Underestimation of Thermogenic Methane Emissions in New York City.

Recent studies have shown that methane emissions are underestimated by inventories in many US urban areas. This has important implications for climate change mitigation policy at the city, state, and national levels. Uncertainty in both the spatial distribution and sectoral allocation of urban emissions can limit the ability of policy makers to develop appropriately focused emission reduction strategies. Top-down emission estimates based on atmospheric greenhouse gas measurements can help to improve inventories and inform policy decisions. This study presents a new high-resolution (0.02 × 0.02°) methane emission inventory for New York City and its surrounding area, constructed using the latest activity data, emission factors, and spatial proxies. The new high-resolution inventory estimates of methane emissions for the New York-Newark urban area are 1.3 times larger than those for the gridded Environmental Protection Agency inventory. We used aircraft mole fraction measurements from nine research flights to optimize the high-resolution inventory emissions within a Bayesian inversion. These sectorally optimized emissions show that the high-resolution inventory still significantly underestimates methane emissions within the New York-Newark urban area, primarily because it underestimates emissions from thermogenic sources (by a factor of 2.3). This suggests that there remains a gap in our process-based understanding of urban methane emissions.

A comprehensive strategy for the identification of biologics by liquid-chromatography-mass spectrometry for release testing in a regulated environment.

Identification (ID) testing is a regulatory requirement for biopharmaceutical manufacturing, requiring robust, GMP-qualified assays that can distinguish the therapeutic from any other in the facility. Liquid Chromatography-Mass Spectrometry (LC-MS) is a powerful analytical tool used to identify and characterize biologics. While routinely leveraged for characterization, LC-MS is relatively rare in Quality Control (QC) settings due to its perceived complexity and scarcity of MS-trained personnel. However, employing LC-MS for identification of drug products has many advantages versus conventional ID techniques, including but not limited to its high specificity, rapid turn-around time, and ease of method execution. In this work, we outline the development and implementation of a comprehensive LC-MS based ID strategy for biologics release testing. Two main workflows (WFs) were developed: i) WF1, a subunit-based assay measuring the molecular weight of the light chain (LC) and heavy chain (HC) of an antibody upon reduction, and ii) WF2, intact mass measurement of the biologic upon N-deglycosylation by PNGase F. The proposed strategy is shown to be applicable for over 40 diverse model biologics including monoclonal antibodies (mAbs), biobetters such as antibody prodrugs/afucosylated mAbs, fusion proteins, multi-specific antibodies, Fabs, and large peptides, all with excellent mass accuracy (error typically < 20 ppm) and precision. It requires a single-step sample preparation and a single click to run and process the data upon method setup. This strategy has been successfully implemented for release testing in GMP labs. Challenges and considerations for the establishment of QC-friendly methods are discussed. It is also shown that these methods can be applied to the ID of more analytically complex biotherapeutics, such as fixed-dose combination (FDC) and drug products co-formulated with trace-level additives.

Aerosol Mass Spectral Profiles from NAMaSTE Field-Sampled South Asian Combustion Sources.

Unit mass resolution mass spectral profiles of nonrefractory submicron aerosol were retrieved from undersampled atmospheric emission sources common to South Asia using a "mini" aerosol mass spectrometer. Emission sources including wood- and dung-fueled cookstoves, agricultural residue burning, garbage burning, engine exhaust, and coal-fired brick kilns were sampled during the 2015 Nepal Ambient Monitoring and Source Testing Experiment (NAMaSTE) campaign. High-resolution peak fitting estimates of the mass spectra were used to characterize ions found within each source profile and help identify mass spectral signatures unique to aerosol emissions from the investigated source types. The first aerosol mass spectral profiles of dung burning, charcoal burning, garbage burning, and brick kilns are provided in this work. The online aerosol mass spectra show that organics were generally the dominant component of the nonrefractory aerosol. However, inorganic aerosol components including ammonium and chloride were significant in dung- and charcoal-fired cookstove emissions and sulfate compounds were major components of the coal-fired brick kiln emissions. Organic mass spectra from both the charcoal burning and zigzag brick kiln were dominated by nitrogen-containing ions thought to be from the electron ionization of amines and amides contained in the emissions. The mixed garbage burning emissions profiles were dominated by plastic combustion with very low fractions of organic markers associated with biomass burning. The plastic burning emissions were associated with enhanced organic signal at mass-to-charge (m/z) 104 and m/z 166, which could be useful fragment ion indicators for garbage burning in ambient aerosol profiles. Finally, a framework for the identification of emission sources using the unit mass resolution organic mass fractions at m/z 55 (f 55), m/z 57 (f 57), and m/z 60 (f 60) is proposed in this work. Plotting the ratio of f 55 to f 57 versus f 60 is found to be effective for the identification of emissions by the fuel type and even useful in separating emissions of similar source types. Although the sample size was limited, these results give further context to the aerosol and gas-phase emission factors presented in other NAMaSTE works and provide a critical reference for future aerosol composition measurements in South Asia.

Garbage Burning in South Asia: How Important Is It to Regional Air Quality?

Increasing air pollution in South Asia has serious consequences for air quality and human/ecosystem health within the region. South Asia, including India and Nepal, suffers from severe air pollution, including high concentrations of aerosols, as well as gaseous pollutants. One of the often-neglected sources contributing to the regional air pollution is garbage burning. It is mostly related to numerous yet small, open, uncontrolled fires burning diverse fuels, making it difficult to quantify activity and emissions. In this study, we attempted to quantify the total emissions due to garbage burning and its contribution to regional air quality, using new observational data, a new inventory, and a regional chemical transport model. We implemented the newly available emission factors (EFs) from a recent field campaign, Nepal Ambient Monitoring and Source Testing Experiment (NAMaSTE), which took place in April 2015. Using a chemical transport model-Weather Research and Forecasting model coupled with Chemistry version 3.5 (WRF-Chem)-and three emission scenarios, we assessed the impact of open garbage burning emissions on regional air quality. Our results show that garbage burning emissions could increase PM2.5 concentrations by nearly 30% in India and Nepal, and result in ∼300 000 premature deaths from chronic obstructive pulmonary disease in the two countries.

Surface organization of a DPPC monolayer on concentrated SrCl2 and ZnCl2 solutions.

Transition metals are known to be enriched in organic-coated marine aerosols, but the impact these cations have on their surface properties is not well understood. Here the effect of Zn2+ enrichment on the surface properties of a dipalmitoylphosphatidylcholine (DPPC) monolayer was investigated and compared to that of the alkaline earth metal Sr2+, an ion not enriched in aerosols. Phase behavior of the DPPC film on concentrated aqueous solutions was probed with surface pressure-area isotherms while domain morphology was monitored with Brewster angle microscopy (BAM). Infrared reflection-absorption spectroscopy (IRRAS) and vibrational sum frequency generation (VSFG) spectroscopy were used to assess the impact of cations on the conformation and orientation of alkyl chains as well as the hydration state of the carbonyl and phosphatidylcholine (PC) moieties. Results of compression isotherms and BAM show that Zn2+ strongly interacts with DPPC molecules, and induces condensation of the monolayer while Sr2+ only weakly interacts with the monolayer in expanded phases. Conformational order and orientation of alkyl chains in the condensed phase are not significantly altered by either cation. IRRAS indicates that Sr2+ has weak interactions with the PC headgroup. Zn2+ ions cause dehydration of carbonyl groups and binds to the phosphate group in a 2 : 1 bridging complex. Findings here suggest that Sr2+ is not enriched in aerosols because it behaves similar to a monovalent ion and only weakly interacts with the monolayer, while enrichment of Zn2+ is due to strong binding to the lipid film.

Enrichment of Saccharides and Divalent Cations in Sea Spray Aerosol During Two Phytoplankton Blooms.

Sea spray aerosol (SSA) is a globally important source of particulate matter. A mesocosm study was performed to determine the relative enrichment of saccharides and inorganic ions in nascent fine (PM2.5) and coarse (PM10-2.5) SSA and the sea surface microlayer (SSML) relative to bulk seawater. Saccharides comprise a significant fraction of organic matter in fine and coarse SSA (11 and 27%, respectively). Relative to sodium, individual saccharides were enriched 14-1314-fold in fine SSA, 3-138-fold in coarse SSA, but only up to 1.0-16.2-fold in SSML. Enrichments in SSML were attributed to rising bubbles that scavenge surface-active species from seawater, while further enrichment in fine SSA likely derives from bubble films. Mean enrichment factors for major ions demonstrated significant enrichment in fine SSA for potassium (1.3), magnesium (1.4), and calcium (1.7), likely because of their interactions with organic matter. Consequently, fine SSA develops a salt profile significantly different from that of seawater. Maximal enrichments of saccharides and ions coincided with the second of two phytoplankton blooms, signifying the influence of ocean biology on selective mass transfer across the ocean-air interface.

Urban Enhancement of PM10 Bioaerosol Tracers Relative to Background Locations in the Midwestern United States.

Bioaerosols are well-known immune-active particles that exacerbate respiratory diseases. Human exposures to bioaerosols and their resultant health impacts depend on their ambient concentrations, seasonal and spatial variation, and co-pollutants, which are not yet widely characterized. In this study, chemical and biological tracers of bioaerosols were quantified in respirable particulate matter (PM10) collected at three urban and three background sites in the Midwestern United States across four seasons in 2012. Endotoxins from gram negative bacteria (and a few gram positive bacteria), water-soluble proteins, and tracers for fungal spores (fungal glucans, arabitol and mannitol) were ubiquitous and showed significant seasonal variation and dependence on temperature. Fungal spores were elevated in spring and peaked in summer, following the seasonal growing cycle, while endotoxins peaked in autumn during the row crop harvesting season. Paired comparisons of bioaerosols in urban and background sites revealed significant urban enhancements in PM10, fungal glucans, endotoxins and water-soluble proteins relative to background locations, such that urban populations have a greater outdoor exposure to bioaerosols. These bioaerosols contribute, in part, to the urban excesses in PM10. Higher bioaerosol mass fractions in urban areas relative to background sites indicate that urban areas serve as a source of bioaerosols. Similar urban enhancements in water-soluble calcium and its correlation with bioaerosol tracers point towards wind-blown soil as an important source of bioaerosols in urban areas.

Selectivity Across the Interface: A Test of Surface Activity in the Composition of Organic-Enriched Aerosols from Bubble Bursting.

Although theories have been developed that describe surface activity of organic molecules at the air-water interface, few studies have tested how surface activity impacts the selective transfer of molecules from solution phase into the aerosol phase during bubble bursting. The selective transfer of a series of organic compounds that differ in their solubility and surface activity from solution into the aerosol phase is quantified experimentally for the first time. Aerosol was produced from solutions containing salts and a series of linear carboxlyates (LCs) and dicarboxylates (LDCs) using a bubble bursting process. Surface activity of these molecules dominated the transport across the interface, with enrichment factors of the more surface-active C4-C8 LCs (55 ± 8) being greater than those of C4-C8 LDCs (5 ± 1). Trends in the estimated surface concentrations of LCs at the liquid-air interface agreed well with their relative concentrations in the aerosol phase. In addition, enrichment of LCs was followed by enrichment of calcium with respect to other inorganic cations and depletion of chloride and sulfate.

Analysis of Organic Anionic Surfactants in Fine and Coarse Fractions of Freshly Emitted Sea Spray Aerosol.

The inclusion of organic compounds in freshly emitted sea spray aerosol (SSA) has been shown to be size-dependent, with an increasing organic fraction in smaller particles. Here we have used electrospray ionization-high resolution mass spectrometry in negative ion mode to identify organic compounds in nascent sea spray collected throughout a 25 day mesocosm experiment. Over 280 organic compounds from ten major homologous series were tentatively identified, including saturated (C8-C24) and unsaturated (C12-C22) fatty acids, fatty acid derivatives (including saturated oxo-fatty acids (C5-C18) and saturated hydroxy-fatty acids (C5-C18), organosulfates (C2-C7, C12-C17) and sulfonates (C16-C22). During the mesocosm, the distributions of molecules within some homologous series responded to variations among the levels of phytoplankton and bacteria in the seawater. The average molecular weight and carbon preference index of saturated fatty acids significantly decreased within fine SSA during the progression of the mesocosm, which was not observed in coarse SSA, sea-surface microlayer or in fresh seawater. This study helps to define the molecular composition of nascent SSA and biological processes in the ocean relate to SSA composition.

Uncontrolled combustion of shredded tires in a landfill - Part 1: Characterization of gaseous and particulate emissions.

In summer 2012, a landfill liner comprising an estimated 1.3 million shredded tires burned in Iowa City, Iowa. During the fire, continuous monitoring and laboratory measurements were used to characterize the gaseous and particulate emissions and to provide new insights into the qualitative nature of the smoke and the quantity of pollutants emitted. Significant enrichments in ambient concentrations of CO, CO2, SO2, particle number (PN), fine particulate (PM2.5) mass, elemental carbon (EC), and polycyclic aromatic hydrocarbons (PAH) were observed. For the first time, PM2.5 from tire combustion was shown to contain PAH with nitrogen heteroatoms (a.k.a. azaarenes) and picene, a compound previously suggested to be unique to coal-burning. Despite prior laboratory studies' findings, metals used in manufacturing tires (i.e. Zn, Pb, Fe) were not detected in coarse particulate matter (PM10) at a distance of 4.2 km downwind. Ambient measurements were used to derive the first in situ fuel-based emission factors (EF) for the uncontrolled open burning of tires, revealing substantial emissions of SO2 (7.1 g kg-1), particle number (3.5×1016 kg-1), PM2.5 (5.3 g kg-1), EC (2.37 g kg-1), and 19 individual PAH (totaling 56 mg kg-1). A large degree of variability was observed in day-to-day EF, reflecting a range of flaming and smoldering conditions of the large-scale fire, for which the modified combustion efficiency ranged from 0.85-0.98. Recommendations for future research on this under-characterized source are also provided.

Emissions of fine particle fluoride from biomass burning.

The burning of biomasses releases fluorine to the atmosphere, representing a major and previously uncharacterized flux of this atmospheric pollutant. Emissions of fine particle (PM2.5) water-soluble fluoride (F-) from biomass burning were evaluated during the fourth Fire Laboratory at Missoula Experiment (FLAME-IV) using scanning electron microscopy energy dispersive X-ray spectroscopy (SEM-EDX) and ion chromatography with conductivity detection. F- was detected in 100% of the PM2.5 emissions from conifers (n=11), 94% of emissions from agricultural residues (n=16), and 36% of the grasses and other perennial plants (n=14). When F- was quantified, it accounted for an average (±standard error) of 0.13±0.02% of PM2.5. F- was not detected in remaining samples (n=15) collected from peat burning, shredded tire combustion, and cook-stove emissions. Emission factors (EF) of F- emitted per kilogram of biomass burned correlated with emissions of PM2.5 and combustion efficiency, and also varied with the type of biomass burned and the geographic location where it was harvested. Based on recent evaluations of global biomass burning, we estimate that biomass burning releases 76 Gg F- yr(-1) to the atmosphere, with upper and lower bounds of 40-150 Gg F- yr(-1). The estimated F- flux from biomass burning is comparable to total fluorine emissions from coal combustion plus other anthropogenic sources. These data demonstrate that biomass burning represents a major source of fluorine to the atmosphere in the form of fine particles, which have potential to undergo long-range transport.