The particle phase state is a key
factor for determining gas particle
partitioning, particle reactive gas uptake, and multiphase chemical
reactions, with associated links to secondary aerosol formation. In
this study, the particle phase state was investigated by measuring
particle rebound fraction f in the highly polluted
atmosphere of Beijing, China. The particle phase state was sensitive
to ambient relative humidity (RH). The particles changed from rebounding
to adhering when the RH increased above 60%, suggesting a transition
from the semisolid to liquid state. This transition RH was below the
deliquescence RH of both (NH4)2SO4 and NH4NO3. Submicrometer particles were in
the liquid state during heavy haze episodes. This might be because
the elevated RH and inorganic fraction in particles resulted in an
increase in aerosol liquid water content. The transition to a liquid
phase state, marking the beginning of the haze episode, might kick
off a positive feedback loop. The liquid particles might readily take
up pollutants that then react to form inorganics, thereby further
increasing the rate of water uptake. We propose that the liquid phase
state facilitates the mass transfer and multiphase reactions of the
particles, thereby accelerating secondary particle growth in haze
over the North China Plain.
Particle phase state
plays a key role in gas-particle partitioning,
heterogeneous and multiphase reactions, and secondary aerosol formation.
In this work, the rebound fraction and chemical composition of submicron
particles were simultaneously measured to investigate the particle
phase state and its link to chemical composition in a subtropical
coastal urban city (Shenzhen, China). Submicron particles were found
to be in the liquid state for most of the measurement period in spring.
During the sampling time, both high relative humidity (RH, ranged
from 40% to 93%) and inorganic mass fraction in particles (62.6 ±
12.4% of dry particles, on average) resulted in abundant aerosol liquid
water (43 ± 6% in the wet PM1, on average), which
may liquefy the particles. Considering the high frequency of ambient
RH > 60% and large inorganic mass fraction in aerosol particles,
we
deduced that particles were in the liquid state throughout the year
in coastal urban areas, where this study was performed. The liquid
phase particles may accelerate the mass transfer of reactive trace
gases and multiphase reactions, thereby enhanced secondary aerosol
formation, further resulting in a rapid growth in aerosol mass. Our
work suggested that in regions heavily impacted by SO2 and
NO
x
emissions, especially in developing
countries, the presence of inorganics could significantly impact the
phase state of ambient aerosol particles, and thus the mixing state
of inorganic and organic matter should be taken into account for the
investigation of the aerosol phase state in urban environments.
Naphthalene
(Nap) and methylnaphthalene (MN) are the most abundant
polycyclic aromatic hydrocarbons (PAHs) in atmosphere and have been
proposed to be important precursors of anthropogenic secondary organic
aerosol (SOA) derived from laboratory chamber experiments. In this
study, atmospheric Nap/MN and their gas-phase photooxidation products
were quantified by a Proton Transfer Reaction-Quadrupole interface
Time-of-Flight Mass Spectrometer (PTR-QiTOF) during the 2016 winter
in Beijing. Phthalic anhydride, a late generation product from Nap
under high-NO
x
conditions, appeared to
be more prominent than 2-formylcinnamaldehyde (early generation product),
possibly due to more sufficient oxidation during the haze. 1,2-Phthalic
acid (1,2-PhA), the hydrated form of phthalic anhydride, was capable
of partitioning into aerosol phase and served as a tracer to explore
the contribution of Nap to ambient SOA. The measured fraction in particle
phase (F
p) of 1,2-PhA averaged at 73 ±
13% with OA mass loadings of 52.5–87.8 μg/m3, lower than the value predicted by the absorptive partitioning model
(100%). Using tracer product-based and precursor consumption-based
methods, 2-ring PAHs (Nap and MN) were estimated to produce 14.9%
(an upper limit) of the SOA formed in the afternoon during the wintertime
haze, suggesting a comparable contribution of Nap and MN with
monocyclic-aromatics on urban SOA formation.
Coronary
heart disease (CHD) threatens human health. The discovery
and assessment of potential biometabolic markers for different syndrome
types of CHD may contribute to decipher pathophysiological mechanisms
and identify new targets for diagnosis and treatment. On the basis
of UPLC-Q-TOF/MS metabolomics technology, urine samples of 1072 participants
from nine centers, including normal control, phlegm and blood stasis
(PBS) syndrome and Qi and Yin deficiency (QYD) syndrome, and other
syndromes of CHD, were conducted to find biomarkers. Among them, the
discovery set (n = 125) and the test set (n = 337) were used to identify and validate biomarkers,
and the validation set (n = 610) was used for the
application and evaluation of the support vector machine (SVM) prediction
model. We discovered 15 CHD-PBS syndrome biomarkers and 12 CHD-QYD
syndrome biomarkers, and the receiver-operator characteristic (ROC)
area-under-the-curve (AUC) values of them were 0.963 and 0.990. The
established SVM model has a good diagnostic ability and can well distinguish
the two syndromes of CHD with a high predicted accuracy >98.0%.
The
discovery of biomarkers and metabolic pathways in different syndrome
types of CHD provides a basis for the diagnosis and evaluation of
CHD, thereby improving the accurate diagnosis and precise treatment
level of Chinese medicine.
Ginkgo tea is a kind of health food produced from Ginkgo biloba leaves. The market of Ginkgo tea encountered many difficulties because of its bad palatability and vague function statement. In this study, two kinds of glycosidase were used to improve the flavor of Ginkgo tea, and three kinds of bioactivities were selected to investigate the health care function of the tea infusion. The aroma components extracted by headspace absorb (HSA) method during the making of Ginkgo tea were analyzed by GC-MS. The flavonoids and ginkgolides released into the tea infusion were studied by HPLC. A combination of β-glucosidase (β-G) and α-rhamnosidase (α-R) was applied during the making of the tea. The contents of characteristic aroma components and the release of total flavonoids and ginkgolides were increased significantly by adding β-G and α-R. The composition of flavone glycosides was changed greatly. The free radical scavenging, inhibition of inflammatory cell activation, and tumor cytotoxicity activities of the tea were demonstrably improved. According to the release of active components, Ginkgo tea can be brewed repeatedly for at least three times. The enzymes used here show potential application prospects in the making of Ginkgo tea or tea drink to get higher contents of flavonoids, ginkgolides, and aroma components.
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