA mass spectrum from this event is very similar to that from the entire study suggests that the majority of OOA in Pittsburgh is likely SOA. O3 appears to be a poor indicator for OOA concentration while SO 2 is a relatively good surrogate for this dataset. Since the diurnal averages of HOA track those of CO during day time, oxida- tion/aging of HOA appears to be very small on the time scale of several hours. Based on extracted mass spectra and the likely elemental compositions of major m/z's, the organic mass to organic carbon ratios (OM:OC) of HOA and OOA are estimated at 1.2 and 2.2µg/µgC, respectively, leading to an average OM:OC ratio of 1.8 for submicron OA in Pitts- burgh during September. The C:O ratio of OOA is estimated at 1:0.8. The carbon contents in HOA and OOA estimated accordingly correlate well to primary and secondary organic carbon, respectively, estimated by the OC/EC tracer tech- nique (assuming POC-to-EC ratio=1). In addition, the total carbon concentrations estimated from the AMS data agree well with those measured by the Sunset Laboratory Carbon analyzer (r 2 =0.87; slope=1.01±0.11). Our results represent the first direct estimate of the OM:OC ratio from highly time- resolved chemical composition measurements.

  • deconvolution and quantification of hydrocarbon like and oxygenated organic aerosols based on aerosol mass spectrometry
    Environmental Science & Technology, 2005
    Co-Authors: Q Zhang, Manjula R Canagaratna, Douglas R Worsnop, Rami M Alfarra, J D Allan, Jose L Jimenez
    Abstract:

    A new technique has been developed to deconvolve and quantify the mass concentrations of hydrocarbon-like and oxygenated organic aerosols (HOA and OOA) using highly time-resolved organic mass spectra obtained with an Aerodyne Aerosol Mass Spectrometer (AMS). This technique involves a series of multivariate linear regressions that use mass-to-charge ratios (m/z's) 57 (mostly C4H9+) and 44 (mostly CO2+)the identified AMS mass spectral tracers for HOA and OOA, respectivelyas the initial principal components. Two algorithms have been developed:  algorithm 1 is based solely on m/z 44 and m/z 57, and algorithm 2 is an iterative procedure expanded from algorithm 1. This technique was applied to the AMS organic aerosol data acquired at the EPA Pittsburgh Supersite during September 2002. The reconstructed organic concentrations (= HOA + OOA) agree well with the measured values (r2 = 0.997, slope = 0.998), and the reconstructed organic data matrix (size = 3199 time steps × 300 m/z's) explains 99% of the variance in...

  • deconvolution and quantification of hydrocarbon like and oxygenated organic aerosols based on aerosol mass spectrometry
    Environmental Science & Technology, 2005
    Co-Authors: Q Zhang, Manjula R Canagaratna, Douglas R Worsnop, Rami M Alfarra, J D Allan, H Coe, Jose L Jimenez
    Abstract:

    A new technique has been developed to deconvolve and quantify the mass concentrations of hydrocarbon-like and oxygenated organic aerosols (HOA and OOA) using highly time-resolved organic mass spectra obtained with an Aerodyne Aerosol Mass Spectrometer (AMS). This technique involves a series of multivariate linear regressions that use mass-to-charge ratios (ml/s) 57 (mostly C4H9+) and 44 (mostly CO2+)-the identified AMS mass spectral tracers for HOA and OOA, respectively-as the initial principal components. Two algorithms have been developed: algorithm 1 is based solely on m/z 44 and m/z 57, and algorithm 2 is an iterative procedure expanded from algorithm 1. This technique was applied to the AMS organic aerosol data acquired at the EPA Pittsburgh Supersite during September 2002. The reconstructed organic concentrations (= HOA + OOA) agree well with the measured values (r2 = 0.997, slope = 0.998), and the reconstructed organic data matrix (size = 3199 time steps x 300 m/z's) explains 99% of the variance in the measured time series. In addition, the extracted mass spectrum of HOA shows high similarity to those of diesel exhaust, lubricating oil, and freshly emitted traffic aerosols observed in urban areas, while the spectrum of OOA closely resembles those of aged organic aerosols sampled in rural areas and also shows similarity with the spectrum of fulvic acid- a humic-like substance that is ubiquitous in the environment and has previously been used as an analogue to represent polyacid components found in highly processed and oxidized atmospheric organic aerosols. There is evidence for the presence of a third component, although its contribution to the total organic signal appears to be small in this study. The most important result is that m/z 44 and m/z 57 are reliable AMS mass spectral "markers" that provide the "first guess" for algorithm 2 which allows the quantitative description of the organic aerosol concentration and mass spectra over a period of 16 days in a major urban area and allows the extraction of mass spectra of OOA and HOA that can be interpreted chemically. These findings indicate the potential of performing organic source apportionment on the basis of total particle mass, rather than on the basis of organic tracer compounds that contribute a small fraction of this mass.

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  • Phylogeny of Poa (Poaceae) Based on trnT–trnF Sequence Data: Major Clades and Basal Relationships
    Aliso, 2007
    Co-Authors: Lynn J. Gillespie, Annie Archambault, Robert J. Soreng
    Abstract:

    Poa, the largest genus of grasses (Poaceae) with over 500 species, occurs throughout temperate and boreal regions in both hemispheres. A phylogenetic study of Poa based on trnT-trnF chloroplast DNA sequence data is presented focusing on basal relationships, major clades, generic boundaries, and placement of putatively closely related genera. Results support the monophyly of the main lineage of Poa if subgen. Andinae is excluded and Anthochloa, Austrofestuca, Dissanthelium (at least in part), and EremoPoa are included. The main Poa clade and subgen. Andinae resolve within a strongly supported Poinae-Alopecurinae-Miliinae clade (PAM). The subdivision of Poa into five major clades, proposed based on chloroplast restriction site data, is supported by sequence data. The basal-most clade (ArcSyl) comprises Poa subgen. ArctoPoa and subgen. Poa sect. Sylvestres, two groups having disparate morphology, but similar cpDNA. The next-diverging clade (BAPO), comprising sects. Bolbophorum, Alpinae, Parodiochloa, and OchloPoa, is strongly supported and characterized by highly divergent cpDNA. The majority of Poa species and sections form a strongly supported clade comprising major clades SPOSTA. PoM, and HAMBADD. Newly reported in this study is EremoPoa as a distinct lineage positioned between this higher Poa clade and BAPO. A revised infrageneric classification of Poa comprising five subgenera is proposed. Two new subgeneric divisions of Poa are proposed: subgen. StenoPoa for the SPOSTA clade and supersect. HomaloPoa for the HAMBADD clade. The monotypic genus Anthochloa is reduced to Poa sect. Anthochloa, and its one species recognized as Poa lepidula.

  • phylogeny of Poa Poaceae based on trnt trnf sequence data major clades and basal relationships
    Aliso, 2007
    Co-Authors: Lynn J. Gillespie, Annie Archambault, Robert J. Soreng
    Abstract:

    Poa, the largest genus of grasses (Poaceae) with over 500 species, occurs throughout temperate and boreal regions in both hemispheres. A phylogenetic study of Poa based on trnT-trnF chloroplast DNA sequence data is presented focusing on basal relationships, major clades, generic boundaries, and placement of putatively closely related genera. Results support the monophyly of the main lineage of Poa if subgen. Andinae is excluded and Anthochloa, Austrofestuca, Dissanthelium (at least in part), and EremoPoa are included. The main Poa clade and subgen. Andinae resolve within a strongly supported Poinae-Alopecurinae-Miliinae clade (PAM). The subdivision of Poa into five major clades, proposed based on chloroplast restriction site data, is supported by sequence data. The basal-most clade (ArcSyl) comprises Poa subgen. ArctoPoa and subgen. Poa sect. Sylvestres, two groups having disparate morphology, but similar cpDNA. The next-diverging clade (BAPO), comprising sects. Bolbophorum, Alpinae, Parodiochloa, and OchloPoa, is strongly supported and characterized by highly divergent cpDNA. The majority of Poa species and sections form a strongly supported clade comprising major clades SPOSTA. PoM, and HAMBADD. Newly reported in this study is EremoPoa as a distinct lineage positioned between this higher Poa clade and BAPO. A revised infrageneric classification of Poa comprising five subgenera is proposed. Two new subgeneric divisions of Poa are proposed: subgen. StenoPoa for the SPOSTA clade and supersect. HomaloPoa for the HAMBADD clade. The monotypic genus Anthochloa is reduced to Poa sect. Anthochloa, and its one species recognized as Poa lepidula.

  • A Phylogenetic Analysis of the Bluegrass Genus Poa Based on cpDNA Restriction Site Data
    Systematic Botany, 2005
    Co-Authors: Lynn J. Gillespie, Robert J. Soreng
    Abstract:

    Abstract Poa, with about 575 species, is the largest genus of grasses, and has diversified throughout temperate, boreal, and arctic regions, and similar habitats through the tropics. This new phylogenetic study of Poa based on analysis of restriction site data from PCR amplified regions of chloroplast DNA (trnT-trnF, trnF-trnV, trnV-rbcL, rbcL-ORF106, trnH-trnK) expands previous sampling in the genus to where 1/5 to 1/6 of the species have been characterized for chloroplast DNA types. A broad phylogenetic structure detected in a previous study using restriction site mapping of Poa chloroplast DNA gained additional and robust support. Accounting for extended intra- and extrageneric sampling, Poa remains monophyletic if Austrofestuca and Parodiochloa are included as sections within P. subg. Poa, and if Poa subg. Andinae is removed from the genus. Two new combinations are made: Poa sect. Austrofestuca and Poa sect. Parodiochloa. This new analysis supports the recognition of five major clades within Poa: 1) A...

  • Phylogenetic relationships and infraspecific variation in Canadian Arctic Poa based on chloroplast DNA restriction site data
    Canadian Journal of Botany, 2001
    Co-Authors: Lynn J. Gillespie, Ruben Boles
    Abstract:

    Infraspecific variation and phylogenetic relationships of Canadian Arctic species of the genus Poa were studied based on chloroplast DNA (cpDNA) variation. Restriction site analysis of polymerase chain reaction amplified cpDNA was used to reexamine the status of infraspecific taxa, reconstruct phylogenetic relationships, and reexamine previous classification systems and hypotheses of relationships. Infraspecific variation was detected in three species, but only in Poa hartzii Gand. did it correspond to infraspecific taxa where recognition of subspecies ammophila at the species level is supported. Additional variation in P. hartzii ssp. hartzii is hypothesized to be the result of hybridization with Poa glauca in the High Arctic and subsequent introgression resulting in repeated transfer of P. glauca DNA. The variation in Poa pratensis L. had a geographical rather than taxonomic basis, and is hypothesized to correspond to indigenous arctic versus introduced extra-arctic populations. In P. glauca Vahl cpDNA variation was detected only in western Low Arctic and boreal populations and may represent greater variation where the species survived the Pleistocene glaciations. Cladistic parsimony analysis of cpDNA restriction site data mostly confirms recent infrageneric classification systems. Poa alpina L., along with the non-arctic Poa annua L. and Poa sect. Sylvestres, formed the basalmost clades. The remaining taxa group into two main clades: one consisting of Poa sects. Poa, HomaloPoa, MadroPoa and DiocoPoa; the second, of Poa sects. Secundae, Pandemos, Abbreviatae and StenoPoa. Poa sect. Poa, comprising Poa arctica R. Br. and P. pratensis, is a strongly supported monophyletic group, not closely related to P. alpina. Poa hartzii is confirmed as a member of a paraphyletic or weakly supported P. sect. Secundae. Poa glauca and Poa abbreviata R. Br. are distinct members within a generally unresolved Poa. sect. StenoPoa-Abbreviatae complexKey words: Poa, Canadian arctic, chloroplast DNA, restriction site analysis, infraspecific variation, phylogeny.

  • Phylogenetic relationships and infraspecific variation in Canadian Arctic Poa based on chloroplast DNA restriction site data
    Canadian Journal of Botany, 2001
    Co-Authors: Lynn J. Gillespie, Ruben L. Boles
    Abstract:

    Infraspecific variation and phylogenetic relationships of Canadian Arctic species of the genus Poa were stud- ied based on chloroplast DNA (cpDNA) variation. Restriction site analysis of polymerase chain reaction amplified cpDNA was used to reexamine the status of infraspecific taxa, reconstruct phylogenetic relationships, and reexamine previous classification systems and hypotheses of relationships. Infraspecific variation was detected in three species, but only in Poa hartzii Gand. did it correspond to infraspecific taxa where recognition of subspecies ammophila at the spe- cies level is supported. Additional variation in P. hartzii ssp. hartzii is hypothesized to be the result of hybridization with Poa glauca in the High Arctic and subsequent introgression resulting in repeated transfer of P. glauca DNA. The variation in Poa pratensis L. had a geographical rather than taxonomic basis, and is hypothesized to correspond to in- digenous arctic versus introduced extra-arctic populations. In P. glauca Vahl cpDNA variation was detected only in western Low Arctic and boreal populations and may represent greater variation where the species survived the Pleisto- cene glaciations. Cladistic parsimony analysis of cpDNA restriction site data mostly confirms recent infrageneric classi - fication systems. Poa alpina L., along with the non-arctic Poa annua L. and Poa sect. Sylvestres, formed the basalmost clades. The remaining taxa group into two main clades: one consisting of Poa sects. Poa, HomaloPoa, MadroPoa and DiocoPoa; the second, of Poa sects. Secundae, Pandemos, Abbreviatae and StenoPoa. Poa sect. Poa, comprising Poa arctica R. Br. and P. pratensis, is a strongly supported monophyletic group, not closely related to P. alpina. Poa hartzii is confirmed as a member of a paraphyletic or weakly supported P. sect. Secundae. Poa glauca and Poa abbreviata R. Br. are distinct members within a generally unresolved Poa. sect. StenoPoa-Abbreviatae complex