Low-Molecular-Weight Carboxylic Acids in the Southeastern U.S.: Formation, Partitioning, and Implications for Organic Aerosol Aging

While carboxylic acids are important components in both particle and gas phases in the atmosphere, their sources and partitioning are not fully understood. In this study, we present real-time measurements of both particle- and gas-phase concentrations for five of the most common and abundant low-molecular-weight carboxylic acids (LMWCA) in a rural region in the southeastern U.S. in Fall 2016. Through comparison with secondary organic aerosol (SOA) tracers, we find that isoprene was the most important local precursor for all five LMWCA but via different pathways. We propose that monocarboxylic acids (formic and acetic acids) were mainly formed through gas-phase photochemical reactions, while dicarboxylic acids (oxalic, malonic, and succinic acids) were predominantly from aqueous processing. Unexpectedly high concentrations of particle-phase formic and acetic acids (in the form of formate and acetate, respectively) were observed and likely the components of long-range transport organic aerosol (OA), decoupled from their gas-phase counterparts. In addition, an extraordinarily strong correlation (R² = 0.90) was observed between a particulate LMWCA and aged SOA, which we tentatively attribute to boundary layer dynamics.

Detailed Analysis of Estimated pH, Activity Coefficients, and Ion Concentrations between the Three Aerosol Thermodynamic Models

In this work, we utilize a rich set of simulated and ground-based observational data in Tianjin, China to examine and compare the differences in aerosol acidity and composition predicted by three popular thermodynamic equilibrium models: ISORROPIA II, the Extended Aerosol Inorganics Model vision IV (E-AIM IV), and the Aerosol Inorganic-Organic Mixtures Functional groups Activity Coefficients model (AIOMFAC). The species used to estimate aerosol acidity for both simulated and ambient data were NH₄⁺, Na⁺, SO₄^2-, NO₃^-, and Cl^-. For simulated data, there is good agreement between ISORROPIA II and E-AIM IV predicted acidity in the forward and metastable mode, resulting from the hydrogen ion activity coefficient (γ_(H⁺)) and the molality (m_(H⁺)) showing opposite trends. While almost all other inorganic species concentrations are found to be similar among the three models, such is not the case for the bisulfate ion (HSO₄^-), which is linked to m_(H⁺). We find that differences in predicted bisulfate between the three models primarily result from differences in the treatment of the HSO₄^- ↔ H⁺ + SO₄^2- reaction for highly acidic conditions. This difference in bisulfate is responsible for much of the difference in estimated pH for the ambient data (average pH of 3.5 for ISORROPIA II and 3.0 for E-AIM IV).

Studying the impact of radioactive charging on the microphysical evolution and transport of radioactive aerosols with the TOMAS-RC v1 framework

Radioactive charging can significantly impact the way radioactive aerosols behave, and as a result their lifetime, but such effects are neglected in predictive model studies of radioactive plumes. The objective of this work is to determine the influence of radioactive charging on the vertical transport of radioactive aerosols in the atmosphere, through its effect on coagulation and deposition, as well as quantifying the impact of this charging on aerosol lifetime. The TwO-Moment Aerosol Sectional (TOMAS) microphysical model was extended to account for radioactive charging effects on coagulation in a computationally efficient way. The expanded model, TOMAS-RC (TOMAS with Radioactive Charging effects), was then used to simulate the microphysical evolution and deposition of radioactive aerosol (containing the isotopes ¹³¹I and ¹³⁷Cs) in a number of idealized atmospheric transport experiments. Results indicate that radioactive charging can facilitate or suppress coagulation of radioactive aerosols, thus influencing the deposition patterns and total amount of radioactive aerosol mass available for long-range transport. Sensitivity simulations to uncertain parameters affirm the potential importance of radioactive charging effects. An important finding is that charging of neutral, coarse mode aerosol from background radiation can reduce coagulation rates and extend its lifetime in the atmosphere by up to a factor of 2.

Linked Response of Aerosol Acidity and Ammonia to SO2 and NO x Emissions Reductions in the United States

Large reductions of sulfur and nitrogen oxide emissions in the United States have led to considerable improvements in air quality, though recent analyses in the Southeastern United States have shown little response of aerosol pH to these reductions. This study examines the effects of reduced emissions on the trend of aerosol acidity in fine particulate matter (PM_2.5), at a nationwide scale, using ambient concentration data from three monitoring networks-the Ammonia Monitoring Network (AMoN), the Clean Air Status and Trends network (CASTNET) and the Southeastern Aerosol Research and Characterization Network (SEARCH), in conjunction with thermodynamic (ISORROPIA-II) and chemical transport (CMAQ) model results. Sulfate and ammonium experienced similar and significant decreases with little change in pH, neutralization ratio ( f = [NH₄⁺]/2[SO₄^2-] + [NO₃^-]), or nitrate. Oak Grove, MS was the only SEARCH site showing statistically significant pH changes in the Southeast region where small increases in pH (0.003-0.09 pH units/year) were observed. Of the five regions characterized using CASTNET/AMoN data, only California exhibited a statistically significant, albeit small pH increase of +0.04 pH units/year. Furthermore, statistically insignificant (α = 0.05) changes in ammonia were observed in response to emission and PM_2.5 speciation changes. CMAQ simulation results had similar responses, showing steady ammonia levels and generally low pH, with little change from 2001 to 2011.

Linked Response of Aerosol Acidity and Ammonia to SO2 and NO x Emissions Reductions in the United States

Large reductions of sulfur and nitrogen oxide emissions in the United States have led to considerable improvements in air quality, though recent analyses in the Southeastern United States have shown little response of aerosol pH to these reductions. This study examines the effects of reduced emissions on the trend of aerosol acidity in fine particulate matter (PM_2.5), at a nationwide scale, using ambient concentration data from three monitoring networks-the Ammonia Monitoring Network (AMoN), the Clean Air Status and Trends network (CASTNET) and the Southeastern Aerosol Research and Characterization Network (SEARCH), in conjunction with thermodynamic (ISORROPIA-II) and chemical transport (CMAQ) model results. Sulfate and ammonium experienced similar and significant decreases with little change in pH, neutralization ratio ( f = [NH₄⁺]/2[SO₄^2-] + [NO₃^-]), or nitrate. Oak Grove, MS was the only SEARCH site showing statistically significant pH changes in the Southeast region where small increases in pH (0.003-0.09 pH units/year) were observed. Of the five regions characterized using CASTNET/AMoN data, only California exhibited a statistically significant, albeit small pH increase of +0.04 pH units/year. Furthermore, statistically insignificant (α = 0.05) changes in ammonia were observed in response to emission and PM_2.5 speciation changes. CMAQ simulation results had similar responses, showing steady ammonia levels and generally low pH, with little change from 2001 to 2011.

On the implications of aerosol liquid water and phase separation for organic aerosol mass

Organic compounds and liquid water are major aerosol constituents in the southeast United States (SE US). Water associated with inorganic constituents (inorganic water) can contribute to the partitioning medium for organic aerosol when relative humidities or organic matter to organic carbon (OM/OC) ratios are high such that separation relative humidities (SRH) are below the ambient relative humidity (RH). As OM/OC ratios in the SE US are often between 1.8 and 2.2, organic aerosol experiences both mixing with inorganic water and separation from it. Regional chemical transport model simulations including inorganic water (but excluding water uptake by organic compounds) in the partitioning medium for secondary organic aerosol (SOA) when RH > SRH led to increased SOA concentrations,· particularly at night. Water uptake to the organic phase resulted in even greater SOA concentrations as a result of a positive feedback in which water uptake increased SOA, which further increased aerosol water and organic aerosol. Aerosol properties· such as the OM/OC and hygroscopicity parameter (κorg), were captured well by the model compared with measurements during the Southern Oxidant and Aerosol Study (SOAS) 2013. Organic nitrates from monoterpene oxidation were predicted to be the least water-soluble semivolatile species in the model, but most biogenically derived semivolatile species in the Community Multiscale Air Quality (CMAQ) model were highly water soluble and expected to contribute to water-soluble organic carbon (WSOC). Organic aerosol and SOA precursors were abundant at night, but additional improvements in daytime organic aerosol are needed to close the model-measurement gap. When taking into account deviations from ideality, including both inorganic (when RH > SRH) and organic water in the organic partitioning medium reduced the mean bias in SOA for routine monitoring networks and improved model performance compared to observations from SOAS. Property updates from this work will be released in CMAQ v5.2.

Expression of estrogen receptors in melanoma and sentinel lymph nodes; a "female" clinical entity or a possible treatment modality?

PURPOSE

The natural history of human malignant melanoma suggests that steroid hormones may affect the biological behavior of this tumor. The purpose of the current study was to investigate the specific immunostaining patterns of estrogen receptors in malignant melanomas and their sentinel lymph nodes (SLNs), as well as to examine any possible association with patients' prognosis and overall survival.

MATERIALS AND METHODS

A retrospective analysis of prospectively collected data was conducted during a 12-year period (2001-2012). Sixty patients with mean age of 54.4 ± 14.5 years diagnosed with melanomas of varying depth (Clark) and thickness (Breslow) after excision biopsy of pre-existing melanocytic lesions, were included in the study. All patients underwent wide excision of the primary tumor and SLN identification. Determination of estrogen receptor alpha (ERa) and beta (ERb) status by immunohistochemistry on tumor and nodal paraffin blocks was performed in all feasible cases.

RESULTS

ERb but not ERa was the predominant estrogen receptor found in all primary tumors and SLNs examined. The most intense ERb immunostaining was seen in negative SLNs associated with thinner, less invading melanomas. ERb expression in the primary tumor seems to correlate with the cellular microenvironment, possibly altering the process of SLN invasion.

CONCLUSIONS

ERb expression is down-regulated in aggressive melanomas with sentinel nodal metastatic disease, suggesting its possible usefulness as a surrogate marker for metastatic potential and prognosis in malignant melanoma.

Gallbladder contraction after administration of intravenous amino acids and long-chain triacylglycerols in humans

We examined the possible physiologic effects of intravenous (IV) amino acids (AAs) and long-chain triacylglycerols (LCTs) on gallbladder (GB) motility and release of cholecystokinin (CCK) on humans. GB contraction was studied in normal volunteers after administration of a fatty meal and IV infusion of AA and LCT. The GB contraction volume was calculated with ultrasound. Cholecystokinin-8 (CCK-8) and cholecystokinin-33/39 (CCK-33/39) were measured by radio-immunoassay. Administration of a fatty meal resulted in GB contraction by 60% of its basal volume and was accompanied by an increase in the serum levels of both CCK-8 and CCK-33/39. Administration of IV AA and LCT resulted in GB contraction by 17 and 37%, respectively, of its basal volume. The latter contractions were accompanied by increased levels of CCK-8 only. We conclude that IV administration of AA and LCT can result in human GB contraction and induce the release of only CCK-8. Continuous IV administration of AA and LCT for greater than 2h causes exhaustion of CCK-8 release, so that the GB returns to its initial volume.

False aneurysm of splanchnic arteries--a scintigraphic pitfall

A 99mTc-DTPA flow study fo the abdominal aorta in a 56-year old woman gave a false-positive image of an aneurysm at the site of the celiac axis or superior mesenteric artery.

An unusual encapsulated collection of urine (urinoma) in an infant with vesicoureteral reflux

We describe an unusual case of encapsulated collection of urine (urinoma) in a 7-month-old female infant. The clinical diagnosis was urinary tract infection. The retrograde cysto-urethrogram revealed grade III vesicoureteral reflux, which we believe was the cause of the urinoma. The investigation was completed with isotope and ultrasound studies. High pressure reflux was the cause of the urine extravasation in the perirenal space.