PM Deposition Research Articles

Evaluation of Particulate Matter Deposition Efficiency and Air Quality Improvement by Vertical Shrub and Climber Walls

Fine particulate matter poses a significant health risk indoors, making indoor air quality improvement crucial. Vertical greenery systems offer a promising solution, but selecting suitable plant species remains a challenge. This study evaluated the PM deposition and air quality impact of six ornamental plants (climbers and shrubs) in a controlled chamber. Almost all plants reduced CO2 by 20%, while PM deposition varied by species, with Petunia hybrid being the most efficient. Total leaf area showed the strong correlated with PM deposition. These findings confirm the potential of ornamental plants, particularly those with large total leaf area, for PM reduction in vertical greenery systems. Further research with a wider range of plants and advanced characterization techniques is needed to refine our understanding and develop practical guidelines for their effective use in indoor air purification.

Nature-based solution for mitigation of pedestrians’ exposure to airborne particles of traffic origin in a tropical city

This study investigated the effectiveness of vegetation barriers (VBs) planted along roadsides in a highly urbanized tropical Asian city-state to mitigate pedestrians’ exposure to airborne particles (PM) of traffic origin for the first time. Mobile and fixed-site measurements of black carbon (BC) and ultrafine particles (UFPs) were conducted with three types of VBs (green walkway covered with creepers; hedgerow; and three-layer hedges with varying heights) using portable PM devices. The three-layered hedges showed higher BC and UFPs reductions (the average reduction of about 60%) than the other two configurations (20–40%). Deposition of PM with diverse size, morphology and elemental composition onto VBs leaves plays an important role in reducing PM exposure concentration, providing health benefits to pedestrians involved in active mobility on roads. Our findings provide a scientific basis for formulating appropriate guidelines for selecting and installing VBs to reduce the inhalation exposure of pedestrians to PM of traffic origin.

Effect of air quality improvement by urban parks on mitigating PM2.5 and its associated heavy metals: A mobile-monitoring field study

Field mobile monitoring of PM2.5, equipped with a highly accurate device, was performed for two types of urban parks in Taiwan. Measurements were taken in the morning and evening rush hours, on certain weekdays and weekends, every month over a year. We designed six calculation schemes of the rate of PM2.5 mitigation by urban parks to comprehensively compare the average and maximum mitigation effects in relation to the vegetation barriers. The mitigation rate, from the lowest (2.51%) to the highest (35.57%) depended on the calculation schemes. The Taipei Botanical Garden (TBG) with a dense, multilevel forest has a stable PM2.5 mitigation effect and strong ability to improve air quality inside the park under severe PM2.5 pollution. In contrast, Zhonghe No.4 Park (ZHP), an open park with mostly a single-storied stand, has variable PM2.5 mitigation effect, leading to either quick dissipation or accumulation of PM2.5 inside the park. Furthermore, the dry deposition of PM and the associated heavy metals were investigated using camphor trees as bioaccumulators. Dry deposition flux of the leaf-deposited PM2.5 exhibited similar results in ZHP; whereas, noticeable higher results were observed inside TBG. In addition, most of the PM2.5 deposition flux from field estimations were similar to those in i-Tree Eco when considering the loss of mass due to the dissolution through water filtration, indicating that i-Tree Eco may be reliable to model the removal of PM2.5 in the parks in Taiwan. Moreover, we examined nine heavy metals’ content in the deposited PM, and most of the detectable elements were significantly higher outside both parks, demonstrating the mitigation effects of urban parks in reducing not only the PM2.5 concentration but also the toxicity of the pollutant. This study provides direct evidence of the important ecosystem services, namely air quality improvement and biomonitoring effect, derived from urban parks.

Protecting playgrounds: local-scale reduction of airborne particulate matter concentrations through particulate deposition on roadside ‘tredges’ (green infrastructure)

Exposure to traffic-related particulate air pollution has been linked with excess risks for a range of cardiovascular, respiratory and neurological health outcomes; risks likely to be exacerbated in young children attending schools adjacent to highly-trafficked roads. One immediate way of reducing airborne PM concentrations at the local (i.e., near-road community) scale is installation of roadside vegetation as a means of passive pollution abatement. Roadside vegetation can decrease airborne PM concentrations, through PM deposition on leaves, but can also increase them, by impeding airflow and PM dispersion. Critical to optimizing PM removal is selection of species with high particle deposition velocity (Vd) values, currently under-parameterised in most modelling studies. Here, the measured amounts of leaf-deposited magnetic PM after roadside greening (‘tredge’) installation, and measured reductions in playground PM, particle number and black carbon concentrations demonstrate that air quality improvements by deposition can be achieved at the local, near-road, community/playground scale. PM deposition on the western red cedar tredge removed ~ 49% of BC, and ~ 46% and 26% of the traffic-sourced PM2.5 and PM1, respectively. These findings demonstrate that roadside vegetation can be designed, installed and maintained to achieve rapid, significant, cost-effective improvement of air quality by optimising PM deposition on plant leaves.

Ambient concentrations and dosimetry of inhaled size-segregated particulate matter during periods of low urban mobility in Bragança, Portugal

The restrictive measures in place during the COVID-19 pandemic provided a timely scenario to investigate the effects of human activities on air quality, and the extent to which mobility reduction strategies can impact atmospheric pollutant levels. Real-time concentrations of PM1, PM2.5 and PM10 were measured using a mobile platform in a small city of Portugal, during morning and afternoon rush hours, in two distinct phases of the pandemic: emergency phase (cold period, lockdown) and calamity phase (warm period, less restricted). The Multiple-Path Particle Dosimetry Model (MPPD) was used to calculate the PM deposition for adults. Large spatio-temporal variabilities and pronounced changes in mean PM concentrations were observed, with lower concentrations in the calamity phase: PM1 = 2.33 ± 1.61 μg m−3; PM2.5 = 5.15 ± 2.77 μg m−3; PM10 = 23.30 ± 21.53 μg m−3 than in the emergency phase: PM1 = 16.85 ± 31.80 μg m−3; PM2.5 = 30.92 ± 31.93 μg m−3; PM10 = 111.27 ± 104.53 μg m−3. These changes are explained by a combination of meteorological factors and local emissions, mainly residential firewood burning. Regarding regional deposition, PM1 was the main contributor to deposition in the tracheobronchial (5%) and pulmonary (12%) regions, and PM10 in the head region (92%). In general, total deposition doses were higher for males than for females. This work quantitatively demonstrated that even with a 38% reduction in urban mobility during the lockdown, the use of firewood for residential heating is the main contributor to the high concentrations of PM and the respective inhaled dose.

Assessment of Indoor Air Pollution through Fine Particle Capturing Potential and Accumulation on Plant Foliage in Delhi, India

The dry deposition of PM on foliage of indoor plants in the households of Delhi has been reported in this study. It was observed that dustfall fluxes were higher at the industrial site (MH) as compared to the residential site (DH). Seasonal variations in dust deposition indicated that it was highest in the winter season and lowest in the monsoon season. Chemical profiling of the deposited dust marked that dust was less basic at MH as compared to DH and Ca2+ was ubiquitously the most abundant cation at both sites whereas Cl- and SO42- were the most abundant anions at DH and MH, respectively. Abundance of K+, NO3- and NH4+ etc. indicated the influence of anthropogenic activities. The number of PM deposited on the foliar surfaces of indoor plants was also estimated and divided into PM1, PM2.5 and PM10 based on their size because particle count is more appropriate than particle mass for estimation of finer PM. PM accumulation on the foliar surfaces of selected plants for the present study followed the order, PM1 > PM2.5 > PM10 at both the sites. The foliar micromorphology of abaxial surfaces of the plants accounted for significant interspecies variability due to difference in presence of grooves and undulations, high stomatal density, epicuticular wax etc. Leaves with densely arranged grooves and ridges showed more PM accumulation. Investigation of plants with respect to dust deposition and selection of species which can perform the dual functions of improving air quality and providing aesthetic value are needed for understanding the role of vegetation in air pollution mitigation approaches in real life environment.

Wheat Cultivar Growth, Biochemical, Physiological and Yield Attributes Response to Combined Exposure to Tropospheric Ozone, Particulate Matter Deposition and Ascorbic Acid Application.

In the present study wheat (Triticum aestivum) cultivar HD 2967 was exposed to ambient and elevated levels of O3 and PM deposition, with and without exogenous application of ascorbic acid (AA). Cultivar HD 2967 exposed to eight treatments in free air O3 enrichment facility and the assessed results showed that wheat cultivar, growth, biochemical, physiological and yield attributes were variably but adversely affected by combined exposure to O3 and PM deposition. PM deposition clogged stomata and enhanced leaf temperature. However, plants exposed to O3 and PM deposition and treated with AA exhibited less reduction in yield as compared to plants exposed to O3 and PM deposition without AA treatment. The decline in grain yield of HD 2967 due to combined exposure of O3 and PM deposition were in the range of 4%-17%. AA spray partially mitigated ozone and PM deposition adverse impact and enhanced wheat yield by 16%.

The hallmarks of environmental issues and the brain

BACKGROUND AND AIM: The aim of this presentation is to discuss the knowledge regarding the impact of the hallmark environmental insults on the brain. Air pollution, noise, heat, light at night, industrial chemicals, and lack of green space have been associated with the impairment of brain development and function and higher risk of neurological diseases and neurodegeneration. METHODS: Several hallmarks (oxidative stress, methylation, endocrine disruption, mitochondrial disfunction, telomers, intravesicular cells, miRNA, microbiome, autonomous nervous system irritation) have been suggested to underline these relationships via direct and indirect pathways. The nervous system itself controls the body's physiological processes and as such could impair the cardiovascular, metabolic/endocrine, and respiratory systems, among others. RESULTS:The efforts in understanding the intermediate role of the cellular hallmarks between the exposure and the brain effects is a path to establish causal relationships. For instance, a key development is to discover the windows of greatest sensitivity of structural and functional brain changes to air pollution. The brain has the widest vulnerable window among all systems. Prenatal exposures may have more severe consequences for the brain because brain structures are forming during this period and may cause permanent brain injury and predict cognitive impairment later in life. Supporting the importance of the prenatal period, mice experiments consistently reported that prenatal exposure to fine PM and diesel exhaust could induce inflammatory reactions and structural changes in several brain regions related with the myelination process which has been replicated in humans, in part, through impairing placental function via PM deposition in the placenta or indirectly via several of the hallmarks in peripheral blood and in the placenta itself. CONCLUSIONS:Hallmarks could be relevant for informing about the persistence or tracking of the effects until later life. It is important to simultaneously study the effect of these hallmarks together on the brain in relation to the exposome. KEYWORDS: omics technologies,Neurologic and mental health outcomes, air pollution, chemical exposues, climate

Effectual removal of indoor ultrafine PM using submicron water droplets

Exposure to ultrafine airborne particulate matter (PM1.0) poses a significant risk to human health and well-being. Examining the effect of submicron water droplets on the removal of ultrafine PM is timely and important for mitigating indoor ultrafine PM, which is difficult to filter out from incoming air. In this study, submicron water droplets were made by using a nanoporous membrane and an ultrasonic module of a commercial household ultrasonic humidifier (UH) for effectual ultrafine PM removal. The effect of water droplet size on indoor PM removal was experimentally investigated. Variations in the normalized PM concentration, removal efficiency and deposition constants were evaluated by analyzing the temporal variation in PM concentration inside a test chamber. The measured PM deposition constants were compared with the results of other previous studies. As a result, submicron water droplets of 800 nm in mean diameter were generated by ultrasonic module combined passive nanoporous membrane, and PM1.0 concentration decreased by 30% in the initial 30 min. Compared with micron-sized water droplets, PM1.0 removal efficiency improved by approximately two times higher. Moreover, the substitution of the experimental results into a theoretical model ascertained that PM collection efficiency is increased by approximately 103 levels as the size of water droplets decreases. These results would be utilized in the development and implementation of effective strategies for indoor PM removal.

Dry deposition of dust particles during medium- and high-level dust storms to a forest canopy in a semi-arid region

In the present study the impact of forest canopy on the spatial distribution of PM10 concentration during dust events in a region, which is subjected to frequent occurrences such as dust storms is investigated. The developed two-dimensional model is based on the application of theory of turbulent diffusion in the forest canopy in conjunction with model of dust particles deposition to vegetation elements. The leaf area density (LAD) distribution with height as well as dust particle size distribution are taken into account. The initial wind velocity profiles on the windward side of the forest were fitted from data obtained in field measurements in the studied region. The resulted dust transport in the forest canopy was validated by comparison of theoretical results with the empirical data in the studied region. Using the suggested model, we analyzed the evolution of wind velocity profiles in and above the forest canopy as well as the process of dry deposition of PM to vegetation elements. Numerical calculations performed using the developed model showed that in dust storms, PM10 concentrations at the leeward side of the forest are reduced by ≈ 16–18% depending on dust storm level. We also found that inside the canopy the ratio of PM10 concentrations between the points along the studied transect and windward side (not affected by the forest) is higher, the higher the level of the dust storm. Our model results of the atmospheric PM distribution show fairly good agreement with the data of the field measurements.

Extended filtration model for diesel particulate filter based on diesel particulate matter morphology characteristics

This study proposes an extended filtration model for diesel particulate filter based on diesel particulate matter morphology characteristics. This model introduces the parameter of variable effective density to modify the filtration model and develops the global filtration correction coefficient ϑp to consider the changes of PM morphological parameters. The specific calculation formulas of these two parameters are given in the paper. The filtration model proposed in this paper is based on the theory of spherical particles packed bed. Results show that the prediction error of the extended model can be as low as 0.66%, the average prediction error is 1.17%, and the prediction accuracy is improved by 34.08% compared with the former model. Filtration efficiency growth coefficient Egro exhibits a bimodal distribution, and the PM in the two particle size ranges of 110–140 nm and greater than 500 nm is more sensitive to the micro-changes in parameters caused by PM deposition in the porous substrate. In addition, the filtration time interval has the greatest influence on the growth rate, especially for the small and medium particle sizes ranging between 166.5 and 294.3 nm.

Ecological Assessment of Particulate Material (PM5 and PM10) in Urban Habitats

Trees are especially useful biological indicators. We tested the suitability of tree leaves (Common Lime) to assess PM5 and PM10 deposition in the three summer months of 2018 in Debrecen city, Hungary. We also tested the usefulness of the cheap and simple gravimetric method to assess the PM deposition, and compared to the expensive, but standard laser diffraction method. We found significant differences between the concentrations of PM10 deposited on tree leaves, and on dust traps. A significant difference was found in the concentration of PM5 only in July. A significant difference was also found in the concentration of PM10 among months based on leaves and dust traps. For PM5 there was a significant difference among months based on leaves deposition. We found a significant positive correlation between the PM10 concentration deposited on leaves and on dust traps. A positive correlation was found between the concentration of PM based on the gravimetric and laser diffraction measurement methods. Our findings pointed out the particulate material’s washing by rain from leaves; thus, dust deposition on the surface of leaves is limited. Our results demonstrated that trees play an important role in the mitigation of air pollution, and they are a useful indicator of PM deposition for biomonitoring studies.

Magnetic biomonitoring of atmospheric dust using tree leaves of Ficus benjamina in Querétaro (México).

There are limited economic and reliable tools to monitor the effects of airborne particulate matter PM originating from rapid industrialization, urbanization, population growth, and economic development. It is now well established that urban PM contains magnetic particles along with other air pollutants. The velocity and temporal variability of the deposition of such PM on tree leaves are subject to the pollution sources, climate, and local atmospheric conditions. Therefore, these variables have to be taken into account during a biomonitoring. This study presents a magnetic biomonitoring in the city of Querétaro. In the city's metropolitan area, the most abundant and perennial tree species for biomonitoring is Ficus benjamina. For leaves of this species, the number of days needed for collection NDNC was measured, taking into account the meteorological conditions and the time at which they reached the saturation of airborne PM (pollutants). By means of sequential sampling, we identified that the minimum NDNC after a rainfall > 3mm is 15days. In such a period, total suspended particle TSP depositions reach its dynamic equilibrium. This behavior can be observed from measurements of specific magnetic susceptibility χ in Ficus benjamina samples and their comparison with TSP depositions collected with traditional Hi-Vol monitoring systems. After the NDNC calculation, a magnetic monitoring was performed with the biomonitor Ficus benjamina to evaluate the air quality at different sites in the metropolitan area every month for a period of 5months. Values of χ ranged from 0.45 to 18.52 × 10-8m3kg-1. The species Ficus benjamina can be used as a biomonitor in the city of Querétaro only in seasons (winter-spring) with no or low rainfall. The species has the advantage of providing current PM information about a specific period of time.

Ozone and particle fluxes in a Mediterranean forest predicted by the AIRTREE model

Mediterranean forests are among the most threatened ecosystems by the concurrent effects of climate change and atmospheric pollution. In this work we parameterized the AIRTREE multi-layer model to predict CO2, water, ozone, and fine particles exchanges between leaves and the atmosphere. AIRTREE consists of four different modules: (1) a canopy environmental module determines the leaf temperature and radiative fluxes at different levels from above to the bottom of the canopy; (2) a hydrological module predicts soil water flow and water availability to the plant's photosynthetic apparatus; (3) a photosynthesis module estimates the net photosynthesis and stomatal conductance, and (4) a deposition module estimates ozone and PM deposition sinks as a function of the resistances to gas diffusion in the atmosphere, and within the canopy and leaf boundary layer. We describe the AIRTREE model framework, accuracy and sensitivity by comparing modeling results against long-term continuous Eddy Covariance measurements of ozone, water, and CO2 fluxes in a Mediterranean Holm oak forest, and we discuss potential application of AIRTREE for ozone-risk assessment in view of availability of a large observational database from ecosystems distributed worldwide.

Fluorescent reconstitution on deposition of PM2.5 in lung and extrapulmonary organs.

The deposition of PM2.5 (fine particulate matter in air with diameter smaller than 2.5 μm) in lungs is harmful to human health. However, real-time observation on the deposition of particles in the acinar area of the lung is still a challenge in experiments. Here, a fluorescent imaging method is developed to visualize the deposition process with a high temporal and spatial resolution. The observations reveal that the deposition pattern is nonuniform, and the maximum deposition rate in the acinar area differs significantly from the prediction of the widely used average deposition model. The method is also used to find single particles in the kidney and liver, though such particles are commonly believed to be too large to enter the extrapulmonary organs.

Assessing the spatiotemporal characteristics of dry deposition flux in forests and wetlands

ABSTRACTForests and wetlands, as two important ecosystems, play a crucial role in reducing the concentration of particulate matters. The main purpose of this study is to reveal the contribution of forest and wetland ecosystems to the reduction of particulate matter. We collected the concentration and meteorological data during the daytime in a forest and a wetland in the Olympic Park in Beijing. The main results are as follows: daily variation in the PM10 and PM2.5 concentration had the similar trend with the lowest value at midday and relatively high values in the morning and at nightfall. In the forest ecosystem, the trend of PM10 concentration at three heights followed the order: 6 m > 10 m > 1.5 m, while that of the PM2.5 followed the order 1.5 m > 10 m > 6 m. In the wetland, PM10 and PM2.5 concentrations at the three heights exhibited the same trend: 10 m > 1.5 m > 6 m. It is a comprehensive impact on concentration which may include vegetation collection rate, meteorological conditions and some kind of human activities. The PM deposition velocity of wetland was higher than that of forest, and showed the highest values in winter both in PM2.5 and PM10. The PM deposition flux in wetland was lower than forest only in autumn, and the value of deposition flux was higher than forest in other seasons. PM concentrations was positively correlated with relative humidity but negatively correlated with temperature and wind velocity.

In-vitro metabolomics to evaluate toxicity of particulate matter under environmentally realistic conditions

In this pilot study three fractions of particulate matter (PM0.25, PM2.5-0.25, and PM10-2.5) were collected in three environments (classroom, home, and outdoors) in a village located nearby an industrial complex. Time-activity pattern of 20 students attending the classroom was obtained, and the dose of particles reaching the children's lungs under actual environmental conditions (i.e. real dose) was calculated via dosimetry model. The highest PM concentrations were reached in the classroom. Simulations showed that heavy intensity outdoor activities played a major role in PM deposition, especially in the upper part of the respiratory tract. The mass of PM10-2.5 reaching the alveoli was minor, while PM2.5-0.25 and PM0.25 apportion for most of the PM mass retained in the lungs. Consequently, PM2.5-0.25 and PM0.25 were the only fractions used in two subsequent toxicity assays onto alveolar cells (A549). First, a cytotoxicity dose-response assay was performed, and doses corresponding to 5% mortality (LC5) were estimated. Afterwards, two LC-MS metabolomic assays were conducted: one applying LC5, and another applying real dose. A lower estimated LC5 value was obtained for PM0.25 than PM2.5-0.25 (8.08 and 73.7 ng/mL respectively). The number of altered features after LC5 exposure was similar for both fractions (39 and 38 for PM0.25 and PM2.5-0.25 respectively), while after real dose exposure these numbers differed (10 and 5 for PM0.25 and PM2.5-0.25 respectively). The most metabolic changes were related to membrane and lung surfactant lipids. This study highlights the capacity of PM to alter metabolic profile of lung cells at conventional environmental levels.

Effect of Surface Cavity Shape on PM Deposition and Pressure Drop in DPF Porous Material

Effect of Surface Cavity Shape on PM Deposition and Pressure Drop in DPF Porous Material

Effects of bypass flows through Inlet/Inlet walls on PM deposition in hexagonal channel diesel particulate filters

Effects of bypass flows through Inlet/Inlet walls on PM deposition in hexagonal channel diesel particulate filters

212Pb as tracer for PM deposition on urban vegetation

212Pb concentration in outdoor air is closely correlated with fine suspended particulate matter in the atmosphere. Thanks to this association, this isotope can be used to trace the sinking processes of particulate matter due to the vegetation, also providing accurate estimations of the deposition velocity on foliar surfaces. This approach is particularly effective in areas with high thoron fluxes and, consequently, high 212Pb fluxes from soil.The contribution of vegetation to the improvement of air quality (AQImp) in the municipality area (MA) of Rome (Latium, Italy), almost entirely located on Th-enriched volcanic soils, was estimated by studying 212Pb deposition velocity on the grasses (0.9–2.5mm·s−1) and on the most common tree classes, namely conifers (1.5–15mm·s−1), evergreen (1–4mm·s−1) and deciduous (0.2–1.5mm·s−1).212Pb activity in outdoor air was determined by gamma spectrometry after air pumping with accumulation on cellulose filters and after collection on artificial electrostatically charged surfaces (ECS). The high 212Pb activity values obtained from this analysis (0.90±0.6Bqm−3 and 0.58±0.15Bqm−3, respectively near and far from the soil) are consistent both with the average regional thoron flux from volcanic soils (2.9·104Bqm−2·h−1) and with the thoron flux measured in the volcanic soils of the study area. Thoron and 212Pb fluxes were also measured both in laboratory and in the field under different soil moisture conditions. The total AQImp for the period from September 2014 to September 2015, calculated after the classification of the MA of Rome into six classes of vegetation, provided a value of 0.20 corresponding to 2.3 Tons per day of removed PM10. The role of grasslands in the PM10 removal, the contribution of the vegetation to the improvement of AQImp and the possibility of improving the sinking efficiency of green areas by increasing conifer trees coverage were also highlighted.