5 research outputs found
Organosulfates in Atlanta, Georgia: anthropogenic influences on biogenic secondary organic aerosol formation
Organosulfates are secondary organic aerosol (SOA) products that form from
reactions of volatile organic compounds (VOC), such as isoprene, in the
presence of sulfate that is primarily emitted by fossil fuel combustion. This
study examines the anthropogenic influence on biogenic organosulfate
formation at an urban site in Atlanta, Georgia (GA) in the southeastern
United States (US). Organosulfates were analyzed in fine particulate matter
(PM2.5) collected during August 2015 in Atlanta using hydrophilic
interaction liquid chromatography (HILIC), tandem mass spectrometry (MS/MS),
and high-resolution time-of-flight (ToF) mass spectrometry. By their MS/MS
response, 32 major organosulfate species were identified, selected species
were quantified, and other species were semi-quantified using surrogate
standards. Organosulfates accounted for 16.5 % of PM2.5 organic carbon
(OC). Isoprene-derived organosulfates were the most abundant, dominated by
methyltetrol sulfate which accounted for 12.6 % of PM2.5 OC.
Together, the isoprene-derived organosulfates accounted for the majority of
the isoprene-derived SOA that had been previously observed in Atlanta, but
had not been identified at the molecular level. Other major species included
seven monoterpene-derived organosulfates, five diesel and/or
biodiesel-derived organosulfates, and three new organosulfates that are also
expected to derive from isoprene. Organosulfate species and concentrations in
Atlanta were compared to those in a rural forested site in Centreville,
Alabama (AL) during summer 2013, which were also dominated by
isoprene-derived organosulfates. In Atlanta, isoprene-derived organosulfate
concentrations were 2–6 times higher and accounted for twice as much
OC. The greatest enhancement in concentration was observed for
2-methylglyceric acid sulfate whose formation is enhanced in the presence of
nitrogen oxides (NO and NO2; NOx) and is a tracer for isoprene
high-NOx SOA. The isoprene-derived organosulfates indicated a stronger
influence of NOx in Atlanta compared to Centreville. Overall, these
results suggest that SOA in the southeastern US can be reduced by controlling
NOx and SO2 emissions from fossil fuel combustion. This study gives
insights into the major organosulfate species that should be targets for
future measurements in urban environments and standard development.</p
Source apportionment of fine particulate matter in Houston, Texas: insights to secondary organic aerosols
Online and offline measurements of ambient particulate matter (PM) near the
urban and industrial Houston Ship Channel in Houston, Texas, USA, during May
2015 were utilized to characterize its chemical composition and to evaluate
the relative contributions of primary, secondary, biogenic, and anthropogenic
sources. Aerosol mass spectrometry (AMS) on nonrefractory PM1 (PM ≤
1 µm) indicated major contributions from sulfate (averaging
50 % by mass), organic aerosol (OA, 40 %), and ammonium (14 %).
Positive matrix factorization (PMF) of AMS data categorized OA on average as
22 % hydrocarbon-like organic aerosol (HOA), 29 % cooking-influenced
less-oxidized oxygenated organic aerosol (CI-LO-OOA), and 48 %
more-oxidized oxygenated organic aerosol (MO-OOA), with the latter two
sources indicative of secondary organic aerosol (SOA). Chemical analysis of
PM2.5 (PM ≤ 2.5 µm) filter samples agreed that organic
matter (35 %) and sulfate (21 %) were the most abundant components.
Organic speciation of PM2.5 organic carbon (OC) focused on molecular
markers of primary sources and SOA tracers derived from biogenic and
anthropogenic volatile organic compounds (VOCs). The sources of PM2.5 OC
were estimated using molecular marker-based positive matric factorization
(MM-PMF) and chemical mass balance (CMB) models. MM-PMF resolved nine factors
that were identified as diesel engines (11.5 %), gasoline engines
(24.3 %), nontailpipe vehicle emissions (11.1 %), ship emissions
(2.2 %), cooking (1.0 %), biomass burning (BB, 10.6 %), isoprene
SOA (11.0 %), high-NOx anthropogenic SOA (6.6 %),
and low-NOx anthropogenic SOA (21.7 %). Using available
source profiles, CMB apportioned 41 % of OC to primary fossil sources
(gasoline engines, diesel engines, and ship emissions), 5 % to BB,
15 % to SOA (including 7.4 % biogenic and 7.6 % anthropogenic),
and 39 % to other sources that were not included in the model and are
expected to be secondary.This study presents the first application of in situ AMS-PMF, MM-PMF, and
CMB for OC source apportionment and the integration of these methods to
evaluate the relative roles of biogenic, anthropogenic, and BB-SOA. The three
source apportionment models agreed that ∼  50 % of OC is associated
with primary emissions from fossil fuel use, particularly motor vehicles.
Differences among the models reflect their ability to resolve sources based
upon the input chemical measurements, with molecular marker-based methods
providing greater source specificity and resolution for minor sources. By
combining results from MM-PMF and CMB, BB was estimated to contribute
11 % of OC, with 5 % primary emissions and 6 % BB-SOA. SOA was
dominantly anthropogenic (28 %) rather than biogenic (11 %) or
BB-derived. The three-model approach
demonstrates significant contributions of anthropogenic SOA to fine PM. More
broadly, the findings and methodologies presented herein can be used to
advance local and regional understanding of anthropogenic contributions to
SOA.</p
May Measurement Month 2018: a pragmatic global screening campaign to raise awareness of blood pressure by the International Society of Hypertension
Aims
Raised blood pressure (BP) is the biggest contributor to mortality and disease burden worldwide and fewer than half of those with hypertension are aware of it. May Measurement Month (MMM) is a global campaign set up in 2017, to raise awareness of high BP and as a pragmatic solution to a lack of formal screening worldwide. The 2018 campaign was expanded, aiming to include more participants and countries.
Methods and results
Eighty-nine countries participated in MMM 2018. Volunteers (≥18 years) were recruited through opportunistic sampling at a variety of screening sites. Each participant had three BP measurements and completed a questionnaire on demographic, lifestyle, and environmental factors. Hypertension was defined as a systolic BP ≥140 mmHg or diastolic BP ≥90 mmHg, or taking antihypertensive medication. In total, 74.9% of screenees provided three BP readings. Multiple imputation using chained equations was used to impute missing readings. 1 504 963 individuals (mean age 45.3 years; 52.4% female) were screened. After multiple imputation, 502 079 (33.4%) individuals had hypertension, of whom 59.5% were aware of their diagnosis and 55.3% were taking antihypertensive medication. Of those on medication, 60.0% were controlled and of all hypertensives, 33.2% were controlled. We detected 224 285 individuals with untreated hypertension and 111 214 individuals with inadequately treated (systolic BP ≥ 140 mmHg or diastolic BP ≥ 90 mmHg) hypertension.
Conclusion
May Measurement Month expanded significantly compared with 2017, including more participants in more countries. The campaign identified over 335 000 adults with untreated or inadequately treated hypertension. In the absence of systematic screening programmes, MMM was effective at raising awareness at least among these individuals at risk
Evaluation of anthropogenic secondary organic aerosol tracers from aromatic hydrocarbons
Products of secondary organic aerosol (SOA) from aromatic
volatile organic compounds (VOCs) – 2,3-dihydroxy-4-oxopentanoic acid,
dicarboxylic acids, nitromonoaromatics, and furandiones – were evaluated for
their potential to serve as anthropogenic SOA tracers with respect to their
(1) ambient concentrations and detectability in PM<sub>2.5</sub> in Iowa City, IA,
USA; (2) gas–particle partitioning behaviour; and (3) source specificity by
way of correlations with primary and secondary source tracers and literature
review. A widely used tracer for toluene-derived SOA,
2,3-dihydroxy-4-oxopentanoic acid was only detected in the particle phase
(<i>F</i><sub>p</sub> = 1) at low but consistently measurable ambient
concentrations (averaging 0.3 ng m<sup>−3</sup>). Four aromatic dicarboxylic acids
were detected at relatively higher concentrations (9.1–34.5 ng m<sup>−3</sup>),
of which phthalic acid was the most abundant. Phthalic acid had a low
particle-phase fraction (<i>F</i><sub>p</sub> = 0.26) likely due to
quantitation interferences from phthalic anhydride, while 4-methylphthalic
acid was predominantly in the particle phase (<i>F</i><sub>p</sub> = 0.82).
Phthalic acid and 4-methylphthalic acid were both highly correlated with
2,3-dihydroxy-4-oxopentanoic acid (<i>r</i><sub>s</sub> = 0.73, <i>p</i> = 0.003;
<i>r</i><sub>s</sub> = 0.80, <i>p</i> < 0.001, respectively), suggesting that they were
derived from aromatic VOCs. Isophthalic and terephthalic acids, however, were
detected only in the particle phase (<i>F</i><sub>p</sub> = 1), and
correlations suggested association with primary emission sources.
Nitromonoaromatics were dominated by particle-phase concentrations of
4-nitrocatechol (1.6 ng m<sup>−3</sup>) and 4-methyl-5-nitrocatechol
(1.6 ng m<sup>−3</sup>) that were associated with biomass burning. Meanwhile,
4-hydroxy-3-nitrobenzyl alcohol was detected in a lower concentration
(0.06 ng m<sup>−3</sup>) in the particle phase only (<i>F</i><sub>p</sub> = 1) and is
known as a product of toluene photooxidation. Furandiones in the atmosphere
have only been attributed to the photooxidation of aromatic hydrocarbons;
however the substantial partitioning toward the gas phase
(<i>F</i><sub>p</sub> ≤ 0.16) and their water sensitivity limit their application as tracers.
The outcome of this study is the demonstration that
2,3-dihydroxy-4-oxopentanoic acid, phthalic acid, 4-methylphthalic acid, and
4-hydroxy-3-nitrobenzyl alcohol are good candidates for tracing SOA from
aromatic VOCs