El Niño-Southern Oscillation affects the species-level temporal variation in seed and leaf fall in a mixed temperate forest

El Niño-Southern Oscillation (ENSO), the variation between anomalously cold (La Niña) and warm conditions (El Niño), is one of the most prominent large-scale climate patterns with worldwide effects. Elevated seed and leaf fall has been found at the positive phase of ENSO (El Niño) in tropical forests. However, how seed and leaf fall respond to ENSO at species level is understudied, especially in temperate forests. In this study, we monitored seed and leaf fall at the species-level at 150 points across a 25-ha temperate forest in northeastern China over a span of 12 years. Using time series and wavelet analyses, we assessed three hypotheses: 1) temperate tree species' seed and leaf fall are strongly, but differently, correlated with ENSO and, 2) community synchrony in seed and leaf occurred both at seasonal and ENSO scales; finally, 3) local climatic modulated the effects of ENSO on seed and leaf fall. We found that ENSO was significantly correlated with seed and leaf fall of all species, although correlation strength varied across species (r = 0.206-0.658). Specifically, ENSO indices (ENSO12 or ENSO34) accounted for the most variation in seed and leaf fall of Acer pseudo-sieboldianum (40 % and 34 %, respectively) and ranged 4 %-31 % in all other species. Leaf fall was synchronous with ENSO cycles with a period of 2-7 years, but community synchrony of seed fall was only detected at seasonal scales. ENSO influenced seed fall of Fraxinus mandshurica and Tilla amurensis by mediating rainfall and relative humidity, respectively, highlighting the interactive effects of local climate and ENSO. Our findings highlight the potential effects of ENSO on ecosystems outside of tropical regions and improve our ability to predict regeneration dynamics and nutrient cycling of temperate forests under the context of global change.

Incorporation and improvement of a heterogeneous chemistry mechanism in the atmospheric chemistry model GRAPES_Meso5.1/CUACE and its impacts on secondary inorganic aerosol and PM2.5 simulations in Middle-Eastern China

Heterogeneous chemistry is considered one of the critical pathways of secondary inorganic aerosol (SIA) productions. In this study, a heterogeneous chemistry mechanism is incorporated into the atmospheric chemistry model GRAPES_Meso5.1/CUACE. Varying uptake coefficient schemes of SO₂ and NO₂ are compared and the equivalent ratio of inorganic aerosol (ER)-dependent scheme for SO₂ and relative humidity (RH)/ER-dependent scheme for NO₂ are used to form the improved heterogeneous chemistry. Focusing on a severe haze episode in Middle-Eastern China, the impacts of heterogeneous mechanism on SIA and PM_2.5 composition are investigated based on the updated model. Study results show that the differences in RH or ER uptake coefficients result in obvious differences in sulfate and nitrate concentrations, especially during the severe pollution period, because the ER schemes restrict the excessive production of sulfate and nitrate under high RH effectively by including the self-limitation of heterogeneous reactions, which shows better performance in capturing the magnitude and temporal variations of surface SIA and PM_2.5. Normalized mean bias of sulfate, nitrate, ammonium, and PM_2.5 in megacity Beijing decreases from -27.0, -28.3, -58.2, and -26.3 to 1.0, -2.2, -47.2, and -16.5 %, respectively. And the fractions of sulfate, nitrate, ammonium, and organics during the polluted period change from 13.7, 19.3, 6.9, and 60.1 to 16.5, 23.0, 7.6, and 52.9 %, respectively, which is more consistent with the observation (16.0, 23.2, 14.1, and 46.7 %). SIA and PM_2.5 simulations in another megacity Shanghai have the similar improvements. The modeled SIA by heterogeneous processes contributes 11.7 % of total PM_2.5 in Beijing and 22.5 % in Shanghai. That is 13.5 % in the Chinese megalopolis Beijing-Tianjin-Hebei and 19.8 % in Yangtze-River-Delta, indicating a considerable contribution of heterogeneous pathways to haze pollution. This work indicates the importance of detailed and reasonable heterogeneous schemes for better SIA and haze/fog prediction in the atmospheric chemistry model.

Distribution of droplets/droplet nuclei from coughing and breathing of patients with different postures in a hospital isolation ward

Suspected and confirmed cases of infectious diseases such as COVID-19 are diagnosed and treated in specific hospital isolation wards, posing a challenge to preventing cross-infection between patients and healthcare workers. In this study, the Euler-Lagrange method was used to simulate the evaporation and dispersion of droplets with full-size distribution produced by fluctuating coughing and breathing activities in an isolation ward. The effects of supply air temperature and relative humidity, ventilation rates and patient postures on droplet distribution were investigated. The numerical models were validated by an aerosol experiment with an artificial saliva solution containing E. coli bacteria conducted in a typical isolation ward. The results showed that the small size group of droplets (initial size ≤87.5 μm) exhibited airborne transmission in the isolation ward, while the large size group (initial size ≥112.5 μm) were rapidly deposited by gravitational effects. The ventilation rate had a greater effect on the diffusion of droplet nuclei than the supply air temperature and relative humidity. As the air changes per hour (ACH) increased from 8 to 16, the number fraction of suspended droplet nuclei reduced by 14.2% and 6.4% in the lying and sitting cases, respectively, while the number fraction of escaped droplet nuclei increased by 16.2% and 14.6%. Regardless of whether the patient was lying or sitting, the amount of droplet nuclei deposited on the ceiling was highest at lower ventilation rates. These results may provide some guidance for routine disinfection and ventilation strategies in hospital isolation wards.

Relationship between meteorological factors and mortality from respiratory diseases in a subtropical humid region along the Yangtze River in China

As the health impacts of climate change take on a more serious form, this study for the first time investigates the effect of meteorological factors on the risk of death from respiratory diseases (RD) in Wuhu, a representative city along the Yangtze River in subtropical humid region. Daily meteorological element data and RD deaths in Wuhu City were collected from 2014 to 2020. Time series analysis was conducted using distributed lagged nonlinear model (DLNM) combined with generalized additive model (GAM), and stratified by age and gender. In 7 years, a total of 8016 RD death cases were collected in Wuhu, China. The results demonstrated that the maximum impacts of short-term exposure to exceedingly low temperatures mean (Tmean) were at lag 9, with the maximum relative risk (RR) of 1.044 (lag 1, 95% CI: 1.001, 1.098). The risk of exceedingly high Tmean reached its maximum at lag 0 (RR = 1.070, 95% CI: 1.018, 1.125). Low relative humidity (RH) was negatively associated with the risk of RD death, with the lowest RR values occurring at lag 12 (RR = 0.987, 95% CI: 0.975, 0.999). No significant correlation was found for diurnal temperature range (DTR). Stratified analysis showed that Tmean exposure remained statistically significant for male, female and elderly, while RH and DTR only seemed to increase the mortality risk in the young. In a word, short-term exposure to extreme temperatures may increase the RD mortality risk in the population, and young people needed to be aware that exposure to exceedingly high RH and DTR also increased the risk.

Moisture Sorption by Polymeric Excipients Commonly Used in Amorphous Solid Dispersions and its Effect on Glass Transition Temperature: II. Cellulosic Polymers

Moisture sorption by polymeric carriers used for the development of amorphous solid dispersions (ASDs) plays a critical role in the physical stability of dispersed drugs since moisture may decrease glass transition temperature (T_g) and thereby increase molecular mobility of drugs leading to their crystallization. To assist the selection of appropriate polymers for ASDs, we conducted moisture sorption by five types of cellulosic polymers, namely, hydroxypropyl cellulose (HPC), hydroxypropyl methyl cellulose (HPMC), hydroxypropyl methyl cellulose acetate succinate (HPMCAS), hydroxypropyl methyl cellulose phthalate (HPMCP), and ethyl cellulose (EC), as functions of relative humidity (10 to 90% RH) and temperature (25 and 40 °C). The moisture sorption was in the order of HPC>HPMC>HPMCP>HPMCAS>EC, and there was no significant effect of the molecular weights of polymers on moisture uptake. There was also less moisture sorption at 40 °C than that at 25 °C. Glass transition temperatures (T_g) of the polymers decreased with the increase in moisture content. However, the plasticizing effect by moisture on HPC could not be determined fully since, despite being amorphous, there were very little baseline shifts in DSC scans. There was also very shallow baseline shift for HPMC at >1% moisture content. In contrast, T_g of HPMCAS and HPMCP decreased in general agreement with the Gordon-Taylor/Kelley-Bueche equation, and EC was semicrystalline having both T_g and melting endotherm, with only minor effect of moisture on T_g. The results of the present investigation would lead to a systematic selection of polymeric carriers for ASDs.

Climate-mediated air pollution associated with COPD severity

Air pollution has been reported to be associated with chronic obstructive pulmonary disease (COPD). Our study aim was to examine the mediating effects of air pollution on climate-associated health outcomes of COPD patients. A cross-sectional study of 117 COPD patients was conducted in a hospital in Taiwan. We measured the lung function, 6-min walking distance, oxygen desaturation, white blood cell count, and percent emphysema (low attenuation area, LAA) and linked these to 0-1-, 0-3-, and 0-5-year lags of individual-level exposure to relative humidity (RH), temperature, and air pollution. Linear regression models were conducted to examine associations of temperature, RH, and air pollution with severity of health outcomes. A mediation analysis was conducted to examine the mediating effects of air pollution on the associations of RH and temperature with health outcomes. We observed that a 1 % increase in the RH was associated with increases in forced expiratory volume in 1 s (FEV₁), eosinophils, and lymphocytes, and a decrease in the total-lobe LAA. A 1 °C increase in temperature was associated with decreases in oxygen desaturation, and right-, left-, and upper-lobe LAA values. Also, a 1 μg/m³ increase in PM_2.5 was associated with a decrease in the FEV₁ and an increase in oxygen desaturation. A 1 μg/m³ increases in PM₁₀ and PM_2.5 was associated with increases in the total-, right-, left, upper-, and lower-lobe (PM_2.5 only) LAA. A one part per billion increase in NO₂ was associated with a decrease in the FEV₁ and an increase in the upper-lobe LAA. Next, we found that NO₂ fully mediated the association between RH and FEV₁. We found PM_2.5 fully mediated associations of temperature with oxygen saturation and total-, right-, left-, and upper-lobe LAA. In conclusion, climate-mediated air pollution increased the risk of decreasing FEV₁ and oxygen saturation and increasing emphysema severity among COPD patients. Climate change-related air pollution is an important public health issue, especially with regards to respiratory disease.

Formation of extremely low-volatility organic compounds from styrene ozonolysis: Implication for nucleation

Styrene is a highly reactive compound with the dual nature of aromatics and olefins. This work presents evidence for formation of extremely low-volatility organic compounds (ELVOCs) from styrene ozonolysis. The molecules of ELVOCs were analyzed using a high-resolution orbitrap mass spectrometer. The results show that ELVOCs were oligomers characterized by stabilized Criegee radicals (SCIs) as chain units. The addition of C₆H₅CHOO (SCI1) or CH₂OO (SCI2) can dramatically decrease the oligomers' volatility. At low relative humidity (RH), ELVOCs are mainly formed from the reaction of RO₂ radical, C₆H₅OO·, with SCI1 and SCI2; however, ELVOCs are primarily produced by the reaction between benzoic acid and SCI1 at high RH. Ambient particles were also collected to propose the probable oligomers from styrene-SCI. Our results suggest that styrene-SCI derived ELVOCs may act as nucleating agents, potentially providing an experimental basis for nucleation events that frequently occur in urban areas.

Aerosol liquid water content of PM2.5 and its influencing factors in Beijing, China

Aerosol liquid water content (ALWC) has important influences on atmospheric radiation and aerosol chemical processes. In this work, the changes in ALWC of PM_2.5 were investigated over four seasons based on hourly monitoring of inorganic water-soluble ions and their gaseous precursors using the thermodynamic model ISORROPIA II. The results showed that the ALWC concentrations exhibited pronounced seasonal (autumn > summer > spring > winter) and diurnal variation characteristics. The sensitivity tests indicated that ALWC depended strongly on TSO₄ (total sulfate (gas and aerosols) expressed as equivalent H₂SO₄), followed by TNO₃ (total nitrate (gas and aerosols) expressed as equivalent HNO₃). The relatively low concentration of TCl (total chloride (gas and aerosols) expressed as equivalent HCl) limit its importance in the atmosphere. ALWC showed exponential growth features as a function RH in all four seasons. RH became the most influential factor on the variation of ALWC when RH exceeded 80% in all seasons. The seasonal average data showed that the ALWC increased from 2.92 μg·m^-3 to 75.83 μg·m^-3 when ambient RH increased from 30% to 90%, the associated sulfate, nitrate, and ammonium (abbreviated as SNA) mass fraction in PM_2.5 rose from 0.39 to 0.58 in the atmosphere. The ALWC facilitated the formation of SNA through gas-particle conversion and partitioning. The self-amplifying processes between ALWC and SNA enhanced aerosol formation. By modeling ALWC under different seasonal atmospheric scenarios, it was found that reductions in chemical species could reduce ALWC concentrations in different degrees. Based on the current emission conditions, controlling excess NH₃ emission could effectively reduce ALWC to a maximum of 45.71% in summer, indicating that NH₃ control was crucial for reducing ALWC and PM_2.5 concentrations under high levels of SO₄^2- and NO₃^-.

Contributions of ambient temperature and relative humidity to the risk of tuberculosis admissions: A multicity study in Central China

BACKGROUND

As a communicable disease and major public health issue, many studies have quantified the associations between tuberculosis (TB) and meteorological factors with inconsistent results. The purpose of this multicenter study was to characterize the associations between ambient temperature, humidity and the risk of TB hospitalizations and to investigate potential heterogeneity.

METHOD

Data on daily hospitalizations for TB, meteorological factors and ambient air pollutants for 16 cities in Anhui Province were collected from 2015 to 2020. A distributed lag nonlinear model (DLNM) was performed to obtain the estimates of meteorological-TB relationships by cities. Then, we used the multivariate meta-regression model to pool the city-specific estimates with air pollution, demographic indicators, medical resource and latitude as potential modifiers to explore the sources of heterogeneity. Finally, we divided the whole province into three regions to validate the meteorological-TB relationships by regions.

RESULTS

The overall pooled temperature-TB association presented an approximate S-shaped curve, with relative risk (RR) peaking at 5 °C (RR = 1.536, 95% CI: 1.303-1.811) compared to the reference temperature (27 °C). Lag-response curve suggested that low temperature exposure increased the risk of TB hospitalizations at lag 0 and 1 day (lag0 day: RR = 1.136, 95% CI: 1.048-1.231, lag1 day: RR = 1.052, 95% CI: 1.023-1.082). However, the overall exposure-response curve between relative humidity and TB showed almost horizontal line with reference relative humidity to 78%. The residual heterogeneity ranged from 27.1% to 36.9%, with air pollution, latitude and medical resource explained the largest proportion.

CONCLUSION

We found that low temperature exposure is associated with an acute increased risk of TB hospitalizations in Anhui Province. The association between temperature and TB admission varies depending on air pollution, latitude, and medical resources. Since the effect of short-term exposure to humidity is not significant, further studies are supposed to focus on the long-term effect of humidity.

Influence of meteorological parameters and oxidizing capacity on characteristics of airborne particulate amines in an urban area of the Pearl River Delta, China

Nine amine species in atmospheric particles during haze and low-pollution days with low and high relative humidity (RH) were analyzed in urban Guangzhou, China. The mean concentrations of total measured amines (Ʃamines) in fine particles were 208 ± 127, 63.7 ± 21.3, and 120 ± 20.1 ng m^-3 during haze, low pollution-low RH (LP-LRH), and low pollution-high RH (LP-HRH) episodes, respectively. The dominant amine species were methylamine (MA), dimethylamine (DMA), diethylamine (DEA) and dibutylamine (DBA), which in total accounted for 82-91% of the Ʃamines during different pollution episodes. The contributions of Ʃamines-C to water-soluble organic carbon (WSOC) and Ʃamines-N to water-soluble organic nitrogen (WSON) were 1.52% and 2.49% during haze, 1.24% and 1.96% during LP-LRH, and 2.00 and 2.98% during LP-HRH days, respectively. The mass proportion of Ʃamines in fine particles was higher during LP-HRH periods (0.19%) than during haze and LP-LRH periods (0.16%). The mass proportion of DBA in Ʃamines increased from 7% during haze and LP-LRH episodes to 25% during LP-HRH episodes. Compared with other amines, DBA showed a stronger linear relationship with RH (r = 0.867, p < 0.01), which demonstrates its high sensitivity to high RH conditions. Meteorological parameters (including RH, the mixed layer depth, wind speed and temperature), the oxidizing capacity (ozone concentration), and gaseous pollutants (NO_x and SO₂) correlated with amines under different pollution conditions. Under high RH, acid-base reactions were the dominant pathway for the gas-to-particle distribution of amines in urban areas, while direct dissolution dominated in the background site. To our knowledge, this study is the first attempt to conduct in situ measurements of particulate amines during different pollution conditions in China, and further research is needed to in-depth understanding of the influence of amines on haze formation.

Lagged meteorological impacts on COVID-19 incidence among high-risk counties in the United States-a spatiotemporal analysis

BACKGROUND

The associations between meteorological factors and coronavirus disease 2019 (COVID-19) have been discussed globally; however, because of short study periods, the lack of considering lagged effects, and different study areas, results from the literature were diverse and even contradictory.

OBJECTIVE

The primary purpose of this study is to conduct more reliable research to evaluate the lagged meteorological impacts on COVID-19 incidence by considering a relatively long study period and diversified high-risk areas in the United States.

METHODS

This study adopted the distributed lagged nonlinear model with a spatial function to analyze COVID-19 incidence predicted by multiple meteorological measures from March to October of 2020 across 203 high-risk counties in the United States. The estimated spatial function was further smoothed within the entire continental United States by the biharmonic spline interpolation.

RESULTS

Our findings suggest that the maximum temperature, minimum relative humidity, and precipitation were the best meteorological predictors. Most significantly positive associations were found from 3 to 11 lagged days in lower levels of each selected meteorological factor. In particular, a significantly positive association appeared in minimum relative humidity higher than 88.36% at 5-day lag. The spatial analysis also shows excessive risks in the north-central United States.

SIGNIFICANCE

The research findings can contribute to the implementation of early warning surveillance of COVID-19 by using weather forecasting for up to two weeks in high-risk counties.

Identifying joint impacts of sun radiation, temperature, humidity, and rain duration on triggering mental disorders using a high-resolution weather monitoring system

BACKGROUND

Mental disorders (MDs) are behavioral or mental patterns that cause significant distress or impairment of personal functioning. Previously, temperature has been linked to MDs, but most studies suffered from exposure misclassification due to limited monitoring sites. We aimed to assess whether multiple meteorological factors could jointly trigger MD-related emergency department (ED) visits in warm season, using a highly dense weather monitoring system.

METHODS

We conducted a time-stratified, case-crossover study. MDs-related ED visits (primary diagnosis) from May-October 2017-2018 were obtained from New York State (NYS) discharge database. We obtained solar radiation (SR), relative humidity (RH), temperature, heat index (HI), and rainfall from Mesonet, a real-time monitoring system spaced about 17 miles (126 stations) across NYS. We used conditional logistic regression to assess the weather-MD associations.

RESULTS

For each interquartile range (IQR) increase, both SR (excess risk (ER): 4.9%, 95% CI: 3.2-6.7%) and RH (ER: 4.0%, 95% CI: 2.6-5.4%) showed the largest risk for MD-related ED visits at lag 0-9 days. While temperature presented a short-term risk (highest ER at lag 0-2 days: 3.7%, 95% CI: 2.5-4.9%), HI increased risk over a two-week period (ER range: 3.7-4.5%), and rainfall hours showed an inverse association with MDs (ER: -0.5%, 95% CI: 0.9-(-0.1)%). Additionally, we observed stronger association of SR, RH, temperature, and HI in September and October. Combination of high SR, RH, and temperature displayed the largest increase in MDs (ER: 7.49%, 95% CI: 3.95-11.15%). The weather-MD association was stronger for psychoactive substance usage, mood disorders, adult behavior disorders, males, Hispanics, African Americans, individuals aged 46-65, or Medicare patients.

CONCLUSIONS

Hot and humid weather, especially the joint effect of high sun radiation, temperature and relative humidity showed the highest risk of MD diseases. We found stronger weather-MD associations in summer transitional months, males, and minority groups. These findings also need further confirmation.

Historical seasonal changes in prescribed burn windows in California

Prescribed (Rx) burns are conducted on days when the meteorological thresholds of maximum air temperature, relative humidity, and wind speeds are all met (burn window) in order to ensure safe Rx burn practices. Limited burn windows have been consistently identified as one of the most important constraints for conducting Rx burns in California. We investigate whether burn windows across California can be extended from the typical fall season to include other opportune seasons for facilitating specific management objectives. We quantify the seasonal Rx burn efficiencies by assessing the frequency and burned areas using an aggregate of Rx datasets, and we compute the seasonal spatiotemporal trends in the number of days the set of meteorological parameters are met over thirty-five years (1984 to 2019), using the gridMET 4 km dataset. Our results indicate that while fall burns are most frequently executed (40% of the time), the spring (and to a lesser extent winter) seasons yield efficient Rx burns similar to fall because greater acres are being consumed with less burns. In addition, winter and spring seasons experience burn window opportunities (70-90% of the time) over larger areas than the other seasons, and this is predominantly over forested regions in Northern California. Our results also indicate that burn windows in the winter and spring are decreasing at a rate of one day per year over a larger spatial area than that of summer and fall. This decrease is primarily driven by changes in the number of days the relative humidity thresholds are met. Policymakers recognize the critical importance that Rx burns have on a multitude of ecosystem restoration factors, fire behavior dynamics, and firefighter safety. Therefore, there is a need to capitalize on these additional burn windows before these opportunities become less feasible in the future.

Temporal dynamics of negative air ion concentration and its relationship with environmental factors: Results from long-term on-site monitoring

Negative air ions (NAIs) play an important role in evaluating forest health effects and promoting human physical and mental health. In this paper, long-term on-site monitoring of NAI concentration, air temperature, and relative humidity was conducted in real time over 24 h, from July 2019 to March 2021, to explore the temporal dynamic patterns of NAIs. We found that the daily dynamics of NAI concentration showed a bimodal curve. The peak concentrations usually occurred in the early morning (5:00-7:00) and afternoon (15:00-17:00), and the lowest concentrations usually occurred at noon (11:00-13:00). At the monthly scale, NAI concentrations were relatively high in February and August and low in May and December, and at the seasonal scale, NAI concentration was significantly higher in summer than in other seasons. Autumn had the second highest NAI concentration. There was no significant difference in NAI concentration between winter and spring. A comprehensive analysis shows that the AQI was the most key factor affecting NAI concentrations compared to temperature and relative humidity, especially the two indicators of particulate matter and ozone, and that NAI concentration had a negative correlation with these indicators and was significantly higher under favorable air quality conditions than under polluted air conditions. NAI concentrations and air temperature showed marked piecewise characteristics, with NAIs increasing linearly with rising temperature only if the Ta was separated into three ranges of -5 °C-10 °C, 10 °C-30 °C, and 30 °C-40 °C. With rising relative humidity, NAI concentration increased in accordance with a quadratic function. Our research provides new insights into the NAI temporal dynamics patterns and its driving factors, and will aid in scheduling outdoor recreation and forest health activities for urban people.

Modeling the Growth of Salmonella on Sliced Cucumbers as a Function of Temperature and Relative Humidity

ABSTRACT

Recent multistate outbreaks of salmonellosis linked to fresh cucumbers underscore the importance of understanding Salmonella behavior on cucumbers under different storage conditions. No validated models that describe the impact of environmental factors on the growth of Salmonella on sliced cucumbers currently exist. This study developed mathematical models to predict the growth of Salmonella on sliced cucumbers at different temperature and relative humidity (RH) conditions. Sliced cucumbers were inoculated with a four-strain cocktail of Salmonella and placed in desiccators containing a saturated salt solution to create controlled RH environments (∼15, 50, and 100% RH) at 7, 14, and 21°C for up to 120 h. Predictive models were developed by using the Baranyi and Roberts equation as a primary model, and estimated kinetic parameters were fitted into a square root (or Ratkowsky) equation for secondary models. The maximum growth rates for Salmonella on sliced cucumbers depended on temperature but not RH. The square root model for Salmonella growth was √μ= 0.0297 × (T - 6.5185), with a high R2 value (0.98). The models in this study will be useful for future microbial risk assessments and predictions of Salmonella behavior in the cucumbers to manage the risk of Salmonella on sliced cucumbers.

HIGHLIGHTS

Effects of environmental parameters and their interactions on the spreading of SARS-CoV-2 in North Italy under different social restrictions. A new approach based on multivariate analysis

In 2020 North Italy suffered the SARS-CoV-2-related pandemic with a high number of deaths and hospitalization. The effect of atmospheric parameters on the amount of hospital admissions (temperature, solar radiation, particulate matter, relative humidity and wind speed) is studied through about 8 months (May-December). Two periods are considered depending on different conditions: a) low incidence of COVID-19 and very few regulations concerning personal mobility and protection ("free/summer period"); b) increasing incidence of disease, social restrictions and use of personal protections ("confined/autumn period"). The "hospitalized people in medical area wards/100000 residents" was used as a reliable measure of COVID-19 spreading and load on the sanitary system. We developed a chemometric approach (multiple linear regression analysis) using the daily incidence of hospitalizations as a function of the single independent variables and of their products (interactions). Eight administrative domains were considered (altogether 26 million inhabitants) to account for relatively homogeneous territorial and social conditions. The obtained models very significantly match the daily variation of hospitalizations, during the two periods. Under the confined/autumn period, the effect of non-pharmacologic measures (social distances, personal protection, etc.) possibly attenuates the virus diffusion despite environmental factors. On the contrary, in the free/summer conditions the effects of atmospheric parameters are very significant through all the areas. Particulate matter matches the growth of hospitalizations in areas with low chronic particulate pollution. Fewer hospitalizations strongly correspond to higher temperature and solar radiation. Relative humidity plays the same role, but with a lesser extent. The interaction between solar radiation and high temperature is also highly significant and represents surprising evidence. The solar radiation alone and combined with high temperature exert an anti-SARS-CoV-2 effect, via both the direct inactivation of virions and the stimulation of vitamin D synthesis, improving immune system function.

Epidemiologic Correlation and Drug Resistance Analysis of Pathogenic Bacteria in Different Open Limb Injury External Conditions

Objective

To study the epidemiological correlation and drug resistance of external factors of infection caused by open injury of limbs to pathogens.

Methods

This experiment is a retrospective study. We took the geographical location and climate of Nanchang, Jiangxi Province, China as the background, analyzed 2017 strains of pathogens from 1589 patients with limb trauma infection in a University Affiliated Hospital from 2012 to 2017. Patients were divided into three groups according to the type of incision: I, In‐hospital infection of clean limb incision, II, In‐hospital infection with open injury, III, Community infection with open injury of the limb. Groups II and Groups III were divided into six subgroups according to the causes of trauma, including: accidents from non‐motor vehicles, machinery, cutting/piercing, pedestrian injuries, struck by/against, pedal cycles, and other injuries. We found eight common pathogens of orthopedic infection, which were mainly divided into Gram‐positive bacteria (G+, mainly including Staphylococcus) and Gram‐negative bacteria (G‐, mainly Enterobacteriaceae). The relationship between main pathogens and damage mechanism, apparent temperature and relative humidity was discussed in this study. SPSS v22.0 was used for statistical analysis of the data. Friedman's two‐way ANOVA was used to analyze the difference between the injury mechanism and incidence of pathogenic bacteria. Linear regression was used to determine the trend between the incidence of major pathogens and seasonal temperature and humidity. The level of significance was set as P < 0.05.

Results

There was no significant difference in the distribution of pathogens between Groups II and Groups III (P>0.05). The drug resistance of Groups III was significantly higher than that of Groups II and Groups I. G+ bacteria were resistant to cephalosporin, ceftriaxone and other cephalosporins and erythromycin and other macrolides. They were sensitive to vancomycin and linezolid. G‐ were resistant to the first‐ and the second‐generation cephalosporins, including cefotetan and cefazolin, and ampicillin and other penicillins, while they were sensitive to third‐generation cephalosporins, such as ceftazidime, as well as to levofloxacin and other quinolones, meropenem, and other beta‐lactamases. The correlation between the injury mechanism and infection of pathogenic bacteria was not significant. The monthly average apparent temperature and relative humidity were correlated with the infection rate of pathogenic bacteria.

Conclusion

In open injury of extremities, apparent temperature and relative humidity is an important risk factor for infection by pathogenic bacteria and the drug resistance of pathogenic bacteria in out‐of‐hospital infection was lower than that of hospital infection.

A natural environmental chamber study on the emissions and fate of organophosphate esters in the indoor environment

In this study, we investigated the emission and fate of 9 organophosphate esters (OPEs) from a natural environment chamber, in which three environment matrices (i.e., air, dust, and window film samples) as well as three decoration materials (i.e., laminate flooring, latex paint, and nonwoven paper) were collected within gradient variation of room temperature and relative humidity. ΣAlkyl-OPEs and ΣCl-OPEs were the predominant classes in the three environment matrices, accounting - on average - for 98.7%, 99.8% and 99.3% of ΣOPEs in indoor dust, air and window film, respectively. TBOEP was the most abundant OPE in air, dust, and laminate flooring, respectively, while tris (2-chloro-isopropyl) phosphate (TCIPP) and tris (1,3-dichloro-2-propyl) phosphate (TDCIPP) in nonwoven paper and latex paint, respectively. The results showed that higher room temperature expedited the emission of OPEs to indoor air. However, the room temperature and relative humidity had no effect on the levels of OPEs in dust. The OPEs equilibrium time in indoor environment may be dependent on room temperature and relative humidity. The area specific emission rates (SERs) of the three materials were calculated, and an optimal expression based on the concept of mass balance model was constructed, preliminarily revealing a general relationship between OPEs source and sink effects in indoor environment.

Conservation risks for paper collections induced by the microclimate in the repository of the Alessandrina Library in Rome (Italy)

The Alessandrina Library was founded in 1667 by pope Alexander VII Chigi and is nowadays housed in the Campus of Sapienza University of Rome (Italy). Within its Ancient (mostly made of rag paper) and Modern (mostly made of contemporary paper) collections, it includes more than one million books produced from the XVI to the XXI century. In 2019, six thermo-hygrometers were deployed in its multi-storey repository to monitor temperature (T) and relative humidity (RH). Hourly T and RH data collected over 2 years allowed us to evaluate spatial and temporal thermo-hygrometric distributions and to carry out a comprehensive assessment of the climate-induced risks (mechanical, chemical, and biological deterioration mechanisms). Vertical temperature gradients associated with unstable conditions occurred in winter, resulting in upraising air flows up to the ceiling. The risky short-term RH fluctuations (EN 15757:2010) were determined to avoid mechanical stress in case of loans, relocation, and consultation. The Time Weighted Expected Lifetime (TWEL) index was used to evaluate the chemical risk for different paper-based collections as a function of their acidity and degree of polymerisation, also considering the typical response time of paper books to T and RH changes. The TWEL calculation estimated that the durability of acidic paper was around 300 years and highlighted that rag paper could be subject to cellulose hydrolysis only in summer and autumn, while contemporary paper was mostly at no risk. The risk of mould germination (Sedlbauer diagram) was possible on few days in Autumn, while the production of insect eggs (Brimblecombe empirical function) was favoured during approximately 42% of time over the year. In addition, illuminance and colorimetric measurements (performed on selected book covers) showed that light-sensitive objects could be exposed to the photodeterioration risk in the east-facing side of the repository. Although the investigation focussed on a specific case study, a similar approach could be effectively adapted to most library and archival repositories conserving paper-based collections.

Association between meteorological factors and hospital admissions for uveitis in Hefei, China: a time-series study

Meteorological variables are regarded as risk factors for inflammatory diseases, but their associations with uveitis, one of the leading causes accounting for blindness worldwide with an estimated prevalence of 38-714 cases/100,000 person-years, have not been thoroughly investigated. The present study explored the short-term association between meteorological variables and hospital admissions for uveitis in Hefei City, China. Daily data on uveitis hospital admissions and meteorological variables including mean temperature (MT) (°C), diurnal temperature range (DTR) (°C), and relative humidity (RH) (%), from 2014 to 2020, were collected. A time-series study using generalized linear model combined with distributed lag non-linear model was applied. Totally, 1911 admissions for uveitis including 894 first admissions and 1017 readmissions were reported during the study period. The associations of high percentile of MT (75th, 24.5℃) and low percentile of DTR (25th, 5.4℃) with uveitis admissions were observed to be statistically significant from lag9 (RR = 1.041, 95%CI: 1.002-1.081) to lag11 (RR = 1.053, 95%CI: 1.003-1.104) and lag4 (RR = 1.053, 95%CI: 1.019-1.088) to lag5 (RR = 1.052, 95%CI: 1.020-1.085), respectively. Moreover, a significant association between low percentile of RH (1th, 44%) and uveitis admissions appeared at lag0-8 (RR = 1.869, 95%CI: 1.017-3.434) and lasted until lag0-13 (RR = 2.539, 95%CI: 1.102-5.850) in the cumulative lag structure. Subgroup analyses indicated that males and the young seemed to be more sensitive to high MT exposure, while females appeared to be more vulnerable to low DTR exposure. Interestingly, both the young and the elderly are susceptible to low DTR and low RH exposure. Furthermore, high MT and low DTR exposure were associated with increased risk of first admission for uveitis. In summary, exposure to high-value of MT and low-value of DTR and RH may increase the hospital admissions for uveitis, especially for the status of first admission.

Association between air pollution and outpatient visits for allergic rhinitis: Effect modification by ambient temperature and relative humidity

Mounting evidence indicated the associations between air pollution and outpatient visits for allergic rhinitis (AR), while few studies assessed the effect modification of these associations by ambient temperature and relative humidity (RH). In this study, dataset of AR outpatients was obtained from Chinese People's Liberation Army Strategic Support Force Characteristic Medical Center in Beijing during 2014 to 2019, and the average concentrations of air pollutants including particulate matter ≤2.5 μm in diameter (PM_2.5) and ≤10 μm (PM₁₀), nitrogen dioxide (NO₂), sulfur dioxide (SO₂), and meteorological factors (temperature and RH) at the same period were collected from one nearby air monitoring station. We performed a time-series study with Poisson regression model to examine the effects of air pollutants on AR outpatients after adjustment for potential confounders. And the effects modification analysis was further conducted by stratifying temperature and RH by tertiles into three groups of low, middle and high. In total of 33,599 outpatient visits for AR were recorded during the study period. Results found that a 10 μg/m³ increase in PM_2.5, PM₁₀, NO₂ and SO₂ was associated with significant increases in AR outpatients of 1.24% (95% confidence interval (CI): 0.69%, 1.78%), 0.79% (95% CI: 0.43%, 1.15%), 3.05% (95% CI: 1.72%, 4.40%) and 5.01% (95% CI: 1.18%, 8.96%), respectively. Stronger associations were observed in males than those in females, as well as in young adults (18-44 years) than those in other age groups. Air pollution effects on AR outpatients increased markedly at low temperature (<33.3th percentile) and high RH (>66.7th percentile). Findings in this study indicate that air pollution is associated with increased risk of AR outpatients, and the effects of air pollution on AR could be enhanced at low temperature and high RH.

Short-term effect of meteorological factors on the risk of rheumatoid arthritis hospital admissions: A distributed lag non-linear analysis in Hefei, China

Rheumatoid arthritis (RA) is an autoimmune disease, mainly characterized by erosional arthritis. The proportion of adults suffering from RA is about 0.5%-1%. There have been reports on the association of rainfall and traffic-related air pollutants with RA hospitalization rates. However, there have been no studies on the association of diurnal temperature range (DTR) and relative humidity (RH) with RA hospitalization rates. This study aimed to examine the short-term association of DTR, RH and other meteorological factors with the hospital admission rate of RA patients, while excluding the interference of PM_2.5, SO₂, NO₂, CO and O₃ atmospheric pollutants. We collected daily RA occupancy rate and meteorological factor data in Hefei city from 2015 to 2018 and used the generalized additive model (GAM) combined with the distributed lag nonlinear model (DLNM) for time series analysis, and further stratified analysis by gender and age. Single-day and cumulative-day risk estimates of RA admissions were expressed as relative risk (RR) and its 95% confidence interval (95% CI). For the cumulative-day lag model, high RH was statistically significant after cumulative lag 0-8 days, and the effect gradually increases. Stratified analysis shows that females seem to be more susceptible to high or extremely high DTR and RH exposure, and extremely high DTR exposure may increase the risk of RA admission in all populations. In conclusion, this study found that high DTR and high RH exposure increased the risk of hospitalization in RA patients and provided clues to the potential association between other meteorological factors and RA.

Quantifying the impacts of PM2.5 constituents and relative humidity on visibility impairment in a suburban area of eastern Asia using long-term in-situ measurements

The deterioration of visibility due to air pollutants and relative humidity has been a serious environmental problem in eastern Asia. In most previous studies, chemical compositions of atmospheric particles were provided using filter-based offline analyses, which were unable to provide long-term and in-situ measurements that resolve sufficient temporal variations of air pollution and meteorology, hindering the resolution of the relationship between air quality and visibility. Here, we present a year-long continuously measured data from a comprehensive suite of online instruments to investigate diurnal and seasonal impacts of the aerosol chemical compositions in PM_2.5 on visibility seasonally and diurnally. The measured dry aerosol extinction at λ = 550 nm reached a closure with that predicted by aerosol compositions within 12%. However, the hygroscopic growth of particles under ambient RH could enhance the aerosol extinction by a factor of 2-6, matching the perceptive visibility of the public. Particulate ammonium nitrate was most sensitive to reducing visibility, while ammonium sulfate contributed the most to the light extinction. In spring and winter, the monsoon and stagnant air masses reduced the visibility and increased PM_2.5 (>35 μg m^-3). The moisture was found to substantially enhance the light extinction under RH = 60-90%, reducing visibility by approximately 15 km, largely attributed to hygroscopic inorganic salts. This study serves as a metric to highlight the need to consider the influence of RH, and aqueous reactions in producing secondary inorganic aerosols on atmospheric visibility, underpinning the more accurate mitigation strategies of air pollution.

Forecasting of monthly relative humidity in Delhi, India, using SARIMA and ANN models

Relative humidity plays an important role in climate change and global warming, making it a research area of greater concern in recent decades. The present study attempted to implement seasonal autoregressive moving average (SARIMA) and artificial neural network (ANN) with multilayer perceptron (MLP) models to forecast the monthly relative humidity in Delhi, India during 2017-2025. The average monthly relative humidity data for the period 2000-2016 have been used to carry out the objectives of the proposed study. The forecast trend in relative humidity declines from 2017 to 2025. The accuracy of the models has been measured using root mean squared error (RMSE) and mean absolute error (MAE). The results showed that the SARIMA model provides the forecasted relative humidity with RMSE of 6.04 and MAE of 4.56. On the other hand, MLP model reported the forecasted relative humidity with RMSE of 4.65 and MAE of 3.42. This study concluded that the ANN model was more reliable for predicting relative humidity than SARIMA model.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s40808-022-01385-8.

Effects of environmental conditions on the emission and odor-active compounds from Fraxinus mandshurica Rupr

Being one of the most common wood in furniture and decoration, Fraxinus mandshurica Rupr. (F. mandshurica) is a frequently used material for wood products. However, the resulting odor problem has not yet been solved so far. Thus, this study focused on exploring odor-active compounds and investigating the effect of environmental conditions on emission and odor attributes. F. mandshurica was studied via TD-GC-MS/O combined with microchamber. Totally, 15 kinds of key odor-active compounds were detected from F. mandshurica. The main odorous components were found to be aromatics, aldehydes and ketones, esters, alcohols and acids. Six kinds of attributes played a key role in the overall odor character of F. mandshurica. Fragrant was the predominant odor impressions, followed by vinegar and antiseptic solution. The proportion of the odor-active compounds concentration to total concentration decreased with an increase in the temperature and relative humidity, while the ratio of air exchange rate to the loading factor had little effect on this. The total concentration of F. mandshurica increased as the temperature and relative humidity increased, but these decreased as the ratio of air exchange rate to the loading factor increased, while the total odor intensity reduced with the rise in the ratio of air exchange rate to the loading factor. Time was found to be the most effective factor for eliminating emissions. Considering the environmental conditions in this study, 40 °C, 60% relative humidity and a 1.0 m³·m^-2 h^-1 ratio of air exchange rate to loading factor are recommended to accelerate the emission of F. mandshurica. The optimum condition was found to be higher temperature, higher relative humidity and higher ratio of air exchange rate to loading factor.

Effect of NOx and RH on the secondary organic aerosol formation from toluene photooxidation

The secondary organic aerosol (SOA) formation mechanism and physicochemical properties can highly be influenced by relative humidity (RH) and NOx concentration. In this study, we performed a laboratory investigation of the SOA formation from toluene/OH photooxidation system in the presence or absence of NOx in dry and wet conditions. The chemical composition of toluene-derived SOA was measured using Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). It was found that the mass concentration of toluene decreased with increasing RH and NOx concentration. However, the change of SOA chemistry composition (f₄₄, O/C) with increased RH was not consistent in the condition with or without NOx. The light absorption and mass absorption coefficient (MAC) of the toluene-derived SOA only increased with RH in the presence of NOx. In contrast, MAC is invariant with RH in the absence of NOx. HR-ToF-AMS results showed that, in the presence of NOx, the increased nitro-aromatic compounds and N/C ratio concurrently caused the increase of SOA light absorption and O/C in wet conditions, respectively. The relative intensity of CHON and CHO_xN family to the total nitrogen-containing organic compounds (NOCs) increased with the increasing RH, and be the major components of NOCs in wet condition. This work revealed a synergy effect of NOx and RH on SOA formation from toluene photooxidation.

Ambient temperature, humidity, and urinary system diseases: a population-based study in Western China

Climate has received an increasing attention due to its adverse effects on human health, but the effects on the urinary system are still short of enough evidence. Therefore, we carry out this study to analyze the relationship between meteorological factors and urinary system health in arid areas of western China. In this study, the daily numbers of outpatients with the urinary system diseases from multiple hospitals in three cities in Gansu province (Lanzhou, Zhangye, and Tianshui city) were collected and used for analysis. The distributed lag non-linear models (DLNM) with a quasi-Poisson distribution were used to estimate the associations between meteorological factors and daily outpatients for urinary system diseases in these three cities, and then a multivariate meta-analysis was applied to pool the estimates of city-specific effects. We found that the ambient temperature (AT) and relative humidity (RH) were significantly associated with the outpatient visits of urinary system diseases. The effects of meteorological factors on outpatients with urinary system diseases for both males and females were statistically significant at different lag days. The higher AT and lower RH were associated with the higher risk of urinary system diseases. We also observed substantial lag effects of meteorological factors on outpatients for both males and females. Among all disease types, renal tubule-interstitial diseases had the strongest relationships with meteorological factors. Our results indicate that the higher AT and lower RH may increase the outpatient visits for urinary system diseases, with significant lag effects in semi-arid areas.

Wall losses of oxygenated volatile organic compounds from oxidation of toluene: Effects of chamber volume and relative humidity

Vapor wall losses can affect the yields of secondary organic aerosol. The effects of surface-to-volume (S/V) ratio and relative humidity (RH) on the vapor-wall interactions were investigated in this study. The oxygenated volatile organic compounds (OVOCs) were generated from toluene-H₂O₂ irradiations. The average gas to wall loss rate constant (k_gw) of OVOCs in a 400 L reactor (S/V = 7.5 m^-1) is 2.47 (2.41 under humid conditions) times higher than that in a 5000 L reactor (S/V = 3.6 m^-1) under dry conditions. In contrast, the average desorption rate constant (k_wg) of OVOCs in 400 L reactor is only 1.37 (1.20 under humid conditions) times higher than that in 5000 L reactor under dry conditions. It shows that increasing the S/V ratio can promote the wall losses of OVOCs. By contrast, the RH effect on k_gw is not prominent. The average k_gw value under humid conditions is almost the same as under dry conditions in the 400 L (5000 L) reactor. However, increasing RH can decrease the desorption rates. The average k_wg value under dry conditions is 1.45 (1.27) times higher than that under humid conditions in the 400 L (5000 L) reactor. The high RH can increase the partitioning equilibrium timescales and enhance the wall losses of OVOCs.

Heterogeneous reaction of SO2 on CaCO3 particles: Different impacts of NO2 and acetic acid on the sulfite and sulfate formation

Despite the heterogeneous reaction of sulfur dioxide (SO₂) on mineral dust particles significantly affects the atmospheric environment, the effect of acidic gases on the formation of sulfite and sulfate from this reaction is not particularly clear. In this work, using the in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) technique, we employed a mineral dust particle model (CaCO₃) combined with NO₂ and acetic acid to investigate their effects on the heterogeneous reaction of SO₂ on CaCO₃ particles. It was found that water vapor can promote the formation of sulfite and simulated radiation can facilitate the oxidation of sulfite to sulfate. The addition of NO₂ or acetic acid to the reaction system altered the production of sulfate and sulfite accordingly. There was a synergistic effect between NO₂ and SO₂ that promoted the oxidation of sulfite to sulfate, and a competitive effect between acetic acid and SO₂ that inhibited the formation of sulfite. Moreover, light and water vapor can also affect the heterogeneous reaction of SO₂ with the coexistence of multiple gases. These findings improve our understanding of the effects of organic and inorganic gases and environmental factors on the formation of sulfite and sulfate in heterogeneous reactions.

Moisture sorption by polymeric excipients commonly used in amorphous solid dispersion and its effect on glass transition temperature: I. Polyvinylpyrrolidone and related copolymers

Moisture plays a critical role in the stability of amorphous solid dispersions (ASD) as it can lower the glass transition temperature (T_g) and thereby increase molecular mobility resulting in drug crystallization. A systematic study on moisture sorption by four polyvinylpyrrolidone (PVP) having different molecular weights (Kollidon® 12, 17, 30, and 90) and two related copolymers (Kollidon® VA64; Soluplus®) was conducted at 25 and 40 °C as a function of relative humidity to determine effects of absorbed moisture on T_g and potential stability of ASDs. A VTI dynamic moisture sorption analyzer was used, where experimental conditions were first established such that equilibrium was reached and there was no significant hysteresis loop between sorption and desorption isotherms. The PVPs had identical moisture sorption profiles and were highly hygroscopic, reaching 22-24% and 41-42% w/w moisture at 25 °C/60% RH and 25 °C/80% RH, respectively. Kollidon® VA64 and Soluplus® were relatively less hygroscopic, reaching, respectively, about half and one-fourth the moisture content of PVPs at 25 °C/60% RH. Moisture sorption at 40 °C was relatively lower than that at 25 °C. The high moisture sorption drastically decreased T_g of polymers, which roughly agreed with theoretical calculations based on the Gordon-Taylor/Kelley-Bueche equation, although deviation occurred, possibly due to hydrogen bonding between polymer and moisture.

A single-film fiber optical sensor for simultaneous measurement of carbon dioxide and relative humidity

Colorimetric measurement is a versatile, low-cost method for bio-/chemical sensing and that has importance in biomedical applications. General carbon dioxide (CO₂) sensors based on colorimetric change of a pH indicator report only one parameter at a time and are cross-sensitive to relative humidity (RH). This work describes a novel optical fiber sensor with a thin film on the distal end of the fiber, combining colorimetric measurement and a white light Fabry-Pérot interferometer (FPI) for the simultaneous measurement of CO₂ and RH. The CO₂ sensitive dye ion-pair: thymol blue and tetramethylammonium hydroxide are encapsulated inside organically modified silica forming an extrinsic FPI cavity (refractive index of 1.501 ± 0.02 and thickness of 5.83 ± 0.09 μm). The sensor reversibly responds to 0-6% CO₂ and 0-90% RH with negligible cross-sensitivity and allows measurement of both parameters simultaneously. A sensitivity of ∼0.19 nm/%RH is obtained for RH measurement based on the wavelength shift of the FPI and there is a polynomial correlation between the average intensity of selected wavelengths and the concentration of CO₂. The applicability of the sensor is demonstrated by measuring the CO₂ and RH exhaled from human breath with a percent error of 3.1% and 2.2% respectively compared to a commercial datalogger. A simulation model is provided for the dye-encapsulated FPI sensor allowing simulation of spectra of sensors with different film thicknesses.

Etofenprox as grain protectant for the management of five key stored-product insect pests

Etofenprox is a broad spectrum pyrethroid insecticide with low toxicity to mammals, fishes, and honeybees. In the present study it was evaluated as grain protectant against Ephestia kuehniella (Lepidoptera: Pyralidae) larvae, Prostephanus truncatus (Coleoptera: Bostrychidae) adults, Rhyzopertha dominica (Coleoptera: Bostrychidae) adults, Sitophilus oryzae (Coleoptera: Curculionidae) adults, and Tribolium confusum (Coleoptera: Tenebrionidae) larvae and adults. Etofenprox was applied at 0.1, 1, 5, and 10 ppm on wheat, or maize in the case of P. truncatus, and tested at different combinations of temperatures (20, 25, and 30 °C) and relative humidity (RH) levels (55 and 75%). Progeny production of the tested coleopteran adult species was also assessed. For E. kuehniella, after 21 days of exposure 75.6% of the exposed larvae were killed at 20 and 30 °C/55% RH. Mortality of P. truncatus adults reached 99.4 and 97.8% at 10 ppm of 55 and 75% RH, respectively, at 30 °C. For S. oryzae, after 21 days of exposure, mortality was moderate at both RH levels, even at the elevate doses, reaching 66.7% at 10 ppm at 20°C/75% RH. All R. dominica adults died 21 days post-exposure at 30°C/55% RH and 25 or 30°C/75% RH at 10 ppm. For T. confusum adults, mortality was 81.1% 10 ppm 21 days post-exposure at 20°C/75% RH. Etofenprox killed 99.4% of the exposed T. confusum larvae at 10 ppm respectively 14 days post-exposure at 25°C/55% RH. Concerning progeny production, complete suppression was recorded for P. truncatus, R. dominica, and T. confusum in various combinations of temperature/RH. Our findings indicate that etofenprox is a well-promising insecticide for the protection of stored grains. However, its performance differs among insect species and abiotic conditions.

Effects of temperature and relative humidity on the COVID-19 pandemic in different climates: a study across some regions in Algeria (North Africa)

After more than a year from the first confirmed cases of coronavirus (COVID-19) disease, the role of meteorological factors in the transmission of the virus still needs to be correctly determined. In this scenario of deep uncertainty, the present study aims to investigate the effects of temperature and relative humidity on daily new cases of COVID-19. For this purpose, the COVID-19's development of infection in fourteen Algerian cities characterized by different climatic conditions, during the period from April 1, 2020, to August 31, 2020, has been investigated. A detailed time series analysis along with linear regression was used to state a possible correlation among some climate's factor variability (temperature and relative humidity) and daily new confirmed cases of COVID-19. The results showed a weak correlation between daily new cases of COVID-19 and meteorological factors throughout the selected regions. In addition, we concluded that the COVID-19 could fit to high or low values of temperature and relative humidity, and other factors not climates could affect the spreading of the virus like demography and human contact. So, after the discovery of the vaccine and before vaccination of 70% of the world's population, living with the virus has become an inevitable reality, and it is mandatory to apply the sanitary procedures to slow down the COVID-19 transmission.

Effects of temperature and relative humidity on soil-air partition coefficients of organophosphate flame retardants and polybrominated diphenyl ethers

The soil-air partition coefficients (K_SA) of polybrominated diphenyl ethers (PBDEs) and organophosphate flame retardants (OPFRs) is important for determining their fate in soil and air media. However, K_SA values of OPFRs and PBDEs are not available from the current literature, and the effects of environmental factors such as temperature and relative humidity (RH) on K_SA values are not clear. In this study, a solid-phase fugacity meter was used to measure the K_SA values of PBDEs and OPFRs at different temperatures (25, 30, 35, 40, and 45 °C) and relative humidity (RH) conditions (<3 and 100% RH), the relationships between K_SA and octanol-air partition coefficients (K_OA) for OPFRs and PBDEs were analyzed. The results showed that an increase in temperature and RH resulted in a decrease of all K_SA values for PBDEs and OPFRs. Furthermore, the effects of RH on the soil-air partitioning behavior of PBDEs were larger than that of OPFRs. In addition, a significant correlation (p < 0.0001) was observed between log K_SA and log K_OA. The experimental K_SA values of OPFRs and PBDEs were quite different from the predicted K_SA, when calculated with their K_OA values. Overall, this study provides a better understanding for predicting the behavior and fate of OPFRs and PBDEs in soil-air systems.

Increasing agar content improves the sol-gel and mechanical features of starch/agar binary system

Starch/agar systems are highly potential for versatile applications such as packaging and biomedical materials. Here, how combined factors affect the features of a starch/agar binary system were explored. An increase of starch amylose/amylopectin ratio from 0/100 to 50/50 increased the sol-gel transition temperature and gel hardness of the aqueous starch/agar mixture. An increased agar content (mainly from 30% to 70%) allowed increases in both the tensile strength (reaching 50-60 MPa) and elongation at break of the starch/agar binary films. This phenomenon should be related to the strengthened crystalline structure and the weakened hydrogen bonding between starch chains (reflected by infrared spectroscopy). Furthermore, a higher relative humidity (from 30% to 70%) allowed enhanced chain interactions and probably nanoscale molecular order but weakened the crystalline structure, leading to reduced tensile strength and increased elongation at break. This work could facilitate the design of starch/agar binary systems with improved sol-gel and mechanical performance.

The interaction of temperature and relative humidity affects the main aromatic components in postharvest Torreya grandis nuts

The postharvest ripening stage is necessary for Torreya grandis (T. grandis) nuts to complete aromatic synthesis, which requires appropriate temperature and relative humidity (RH). Currently, scarce information is available regarding the changes in aroma profiles in T. grandis nuts and the relationship with their response to different environmental conditions. Therefore, the interaction of temperature (20 °C or 30 °C) and relative humidity (70% RH or 90% RH) was investigated on aromatic substances after harvest. The results showed that 56 aromatic components were detected by a gas chromatography-mass spectrometer (GC-MS) and mainly divided into five categories, among which terpenes were the most abundant (56.2-86.7%). Principal component analysis (PCA) showed that both temperature and humidity can affect the aroma composition, and terpenes were mainly influenced by humidity. Specifically, d-limonene occupied the largest proportion of terpenes (63.0-90.8%) and was significantly upregulated by high humidity.

Impact of relative humidity on the laying performance, egg quality, and physiological stress responses of laying hens exposed to high ambient temperature

The present study investigated the effects of relative humidity (RH) on the laying performance, egg quality, and stress indicators of laying hens raised at high ambient temperatures. A total of 180 Hy-Line Brown laying hens (68-wk-old) were randomly allotted to one of the following three RH conditions for 12 h a day (9:00 a.m.-9:00 p.m.) over four weeks: low RH (LRH; 25% RH), moderate RH (MRH; 50% RH), and high RH (HRH; 75% RH); ambient temperature was 30 °C under all treatments. None of the RH treatments affected hen-day egg production, egg weight, or egg mass (P > 0.05). However, feed intake was lower in the HRH group than in the LRH group (P < 0.05). Plasma corticosterone (CORT) concentration on day 21, yolk CORT concentration on day 3, and albumen CORT concentration on day 7 following RH exposure were higher in the HRH group than in the LRH group (P < 0.05). Moreover, plasma HDL-cholesterol concentration on day 14 was higher in the HRH group than in the LRH group (P < 0.05). On days 3 and 14, the Haugh unit decreased (P < 0.05) in the LRH group compared with that in the MRH and HRH groups. The HRH-exposed laying hens showed the lowest (P < 0.05) eggshell thickness on day 14. The absolute weights of eggshell, yolk, and albumen decreased in the HRH group compared with those in the MRH and LRH groups. Overall, high RH lowered feed intake and egg quality except for the Haugh unit, and induced stress response as manifested by elevated plasma, yolk, and albumen CORT concentrations. To our best knowledge, the present study is the first to demonstrate the role of RH in triggering temperature stress responses in laying hens.

GPS-ZTD data assimilation and its impact on wintertime haze prediction over North China Plain using WRF 3DVAR and CMAQ modeling system

Severe haze frequently hits the North China Plain (NCP), especially in winter during recent years. Meteorological factors affect aerosol formation and its optical properties, and accurate meteorological fields are imperative for accurate aerosol simulations. The impacts of Global Positioning System Zenith Total Delay (GPS-ZTD) data assimilation on meteorology and aerosol simulations were evaluated in this study using the WRF-CMAQ (the Weather Research and Forecasting model and Community Multiscale Air Quality) modelling system over the NCP during 01-31 December 2019. After bias correction, GSP-ZTD data were assimilated into the WRF model using the 3DVAR technique. Two sensitivity tests (CTR and ZTD) were conducted. The WRF model had generally acceptable performance for surface and upper air meteorological variables, PM_2.5 and visibility. From the aspect of BIAS, STDE, RMSE, and R, the assimilation of ZTD data improved the underestimation of ground relative humidity (RH). The improvement was more pronounced in the first 18 forecast hours. The mean RH BIAS decreased by 8%. Surface pressure was also improved in ZTD. The influence of ZTD data assimilation on ground temperature and wind tended to be neutral. The BIAS of ZTD decreased by 3% after data assimilation while STED or RMSE increased slightly. After ZTD data assimilation, the PM_2.5 underestimation decreased by 3.4% over NCP. And station mean BIAS or RMSE of PM_2.5 decreased at more than 70% stations. After ZTD data assimilation, the visibility overestimation was reduced by 2.5%. And more than 81% stations over had lower visibility BIAS or RMSE. Station mean PM_2.5 mass concentration increased by 1.5% in ZTD. The primary aerosol species increased by approximately 1%, and most secondary aerosol species increased by greater than 2% affected by both aerosol physical and chemical process. Although the improvement of PM_2.5 seems marginal from the perspective of regional or temporal average, the contribution of ZTD data assimilation on specific pollution episodes at specific stations can be great. The improvement of PM_2.5 troughs was in the range of 1-5 μg/m³, while the overestimation of PM_2.5 peaks was reduced by few up to dozens μg/m³. This will contribute to the extreme value prediction during pollution episode.

Leaf-cutting ants' critical and voluntary thermal limits show complex responses to size, heating rates, hydration level, and humidity

Thermal variation has complex effects on organisms and they respond to these effects through combined behavioral and physiological mechanisms. However, it is less clear how these traits combine in response to changes in body condition (e.g., size, hydration) and environmental factors that surround the heating process (e.g., relative humidity, start temperatures, heating rates). We tested whether these body conditions and environmental factors influence sequentially measured Voluntary Thermal Maxima (VT_max) and Critical Thermal Maxima, (CT_max) in leaf-cutting ants (Atta sexdens rubropilosa, Forel, 1908). VT_max and CT_max reacted differently to changes in body size and relative humidity, but exhibited similar responses to hydration level, start temperature, and heating rate. Strikingly, the VT_max of average-sized workers was closer to their CT_max than the VT_max of their smaller and bigger sisters, suggesting foragers maintain normal behavior at higher temperatures than sister ants that usually perform tasks within the colony. Previous experiments based on hot plate designs might overestimate ants’ CT_max. VT_max and CT_max may respond concomitantly or not to temperature rises, depending on body condition and environmental factors.

Estimating the impact of indoor relative humidity on SARS-CoV-2 airborne transmission risk using a new modification of the Wells-Riley model

A novel modified version of the Wells-Riley model was used to estimate the impact of relative humidity (RH) on the removal of respiratory droplets containing the SARS-CoV-2 virus by deposition through gravitational settling and its inactivation by biological decay; the effect of RH on susceptibility to SARS-CoV-2 was not considered. These effects were compared with the removal achieved by increased ventilation rate with outdoor air. Modeling was performed assuming that the infected person talked continuously for 60 and 120 min. The results of modeling showed that the relative impact of RH on the infection risk depended on the ventilation rate and the size range of virus-laden droplets. A ventilation rate of 0.5 ACH, the change of RH between 20% and 53% was predicted to have a small effect on the infection risk, while at a ventilation rate of 6 ACH this change had nearly no effect. On the contrary, increasing the ventilation rate from 0.5 ACH to 6 ACH was predicted to decrease the infection risk by half which is remarkably larger effect compared with that predicted for RH. It is thus concluded that increasing the ventilation rate is more beneficial for reducing the airborne levels of SARS-CoV-2 than changing indoor RH.

PRACTICAL IMPLICATIONS

The present results show that humidification to moderate levels of 40%-60% RH should not be expected to provide a significant reduction in infection risk caused by SARS-CoV-2, hence installing and running humidifiers may not be an efficient solution to reduce the risk of COVID-19 disease in indoor spaces. The results do however confirm that ventilation has a key role in controlling SARS-CoV-2 virus concentration in the air providing considerably higher benefits. The modified model developed in the present work can be used by public health experts, engineers, and epidemiologists when selecting different measures to reduce the infection risk from SARS-CoV-2 indoors allowing informed decisions concerning indoor environmental control.

Leveraging weather data for forecasting cases-to-mortality rates due to COVID-19

There are several recent publications criticizing the failure of COVID-19 forecasting models, with swinging over predictions and underpredictions, which have made it difficult for decision and policy making. Observing the failures of several COVID-19 forecasting models and the alarming spread of the virus, we seek to use some stable response for forecasting COVID-19, viz., ratios of COVID-19 cases to mortalities, rather than COVID-19 cases or fatalities. A trend of low COVID-19 cases-to-mortality ratios calls for urgent attention: the need for vaccines, for instance. Studies have shown that there are influences of weather parameters on COVID-19; and COVID-19 may have come to stay and could manifest a seasonal outbreak profile similar to other infectious respiratory diseases. In this paper, the influences of some weather, geographical, economic and demographic covariates were evaluated on COVID-19 response based on a series of Granger-causality tests. The effect of four weather parameters, viz., temperature, rainfall, solar irradiation and relative humidity, on daily COVID-19 cases-to-mortality ratios of 36 countries from 5 continents of the world were determined through regression analysis. Regression studies show that these four weather factors impact ratios of COVID-19 cases-to-mortality differently. The most impactful factor is temperature which is positively correlated with COVID-19 cases-to-mortality responses in 24 out of 36 countries. Temperature minimally affects COVID-19 cases-to-mortality ratios in the tropical countries. The most influential weather factor - temperature - was incorporated in training random forest and deep learning models for forecasting the cases-to-mortality rate of COVID-19 in clusters of countries in the world with similar weather conditions. Evaluation of trained forecasting models incorporating temperature features show better performance compared to a similar set of models trained without temperature features. This implies that COVID-19 forecasting models will predict more accurately if temperature features are factored in, especially for temperate countries.

Mechanistic insights into and modeling the effects of relative humidity on low-concentration VOCs adsorption on hyper-cross-linked polymeric resin by inverse gas chromatography

Water vapor is very common in contaminated streams, which has a great influence on the adsorption of low-concentration volatile organic compounds (VOCs) due to the competition between water and VOCs. Understanding adsorption mechanisms and predicting adsorption of VOCs under different relative humidity (RH) are of great importance to design effective adsorption unit. In this study, we comprehensively investigated the effects of RH on the surface properties of hyper-cross-linked polymeric resin (HPR) and adsorption of 18 VOCs at low concentration on HPR under five levels of RH using inverse gas chromatography (IGC). Further, a promising RH-dependent poly-parameter linear free energy relationships (PP-LFERs) model was developed. It was found that water vapor caused the decrease of surface free energy (γ_s^t) of HPR due to the occupation of active sites by water molecules, resulting in the decrease of adsorption partition coefficients (K). Moreover, the γ_s^t could accurately quantify the effects of RH on the surface properties of HPR. Therefore, the RH-dependent PP-LFERs model was established by correlating RH and γ_s^t. The developed model overcame the limited predictive ability of existing models only under a specific RH level, and excellently predicted the lnK values of VOCs (R² = 0.944, RMSEt = 0.36 and RMSEv = 0.47) under various RH.

Environmental controls and influences of Pinus roxburghii Sarg. (Chir pine) plantation on temporal variation in soil carbon dioxide emission and soil organic carbon stock under humid subtropical region

Soil carbon dioxide emission is a major component of ecosystem respiration, responsible for organic carbon losses from the ecosystem. In Pinus roxburghii Sarg. plantations, higher CO₂ emission coincided with maximum soil moisture and soil temperature during the rainy season (4.23 µmol CO₂m^-2 s^-1) followed by summer season (1.69 µmol CO₂m^-2 s^-1) and winter season (1.35 µmol CO₂m^-2 s^-1). The soil CO₂ emission rates recorded during the rainy season differed significantly from other seasons (p < 0.05). Multiple linear regression revealed that rainfall was the main dominant factor affecting the soil CO₂ emission. A significant positive correlation with minimum air temperature and average air temperature during the lag period, i.e., preceding 15 days of data, was recorded. A significant positive correlation was also observed between annual soil CO₂ emission rates with soil temperature, soil moisture, air temperature, and rainfall (p < 0.05). Vapor pressure and relative humidity at 14.19 h also emerged as additional scientific variables affecting soil CO₂ emission with significant positive correlations. Annual soil CO₂ emission rates and soil properties were not significantly correlated but were positively correlated with organic carbon, exchangeable potassium and negatively correlated with available nitrogen and phosphorous (p > 0.05). Higher annual average carbon stock, 95.05 t ha^-1 in P. roxburghii plantations than the yearly soil CO₂ emission, 33.23 t ha^-1 indicates that plantations sequester more carbon than the emissions.

Is Meteorology a Factor to COVID-19 Spread in a Tropical Climate?

It was speculated that fewer COVID-19 infections may emerge in tropical countries due to their hot climate, but India emerged as one of the leading hotspot. There is no concrete answer on the influence of meteorological parameters on COVID-19 even after more than a year of outbreak. The present study examines the impacts of Meteorological parameters during the summer and monsoon season of 2020, in different Indian mega cities having distinct climate and geography. The results indicate the sign of association, but it varies from one climatic zone to another. The principal component analysis revealed that humidity is strongly correlated with COVID-19 infections in hillocky city Pune (R = 0.70), dry Delhi (R = 0.50) and coastal Mumbai (R = 0.46), but comparatively weak correlation is found in arid climatic city of Ahmedabad. As against the expectations, no discernible correlation is found with temperature in any of the cities. As the virus in 2020 in India largely travelled with droplets, the association with absolute humidity in the dry regions has serious implications. Clarity in understanding the impact of seasonality will greatly help epidemiological research and in making strategies to control the pandemic in India and other tropical countries around the world.

High relative humidity improve chilling tolerance by maintaining leaf water potential in watermelon seedlings

Low temperature is a major environmental factor that severely impairs plant growth and productivity. Although the response to low temperature stress is well studied, the mechanisms of chilling tolerance are still not well understood. Here, we describe experiments that aimed to determine whether relative humidity (RH) contribute to chilling tolerance by regulating leaf water potential in watermelon seedlings. Plants exposed to chilling stress (10 °C/5 °C day/night) were severely wilted, and the water potential in their leaves was decreased. We found that maintaining high RH when plants were subjected to chilling-stress conditions attenuated the reduction in leaf water potential, reduced electrolyte leakage, improved the stability of photosynthesis, and alleviated chilling damage. Pretreatment with ABA increased chilling tolerance in low RH conditions but became ineffective in high RH conditions. Analysis of endogenous ABA content indicated that water potential mediated chilling tolerance was independent of ABA. Analysis of stomatal resistance indicated that the maintenance of water potential was related to stomatal resistance but that the balance between water absorption and loss is more important. In conclusion, high RH maintained leaf water potential and cell turgor, maintained better cell morphology, improved stomatal conductance and thus, ultimately improved the chilling tolerance of watermelon seedlings.

Investigation of SARS-CoV-2 in hospital indoor air of COVID-19 patients' ward with impinger method

In December 2019, all nations learnt about the emergence of a pandemic of coronavirus disease (COVID-19), induced by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is a member of the β-coronavirus group. As SARS-CoV-2 has the potentiality of leading to life-threatening respiratory failure, its transmission routes need to be characterized. Yet, the possibility of airborne transmission is still debated. This study was performed to evaluate potential hospital indoor air viral quality in order to detect SARS-COV-2. For this purpose, an impinger method was used to monitor the SARS-COV-2 virus in the air. Thus, 33 samples were collected from 8 different hospital locations. The sampling time was between 50 and 60 min with a sampling flow rate of 28 L/min. Air samples were taken from 2 to 5 m away from the patients' beds. Temperature, relative humidity, and CO₂ concentration were 28, 37, and 438 ppm, respectively. The results indicated that air samples which were 2 to 5 m away from the patients' beds were negative for the presence of the virus. According to the obtained results, it is suggested that airborne transmission may not have much effect on this pandemic. However, as the patients with SARS-CoV-2 were hospitalized in rooms with negative air pressure, the results might have been negatively affected. Graphical abstract.

The preparation of electrospun PVDF/TBAC multi morphology nanofiber membrane and its application in direct contact membrane distillation

Microporous membrane with a hydrophobic surface, high porosity and narrow pore size distribution is the ideal membrane distillation (MD) membrane. The electrospun membranes for MD is a new type and effective way to seawater desalination. Herein, a novel polyvinylidene fluoride (PVDF)/ tetrabutylammonium chloride (TBAC) electrospun nanofiber membrane (ENMs) fabricated apply to for direct contact membrane distillation (DCMD). Combine with the spinning condition, the characteristic and content of TBAC significant effect on the multi morphology structure of nanofiber. Therefore, the porous structure and morphology of PVDF/TBAC ENMs can be well-designed by optimizing relative humidity and TBAC concentration in spinning process, three different structure nanofiber membranes were obtained. Lab-scale setup was used to test membrane separation performance. The result indicated that the ultrafine ENMs with 0.025 mol/L TBAC presented a steady water flux of about 20.6 L/(m² h) and a high-efficiency salt rejection rate of over 99%. PVDF/TBAC ENMs are expected to provide a solution for development of efficient water treatment membrane. This article is protected by copyright. All rights reserved.

The association between initial COVID-19 spread and meteorological factors in Indonesia

On March 2, 2020, the first Coronavirus Disease (COVID-19) case was reported in Jakarta, Indonesia. One and a half months later (15/05/2020), the cumulative number of infection cases was 16,496, with a total of 1076 mortalities. This study investigates the possible role of weather in the early cases of COVID-19 in six selected cities in Indonesia. Daily temperature and relative humidity data from weather stations nearby in each city were collected from March 3 to April 30, 2020, corresponding with COVID-19 incidence. Correlation tests and regression analysis were performed to examine the association of those two data series. Moreover, we analyzed the distribution of COVID-19 referring the weather data to estimate the effective range of weather data supporting the COVID-19 incidence. Our result reveals that weather data is generally associated with COVID-19 incidence. The daily average temperature (T-ave) and relative humidity (RH) present significant positive and negative correlation with COVID-19 data, respectively. However, the correlation coefficients are weak, with the strongest correlations found at the 5-day lag, i.e., 0.37 (- 0.41) for T-ave (RH). The regression analysis consistently confirmed this relation. The distribution analysis reveals that most COVID-19 cases in Indonesia occurred in the daily temperature range of 25-31 °C and relative humidity of 74-92%. Our findings suggest that COVID-19 incidence in Indonesia has a weak association with weather conditions. Therefore, non-meteorological factors seem to play a more prominent role and should be given greater consideration in preventing the spread of COVID-19.

Graphic abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s42398-021-00202-9.

Evaluation of pig behavior changes related to temperature, relative humidity, volatile organic compounds, and illuminance

The objective of this study was evaluation of pig behavior changes related to temperature, relative humidity, volatile organic compounds (VOCs), and illuminance. A total of 24 growing pigs ([Yorkshire × Landrace] × Duroc) were used in the experiment. A sensor was installed at a height of 0.5 m in the center of the pig house. In experiment 1, temperature was changed every four days to 18°C (T1), 22°C (T2), 26°C (T3), and then 30°C (T4). In experiment 2, relative humidity was adjusted to 45% (low humidity [LH]), 60% (middle humidity [MH]), and then 75% (high humidity [HH]) for four days. In experiment 3, after cleaning the pig house just before experiment, only minimal ventilation was provided. VOCs and pig behaviors were observed for 7 days without cleaning the pig house. In experiment 4, three light bulbs of 40 W (470 lumens / 45 lx; low illuminance [LI]), 75 W (1,055 lumens / 103 lx; middle illuminance [MI]), and 100 W (1,521 lumens / 146 lx; high illuminance [HI]) were used for four days each. Pig behavior analysis was performed for following criteria : Feed intake, Standing, Lying, Sitting, Drink water, Rooting, Posture transition (lying-standing), Posture transition (standing-lying), Wallowing, and Biting. In experiment 1, feed intake time was lower (p < 0.05) for the T3 than other treatment groups. Standing time was highest (p < 0.05) for the T1 and lowest (p < 0.05) for the T3. Lying time was shorter (p < 0.05) in T1 and T2 compared to T3 and T4. Drinking frequency was higher (p < 0.05) for the T4 than other treatment groups. In experiment 2, the frequency of rooting and wallowing increased (p < 0.05) with increasing humidity. LH showed the lowest (p < 0.05) rooting frequency and HH showed the highest (p < 0.05) rooting frequency. In experiment 3, VOCs concentration did not (p > 0.05) change pig behavior. In experiment 4, lying time was the longest (p < 0.05) at LI and shortest (p < 0.05) at HI. Therefore, pig behavior is heavily influenced by the environment, especially temperature and humidity. However, correlation between pig behavior to VOCs and illuminance seems to be needed more research.

Modeling the survival of Salmonella on whole cucumbers as a function of temperature and relative humidity

Recent multistate outbreaks of salmonellosis associated with fresh cucumbers underscore the importance of understanding Salmonella behavior on cucumbers under different conditions. This study developed mathematical models to predict the survival of four-strain cocktail of Salmonella on whole cucumbers at different temperature and relative humidity (RH) conditions. The strains were Salmonella Newport H1275 and Stanley H0558 (sprout outbreaks), Montevideo G4639 (tomato outbreak), and Saintpaul 02-517-1 (cantaloupe outbreak). Inoculated cucumbers were placed in desiccators containing saturated salt solution to create controlled RH environments (~15, 50, 100% RH) at 7, 14, and 21 °C, and enumerated at time intervals ranging from 0 to 240 h. Predictive models were developed using Baranyi and Roberts equation as a primary model and estimated kinetic parameters were fitted into a polynomial equation for secondary models. Reduced model polynomial equations which describe the maximum death rate and the log reduction of Salmonella on whole cucumber as a function of temperature and RH had high R² values (>0.95). Validation results verified the performance and reliability of the predictive models. The models in this study will be useful for future microbial risk assessments and predictions of Salmonella behavior in the cucumbers to manage the risk of Salmonella on whole cucumbers.