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European Journal of Protistology Aug 2021Cercozoa and Oomycota contain a huge biodiversity and important pathogens of forest trees and other vegetation. We analyzed air dispersal of these protistan phyla with...
Cercozoa and Oomycota contain a huge biodiversity and important pathogens of forest trees and other vegetation. We analyzed air dispersal of these protistan phyla with an air sampler near-ground (~2 m) and in tree crowns (~25 m) of three tree species (oak, linden and ash) in a temperate floodplain forest in March (before leafing) and May (after leaf unfolding) 2019 with a cultivation-independent high-throughput metabarcoding approach. We found a high diversity of Cercozoa and Oomycota in air samples with 122 and 81 OTUs, respectively. Especially oomycetes showed a significant difference in community composition between both sampling dates. Differences in community composition between air samples in tree canopies and close to the ground were however negligible, and also tree species identity did not affect communities in air samples, indicating that the distribution of protistan propagules through the air was not spatially restricted in the forest ecosystem. OTUs of plant pathogens, whose host species did not occur in the forest, demonstrate dispersal of propagules from outside the forest biome. Overall, our results lead to a better understanding of the stochastic processes of air dispersal of protists and protistan pathogens, a prerequisite to understand the mechanisms of their community assembly in forest ecosystems.
Topics: Air; Biodiversity; Ecosystem; Eukaryota; Trees
PubMed: 34090087
DOI: 10.1016/j.ejop.2021.125805 -
Sensors (Basel, Switzerland) Nov 2022Precise and accurate measurements of ambient HNO3 are crucial for understanding various atmospheric processes, but its ultra-low trace amounts and the high polarity of...
Precise and accurate measurements of ambient HNO3 are crucial for understanding various atmospheric processes, but its ultra-low trace amounts and the high polarity of HNO3 have strongly hindered routine, widespread, direct measurements of HNO3 and restricted field studies to mostly short-term, localized measurement campaigns. Here, we present a custom field-deployable direct absorption laser spectrometer and demonstrate its analytical capabilities for in situ atmospheric HNO3 measurements. Detailed laboratory characterizations with a particular focus on the instrument response under representative conditions for tropospheric measurements, i.e., the humidity, spectral interference, changing HNO3 amount fractions, and air-sampling-related artifacts, revealed the key aspects of our method: (i) a good linear response (R2 > 0.98) between 0 and 25 nmol·mol−1 in both dry and humid conditions with a limit of detection of 95 pmol·mol−1; (ii) a discrepancy of 20% between the spectroscopically derived amount fractions and indirect measurements using liquid trapping and ion chromatography; (iii) a systematic spectral bias due to water vapor. The spectrometer was deployed in a three-week field measurement campaign to continuously monitor the HNO3 amount fraction in ambient air. The measured values varied between 0.1 ppb and 0.8 ppb and correlated well with the daily total nitrates measured using a filter trapping method.
Topics: Air Pollutants; Air; Nitrates; Lasers
PubMed: 36501859
DOI: 10.3390/s22239158 -
PloS One 2015Conventional wisdom among cave divers is that submerged caves in aquifers, such as in Florida or the Yucatan, are unstable due to their ever-growing size from limestone...
Conventional wisdom among cave divers is that submerged caves in aquifers, such as in Florida or the Yucatan, are unstable due to their ever-growing size from limestone dissolution in water. Cave divers occasionally noted partial cave collapses occurring while they were in the cave, attributing this to their unintentional (and frowned upon) physical contact with the cave walls or the aforementioned "natural" instability of the cave. Here, we suggest that these cave collapses do not necessarily result from cave instability or contacts with walls, but rather from divers bubbles rising to the ceiling and reducing the buoyancy acting on isolated ceiling rocks. Using familiar theories for the strength of flat and arched (un-cracked) beams, we first show that the flat ceiling of a submerged limestone cave can have a horizontal expanse of 63 meters. This is much broader than that of most submerged Florida caves (~ 10 m). Similarly, we show that an arched cave roof can have a still larger expanse of 240 meters, again implying that Florida caves are structurally stable. Using familiar bubble dynamics, fluid dynamics of bubble-induced flows, and accustomed diving practices, we show that a group of 1-3 divers submerged below a loosely connected ceiling rock will quickly trigger it to fall causing a "collapse". We then present a set of qualitative laboratory experiments illustrating such a collapse in a circular laboratory cave (i.e., a cave with a circular cross section), with concave and convex ceilings. In these experiments, a metal ball represented the rock (attached to the cave ceiling with a magnet), and the bubbles were produced using a syringe located at the cave floor.
Topics: Air; Calcium Carbonate; Caves; Groundwater; Mechanical Phenomena
PubMed: 25849088
DOI: 10.1371/journal.pone.0122349 -
International Journal of Environmental... Nov 2022Recently released hourly particular matter (PM:PM and PM) and gaseous pollutants (SO, NO, CO, and O) data observed in Qingdao, Hangzhou, and Xiamen from 2015 to 2019...
Recently released hourly particular matter (PM:PM and PM) and gaseous pollutants (SO, NO, CO, and O) data observed in Qingdao, Hangzhou, and Xiamen from 2015 to 2019 were utilized to reveal the current situation of air pollution over eastern coastal China. The PM pollution situation over the three metropolises ameliorated during studied period with the concentrations decreasing about 20-30%. Gas pollutants, excepting SO, generally exhibit no evident reduction tendencies, and a more rigorous control standard on gaseous pollutants is neededEven for the year 2018 with low pollution levels among the study period, these levels (<10% of PM, <6% of PM, and <15% of O) surpass the Grade II of the Chinese Ambient Air Quality Standard (CAAQS) over these metropolises of eastern coast China. No matter in which year, both SO and CO concentrations are always below the Grade-II standards. According to the comparative analysis of PM/PM and PM/CO during episode days and non-episode days, the formation of secondary aerosols associated with stagnant weather systems play an important role in the pollutant accumulation as haze episodes occurred. The stronger seasonal variations and higher magnitude occur in Qingdao and Hangzhou, while weaker seasonal variations and lower magnitudes occur in Xiamen. In Qingdao and Hangzhou, PM, NO, SO, and CO show relatively high levels in the cold wintertime and low levels in summer, whereas O shows a completely opposite pattern. Xiamen exhibits high levels of all air pollutants except O in spring due to its subtropical marine monsoon climate with mild winters. According to the back trajectory hierarchical clustering and concentration weighted trajectory (CWT) analysis, the regional transmission from adjacent cities has a significant impact on the atmospheric pollutant concentrations under the control of the prejudiced winds. Thus, besides local emission reduction, strengthening regional environmental cooperation and implementing joint prevention are effective measures to mitigate air pollution in the eastern coastal areas of China.
Topics: Air Pollutants; Nitrogen Dioxide; Environmental Pollutants; Gases; China; Wind; Particulate Matter
PubMed: 36430050
DOI: 10.3390/ijerph192215332 -
Environmental Science and Pollution... Dec 2016Organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) were studied to determine occurrence, levels and spatial distribution in the marine atmosphere and...
Organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) were studied to determine occurrence, levels and spatial distribution in the marine atmosphere and surface seawater during cruises in the German Bight and the wider North Sea in spring and summer 2009-2010. In general, the concentrations found in air are similar to, or below, the levels at coastal or near-coastal sites in Europe. Hexachlorobenzene and α-hexachlorocyclohexane (α-HCH) were close to phase equilibrium, whereas net atmospheric deposition was observed for γ-HCH. The results suggest that declining trends of HCH in seawater have been continuing for γ-HCH but have somewhat levelled off for α-HCH. Dieldrin displayed a close to phase equilibrium in nearly all the sampling sites, except in the central southwestern part of the North Sea. Here atmospheric deposition dominates the air-sea exchange. This region, close to the English coast, showed remarkably increased surface seawater concentrations. This observation depended neither on riverine input nor on the elevated abundances of dieldrin in the air masses of central England. A net depositional flux of p,p'-DDE into the North Sea was indicated by both its abundance in the marine atmosphere and the changes in metabolite pattern observed in the surface water from the coast towards the open sea. The long-term trends show that the atmospheric concentrations of DDT and its metabolites are not declining. Riverine input is a major source of PCBs in the German Bight and the wider North Sea. Atmospheric deposition of the lower molecular weight PCBs (PCB28 and PCB52) was indicated as a major source for surface seawater pollution.
Topics: Air; Air Pollutants; Atmosphere; England; Environmental Monitoring; Hydrocarbons, Chlorinated; North Sea; Pesticides; Polychlorinated Biphenyls; Seawater
PubMed: 27617333
DOI: 10.1007/s11356-016-7530-3 -
International Journal of Environmental... Aug 2012In order to improve disinfection by-product (DBP) exposure assessment, this study was designed to document both water and air levels of these chemical contaminants in...
In order to improve disinfection by-product (DBP) exposure assessment, this study was designed to document both water and air levels of these chemical contaminants in two indoor swimming pools and to analyze their within-day and day-to-day variations in both of them. Intensive sampling was carried out during two one-week campaigns to measure trihalomethanes (THMs) and chloramines (CAMs) in water and air, and haloacetic acids (HAAs) in water several times daily. Water samples were systematically collected at three locations in each pool and air samples were collected at various heights around the pool and in other rooms (e.g., changing room) in the buildings. In addition, the ability of various models to predict air concentrations from water was tested using this database. No clear trends, but actual variations of contamination levels, appeared for both water and air according to the sampling locations and times. Likewise, the available models resulted in realistic but imprecise estimates of air contamination levels from water. This study supports the recommendation that suitable minimal air and water sampling should be carried out in swimming pools to assess exposure to DBPs.
Topics: Air; Air Pollutants; Carboxylic Acids; Chloramines; Disinfection; Hazardous Substances; Models, Statistical; Swimming Pools; Trihalomethanes; Water
PubMed: 23066383
DOI: 10.3390/ijerph9082562 -
Indoor Air Nov 2017We report measurements of hydroxyl (OH) and hydroperoxy (HO ) radicals made by laser-induced fluorescence spectroscopy in a computer classroom (i) in the absence of...
We report measurements of hydroxyl (OH) and hydroperoxy (HO ) radicals made by laser-induced fluorescence spectroscopy in a computer classroom (i) in the absence of indoor activities (ii) during desk cleaning with a limonene-containing cleaner (iii) during operation of a commercially available "air cleaning" device. In the unmanipulated environment, the one-minute averaged OH concentration remained close to or below the limit of detection (6.5×10 molecule cm ), whilst that of HO was 1.3×10 molecule cm . These concentrations increased to ~4×10 and 4×10 molecule cm , respectively during desk cleaning. During operation of the air cleaning device, OH and HO concentrations reached ~2×10 and ~6×10 molecule cm respectively. The potential of these OH concentrations to initiate chemical processing is explored using a detailed chemical model for indoor air (the INDCM). The model can reproduce the measured OH and HO concentrations to within 50% and often within a few % and demonstrates that the resulting secondary chemistry varies with the cleaning activity. Whilst terpene reaction products dominate the product composition following surface cleaning, those from aromatics and other VOCs are much more important during the use of the air cleaning device.
Topics: Air; Air Pollution, Indoor; Disinfection; Hydroxides; Models, Chemical; Oxygen; Peroxides; Volatile Organic Compounds
PubMed: 28493625
DOI: 10.1111/ina.12394 -
Indoor Air Feb 2013p-dichlorobenzene (PDCB) is a chlorinated volatile organic compound that can be encountered at high concentrations in buildings owing to its use as pest repellent and... (Comparative Study)
Comparative Study
UNLABELLED
p-dichlorobenzene (PDCB) is a chlorinated volatile organic compound that can be encountered at high concentrations in buildings owing to its use as pest repellent and deodorant. This study characterizes PDCB concentrations in four communities in southeast Michigan. The median concentration outside 145 homes was 0.04 μg/m(3), and the median concentration inside 287 homes was 0.36 μg/m(3). The distribution of indoor concentrations was extremely skewed. For example, 30% of the homes exceeded 0.91 μg/m(3), which corresponds to a cancer risk level of 10(-5) based on the California unit risk estimate, and 4% of homes exceeded 91 μg/m(3), equivalent to a 10(-3) risk level. The single highest measurement was 4100 μg/m(3). Estimates of whole-house emission rates were largely consistent with chamber test results in the literature. Indoor concentrations that exceed a few μg/m(3) indicate the use of PDCB products. PDCB concentrations differed among households and the four cities, suggesting the importance of locational, cultural, and behavioral factors in the use patterns of this chemical. The high PDCB levels found suggest the need for policies and actions to lower exposures, for example, sales or use restrictions, improved labeling, and consumer education.
PRACTICAL IMPLICATIONS
Distributions of p-dichlorobenzene concentrations in residences are highly right-skewed, and a subset of houses has very elevated concentrations that are equivalent to an excess cancer risk of 10(-3) or higher based on the California unit risk effect estimate. House-to-house variation is large, reflecting differences in use practices. Stronger policies and educational efforts are needed to eliminate or modify indoor usage practices of this chemical.
Topics: Air; Air Pollutants; Air Pollution, Indoor; Chlorobenzenes; Cities; Naphthalenes; Risk Assessment
PubMed: 22725685
DOI: 10.1111/j.1600-0668.2012.00796.x -
Ultrasonics Sonochemistry Apr 2009To understand the underlying concepts required for the determination of thresholds for free radical generation, effects of gas dissolution in and microbubble addition to...
Threshold curves obtained under various gaseous conditions for free radical generation by burst ultrasound - Effects of dissolved gas, microbubbles and gas transport from the air.
To understand the underlying concepts required for the determination of thresholds for free radical generation, effects of gas dissolution in and microbubble addition to sonicated solutions were investigated. Four solutions with different gaseous conditions, air-saturated and degassed solutions with and without microbubbles of 20 microm in diameter with shells, were studied in the presence of an air-liquid interface. These test solutions were exposed to 1 MHz ultrasound of 0.06 MPa(p-p) at various pulse durations (PDs) from 0.1 to 5 ms and pulse repetition frequencies from 0.1 to 2 kHz. Generation of free radicals was evaluated using the electron spin resonance (ESR) spin trapping method and starch-iodine method. Thresholds of duty ratio (DR) corresponding to temporal average intensity of ultrasound for free radical generation were significantly greater in degassed solutions than in air-saturated solutions. Microbubbles had no significant effects in air-saturated solutions but caused a slight decrease in the threshold in degassed solutions. In all of these results, the DR of a threshold curve against pulse repetition period (PRP) was not constant but linearly decreased with it, suggesting that a balance between bubble growth and shrinkage during the ON and OFF times of burst ultrasound is the primary parameter for the interpretation of thresholds. The effect of an air-liquid interface of the solution was also examined, and it was revealed that gas transport from the air is a predominant factor determining the amount of free radicals.
Topics: Air; Free Radicals; Gases; Microbubbles; Motion; Solubility; Sonication; Ultrasonics
PubMed: 19124266
DOI: 10.1016/j.ultsonch.2008.11.010 -
Scientific Reports Sep 2022The interest around analysis of volatile organic compounds (VOCs) within breath has increased in the last two decades. Uncertainty remains around standardisation of...
The interest around analysis of volatile organic compounds (VOCs) within breath has increased in the last two decades. Uncertainty remains around standardisation of sampling and whether VOCs within room air can influence breath VOC profiles. To assess the abundance of VOCs within room air in common breath sampling locations within a hospital setting and whether this influences the composition of breath. A secondary objective is to investigate diurnal variation in room air VOCs. Room air was collected using a sampling pump and thermal desorption (TD) tubes in the morning and afternoon from five locations. Breath samples were collected in the morning only. TD tubes were analysed using gas chromatography coupled with time-of-flight mass spectrometry (GC-TOF-MS). A total of 113 VOCs were identified from the collected samples. Multivariate analysis demonstrated clear separation between breath and room air. Room air composition changed throughout the day and different locations were characterized by specific VOCs, which were not influencing breath profiles. Breath did not demonstrate separation based on location, suggesting that sampling can be performed across different locations without affecting results.
Topics: Air; Air Pollutants; Body Fluids; Breath Tests; Gas Chromatography-Mass Spectrometry; Volatile Organic Compounds
PubMed: 36151300
DOI: 10.1038/s41598-022-20365-7