ACS ES&T Air最新文献

[This corrects the article DOI: 10.1021/acsestair.3c00102.].

High ambient relative humidity (RH) poses a substantial challenge to the accuracy of low-cost optical sensors used for measuring the fine particulate matter (PM_2.5) concentration. In this study, we developed a novel, practical, and feasible framework for mechanistically correcting low-cost PM_2.5 sensor measurements under high-humidity conditions by quantitatively separating aerosol liquid water mass (ALW) using the widely available EPA Chemical Speciation Network (CSN) data set, after accounting for the necessary optical calibration procedures that affect sensor performance at elevated RH. We introduced two key correction processes for a low-cost optical PM_2.5 measurement system comprising a nephelometer and an optical particle counter: (1) optical calibration grounded in Mie theory to account for variations in sensor performance driven by aerosol size distribution, refractive index, and hygroscopic growth, and (2) determination of ALW to estimate dry-equivalent PM_2.5 mass concentrations under high RH conditions. The corrected PM_2.5 data exhibit strong agreement with EPA reference measurements, affirming the robustness of the proposed correction framework. Furthermore, the quantification of ALW offers valuable insights for advancing aqueous-phase aerosol chemistry and secondary aerosol formation studies. For regions without colocated CSN data, we provide practical guidance for applying these correction methods using surrogate information. Overall, the methodologies developed in this work are expected to significantly enhance the accuracy and applicability of low-cost optical PM_2.5 sensors in humid environments.

Residents of agricultural communities may experience higher exposures to pesticides due to their proximity to agricultural operations. We applied a novel measurement approach, using Ultrasonic Personal Air Samplers (UPAS), to quantify particulate matter and organophosphate pesticides in air in California's Central Valley. We collected 124 personal, 126 in-home, and 32 outdoor air samples with 66 adults from 37 rural households in 2023 and 2024. We detected chlorpyrifos, acephate, malathion, diazinon, and naled in air samples. We detected gas-phase chlorpyrifos in 63% of personal samples and 86% of homeseven though use of chlorpyrifos has been banned in California (with few exceptions) since January 2021at 24 h average concentrations ranging up to 13 ng m^-3 (personal) and 5.8 ng m^-3 (in-home). We did not detect chlorpyrifos in outdoor air samples. Using linear mixed models, we found that higher indoor air temperatures and having more carpets/rugs were associated with higher indoor chlorpyrifos concentrations. The concentrations we measured were well below the California Department of Pesticide Regulation's health screening level of 510 ng m^-3 for chronic exposure to chlorpyrifos in air; nevertheless, our results suggest that persistent chlorpyrifos in home environments continues to contribute to nondietary exposure among California residents.

Two solutions containing ~500 mg/L of perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) were atomized at two post-flame locations within a natural gas-fired pilot-scale combustor with peak temperatures of ~860 °C and ~750 °C. The thermal destruction of PFOS and PFOA and the formation of fluorocarbon products of incomplete combustion (PICs) were analyzed using EPA Other Test Method (OTM)-45, a prepublication version of EPA OTM-50, an activated carbon-based thermal desorption (TD) tube gas chromatography/mass spectrometry (GC/MS) method, and two real-time methods including iodine-adduct chemical ionization mass spectrometry (CIMS) and Fourier transform infrared spectrometry (FTIR). Destruction efficiencies (DEs) determined for PFOS by OTM-45 and for PFOA by both OTM-45 and CIMS, were >99.99% for both peak injection temperatures. OTM-45 and CIMS confirmed the presence of several perfluorocarboxylic acids (PFCAs) as PICs. These PFCAs included trifluoroacetic acid (TFA) and perfluoropropionic acid (PFPrA) for both solutions and included the formation of PFOA from PFOS and similarly perfluoroheptanoic acid (PFHpA) from PFOA. PFCA concentrations and the relative amounts of PFOA and PFHpA increased at the lower temperature. OTM-50 and the TD tube analysis identified numerous fluorocarbon PICs including 1H-pefluoroalkanes, and perfluoroalkanes such as trifluoromethane (CHF₃) and hexafluoroethane (C₂F₆).

Biogenic volatile organic compounds (BVOCs), a dominant source of secondary organic aerosol (SOA) globally, exhibit emission rates and compositions that are plant species-specific and vary with environmental stressors. A common outcome of plant stress is increased emissions of acyclic terpenes. The paucity of information about acyclic terpene SOA chemistry contributes to uncertainties in predictions of SOA global loadings and impacts on Earth's radiative budget, particularly in a changing climate where acyclic terpene emissions could become more prominent. This study compared properties of SOA derived from hydroxyl radical (OH) oxidation of acyclic and cyclic monoterpenes (β-ocimene, α-pinene) and sesquiterpenes (β-farnesene, β-caryophyllene). Single-particle mass spectrometry was used for assessing shape, density, and evaporation kinetics of size-selected SOA particles, and nanospray desorption electrospray ionization high-resolution mass spectrometry (nano-DESI-HRMS) was used to measure the molecular composition of SOA. Acyclic terpene SOA exhibited higher viscosity and lower volatility compared to cyclic terpene SOA, and had a greater volume fraction remaining (VFR) after ∼24 h of evaporationapproximately 1.3-1.6 times higher VFR than that of cyclic terpene SOA. Additionally, HRMS analysis revealed greater chemical diversity and higher fractions of extremely low-volatility compounds (56-62% ELVOC/LVOC) in acyclic terpene SOA compared to cyclic counterparts (25-37% ELVOC/LVOC). Our findings highlight the potential importance of accounting for acyclic terpene aerosol chemistry under conditions of plant stress to improve predictions of SOA loadings and impacts.

A new calibration approach, the Network Calibration Algorithm (NCA), was developed and applied to low-cost sensors measuring PM_2.5, O₃, NO₂, NO, and CO at 38 New York State Mesonet sites in the New York City Metropolitan Area. A single low-cost sensor package (the "keystone" package) was colocated alongside regulatory-grade (reference) instruments at the New York State Department of Environmental Conservation Queens College monitoring site for 16 months. For each pollutant, hourly data from the keystone package and reference instruments were used to train a single calibration model that was subsequently applied to all packages at field sites across the network. The calibration models included multiple linear regression (MLR) for CO and a hybrid approach that combined MLR with a Random Forest model for PM_2.5, O₃, NO₂, and NO. The performance of the NCA-calibrated low-cost sensors was quantified using multiple evaluation data sets, with a focus on accuracy and long-term stability over the 16-month period. The performance statistics were consistent with or better than previous reports for similar low-cost sensors, and the NCA was able to compensate for sensor degradation and drift. Empirical estimates of the field limit of detection for each of the low-cost sensors are presented.

Wildland-urban interface (WUI) fires pose unique environmental pollution challenges due to the combustion of both natural vegetation and synthetic building materials. Following the 2025 Palisades and Eaton wildfires in Los Angeles, we conducted a field study to characterize indoor air quality and surface contamination in 19 homes before reoccupancy. Indoor PM_2.5 and PM₁₀ concentrations averaged 3.45 and 31.66 μg/m³, respectively, with several homes showing indoor-to-outdoor (I/O) ratios of >1 (particularly for PM₁₀) compared to typical I/O values of 0.45-0.8 in residences, indicating persistent indoor particle reservoirs. Depending on the air-exchange rate, elevated indoor PM levels in noncleaned homes may arise from two contrasting mechanisms: low ventilation that traps resuspended fire residues triggered by movements during sampling and high ventilation that induces turbulence and disturbs heavily contaminated entry zones. Regression analysis suggested that proximity to the fire, absence of air purifiers, use of non-HEPA vacuums, and open windows during the fire significantly increased indoor PM levels, explaining 73% (PM₁₀) and 86% (PM_2.5) of the variation across homes. Airborne metal concentrations were below health-based thresholds; however, surface wipe samples revealed widespread contamination, with potassium, magnesium, aluminum, and iron frequently exceeding 1000 μg/ft², and detectable levels of zinc, copper, and manganese in many homes. Lead concentrations exceeded the EPA's dust clearance levels in multiple homes, especially on window sills and entry floors. Our findings highlight that while airborne risks may subside within weeks after the fire, indoor surfaces can retain fire-related pollutants, presenting ongoing exposure risks even 2 months after the fire.

Fires occurring at the wildland-urban interface (WUI) can produce smoke, that contains unique chemicals from the combustion of urban structures, which can then contaminate nearby buildings and affect indoor air quality. Assessing property loss and possible occupant exposure to persistent contamination from WUI smoke is challenging, in part because of a lack of measurements detailing chemical contamination in real indoor environments after WUI events. Here, we mimic contamination from a WUI fire by repeatedly exposing a test house to smoke from combustion of residential building surrogates and measure the persistence of volatile nonmethane organic gas (NMOG) contamination. Over the 1.5 month experimental period, we observed an increase in emission rates of 31 NMOGs, indicating the formation of surface reservoirs indoors that increase with subsequent burns. We observe off-gassing time scales of less than 10 days for many highly volatile NMOGs like acetonitrile, acrylonitrile, and styrene. Other NMOGs, like naphthalene and C12 aromatics, took longer than 10 days to off-gas and show emissions persistently elevated above background for at least three months after the end of the experiments. The NMOG emissions from contamination in the test house were lower when compared with a house affected by the Marshall Fire in Colorado. However, the NMOG off-gassing times measured in the test house were longer.

Reliable elemental analysis is important for understanding mineral dust mass concentrations, composition, sources, and atmospheric processing. X-ray attenuation of light elements in widely used X-ray fluorescence (XRF) measurements can lead to underestimated dust mass and inaccurate dust composition, yet attenuation corrections are often neglected in ambient particulate matter (PM) analysis. This study experimentally quantifies attenuation for silicon and aluminum by comparing XRF and gravimetric measurements of samples with known compositions. Silica (SiO₂), alumina (Al₂O₃), and Arizona test dust (ATD) were aerosolized and collected on Teflon filters to generate samples with varying mass loadings and particle size ranges. Results validated that attenuation increases with both mass loading and particle size. Greater Si attenuation observed in ATD than in SiO₂ at equivalent mass loading and size range indicates that other crustal elements enhance Si attenuation. Theoretical models considering only mass loading or particle size underestimated the measured attenuation. We developed empirical equations to correct for Si and Al attenuation. Applying these equations, with a size scaling factor for nondust species, to ambient dust-dominated PM samples from the global Surface PARTiculate mAtter Network (SPARTAN) increased dust concentrations by 21% in PM_2.5 and 29% in PM₁₀. This work demonstrates the importance of considering attenuation effects in XRF analysis for accurate dust inference from measured elements.

The mechanisms of secondary organic aerosol (SOA) formation are not yet fully understood. The relative abundance of hydroperoxyl radicals (HO₂) and peroxy radicals (RO₂) affects SOA properties, but chamber experiments often underemphasize the role of HO₂. To clarify their contribution, this study compares the composition and volatility of SOA formed by the hydroxyl radical (OH) oxidation of α-pinene under low and high HO₂/RO₂ regimes with a constant OH concentration. The particle-phase was characterized with a Filter Inlet for Gases and AEROsols coupled to an iodide Chemical Ionization Mass Spectrometer (FIGAERO CIMS), and a CIMS with NO₃ ^- ionization was used for gas-phase measurements. High HO₂/RO₂ conditions weakened the particle-phase monomer (C₁₀), fragment (C_4-9), and accretion product (C_11-20) signals by 34%, 29%, and 78%, respectively, compared to low HO₂/RO₂ conditions. The only species with an increased signal (180%) was C₁₀H₁₈O₇. The gas-phase changes align with those in the particle-phase within a factor of 2. Overall, the organic mass was reduced by 47% and 39% for particle and gas-phases, respectively. Bulk SOA volatility (log C*) increased slightly from -0.22 μg m^-3 to -0.1 μg m^-3, reflecting the suppression of low volatility accretion products but formation of high volatility hydroperoxide monomers. This study highlights the importance of HO₂ for SOA formation and model predictions.