Effect Of Relative Air Humidity Research Articles

Lower air humidity reduced both the plant growth and activities of photosystems I and II under prolonged heat stress

The warming is global problem. In natural environments, heat stress is usually accompanied by drought. Under drought conditions, water content decreases in both soil and air; yet,the effect of lower air humidity remains obscure. We supplied maize and barley plants with an unlimited source of water for the root uptake and studied the effect of relative air humidity under heat stress. Young plants were subjected for 48 h to several degrees of heat stress: moderate (37 °C), genuine (42 °C), and nearly lethal (46 °C). The conditions of lower air humidity decreased the photochemical activities of photosystem I and photosystem II. The small effect was revealed in the control (24 °C). Elevating temperature to 37 °C and 42 °C increased the relative activities of both photosystems; the photosystem II was activated more. Probably, this is why the effect of air humidity disappeared at 37 °C; the small inhibiting effect was observed at 42 °C. At 46 °C, lower air humidity substantially magnified the inhibitory effect of heat. As a result, the maximal and relative activities of both photosystems decreased in maize and barley; the photosystem II was inhibited more. Under the conditions of 46 °C at lower air humidity, the plant growth was greatly reduced. Maize plants increased water uptake by roots and survived; barley plants were unable to increase water uptake and died. Therefore, air humidity is an important component of environmental heat stress influencing activities of photosystem I and photosystem II and thereby plant growth and viability under severe stress conditions.

Significance of the humidityregime during the storage of bakery products to ensure their safety

The article made an analytical review of the effect of relative air humidity on the change in the quality of bakery products during storage on the example of the experiments performed. It is shown that the theoretical basis for the proper storage of flour, cereals, and macaroni products is to take into account the critical moisture content, i.e., the moisture level at which free moisture appears in the products. The appearance of free moisture dramatically increases the risk of product spoilage (mold, rancidity, souring). The recommendations are given to ensure the safety of bakery products

Skin Temperature: The Impact of Perfusion, Epidermis Thickness, and Skin Wetness

This work aimed to elucidate the primary factors which affect skin temperature. A simple thermophysical model of the skin, which accounts for radiative, convective, and evaporative heat losses, has been developed to address it. The model is based on the skin’s morphology and consists of passive (nonviable tissue) and active (viable tissue) layers. The bioheat equation was solved for these layers using realistic assumptions. It was found that other than the ambient temperature, blood perfusion and epidermis thickness are the primary factors responsible for the skin temperature variations. The main temperature drop in the skin is attributed to the cooling of the blood in the venous plexus. The temperature drop in the epidermis is on the scale of 0.1 °C for the normal epidermis but can be 1.5–2 °C or higher in calluses. Thus, local skin temperature variations can indicate the epidermis thickness variations, particularly in callus-prone areas. The effects of relative air humidity and skin wetness on skin temperature were also quantified. The presence of free moisture on the skin (e.g., wet wound) significantly increases the heat transfer, resulting in a skin temperature drop, which can be on the scale of several degrees Celsius. The relative air humidity significantly contributes (by slowing heat dissipation) only in the case of evaporative heat loss from wet skin. Therefore, wet skin is undesirable and should be avoided during a thermographic assessment.

Effect of Relative Air Humidity on the Number Concentration of Aerosol Particles in a Sealed Volume

Effect of Relative Air Humidity on the Number Concentration of Aerosol Particles in a Sealed Volume

The effect of relative air humidity on the evaporation timescales of a human sneeze.

The present paper investigates droplet and aerosol emission from the human respiratory function by numerical and experimental methods, which is analyzed at the worst-case scenario, a violent sneeze without a face covering. The research findings develop the understanding of airborne disease transmission relevant to COVID-19, its recent variants, and other airborne pathogens. A human sneeze is studied using a multiphase Computational Fluid Dynamics (CFD) model using detached eddy simulation coupled to the emission of droplets that break up, evaporate, and disperse. The model provides one of the first experimental benchmarks of CFD predictions of a human sneeze event. The experiments optically capture aerosols and droplets and are processed to provide spatiotemporal data to validate the CFD model. Under the context of large random uncertainty, the studies indicate the reasonable correlation of CFD prediction with experimental measurements using velocity profiles and exposure levels, indicating that the model captures the salient details relevant to pathogen dispersion. Second, the CFD model was extended to study the effect of relative humidity with respect to the Wells curve, providing additional insight into the complexities of evaporation and sedimentation characteristics in the context of turbulent and elevated humidity conditions associated with the sneeze. The CFD results indicated correlation with the Wells curve with additional insight into features, leading to non-conservative aspects associated with increased suspension time. These factors are found to be associated with the combination of evaporation and fluid-structure-induced suspension. This effect is studied for various ambient air humidity levels and peaks for lower humidity levels, indicating that the Wells curve may need a buffer in dry climates. Specifically, we find that the increased risk in dry climates may be up to 50% higher than would be predicted using the underlying assumptions in Wells’ model.

Influence of Relative Humidity on the Characteristics of Filter Cake Using Particle Flow Code Simulation

To study the effect of air humidity on particle filtration performance, the Particle Flow Code (PFC) calculation program was used to numerically simulate the formation process of filter cake. The effects of relative air humidity on the deposition morphology, porosity and filtration resistance characteristics of the filter cake were revealed. The results show that relative humidity (RH) is mainly reflected in the density and surface viscosity of the particles. It was found that the higher the relative humidity, the higher the particle moisture content, the greater the density, and the greater the surface viscosity. With an increase in the particle density or with a decrease in the viscosity, the bridging phenomenon of particle deposition became more obvious; the dendritic deposition phenomenon became weaker; and, therefore, the filter cake structure became denser; the porosity decreased; and the total filtration resistance increased. As the humidity changed, the actual density and viscosity of the particles changed simultaneously with different degrees, which caused different variation trends of the filter cake characteristics. Three different types of particles, DM828 (Starch), PVA1788 (Polyvinyl Alcohol) and Polyacrylamide (Polyacrylic acid), were selected for comparison. For the studied PVA1788 and Polyacrylamide particles, with an increase in relative humidity, the porosity of the filter cake increased monotonously, while the total filtration resistance decreased monotonously. For DM828 particles, the cake porosity first decreased and then increased, and the total filtration resistance first increased and then decreased, with an inflection point at 30% RH. By combining these results with existing reports, three kinds of variations of the filtration performance with humidity could be determined: (1) as the humidity increased, the filtration resistance first increased and then decreased; (2) the filtration resistance decreased; and (3) the filtration resistance increased.

Long-term effect of weather in Dfb climate subtype on properties of hydrophobic coatings on sandstone

Hydrophobic poly(alkyl siloxane) coatings (pure and containing 0.5 wt% of nano-ZnO) were applied by spraying on sandstone. Coated (S/P and S/PZnO) and uncoated (S) samples were characterized and exposed to weather for 545 days in Ostrava, Czech Republic, an industrial city having persistently high concentrations of particulate matter in air (PM10 ≈ 20±10 μg/m3) and belonging to the Dfb climate subtype. Despite the more distinct final colour change of S/P and S/PZnO front faces, the differences between front and back faces were significantly smaller (ΔE*F–B values of ∼3.7 and ∼3.1 for S/P and S/PZnO, respectively) compared to S (ΔE*F–B ≈ 7.7). Correlations of colour changes with meteorological data revealed effect of relative air humidity, total precipitation, and concentration of particulate matter. Static contact angle (initial values of 137° and 142° for S/P and S/PZnO, respectively) remained >120° during the experiment, and the coatings effectively prevented the falling rainwater to soak into the sandstone. The high hydrophobicity was not accompanied by closure of pores. Despite a decrease in Zn content, no algae was observed on S/PZnO during the experiment. On S and S/P samples, the algae was found after 473 days.

Climatic determinants of lowland rice development

AbstractAccurate modelling of plant development is the basis for any assessment of climate change impact on crop yields. Most rice models simulate development (phenology) based on temperature and photoperiod, but often the reliability of these models is reduced beyond the environment they were calibrated for. In our study, we tested the effects of relative air humidity and solar radiation on leaf appearance rate in greenhouse experiments and analysed data sets from field studies conducted in two extremely different rice‐growing environments in Nepal and Senegal. We also analysed environmental effects on duration to flowering of one popular IRRI material (IR64) for eight different sites covering the entire temperature range where rice is widely cultivated. Both low relative air humidity and low solar radiation significantly decreased leaf appearance rate. Mean air temperature explained 81% of the variation in duration to flowering across sites, which was furthermore significantly influenced by relative air humidity. Across all sites, a simple linear regression approach including mean air temperature and mean relative humidity in the calculation of duration to flowering led to a root mean square error (RMSE) of 10 days, which was slightly lower than the RMSE of 11 days achieved with an automated calibration tool for parameter optimization of cardinal temperatures and photoperiod sensitivity. Parameter optimization for individual sites led to a much smaller prediction error, but also to large differences in cardinal temperatures between sites, mainly lower optimum temperatures for the cooler sites. To increase the predictive power of phenological models outside their calibration range and especially in climate change scenarios, a more mechanistic modelling approach is needed. A starting point could be including relative air humidity and radiation in the simulation procedure of crop development, and presumably, a closer link between growth and development procedures could help to increase the robustness of phenological models.

Responses of Rice Growth to Day and Night Temperature and Relative Air Humidity-Dry Matter, Leaf Area, and Partitioning.

Asymmetric changes of day and night temperature have already been observed because of Climate Change. However, knowledge on environmental conditions either during day or night serving as trigger for growth processes is scarce. In this study, one rice (Oryza sativa) variety (IR64) was examined to assess the impact of varying temperatures and relative air humidities during day and night periods on biomass, leaf area, and dry matter partitioning between organs. Three different day and night temperature (30/20 °C, 25/25 °C, 20/30 °C) and relative air humidity (40/90%, 65/65%, 90/40%) regimes were established. The effect of relative air humidity on both plant dry matter and leaf area was larger than the effect of temperature, in particular low humidity had a strong negative impact during the night. With high day temperature, the shoot mass fraction increased, whereas the root mass fraction decreased. Specific leaf area increased at high night temperatures and led, along with the high leaf mass fraction at high night humidities, to higher growth rates. The results emphasize the importance of considering relative air humidity when focusing on plant responses to temperature, and strongly suggest that under asymmetric day and night temperature increases in the future, biomass partitioning rather than biomass itself will be affected.

Effect of Relative Air Humidity and High Temperature on the Physiological and Anatomical Responses of Two Rhododendron Cultivars

The effects of different relative air humidity (RH) levels under high temperature and accompanying vapor pressure deficits (VPDs) on the physiology, photosynthesis, and anatomy of Rhododendron need to be better understood to help in reducing damage to leaves caused by high temperature. In this study, two Rhododendron cultivars were exposed at 45%, 55%, 65%, 75%, and 85% RH to a treatment of constant temperature at 38 °C for 14 days, resulting in a VPD of 3.64, 2.98, 2.32, 1.66, and 0.99 kPa, respectively. The results showed the least reduction of the net photosynthetic rate (Pn) under 75% RH treatment in R. ‘Fen Zhenzhu’ (decreased by 79.8%), and under the 85% RH treatment in R. ‘Zhuangyuan Hong’ (decreased by 75.4%). The decline in relative water content (RWC) was less under the 75% and 85% RH treatments, and electrolyte leakage showed a slight decrease under the 75% RH treatment in the two Rhododendron cultivars. The appearance of the two cultivars under greater RH showed less damage, probably because plants can avoid damage by increasing total chlorophyll content, decreasing stomatal area, stomatal density, and opened stomata ratio, enhancing enzymatic activity and osmoregulation substances, and improving leaf structure. The findings show that greater RH can alleviate damage caused by heat stress and improve thermostability.

Fuzzy comprehensive evaluation of the effects of relative air humidity on the morpho-physiological traits of Pakchoi (Brassica chinensis L.) under high temperature

This study was conducted to investigate the effects of relative air humidity (RH) on morphological and physiological traits of Pakchoi (Brassica chinensis L.) under high temperature. Pakchoi was planted in climate chambers at 35/28 °C, day / night temperature, and the RH levels were 20%, 40%, 60%, 80%, and 95%. Most growth parameters peaked at 40–60% RH under high temperature. Biomass, leaf area, net photosynthetic rate (Pn), soluble sugar, and vitamin C were the highest at 60% RH, whereas total chlorophyll content, transpiration rate, and leaf air temperature were the highest at 40% RH. Superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) activities were the highest at 80% RH. All the above properties showed the lowest value at 95% RH. Malondialdehyde (MDA) peaked at 95% RH, and severe chlorosis was observed simultaneously. Based on our fuzzy comprehensive evaluation, the fuzzy value of production and intrinsic quality was the highest at 60% RH and lowest at 95% RH. RH does affect the temperature difference between leaf and air from the change of transpiration. Excessively high or low RH caused a significant reduction in biomass production and intrinsic quality. We found that 60% RH was the optimum level for growth of Pakchoi at high temperature. With 95% RH, the Pakchoi was damaged under high temperature; Pn, SOD, CAT, and POD activities were the lowest; and MDA content was the highest. Results suggested that proper RH level could reduce leaf temperature and maintain stomatal conductance, thereby maintaining the high yield of Pakchoi via higher photosynthetic efficiency at high temperature.

Tipburn Severity and Calcium Distribution in Lisianthus (Eustoma Grandiflorum (Raf.) Shinn.) Cultivars under Different Relative Air Humidity Conditions

Tipburn is a major problem for the production of lisianthus (Eustoma grandiflorum (Raf.) Shinn.) cultivars. Relative air humidity is regarded as a key environmental factor affecting tipburn severity in commercial crops. However, there are limited studies comparing the occurrence of tipburn and calcium (Ca) distribution in lisianthus cultivars under different relative air humidity conditions. Accordingly, we investigated the effect of relative air humidity on tipburn severity, transpiration rate, and Ca content in seven lisianthus cultivars. Under a high humidity treatment (70%), only two cultivars (“Voyage pink” (VP) and “Azuma-no-kaori” (AK)) showed significantly higher tipburn severity than those under a low humidity treatment (50%), which suggests that high humidity conditions do not always increase tipburn severity in lisianthus. Transpiration rates of all cultivars, except for AK, were either significantly lower under the high humidity treatment than under the low humidity treatment, or did not vary significantly between the treatments. In contrast, total Ca concentrations in all cultivars, except for “Piccolosa snow” (PS), were significantly higher under the high humidity treatment than under the low humidity treatment. These results suggest that Ca acquisition and distribution in lisianthus cultivars are strongly influenced by Ca uptake from root pressure.

Abatement of mixed volatile organic compounds in a catalytic hybrid surface/packed-bed discharge plasma reactor

In this study, post plasma-catalysis degradation of mixed volatile organic compounds (benzene, toluene, and xylene) has been performed in a hybrid surface/packed-bed discharge plasma reactor with Ag-Ce/g-Al2O3 catalyst at room temperature. The effect of relative air humidity on mixed VOCs degradation has also been investigated in both plasma-only and PPC systems. In comparison to the plasma-only system, a significant improvement can be observed in the degradation performance of mixed VOCs in PPC system with Ag-Ce/γ-Al2O3 catalyst. In PPC system, 68% benzene, 89% toluene, and 94% xylene were degraded at 800 J·L–1, respectively, which were 25%, 11%, and 9% higher than those in plasma-only system. This result can be attributed to the high catalytic activity of Ag-Ce/γ-Al2O3 catalyst to effectively decompose O3 and lead to generating more reactive species which are capable of destructing the VOCs molecules completely. Moreover, the presence of Ag-Ce/γ-Al2O3 catalyst in plasma significantly decreased the emission of discharge byproducts (NOx and O3) and promoted the mineralization of mixed VOCs towards CO2. Adding a small amount of water vapor into PPC system enhanced the degradation efficiencies of mixed VOCs, however, further increasing water vapor had a negative impact on the degradation efficiencies, which was primarily attributed to the quenching of energetic electrons by water vapor in plasma and the competitive adsorption of water vapor on the catalyst surface. Meanwhile, the catalysts before and after discharge were characterized by the Brunauer-Emment-Teller and X-ray photoelectron spectroscopy.

The Examination of the Effects of Relative Humidity on the Changes of Tropospheric Ozone Concentrations in the Ciuc Basin, Romania

As ozone is a secondary polluting substance, its oxides of nitrogen (NOx) play a significant role as precursors. Their existence is influenced by climatological and meteorological parameters, as well as other air pollutants (SOA, VOC). At present, alongside with various meteorological parameters (temperature, wind speed, relative humidity, sun intensity), other air pollutants (oxides of nitrogen, carbon monoxide, benzene) and other physical phenomena (dry deposition, meteoric stability) mostly the indirect effects of relative air humidity was examined in relation with the evolution of tropospheric ozone concentration. Our aim was, to examine the closed experiment of Jia and Xu (2014) (smog chamber), under atmospheric conditions, according to which in the case of high relative humidity the formation of ozone falls if benzene and ethylbenzene are added. According to the results, relative humidity has an increasing effect on water radical reactions and the hydration of glyoxal, while the concentration of the ozone changes as a result. At the same time, it can be observed that the higher the value of relative humidity is, the higher are also the values of ONO2, benzene and CO, whereas the concentration of O3 decreases. The reactions caused by the relative humidity of the air and VOC concentration in the experiment of Jia and Xu (2014) produced relatively adversary demonstrations in natural environment, because the experiment had been carried out at room temperature, whereas temperature and other parameters are subject to constant change in the natural environment.

Effect of relative air humidity on the flowability of lactose powders

Moisture is known to affect the flowing properties of powders. However, the quantification and the understanding of the observed effects are far to be obvious. To study air moisture influence on powder flowability in a laboratory, a conditioning system and a precise flowmeter are necessary. Simple flow testers, which are commonly used R&D laboratories, are not able to quantify precisely the effect of moisture on powders. The use of advanced techniques is necessary. In this paper, we present how a precise and user-friendly flowability test associated with a dynamic conditioning system can be used to quantify the influence of moisture on the flowability properties of lactose powders. The effect of residence time T in high humidity conditions is analyzed. Afterward, we show that the relative humidity range that optimizes the flowability of lactose powders is between 30% and 50%. For lower values of the relative humidity, the apparition of electric charges inside the bulk induces cohesive forces. For higher relative humidity, the condensation of the air humidity at the contact between the grains forms capillary bridges which favors also the cohesive interactions. A model taking both triboelectric and capillary effects into account is proposed to fit the experimental data.

Effects of relative air humidity on the phenolic compounds contents and coloration in the ‘Fuji’ apple (Malus domestica Borkh.) peel

To investigate the effects of relative air humidity (AH) on ‘Fuji’ apple (Malus domestica Borkh.) peel phenolic compounds and pigment coloration, the bagged fruits were bags moved and then exposed to high AH and low AH conditions, respectively. Cyanidin-3-galactoside, the main anthocyanin compound in apple, and 17 other types of phenolic compounds were detected and their concentrations were also compared between high and low AH treated apple peels. We observed that the removal of bags and subsequent re-exposure to sunlight could significantly decrease the concentrations of syringic acid, caffeic acid, ρ-coumaric acid, and quercetin-3-rhamnoside, but increase the concentrations of ferulic acid, quercetin-3-galactoside, quercetin-3-glucoside, quercetin-3-rutinoside, and cyanidin-3-galactoside. Furthermore, high AH samples had higher concentrations of chlorogenic acid, ferulic acid, epicatechin, quercetin-3-rutinoside, and cyanidin-3-galactoside than low AH samples as they were in the similar temperature conditions. These results suggested that high AH conditions could significantly improve coloration and the eating quality of fruits.

The effect of weather variables on the flight activity of horseflies (Diptera: Tabanidae) in the continental climate of Hungary

Although the tabanid species and populations occurring in eastern central Europe (Carpathian Basin) are thoroughly studied, there are only sporadic data about the influence of weather conditions on the abundance and activity of horseflies. To fill in this lack, in Hungary, we performed a 3-month summer survey of horsefly catches registering the weather parameters. Using common canopy traps and polarization liquid traps, we found the following: (i) rainfall, air temperature, and sunshine were the three most important factors influencing the trapping number of tabanids. (ii) The effect of relative air humidity H on tabanids was indirect through the air temperature T: H ≈ 35 % (corresponding to T ≈ 32 °C) was optimal for tabanid trapping, and tabanids were not captured for H ≥ 80 % (corresponding to T ≤ 18 °C). (iii) A fast decrease in the air pressure enhanced the trapping number of both water-seeking and host-seeking horseflies. (iv) Wind velocities larger than 10 km/h reduced drastically the number of trapped tabanids. Our data presented here may serve as a reference for further investigations of the effect of climate change on tabanids in Europe.

The Effect of Relative Air Humidity on the Rheological Properties of Roasted Turkey Breast

The effect of relative humidity (RH) of air on the mechanical properties of roasted turkey breast was studied using a rheological model. The raw turkey breast with a moisture content of ca. 75%, protein content of ca. 24% and fat content of ca. 1% was roasted in a convection steam oven at 180C and five RH levels (0, 20, 50, 70 and 90%). The elastic modulus decreased, whereas the flow consistency index and the flow limit increased with an increase in RH from 0 to 70%. Significant differences were observed in elastic modulus between RH levels of 0 and 20% versus 50, 70 and 90%. As regard the flow consistency index and the flow limit, significant differences were observed between 0 versus 50 and 70% RH levels. No significant differences in those values were reported at RH exceeding 50%. The flow consistency index was independent of RH of air level. Practical Applications The proposed method can be used to determine the effect of treatment parameters on the rheological properties of the analyzed product, and to assess its final quality. The presented mathematical model allows to evaluate the rheological properties of turkey breast meat roasted in a convection steam oven independently of the type of mechanical tests used to determine those values. The obtained results support the selection of roasting parameters (relative humidity) aimed at yielding a product with the desired rheological properties.

Hypertension, pregnancy and weather: is seasonality involved?

The present study aimed at assessing the association between environmental temperature and the relative humidity of the air with frequency of hypertensive disorders of pregnancy. A prospective and retrospective, descriptive, ecological study was held at a teaching maternity in Recife, Brazil. Data from all 26.125 pregnant women admitted between 2000 and 2006 were analysed and 5.051 had the diagnosis of hypertensive disorder of pregnancy. The incidence percentages were calculated monthly per deliveries. Data on mean monthly temperature and relative humidity of the air were collected and monthly comparisons were conducted. February was chosen as the reference month due to its lowest incidence of the disease. The relative chance of hypertensive disorders of pregnancy for each other month was estimated by odds ratio and Pearson's correlation coefficient was used to calculate the relation between the incidence of hypertensive disorders of pregnancy and the mean monthly temperature and relative air humidity. February presented the lowest mean monthly incidence (9.95%) and August the highest (21.54%). Pearson correlation coefficient revealed a higher incidence of hypertensive disorders of pregnancy in the cooler months (r= -0.26; p=0.046) and no significant effect of relative air humidity (r=0.20; p=0.128). The incidence of hypertensive disorders of pregnancy may be affected by variations in temperature, increasing during cooler periods.

Effect of relative air humidity on photoacoustic aerosol absorption measurements in the near-ground atmospheric layer

The paper discusses wintertime synchronous near-ground measurements of the aerosol absorption coefficient at wavelengths of 532 and 1064 nm and the black carbon mass concentration by pulsed photoacoustic (PA) spectroscopy and optical aethalometry, respectively. It was found that the signal of the pulsed PA spectrometer decreases monotonically, by 30–40% on average, as the relative air humidity increases from 30 to 90%. Analysis of the data has shown that the PA method is efficient for studying the absorption of laser radiation in the range of low humidity values, i.e., for measurements of the aerosol absorption coefficient of “dry” carbonaceous particles. Correctness of the aerosol absorption measurements for increased relative air humidity (60–90%) can be improved through a sensitivity correction (additional calibration) of PA spectrometers.