Simultaneous Measurements of Atmospheric HONO and NO2 via Absorption Spectroscopy using Tunable Mid-Infrared Continuous-wave Quantum Cascade Lasers

Nitrous acid (HONO) is important as a significant source of hydroxyl radical (OH) in the troposphere and as a potent indoor air pollutant. It is thought to be generated in both environments via heterogeneous reactions involving nitrogen dioxide $(NO_2)$. In order to enable fast-response HONO detection suitable for eddy-covariance flux measurements and to provide a direct method that avoids interferences associated with derivatization, we have developed a 2-channel tunable infrared laser differential absorption spectrometer (TILDAS) capable of simultaneous high-frequency measurements of HONO and NO2. Beams from two mid-infrared continuous-wave mode quantum cascade lasers (cw-QCLs) traverse separate 210 m paths through a multi-pass astigmatic sampling cell at reduced pressure for the direct detection of HONO $(1660 cm^{−1})$ and $(NO_2)$ $(1604 cm^{−1})$. The resulting one-second detection limits (S/N=3) are 300 and 30 ppt (pmol/mol) for HONO and $(NO_2)$, respectively. Our HONO quantification is based on revised line-strengths and peak positions for cis-HONO in the 6-micron spectral region that were derived from laboratory measurements. An essential component of ambient HONO measurements is the inlet system and we demonstrate that heated surfaces and reduced pressure minimize sampling artifacts.Earth and Planetary SciencesEngineering and Applied Science

Characterization of Fine Particulate Matter (PM) and Secondary PM Precursor Gases in Mexico City

This project was one of three collaborating grants designed to understand the atmospheric chemistry and aerosol particle microphysics impacting air quality in the Mexico City Metropolitan Area (MCMA) and its urban plume. The overall effort, titled MCMA- 2006, focused on: 1) the primary emissions of fine particles and precursor gases leading to photochemical production of atmospheric oxidants and secondary aerosol particles and 2) the measurement and analysis of secondary oxidants and secondary fine particular matter (PM) production, with particular emphasis on secondary organic aerosol (SOA). MCAM-2006 pursued it goals through three main activities: 1) performance and publication of detailed analyses of extensive MCMA trace gas and fine PM measurements made by the collaborating groups and others during earlier MCMA field campaigns in 2002 and 2003; 2) deployment and utilization of extensive real-time trace gas and fine PM instrumentation at urban and downwind MCMA sites in support of the MAX-Mex/MILAGRO field measurements in March, 2006; and, 3) analyses of the 2006 MCMA data sets leading to further publications that are based on new data as well as insights from analysis and publication of the 2002/2003 field data. Thirteen archival publications were coauthored with other MCMA-2003 participants. Documented findings included a significantly improved speciated emissions inventory from on-road vehicles, a greatly enhanced understanding of the sources and atmospheric loadings of volatile organic compounds, a unique analysis of the high fraction of ambient formaldehyde from primary emission sources, a much more extensive knowledge of the composition, size distributions and atmospheric mass loadings of both primary and secondary fine PM, including the fact that the rate of MCMA SOA production greatly exceeded that predicted by current atmospheric models, and evaluations of significant errors that can arise from standard air quality monitors for ozone and nitrogen dioxide. Deployment of the Aerodyne mobile laboratory, equipped with instruments from five collaborating laboratories, at the T0 urban supersite, four downwind sites and the Tula industrial area yielded unique trace gas and fine PM data sets during the March 2006 MAXMex/MILAGRO campaign. In addition, on-road measurements as the mobile laboratory moved between sites provided extensive data on 2006 MCMA fleet averaged vehicle emissions. Analyses of 2006 data sets have yielded the identification of a close correlation between the rate of production of SOA and “Odd Oxygen” (O3 + NO2) and primary organic PM with CO in the MCMA urban plume, a more sophisticated understanding of the interplay between nitrogen oxide speciation and ozone production, the identification of significant vehicular emission sources of HCN and CH3CN (usually associated with biomass burning), characterization of the aging of primary carbonaceous PM, and updated 2006 MCMA fleet on-road trace gas and fine PM emissions. Results from analyses of 2002/2003 and 2006 emissions and ambient measurements have conveyed to Mexican air quality managers who are using these data to devise and assess air quality management strategies. All data sets and published analyses are available to DOE/ASP researchers evaluating the impact of urban emissions on regional climate

31st Annual Meeting and Associated Programs of the Society for Immunotherapy of Cancer (SITC 2016) : part two

Background The immunological escape of tumors represents one of the main ob- stacles to the treatment of malignancies. The blockade of PD-1 or CTLA-4 receptors represented a milestone in the history of immunotherapy. However, immune checkpoint inhibitors seem to be effective in specific cohorts of patients. It has been proposed that their efficacy relies on the presence of an immunological response. Thus, we hypothesized that disruption of the PD-L1/PD-1 axis would synergize with our oncolytic vaccine platform PeptiCRAd. Methods We used murine B16OVA in vivo tumor models and flow cytometry analysis to investigate the immunological background. Results First, we found that high-burden B16OVA tumors were refractory to combination immunotherapy. However, with a more aggressive schedule, tumors with a lower burden were more susceptible to the combination of PeptiCRAd and PD-L1 blockade. The therapy signifi- cantly increased the median survival of mice (Fig. 7). Interestingly, the reduced growth of contralaterally injected B16F10 cells sug- gested the presence of a long lasting immunological memory also against non-targeted antigens. Concerning the functional state of tumor infiltrating lymphocytes (TILs), we found that all the immune therapies would enhance the percentage of activated (PD-1pos TIM- 3neg) T lymphocytes and reduce the amount of exhausted (PD-1pos TIM-3pos) cells compared to placebo. As expected, we found that PeptiCRAd monotherapy could increase the number of antigen spe- cific CD8+ T cells compared to other treatments. However, only the combination with PD-L1 blockade could significantly increase the ra- tio between activated and exhausted pentamer positive cells (p= 0.0058), suggesting that by disrupting the PD-1/PD-L1 axis we could decrease the amount of dysfunctional antigen specific T cells. We ob- served that the anatomical location deeply influenced the state of CD4+ and CD8+ T lymphocytes. In fact, TIM-3 expression was in- creased by 2 fold on TILs compared to splenic and lymphoid T cells. In the CD8+ compartment, the expression of PD-1 on the surface seemed to be restricted to the tumor micro-environment, while CD4 + T cells had a high expression of PD-1 also in lymphoid organs. Interestingly, we found that the levels of PD-1 were significantly higher on CD8+ T cells than on CD4+ T cells into the tumor micro- environment (p < 0.0001). Conclusions In conclusion, we demonstrated that the efficacy of immune check- point inhibitors might be strongly enhanced by their combination with cancer vaccines. PeptiCRAd was able to increase the number of antigen-specific T cells and PD-L1 blockade prevented their exhaus- tion, resulting in long-lasting immunological memory and increased median survival

Ethane-Based Chemical Amplification Measurement Technique for Atmospheric Peroxy Radicals

Peroxy radicals play important roles in the atmospheric oxidation of organic compounds and the formation of ozone and secondary organic aerosol. There are few peroxy radical measurement techniques; the most common, chemical amplification using CO and NO, requires the use of toxic reagents, and its calibration factor is very sensitive to relative humidity. We present a new method for quantifying atmospheric peroxy radicals, ECHAMP (Ethane CHemical AMPlifier). Sampled air is mixed with NO and C₂H₆ (rather than CO), effecting a series of reactions that ultimately produces 25 molecules of NO₂ per sampled peroxy radical under dry conditions. This “amplification” factor decreases to 17 at a relative humidity of 50%, yielding a 1σ precision for 90 s average measurements of 0.8–2.5 ppt depending on the atmospheric variability of ozone. We demonstrated the utility of the new technique with measurements in Bloomington, IN, in July 2015

Short-term variation in near-highway air pollutant gradients on a winter morning

Quantification of exposure to traffic-related air pollutants near highways is hampered by incomplete knowledge of the scales of temporal variation of pollutant gradients. The goal of this study was to characterize short-term temporal variation of vehicular pollutant gradients within 200–400 m of a major highway (\u3e150 000 vehicles/d). Monitoring was done near Interstate 93 in Somerville (Massachusetts) from 06:00 to 11:00 on 16 January 2008 using a mobile monitoring platform equipped with instruments that measured ultrafine and fine particles (6–1000 nm, particle number concentration (PNC)); particle-phase (\u3e30 nm) equation M1, equation M2, and organic compounds; volatile organic compounds (VOCs); and CO2, NO, NO2, and O3. We observed rapid changes in pollutant gradients due to variations in highway traffic flow rate, wind speed, and surface boundary layer height. Before sunrise and peak traffic flow rates, downwind concentrations of particles, CO2, NO, and NO2 were highest within 100–250 m of the highway. After sunrise pollutant levels declined sharply (e.g., PNC and NO were more than halved) and the gradients became less pronounced as wind speed increased and the surface boundary layer rose allowing mixing with cleaner air aloft. The levels of aromatic VOCs and equation M3, equation M4 and organic aerosols were generally low throughout the morning, and their spatial and temporal variations were less pronounced compared to PNC and NO. O3 levels increased throughout the morning due to mixing with O3-enriched air aloft and were generally lowest near the highway reflecting reaction with NO. There was little if any evolution in the size distribution of 6–225 nm particles with distance from the highway. These results suggest that to improve the accuracy of exposure estimates to near-highway pollutants, short-term (e.g., hourly) temporal variations in pollutant gradients must be measured to reflect changes in traffic patterns and local meteorology