Closed-chamber Experiments Research Articles

Toxic metals from atmospheric particulate matter in food species of tomato (Solanum lycopersicum) and strawberry (Fragaria x ananassa) used in urban gardening. A closed chamber study

In this work, two plant foods, strawberry and tomato, were subjected to exposure to metals from synthetic airborne particles in a closed chamber experiment. The synthetic particles were obtained in the laboratory. Within the closed chamber, particles were added and recirculated for 4 days in a turbulent air stream, causing deposition on the different parts of the plants. They were evaluated because of their increasingly frequent cultivation in urban gardens of cities. The main objectives were to determine whether the species accumulate metals significantly, which species accumulate the most, and in which parts of the plant. Finally, an attempt was made to differentiate the accumulation of pollutants by surface deposition on leaves and fruits from the adsorbed metals into the leaf or the fruit by their stomata or cuticles. The concentration of heavy metals was quantified in fruits, leaves and the soil after exposure. Metals were evaluated as a whole and individually, both in dry and fresh weight basis. The decrease of particulate matter and metals in the air inside the chamber was also studied in order to evaluate the use of both food species as air purifier by vertical gardens. The concentration of metals in plants (mg kg−1) and airborne particles (mg m−3) was measured by microwave plasma optical emission spectroscopy (MP-AES). For the sake comparison of total amount of metals in the samples concentrations were normalized. Strawberries was the food species that accumulated the largest amount of metals. In a dry weight basis, tomato leaves and strawberry fruits were the parts of the plants with higher accumulation capacity of particles and metals. The potential toxic elements Cd, Ni and Cr in tomato leaves and in strawberry fruits had a higher presence in the interior of the plant system. In a fresh weight basis, the strawberry fruit had the most accumulation capacity for metals.

SG-APSIC1151: ZeBox: A prophylactic device against airborne infection

Objectives: Public health emergencies caused by airborne infectious agents are a significant concern, re-emphasized by the current COVID-19 pandemic. It is therefore vital to employ a technology that destroys microbes of all phyla and genera. We describe a novel technology called “Zebox” that can extract, trap, and destroy microbes from the air. This technology destroys even microbes that are resistant to known antibiotics. Methods: Airborne microbial load was enumerated using standard microbiological methods in both hospital ICUs and controlled conditions. Significant microbial reductions due to the ZeBox intervention in the ICUs were confirmed by statistical analysis. Results: ZeBox eliminated a broad spectrum of airborne pathogens (ie, viruses, bacteria, and fungi) in laboratory tests and in hospital ICUs, which are characterized by high, stochastic microbial loads. In closed-chamber experiments, ZeBox achieved a >99.999% reduction of airborne microbes. In the hospital ICU, ZeBox achieved a consistent >90% reduction across several months. Some of the airborne pathogens that ZeBox eliminated in the hospital ICU were multidrug resistant. Conclusions: ZeBox is an effective preventive technology against the spread of airborne pathogens and potentially associated infections. ZeBox could be used to reduce healthcare-associated infections in clinics and hospitals, as well as in burns units and immunocompromised patients. Zebox has the potential to be a significant prophylactic device in the global war on antimicrobial resistance.

Numerical Investigation of Turbulent Premixed Combustion in a High Acceleration Field

Abstract To guide ultra-compact combustor (UCC) engineering, simulations were conducted about turbulent premixed combustion in a high acceleration field which is called high-g combustion, along with a detailed investigation on the evolution of turbulent premixed flame in a rotating tube of stoichiometric propane-air. The rotation of the tube was mimicked by modified momentum source term in the unsteady 2D simulations to decouple the centrifugal force and the Coriolis force, the latter of which was usually neglected in previous reports. A good agreement was found between the simulation result and experimental data, along with a discovery of the phenomenon that flame speed was accelerated by the imposed acceleration field. Further study indicated that the flame acceleration phenomenon can be attributed to the flame corrugation induced by the Rayleigh–Taylor instability (RTI). The Coriolis force was found to be non-negligible in high-g combustion since the Coriolis acceleration could be at the same magnitude as the centrifugal acceleration, and the observed flame speed was nearly 20% lower without the Coriolis force. The current study revealed that the high-g combustion in an open chamber due to the absence of pressure wave/flame front interaction could not be fully compatible with predictions derived from closed chamber experiments and that the Coriolis force could not be ignored in the high-g combustion process.

Biochar with near-neutral pH reduces ammonia volatilization and improves plant growth in a soil-plant system: A closed chamber experiment

Ammonia (NH3) volatilization is considered as one of the major mechanisms responsible for the loss of nitrogen (N) from soil-plant systems worldwide. This study investigated the effect of biochar amendment to a calcareous soil (pH 7.8) on NH3 volatilization and plant N uptake. In particular, the effect of biochar's feedstock and application rate on both NH3 volatilization and plant growth were quantified using a specially designed closed chamber system. Two well-characterized biochars prepared from poultry manure (PM-BC) and green waste compost (GW-BC) were applied to the soil (0, 0.5, 1, 1.5 and 2% w/w equivalent to 0, 7.5, 15, 22 and 30 t ha−1) and wheat (Triticum aestivum, variety: Calingiri) was grown for 30 days. Both PM-BC and GW-BC decreased NH3 volatilization to a similar degree (by 47 and 38%, respectively), in the soil-plant system compared to the unamended control. Higher plant biomass production of up to 70% was obtained in the closed chamber systems with the addition of biochar. The increase in plant biomass was due to the reduction in N loss as NH3 gas, thereby increasing the N supply to the plants. Plant N uptake was improved by as much as 58% with biochar addition when additional NPK nutrients were supplied to the soil. This study demonstrates that the application of biochars can mitigate NH3 emission from calcareous agricultural cropping soil and that the retained N is plant-available and can improve wheat biomass yield.

The NADPH Oxidases Nox1 and Nox2 Differentially Regulate Volatile Organic Compounds, Fungistatic Activity, Plant Growth Promotion and Nutrient Assimilation in Trichoderma atroviride.

In eukaryotic systems, membrane-bound NADPH oxidases (Nox) generate reactive oxygen species (ROS) as a part of normal physiological functions. In the soil-borne mycoparasitic and plant facultative symbiont Trichoderma atroviride, Nox1 and the regulator NoxR are involved in differentiation induced by mechanical damage, while the role of Nox2 has not been determined. The knock-out strains Δnox1, ΔnoxR and Δnox2 were compared to the parental strain (WT) in their ability to grow and conidiate under a series of stress conditions (osmotic, oxidative, membrane, and cell-wall stresses). All three genes were differentially involved in the stress-response phenotypes. In addition, several interactive experiments with biotic factors (plant seedlings and other fungi) were performed comparing the mutant phenotypes with the WT, which was used as the reference strain. Δnox1 and ΔnoxR significantly reduced the antagonistic activity of T. atroviride against Rhizoctonia solani and Sclerotinia sclerotiorum in direct confrontation assays, but Δnox2 showed similar activity to the WT. The Δnox1, ΔnoxR, and Δnox2 mutants showed quantitative differences in the emission of several volatile organic compounds (VOCs). The effects of a blend of these volatiles on plant-growth promotion of Arabidopsis thaliana seedlings were determined in closed-chamber experiments. The increase in root and shoot biomass induced by T. atroviride VOCs was significantly lowered by ΔnoxR and Δnox1, but not by Δnox2. In terms of fungistatic activity at a distance, Δnox2 had a significant reduction in this trait against R. solani and S. sclerotiorum, while fungistasis was highly increased by ΔnoxR and Δnox1. Identification and quantification of individual VOCs in the blends emitted by the strains was performed by GC-MS and the patterns of variation observed for individual volatiles, such as 6-Pentyl-2H-pyran-2-one (6PP-1) and (E)-6-Pent-1-enylpyran-2-one (6PP-2) were consistent with their negative effects in plant-growth promotion and positive effects in fungistasis at a distance. Nox1 and NoxR appear to have a ubiquitous regulatory role of in a variety of developmental and interactive processes in T. atroviride either as positive or negative modulators. Nox2 may also have a role in regulating production of VOCs with fungistatic activity.

Changes in CO2 Absorption Efficiency of NaOH Solution Trap with Temperature

Under the projected global warming, release of carbon as CO2 through soil organic matter decomposition is expected to increase. Therefore, accurate measurement of CO2 released from soil is crucial in understanding the soil carbon dynamics under increased temperature conditions. Sodium hydroxide (NaOH) traps are frequently used in laboratory soil incubation studies to measure soil respiration rate, but decreasing CO2 gas solubility with increasing temperature may render the reliability of the method questionable. In this study, the influences of increasing temperature on the CO2 capture capacity of NaOH traps were evaluated under 5~35°C temperature range at 10°C interval. Two closed-chamber experiments were performed where NaOH traps were used to capture CO2 either released from acidified Na2CO3 solution or directly injected into the chamber. The sorption of ambient CO2 within the incubators into NaOH traps was also measured. The amount CO2 captured increased as temperature increased within 2 days of incubation, suggesting that increased diffusion rate of CO2 at higher temperatures led to increases in CO2 captured by the NaOH traps. However, after 2 days, over 95% of CO2 emitted in the emission-absorption experiment was captured regardless of temperature, demonstrating high CO2 absorption efficiency of the NaOH traps. Thus, we conclude that the influence of decreased CO2 solubility by increased temperatures is negligible on the CO2 capture capacity of NaOH traps, supporting the use of NaOH traps in the study of temperature effect on soil respiration is a valid method. Changes in the CO2 absorption amount of NaOH solution trap with temperature measured using CO2 emission-absorption method. Standard error bars are provided and some bars are not depicted due to small error. Different letters on the data bars indicate significant (P<0.05)difference among the treatments (temperature and reaction time).

Calorespirometry reveals that goldfish prioritize aerobic metabolism over metabolic rate depression in all but near-anoxic environments.

Metabolic rate depression (MRD) has long been proposed as the key metabolic strategy of hypoxic survival, but surprisingly, the effects of changes in hypoxic O2 tensions (PwO2 ) on MRD are largely unexplored. We simultaneously measured the O2 consumption rate (ṀO2 ) and metabolic heat of goldfish using calorespirometry to test the hypothesis that MRD is employed at hypoxic PwO2 values and initiated just below Pcrit, the PwO2below which ṀO2 is forced to progressively decline as the fish oxyconforms to decreasing PwO2 Specifically, we used closed-chamber and flow-through calorespirometry together with terminal sampling experiments to examine the effects of PwO2 and time on ṀO2 , metabolic heat and anaerobic metabolism (lactate and ethanol production). The closed-chamber and flow-through experiments yielded slightly different results. Under closed-chamber conditions with a continually decreasing PwO2 , goldfish showed a Pcrit of 3.0±0.3 kPa and metabolic heat production was only depressed at PwO2 between 0 and 0.67 kPa. Under flow-through conditions with PwO2 held at a variety of oxygen tensions for 1 and 4 h, goldfish also initiated MRD between 0 and 0.67 kPa but maintained ṀO2 to 0.67 kPa, indicating that Pcrit is at or below this PwO2 Anaerobic metabolism was strongly activated at PwO2≤1.3 kPa, but only used within the first hour at 1.3 and 0.67 kPa, as anaerobic end-products did not accumulate between 1 and 4 h exposure. Taken together, it appears that goldfish reserve MRD for near-anoxia, supporting routine metabolic rate at sub-PcritPwO2 values with the help of anaerobic glycolysis in the closed-chamber experiments, and aerobically after an initial (<1 h) activation of anaerobic metabolism in the flow-through experiments, even at 0.67 kPa PwO2.

Photocatalytic degradation of soot deposition: Self-cleaning effect on titanium dioxide coated cementitious materials

Diesel soot emissions deteriorate the appearance of architectural building materials by soot fouling. This soot deposition devalue the aesthetic value of the building. A solution to counteract this problem is applying titanium dioxide on building materials. TiO2 can provide air-purifying and self-cleaning properties due to its photocatalytic activity. In literature, photocatalytic soot oxidation is observed on glass or silicon substrates. However, degradation of soot by photocatalysis was not yet investigated on cementitious samples (mortar, concrete) although it is one of the most frequently used building materials.In this study, photocatalytic soot oxidation by means of TiO2 coated cementitious samples is addressed. The soot removal capacity of four types of TiO2 layers, coated on mortar samples, is evaluated by means of two detection methods. The first method is based on colorimetric measurements, while the second method uses digital image processing to calculate the area of soot coverage.The experimental data revealed that cementitious materials coated with commercially available TiO2 exhibited self-cleaning properties as it was found that all coated samples were able to remove soot. The P25 coating gave the best soot degradation performance, while the Eoxolit product showed the slowest soot degradation rate. In addition, gas chromatography measurements in a closed chamber experiment with P25 confirmed that complete mineralisation of about 60% of the soot was obtained within 24h since CO2 was the sole observed oxidation product.Due to its realistic approach, this study proves that photocatalytic soot removal on TiO2 coated cementitious surfaces is possible in practice, which is an important step towards the practical application of self-cleaning building materials.

C-History Method: Rapid Measurement of the Initial Emittable Concentration, Diffusion and Partition Coefficients for Formaldehyde and VOCs in Building Materials

The initial emittable concentration (C(m,0)), the diffusion coefficient (D(m)), and the material/air partition coefficient (K) are the three characteristic parameters influencing emissions of formaldehyde and volatile organic compounds (VOCs) from building materials or furniture. It is necessary to determine these parameters to understand emission characteristics and how to control them. In this paper we develop a new method, the C-history method for a closed chamber, to measure these three parameters. Compared to the available methods of determining the three parameters described in the literature, our approach has the following salient features: (1) the three parameters can be simultaneously obtained; (2) it is time-saving, generally taking less than 3 days for the cases studied (the available methods tend to need 7-28 days); (3) the maximum relative standard deviations of the measured C(m,0), D(m) and K are 8.5%, 7.7%, and 9.8%, respectively, which are acceptable for engineering applications. The new method was validated by using the characteristic parameters determined in the closed chamber experiment to predict the observed emissions in a ventilated full scale chamber experiment, proving that the approach is reliable and convincing. Our new C-history method should prove useful for rapidly determining the parameters required to predict formaldehyde and VOC emissions from building materials as well as for furniture labeling.

CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; flux determination by closed-chamber methods can be seriously biased by inappropriate application of linear regression

Abstract. Closed (non-steady state) chambers are widely used for quantifying carbon dioxide (CO2) fluxes between soils or low-stature canopies and the atmosphere. It is well recognised that covering a soil or vegetation by a closed chamber inherently disturbs the natural CO2 fluxes by altering the concentration gradients between the soil, the vegetation and the overlying air. Thus, the driving factors of CO2 fluxes are not constant during the closed chamber experiment, and no linear increase or decrease of CO2 concentration over time within the chamber headspace can be expected. Nevertheless, linear regression has been applied for calculating CO2 fluxes in many recent, partly influential, studies. This approach has been justified by keeping the closure time short and assuming the concentration change over time to be in the linear range. Here, we test if the application of linear regression is really appropriate for estimating CO2 fluxes using closed chambers over short closure times and if the application of nonlinear regression is necessary. We developed a nonlinear exponential regression model from diffusion and photosynthesis theory. This exponential model was tested with four different datasets of CO2 flux measurements (total number: 1764) conducted at three peatlands sites in Finland and a tundra site in Siberia. Thorough analyses of residuals demonstrated that linear regression was frequently not appropriate for the determination of CO2 fluxes by closed-chamber methods, even if closure times were kept short. The developed exponential model was well suited for nonlinear regression of the concentration over time c(t) evolution in the chamber headspace and estimation of the initial CO2 fluxes at closure time for the majority of experiments. However, a rather large percentage of the exponential regression functions showed curvatures not consistent with the theoretical model which is considered to be caused by violations of the underlying model assumptions. Especially the effects of turbulence and pressure disturbances by the chamber deployment are suspected to have caused unexplainable curvatures. CO2 flux estimates by linear regression can be as low as 40% of the flux estimates of exponential regression for closure times of only two minutes. The degree of underestimation increased with increasing CO2 flux strength and was dependent on soil and vegetation conditions which can disturb not only the quantitative but also the qualitative evaluation of CO2 flux dynamics. The underestimation effect by linear regression was observed to be different for CO2 uptake and release situations which can lead to stronger bias in the daily, seasonal and annual CO2 balances than in the individual fluxes. To avoid serious bias of CO2 flux estimates based on closed chamber experiments, we suggest further tests using published datasets and recommend the use of nonlinear regression models for future closed chamber studies.

Relations between Light Hydrocarbon, Carbon Monoxide, and Carbon Dioxide Concentrations in the Plume from the Combustion of Plant Material in a Furnace

To systematically explain relations between light hydrocarbons, CO, and CO2 concentrations/emissions of biomassburning, we measured concentrations/emissions of carbon gases – CO,CO2, light hydrocarbons (CH4, C2H6,C2H4, C2H2, C3H8, C3H6,n-C4H10, i-C4H10, n-C5H12,i-C5H12), and THC (total hydrocarbon) – in the burning of dead plant material, mainly Imperata grass, byclosed-chamber experiments and by time-series analyses of gas concentrations in combustion plumes in relatively efficient and inefficient combustion situations. Concentrations of hydrocarbons measured were well correlated to [CO] although [C2H2] was exceptionally well correlated to[CO2]. The phase diagrams (relation between [CO]/Δ [CO2] and [hydrocarbon]/Δ [CO2]) obtained by the time-seriesexperiments well illustrated the variation in the overall emission rates of the closed-chamber experiments. The higher rates of decrease in hydrocarbon concentration with increasing carbon number in the efficient case compared with the inefficient case probably reflected the rate of oxidation and the amount of radicals. The overall concentrations (or emissions) of C2H4 and C3H6 were higher thanthose of C2H6 and C3H8, suggesting a linkage to mechanisms in whichthe predominant path of hydrocarbon oxidation is through the degradation of alkyl radicals, which can be immediately converted into or formed from alkenes. For C3 and C4 species, normal-chain species hadhigher emissions than iso-chain species under lower combustion efficiency. This may be attributable to the presence of tertiary C–H bonds in iso-species,which show more reactivity in the abstraction of H than secondary C–H bonds unless the carbon number is large.

Further studies concerning the energy distribution in the ETC closed chamber and the impact on observed propellant burn rate

In this paper, the authors investigate the consequences of the changing chemical equilibrium states that occur during ETC closed chamber experiments and the associated impact on the propellant burn rate calculation. The theoretical results are compared with experimental data to determine the influence on the computed propellant burn rate when a plasma is present.

Photochemical Production of Carbon Monoxide in Snow

Carbon monoxide concentrations were measured over an 8-day period (March 1997) in freshly fallen snow samples collected at Mount Sonnblick (Austria). Diurnal changes were system- atically observed in the snow, with higher CO during daytime, indicating that light-dependent CO production processes are active in surface snow layers. Mean daytime CO concentrations in snow varied significantly from one day to another and were found to be well correlated with the daily mean atmospheric CO concentrations. Thus, the more polluted the air mass during the snow fall, the more CO was produced through photolytical processes. Furthermore closed chamber experiments were made, giving similar observations: rapid increases of CO concentration occurred within the chamber when the snow was exposed to sunlight. In the dark, however, CO concentrations decreased. CO fluxes between the surface of the snowpack and the atmosphere were estimated at 0.6 ppb/day which may be significant in the local CO budget but not on a global scale. Laboratory experiments showed that CO was rapidly formed when melted snow samples were exposed to the light from a solar simulator and that the initial CO formation rate was strongly correlated with the concentrations of Total Organic Carbon in the melted snow samples. This correlation indicates that organic com- pounds present in snow precipitation are the major substrate for the photochemical CO production observed in freshly fallen snow. Recent studies have reported high formaldehyde concentrations in the snowpack and we suggest HCHO photolysis to be partly responsible of CO production in snow.

Growth and yield responses of Pakistan rice ( Oryza sativa L.) cultivars to O 3 and NO 2

Two separate experiments were undertaken to determine Pakistan rice ( Oryza sativa L.) cultivar responses to air pollution, and specifically to test whether O 3 was the pollutant likely to have caused the large effects of filtration on rice yield found in earlier field experiments in Pakistan. In the first experiment (Exp 1), cv. IRRI-6 was exposed to ozone (O 3) at a mean concentration of 43 nl l −1 (8 h day −1) for 133 days until final harvest, covering both the vegetative and reproductive stages of growth. Results showed a significant reduction in total grain weight per plant. In the second experiment (Exp 2), fumigation of two rice cultivars with O 3 at 40−42 nl l −1 (8 h day −1) and nitrogen dioxide (NO 2) at 21–23 nl l −1 (24 h day −1), both singly and in combination, was carried out for 42 days during the vegetative stage of growth to determine if the presence of low concentrations of NO 2 might influence the responses of both cultivars to O 3. Results showed O 3 to be more phytotoxic than NO 2 at the concentrations used. No significant O 3×NO 2 interactions were found at the time of harvest, but O 3 significantly reduced the photosynthetic capacity and biomass of both cultivars. Results of both experiments are compared with those reported for an open-top chamber filtration experiment carried out in Pakistan using the same two rice cultivars. Grain yield of cv. IRRI-6 was decreased in the closed chamber experiment by 57%, compared to a 37% decrease in the open-top chamber experiment; different yield components were affected in the open-top and closed chamber experiments which may be the result of differences in environmental conditions between the two studies. The results suggest that O 3 may have significant effects on rice yield in Pakistan and indicate that Pakistan rice cultivars have a high sensitivity to O 3.

Uptake of 15NH3 by Picea abies in Closed Chamber Experiments

Abstract Above-ground deposition of anthropogenic trace gases like NH3 and NOx is considered as a main factor for nitrogen (N) loading of Picea abies ecosystems. In order to quantify NH3 deposition, tracer experiments with 15N labelled NH3 were carried out in fumigation chambers (GSF München). NH3 uptake is linearly related to the gas concentration in the air, but the relation differs between organs and depends on N-nutrition of the organs. Plants well supplied with N have a lower NH3 uptake per g dry weight then plants deprived of N. Only a small amount of the offered gas deposits to the external plant surfaces. The NH3 uptake rates of spruce indicate that NH3 may be regarded as being just as or even more important as environmental pollutant than NOx with respect to N loading of spruce ecosystems.