Peroxide Content of Secondary Organic Aerosol

Secondary organic aerosol (SOA) formed from the oxidation of monoterpenes can impact the Earth’s radiation balance, act as cloud condensation nuclei and negatively affect human health. In the summer of 2015, the Secondary Organic Aerosol From Forest Emission Experiment (SOAFFEE) laboratory campaign was launched in order to study the physical properties of SOA generated from the oxidation of α−pinene and Δ-carene. Both compounds are gas-phase monoterpenes emitted into the atmosphere via biogenic sources. In this study, the peroxide content of SOA was determined using an iodometricspectrophotometric (IS) technique. It was found that the peroxide content of SOA generated during the SOAFFEE campaign was similar to that found in previous studies

Determination of Total Peroxide Content in Secondary Organic Aerosol Particles

Secondary organic aerosol particles (SOA) formed from the oxidation of monoterpenes can impact the Earth’s radiation balance, act as cloud condensation nuclei and negatively affect human health. In the initial Visiting Faculty Program application, we proposed the use of an ultraviolet-visible spectrometer equipped with a liquid waveguide capillary flow cell to determine the extent to which SOA absorb visible light. The inclusion of Concordia University in the Secondary Organic Aerosol From Forest Emissions Experiment (SOAFFEE) laboratory campaign at PNNL necessitated a change in the proposed experiments. An iodometric-spectrophotometric (IS) technique was developed to quantify the total peroxide content in SOA. The experimental technique was validated by measuring the peroxide content in commercially available products. After the validation of the experimental technique, the total peroxide content of SOA formed from a variety of experimental conditions was quantified. It was found that the amount of peroxides in the SOA generated at PNNL was similar to that found in previous research studies. The research carried out at PNNL will be included in an undergraduate senior thesis at Concordia University - Portland (CU). It is also expected that the research will be included in peer-reviewed journal articles. It is our hope that the success of our work will result in future collaborations between PNNL and CU

Droplet activation, separation, and compositional analysis: laboratory studies and atmospheric measurements [Discussion paper]

Droplets produced in a cloud condensation nucleus chamber as a function of supersaturation have been separated from unactivated aerosol particles using counterflow virtual impaction. Residual material after droplets were evaporated was chemically analyzed with an Aerodyne Aerosol Mass Spectrometer and the Particle Analysis by Laser Mass Spectrometry instrument. Experiments were initially conducted to verify activation conditions for monodisperse ammonium sulfate particles and to determine the resulting droplet size distribution as a function of supersaturation. Based on the observed droplet size, the counterflow virtual impactor cut-size was set to differentiate droplets from unactivated interstitial particles. Validation experiments were then performed to verify that only droplets with sufficient size passed through the counterflow virtual impactor for subsequent analysis. A two-component external mixture of monodisperse particles was also exposed to a supersaturation which would activate one of the types (ammonium sulfate) but not the other (polystyrene latex spheres). The mass spectrum observed after separation indicated only the former, validating separation of droplets from unactivated particles. Results from atmospheric measurements using this technique indicate that aerosol particles often activate predominantly as a function of particle size. Chemical composition is not irrelevant, however, and we observed enhancement of sulfate in droplet residuals using single particle analysis

Droplet activation, separation, and compositional analysis: laboratory studies and atmospheric measurements

Droplets produced in a cloud condensation nuclei chamber (CCNC) as a function of supersaturation have been separated from unactivated aerosol particles using counterflow virtual impaction. Residual material after droplets were evaporated was chemically analyzed with an Aerodyne Aerosol Mass Spectrometer (AMS) and the Particle Analysis by Laser Mass Spectrometry (PALMS) instrument. Experiments were initially conducted to verify activation conditions for monodisperse ammonium sulfate particles and to determine the resulting droplet size distribution as a function of supersaturation. Based on the observed droplet size, the counterflow virtual impactor cut-size was set to differentiate droplets from unactivated interstitial particles. Validation experiments were then performed to verify that only droplets with sufficient size passed through the counterflow virtual impactor for subsequent analysis. A two-component external mixture of monodisperse particles was also exposed to a supersaturation which would activate one of the types (hygroscopic salts) but not the other (polystyrene latex spheres or adipic acid). The mass spectrum observed after separation indicated only the former, validating separation of droplets from unactivated particles. Results from ambient measurements using this technique and AMS analysis were inconclusive, showing little chemical differentiation between ambient aerosol and activated droplet residuals, largely due to low signal levels. When employing as single particle mass spectrometer for compositional analysis, however, we observed enhancement of sulfate in droplet residuals

Natural Office Vacancy Rates: Some Additional Estimates

[Excerpt] In our recent paper (Shilling et al. [2]), we examined the rent adjustment process for 17 U.S. office markets and provided the first estimates of the natural vacancy rates. In his comment, Voith [3] argues that our specification of the rent-vacancy relationship is biased since we introduced an interaction term to capture the effect of risks associated with higher vacancy levels. He suggests that an alternative specification would be to enter a vacancy squared term to capture this risk effect

Determination of the Optical Properties of Secondary Organic Aerosol Particles

The enhanced greenhouse effect is currently considered to be our most important global environmental problem. While the magnitude of radiation absorbed by greenhouse gases is known to a high certainty, the absorption of radiation by atmospheric aerosol particles is not. In the initial Visiting Faculty Program application, we proposed the use of an ultraviolet-visible (UV/Vis) spectrometer equipped with a liquid waveguide capillary flow cell to determine the extent to which secondary organic aerosol particles (SOA) absorb visible light. Early in the research period, the UV/Vis technique was optimized for three solvent systems (methanol, water and 0.1 M hydrochloric acid). Using the optimized UV/Vis technique optical properties such as mass specific absorption cross-section and imaginary refractive index were determined for SOA dissolved in different solvent systems. The end result of the UV/Vis studies is the inclusion of SOA optical properties into climate models developed at the Pacific Northwest National Laboratory (PNNL). This knowledge will help to improve climate models, which currently do not include the effect of SOA. We also utilized Fourier Transform Infrared Spectroscopy to help elucidate the chemical composition of SOA. Finally, an experimental method was developed to determine the peroxide content of SOA. It is expected that these studies will connect the chemical composition of SOA to their optical properties. The research carried out at PNNL will be included in two undergraduate senior theses at Concordia University - Portland (CU). It is also expected that this research will be included in a peer-reviewed journal article. It is our hope that success of our work will result in future collaborations between PNNL and CU students

Price Adjustment Process for Rental Office Space

This paper analyzes the price adjustment process for rental office space in 17 cities across the United States over the time period 1960 to 1975. The results confirm much of what economic theory suggests. Landlords react to fluctuations in demand by building up or drawing down inventories of unlet or vacant office space. Other things equal, higher levels of vacant office space mean that landlords lower their rents and reduce the difference between desired and actual vacancies. Empirical evidence is also presented on the normal vacancy rate across different cities

Estimating Net Realizable Value for Distressed Real Estate

This paper provides a framework for adjusting distressed real estate properties for liquidating discounts. We estimate the probability of receiving an offer on a property in any particular short interval of time. Our empirical evidence allows us to predict the average rate at which offers will occur in any particular interval of time. Further, it allows us to arrive at an estimate of net realizable value, adjusted for selling expenses.

Patient and public understanding of the concept of ‘personalised medicine’ in relation to cancer treatment: a systematic review

Personalised medicine (PM) is becoming increasingly integrated into standard clinical practice for treating numerous diseases, including cancer. Implementing PM into healthcare systems will only be successful with the acceptance and input of both patients’ and public opinion. This review, therefore, aimed to identify both patients’ and public understanding, and perceived benefits and concerns of PM in cancer treatment. A literature search was conducted using MEDLINE, EMBASE, PsycINFO and CINAHL databases. The eligibility criteria specified that papers must explore the public or patients’ understanding of PM or pharmacogenomic (PGx) testing in relation to cancer treatment. Patients have a greater understanding of, and trust in, PM compared with members of the public, but often misunderstand how genomic testing in PM works. Key areas that can be targeted to inform future health literacy interventions include genetic literacy for the public and understanding of how PM testing and treatment works for patients

Hygroscopic Growth of Ammonium Sulfate/Dicarboxylic Acids

Recent studies have shown that tropospheric sulfate aerosols commonly contain 50% by mass organic species. The influence of these organics on the chemical and physical properties of sulfate aerosols is not fully established. We have measured the water activity of pure dicarboxylic acids and eutonic mixtures of ammonium sulfate/dicarboxylic acids at 25°C and have calculated van\u27t Hoff factors for each individual system. We have also used the vapor pressure data to determine the hygroscopic growth curves for pure dicarboxylic acids and eutonic mixtures and provide power law fits to the data. For the systems studied we find that the presence of soluble dicarboxylic acids at the eutonic proportion depresses hygroscopic growth when compared to pure ammonium sulfate. In addition, we find that the presence of low-solubility dicarboxylic acids at the eutonic proportion has no effect on the hygroscopic growth when compared to pure ammonium sulfate. To model the hygroscopic growth curves of the eutonic solutions, we employed the Zdanovskii, Stokes, and Robinson method. It was found that this approximation was accurate to within 17% for all the systems studied