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Andrea R Ferro - One of the best experts on this subject based on the ideXlab platform.
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a comparative study of walking induced dust Resuspension using a consistent test mechanism
Indoor Air, 2014Co-Authors: Yilin Tian, Jing Qian, Kyung Sul, Sumona Mondal, Andrea R FerroAbstract:UNLABELLED Human walking influences indoor air quality mainly by resuspending dust particles settled on the floor. This study characterized walking-induced particle Resuspension as a function of flooring type, relative humidity (RH), surface dust loading, and particle size using a consistent Resuspension mechanism. Five types of flooring, including hardwood, vinyl, high-density cut pile carpet, low-density cut pile carpet, and high-density loop carpet, were tested with two levels of RH (40% and 70%) and surface dust loading (2 and 8 g/m(2) ), respectively. Resuspension fraction ra (fraction of surface dust resuspended per step) for house dust was found to be varied from 10(-7) to 10(-4) (particle size: 0.4-10 µm). Results showed that for particles at 0.4-3.0 µm, the difference in Resuspension fraction between carpets and hard floorings was not significant. For particles at 3.0-10.0 µm, carpets exhibited higher Resuspension fractions compared with hard floorings. Increased RH level enhanced Resuspension on high-density cut pile carpet, whereas the opposite effect was observed on hard floorings. Higher surface dust loading was associated with lower Resuspension fractions on carpets, while on hard floorings the effect of surface dust loading varied with different RH levels. PRACTICAL IMPLICATIONS The results from this study validate the recommendation that people sensitive to allergens could select hard floorings to reduce exposure and related adverse health outcomes. The results can also be applied to exposure models to determine the overall impact of exposure to Resuspension as compared with other particle sources.
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human induced flow field and resultant particle Resuspension and transport during gait cycle
Building and Environment, 2014Co-Authors: Iman Goldasteh, Goodarz Ahmadi, Yilin Tian, Andrea R FerroAbstract:Abstract Particle Resuspension from flooring is believed to be an important source of particulate matter (PM) in the indoor environment. It is hypothesized that the high speed airflow generated between the flooring and the foot during the gait cycle is the main cause of particle Resuspension. The simulation results show that particles are detached from the substrate during the downward motion of the foot. Furthermore, during the upward motion of the foot, additional particles may also be resuspended because of the suction flow generated by lifting the foot. These resuspended particles are then dispersed in the room by the airflow turbulence. In this study a combined experimental and computational studies were performed to shed light on the mechanisms of particle Resuspension from flooring during the gait cycle. A mechanical foot experimental setup which mimics the human walking was developed and used to measure the rate of Resuspension. In addition, to investigate the airflow field during walking, a three dimensional numerical model of a moving shoe during the gait cycle was generated using the ANSYS-FLUENT™ CFD package. A RANS approach with the RNG k-epsilon turbulence model was used for simulating the unsteady airflow field around and under the shoe. To include the shoe motion in the analysis, a user defined function (UDF) was developed and the dynamic mesh technique was used. A Resuspension model was applied for the Resuspension of pre-deposited particles from the flooring. The predicted particle Resuspension were compared with the corresponding experimental results and good agreement was found.
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Walking-induced particle Resuspension in indoor environments
Atmospheric Environment, 2014Co-Authors: Jing Qian, Jordan Peccia, Andrea R FerroAbstract:Resuspension of particles indoors increases the risk of consequent exposure through inhalation and non-dietary ingestion. Studies have been conducted to characterize indoor particle Resuspension but results do not always agree, and there are still many open questions in this field. This paper reviews the recent research of indoor Resuspension and summarizes findings to answer six critical questions: 1) How does the Resuspension sources compared to other indoor sources; 2) How is Resuspension determined and how does the Resuspension measure change as a function of particle size; 3) What are the primary Resuspension mechanisms; 4) What are the factors affecting Resuspension; 5) What are the knowledge gaps and future research directions in this area; and 6) How can what we know about Resuspension guide better exposure mitigation strategies? From synthesized results, we conclude that Resuspension is an important source for indoor particulate matter, compared with other indoor sources. Among all existing quantification terms of Resuspension, Resuspension fraction has the least variation in its estimates by explicitly defining surface loading and walking frequency, and thus is recommended to be adopted in future research over other terms. Resuspension increases with particle size in the range of 0.7–10 μm, although differences exist in Resuspension estimates by orders of magnitude. The primary mechanism of particle Resuspension involves rolling detachment, and the adhesive forces can be greatly reduced by microscopic surface roughness. Particle Resuspension is by nature complicated, affected by various factors and their interactions. There are still many open questions to be answered to achieve an understanding of Resuspension fundamentals. Given the complex and multidisciplinary nature of Resuspension, understanding indoor particle Resuspension behavior requires cross-disciplinary participation from experts in aerosol science, textile science, surface chemistry, electrostatics, and fluid mechanics.
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wind tunnel study and numerical simulation of dust particle Resuspension from indoor surfaces in turbulent flows
Journal of Adhesion Science and Technology, 2013Co-Authors: Iman Goldasteh, Goodarz Ahmadi, Andrea R FerroAbstract:Particle Resuspension from flooring is an important source of air pollution in the indoor environment. In this work, Resuspension of monolayer, polydisperse, irregularly shaped dust particles from various types of floorings was studied via a series of wind tunnel experiments. The range of free-stream velocity needed for Resuspension of dust particles was evaluated as a function of particle size and material of particles and surfaces. In addition, a Monte Carlo simulation for predicting the Resuspension of dust particles was developed. The Resuspension model took into account the effects of particle irregularity, particle surface roughness, and flow characteristics. The dust particle Resuspension from different floorings for several particle sizes was evaluated. The model predictions for Resuspension fractions were compared with the experimental data and good agreement was observed. The study provided information on the role of airflow velocity on irregular dust particle Resuspension from common floorings.
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Resuspension of Dust Particles in a Chamber and Associated Environmental Factors
Aerosol Science and Technology, 2008Co-Authors: Jing Qian, Andrea R FerroAbstract:Experiments investigating particle Resuspension from human activities were conducted in a full-scale experimental chamber. The experiments tested three types of flooring (vinyl tiles, new and old level-loop carpets) and two ventilation configurations (ceiling and side wall supply systems). The floorings were seeded with 0.1–10 μ m test particles. The airborne particle concentration was measured by an array of optical particle counters (OPCs) in the chamber. Resuspension rates were estimated in size ranges of 0.8–1, 1.0–2.0, 2.0–5.0, and 5.0–10 μm ranging from 10−5–10−2 hr−1, with higher Resuspension rates associated with larger particles. Resuspension via walking activity varied from experiment to experiment. “Heavy and fast” walking was associated with higher Resuspension rates than less active walking, most likely due to a combination of increased pace, increased air swirl velocity, and electrostatic field effects established by the walking. The type of floorings also influenced the particle resuspensio...
Jing Qian - One of the best experts on this subject based on the ideXlab platform.
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a comparative study of walking induced dust Resuspension using a consistent test mechanism
Indoor Air, 2014Co-Authors: Yilin Tian, Jing Qian, Kyung Sul, Sumona Mondal, Andrea R FerroAbstract:UNLABELLED Human walking influences indoor air quality mainly by resuspending dust particles settled on the floor. This study characterized walking-induced particle Resuspension as a function of flooring type, relative humidity (RH), surface dust loading, and particle size using a consistent Resuspension mechanism. Five types of flooring, including hardwood, vinyl, high-density cut pile carpet, low-density cut pile carpet, and high-density loop carpet, were tested with two levels of RH (40% and 70%) and surface dust loading (2 and 8 g/m(2) ), respectively. Resuspension fraction ra (fraction of surface dust resuspended per step) for house dust was found to be varied from 10(-7) to 10(-4) (particle size: 0.4-10 µm). Results showed that for particles at 0.4-3.0 µm, the difference in Resuspension fraction between carpets and hard floorings was not significant. For particles at 3.0-10.0 µm, carpets exhibited higher Resuspension fractions compared with hard floorings. Increased RH level enhanced Resuspension on high-density cut pile carpet, whereas the opposite effect was observed on hard floorings. Higher surface dust loading was associated with lower Resuspension fractions on carpets, while on hard floorings the effect of surface dust loading varied with different RH levels. PRACTICAL IMPLICATIONS The results from this study validate the recommendation that people sensitive to allergens could select hard floorings to reduce exposure and related adverse health outcomes. The results can also be applied to exposure models to determine the overall impact of exposure to Resuspension as compared with other particle sources.
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Walking-induced particle Resuspension in indoor environments
Atmospheric Environment, 2014Co-Authors: Jing Qian, Jordan Peccia, Andrea R FerroAbstract:Resuspension of particles indoors increases the risk of consequent exposure through inhalation and non-dietary ingestion. Studies have been conducted to characterize indoor particle Resuspension but results do not always agree, and there are still many open questions in this field. This paper reviews the recent research of indoor Resuspension and summarizes findings to answer six critical questions: 1) How does the Resuspension sources compared to other indoor sources; 2) How is Resuspension determined and how does the Resuspension measure change as a function of particle size; 3) What are the primary Resuspension mechanisms; 4) What are the factors affecting Resuspension; 5) What are the knowledge gaps and future research directions in this area; and 6) How can what we know about Resuspension guide better exposure mitigation strategies? From synthesized results, we conclude that Resuspension is an important source for indoor particulate matter, compared with other indoor sources. Among all existing quantification terms of Resuspension, Resuspension fraction has the least variation in its estimates by explicitly defining surface loading and walking frequency, and thus is recommended to be adopted in future research over other terms. Resuspension increases with particle size in the range of 0.7–10 μm, although differences exist in Resuspension estimates by orders of magnitude. The primary mechanism of particle Resuspension involves rolling detachment, and the adhesive forces can be greatly reduced by microscopic surface roughness. Particle Resuspension is by nature complicated, affected by various factors and their interactions. There are still many open questions to be answered to achieve an understanding of Resuspension fundamentals. Given the complex and multidisciplinary nature of Resuspension, understanding indoor particle Resuspension behavior requires cross-disciplinary participation from experts in aerosol science, textile science, surface chemistry, electrostatics, and fluid mechanics.
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Resuspension of Dust Particles in a Chamber and Associated Environmental Factors
Aerosol Science and Technology, 2008Co-Authors: Jing Qian, Andrea R FerroAbstract:Experiments investigating particle Resuspension from human activities were conducted in a full-scale experimental chamber. The experiments tested three types of flooring (vinyl tiles, new and old level-loop carpets) and two ventilation configurations (ceiling and side wall supply systems). The floorings were seeded with 0.1–10 μ m test particles. The airborne particle concentration was measured by an array of optical particle counters (OPCs) in the chamber. Resuspension rates were estimated in size ranges of 0.8–1, 1.0–2.0, 2.0–5.0, and 5.0–10 μm ranging from 10−5–10−2 hr−1, with higher Resuspension rates associated with larger particles. Resuspension via walking activity varied from experiment to experiment. “Heavy and fast” walking was associated with higher Resuspension rates than less active walking, most likely due to a combination of increased pace, increased air swirl velocity, and electrostatic field effects established by the walking. The type of floorings also influenced the particle resuspensio...
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Estimating the Resuspension rate and residence time of indoor particles
Journal of the Air and Waste Management Association, 2008Co-Authors: Jing Qian, Andrea R Ferro, Kathleen R. FowlerAbstract:Resuspension experiments were performed in a single-family residence. Resuspension by human activity was found to elevate the mass concentration of indoor particulate matter with an aerodynamic diameter less than 10 microm (PM10) an average of 2.5 times as high as the background level. As summarized from 14 experiments, the average estimated PM10 Resuspension rate by a person walking on a carpeted floor was (1.4 +/- 0.6) x 10(-4) hr(-1). The estimated residence time for PM in the indoor air following Resuspension was less than 2 hr for PM10 and less than 3 hr for 2-microm tracer particles. However, experimental results show that the 2-microm tracer particles stayed in the combined indoor air and surface compartments much longer (>>19 days). Using a two-compartment model to simulate a regular deposition and Resuspension cycle by normal human activity (e.g., walking and sitting on furniture), we estimated residence time for 2-microm conservative particulate pollutants to be more than 7 decades without vacuum cleaning, and months if vacuum cleaning was done once per week. This finding supports the observed long residence time of persistent organic pollutants in indoor environments. This study introduces a method to evaluate the particle Resuspension rate from semicontinuous concentration data of particulate matter (PM). It reveals that Resuspension and subsequent exfiltration does not strongly affect the overall residence time of PM pollutants when compared with surface cleaning. However, Resuspension substantially increases PM concentration, and thus increases short-term inhalation exposure to indoor PM pollutants.
Marc Bouvy - One of the best experts on this subject based on the ideXlab platform.
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Wind Induced Resuspension in a Shallow Tropical Lagoon
Estuarine Coastal and Shelf Science, 1993Co-Authors: Robert Arfi, D. Guiral, Marc BouvyAbstract:In shallow environments, particle Resuspension can induce large ecological effects. Under some certain conditions of fetch, wind velocity, bathymetry and bed roughness, Resuspension is generated by wind induced waves. During December 1991, a shallow station (1 m depth) in the north shore of a tropical lagoon (Cote d'Ivoire) was investigated in order to study the impact of wind induced Resuspension on the ecosystem. In this area, Austral Trade winds are dominant almost all year long, and their velocity shows a marked diel pattern. During the survey, three sequences were distinguished: a period of Austral Trade winds (with possible Resuspension), a period of Boreal Trade winds (no wind induced waves at the station) and a period of transitional Trade winds. Only Austral Trade winds with a speed >3 m s-1 allowed particle Resuspension. For chlorophyll, mineral seston and ammonia, significantly higher values were noted during the windy sequences. Conductivity and water colour varied in relation to tides. Granulometric and mineralogical analyses showed that only the 0-3 cm superficial level of the sediment was involved in Resuspension. This process induced several effects: (1) an increase of suspended matter concentration in the water and thus a light attenuation due to a higher turbidity, (2) a distribution in the whole water column of nutrients from the pore water, (3) a modification of the sediment granulometric characteristics and (4) an increase in the food available for planktonic filter feeders since algal cells were periodically resuspended in the whole water column. Wind induced Resuspension occurred in 10% of the Ebrie lagoon. In this area, the daily alternate of Resuspension-sedimentation sequence is then a major factor controlling the productivity of a system which is potentially highly productive (high nutrient load, favourable climatic conditions) yet characterized by high turbidity. These observations can be generalized to comparable systems in the tropical area.
Leena Nurminen - One of the best experts on this subject based on the ideXlab platform.
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the influence of macrophytes on sediment Resuspension and the effect of associated nutrients in a shallow and large lake lake taihu china
PLOS ONE, 2015Co-Authors: Mengyuan Zhu, Guangwei Zhu, Leena Nurminen, Jiangming Deng, Yunlin Zhang, Boqiang Qin, Annemari VentelaAbstract:A yearlong campaign to examine sediment Resuspension was conducted in large, shallow and eutrophic Lake Taihu, China, to investigate the influence of vegetation on sediment Resuspension and its nutrient effects. The study was conducted at 6 sites located in both phytoplankton-dominated zone and macrophyte-dominated zone of the lake, lasting for a total of 13 months, with collections made at two-week intervals. Sediment Resuspension in Taihu, with a two-week high average rate of 1771 g·m-2·d-1 and a yearly average rate of 377 g·m-2·d-1, is much stronger than in many other lakes worldwide, as Taihu is quite shallow and contains a long fetch. The occurrence of macrophytes, however, provided quite strong abatement of sediment Resuspension, which may reduce the sediment Resuspension rate up to 29-fold. The contribution of nitrogen and phosphorus to the water column from sediment Resuspension was estimated as 0.34 mg·L-1 and 0.051 mg·L-1 in the phytoplankton-dominated zone. Sediment Resuspension also largely reduced transparency and then stimulated phytoplankton growth. Therefore, sediment Resuspension may be one of the most important factors delaying the recovery of eutrophic Lake Taihu, and the influence of sediment Resuspension on water quality must also be taken into account by the lake managers when they determine the restoration target.
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Resuspension-mediated temporal variation in phosphorus concentrations and internal loading.
Journal of environmental quality, 2009Co-Authors: Juha Niemistö, Leena Nurminen, Heidi Holmroos, Jukka HorppilaAbstract:Sediment Resuspension is an important factor for nutrient cycling in shallow lakes. Temporal variation in sediment Resuspension and its influence on P concentrations and internal loading were studied in the shallow and eutrophic Kirkkojarvi basin. Gross sedimentation and sediment Resuspension were estimated with sediment traps during three exposure periods in spring, midsummer, and autumn. The effects of Resuspension on the concentrations of suspended solids, total phosphorus (TP), soluble reactive P, and chlorophyll a were followed. The level of sediment Resuspension was greatest in midsummer (July-August 63.9 g dw m(-2) d(-1)), due to strong phytoplankton blooms modifying the surface film of the sediment more prone to Resuspension. The dependence of high total P concentrations (226-385 microg L(-1)) on sediment Resuspension and suspended solids was significant at the time. The concentrations of soluble reactive P were also high in midsummer (52-91 microg L(-1)), but had a negative dependence on suspended solids. This dependence was due to algal assimilation as was proved by a negative effect of chlorophyll a on soluble reactive P. Consequently, we suggest that the increase in the total P concentrations caused by sediment Resuspension in midsummer was possibly intensified by strong algal blooms occurring at the time because strong assimilation resulting in high pH (pH 7.3 in May, 9.3-10.2 in July-August, 7.6 in October) may have increased the desorption of P from the suspended inorganic particles and intensified the P transfer into the phytoplankton biomass in midsummer.
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effects of different macrophyte growth forms on sediment and p Resuspension in a shallow lake
Hydrobiologia, 2005Co-Authors: Jukka Horppila, Leena NurminenAbstract:The effects of floating-leaved, submerged and emergent macrophytes on sediment Resuspension and internal phosphorus loading were studied in the shallow Kirkkojarvi basin by placing sedimentation traps among different plant beds and adjacent open water and by sediment and water samples. All the three life forms considerably reduced sediment Resuspension compared with non-vegetated areas. Both among submerged (Ceratophyllum demersum, Potamogeton obtusifolius, Ranunculus circinatus) and emergent (Typha angustifolia) plants, Resuspension rate was on average 43% of that in the adjacent open water, while within floating-leaved plants (Nuphar lutea) the corresponding value was 87%. The effects of submerged and emergent vegetation increased in the course of the growing season together with increasing plant density. Among floating-leaved vegetation, such seasonal trend in Resuspension effects was not observed. Compared with the non-vegetated area, floating-leaved, submerged and emergent plants reduced internal phosphorus loading on average by 21, 12 and 26 mg m−2 d−1, respectively. The effects of floating-leaved plants on Resuspension-mediated internal phosphosrus loading were thus comparable to the effects of the other two life forms.
Jukka Horppila - One of the best experts on this subject based on the ideXlab platform.
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Sediment Resuspension: rescue or downfall of a thermally stratified eutrophic lake?
Hydrobiologia, 2012Co-Authors: Juha Niemistö, Perttu Tamminen, Päivi Ekholm, Jukka HorppilaAbstract:The aim of this study was to estimate the effect of sediment Resuspension, a common phenomenon in many lakes, on the phosphorus budget of a eutrophicated lake. We used two different approaches, mass balance calculations and spatially comprehensive Resuspension measurements, to determine the level of phosphorus loading from which rehabilitation action is started in a dimictic north temperate lake. The effect of Resuspension was assumed to be significant, since it often is a governing process for cycling of material in lakes. Internal loading was multifold to that of external loading as determined by the budget calculation. Spatially comprehensive sedimentation and Resuspension measurements were necessary, since deep site versus spatially comprehensive measurements had a marked difference in their results. Resuspension of P slightly exceeded the internal loading assessed by budget calculations and thereby proved its significance as a governing in-lake process that influences P cycling strongly. The shallow areas were of importance, since most of the total P load originated from there. The fate of P after Resuspension depends on the retention capacity of resuspended particles in addition to prevailing biological and physico-chemical conditions. Therefore, sediment Resuspension can either strengthen or diminish internal nutrient load and the processes of the shallow zones are of importance.
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Resuspension-mediated temporal variation in phosphorus concentrations and internal loading.
Journal of environmental quality, 2009Co-Authors: Juha Niemistö, Leena Nurminen, Heidi Holmroos, Jukka HorppilaAbstract:Sediment Resuspension is an important factor for nutrient cycling in shallow lakes. Temporal variation in sediment Resuspension and its influence on P concentrations and internal loading were studied in the shallow and eutrophic Kirkkojarvi basin. Gross sedimentation and sediment Resuspension were estimated with sediment traps during three exposure periods in spring, midsummer, and autumn. The effects of Resuspension on the concentrations of suspended solids, total phosphorus (TP), soluble reactive P, and chlorophyll a were followed. The level of sediment Resuspension was greatest in midsummer (July-August 63.9 g dw m(-2) d(-1)), due to strong phytoplankton blooms modifying the surface film of the sediment more prone to Resuspension. The dependence of high total P concentrations (226-385 microg L(-1)) on sediment Resuspension and suspended solids was significant at the time. The concentrations of soluble reactive P were also high in midsummer (52-91 microg L(-1)), but had a negative dependence on suspended solids. This dependence was due to algal assimilation as was proved by a negative effect of chlorophyll a on soluble reactive P. Consequently, we suggest that the increase in the total P concentrations caused by sediment Resuspension in midsummer was possibly intensified by strong algal blooms occurring at the time because strong assimilation resulting in high pH (pH 7.3 in May, 9.3-10.2 in July-August, 7.6 in October) may have increased the desorption of P from the suspended inorganic particles and intensified the P transfer into the phytoplankton biomass in midsummer.
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effects of different macrophyte growth forms on sediment and p Resuspension in a shallow lake
Hydrobiologia, 2005Co-Authors: Jukka Horppila, Leena NurminenAbstract:The effects of floating-leaved, submerged and emergent macrophytes on sediment Resuspension and internal phosphorus loading were studied in the shallow Kirkkojarvi basin by placing sedimentation traps among different plant beds and adjacent open water and by sediment and water samples. All the three life forms considerably reduced sediment Resuspension compared with non-vegetated areas. Both among submerged (Ceratophyllum demersum, Potamogeton obtusifolius, Ranunculus circinatus) and emergent (Typha angustifolia) plants, Resuspension rate was on average 43% of that in the adjacent open water, while within floating-leaved plants (Nuphar lutea) the corresponding value was 87%. The effects of submerged and emergent vegetation increased in the course of the growing season together with increasing plant density. Among floating-leaved vegetation, such seasonal trend in Resuspension effects was not observed. Compared with the non-vegetated area, floating-leaved, submerged and emergent plants reduced internal phosphorus loading on average by 21, 12 and 26 mg m−2 d−1, respectively. The effects of floating-leaved plants on Resuspension-mediated internal phosphosrus loading were thus comparable to the effects of the other two life forms.
