Spatial and seasonal variations in the carbon and lead isotopes of PM2.5 in air of residential buildings and their applications for source identification

Evaluating the representativeness of atmospheric PM2.5 data for indoor exposure: insights from concentrations, chemical compositions, and sources

Studies relied on atmospheric PM2.5 data to estimate health risks and sources, but its representativeness for indoor air remains unclear. This study placed an atmospheric PM2.5 sampler on the rooftop of a three-story building, and indoor and outdoor (balcony) samples were collected from study houses within a 5 km radius of the atmospheric sampling site during low and high PM2.5 seasons to evaluate the representativeness of atmospheric PM2.5 data. The average PM2.5 concentrations were 15.4 ± 7.1 μg/m3 (indoor), 18.9 ± 7.0 μg/m3 (outdoor), and 13.9 ± 6.1 μg/m3 (atmospheric). Atmospheric PM2.5 concentrations were significantly associated with indoor and outdoor PM2.5, but outdoor PM2.5 concentrations were higher. Source identification revealed that traffic-related emission was a major contributor to PM2.5 across all sites and seasons, while long-range transport from China was another source during the high PM2.5 season based on lead isotope ratios. Crustal elements and construction dust, identified through positive matrix factorization, were higher in both indoor and outdoor air than in the atmosphere. Elements from industrial or traffic emissions showed similar concentrations across different sampling sites. The average ratios of indoor to outdoor or atmospheric PM2.5 concentrations were 0.84 ± 0.27 and 1.18 ± 0.37, respectively. In conclusion, atmospheric PM2.5 can be used to estimate PM2.5 exposure and element concentrations from industrial or traffic emissions in indoors; however, it underestimates the contributions of crustal elements and construction dust. Ambient PM2.5 samples from outdoor or atmospheric environments should be considered when comparing their influence on indoor air across studies.

Advanced Characterization of Industrial Smoke: Particle Composition and Size Analysis with Single Particle Aerosol Mass Spectrometry and Optimized Machine Learning

With the acceleration of industrialization, industrial smoke particles containing complex chemical compositions and varying particle sizes pose a serious threat to the environment and human health. As a powerful tool for aerosol measurement, mass spectrometry can effectively analyze particulate matter. However, due to the high dimensionality and complexity of mass spectrometry data, research on the relationship between particle size and composition remains very limited. To address this gap, this study innovatively combines single particle aerosol mass spectrometry (SPAMS) with optimized machine learning, achieving for the first time the precise prediction of smoke particle size based on mass spectrometry data. Nonlinear dimensionality reduction of mass spectrometry data was performed using kernel principal component analysis (KPCA) to extract key features. Combined with random forest (RF) for prediction, the R2 of the test set reached 0.843 after optimization. Additionally, to address the issue of imbalanced sample distribution, a systematic stratified random sampling algorithm (SSRSA) was developed, significantly enhancing the model's generalization ability and stability during training and testing. This study also simulated a soldering scenario to analyze lead (Pb) isotope abundances and particle size distributions in smoke at different soldering temperatures. Results indicate a significant correlation between the abundance of lead isotopes and the soldering temperature. Additionally, as the soldering temperature increases, the proportion of smaller sized particles increases noticeably. This research provides an innovative approach for precise analysis of industrial smoke particle composition and size, offering critical scientific insights for health risk assessment and the development of pollution control strategies.

Mitigating air and noise pollution through highway capping: The Bundang-Suseo Highway Cap Project case study

Highways, while vital for transportation, often lead to heightened air and noise pollution, adversely affecting nearby communities. This study delves into the effectiveness of highway capping, a sustainable urban development strategy, in addressing these environmental challenges, with a specific focus on the Bundang-Suseo Highway in South Korea. This study employed a multifaceted approach, incorporating on-road monitoring, in situ measurements, and vertical assessments using UAVs. Following the cap's installation, the area experienced more stable pollutant levels, marking a notable shift from the previously fluctuating conditions heavily influenced by the highway. In-depth in situ monitoring near the cap revealed significant reductions in noise and pollutants like UFP and BC. Furthermore, UAV monitoring captured these changes in pollutant levels at different altitudes. Notably, the installation of the highway cap led to increased PM2.5, PM10, and NO2 levels at ground level, but a decrease above the cap, emphasizing the critical importance of intentional highway cap design in enhancing urban air quality and reducing exposure to harmful pollutants. This research yields invaluable insights for urban planners, health authorities, and policymakers, aiding the precise identification of pollution-prone areas and advocating for improved highway cap design to enhance urban environments.

Impact of agricultural activity on PM2.5 and its compositions in elementary schools near corn and rice farms

Agricultural activity is an important source of particulate matter <2.5 μm in size (PM2.5) in rural areas. In Taiwan, many elementary schools are surrounded by farms, and studies investigating the impact of agricultural activity on air quality in schools are required. We collected PM2.5 samples from the classrooms of elementary schools near corn and rice farms during the crop cultivation stages and analyzed their concentrations and compositions to investigate whether agricultural activity affects the schools' air quality. We found that the average ratio of PM2.5/PM10 (<10 μm in particle size) was <0.6 in the school near the corn farm, and that the indoor PM2.5/PM10 ratio was significantly associated (r = 0.93, p < 0.05) with the outdoor ratio. Moreover, the potassium (K) concentration in the school near the corn farm (189.2 ± 119 ng/m3) was higher than that near the rice farm (140.9 ± 116.0 ng/m3). There were higher concentrations of K and crustal elements, and a greater crustal elements/heavy metals ratio, in the school near the corn farm during the sowing and soil covering stages than during other cultivation stages. Positive matrix factorization (PMF) results indicate that agricultural activity was a predominant contributor of PM2.5 in the schools near corn and rice farms, however, PM2.5 from industrial and traffic emissions also affected schools' air quality. In summary, agricultural activity influenced the air quality of schools, especially near the corn farm. Governments should develop air quality management policies to reduce the risk of children suffering exposure to high particle concentrations in these schools and further suggest that the impact of industrial and traffic emissions on air quality also requires attention.

Investigation of source and infiltration of toxic metals in indoor PM2.5 using Pb isotopes during a season of high pollution in an urban area

Lead (Pb) isotope ratio has been applied in source investigation for particulate matter in size < 2.5 μm. However, arsenic (As) and cadmium (Cd) are carcinogenic to human and their isotope analysis is difficult. This study investigated whether the Pb isotope ratio was a useful indicator in identifying the sources of As and Cd indoors and investigating its influencing factors. This study also calculated the infiltration factor (Finf) for metals to assess the influences of indoor- and outdoor-generated metals to indoor air. The As and Cd concentrations in indoor air were 0.87 ± 0.69 and 0.19 ± 0.15 ng/m3, respectively; the corresponding values for outdoor air were 1.44 ± 0.80 and 0.33 ± 0.19 ng/m3. The Finf of As and Cd were 0.60 ± 0.37 and 0.58 ± 0.39, and outdoor was a predominant contributor to indoor As and Cd. The Pb isotopes ratio indicated that traffic-related emission was a major contributor to Pb. The Pb concentration was associated with those of As and Cd in indoor or outdoor air, as was the 208Pb/207Pb ratio in outdoor air. Significant correlations between indoor 208Pb/207Pb values and As and Cd concentrations in indoor air were found only in study houses with air change rate > 1.5 h-1. These findings suggested that traffic-related emission was identified as a major source of As and Cr. The 208Pb/207Pb is a useful indicator in investigating the source of As and Cd; however, the air change rate influences the applicability of this approach on source identification.

A study to characterize the lead isotopic fingerprint in PM2.5 emitted from incense stick and cigarette burning

The incense sticks and cigarettes burning are key sources of particulate matter with a diameter of ≤ 2.5 μm (PM_2.5) in indoor and outdoor air. While lead (Pb) isotope ratios provide valuable insights into the origin of particle pollution, their applicability for investigating these source remains unclear. The Pb isotope ratios in the PM_2.5 emitted from these two sources were analyzed, and effects of brands or nicotine contents on the ratios were assessed. In addition, As, Cr, and Pb were analyzed to investigate whether Pb isotope ratios can serve as an indicator for the source investigation of these metals. We found that average ratios of ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁶Pb/²⁰⁷Pb, and ²⁰⁸Pb/²⁰⁷Pb in cigarettes were heavier than those in incense sticks. Scatter plots of Pb isotope ratios indicated an overlap of values for incense sticks or cigarettes linked to different brands, in that ratios for cigarettes with high nicotine content were heavier than for those with low nicotine content. Scatter plots of As, Cr, or Pb concentration against Pb isotope ratios clearly distinguished the effects of cigarette burning versus incense sticks with respect to PM_2.5 of these metals. Results indicate that brand differences did not affect the determination of PM_2.5 in these two sources. We suggest that Pb isotope ratios can be a useful tool in investigating the influence of incense sticks and of cigarettes (with high or low nicotine content) burning to PM_2.5 and associated metals.