Effect Of Relative Humidity Research Articles

The Effect of Relative Humidity on Creep Behavior of Cement Paste Microprism

Despite decades of extensive studies, the mechanism of concrete creep remains a subject of debate, mainly due to the complex nature of cement microstructure. This complexity is further amplified by the interplay between water and the cement microstructure. The present study aimed to better understand the creep mechanism through creep tests on microprisms of cement paste at hygral equilibrium. First, microprisms with dimensions of 150 mm × 150 mm × 300 mm were prepared by precision cutting from a cement paste specimen with a water-to-cement ratio of 0.4. Subsequently, uniaxial compression and creep tests were carried out on these microprisms in a chamber with controlled relative humidity (RH). To mitigate the impact of plasticity and damage, the applied peak load was set to generate a stress level that was approximately 40% of the compressive strength. Moreover, an analytical coefficient φ was formulated to account for the foundation effect on microprism creep, agreeing with the numerical analysis employing the finite element method. Our findings showed that the microscale creep compliance varied when the RH level was changed from 90% to 11%. Furthermore, logarithmic and power-law models were both applied to simulate creep curves. Lastly, the modeled creep behaviors were compared with those obtained by microindentation experiments in previous studies.

Impact of Meteorological Parameters on Global Solar Radiation (GSR) at Nepalgunj Airport, Nepal

Global solar radiation (GSR), is the main source of heat that powers the energy between the geosphere and the atmosphere, is the total of the direct and diffused shortwave solar radiation that reaches the earth's surface. The target of the present report is to analyze the GSR from the data of Nepalgunj airport, Nepal in 2020. In addition, to analyze the effect of rainfall, relative humidity, maximum temperature, and minimum temperature to the GSR. The data on a horizontal surface for Nepalgunj airport, Nepal in 2020 were collected from the Department of Hydrology and Meteorology, Government of Nepal. The Angstrom-Prescott, Tiwari, and Sangeeta models were used to calculate the GSR theoretically on a horizontal surface with the help of the estimated sunshine hour. The yearly average value of GSR for the year 2020 was 18.73 MJ/m2/day. The measured GSR on a horizontal surface was found maximum in April which was 27.64 MJ/m2/day and minimum in August which was 6.38 MJ/m2/day The minimum amount of GSR found in August may be due to the high amount of rainfall of 10.51 mm in August. Talking about the seasonal variation, the Spring season receives the maximum amount of GSR i.e. 24.75 MJ/m2/day and the minimum amount is in winter i.e. 9.13 MJ/m2/day. Here, the summer season belongs to June, July, and August, and the minimum amount of solar radiation was found in August. During that month a high amount of rainfall was observed, and minimum amount of average temperature was observed. On studying the graph of variation of GSR with various meteorological parameters well-accepted relations were found. A direct relation is found between GSR and average maximum temperature, minimum temperature, rainfall, and relative humidity.

Study on the Aging Effects of Relative Humidity on the Primary Chemical Components of Palm Leaf Manuscripts.

Palm Leaf Manuscripts represent a significant component of the world's cultural heritage. Investigating their primary chemical components and understanding the transformations these materials undergo under environmental influences are crucial for elucidating their material characteristics and aging mechanisms and developing effective strategies for preventive conservation. This study utilized infrared absorption spectroscopy and X-ray diffraction analysis to examine changes in the primary chemical components of Palm Leaf Manuscripts under varying relative humidity conditions over extended periods. The findings reveal that dry environments lead to surface cracking, while humid environments promote mold growth, both of which contribute to the degradation of the primary chemical components. These degradative processes reduce cellulose crystallinity and thermal stability. The deterioration is particularly severe under high humidity, with hemicellulose degrading faster and more extensively than cellulose under the same conditions. After 200 days of aging at 10% RH and 90% RH, cellulose degradation reached 19.82% and 54.40%, respectively, while hemicellulose degradation was 34.78% and 64.28%. Correspondingly, the relative crystallinity of cellulose decreased by 8.01% and 13.11%. In contrast, samples maintained at 50% RH exhibited minimal deterioration, with cellulose and hemicellulose degrading by only 4.08% and 13.55%, respectively, and a 6.61% reduction in cellulose crystallinity. These results suggest that a relative humidity of 50% is optimal for the preservation of Palm Leaf Manuscripts. This study offers significant insights into the ageing mechanisms and preventive conservation of Palm Leaf Manuscripts, as well as other cellulose-based organic heritage materials.

Effect of Moisture Sorption and Lactose Type on Tablet Quality: A Hygroscopicity Study between Lactose Powder and Tablets.

Lactose is one of the most commonly used tablet diluents and fillers. However, the moisture sorption of lactose powder could exert detrimental effects on the excipient itself, as well as on the tablet quality. The effects of storage relative humidity (RH) conditions for different grades of lactose powders and tablets on compression behavior and tablet qualities were investigated. Four types of lactose were selected in this study: sieved lactose (Pharmatose 110M), granulated lactose (SuperTab 30GR), anhydrous lactose (SuperTab 21AN), and spray-dried lactose (SuperTab 14SD). These powders and tablets were stored at three RH levels (33, 58, 75%) for a certain period of time before determining their properties. For the moisture-sorbed powder, there was little change in the basic physical properties of lactose powder. Based on the dynamic vapor sorption (DVS) results, the lactose grades determined their hygroscopic properties. The reduction in mechanical strength of lactose powder during storage became less pronounced except for 14SD. But a reduction was observed in the tensile strength (TS) of the 14SD powder from 2.1 to 0.9 MPa after storage at 75% RH for 30 days. The fragmentation of lactose increased with increasing storage humidity. By using multivariate statistical analysis, the similarity and variation of powder properties between 14SD and other types of lactose were visualized. For the moisture-sorbed tablet, the TS became higher and the friability became lower. The TS of lactose tablets exhibited an increase of up to 59.8%. Whether water uptake occurred before or after compression adversely affected tablet disintegration. In conclusion, adverse phenomena during production and storage can be effectively minimized by a better understanding of the effects of moisture sorption on lactose powder and tablets.

Cavitation, Hydrophilicity, and Sorption Hysteresis in C-S-H Pores: Coupled Effects of Relative Humidity and Temperature.

Sorption processes are critical for the drying and durability of cement-based materials, directly affecting their thermal properties. Temperature can substantially influence these processes. This work uses molecular simulations to study sorption in C-S-H pores under varying temperatures and relative humidity, considering pore sizes from the gel to the interlayer scale (between 11.6 and 106 Å). We quantify the temperature and pore-size dependence of water cavitation and sorption hysteresis in the C-S-H pores. The critical pore sizes for the disappearance of hysteresis and the reversibility of capillary condensation are identified, with the former being directly associated with cavitation. We show that cavitation occurs only in gel (meso)pores when they are above the critical pore size and below the critical temperature for cavitation. Interlayer pores, a major class of micropores in C-S-H, are not subjected to cavitation. Cavitation in C-S-H pores is homogeneous, occurring in the bulk-like zone of mesopores. The hydrophilicity of the C-S-H surface increases with the temperature, making heterogeneous cavitation less likely to occur. The results above were obtained consistently with three different force field parametrizations, building confidence in their relevance to describe C-S-H interfacial behavior. Finally, we demonstrate that macroscopic considerations for pore emptying and filling, such as the Kelvin-Cohan and equilibrium Derjaguin-Broekhoff-de Boer equations, are not valid or inaccurate when desorption occurs through cavitation in C-S-H. These results are relevant to understanding the sorption processes in other nanolayered adsorbing materials.

Numerical Simulation of a Wavy Fin-and-Tube Heat Exchanger Under Wet Conditions

In order to analyze the influence of condensation behavior on the heat transfer process of large heat exchangers under wet conditions, a three-dimensional numerical model of condensation heat transfer of twelve-row wavy fin-and-tube heat exchangers under wet conditions was established. The effects of inlet velocity and relative humidity on heat and mass transfer characteristics were investigated. Through the analysis of the field synergy principle, it is found that the wavy fin can effectively improve the synergy between the velocity field with the temperature field and the concentration field. The wavy fin not only increased the disturbance of fluid but also continuously disrupted the developments of thermal and mass concentration boundary layers, thereby greatly enhancing the heat and mass transfer. The condensation mainly occurs on the first six pipe rows, and the increase of inlet velocity makes the condensation area obviously larger. The inlet relative humidity has little effect on the temperature distribution and sensible heat transfer under wet conditions but has a significant effect on the latent heat transfer and total heat transfer. Finally, the relationship for convective heat transfer coefficients under wet and dry conditions is obtained by multivariate fitting.

Synergistic analysis of oxygen transport resistance in polymer electrolyte membrane fuel cells

The oxygen transport resistance of polymer electrolyte membrane fuel cells operated under various conditions (e.g., temperature and relative humidity) was separated into molecular diffusion, Knudsen diffusion, and ionomer film (IF) resistances using the catalyst agglomerate model, dissection of oxygen transport resistance, and distribution of relaxation time analysis. Simultaneously, an analysis of resistance, including charge transfer, proton transfer, and high-frequency resistances, was performed. The Knudsen diffusion resistance of the catalyst layer was calculated by assessing the effects of relative humidity on porosity and pore size. Oxygen transport resistance was analyzed to establish a correlation between temperature, relative humidity, and IF resistance. Water negligibly impacted performance at low oxygen levels at all examined current densities. The fractional contributions of molecular diffusion, Knudsen diffusion, and IF resistances obtained using oxygen transport analysis could be effectively applied to mass transport resistance in the distribution of relaxation time analysis. The IF resistance in the catalyst layer was up to eight times higher than the Knudsen diffusion resistance and 150 times higher than the proton transfer resistance across all current densities, thus most strongly contributing to the catalyst layer resistance. In the gas diffusion layer, the molecular diffusion resistance was up to four times higher than the Knudsen diffusion resistance. Thus, we examined the relationship between the mass transport resistances of individual elements and IF behavior under different operating conditions, revealing that the design of the IF in the catalyst should be considered alongside the relationship between the gas diffusion layer and membrane for optimal performance.

Effect of wide reactant relative humidity on PEMFC electrochemical and thermodynamic performance from both global and local perspectives

For realizing high-power and high-efficiency operation of proton exchange membrane fuel cell (PEMFC), influence mechanism of relative humidity (RH) on the fuel cell performance was explored in this study. Combining experimental and simulation methods, the effect of wide gas humidification on the fuel cell output power and irreversible losses were comprehensively studied. Rising RH negatively influenced PEMFC electrochemical and thermodynamic properties at I=1.6 A/cm2. Humidification of the gas can lead to a maximum increase of 36%, 43% and 14.5% in cell exergy efficiency at I=0.2-0.4 A/cm2, I=0.4-1.2 A/cm2 and I=1.2-1.4 A/cm2, respectively. The effect of RH on the pressure drop at a wide current densities was identified using a two-phase multiplier, and further can be categorized into three zones. Electrochemical impedance spectroscopy (EIS) results showed that mass transfer losses and activation losses are keys to influence the characteristics of the above regions. Cathode catalyst layer (CCL) and proton exchange membrane (PEM) contributed more than 90% to thermal irreversible loss, whose entropy generation rates change is consistent with activation loss. These study results can provide theoretical support for the development of PEMFC with high output power and high exergy efficiency at wide gas humidification conditions.

Initial investigation of the relative humidity effect on the convective heat exchange using full-scale wind tunnel experiments

Abstract In this paper, an initial investigation of the effect of relative humidity on the rate of convective heat exchange is carried out. For this reason, a specific sample design was developed that was tested in the unique closed-circuit wind tunnel laboratory that allows for investigation of various environmental loads on full-scale samples. The analysis of experimental data indicated the relative humidity as a potential key factor with a sufficient level of significancy that may seriously affect the rate of convective heat exchange between sample surface and ambient air.

The effect of ambient temperature and relative humidity in postpartum dairy cows on productive and reproductive performance and biochemical blood indices in the subsequent lactation

Abstract This study evaluated the effects of ambient temperature (T) and relative humidity (RH) during the postpartum transition period on dairy cows’ milk performance, fertility, and immunometabolic blood indices in the subsequent lactation. A total of 100 Polish Holstein-Friesian cows originating from five commercial dairy farms were categorized into three groups based on average T (<16 °C, 16-20 °C and >20 °C) and RH (<65%, 65-75%, and >75%) on the calving day (0d), and days 7, 14, 21 after calving. With increasing T and RH postpartum, the average daily milk yield during the first 150 days in milk decreased gradually, and the differences between T <16 °C and >20 °C and RH <65% and >75% groups were approx. 3.48 and 2.78 kg, respectively. Milk of cows exposed to increased T and RH was lower in protein, and lactose and higher in fat, milk urea, and somatic cell count. It was also characterized by altered fat composition. Ambient T during the postpartum period had a negative effect on cows’ fertility, which, however, was not affected by RH. The increasing T from <16 °C to >20 °C resulted in the later manifestation of the first estrous (by 27.7 days), a more extended artificial insemination service period (by 19.4 days), a higher number of insemination services per conception (by 0.92 on average), more days open (by 43.3 days), and a longer calving interval (by 43.3 days). Within ranges used in this study, increasing T and RH during the period from d 0 to d 14 postpartum led to decreased body condition score on day 21 by approx. 0.48 and 0.51 points, respectively. Furthermore, T and RH on a calving day were associated with altered biochemical blood indices on d 21 after calving, indicating a more severe negative energy balance and a state of inflammation. The results of this study suggest that dairy cows that calve when T >16 °C should be provided cooling to ensure optimal environmental conditions for high milk production and prevent economic losses associated with reduced milk yield and low fertility.

Combined Effect of Ambient Temperature and Relative Humidity on Skin Aging Phenotypes in the Era of Climate Change: Results From an Indian Cohort Study.

Background: There is no doubt that global warming, with its extreme heat events, is having an increasing impact on human health. Heat is not independent of ambient temperature but acts synergistically with relative humidity (RH) to increase the risk of several diseases, such as cardiovascular and pulmonary diseases. Although the skin is the organ in direct contact with the environment, it is currently unknown whether skin health is similarly affected. Objective: While mechanistic studies have demonstrated the mechanism of thermal aging, this is the first epidemiological study to investigate the effect of long-term exposure to heat index (HI) as a combined function of elevated ambient temperature and RH on skin aging phenotypes in Indian women. Methods: The skin aging phenotypes of 1510 Indian women were assessed using the Score of Intrinsic and Extrinsic Skin Aging (SCINEXA™) scoring tool. We used data on ambient temperature and RH, combined into an HI with solar ultraviolet radiation (UVR), and air pollution (particulate matter <2.5 µm [PM2.5]; nitrogen dioxide [NO2]) from secondary data sources with a 5-year mean residential exposure window. An adjusted ordinal multivariate logistic regression model was used to assess the effects of HI on skin aging phenotypes. Results: HI increased pigmentation such as hyperpigmented macula on the forehead (odds ratios [OR]: 1.31, 95% confidence interval [CI]: 1.12, 1.54) and coarse wrinkles such as crow's feet (OR: 1.17, 95% CI: 1.05, 1.30) and under-eye wrinkles (OR: 1.3, 95% CI: 1.15, 1.47). These associations were robust to the confounding effects of solar UVR and age. Prolonged exposure to extreme heat, as indicated by high HI, contributes to skin aging phenotypes. Conclusion: Thus, ambient temperature and RH are important factors in assessing the skin aging exposome.

A study of the correlation between meteorological factors and hospitalization for acute lower respiratory infections in children

BackgroundThe study focuses on the effect of temperature and relative humidity on hospitalization for acute lower respiratory tract infections (LRTI) in children, respectively.MethodsIn this study, the Distributed Lag Nonlinear Model (DLNM) based on quasi-Poisson distribution was used to investigate the effect of temperature and relative humidity on LRTI hospitalization in children, and subgroup analyses were conducted to identify sensitive populations by gender and age.ResultsA total of 43,951 children were hospitalized for LRTI from 1 January 2014 to 31 December 2019 in Lanzhou. The mean temperature during the study period was 11.34 °C and the mean relative humidity was 51.03%. With reference to the median temperature of 12.7 °C during the study period, both low (-4.1 °C) and high (25.43 °C) temperature had a detrimental effect on LRTI hospitalization, and the maximum effect was reached at lag0-10 and lag0-9, respectively, with RR values of 1.645 (95%CI: 1.533, 1.764) and 1.098 (95%CI: 1.018, 1.184). With a reference to the median relative humidity of 51.17% during the study period, both low relative humidity (26.71%) and high relative humidity (76.70%, P95) had a detrimental effect on LRTI hospitalization, and the maximum effect was reached at lag0-21 and lag21, respectively, with RR values of 1.235 (95% CI: 1.163, 1.311) and 1.044 (95% CI: 1.036, 1.051). The results of subgroup analyses showed that changes in meteorological factors had a stronger effect on Female and children aged 5–14 years.ConclusionsThe meteorological factors all have different degrees of influence on LRTI hospitalization in children. Girls and the children aged 5–14 years are more sensitive. Attention to these meteorological risks can inform targeted interventions.

Effects of relative humidity on carbonation kinetics and strength development of carbonated wollastonite composites containing sodium tripolyphosphate

Assessing the impact of relative humidity (RH) on carbonation kinetics is crucial for the sustainable and high-strength advancement of CO2-activated Ca-bearing materials incorporating phase-controlling additives. This work focuses on the carbonation kinetics, mechanical properties, and microstructure evolution of carbonated wollastonite composites containing sodium tripolyphosphate (STPP) when exposed to various RH levels. Results show that RH plays an important role during the carbonation of wollastonite, functioning both as a reaction material and accelerating role for wollastonite carbonation. The carbonation rate and the phase transition reaction of poorly crystalline CaCO3 is accelerated at RH ranging from 70% to 95%, favouring to cementitious behaviour of CaCO3 and results in denser microstructure, especially for 85% RH. The carbonation reaction is composed of two distinct stages, namely, wollastonite dissolution and precipitation of the stage-1 and ion-diffusion controlling of stage-2. Among them, the addition of STPP prolong the carbonation duration of stage-1. The degree of carbonation (DOC) of the internal layer sample is higher than that of the outermost layer sample. CaCO3 and silica gel are evenly distributed indirectly, which reduces the elastic modulus at 85 % RH. However, regardless of RH, the cementitious efficiency of poorly crystalline CaCO3 is the highest, followed by calcite and silica gel. Consequently, STPP modified carbonated wollastonite shows highest strength when exposed to 85% RH (67.3 MPa at 7 days). Our study provides a unique way toward developing the STPP-containing carbonated wollastonite system for high performance carbonated materials.

Effects of relative humidity on atmospheric organosulfur species derived from photooxidation and nocturnal chemistry in a forest environment

The molecular composition of organic aerosols in ambient PM2.5 was investigated at the northern foothills of Qinling Mountain region in central China during the summer of 2022. The molecular characteristics of organic matter were analyzed using ultrahigh performance liquid chromatography coupled with high-resolution Orbitrap mass spectrometry. The number of molecular formula assignments was dominated by organosulfur species (OrgS, on average 28–47% in total). Both the number and peak area of OrgS increased significantly with higher relative humidity (RH), while those of CHO and CHON species decreased, indicating the different impacts of RH on individual organic groups. The entire study period was divided into two distinct stages, including a low RH and a high RH period (LRH and HRH). The enhanced formation of CHOS with O>7 in HRH was primarily attributed to photochemical oxidation, whereas the increase in CHONS with O>7 was driven by enhanced NO3 radical-initiated oxidation under elevated RH conditions. Nearly 50% of OrgS presented only in HRH had aliphatic structures with C≥9. Although isoprene-derived organosulfates dominated the peak area across the entire period, the monoterpenes and long-chain alkanes-derived organosulfates largely increased in HRH. The strong correlations between aerosol liquid water content and OrgS containing high oxygen content (O>7) indicate that aqueous-phase reactions played a crucial role in multigenerational oxidation of OrgS. This study highlights the important effects of RH on the formation of OrgS, particularly for organosulfates derived from monoterpenes and long-chain alkanes.

Effect of temperature and relative humidity on hydrolytic degradation of additively manufactured PLA: Characterization and artificial neural network modeling

Understanding the long-term durability of 3D-printed polymeric materials under varying temperature and humidity conditions is essential for expanding their industrial applications. Therefore, it is critical to assess the impact of degradation on mechanical properties such as tensile strength. In this study, we manufactured specimens with dual orientations by additive manufacturing-based 3D printing and subjected them to accelerated degradation under various temperature and humidity conditions to evaluate their durability in degradation environments. Mechanical properties significantly decreased under the most severe conditions, with a maximum reduction of 76.7 % observed in molecular weight. The deconvolution of the molecular weight distribution and its correlation with mechanical properties were thoroughly investigated. We derived an equation representing the relationship between the peaks obtained from deconvoluting the molecular weight distribution and the tensile strength. Furthermore, to expedite and simplify tensile strength assessment, we trained an artificial neural network (ANN) model using tensile test results to construct a predictive model. The ANN utilized temperature, humidity, printing angle, and time as input data, with tensile strength as the output. Validation of this model demonstrated the capability to predict tensile strength accurately under different temperature and humidity conditions.

Studies On The Statistical Analysis And Impact Of Seasonal Temperature And Relative Humidity Variation On The Development Of A Flesh Fly Sarcophagadux(Thomson 1869)(Diptera Sarcophagidae)

Background: The fleshfly Sarcophaga dux (Diptera;Sarcophagidae) is found in Indian Sub continent is of limited forensic significance as its poorly known larval development relationship with temperature and relative humidity. Objective: The objective of this study was to determine the effect of the temperature and relative humidity in the larval development of this fly in two seasons, Summer and Rain, so that the results of this study may enabling the forensic use of this fly in the estimation of Post Mortem Interval(PMI). Material and Method: The present study was carried out in the outer premises of the Regional Forensic Science Laboratory Building, Jagdalpur, Bastardist,Chhattishgarh, India. The fresh meat of male goat was used for rearing of larvae. The effect of temperature and relative humidity on the larval developmental time of this fly in two seasons, Rainy and Summer were studied in normal condition. Statistical analysis of variance was performed and standard significance level of P&lt;0.05 was taken as standard. Results: The results of this study shown that in Rainy season it was completed in 264 h (11 days) when the average temperature ranged from 21.8°C to 24.5°C and the average humidity ranged from 79.5% to 95.5% where as in Summer it was completed in 528 hrs (22 days), when the temperature ranged from 26.5°C to 35.1°C and the humidity ranged from 34% to 67.5%. The P value was found to be P&lt;&lt;.05 in Temperature variation; andP&lt;&lt;0.05 in Humidity variation in different stages(1st instar larvae, 2nd instar larvae, 3rd instar larvae, Prepupae, Pupae and Adult). Conclusion: In the present study we have found that fluctuating temperature and relative humidity of outer condition in two seasons, Rainy and Summer effect the life cycle duration of the fly from the larvi position up to adult eclosion and statistical analysis has proved it to significant rejecting null hypothesis. This data can be further used in the estimation of Post Mortem Interval (PMI) in Homicide and Suspicious cases of both human and wild life poaching death cases.

Sexual activity and climatic adaptation assessment of West African Dwarf goats introduced into Algeria

This study aimed to highlight the effects of variations in age, seasons and climatic conditions on the reproductive activity of West African Dwarf Goats imported from tropical zones in Algeria, and to verify the degree of their adaptation to Mediterranean climatic conditions. For this purpose, testicular biometry and hormonal analysis (testosterone and LH levels) using the radioimmunological method were carried out monthly. In total, seven goats aged between 18 to 48+ months were surveyed during the period from September 2021 to March 2022. The results showed a considerable effect of age on testicular measurements. Bucks less than 18 months recorded the lowest average testicular length, width, thickness and volume, scrotal width and circumference, as levels of testosterone concentrations. All variables were strong correlated. Seasonal variations in the average testicular measurements and hormonal concentrations were observed, without affecting testicular activity. Apart from thenegative action of ambient temperature, no effects of relative humidity or atmospheric pressure were revealed. West African Dwarf Goats showed a good capacity to adapt to Mediterranean climatic conditions through their continuous testicular activity during the year.

Effects of temperature, relative humidity and soil organic carbon content on soil-air partitioning coefficients of volatile PFAS

Soil-air partitioning coefficient (KSA) values are often used to assess the environmental fate of organic contaminants in soil. Till now, sufficient KSA values have not yet been measured for many compounds of interest, including some emerging pollutants such as volatile PFAS. Moreover, the effects of environmental factors such as temperature, relative humidity and soil organic carbon content on KSA of volatile PFAS are also unclear. In this study, the KSA values of target volatile PFAS were measured under various temperature (20–40 °C), relative humidity (30–100 %) and soil organic carbon content (2.1 %–8.0 %) using a modified solid-phase fugacity meter. The results showed that higher temperatures, higher relative humidity and lower organic carbon content in soil may accelerate the diffusion of target volatile PFAS. Furthermore, the KSA measurements were used to derive a multiple linear regression model to depict the relationship between logKSA and temperature, relative humidity, soil organic carbon content and PFAS-specific logKOA. When compared with the predictions obtained from semi-empirical model, we argued that the multiple linear regression model is more robust and easier to implement for target volatile PFAS or other emerging volatile PFAS than the semi-empirical approach to help depict the diffusion process at target volatile PFAS contaminated sites.

Study on the Effects of Temperature and Relative Humidity on the Hygroscopic Properties of Palm Leaf Manuscripts

Study on the Effects of Temperature and Relative Humidity on the Hygroscopic Properties of Palm Leaf Manuscripts

Dependence of aerosol-borne influenza A virus infectivity on relative humidity and aerosol composition.

We describe a novel biosafety aerosol chamber equipped with state-of-the-art instrumentation for bubble-bursting aerosol generation, size distribution measurement, and condensation-growth collection to minimize sampling artifacts when measuring virus infectivity in aerosol particles. Using this facility, we investigated the effect of relative humidity (RH) in very clean air without trace gases (except ∼400 ppm CO2) on the preservation of influenza A virus (IAV) infectivity in saline aerosol particles. We characterized infectivity in terms of 99%-inactivation time, t 99, a metric we consider most relevant to airborne virus transmission. The viruses remained infectious for a long time, namely t 99 > 5 h, if RH < 30% and the particles effloresced. Under intermediate conditions of humidity (40% < RH < 70%), the loss of infectivity was the most rapid (t 99 ≈ 15-20 min, and up to t 99 ≈ 35 min at 95% RH). This is more than an order of magnitude faster than suggested by many previous studies of aerosol-borne IAV, possibly due to the use of matrices containing organic molecules, such as proteins, with protective effects for the virus. We tested this hypothesis by adding sucrose to our aerosolization medium and, indeed, observed protection of IAV at intermediate RH (55%). Interestingly, the t 99 of our measurements are also systematically lower than those in 1-μL droplet measurements of organic-free saline solutions, which cannot be explained by particle size effects alone.