10 research outputs found
Changes in PM2.5 concentrations and their sources in the US from 1990 to 2010
Significant reductions in emissions of SO2, NOx, volatile organic compounds (VOCs), and primary particulate matter (PM) took place in the US from 1990 to 2010. We evaluate here our understanding of the links between these emissions changes and corresponding changes in concentrations and health outcomes using a chemical transport model, the Particulate Matter Comprehensive Air Quality Model with Extensions (PMCAMx), for 1990, 2001, and 2010. The use of the Particle Source Apportionment Algorithm (PSAT) allows us to link the concentration reductions to the sources of the corresponding primary and secondary PM. The reductions in SO2 emissions (64 %, mainly from electric-generating units) during these 20 years have dominated the reductions in PM2.5, leading to a 45 % reduction in sulfate levels. The predicted sulfate reductions are in excellent agreement with the available measurements. Also, the reductions in elemental carbon (EC) emissions (mainly from transportation) have led to a 30 % reduction in EC concentrations. The most important source of organic aerosol (OA) through the years according to PMCAMx is biomass burning, followed by biogenic secondary organic aerosol (SOA). OA from on-road transport has been reduced by more than a factor of 3. On the other hand, changes in biomass burning OA and biogenic SOA have been modest. In 1990, about half of the US population was exposed to annual average PM2.5 concentrations above 20 µg m−3, but by 2010 this fraction had dropped to practically zero. The predicted changes in concentrations are evaluated against the observed changes for 1990, 2001, and 2010 in order to understand whether the model represents reasonably well the corresponding processes caused by the changes in emissions.This work was supported by the Center for Air, Climate, and Energy Solutions (CACES), which was supported under assistance agreement no. R835873 awarded by the U.S. Environmental Protection Agency and the Horizon-2020 Project REMEDIA of the European Union under grant agreement no. 874753.Peer ReviewedPostprint (published version
Saturation Vapor Pressures and Transition Enthalpies of Low-Volatility Organic Molecules of Atmospheric Relevance: From Dicarboxylic Acids to Complex Mixtures
Canine pancytopoenia in a Mediterranean region: a retrospective study of 119 cases (2005 to 2013)
Objectives: To further clarify the causes of pancytopoenia and to investigate whether underlying cause or severity were associated with survival in an area endemic for vector-borne pathogens. Methods: Retrospective review of medical records of 119 dogs with and 238 dogs without pancytopoenia. Results: Mixed-breed dogs and dogs younger than one year had higher odds of being pancytopoenic. The most common diagnoses included monocytic ehrlichiosis (n=42), leishmaniasis (n=28) and parvoviral enteritis (n=19). The mean white blood cell counts were lower in dogs with ehrlichiosis and parvoviral enteritis compared to dogs with leishmaniasis, while platelet counts were lower in ehrlichiosis compared to leishmaniasis or parvoviral enteritis. Total protein concentrations were lower in dogs with parvoviral enteritis compared to ehrlichiosis and leishmaniasis. Higher haematocrit, platelet and white cell counts were associated with better odds of survival. Clinical Significance: Infectious diseases appear to be the leading causes of canine pancytopoenia in endemic areas; severe leukopoenia (ehrlichiosis, parvoviral enteritis), thrombocytopoenia (ehrlichiosis) and hypoproteinaemia (parvoviral enteritis), represented potentially useful disease-specific diagnostic determinants. The severity of pancytopoenia significantly affects the clinical outcome. © 2017 British Small Animal Veterinary Associatio
Organic aerosol in the summertime southeastern United States: Components and their link to volatility distribution, oxidation state and hygroscopicity
The volatility distribution of the organic aerosol (OA) and its sources during the Southern Oxidant and Aerosol Study (SOAS; Centreville, Alabama) was constrained using measurements from an Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) and a thermodenuder (TD). Positive matrix factorization (PMF) analysis was applied on both the ambient and thermodenuded high-resolution mass spectra, leading to four factors: more oxidized oxygenated OA (MO-OOA), less oxidized oxygenated OA (LO-OOA), an isoprene epoxydiol (IEPOX)-related factor (isoprene-OA) and biomass burning OA (BBOA). BBOA had the highest mass fraction remaining (MFR) at 100ĝ€°C, followed by the isoprene-OA, and the LO-OOA. Surprisingly the MO-OOA evaporated the most in the TD. The estimated effective vaporization enthalpies assuming an evaporation coefficient equal to unity were 58ĝ€±ĝ€13ĝ€kJĝ€mol−1 for the LO-OOA, 89ĝ€±ĝ€10ĝ€kJĝ€mol−1 for the MO-OOA, 55ĝ€±ĝ€11ĝ€kJĝ€mol−1 for the BBOA, and 63ĝ€±ĝ€15ĝ€kJĝ€molĝ'1 for the isoprene-OA. The estimated volatility distribution of all factors covered a wide range including both semi-volatile and low-volatility components. BBOA had the lowest average volatility of all factors, even though it had the lowest Oĝ€ : ĝ€C ratio among all factors. LO-OOA was the more volatile factor and its high MFR was due to its low enthalpy of vaporization according to the model. The isoprene-OA factor had intermediate volatility, quite higher than suggested by a few other studies. The analysis suggests that deducing the volatility of a factor only from its MFR could lead to erroneous conclusions. The oxygen content of the factors can be combined with their estimated volatility and hygroscopicity to provide a better view of their physical properties. © Author(s) 2018
Estimation of the volatility distribution of organic aerosol combining thermodenuder and isothermal dilution measurements
A method is developed following the work of Grieshop et al. (2009) for the
determination of the organic aerosol (OA) volatility distribution combining
thermodenuder (TD) and isothermal dilution measurements. The approach was tested
in experiments that were conducted in a smog chamber using organic aerosol
(OA) produced during meat charbroiling. A TD was operated at
temperatures ranging from 25 to 250 °C with a 14 s centerline residence
time coupled to a high-resolution time-of-flight aerosol mass spectrometer
(HR-ToF-AMS) and a scanning mobility particle sizer (SMPS). In parallel, a
dilution chamber filled with clean air was used to dilute isothermally the
aerosol of the larger chamber by approximately a factor of 10. The OA mass
fraction remaining was measured as a function of temperature in the TD and
as a function of time in the isothermal dilution chamber. These two sets of
measurements were used together to estimate the volatility distribution of
the OA and its effective vaporization enthalpy and accommodation
coefficient. In the isothermal dilution experiments approximately 20 % of
the OA evaporated within 15 min. Almost all the OA evaporated in the TD at
approximately 200 °C. The resulting volatility distributions suggested
that around 60–75 % of the cooking OA (COA) at concentrations around
500 µg m−3 consisted of low-volatility organic compounds (LVOCs),
20–30 % of semivolatile organic compounds (SVOCs), and around 10 % of
intermediate-volatility organic compounds (IVOCs). The estimated effective
vaporization enthalpy of COA was 100 ± 20 kJ mol−1 and the
effective accommodation coefficient was 0.06–0.07. Addition of the dilution
measurements to the TD data results in a lower uncertainty of the estimated
vaporization enthalpy as well as the SVOC content of the OA
Volatility of organic aerosol and its components in the megacity of Paris
Using a mass transfer model and the volatility basis set, we estimate the
volatility distribution for the organic aerosol (OA) components during summer
and winter in Paris, France as part of the collaborative project MEGAPOLI.
The concentrations of the OA components as a function of temperature were
measured combining data from a thermodenuder and an aerosol mass spectrometer
(AMS) with Positive Matrix Factorization (PMF) analysis. The hydrocarbon-like
organic aerosol (HOA) had similar volatility distributions for the summer and
winter campaigns with half of the material in the saturation concentration
bin of 10 µg m<sup>−3</sup> and another 35–40 % consisting of low
and extremely low volatility organic compounds (LVOCs with effective
saturation concentrations <i>C</i>* of 10<sup>−3</sup>–0.1 µg m<sup>−3</sup> and
ELVOCs <i>C</i>* less or equal than 10<sup>−4</sup> µg m<sup>−3</sup>,
respectively). The winter cooking OA (COA) was more than an order of
magnitude less volatile than the summer COA. The low-volatility oxygenated OA
(LV-OOA) factor detected in the summer had the lowest volatility of all the
derived factors and consisted almost exclusively of ELVOCs. The volatility
for the semi-volatile oxygenated OA (SV-OOA) was significantly higher than
that of the LV-OOA, containing both semi-volatile organic components (SVOCs
with <i>C</i>* in the 1–100 µg m<sup>−3</sup> range) and LVOCs. The
oxygenated OA (OOA) factor in winter consisted of SVOCs (45 %), LVOCs
(25 %) and ELVOCs (30 %). The volatility of marine OA (MOA) was
higher than that of the other factors containing around 60 % SVOCs. The
biomass burning OA (BBOA) factor contained components with a wide range of
volatilities with significant contributions from both SVOCs (50 %) and
LVOCs (30 %). Finally, combining the bulk average O : C ratios and
volatility distributions of the various factors, our results are placed into
the two-dimensional volatility basis set (2D-VBS) framework. The OA factors
cover a broad spectrum of volatilities with no direct link between the
average volatility and average O : C of the OA components
Simulation of atmospheric organic aerosol using its volatility–oxygen-content distribution during the PEGASOS 2012 campaign
A lot of effort has been made to understand and constrain the
atmospheric aging of the organic aerosol (OA). Different parameterizations of
the organic aerosol formation and evolution in the two-dimensional volatility
basis set (2D-VBS) framework are evaluated using ground and airborne
measurements collected in the 2012 Pan-European Gas
AeroSOls-climate interaction Study (PEGASOS) field campaign in the Po
Valley (Italy). A number of chemical aging schemes are examined, taking into
account various functionalization and fragmentation pathways for biogenic and
anthropogenic OA components. Model predictions and measurements, both at the
ground and aloft, indicate a relatively oxidized OA with little average
diurnal variation. Total OA concentration and O : C ratios
are reproduced within experimental error by a number of chemical aging
schemes. Anthropogenic secondary OA (SOA) is predicted to contribute
15–25 % of the total OA, while SOA from intermediate volatility
compound oxidation contributes another 20–35 %. Biogenic SOA (bSOA) contributions varied
from 15 to 45 % depending on the modeling scheme. Primary OA contributed
around 5 % for all schemes and was comparable to the hydrocarbon-like
OA (HOA) concentrations derived from the positive matrix factorization of the
aerosol mass spectrometer (PMF-AMS) ground measurements. The average OA and
O : C diurnal variation and their vertical profiles showed
a surprisingly modest sensitivity to the assumed vaporization enthalpy for
all aging schemes. This can be explained by the interplay between the
partitioning of the semi-volatile compounds and their gas-phase chemical
aging reactions.</p
Organic aerosol in the summertime southeastern United States: components and their link to volatility distribution, oxidation state and hygroscopicity
The volatility distribution of the
organic aerosol (OA) and its sources during the Southern Oxidant and Aerosol
Study (SOAS; Centreville, Alabama) was constrained using measurements from an
Aerodyne high-resolution time-of-flight aerosol mass spectrometer
(HR-ToF-AMS) and a thermodenuder (TD). Positive matrix factorization (PMF)
analysis was applied on both the ambient and thermodenuded high-resolution
mass spectra, leading to four factors: more oxidized oxygenated OA (MO-OOA),
less oxidized oxygenated OA (LO-OOA), an isoprene epoxydiol (IEPOX)-related
factor (isoprene-OA) and biomass burning OA (BBOA). BBOA had the highest mass
fraction remaining (MFR) at 100 °C, followed by the isoprene-OA, and
the LO-OOA. Surprisingly the MO-OOA evaporated the most in the TD. The
estimated effective vaporization enthalpies assuming an evaporation
coefficient equal to unity were 58 ± 13 kJ mol−1 for the LO-OOA,
89 ± 10 kJ mol−1 for the MO-OOA, 55 ± 11 kJ mol−1
for the BBOA, and 63 ± 15 kJ mol−1 for the isoprene-OA. The
estimated volatility distribution of all factors covered a wide range
including both semi-volatile and low-volatility components. BBOA had the
lowest average volatility of all factors, even though it had the lowest
O : C ratio among all factors. LO-OOA was the more volatile factor and
its high MFR was due to its low enthalpy of vaporization according to the
model. The isoprene-OA factor had intermediate volatility, quite higher than
suggested by a few other studies. The analysis suggests that deducing the
volatility of a factor only from its MFR could lead to erroneous conclusions.
The oxygen content of the factors can be combined with their estimated
volatility and hygroscopicity to provide a better view of their physical
properties
A Systematic Review of the Treatment of Fears and Phobias Among Children with Autism Spectrum Disorders
Research indicates that fears and phobias are significantly more prevalent and emerge in response to a greater variety of stimuli, among children with autism spectrum disorders (ASD) than among their developmentally disabled or typically developing peers. Such findings are problematic given the difficulty of assessing and identifying fears or phobias among the ASD population and the challenge of identifying effective treatments for those with core diagnostic deficits in comprehension, communication, and attentional skills. The current review aimed to evaluate the literature describing interventions to treat fears, specific phobia, or social phobia among children with ASD and to identify evidence-based practice in this area. The review indicated that a variety of interventions, described as both traditional and novel, were successful in treating fearful or phobic behavioral responses to stimuli. The findings also suggest that behavioral intervention, including reinforcement, modeling, and exposure, may be considered evidence-based practice in the treatment of fears and phobias among children with ASD. However, the current research base is limited by the predominant focus on the behavioral element of the fear response, and the lack of research examining the cognitive or physiological responses during assessment or treatment