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Urban atmospheric chlorine chemistry : mechanism development, evaluation and implications
No full texttextDetailed photochemical modeling is used to guide air quality management activities around the world. These models use condensed chemical mechanisms to describe the multiphase processes that lead to chemical transformations in the atmosphere. Condensed mechanisms have generally not included the reactions of halogens, yet an expanding body of ambient observational evidence indicates that halogen chemistry, particularly chlorine chemistry, can be important in urban environments. This thesis is focused on the development, implementation, and evaluation of condensed chemical mechanisms that incorporate chlorine chemistry pathways. Gas phase reactions involving molecular chlorine and nitryl chloride (ClNO₂), as well as heterogeneous reactions involving particulate chloride species are addressed. The predictions of the modeling work presented here are compared to environmental chamber experiments and field observations.Chemical Engineerin
Inland Concentrations of Cl2 and ClNO2 in Southeast Texas Suggest Chlorine Chemistry Significantly Contributes to Atmospheric Reactivity
No full textMeasurements of molecular chlorine (Cl2), nitryl chloride (ClNO2), and dinitrogen pentoxide (N2O5) were taken as part of the DISCOVER-AQ Texas 2013 campaign with a High Resolution Time-of-Flight Chemical Ionization Mass Spectrometer (HR-ToF-CIMS) using iodide (I-) as a reagent ion. ClNO2 concentrations exceeding 50 ppt were regularly detected with peak concentrations typically occurring between 7:00 a.m. and 10:00 am. Hourly averaged Cl2 concentrations peaked daily between 3:00 p.m. and 4:00 p.m., with a 29-day average of 0.9 ± 0.3 (1σ) ppt. A day-time Cl2 source of up to 35 ppt∙h−1 is required to explain these observations, corresponding to a maximum chlorine radical (Cl•) production rate of 70 ppt∙h−1. Modeling of the Cl2 source suggests that it can enhance daily maximum O3 and RO2• concentrations by 8%–10% and 28%–50%, respectively. Modeling of observed ClNO2 assuming a well-mixed nocturnal boundary layer indicates O3 and RO2• enhancements of up to 2.1% and 38%, respectively, with a maximum impact in the early morning. These enhancements affect the formation of secondary organic aerosol and compliance with air quality standards for ozone and particulate matter
Carboxylic acids from limonene oxidation by ozone and hydroxyl radicals: insights into mechanisms derived using a FIGAERO-CIMS
No full textThis work presents the results from a flow reactor study on the formation of carboxylic acids from limonene oxidation in the presence of ozone under NOx-free conditions in the dark. A High-Resolution Time-of-Flight acetate Chemical Ionisation Mass Spectrometer (HR-ToF-CIMS) was used in combination with a Filter Inlet for Gases and AEROsols (FIGAERO) to measure the carboxylic acids in the gas and particle phases. The results revealed that limonene oxidation produced large amounts of carboxylic acids which are important contributors to secondary organic aerosol (SOA) formation. The highest 10 acids contributed 56 %–91 % to the total gas-phase signal, and the dominant gas-phase species in most experiments were C8H12O4, C9H14O4, C7H10O4 and C10H16O3. The particle-phase composition was generally more complex than the gas-phase composition, and the highest 10 acids contributed 47 %–92 % to the total signal. The dominant species in the particle phase were C8H12O5, C9H14O5, C9H12O5 and C10H16O4. The measured concentration of dimers bearing at least one carboxylic acid function in the particle phase was very low, indicating that acidic dimers play a minor role in SOA formation via ozone (O3)/hydroxyl (OH) oxidation of limonene. Based on the various experimental conditions, the acidic compositions for all experiments were modelled using descriptions from the Master Chemical Mechanism (MCM). The experiment and model provided a yield of large (C7–C10) carboxylic acid of the order of 10 % (2 %–23 % and 10 %–15 %, respectively). Significant concentrations of 11 acids, from a total of 16 acids, included in the MCM were measured with the CIMS. However, the model predictions were, in some cases, inconsistent with the measurement results, especially regarding the OH dependence. Reaction mechanisms are suggested to fill-in the knowledge gaps. Using the additional mechanisms proposed in this work, nearly 75 % of the observed gas-phase signal in our lowest concentration experiment (8.4 ppb converted, ca. 23 % acid yield) carried out under humid conditions can be understood
Supplementary material to "Characterization of organic nitrate constituents of secondary organic aerosol (SOA) from nitrate-radical-initiated oxidation of limonene using High-Resolution Chemical Ionization Mass Spectrometry"
No full textCharacterization of organic nitrate constituents of secondary organic aerosol (SOA) from nitrate-radical-initiated oxidation of limonene using High-Resolution Chemical Ionization Mass Spectrometry
No full textAbstract. The gas phase nitrate radical (NO3•) initiated oxidation of limonene can produce organic nitrate species with varying physical properties. Low-volatility products can contribute to secondary organic aerosol (SOA) formation and organic nitrates may serve as a NOx reservoir, which could be especially important in regions with high biogenic emissions. This work presents the measurement results from flow reactor studies on the reaction of NO3• and limonene using a High-Resolution Time-of-Flight Chemical Ionization Mass Spectrometer (HR-ToF-CIMS) combined with a Filter Inlet for Gases and AEROsols (FIGAERO). Major condensed-phase species were identified, and the identity and volatility properties of the most prevalent organic nitrates in the produced SOA were determined. Analysis of multiple experiments resulted in the identification of several dominant species (including C10H15NO6, C10H17NO6, C8H11NO6, C10H17NO7, and C9H13NO7) that occurred in the SOA under all conditions considered. The observed and expected (listed) products (associated with the Master Chemical Mechanism (MCM) limonene mechanism) were compared, and many non-listed species were identified. Additionally, the formation of dimers was consistently observed and these species resided almost completely in the particle phase. The identities of these species are discussed, and formation mechanisms are proposed. Cluster analysis of the desorption temperatures corresponding to the analyzed particle-phase species yielded at least five distinct groupings based on a combination of molecular weight and desorption profile. Overall, the results indicate that the oxidation of limonene by NO3• produces a complex mixture of highly oxygenated monomer and dimer products that contribute to SOA formation.
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Role of cardiac resynchronization therapy in the development of new-onset atrial fibrillation: A single-center prospective study.
No full textAlbeit several studies examined the association between cardiac resynchronization therapy (CRT) and atrial fibrillation (AF) in heart failure (HF), results are still unclear and quite conflicting. We thereby designed a single-center prospective study to determine whether CRT has a favorable effect on the incidence of new-onset AF in a homogeneous population of patients with non-ischemic idiopathic dilated cardiomyopathy and severe heart failure HF. We enrolled 58 patients, AF naïve when received CRT. After 1 year of follow-up our population was subdivided into responders (72.4%) and non (27.6%), so to compare the incidence of AF after 1, 2 and 3 years of follow-up in these two groups. Already after 1 year, there is a significant (p<0.05) difference in new-onset AF in non-responder patients respect to responders (18.2% vs 3.3%). These data are confirmed at 2 year (33.3% vs 12.2%) and 3 year (50.0% vs 15.0%) follow-up. In particular, at 3 year follow-up, non-responders have an increased risk to develop new-onset AF (OR=5.67, 95% confidence interval = 1.36-23.59, p=0.019). The present work suggests a possible favorable role of this non-pharmacological therapy, on the prevention of AF
The Propinquus Group of the Crawfish Genus Orconectes (Decapoda: Astacidae)
No full textAuthor Institution: Department of Biology, University of Virginia, CharlottesvilleNine species and subspecies assigned to the Propinquus Group, Propinquus Section, of the crawfish genus Orconectes are evaluated on the basis of 1226 specimens examined. Eleven characters are analyzed statistically and 12 more qualitatively, principally by determination of comparative frequencies. O. jeffersoni is judged specifically distinct from O. propinquus and the conspecific O. s. sanborni and O. s. erismophorous. All other taxa of the Group are distinct species. A new species from Iowa is diagnosed, but not described. Two distinct subgroups, Propinquus and Sanborni, are proposed and diagnosed. A lectotype and paralectotypes were designated for Cambarus obscurus Hagen and for Cambarus sanborni Faxon. Standard taxonomic characters in crawfishes are discussed briefly with particular reference to the Propinquus Group
Characterization of organic nitrate constituents of secondary organic aerosol (SOA) from nitrate-radical-initiated oxidation of limonene using high-resolution chemical ionization mass spectrometry
No full textThe gas-phase nitrate radical (NO3⚫)
initiated oxidation of limonene can produce organic nitrate species with
varying physical properties. Low-volatility products can contribute to
secondary organic aerosol (SOA) formation and organic nitrates may serve as a
NOx reservoir, which could be especially important in regions with high
biogenic emissions. This work presents the measurement results from flow
reactor studies on the reaction of NO3⚫ with limonene using a
High-Resolution Time-of-Flight Chemical Ionization Mass Spectrometer
(HR-ToF-CIMS) combined with a Filter Inlet for Gases and AEROsols (FIGAERO).
Major condensed-phase species were compared to those in the Master Chemical
Mechanism (MCM) limonene mechanism, and many non-listed species were
identified. The volatility properties of the most prevalent organic nitrates
in the produced SOA were determined. Analysis of multiple experiments
resulted in the identification of several dominant species (including
C10H15NO6, C10H17NO6, C8H11NO6,
C10H17NO7, and C9H13NO7) that occurred in the
SOA under all conditions considered. Additionally, the formation of dimers
was consistently observed and these species resided almost completely in the
particle phase. The identities of these species are discussed, and formation
mechanisms are proposed. Cluster analysis of the desorption temperatures
corresponding to the analyzed particle-phase species yielded at least five
distinct groupings based on a combination of molecular weight and desorption
profile. Overall, the results indicate that the oxidation of limonene by
NO3⚫ produces a complex mixture of highly oxygenated monomer
and dimer products that contribute to SOA formation
Heterogeneous production of Cl<sub>2</sub> from particulate chloride: Effects of composition and relative humidity
No full textLife-History Notes and Distributions of Crayfishes (Decapoda: Cambaridae) From the Chagrin River Basin, Northeastern Ohio)
No full textAuthor Institution: The Ohio State UniversityStream crayfishes were collected from the Chagrin River watershed during 1963-65 to determine their distributional patterns and to gather life-history information. Orconectes rusticus (Girard 1852), probably introduced into the basin in the early 1930s, was the dominant pool-dwelling species in the Chagrin River and Aurora Branch. Orconectespropinquus (Girard 1852), was restricted to the head-water portions of the main stream, the East, the Aurora Branches, and their tributaries; amplexus of this species was observed in September and March. Orconectes sanbornii sanbornii (Faxon 1884), was caught at one locality; this is the first record of its presence in the watershed. Orconectes virilis (Hagen 1870), inhabited pools of the middle and upper portions of the East Branch and its tributaries; its presence in the basin may be a remnant of a more expansive distribution. Orconectes immunis (Hagen 1870), probably a prairie relict, was captured at 2 disjunct localities in the watershed and at 3 other sites in northeastern Ohio. These are the first records of this species in these areas. Cambarus (Puncticambarus) robustus (Girard 1852), was widely distributed and abundant in the pools and riffles of the smaller tributaries and in riffles of the larger streams. An undescribed species, related to Cambarus {Cambarus) bartonii (Fabricius 1798), was captured at 8 localities. Equal sex ratios occurred in populations of 0. virilis and C. (P.) robustus, but 0. rusticus and 0. propinquus had unequal ratios of 1.30:1 and 1.49:1 (male:female), respectively
