ACS ES&T Air最新文献

Terpenes are important constituents of volatile organic compounds (VOCs) emitted from both natural and anthropogenic sources, reacting rapidly in the atmosphere to form secondary organic aerosol (SOA), with climate and health implications. In this study, we explore the gas- and particle-phase mass spectra of highly oxygenated organic molecules (HOMs) from the ozonolysis of four monoterpenes (α-pinene, 3-carene, β-pinene, and limonene), a sesquiterpene, and a boreal forest-mimicking terpene mixture in chamber experiments. Measurements were performed by using the new vaporization inlet for aerosols (VIA) coupled to a nitrate-based chemical ionization mass spectrometer (NO₃-CIMS). We found that higher gas-phase HOM yields correlated with increased SOA formation, while detected particle-phase HOM mass fractions also depended on the terpene being oxidized. Elevated particle-phase dimer-to-monomer ratios compared to the gas phase were observed for α-pinene and β-pinene (by a factor of 4–8), which can not be solely explained by the volatility-dependent condensation, suggesting the existence of particle-phase processes. Additionally, a linear reconstruction of the terpene mixture mass spectra from the individual terpene spectra agreed much better for the particle phase than the gas phase, indicating particle-phase reactions forming common HOM species originating from different monoterpenes. Finally, the first ambient VIA–NO₃-CIMS measurements were conducted and showed similar trends for organics compared with aerosol mass spectrometer (AMS) measurements, while the sulfate tracked almost perfectly between the two instruments. However, the organic mass concentrations obtained by the VIA–NO₃-CIMS were lower than from the AMS, with our best estimates suggesting that particle-phase HOMs comprised about 17% of the organics in the ambient air, while in our chamber studies it was 14–29%.

Terpenes form SOA effectively, with climate and health impacts. This study investigates gas- and particle-phase HOMs in both laboratory and ambient experiments, revealing particle-phase processes of HOMs.

Scented volatile chemical products (sVCPs) are frequently used indoors. We conducted field measurements in a residential building to investigate new particle formation (NPF) from sVCP emissions. State-of-the-art instrumentation was used for real-time monitoring of indoor atmospheric nanocluster aerosol (NCA; 1–3 nm particles) size distributions and terpene mixing ratios. We integrated our NCA measurements with a comprehensive material balance model to analyze sVCP-nucleated indoor NCA dynamics. Our results reveal that sVCPs significantly increase indoor terpene mixing ratios (10–1,000 ppb), exceeding those in outdoor forested environments. The emitted terpenes react with indoor atmospheric O₃ and initiate indoor NPF, resulting in nucleation rates as high as ∼10⁵ cm^–3 s^–1 and condensational growth rates up to 300 nm h^–1; these are orders of magnitude higher than those reported during outdoor NPF events. Notably, high particle nucleation rates significantly increase indoor atmospheric NCA concentrations (10⁵–10⁸ cm^–3), and high growth rates drive their survival and growth to sizes that efficiently reach the deepest regions of the human respiratory system. We found sVCP-nucleated NCA to cause respiratory exposures and dose rates comparable to or exceeding those from primary aerosol sources such as gas stoves and diesel engines, highlighting their significant impact on indoor atmospheric environments.

This study investigates how everyday use of scented consumer products significantly elevates indoor atmospheric nanoparticle levels, underscoring the need to monitor them to protect the health and safety of building occupants.

Scented volatile chemical products (sVCPs) are frequently used indoors. We conducted field measurements in a residential building to investigate new particle formation (NPF) from sVCP emissions. State-of-the-art instrumentation was used for real-time monitoring of indoor atmospheric nanocluster aerosol (NCA; 1-3 nm particles) size distributions and terpene mixing ratios. We integrated our NCA measurements with a comprehensive material balance model to analyze sVCP-nucleated indoor NCA dynamics. Our results reveal that sVCPs significantly increase indoor terpene mixing ratios (10-1,000 ppb), exceeding those in outdoor forested environments. The emitted terpenes react with indoor atmospheric O₃ and initiate indoor NPF, resulting in nucleation rates as high as ∼10⁵ cm^-3 s^-1 and condensational growth rates up to 300 nm h^-1; these are orders of magnitude higher than those reported during outdoor NPF events. Notably, high particle nucleation rates significantly increase indoor atmospheric NCA concentrations (10⁵-10⁸ cm^-3), and high growth rates drive their survival and growth to sizes that efficiently reach the deepest regions of the human respiratory system. We found sVCP-nucleated NCA to cause respiratory exposures and dose rates comparable to or exceeding those from primary aerosol sources such as gas stoves and diesel engines, highlighting their significant impact on indoor atmospheric environments.

The adverse health effects of air pollutants are closely associated with their components, including bioaerosols. However, the characteristics of bioaerosols during pollution processes are not yet fully understood. Here, we investigated the 2- to 6-hly dynamics of bacterial aerosols over a short period that spanned one instance of haze and one sandstorm. 16S rRNA gene (rDNA) sequencing was used to identify the total bacteria, and 16S rRNA (rRNA) sequencing was applied to characterize the actively metabolizing bacteria. The results revealed the highest bacterial diversity in sandstorm air and the lowest bacterial diversity in haze air, with markedly different community structures. Moreover, substantial dissimilarity was detected between the communities of total bacteria and active bacteria within the sandstorm air, with less abundant bacteria dominating the active bacterial population. Selective pressure played a pivotal role in shaping the composition of active bacteria during sandstorms and the total bacterial community in hazy air, thereby enabling potential interactions between airborne microorganisms and chemical components. Additionally, functional prediction analysis suggested increased pathogenicity in the active bacteria of sandstorm air. These insights into the aggregated hourly dynamics and activity of bacterial aerosols during pollution processes underscore the importance of further research into the complex interactions between bioaerosols and air pollutants.

Air sensors can provide valuable nonregulatory and supplemental data as they can be affordably deployed in large numbers and stationed in remote areas far away from regulatory air monitoring stations. Air sensors have inherent limitations that are critical to understand before collecting and interpreting the data. Many of these limitations are mechanistic in nature, which will require technological advances. However, there are documented quality assurance (QA) methods to promote data quality. These include laboratory and field evaluation to quantitatively assess performance, the application of corrections to improve precision and accuracy, and active management of the condition or state of health of deployed air quality sensors. This paper summarizes perspectives presented at the U.S. Environmental Protection Agency’s 2023 Air Sensors Quality Assurance Workshop (https://www.epa.gov/air-sensor-toolbox/quality-assurance-air-sensors#QAworkshop) by stakeholders (e.g., manufacturers, researchers, air agencies) and identifies the most pressing needs. These include QA protocols, streamlined data processing, improved total volatile organic compound (TVOC) data interpretation, development of speciated VOC sensors, and increased documentation of hardware and data handling. Community members using air sensors need training and resources, timely data, accessible QA approaches, and shared responsibility with other stakeholders. In addition to identifying the vital next steps, this work provides a set of common QA and QC actions aimed at improving and homogenizing air sensor QA that will allow stakeholders with varying fields and levels of expertise to effectively leverage air sensor data to protect human health.

Air sensors can provide valuable non-regulatory and supplemental data as they can be affordably deployed in large numbers and stationed in remote areas far away from regulatory air monitoring stations. Air sensors have inherent limitations that are critical to understand before collecting and interpreting the data. Many of these limitations are mechanistic in nature, which will require technological advances. However, there are documented quality assurance (QA) methods to promote data quality. These include laboratory and field evaluation to quantitatively assess performance, the application of corrections to improve precision and accuracy, and active management of the condition or state of health of deployed air quality sensors. This paper summarizes perspectives presented at the U.S. Environmental Protection Agency's 2023 Air Sensors Quality Assurance Workshop (https://www.epa.gov/air-sensor-toolbox/quality-assurance-air-sensors#QAworkshop) by stakeholders (e.g., manufacturers, researchers, air agencies) and identifies the most pressing needs. These include QA protocols, streamlined data processing, improved total volatile organic compound (TVOC) data interpretation, development of speciated VOC sensors, and increased documentation of hardware and data handling. Community members using air sensors need training and resources, timely data, accessible QA approaches, and shared responsibility with other stakeholders. In addition to identifying the vital next steps, this work provides a set of common QA and QC actions aimed at improving and homogenizing air sensor QA that will allow stakeholders with varying fields and levels of expertise to effectively leverage air sensor data to protect human health.

During use of sodium hypochlorite bleach, gas-phase hypochlorous acid (HOCl) and chlorine (Cl₂) are released, which can react with organic compounds present in indoor air. Reactivity between HOCl/Cl₂ and limonene, a common constituent of indoor air, has been observed. The purpose of this study was to characterize the chemical species generated from gas-phase reactions between HOCl/Cl₂ and limonene. Gas-phase reactions were prepared in Teflon chambers housing HOCl, Cl₂, and limonene. The resulting chemical products were analyzed using gas-phase preconcentration, followed by gas chromatography and high-resolution mass spectrometry. Several chlorinated products were detected, including limonene species containing one, two, and three chlorines and limonene chlorohydrin. Product concentrations and yields were estimated for the most abundant products, and greater than 80% of transformed limonene was represented in the detected products. Temporal sampling of the reactions allowed time courses to be plotted for limonene decay and chlorinated limonene product generation under different conditions, including the treatments of HOCl/Cl₂, Cl₂ only, high vs low relative humidity, and ± ozone. These experiments add product speciation, yield estimates, and an understanding of environmental factors affecting product formation to previous studies, further highlighting the chemical transformations initiated by sodium hypochlorite bleach in indoor air.

The U.S. EPA's Community Multiscale Air Quality (CMAQ)-adjoint model is used to map monetized health benefits (defined here as benefits of reduced mortality from chronic PM_2.5 exposure) in the form of benefits per ton (of emissions reduced) for the U.S. and Canada for NOx, SO₂, ammonia, and primary PM_2.5 emissions. The adjoint model provides benefits per ton (BPTs) that are location-specific and applicable to various sectors. BPTs show significant variability across locations, such that only 20% of primary PM_2.5 emissions in each country makes up more than half of its burden. The greatest benefits in terms of BPTs are for primary PM_2.5 reductions, followed by ammonia. Seasonal differences in benefits vary by pollutant: while PM_2.5 benefits remain high across seasons, BPTs for reducing ammonia are much higher in the winter due to the increased ammonium nitrate formation efficiency. Based on our location-specific BPTs, we estimate a total of 91,000 U.S. premature mortalities attributable to natural and anthropogenic emissions.

In 2018, the ATHLETIC campaign was conducted at the University of Colorado Dal Ward Athletic Center and characterized dynamic indoor air composition in a gym environment. Among other parameters, inorganic particle and gas-phase species were alternatingly measured in the gym's supply duct and weight room. The Indoor Model of Aerosols, Gases, Emissions, and Surfaces (IMAGES) uses the inorganic aerosol thermodynamic equilibrium model, ISORROPIA, to estimate the partitioning of inorganic aerosols and corresponding gases. In this study herein, measurements from the ATHLETIC campaign were used to evaluate IMAGES' performance. Ammonia emission rates, nitric acid deposition, and particle deposition velocities were related to observed occupancy, which informed these rates in IMAGES runs. Initially, modeled indoor inorganic aerosol concentrations were not in good agreement with measurements. A parametric investigation revealed that lowering the temperature or raising the relative humidity used in the ISORROPIA model drove the semivolatile species more toward the particle phase, substantially improving modeled-measured agreement. One speculated reason for these solutions is that aerosol water was enhanced by increasing the RH or decreasing the temperature. Another is that thermodynamic equilibrium was not established in this indoor setting or that the thermodynamic parametrizations in ISORROPIA are less accurate for typical indoor settings. This result suggests that applying ISORROPIA indoors requires further careful experimental validation.

In 2018, the ATHLETIC campaign was conducted at the University of Colorado Dal Ward Athletic Center and characterized dynamic indoor air composition in a gym environment. Among other parameters, inorganic particle and gas-phase species were alternatingly measured in the gym’s supply duct and weight room. The Indoor Model of Aerosols, Gases, Emissions, and Surfaces (IMAGES) uses the inorganic aerosol thermodynamic equilibrium model, ISORROPIA, to estimate the partitioning of inorganic aerosols and corresponding gases. In this study herein, measurements from the ATHLETIC campaign were used to evaluate IMAGES’ performance. Ammonia emission rates, nitric acid deposition, and particle deposition velocities were related to observed occupancy, which informed these rates in IMAGES runs. Initially, modeled indoor inorganic aerosol concentrations were not in good agreement with measurements. A parametric investigation revealed that lowering the temperature or raising the relative humidity used in the ISORROPIA model drove the semivolatile species more toward the particle phase, substantially improving modeled-measured agreement. One speculated reason for these solutions is that aerosol water was enhanced by increasing the RH or decreasing the temperature. Another is that thermodynamic equilibrium was not established in this indoor setting or that the thermodynamic parametrizations in ISORROPIA are less accurate for typical indoor settings. This result suggests that applying ISORROPIA indoors requires further careful experimental validation.

This work applies an indoor aerosol model, IMAGES, that estimates the partitioning of inorganic aerosol components and their corresponding gas-phase species with ISORROPIA by leveraging measurements from a university athletic center and derived relationships between occupancy and nitric acid deposition, particle deposition, and ammonia emissions. This study highlights that applying ISORROPIA indoors can sometimes result in inaccurate gas-particle partitioning. However, forcing the model to predict increased particle water by either adjusting relative humidity up or temperature down will result in accurate gas-particle partitioning.