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Gases, Volume 3, Issue 2 (June 2023) – 2 articles

Cover Story (view full-size image): The study envisages detailed and holistic responses of perennial plants belonging to different habitats and commonly employed in roadside plantation in response to predominant air contaminants of three different land-use sites of the Indo-Gangetic Plains of India. The fifteen assessed parameters reflected significant variations depending upon the site, season and plant species. Based on the assessed responses, it was substantiated that the morphology of the foliage contributed more towards the differential responses of the plants to air pollutants than its habitats. As the habitats evolved from evergreen to deciduous with semi-evergreen in between, the plants demonstrated resistance against prevailing air pollution by enhancing their enzymatic antioxidants and resource utilization parameters (leaf area and leaf dry matter content). View this paper
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15 pages, 4781 KiB  
Article
Computational Fluid Dynamics Analysis of a Hollow Fiber Membrane Module for Binary Gas Mixture
by Salman Qadir, Muhammad Ahsan and Arshad Hussain
Gases 2023, 3(2), 77-91; https://doi.org/10.3390/gases3020005 - 22 May 2023
Cited by 1 | Viewed by 1695
Abstract
The membrane gas separation process has gained significant attention using the computational fluid dynamics (CFD) technique. This study considered the CFD method to find gas concentration profiles in a hollow fiber membrane (HFM) module to separate the binary gas mixture. The membrane was [...] Read more.
The membrane gas separation process has gained significant attention using the computational fluid dynamics (CFD) technique. This study considered the CFD method to find gas concentration profiles in a hollow fiber membrane (HFM) module to separate the binary gas mixture. The membrane was considered with a fiber thickness where each component’s mass fluxes could be obtained based on the local partial pressures, solubility, diffusion, and the membrane’s selectivity. COMSOL Multiphysics was used to solve the numerical solution at corresponding operating conditions and results were compared to experimental data. The two different mixtures, CO2/CH4 and N2/O2, were investigated to obtain concentration gradient and mass flux profiles of CO2 and O2 species in an axial direction. This study allows assessing the feed pressure’s impact on the HFM system’s overall performance. These results demonstrate that the increment in feed pressures decreased the membrane system’s separation performance. The impact of hollow fiber length indicates that increasing the active fiber length has a higher effective mass transfer region but dilutes the permeate-side purities of O2 (46% to 28%) and CO2 (93% to 73%). The results show that increasing inlet pressure and a higher concentration gradient resulted in higher flux through the membrane. Full article
(This article belongs to the Special Issue Membrane Processes for Decarbonisation)
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20 pages, 4420 KiB  
Article
Assessment of the Reverberations Caused by Predominant Air Pollutants on Urban Vegetation: A Multi-Site Study in Varanasi Located in Indo-Gangetic Plains
by Harshita Singh, Pallavi Singh, Shashi Bhushan Agrawal and Madhoolika Agrawal
Gases 2023, 3(2), 57-76; https://doi.org/10.3390/gases3020004 - 05 Apr 2023
Cited by 2 | Viewed by 1363
Abstract
Plant responses to air pollution have been extensively studied in urban environments. Nevertheless, detailed and holistic studies assessing their retaliation to air contaminants are still limited. The present study evaluates the effect of criteria pollutants (SO2, NO2, PM10 [...] Read more.
Plant responses to air pollution have been extensively studied in urban environments. Nevertheless, detailed and holistic studies assessing their retaliation to air contaminants are still limited. The present study evaluates the effect of criteria pollutants (SO2, NO2, PM10 and O3) on the overall biochemistry and resource allocation strategy of plants in order to categorize the dominant roadside species (Mangifera indica, Psidium guajava, Ficus religiosa, Azadirachta indica, Dalbergia sissoo, Cascabela thevetia and Bougainvillea spectabilis) of the Indo-Gangetic Plains (IGP), with different morphologies and habits, into species that are tolerant and sensitive to the prevailing air pollutants. This study was performed at three different land-use sites (industrial, commercial and reference) in Varanasi for two seasons (summer and winter). It was inferred that NO2 and PM10 consistently violated the air quality standards at all the sites. The fifteen assessed parameters reflected significant variations depending upon the site, season and plant species whereupon the enzymatic antioxidants (superoxide dismutase and catalase) and resource utilization parameters (leaf area and leaf dry matter content) were remarkably affected. Based on the studied parameters, it was entrenched that deciduous tree species with compound leaves (D. sissoo > A. indica) were identified as the less sensitive, followed by a shrub (C. thevetia > B. spectabilis), while evergreen species with simple leaves were the most sensitive. It was also substantiated that the morphology of the foliage contributed more toward the differential response of the plants to air pollutants than its habit. Full article
(This article belongs to the Special Issue Air Quality: Monitoring and Assessment)
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