Ambient levels of chlorinated gases and aerosol components were measured by online chemical ionization and aerosol mass spectrometers after an indoor floor were repeatedly washed with a commercial bleach solution. Gaseous chlorine (Cl , 10's of ppbv) and hypochlorous acid (HOCl, 100's of ppbv) arise after floor washing, along with nitryl chloride (ClNO ), dichlorine monoxide (Cl O), and chloramines (NHCl , NCl ). Much higher mixing ratios would prevail in a room with lower and more commonly encountered air exchange rates than that observed in the study (12.7 h ). Coincident with the formation of gas-phase species, particulate chlorine levels also rise. Cl , ClNO , NHCl , and NCl exist in the headspace of the bleach solution, whereas HOCl was only observed after floor washing. HOCl decays away 1.4 times faster than the air exchange rate, indicative of uptake onto room surfaces, and consistent with the well-known chlorinating ability of HOCl. Photochemical box modeling captures the temporal profiles of Cl and HOCl very well and indicates that the OH, Cl, and ClO gas-phase radical concentrations in the indoor environment could be greatly enhanced (>10 and 10 cm for OH and Cl, respectively) in such washing conditions, dependent on the amount of indoor illumination.

We report elevated levels of gaseous inorganic chlorinated and nitrogenated compounds in indoor air while cleaning with a commercial bleach solution during the House Observations of Microbial and Environmental Chemistry field campaign in summer 2018. Hypochlorous acid (HOCl), chlorine (Cl2), and nitryl chloride (ClNO2) reached part-per-billion by volume levels indoors during bleach cleaningseveral orders of magnitude higher than typically measured in the outdoor atmosphere. Kinetic modeling revealed that multiphase chemistry plays a central role in controlling indoor chlorine and reactive nitrogen chemistry during these periods. Cl2 production occurred via heterogeneous reactions of HOCl on indoor surfaces. ClNO2 and chloramine (NH2Cl, NHCl2, NCl3) production occurred in the applied bleach via aqueous reactions involving nitrite (NO2 –) and ammonia (NH3), respectively. Aqueous-phase and surface chemistry resulted in elevated levels of gas-phase nitrogen dioxide (NO2). We predict hydroxyl (OH) and chlorine (Cl) radical production during these periods (106 and 107 molecules cm–3 s–1, respectively) driven by HOCl and Cl2 photolysis. Ventilation and photolysis accounted for <50% and <0.1% total loss of bleach-related compounds from indoor air, respectively; we conclude that uptake to indoor surfaces is an important additional loss process. Indoor HOCl and nitrogen trichloride (NCl3) mixing ratios during bleach cleaning reported herein are likely detrimental to human health.

Indoor oxidizing capacity in occupied residences is poorly understood. We made simultaneous continuous time-resolved measurements of ozone (O), nitric oxide (NO), nitrogen dioxide (NO), and nitrous acid (HONO) for two months in an occupied detached home with gas appliances in Syracuse, NY. Indoor NO and HONO mixing ratios were higher than those outdoors, whereas O was much lower (sub-ppbv) indoors. Cooking led to peak NO, NO, and HONO levels 20-100 times greater than background levels; HONO mixing ratios of up to 50 ppbv were measured. Our results suggest that many reported NO levels may have a large positive bias due to HONO interference. Nitrous acid, NO, and NO were removed from indoor air more rapidly than CO, indicative of reactive removal processes or surface uptake. We measured spectral irradiance from sunlight entering the residence through glass doors; hydroxyl radical (OH) production rates of (0.8-10) × 10 molecules cm s were calculated in sunlit areas due to HONO photolysis, in some cases exceeding rates expected from ozone-alkene reactions. Steady-state nitrate radical (NO) mixing ratios indoors were predicted to be lower than 1.65 × 10 molecules cm. This work will help constrain the temporal nature of oxidant concentrations in occupied residences and will improve indoor chemistry models.

Wildfires are important contributors to atmospheric aerosols and a large source of emissions that impact regional air quality and global climate. In this study, the regional and nearfield influences of wildfire emissions on ambient aerosol concentration and chemical properties in the Pacific Northwest region of the United States were studied using real-time measurements from a fixed ground site located in Central Oregon at the Mt. Bachelor Observatory (∼2700 m a.s.l.) as well as near their sources using an aircraft. The regional characteristics of biomass burning aerosols were found to depend strongly on the modified combustion efficiency (MCE), an index of the combustion processes of a fire. Organic aerosol emissions had negative correlations with MCE, whereas the oxidation state of organic aerosol increased with MCE and plume aging. The relationships between the aerosol properties and MCE were consistent between fresh emissions (∼1 h old) and emissions sampled after atmospheric transport (6-45 h), suggesting that biomass burning organic aerosol concentration and chemical properties were strongly influenced by combustion processes at the source and conserved to a significant extent during regional transport. These results suggest that MCE can be a useful metric for describing aerosol properties of wildfire emissions and their impacts on regional air quality and global climate.

An open reading frame (ORF) with homology to interleukin-10 (IL-10) has been identified in rhesus cytomegalovirus (RhCMV). The IL-10-like protein is generated from a multispliced, polyadenylated early gene transcript encompassing part of the corresponding UL111A ORF of human CMV (HCMV). Immunological analyses confirm expression of the IL-10-like protein both in tissue culture and in RhCMV-infected rhesus macaques. Conserved ORFs were subsequently identified in human, baboon, and African green monkey CMV, and a fully processed transcript has been mapped in fibroblasts infected with the Towne strain of HCMV. The conservation of this previously unrecognized ORF suggests that the protein may play an essential role in primate CMV persistence and pathogenesis.

Abstract. Biomass burning (BB) is one of the most important contributors to atmospheric aerosols on a global scale, and wildfires are a large source of emissions that impact regional air quality and global climate. As part of the Biomass Burning Observation Project (BBOP) field campaign in summer 2013, we deployed a high-resolution time-of-flight aerosol mass spectrometer (HR-AMS) coupled with a thermodenuder at the Mt. Bachelor Observatory (MBO, ∼  2.8 km above sea level) to characterize the impact of wildfire emissions on aerosol loading and properties in the Pacific Northwest region of the United States. MBO represents a remote background site in the western US, and it is frequently influenced by transported wildfire plumes during summer. Very clean conditions were observed at this site during periods without BB influence where the 5 min average (±1σ) concentration of non-refractory submicron aerosols (NR-PM1) was 3.7 ± 4.2 µg m−3. Aerosol concentration increased substantially (reaching up to 210 µg m−3 of NR-PM1) for periods impacted by transported BB plumes, and aerosol composition was overwhelmingly organic. Based on positive matrix factorization (PMF) of the HR-AMS data, three types of BB organic aerosol (BBOA) were identified, including a fresh, semivolatile BBOA-1 (O ∕ C  =  0.35; 20 % of OA mass) that correlated well with ammonium nitrate; an intermediately oxidized BBOA-2 (O ∕ C  =  0.60; 17 % of OA mass); and a highly oxidized BBOA-3 (O ∕ C  =  1.06; 31 % of OA mass) that showed very low volatility with only  ∼  40 % mass loss at 200 °C. The remaining 32 % of the OA mass was attributed to a boundary layer (BL) oxygenated OA (BL-OOA; O ∕ C  =  0.69) representing OA influenced by BL dynamics and a low-volatility oxygenated OA (LV-OOA; O ∕ C  =  1.09) representing regional aerosols in the free troposphere. The mass spectrum of BBOA-3 resembled that of LV-OOA and had negligible contributions from the HR-AMS BB tracer ions – C2H4O2+ (m∕z = 60.021) and C3H5O2+ (m∕z = 73.029); nevertheless, it was unambiguously related to wildfire emissions. This finding highlights the possibility that the influence of BB emission could be underestimated in regional air masses where highly oxidized BBOA (e.g., BBOA-3) might be a significant aerosol component but where primary BBOA tracers, such as levoglucosan, are depleted. We also examined OA chemical evolution for persistent BB plume events originating from a single fire source and found that longer solar radiation led to higher mass fraction of the chemically aged BBOA-2 and BBOA-3 and more oxidized aerosol. However, an analysis of the enhancement ratios of OA relative to CO (ΔOA ∕ΔCO) showed little difference between BB plumes transported primarily at night versus during the day, despite evidence of substantial chemical transformation in OA induced by photooxidation. These results indicate negligible net OA production in photochemically aged wildfire plumes observed in this study, for which a possible reason is that SOA formation was almost entirely balanced by BBOA volatilization. Nevertheless, the formation and chemical transformation of BBOA during atmospheric transport can significantly influence downwind sites with important implications for health and climate.

We investigate the effects of sulfate and nitrate on the formation and evolution of secondary organic aerosol formed in the aqueous phase (aqSOA) from photooxidation of two phenolic carbonyls emitted from wood burning. AqSOA was formed efficiently from the photooxidation of both syringaldehyde (CHO) and acetosyringone (CHO) in ammonium sulfate and ammonium nitrate solutions, with mass yields ranging from 30% to 120%. Positive matrix factorization on the organic mass spectra acquired by an Aerosol Mass Spectrometer revealed a combination of functionalization, oligomerization, and fragmentation processes in the chemical evolution of aqSOA. Functionalization and oligomerization dominated in the first 4 h of reaction, with phenolic oligomers and their derivatives significantly contributing to aqSOA formation; and oxidation of the first-generation products led to an abundance of oxygenated ring-opening products. Degradation rates of syringaldehyde and acetosyringone in nitrate solutions were 1.5 and 3.5 times faster than rates in sulfate solutions, and aqSOA yields in nitrate experiments are twice as high as in sulfate experiments. Nitrate likely promoted the reactions because it is a photolytic source of OH radicals, while sulfate is not, highlighting the importance of aerosol-phase nitrate in the formation of aqSOA by facilitating the photooxidation of organic precursors.

Abstract. The San Joaquin Valley (SJV) in California experiences persistent air-quality problems associated with elevated particulate matter (PM) concentrations due to anthropogenic emissions, topography, and meteorological conditions. Thus it is important to unravel the various sources and processes that affect the physicochemical properties of PM in order to better inform pollution abatement strategies and improve parameterizations in air-quality models. During January and February 2013, a ground supersite was installed at the Fresno–Garland California Air Resources Board (CARB) monitoring station, where comprehensive, real-time measurements of PM and trace gases were performed using instruments including an Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) and an Ionicon proton transfer reaction time-of-flight mass spectrometer (PTR-TOF-MS) as part of the NASA Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) campaign. The average submicron aerosol (PM1) concentration was 31.0 µg m−3 and the total mass was dominated by organic aerosols (OA, 55 %), followed by ammonium nitrate (35 %). High PM pollution events were commonly associated with elevated OA concentrations, mostly from primary sources. Organic aerosols had average atomic oxygen-to-carbon (O / C), hydrogen-to-carbon (H / C), and nitrogen-to-carbon (N / C) ratios of 0.42, 1.70, and 0.017, respectively. Six distinct sources of organic aerosol were identified from positive matrix factorization (PMF) analysis of the AMS data: hydrocarbon-like OA (HOA; 9 % of total OA, O / C  =  0.09) associated with local traffic, cooking OA (COA; 18 % of total OA, O / C  =  0.19) associated with food cooking activities, two biomass burning OA (BBOA1: 13 % of total OA, O / C  =  0.33; BBOA2: 20 % of total OA, O / C  =  0.60) most likely associated with residential space heating from wood combustion, and semivolatile oxygenated OA (SV-OOA; 16 % of total OA, O / C  =  0.63) and low-volatility oxygenated OA (LV-OOA; 24 % of total OA, O / C  =  0.90) formed via chemical reactions in the atmosphere. Large differences in aerosol chemistry at Fresno were observed between the current campaign (winter 2013) and a previous campaign in winter 2010, most notably that PM1 concentrations were nearly 3 times higher in 2013 than in 2010. These variations were attributed to differences in the meteorological conditions, which influenced primary emissions and secondary aerosol formation. In particular, COA and BBOA concentrations were greater in 2013 than 2010, where colder temperatures in 2013 likely resulted in increased biomass burning activities. The influence from a nighttime formed residual layer that mixed down in the morning was found to be much more intense in 2013 than 2010, leading to sharp increases in ground-level concentrations of secondary aerosol species including nitrate, sulfate, and OOA, in the morning between 08:00 and 12:00 PST. This is an indication that nighttime chemical reactions may have played a more important role in 2013. As solar radiation was stronger in 2013 the higher nitrate and OOA concentrations in 2013 could also be partly due to greater photochemical production of secondary aerosol species. The greater solar radiation and larger range in temperature in 2013 also likely led to both SV-OOA and LV-OOA being observed in 2013 whereas only a single OOA factor was identified in 2010.