The nitrate radical, NO(3), is photochemically unstable but is one of the most chemically important species in the nocturnal atmosphere. It is accompanied by the presence of dinitrogen pentoxide, ...N(2)O(5), with which it is in rapid thermal equilibrium at lower tropospheric temperatures. These two nitrogen oxides participate in numerous atmospheric chemical systems. NO(3) reactions with VOCs and organic sulphur species are important, or in some cases even dominant, oxidation pathways, impacting the budgets of these species and their degradation products. These oxidative reactions, together with the ozonolysis of alkenes, are also responsible for the nighttime production and cycling of OH and peroxy (HO(2) + RO(2)) radicals. In addition, reactions of NO(3) with biogenic hydrocarbons are particularly efficient and are responsible for the production of organic nitrates and secondary organic aerosol. Heterogeneous chemistry of N(2)O(5) is one of the major processes responsible for the atmospheric removal of nitrogen oxides as well as the cycling of halogen species though the production of nitryl chloride, ClNO(2). The chemistry of NO(3) and N(2)O(5) is also important to the regulation of both tropospheric and stratospheric ozone. Here we review the essential features of this atmospheric chemistry, along with field observations of NO(3), N(2)O(5), nighttime peroxy and OH radicals, and related compounds. This review builds on existing reviews of this chemistry, and encompasses field, laboratory and modelling work spanning more than three decades.
Atmospheric brown carbon (BrC) is an important contributor to the radiative forcing of climate by organic aerosols. Because of the molecular diversity of BrC compounds and their dynamic ...transformations, it is challenging to predictively understand BrC optical properties. OH radical and O3 reactions, together with photolysis, lead to diminished light absorption and lower warming effects of biomass burning BrC. The effects of night-time aging on the optical properties of BrC aerosols are less known. To address this knowledge gap, night-time NO3 radical chemistry with tar aerosols from wood pyrolysis was investigated in a flow reactor. This study shows that the optical properties of BrC change because of transformations driven by reactions with the NO3 radical that form new absorbing species and lead to significant absorption enhancement over the ultraviolet–visible (UV-vis) range. The overnight aging increases the mass absorption coefficients of the BrC by a factor of 1.3–3.2 between 380 nm and 650 nm. Nitrated organic compounds, particularly nitroaromatics, were identified as the main products that contribute to the enhanced light absorption in the secondary BrC. Night-time aging of BrC aerosols represents an important source of secondary BrC and can have a pronounced effect on atmospheric chemistry and air pollution.
Volatile and intermediate-volatility non-methane organic gases (NMOGs) released from biomass burning were measured during
laboratory-simulated wildfires by proton-transfer-reaction time-of-flight ...mass spectrometry (PTR-ToF). We identified NMOG
contributors to more than 150 PTR ion masses using gas chromatography (GC) pre-separation with electron ionization,
H3O+ chemical ionization, and NO+ chemical ionization, an extensive literature review, and
time series correlation, providing higher certainty for ion identifications than has been previously available. Our
interpretation of the PTR-ToF mass spectrum accounts for nearly 90 % of NMOG mass detected by PTR-ToF across all fuel
types. The relative contributions of different NMOGs to individual exact ion masses are mostly similar across many fires
and fuel types. The PTR-ToF measurements are compared to corresponding measurements from open-path Fourier transform
infrared spectroscopy (OP-FTIR), broadband cavity-enhanced spectroscopy (ACES), and iodide ion chemical ionization mass
spectrometry (I− CIMS) where possible. The majority of comparisons have slopes near 1 and values of the linear
correlation coefficient, R2, of > 0.8, including compounds that are not frequently reported by PTR-MS such as
ammonia, hydrogen cyanide (HCN), nitrous acid (HONO), and propene. The exceptions include methylglyoxal and compounds that
are known to be difficult to measure with one or more of the deployed instruments. The fire-integrated emission ratios to
CO and emission factors of NMOGs from 18 fuel types are provided. Finally, we provide an overview of the chemical
characteristics of detected species. Non-aromatic oxygenated compounds are the most abundant. Furans and aromatics, while
less abundant, comprise a large portion of the OH reactivity. The OH reactivity, its major contributors, and the
volatility distribution of emissions can change considerably over the course of a fire.
The functional interpretation of genome-wide association studies (GWAS) is challenging due to the cell-type-dependent influences of genetic variants. Here, we generated comprehensive maps of ...expression quantitative trait loci (eQTLs) for 659 microdissected human kidney samples and identified cell-type-eQTLs by mapping interactions between cell type abundances and genotypes. By partitioning heritability using stratified linkage disequilibrium score regression to integrate GWAS with single-cell RNA sequencing and single-nucleus assay for transposase-accessible chromatin with high-throughput sequencing data, we prioritized proximal tubules for kidney function and endothelial cells and distal tubule segments for blood pressure pathogenesis. Bayesian colocalization analysis nominated more than 200 genes for kidney function and hypertension. Our study clarifies the mechanism of commonly used antihypertensive and renal-protective drugs and identifies drug repurposing opportunities for kidney disease.
Nighttime oxidation of biogenic volatile organic compounds (BVOCs) by nitrate radicals (NO3·) represents one of the most important interactions between anthropogenic and natural emissions, leading to ...substantial secondary organic aerosol (SOA) formation. The direct climatic effect of such SOA cannot be quantified because its optical properties and atmospheric fate are poorly understood. In this study, we generated SOA from the NO3· oxidation of a series BVOCs including isoprene, monoterpenes, and sesquiterpenes. The SOA were subjected to comprehensive online and offline chemical composition analysis using high-resolution mass spectrometry and optical properties measurements using a novel broadband (315–650 nm) cavity-enhanced spectrometer, which covers the wavelength range needed to understand the potential contribution of the SOA to direct radiative forcing. The SOA contained a significant fraction of oxygenated organic nitrates (ONs), consisting of monomers and oligomers that are responsible for the detected light absorption in the 315–400 nm range. The SOA created from β-pinene and α-humulene was further photochemically aged in an oxidation flow reactor. The SOA has an atmospheric photochemical bleaching lifetime of >6.2 h, indicating that some of the ONs in the SOA may serve as atmosphere-stable nitrogen oxide sinks or reservoirs and will absorb and scatter incoming solar radiation during the daytime.
Particle pH is a critical but poorly constrained quantity that affects many aerosol processes and properties, including aerosol composition, concentrations, and toxicity. We assess PM1 pH as a ...function of geographical location and altitude, focusing on the northeastern U.S., based on aircraft measurements from the Wintertime Investigation of Transport, Emissions, and Reactivity campaign (1 February to 15 March 2015). Particle pH and water were predicted with the ISORROPIA‐II thermodynamic model and validated by comparing predicted to observed partitioning of inorganic nitrate between the gas and particle phases. Good agreement was found for relative humidity (RH) above 40%; at lower RH observed particle nitrate was higher than predicted, possibly due to organic‐inorganic phase separations or nitrate measurement uncertainties associated with low concentrations (nitrate < 1 µg m−3). Including refractory ions in the pH calculations did not improve model predictions, suggesting they were externally mixed with PM1 sulfate, nitrate, and ammonium. Sample line volatilization artifacts were found to be minimal. Overall, particle pH for altitudes up to 5000 m ranged between −0.51 and 1.9 (10th and 90th percentiles) with a study mean of 0.77 ± 0.96, similar to those reported for the southeastern U.S. and eastern Mediterranean. This expansive aircraft data set is used to investigate causes in variability in pH and pH‐dependent aerosol components, such as PM1 nitrate, over a wide range of temperatures (−21 to 19°C), RH (20 to 95%), inorganic gas, and particle concentrations and also provides further evidence that particles with low pH are ubiquitous.
Key Points
Highly acidic aerosols (pH = 0.77 ± 0.96) for altitudes up to 5000 m in the northeastern U.S. in wintertime
Thermodynamically predicted HNO3−NO3− partitioning by ISORROPIA‐II agrees with observation above 40% RH
Particle pH should be explicitly determined to accurately assess properties impacted by aerosol acidity, such as HNO3−NO3− partitioning
Nitryl chloride (ClNO2) plays potentially important roles in atmospheric chemistry, but its abundance and effect are not fully understood due to the small number of ambient observations of ClNO2 to ...date. In late autumn 2013, ClNO2 was measured with a chemical ionization mass spectrometer (CIMS) at a mountain top (957 m above sea level) in Hong Kong. During 12 nights with continuous CIMS data, elevated mixing ratios of ClNO2 (>400 parts per trillion by volume) or its precursor N2O5 (>1000 pptv) were observed on six nights, with the highest ever reported ClNO2 (4.7 ppbv, 1 min average) and N2O5 (7.7 ppbv, 1 min average) in one case. Backward particle dispersion calculations driven by winds simulated with a mesoscale meteorological model show that the ClNO2/N2O5‐laden air at the high‐elevation site was due to transport of urban/industrial pollution north of the site. The highest ClNO2/N2O5 case was observed in a later period of the night and was characterized with extensively processed air and with the presence of nonoceanic chloride. A chemical box model with detailed chlorine chemistry was used to assess the possible impact of the ClNO2 in the well‐processed regional plume on next day ozone, as the air mass continued to downwind locations. The results show that the ClNO2 could enhance ozone by 5–16% at the ozone peak or 11–41% daytime ozone production in the following day. This study highlights varying importance of the ClNO2 chemistry in polluted environments and the need to consider this process in photochemical models for prediction of ground‐level ozone and haze.
Key Points
First observation of ClNO2 in the planetary boundary layer of China
Combined high‐resolution meteorological and measurement‐constrained chemical models in data analysis
ClNO2 enhances daytime ozone peak by 5‐16% in well‐processed PRD air
The radiative effects of biomass‐burning aerosols on regional and global scales can be substantial. Accurate modeling of the radiative effects of smoke aerosols requires wavelength‐dependent ...measurements and parameterizations of their optical properties in the UV and visible spectral ranges along with improved description of their chemical composition. To address this issue, we used a recently developed approach to retrieve the time‐ and spectral‐dependent optical properties of ambient biomass‐burning aerosols from 300 to 650 nm wavelengths during a regional nighttime bonfire festival in Israel. During the biomass burning event, the overall absorption at 400 nm increased by about 2 orders of magnitude, changing the single scattering albedo from a background level of 0.95 to 0.7. Based on the new retrieval method, we provide parameterizations of the wavelength‐dependent effective complex refractive index from 350 to 650 nm for freshly emitted and slightly aged biomass‐burning aerosols. In addition, PM2.5 filter samples were collected for detailed offline chemical analysis of the water‐soluble organics that contribute to light absorption. Nitroaromatics were identified as major organic species responsible for the increased absorption at 400 to 500 nm. Typical chromophores include 4‐nitrocatechol, 4‐nitrophenol, nitrosyringol, and nitroguaiacol; oxidation‐nitration products of methoxyphenols; and known products of lignin pyrolysis. Our findings emphasize the importance of both primary and secondary organic aerosols from biomass burning in absorption of solar radiation and in effective radiative forcing.
Plain Language Summary
The radiative effects of biomass‐burning aerosols on regional and global scales are substantial. Accurate modeling of the radiative effects of smoke aerosols requires wavelength‐dependent measurements and parameterizations of their optical properties in the UV and visible spectral ranges along with improved description of their chemical composition. To address this issue we used a recently developed approach to retrieve the time‐ and spectral‐dependent optical properties of the ambient aerosol from 300 to 650 nm wavelengths and a high‐resolution mass spectrometry analysis of fine particulate matter. We found a significant increase in aerosol light absorption in the UV‐Vis spectral range which is correlated to high levels of nitroaromatic compounds identified in the water‐soluble extracts of the filter samples. Additionally, for further applications of our results in radiative transfer models, we provide parameterizations of the wavelength‐dependent effective complex refractive index from 350 to 650 nm for freshly emitted and aged biomass‐burning aerosols.
Key Points
Evolution of the time‐ and UV‐Vis spectral‐dependent optical properties of ambient aerosols during a biomass‐burning event
Parameterizations of wavelength‐dependent effective complex refractive index of biomass‐burning aerosols
Nitration products of syringol and guaiacol identified as major brown carbon light absorbing compounds with significant absorption above 350 nm
To identify the frequency and characteristics of long-term survivors of glioblastoma.
Using all cases of glioblastoma with histopathological confirmation in the National Cancer Database from January ...1, 2004, through December 31, 2009, clinical, institutional, and treatment-related factors were evaluated with multivariable logistic regression models so as to elucidate factors independently associated with higher than 5-year overall survival after diagnosis.
A total of 48,652 patients met the inclusion criteria, with 2249 (4.6%) achieving 5-year survival. Factors associated with odds of improved 5-year overall survival in multivariable analysis were younger age, female sex, less medical comorbidities, nonwhite race, highest median income quartile, left-sided tumors and tumors outside the brainstem, and treatment with radiotherapy (P<.05 for all). The percentage of patients surviving 5 years remained relatively unchanged over the 6-year study period (P=.97).
Despite improvements in median and short-term overall survival shown in recent large clinical trials for glioblastoma, the percentage of patients with glioblastoma achieving 5-year overall survival remains low. This observation calls for the development of practice-redefining therapies and justifies the increased application of radical novel and experimental treatment paradigms for all patients with glioblastoma.
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