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Chemosphere Jan 2021The interfacial tracer test (ITT) conducted via aqueous miscible-displacement column experiments is one of a few methods available to measure air-water interfacial areas...
The interfacial tracer test (ITT) conducted via aqueous miscible-displacement column experiments is one of a few methods available to measure air-water interfacial areas for porous media. The primary objective of this study was to examine the robustness of air-water interfacial area measurements obtained with interfacial tracer tests, and to examine the overall validity of the method. The potential occurrence and impact of surfactant-induced flow was investigated, as was measurement replication. The column and the effluent samples were weighed during the tests to monitor for potential changes in water saturation and flux. Minimal changes in water saturation and flux were observed for experiments wherein steady flow conditions were maintained using a vacuum-chamber system. The air-water interfacial areas measured with the miscible-displacement method completely matched interfacial areas measured with methods that are not influenced by surfactant-induced flow. This successful benchmarking was observed for all three media tested, and over a range of saturations. A mathematical model explicitly accounting for nonlinear and rate-limited adsorption of surfactant at the solid-water and air-water interfaces as well as the influence of changes in surface tension on matric potentials and flow was used to simulate the tracer tests. The independently-predicted simulations provided excellent matches to the measured data, and revealed that the use of the vacuum system minimized the occurrence of surfactant-induced flow and its associated effects. These results in total unequivocally demonstrate that the miscible-displacement ITT method produced accurate and robust measurements of air-water interfacial area under the extant conditions.
Topics: Adsorption; Air; Benchmarking; Models, Theoretical; Physical Phenomena; Porosity; Surface Tension; Surface-Active Agents; Water
PubMed: 33184521
DOI: 10.1016/j.chemosphere.2020.128193 -
Philosophical Transactions of the Royal... Sep 2016High-flying insect migrants have been shown to display sophisticated flight orientations that can, for example, maximize distance travelled by exploiting tailwinds, and... (Review)
Review
High-flying insect migrants have been shown to display sophisticated flight orientations that can, for example, maximize distance travelled by exploiting tailwinds, and reduce drift from seasonally optimal directions. Here, we provide a comprehensive overview of the theoretical and empirical evidence for the mechanisms underlying the selection and maintenance of the observed flight headings, and the detection of wind direction and speed, for insects flying hundreds of metres above the ground. Different mechanisms may be used-visual perception of the apparent ground movement or mechanosensory cues maintained by intrinsic features of the wind-depending on circumstances (e.g. day or night migrations). In addition to putative turbulence-induced velocity, acceleration and temperature cues, we present a new mathematical analysis which shows that 'jerks' (the time-derivative of accelerations) can provide indicators of wind direction at altitude. The adaptive benefits of the different orientation strategies are briefly discussed, and we place these new findings for insects within a wider context by comparisons with the latest research on other flying and swimming organisms.This article is part of the themed issue 'Moving in a moving medium: new perspectives on flight'.
Topics: Air Movements; Animal Migration; Animals; Cues; Flight, Animal; Insecta; Orientation, Spatial; Visual Perception; Wind
PubMed: 27528782
DOI: 10.1098/rstb.2015.0392 -
Annals of Agricultural and... Jun 2018Bioaerosols are particularly sensitive to sterilization processes due to their biological characteristics. Phenomena occurring in the atmosphere have major influence on...
Bioaerosols are particularly sensitive to sterilization processes due to their biological characteristics. Phenomena occurring in the atmosphere have major influence on airborne bacteria and fungi concentration levels. The presented study evaluates the sterilization properties of ambient air temperature and solar radiation on viable bioaerosols concentration levels in outdoor air in Gliwice, Poland. Assigned were the breakpoints indicating limited stimulation properties of the air temperature, which amounted 7.5°C for bacterial aerosol and 16.5 °C for fungal aerosol. Also revealed was the influence of solar radiation properties on decreasing the bioaerosols concentration levels. Both bacterial and fungal viable aerosol were sensitive to this radiation, although the phenomenon was more effective for airborne bacteria.
Topics: Aerosols; Air; Air Microbiology; Bacteria; Cities; Fungi; Poland; Seasons; Sunlight; Temperature
PubMed: 29936815
DOI: 10.26444/aaem/75877 -
PloS One 2015Human occupants are an important source of microbes in indoor environments. In this study, we used DNA sequencing of filter samples to assess the fungal and bacterial...
Human occupants are an important source of microbes in indoor environments. In this study, we used DNA sequencing of filter samples to assess the fungal and bacterial composition of air in an environmental chamber under different levels of occupancy, activity, and exposed or covered carpeting. In this office-like, mechanically ventilated environment, results showed a strong influence of outdoor-derived particles, with the indoor microbial composition tracking that of outdoor air for the 2-hour sampling periods. The number of occupants and their activity played a significant but smaller role influencing the composition of indoor bioaerosols. Human-associated taxa were observed but were not particularly abundant, except in the case of one fungus that appeared to be transported into the chamber on the clothing of a study participant. Overall, this study revealed a smaller signature of human body-associated taxa than had been expected based on recent studies of indoor microbiomes, suggesting that occupants may not exert a strong influence on bioaerosol microbial composition in a space that, like many offices, is well ventilated with air that is moderately filtered and moderately occupied.
Topics: Aerosols; Air; Air Microbiology; Air Pollution, Indoor; Bacteria; Environmental Monitoring; Fungi; Humans; Microbial Consortia
PubMed: 26024222
DOI: 10.1371/journal.pone.0128022 -
The Journal of Physiology Dec 19761. The monitoring of developmental stage and under-water dissection were used to examine the initial aeration of the respiratory system in domestic fowl embryos. 2. A...
1. The monitoring of developmental stage and under-water dissection were used to examine the initial aeration of the respiratory system in domestic fowl embryos. 2. A virtually complete absence of free air within the chorioallantois was found before the beak had begun to make 'beak-clapping' movements, even when the membranes were already draped over its tip. 3. During the 'beak-clapping' stage, but before the membranes were pierced and before respiratory movements had begun, many embryos were found to contain free bubbles of air within the trachea and air sacs. 4. All embryos in which the respiratory system was aerated were found also to have froth in the crop or other parts of the digestive system. 5. Air was found in both the respiratory and digestive systems of all embryos examined after membrane penetration by the beak. 6. When air was injected into the chorioallantois before the stage of initial aeration it was recovered 5 min later from both the respiratory and digestive systems in under-water dissections. 7. It is suggested that lung ventilation takes place in the avian embryo in three distinct stages: the major air-ways become aerated, then respiratory movements begin and lastly the tertiary bronchi are slowly aerated. It is suggested also that movements involved in the imbibing of fluids play a part in aeration before the membranes are pierced.
Topics: Air; Animals; Beak; Chick Embryo; Extraembryonic Membranes; Respiration; Respiratory System; Time Factors
PubMed: 1018275
DOI: 10.1113/jphysiol.1976.sp011640 -
Sensors (Basel, Switzerland) Jun 2023The published 95% uncertainty of the global surface air-temperature anomaly (GSATA) record through 1980 is impossibly less than the 2σ = ±0.25 °C lower limit of...
The published 95% uncertainty of the global surface air-temperature anomaly (GSATA) record through 1980 is impossibly less than the 2σ = ±0.25 °C lower limit of laboratory resolution of 1 °C/division liquid-in-glass (LiG) thermometers. The ~0.7 °C/century Joule-drift of lead- and soft-glass thermometer bulbs renders unreliable the entire historical air-temperature record through the 19th century. A circa 1900 Baudin meteorological spirit thermometer bulb exhibited intense Pb X-ray emission lines (10.55, 12.66, and 14.76 keV). Uncorrected LiG thermometer non-linearity leaves 1σ = ±0.27 °C uncertainty in land-surface air temperatures prior to 1981. The 2σ = ±0.43 °C from LiG resolution and non-linearity obscures most of the 20th century GSATA trend. Systematic sensor-measurement errors are highly pair-wise correlated, possibly across hundreds of km. Non-normal distributions of bucket and engine-intake difference SSTs disconfirm the assumption of random measurement error. Semivariogram analysis of ship SST measurements yields half the error mean, ±½Δε, not the error mean. Transfer-function adjustment following a change of land station air-temperature sensor eliminates measurement independence and forward-propagates the antecedent uncertainty. LiG resolution limits, non-linearity, and sensor field calibrations yield GSATA mean ±2σ RMS uncertainties of, 1900-1945, ±1.7 °C; 1946-1980, ±2.1 °C; 1981-2004, ±2.0 °C; and 2005-2010, ±1.6 °C. Finally, the 20th century (1900-1999) GSATA, 0.74 ± 1.94 °C, does not convey any information about rate or magnitude of temperature change.
Topics: Temperature; Body Temperature; Thermometers; Air; Calibration
PubMed: 37447827
DOI: 10.3390/s23135976 -
Proceedings of the National Academy of... Dec 2011Capturing carbon dioxide from the atmosphere ("air capture") in an industrial process has been proposed as an option for stabilizing global CO(2) concentrations....
Capturing carbon dioxide from the atmosphere ("air capture") in an industrial process has been proposed as an option for stabilizing global CO(2) concentrations. Published analyses suggest these air capture systems may cost a few hundred dollars per tonne of CO(2), making it cost competitive with mainstream CO(2) mitigation options like renewable energy, nuclear power, and carbon dioxide capture and storage from large CO(2) emitting point sources. We investigate the thermodynamic efficiencies of commercial separation systems as well as trace gas removal systems to better understand and constrain the energy requirements and costs of these air capture systems. Our empirical analyses of operating commercial processes suggest that the energetic and financial costs of capturing CO(2) from the air are likely to have been underestimated. Specifically, our analysis of existing gas separation systems suggests that, unless air capture significantly outperforms these systems, it is likely to require more than 400 kJ of work per mole of CO(2), requiring it to be powered by CO(2)-neutral power sources in order to be CO(2) negative. We estimate that total system costs of an air capture system will be on the order of $1,000 per tonne of CO(2), based on experience with as-built large-scale trace gas removal systems.
Topics: Air; Air Pollution; Biomass; Carbon Dioxide; Environmental Restoration and Remediation; Gases; Models, Statistical; Renewable Energy; Thermodynamics
PubMed: 22143760
DOI: 10.1073/pnas.1012253108 -
PloS One 2013To prevent surgical site infection (SSI), the airborne microbial concentration in operating theaters must be reduced. The air quality in operating theaters and nearby...
To prevent surgical site infection (SSI), the airborne microbial concentration in operating theaters must be reduced. The air quality in operating theaters and nearby areas is also important to healthcare workers. Therefore, this study assessed air quality in the post-operative recovery room, locations surrounding the operating theater area, and operating theaters in a medical center. Temperature, relative humidity (RH), and carbon dioxide (CO2), suspended particulate matter (PM), and bacterial concentrations were monitored weekly over one year. Measurement results reveal clear differences in air quality in different operating theater areas. The post-operative recovery room had significantly higher CO2 and bacterial concentrations than other locations. Bacillus spp., Micrococcus spp., and Staphylococcus spp. bacteria often existed in the operating theater area. Furthermore, Acinetobacter spp. was the main pathogen in the post-operative recovery room (18%) and traumatic surgery room (8%). The mixed effect models reveal a strong correlation between number of people in a space and high CO2 concentration after adjusting for sampling locations. In conclusion, air quality in the post-operative recovery room and operating theaters warrants attention, and merits long-term surveillance to protect both surgical patients and healthcare workers.
Topics: Air; Air Microbiology; Air Pollution; Carbon Dioxide; Environmental Monitoring; Hospitals, Urban; Humans; Operating Rooms; Particulate Matter; Quality of Health Care; Recovery Room; Taiwan
PubMed: 23573296
DOI: 10.1371/journal.pone.0061093 -
PloS One 2013Mosquito behavior assays have been used to evaluate the efficacy of vector control interventions to include spatial repellents (SR). Current analytical methods are not...
BACKGROUND
Mosquito behavior assays have been used to evaluate the efficacy of vector control interventions to include spatial repellents (SR). Current analytical methods are not optimized to determine short duration concentrations of SR active ingredients (AI) in air spaces during entomological evaluations. The aim of this study was to expand on our previous research to further validate a novel air sampling method to detect and quantitate airborne concentrations of a SR under laboratory and field conditions.
METHODOLOGY/PRINCIPAL FINDINGS
A thermal desorption (TD) gas chromatography-mass spectrometry (GC-MS) method was used to determine the amount of dichlorodiphenyltrichloroethane (DDT) in samples of air. During laboratory experiments, 1 L volumes of air were collected over 10 min intervals from a three-chamber mosquito behavior assay system. Significantly higher levels of airborne DDT were measured in the chamber containing textiles treated with DDT compared to chambers free of AI. In the field, 57 samples of air were collected from experimental huts with and without DDT for onsite analysis. Airborne DDT was detected in samples collected from treated huts. The mean DDT air concentrations in these two huts over a period of four days with variable ambient temperature were 0.74 µg/m(3) (n = 17; SD = 0.45) and 1.42 µg/m(3) (n = 30; SD = 0.96).
CONCLUSIONS/SIGNIFICANCE
The results from laboratory experiments confirmed that significantly different DDT exposure conditions existed in the three-chamber system establishing a chemical gradient to evaluate mosquito deterrency. The TD GC-MS method addresses a need to measure short-term (<1 h) SR concentrations in small volume (<100 L) samples of air and should be considered for standard evaluation of airborne AI levels in mosquito behavior assay systems. Future studies include the use of TD GC-MS to measure other semi-volatile vector control compounds.
Topics: Air; DDT; Evaluation Studies as Topic; Gas Chromatography-Mass Spectrometry; Insect Repellents; Mosquito Control
PubMed: 24015195
DOI: 10.1371/journal.pone.0071884 -
American Journal of Public Health and... May 1951
Topics: Air; Air Pollution; Humans; Meteorological Concepts; Meteorology
PubMed: 14829668
DOI: No ID Found