Accumulation Of Particulate Matter Research Articles

Particulate Matter Accumulation on Apples and Plums: Roads Do Not Represent the Greatest Threat

Particulate matter (PM) is a mixture of solid and liquid substances of organic and inorganic character suspended in air. Plants are used as biological filters of air. However, PM can be deposited on their edible parts, with a negative effect on people’s health. The aim of this study was to document the PM accumulation on apples and plums harvested from orchards located alongside roads with differing amounts of traffic. Plums accumulated more PM than apples. The deposition of PM on apples increased during fruit development and was highest at harvest. The impact of road type, traffic intensity, and distance from the road on PM accumulation on fruit was small. The least PM was adsorbed by apples harvested from an orchard located close to a road with the highest traffic, while in the case of plums, no effect of the road on PM deposition was recorded. The amount of PM accumulated on fruits depended on the species (fruit morphology, harvest period), activities undertaken in the orchard (early pruning exposes fruits to PM, ecological preparations increase fruit viscosity), and sources of pollution other than the roads located close to the orchard. Washing fruits with water removed half of the accumulated PM.

Relationships Between Leaf Exposure Time to Air Pollution and Metal and Particulate Matter Accumulation for Holm Oak Leaves

Plants play a fundamental role by intercepting air particulate matter (PM) and improving air quality. The link between the accumulation of pollutants and the leaf exposure time to air pollution remains unclear as it depends on different factors. The aim of this study is to test if the metal and PM accumulation in holm oak leaf is linked to exposure time to air pollution. For this study, 1- (1y) and 2-year (2y) old holm oak leaves were sampled in an urban area near Naples. Those leaves were analyzed to measure the amount of particulate matter (PM2.5–10 and PM>10) and the Cr, Cu, Mn, and Ni metal concentrations. The results displayed that leaf Cr, Cu, and Mn accumulation are linked to exposure time, whereas leaf PM deposit was not directly linked to the exposure time. PM deposit on leaves could be influenced by rainfall events or by the saturation of leaves’ surface.

Characteristics of particulate matter and meteorological conditions of a typical air-pollution episode in Shenyang, northeastern China, in winter 2017

Northeastern China (NEC) has experienced serious environmental problems by energy consumption and domestic emission. This paper reviews an extreme haze event occurred in Shenyang, NEC, on 5–9 January 2017. The meteorological data, extinction coefficients from ground-based Lidar and aerosol optical products from Moderate Resolution Imaging Spectroradiometer (MODIS) were used to study this pollution evolution. The deterioration of visibility lasted for 57 h with a minimum value reached to 0.2 km. The SO2 decreased slightly to approximately 150 μg/m3 while the NO2 mass concentration increased to approximately 100 μg/m3. The northeastern wind (1–2 m/s) and higher relative humidity (RH) (90%) as well as increased pressure (1020 hPa) were conducive to particulate matter (PM) accumulation and degraded visibility. An inversion layer began to appear at 0.2 km and developed upward to 2.0 km with the development of heavy pollution, and the RH in the ground and upper air both increased significantly to 80%–90% to conducive larger aerosol extinction. The aerosol extinction coefficient increased to 1.7–1.8 km−1 during the serious pollution, and the average aerosol optical depth (AOD) increased to 1.5 with a larger Ångström exponent (AE) increasing to 1.5 on 7 January. Five main clusters of air trajectories indicated that pollutants from the northwest, southwest, and local emissions affected Shenyang. These findings elucidate the coordinated variation in visibility, PM, and meteorology elements in the near and upper surfaces as well as the spatial distribution in aerosols from satellites during the special pollution episode in NEC.

Assessment of the ability of roadside vegetation to remove particulate matter from the urban air.

The development of urbanised areas together with the growing transport infrastructure and traffic volume are the main cause of air quality deterioration due to the increasing concentrations of particulate matter. Dust pollution is a threat to human health. It can cause the development of lung, larynx or circulatory system cancer. Due to the ability to accumulate dust particles on the leaf surface, the contribution of trees in the process of phytoremediation of air pollution has started to be appreciated. An analysis of the elemental composition of particulate matter (PM) stored on the leaves surface was also carried out, which showed high average concentration of: C > O > Si > Fe (above 8wt.%). It was also observed single particles with a high concentration of heavy metals: Ti, Mn, Ba, Zn, Cr, Pb, Sn, Ni and REE (rare earth elements). The major origin of PM are vehicular emissions, soil and re-suspended road dust. This paper presents also a comparison of selected tree, shrub and vine species differing in their ability to accumulate particulate matter. It was experimentally determined the average leaf surface of individual plant species and established the amount of particulate matter with aerodynamic diameter between 10 and 100μm, 2.5 and 10μm, and 0.2 and 2.5μm deposited on the leaf surface and in waxes. Some species of vines (Parthenocissus quinquefolia), shrubs (Forsythia x intermediata) and coniferous trees, such as Betula pendula 'Youngii', Quercus rubra, Cratageus monogyna, Acer pseduoplatanus, Tilia cordata Mill. or Platanus orientalis turned out to be the most efficient in the process of phylloremediation.

Territory and related artworks: Stuccoworks from the lombard lakes

The paper presents the analytical campaign carried out on the Baroque stucco decorations by Italian artists known as Artists of the Lakes. Forty samples (from moldings, background, sculpture bas- and high- reliefs) from the churches of S. Lorenzo in Laino, S. Maria dei Ghirli in Campione d’Italia and S. Maria Assunta in Puria (Como, Italy) were analysed by chemical and mineralogical techniques and the data were discussed with a multi-disciplinary approach with art historians, in order to enlighten and compare the artistic techniques. Binders, aggregates, pigments and organic fractions were determined using optical microscopy, scanning electron microscopy with EDS microprobe, X-ray powder diffraction, Raman and Fourier transform infrared spectroscopy, gas chromatography-mass spectrometry. The substrate is constituted by a mixture of magnesian lime, silicatic and/or carbonatic aggregate. Layers sequence varies from the simple pattern of S. Maria dei Ghirli, (1 or 2 layers), to the complexity of S. Lorenzo where up to 9 layers above the substrate were observed. Pigment particles were identified as ochres and as green earth in a single case. Three different gilding techniques are described, as the gold leaf is applied over a chrome yellow ground ( a missione ), over a layer composed by ochre and lead white or over a brass leaf. In some cases organic materials were recognized: oil in gilding preparations and egg mixed with ochre pigments. A carbon black based pigment was identified by Raman spectroscopy in some decorative motifs. The sequence and composition of the finishing layers, the accumulation of particulate matter and the use of gypsum on purpose depending on the decorations typology, enlightened the artist skills, showing how different needs and timing influenced the commissions in the buildings.

Leaf traits of Quercus ilex L. affect particulate matter accumulation

In urban areas, particulate matter (PM) is the most abundant airborne pollutant. Plants have been reported to filter PM, as leaves may intercept and adsorb it. The aims of the research were: i) to evaluate if leaves of Quercus ilex L., an ornamental species proven to be a good monitor of air quality, of different ages (1 and 2 years old) differed for the main leaf traits; ii) to assess the efficiency of Q. ilex L. leaves of different ages to intercept particulate matter of two sizes (PM>10 and PM10); iii) to highlight the leaf traits that enhanced the accumulation of PM>10 and PM10 on leaf surface. The research was performed at four municipalities on the outskirts of Naples (Southern Italy). In April 2018, Q. ilex L. leaves of one and two years old were collected and then described for length, width, area, thickness, circularity, dry matter content and petiole length. The tested hypotheses were: older leaves, that should have high values of the investigated leaf traits, intercept and accumulate greater amounts of PM; leaves with greater circularity, width and length, and with lower dry matter content are expected to accumulate more PM. The findings highlighted that Q. ilex leaves of different ages did not statistically differ neither for the investigated leaf traits nor for the amounts of accumulated PM>10 and PM10; the greater amount of PM was observed in Q. ilex leaves with higher circularity and lower dry matter content; smaller width leaves seem to favour the accumulation of PM>10 and those with smaller length the accumulation of PM10.

Stabilization of soil aggregate and organic matter under the application of three organic resources and biochar-based compound fertilizer

Biochar mediation of soil structure and carbon (C) sequestration has been tested, but the underlying mechanisms in this process are poorly understood. We investigated the effects of different organic matter applications on soil aggregation and associated C in Northeast China. Non-disrupted soil samples (0–20 cm in depth) were collected from the field improvement experiment (established in 2009) with four addition treatments: (1) corn straw (CS), (2) pig manure compost (PMC), (3) biochar from corncob (BIO), and (4) biochar-based compound fertilizer (BF), of which CS, PMC, and BIO were combined with extra mineral fertilizers including nitrogen (N), phosphorus (P), and potassium (K). Soil aggregate distribution and associated C concentrations were estimated using physical fractionation techniques. The CS and PMC additions increased mean weight diameter (MWD), large macroaggregate fractions (>2 mm), and small macroaggregate fractions (0.25–2 mm). In contrast, BIO and BF significantly increased silt + clay fractions (< 0.053 mm). Compared with CS and PMC, applying BIO and BF had limited benefits for soil aggregation. Nevertheless, BIO promoted fine and coarse particulate organic matter (POM) accumulation significantly, and BF promoted fine POM accumulation significantly (within small macroaggregates). The concentrations of mMPOM (POM occluded in microaggregates within small macroaggregates) in BF and mPOM (POM within microaggregates) in BIO were the highest (P < 0.05). Biochar addition did not significantly improve soil structure compared to corn straw and pig manure compost treatments, but it was beneficial to SOC accumulation. Furthermore, C sequestration in the organic addition treatments was driven by the POM dynamics, and biochar debris was preferentially incorporated into the < 0.25 mm fractions.

Vehicular emissions effect on the physiology and health status of five tree species in a Bogotá, Colombia urban forest

ABSTRACT. Introduction: Thanks to filtration by foliage, urban trees have a crucial role in air depuration. However, the exposure to pollutants could reduce their health and physiological performance, mainly because of low access to light and clogging of stomata by particulate matter. Objective: The accumulation of particulate matter on leaves (PMAL) and physiological traits of five urban tree species (Croton bogotanus Cuatrec., Eugenia myrtifolia Sims., Ficus soatensis Dugand, Schinus mole L., and Sambucus nigra L.) were quantified in sixty points in Bogotá, with the aims to (1) build a model explaining the PMAL based on traffic variables, (2) establishing the effect of vehicle pollution on physiological and phytosanitary variables, and (3) to evaluate the susceptibility of seedlings and trees to vehicle pollution. Methods: The physiological parameters: photochemical efficiency, stomatal conductance, chlorophyll content, leaf area, and specific leaf mass were measured and correlated with phytosanitary condition, PMAL and traffic variables: number of lanes, vehicular flow and tree-to-avenue distance. Additionally, tree physiological responses were measured in control, residential streets (RS), low traffic avenues (LTA), and high traffic avenues (HTA), and these last were compared with physiology of seedlings planted by three months in HTA. Results: PMAL was strongly associated with physiological responses. Ficus soatensis and C. bogotanus were the species with the maximum and the minimum PMAL. The exposure to traffic increased the photochemical efficiency and specific leaf mass, which could be related to the enrichment of nitrogen and atmospheric CO2. The stomatal conductance followed a bell pattern of low gas exchange in control sites, high values in RS and LTA, and decreasing again in HTA, which suggests an optimization in CO2 fixation at intermediate levels of pollution and susceptibility to stomatal clogging by extreme vehicle emissions. The chlorophyll a/b ratio, leaf area, and specific leaf mass were significantly related to the severity of leaf symptoms, and S. molle was the species with the healthiest leaves in HTA. Seedlings were more susceptible to pollution than trees, and fruits size and seedlings growth were affected by vehicular pollution. Conclusions: Ficus soatensis optimizes particle filtration and C. bogotanus is ideal for planting in HTA, although only as saplings. By contrast, the fast-growing E. myrtifolia and S. nigra seedlings should not be planted in HTA because of susceptibility of pigment contents, leaf area, and stomatal conductance to pollutants. Finally, because of its persistent high stomatal conductance and its low leaf symptoms, S. molle is the species with the best adaptation to vehicle pollution. A complete analysis of interactions among traffic, physiology, and health will help to improve the urban forestry planning.

Aerosol–photolysis interaction reduces particulate matter during wintertime haze events

Aerosol-radiation interaction (ARI) plays a significant role in the accumulation of fine particulate matter (PM2.5) by stabilizing the planetary boundary layer and thus deteriorating air quality during haze events. However, modification of photolysis by aerosol scattering or absorbing solar radiation (aerosol-photolysis interaction or API) alters the atmospheric oxidizing capacity, decreases the rate of secondary aerosol formation, and ultimately alleviates the ARI effect on PM2.5 pollution. Therefore, the synergetic effect of both ARI and API can either aggravate or even mitigate PM2.5 pollution. To test the effect, a fully coupled Weather Research and Forecasting (WRF)-Chem model has been used to simulate a heavy haze episode in North China Plain. Our results show that ARI contributes to a 7.8% increase in near-surface PM2.5 However, API suppresses secondary aerosol formation, and the combination of ARI and API results in only 4.8% net increase of PM2.5 Additionally, API increases the solar radiation reaching the surface and perturbs aerosol nucleation and activation to form cloud condensation nuclei, influencing aerosol-cloud interaction. The results suggest that API reduces PM2.5 pollution during haze events, but adds uncertainties in climate prediction.

The role of upwelling intermittence in the development of hypoxia and nitrogen loss over the Oregon shelf

Abstract Coastal upwelling regions represent less than 2% of the marine biosphere's volume. Nonetheless, local biogeochemical processes have a considerable impact on the structure and functioning of the global oceans. In this study we characterize the evolution of biogeochemical properties during the upwelling seasons of 2009 and 2010 in the coastal ecosystem off central Oregon (west coast of USA). Both years displayed similar cumulative upwelling favorable winds and total input of preformed nutrients into the midshelf despite of their marked differences in the timing of the onset of the upwelling season, its duration and the number of upwelling relaxation events. However, these differences in upwelling forcing induced inter-annual variability in oxygen and nitrogen deficiencies, particulate matter accumulation and nutrient regeneration. Our results suggest that the summer evolution of nitrogen loss and oxygen depletion over the shelf does not follow a simple relationship with the cumulative upwelling index. We hypothesize that other factors, such as the intensity and persistence of the upwelling, which affect the residence time of water masses over the continental shelf, play a key role in the cumulative effect of biological processes leading to hypoxia in these coastal environments.

Effects of reduced organic matter loading through membrane filtration on the microbial community dynamics in recirculating aquaculture systems (RAS) with Atlantic salmon parr (Salmo salar)

A key challenge in recirculating aquaculture systems (RAS) is the accumulation of particulate organic matter, especially the fine and colloidal fraction due to low removal efficiency of today's technology. The supply of organic matter is typically the limiting resource determining the carrying capacity (CC) of heterotrophic bacteria in the system. An appropriate and stable CC is proposed as a strategy for an optimal microbial environment in RAS with less blooms of opportunistic bacteria and more stable community dynamics. In this study, we investigated the effects of including a membrane for ultrafiltration in the RAS water treatment loop (treating 10–15% of the total water flow) to reduce the amount of fine and colloidal organic matter. Atlantic salmon parr (Salmo salar) were reared in two pilot-scale RAS (mRAS: membrane, cRAS: conventional). To evaluate the bacterial dynamics with and without membrane filtration at different organic loadings, the water exchange rates of the systems were manipulated equally to create periods with high and low loading of organic matter. The results showed that in the mRAS water, the level of organic matter was more stable throughout the experiment for the changing organic matter loadings. As a consequence, water in mRAS had higher microbial diversity, lower and shorter bacterial blooms and generally lower bacterial densities than in cRAS. All variables indicate a better microbial environment in the water of the system with membrane filtration. Also, the physicochemical water quality was better in mRAS in terms of lower turbidity and particulate organic matter (POC), and slightly lower concentrations of total ammonia nitrogen (TAN). The composition of the microbial communities was significantly different between the two systems, and temporal variations in the community dynamics were observed in both systems during the periods with different organic loadings. At high organic loading, the genus Mycobacterium had high relative abundance in the cRAS water (up to 0.25) compared to mRAS (0.01–0.03). The fish in mRAS were significantly bigger (14%) than fish in cRAS at the end of the experiment, however it is hard to conclude whether the better growth in mRAS was due to higher temperatures (caused by membrane operation) or better water quality, as it was probably a combination of both. We can conclude that membrane filtration gave more stable and better physicochemical and microbial water quality, which will reduce the probability for microbially related accidents in RAS.

Urban PM2.5 Induces Cellular Toxicity, Hormone Dysregulation, Oxidative Damage, Inflammation, and Mitochondrial Interference in the HRT8 Trophoblast Cell Line.

Objective: Epidemiological studies have found air pollution to be a driver of adverse pregnancy outcomes, including gestational diabetes, low term birth weight and preeclampsia. It is unknown what biological mechanisms are involved in this process. A first trimester trophoblast cell line (HTR-8/SVneo) was exposed to various concentrations of PM2.5 (PM2.5) in order to elucidate the effect of urban particulate matter (PM) of size <2.5 μm on placental function.Methods: PM2.5 were collected at a site representative of urban traffic and dispersed in cell media by indirect and direct sonication. The HTR-8 cells were grown under standard conditions. Cellular uptake was studied after 24 and 48 h of exposure by transmission electron microscopy (TEM). The secretion of human chorionic gonadotropin (hCG), progesterone, and Interleukin-6 (IL-6) was measured by ELISA. Changes in membrane integrity and H2O2 production were analyzed using the CellToxTM Green Cytotoxicity and ROSGloTM assays. Protease activity was evaluated by MitoToxTM assay. Mitochondrial function was assessed through high resolution respirometry in an Oroboros O2k-FluoRespirometer, and mitochondrial content was quantified by citrate synthase activity.Results: TEM analysis depicted PM2.5 cellular uptake and localization of the PM2.5 to the mitochondria after 24 h. The cells showed aggregated cytoskeleton and generalized necrotic appearance, such as chromatin condensation, organelle swelling and signs of lost membrane integrity. The mitochondria displayed vacuolization and disruption of cristae morphology. At 48 h exposure, a significant drop in hCG secretion and a significant increase in progesterone secretion and IL-6 production occurred. At 48 h exposure, a five-fold increase in protease activity and a significant alteration of H2O2 production was observed. The HTR-8 cells exhibited evidence of increased cytotoxicity with increasing exposure time and dose of PM2.5. No significant difference in mitochondrial respiration or mitochondrial mass could be demonstrated.Conclusion: Following exposure to air pollution, intracellular accumulation of PM may contribute to the placental dysfunction associated with pregnancy outcomes, such as preeclampsia and intrauterine growth restriction, through their direct and indirect effects on trophoblast protein secretion, hormone regulation, inflammatory response, and mitochondrial interference.

Urban wastelands: On the frontline between air pollution sources and residential areas

In urban areas, particulate matter (PM) represents an increasing threat to human health. The ability of plants in parks and along roads in cities to accumulate PM has already been demonstrated, but nothing is known about the effect of wasteland vegetation on air quality, despite a significant proportion of greenery in polluted areas being on wastelands. The aim of this study was to document the accumulation of PM and trace elements (TE) by wasteland species (Robinia pseudoacacia L., Populus × canescens (Aiton) Sm., Acer negundo L., Solidago gigantea (Aiton) and Poaceae) growing on Central European urban wastelands with differing levels of air pollution. On average, the largest amounts of PM accumulated on the foliage of R. pseudoacacia and S. gigantea, and the smallest amounts accumulated on P. × canescens leaves. However, accumulation of PM depended more on the distance from the emission source than on species selection, and was higher on the polluted wasteland where the plants' gas exchange was the lowest. The results also suggest that in order to effectively accumulate PM from the air, it is critical to have the correct configuration of plants, with the wasteland vegetation having a layered structure and layers differing in PM retention, as shown in this study using the examples of R. pseudoacacia (a tall tree with low PM retention) and S. gigantea (below-tree vegetation with high PM retention). P. × canescens accumulated the highest concentrations of Cd and Zn, S. gigantea accumulated the highest concentration of Cu, and Poaceae accumulated the highest concentrations of Cr and Ni. These findings have implications for urban vegetation management in areas where there is no organised greenery, and offer proof that vegetation in wasteland areas should be maintained since it is an excellent tool for reducing concentrations of PM at its place of origin.

Aerosol formation during non-contact "air-puff"tonometry and its significance for prevention of COVID-19

Objective To evaluate the aerosol and concentration (PM2.5, PM10 and aerosol particle number) formation in non-contact air-puff tonometry and provide suggestions for medical workers to take appropriate daily protection during the prevalence of 2019-nCoV. Methods A cross-sectional study was carried out in this study.Thirty healthy subjects were enrolled on February 22, 2020 in Eye Hospital of Wenzhou Medical University.The intraocular pressure (IOP) was measured by non-contact air-puff tonometer in the ophthalmic consulting room and the hall with or without masks.Particulate matter (PM)2.5, PM10 and aerosol particles were recorded by air quality detector.The cumulative effects of IOP measurement, PM2.5, PM10 and aerosol particle number were analyzed, and the aerosol density of subjects with and without masks was compared. Results The PM2.5, PM10 and aerosol particles produced by the non-contact air-puff tonometry and increased with the increase of spray times.The IOP curves of 60 eyes of 30 subjects were measured respectively in two environments of medical consulting room and medical institution hall.It was found that PM2.5, PM10 and particle number fluctuated and increased with the increase of IOP measurement person times, showing cumulative effect, and the accumulation speed of aerosol density in hall was faster than that in consulting room.The density of PM2.5 and PM10 produced without gauze mask were (53.417±2.306) and (85.350± 3.488) μg/m3, which were higher than those of (50.567±0.862) and (80.617±1.463) μg/m3 with gauze mask.The differences were statistically significant (P=0.028, 0.019), and significant difference was found in aerosol density between with and without gauze mask, although more aerosol was produced without gauze mask in comparison to gauze mask (P=0.123). Conclusions Aerosol can be produced by non-contact air-puff tonometer spraying, and it fluctuates with the increase of spraying times, showing a cumulative effect.The aerosol and particulate matter accumulation is higher in the hall with insufficient air circulation, and more aerosol and PM can be produced without gauze mask. Key words: Tonometer, non-contact air-puff; Aerosol; Particulate matter; Infection; Transmission; Corona virus disease-19

Exercise in Thermal Inversions: PM2.5 Air Pollution Effects on Pulmonary Function and Aerobic Performance

Wintertime thermal inversions can lead to the accumulation of small particulate matter (PM2.5). Despite an association between respiratory hospital admissions and elevated PM2.5 levels, many people continue to exercise outdoors during inversions. This study compared pulmonary function and exercise performance during periods of low and high ambient PM2.5 concentrations. Forced vital capacity and forced expiratory volume in 1 s were measured outdoors before and after two 3200 m running time trials: one with low ambient PM2.5 (0.6-14.7 microgram·m-3), and the other during high PM2.5 (19.1-42.5 micrograms·m-3). A 10 cm visual analog scale (VAS) administered postexercise quantified subjective ratings of respiratory discomfort. The PM2.5 differential between trials was ≥18 micrograms·m-3 for 10 healthy runners. Despite feeling more respiratory discomfort (P=0.044) during the bad air trial (VAS: 4.6±1.8 cm) compared with the good air trial (VAS: 2.9±1.8 cm), the 3200 m run time (low PM2.5: 13:54±1:34 min:s; high PM2.5: 14:07±1:44 min:s) was not different (P=0.261) between trials. Postexercise forced vital capacity was not significantly different (P=0.846) between the low (4.86±1.00 L) and high (4.84±0.95 L) PM2.5 conditions. Similarly, the difference in postexercise forced expiratory volume in 1 s was not significant (P=0.750) between trials (4.22±0.89 L vs 4.23±0.85 L). Neither run time nor pulmonary function of healthy adults were adversely affected by an acute bout of exercise in elevated ambient PM2.5, equivalent to yellow or orange on the air quality index.

Particulate matter on foliage of Betula pendula, Quercus robur, and Tilia cordata: deposition and ecophysiology

Trees in urban and industrial areas significantly help to limit the amount of particulate matter (PM) suspended in the air, but PM has a negative impact on their life. The amount of PM gathered on leaves depends on quantity, size, and morphology of leaves and can also be increased by the presence of epicuticular waxes, in which PM can become stuck or immersed. In this study, we determined the ability of PM to accumulate on leaves in relation to the species of tree and PM source. We tested saplings of three common European tree species (Betula pendula, Quercus robur, and Tilia cordata) by experimentally polluting them with PM from different sources (cement, construction, and roadside PM), and then assessing the effects of PM on plant growth and ecophysiology. In all studied species, we have found two types of PM accumulation: a layer on the leaf surface and an in-wax layer. Results showed that the studied species accumulate PM on their leaf blade, reducing the efficiency of its photosynthetic apparatus, which in a broader sense can be considered a reduction in the plants’ normal functioning. Saplings of Q. robur suffered the least, whereas B. pendula (especially photosynthetic rate and conductivity) and T. cordata (especially increase in leader shoot length) exhibited greater negative effects. The foliage of B. pendula collected the most PM, followed by Q. robur, and then T. cordata, regardless of the dust’s source. All tested species showed a tendency for higher wax production when growing under PM pollution stress. We believe that, potentially, B. pendula best enhances the quality of the PM-contaminated environment; however, faster leaf fall, reduced productivity, and worse quality of wood should be considered in urban forest management.

Effects of Foliar Trichomes on the Accumulation of Atmospheric Particulates in Tillandsia Brachycaulos.

Foliar trichomes are specialized structures that have first contact with atmospheric particulate matter (PM), while their effects on PM accumulation are rarely investigated. In this study, epiphytic Tillandsia brachycaulos with foliar trichomes was investigated. Trichomes were removed artificially to investigate PM adsorption and resuspension. The results showed that the maximum PM (13.94±0.20 g•m-2) and natural PM content (10.65±1.10 g•m-2) on T. brachycaulos samples with foliar trichomes was significantly higher than those without foliar trichomes. After PM deposition on the leaf surface, more than 85% of PM was dispersed by wind in plants without trichomes, significantly higher than those with trichomes (30.2%). Therefore, the effects of foliar trichomes on PM were reflected not only on PM adsorption, but on PM resuspension. Foliar trichomes can decrease PM resuspension falling on the leaf surface and promote the accumulation of these particles.

Airborne particulate matter accumulation on common green wall plants

In order to better design greening systems for effective particulate matter (PM) removal, it is important to understand the impact leaf traits have on PM deposition. There are however, inconsistences amongst the leaf traits that have previously been correlated with PM accumulation. The aim of this paper was to identify vegetation characteristics of green wall plants that were associated with the accumulation of particulate matter. To determine patterns associated with different leaf morphologies, eleven common ornamental plant species were sampled across 15 sites, over a 6 month duration. PM deposition was determined gravimetrically and its associated size fractions determined microscopically. Linear mixed models were used to identify statistical patterns relating to differences in PM deposition across plant species. PM deposition and the relative frequencies of particle size fractions were found to be statistically different among species, sites and months. Green wall plants were shown to be effective at PM accumulation as all of the assessed plant species had equivalent PM removal efficiency, with minimal evidence of influential leaf characteristics that could enhance PM removal.

How Much Does Weather Matter? Effects of Rain and Wind on PM Accumulation by Four Species of Australian Native Trees

As interest in improving urban air quality grows, phytoremediation—amelioration through plants—is an increasingly popular method of targeting particulate matter (PM), one of the most harmful pollutants. Decades of research has proven that plants effectively capture PM from air; however, more information is needed on the dynamics of PM accumulation. Our study evaluated the effects of meteorological conditions on the dynamics of PM deposition, wash off and resuspension using four Australian tree species growing under natural conditions near a busy highway. Accumulation of PM on foliage was analyzed over the short term (daily changes) and over a longer time period (weekly changes). The results obtained were correlated with ambient concentrations of PM2.5 and PM10, rain intensity and wind strength. The highest accumulation of PM was recorded for Eucalyptus ovata (100.2 µg cm−2), which also had the thickest wax layer while the lowest was for Brachychiton acerifolius (77.9 µg cm−2). PM accumulation was highly changeable, with up to 35% different PM loads on the foliage from one day to the next. Importantly these dynamics are hidden in weekly measurements. Changes in PM deposition on the leaves was mostly affected by rain and to a lesser extent by wind, but the extent of the effect was species specific. The large PM fraction (10–100 µm) was the first to be removed from leaves, while the smallest PM fraction (0.2–2.5 µm) was retained for longer. Precipitation affects also PM retained in waxes, which until now were believed to be not affected by rain. This work demonstrates important interactions between PM load and weather, as well as adding to the small inventory of Australian native tree PM accumulation data.

Vertically-stacked MEMS PM2.5 sensor for wearable applications

Exposure to fine airborne particulate matter (PM), i.e., PM with an aerodynamic diameter (AD) less than 2.5 μm, is associated with many adverse health effects, including impaired pulmonary function, asthma, cardiovascular diseases, and Alzheimer. Consequently, there is a strong need for the development of small, low-cost wearable PM2.5 sensors that can be used by regular citizens to monitor their PM exposure. This work presents the design, fabrication, and experimental evaluation of a stacked-channel wearable direct-read micro-electro-mechanical system (MEMS) PM2.5 sensor that directly measures the mass concentration of the ambient PM by deposition on a mass-sensing resonator. The sensor employs a vertically stacked air-microfluidic channel geometry and an out-of-plane vertical virtual impactor (VVI), fabricated using a novel delayed deep reactive ion etch (DDRIE) process. As a result, this new device not only allows for a greater level of miniaturization than the previously reported air-microfluidic PM sensors, but also significantly reduces internal fouling due to PM accumulation in its channels. The small footprint of the sensor (27 mm × 14 mm × 2 mm) allows for the integration of the sensor into a wearable or cellular platform. An opto-gravimetric method was used to evaluate the collection efficiency of the VVI, which confirmed its 50% cutpoint at 2.5 μm. The experimental evaluation of the functionality of the sensor confirmed the sensitivity of the new design at 7 Hz/min per μg/m3, which is the highest sensitivity of direct-read mass-based PM2.5 sensor presented to this date. Such sensitivity allows for the limit of detection (LOD) of one μg/m3 within 7 min of integration time at a noise level of 50 Hz.