“…The breathing human model with real respiratory tract structure was obtained through CT scanning, which could simulate oral and nasal respiration, the detail of generation process can refer to ( Xu et al, 2020a ). The respiratory tract model included mouth, oral cavity, nasal cavity, oropharynx, pharynx, larynx, trachea and bronchi (G1-5), from top to the bottom, as shown in Fig.…”
Section: Methodsmentioning
confidence: 99%
“…The trajectory of each droplet or aerosol was calculated by solving the droplet movement equation whose theory is Newton's second law: where is particle velocity, is gravity, is drag force, is Saffman lift force and is Brownian diffusion force, is the Cunningham correction factor, respectively. The details of the parameters in this equation can be referred to ( Xu et al, 2020a ).…”
Section: Methodsmentioning
confidence: 99%
“…However, there are few scientific reports about quantitative comparison of indoor COVID-19 exposure dose when the viruses were released from the infected individual's larynx or lungs. To date, some studies focused on the effects of respiratory patterns on the inhalation of viruses or other particulate matter in indoor environments have been done ( Li et al, 2013 ; Shang and Inthavong, 2019 ; Xu et al, 2020a ). They provided validations of the numerical simulation method by using manikin or respiratory tract model in human inhalation exposure, and suggested that it was necessary for the comprehensive analysis of the particle inhalation within the realistic scenarios.…”
COVID-19 virus can replicate in the infected individual's larynx independently, which is different from other viruses that replicate in lungs only, e.g. SARS. It might contribute to the fast spread of COVID-19. However, there are few scientific reports about quantitative comparison of COVID-19 exposure dose (inhalation dose and adhesion dose) for the susceptible individual when the viruses were released from the larynx or lungs. In this paper, a typical numerical model was built based on a breathing human model with real respiratory tract. By using a computational fluid dynamics (CFD) method, two kinds of virus released sites in the infected individual's respiratory tract (larynx, lungs), seven kinds of particle sizes between 1 and 50 μm, three kinds of expiratory flow rates: calm (10 L/min), moderate (30 L/min) and intense (90 L/min) were used to compare the particle deposition proportion and escape proportion. The inhalation dose and the adhesion dose of the susceptible individual were quantified. The results showed that COVID-19 virus-containing droplets and aerosols might be released into the environment at higher proportions (39.1%–44.2%) than viruses that replicate in lungs only (15.3%–37.1%). The exposure doses (inhalation dose and adhesion dose) of the susceptible individual in different situations were discussed. The susceptible individual suffered a higher exposure dose when the viruses were released from the larynx rather than lungs (the difference for 1 μm particles was 1.2–2.2 times). This study provides a possible explanation for the higher transmission risk of COVID-19 virus compared to other viruses and some control advice of COVID-19 in typical indoor environments were also discussed.
“…The breathing human model with real respiratory tract structure was obtained through CT scanning, which could simulate oral and nasal respiration, the detail of generation process can refer to ( Xu et al, 2020a ). The respiratory tract model included mouth, oral cavity, nasal cavity, oropharynx, pharynx, larynx, trachea and bronchi (G1-5), from top to the bottom, as shown in Fig.…”
Section: Methodsmentioning
confidence: 99%
“…The trajectory of each droplet or aerosol was calculated by solving the droplet movement equation whose theory is Newton's second law: where is particle velocity, is gravity, is drag force, is Saffman lift force and is Brownian diffusion force, is the Cunningham correction factor, respectively. The details of the parameters in this equation can be referred to ( Xu et al, 2020a ).…”
Section: Methodsmentioning
confidence: 99%
“…However, there are few scientific reports about quantitative comparison of indoor COVID-19 exposure dose when the viruses were released from the infected individual's larynx or lungs. To date, some studies focused on the effects of respiratory patterns on the inhalation of viruses or other particulate matter in indoor environments have been done ( Li et al, 2013 ; Shang and Inthavong, 2019 ; Xu et al, 2020a ). They provided validations of the numerical simulation method by using manikin or respiratory tract model in human inhalation exposure, and suggested that it was necessary for the comprehensive analysis of the particle inhalation within the realistic scenarios.…”
COVID-19 virus can replicate in the infected individual's larynx independently, which is different from other viruses that replicate in lungs only, e.g. SARS. It might contribute to the fast spread of COVID-19. However, there are few scientific reports about quantitative comparison of COVID-19 exposure dose (inhalation dose and adhesion dose) for the susceptible individual when the viruses were released from the larynx or lungs. In this paper, a typical numerical model was built based on a breathing human model with real respiratory tract. By using a computational fluid dynamics (CFD) method, two kinds of virus released sites in the infected individual's respiratory tract (larynx, lungs), seven kinds of particle sizes between 1 and 50 μm, three kinds of expiratory flow rates: calm (10 L/min), moderate (30 L/min) and intense (90 L/min) were used to compare the particle deposition proportion and escape proportion. The inhalation dose and the adhesion dose of the susceptible individual were quantified. The results showed that COVID-19 virus-containing droplets and aerosols might be released into the environment at higher proportions (39.1%–44.2%) than viruses that replicate in lungs only (15.3%–37.1%). The exposure doses (inhalation dose and adhesion dose) of the susceptible individual in different situations were discussed. The susceptible individual suffered a higher exposure dose when the viruses were released from the larynx rather than lungs (the difference for 1 μm particles was 1.2–2.2 times). This study provides a possible explanation for the higher transmission risk of COVID-19 virus compared to other viruses and some control advice of COVID-19 in typical indoor environments were also discussed.
“…A more anthropomorphic geometry can provide more accurate results. 38 Xu et al 39 employed a scanned human upper respiratory tract to construct an embedded model consisting of the nasal cavity, oral cavity, oropharynx, larynx, trachea and bronchi, which was used to study the effects of the respiratory patterns of nasal and oral inhalation and different exposure conditions on the deposition of particles in the human respiratory tract. The human body model and fifth-generation respiratory tract model are shown in Figure 2.…”
Section: Simulation Methodsmentioning
confidence: 99%
“…Therefore, CFD has advantages for analyzing the effect of the human thermal plume on the exposure to particulate matter, although further advancements are required.Figure 2.Human body and respiratory airway model. 39 …”
This paper reviews studies on the human thermal plume and its influence on the inhalation exposure to particulate matter in the breathing zone under different conditions. The human thermal plume transports particle pollutants from the floor to the breathing zone, increasing the inhaled particulate matter concentration. The concentration can be four times higher than that in the ambient environment. Studies have reported that the human thermal plume may prevent particulate matter from entering the breathing zone under specific conditions. Indoor airflow patterns significantly affect the dispersion of pollutants, especially in rooms equipped with displacement ventilation at low airflow velocities. It has been shown that the particle concentration is two times lower in the breathing zone of a rotating manikin than a static manikin. Understanding the characteristics and influencing factors of the human thermal plume is crucial to formulate measures to mitigate the inhalation exposure to particulate matter, achieve independent and personalized control of the human microenvironment, and create a healthy, intelligent and energy-saving indoor environment.
Heavy metal pollution is one of the negative impacts deriving from municipal solid waste landfills. Due to the multiple pollution transport pathways (including leachate, runoff, and waste gas) and complex and co-existing potential pollution sources (such as agricultural activities) around landfills, a combination of different pollution assessment methods and source identification tools are required to address pollution distribution and potential risks. In this study, the distribution of eight heavy metals (chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), zinc (Zn), arsenic (As), cadmium (Cd), and mercury (Hg)) around a landfill were analyzed using 60 topsoil samples. There are no environmental pollution and human carcinogenic risk posed by the heavy metals for the time being. However, high concentration of Cr in soil would cause non-carcinogenic risk for adults in the study area. Besides, the geoaccumulation indices of Cr, Cu, Ni, Zn, As, and Hg confirmed anthropogenic accumulation of these heavy metals in soils. Additionally, the potential ecological risk index indicated that Hg posed considerable risk to the eco-environment around the landfill. Sources of the heavy metals in the study area were attributed to natural sources (22.1%), agricultural activities (27.6%), and the landfill (50.3%). As the greatest contributor, the landfill affected heavy metal distribution in nearby surface soils mainly via surface runoff and waste gas. The continuous accumulation of heavy metals and non-carcinogenic risk for adults suggests the necessity for continuous monitoring of heavy metal content and migration around the landfill. This study provides a reference for local authorities in the study area.
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