Low Relative Humidity Conditions Research Articles

An Application of Mist Generator as a Way to Reduce Particulate Matter during High Concentration Episodes in Urban Forests

Previous conventional mist devices can induce a detrimental effect of leaf burn by intense, focused sunlight in summer. A mist generator is designed to prevent particulate matter (PM) damage to trees by combining mist with PM during high PM episodes. We measured changes in microclimate conditions and the concentration of PM before, during, and after mist spraying in urban parks (Yangjae Citizen Forest, YCF; Cheongdam Road Park, CRP) from May 6 to 8, 2020. PM changes in YCF and CRP were observed immediately after mist spraying and were found to return to the previous concentrations. Mist spraying had no significant effects on the meteorological traits of air temperature, humidity, and wind speed but had significant effects on the concentration of PMx and the ratio of PM during a short time. Also, the ratio of PMx was partially affected by mist spraying. During the morning rush hour and lunch, mist, high wind speed, and low relative humidity conditions were related to the increase in mist movement, resulting in increasing PM (2.5–10 μm) and the deposition of these PM. During the evening rush hour, high relative humidity and low wind speed affected PM concentrations more than mist. This prototype of mist spraying could effectively condense and deposit the PM during high PM episodes.

Enhanced Hydrophilicity of DAAQ-TFP COFs via Sulfonate Modification for Air Water Harvesting in Arid Environment.

The poor ability of covalent organic frameworks (COFs) based adsorbents at low relative humidity (RH) conditions limits their applications for air-water harvesting in arid environments. In the present work, the sulfonated COFs (DAAQ-TFP-SO3H@LiCl) composites are prepared through the functionalization of sulfonic acid and LiCl composite to improve its hydrophilicity. TheDAAQ-TFP-SO3H@LiCl composites exhibit a good adsorption performance, outperforming many other COF adsorbents developed so far. It can absorb 0.22±0.005g g-1 and 1.01±0.027g g-1 of water at room temperature under 20% RH and 90% RH, respectively while demonstrating good cyclic stability. Compared with the isotherm of the DAAQ-TFP, the introduction of the sulfonic acid group shifts the inflection point of the water isotherm toward low humidity, indicating that the sulfonic acid group effectively expends the working humidity range of the adsorbent and enables the effective water adsorption in an arid environment. Furthermore, the DAAQ-TFP-SO3H@LiCl composites display rapid kinetics during both the adsorption and desorption processes, reaching saturation within 60min in the equilibrium adsorption test and completing desorption within 12min at 50°C. This innovative approach provides a new method for designing adsorbent materials with low energy input requirements and high daily water consumption capabilities.

Responses of surface ozone under the tropical cyclone circulations: Case studies from Fujian Province, China

The circulation of tropical cyclones (TCs) exerts a multifaceted influence on the spatial and temporal distribution of surface pollutants. This study investigates the response of surface ozone (O3) concentration to the TCs in Fujian Province from June to December 2022 by analyzing the contributions of atmospheric pollutants, meteorological conditions, and dynamical transports. Empirical orthogonal function (EOF) decomposition methods are used to analyze the spatio-temporal distribution patterns of affected O3, and a Gradient Boosting Regression Trees (GBRT) machine learning model is employed to estimate surface O3 concentration, quantifying the influence of each factor. The results indicate an anomaly increase in O3 concentration during this period, with photochemistry-related meteorological conditions being the primary influencer, accounting for 66.9% of O3 variations, elucidating the interpretability of the GBRT model for attributing changes in O3 concentration. Low relative humidity and high temperature conditions have been identified as pivotal factors influencing the rise in O3 concentrations. The presence of TC undermines this predominant influence, amplifying the role of transport factors and other atmospheric pollutants. In the case studies of TC (Muifa and Nanmadol, 2022), the slow or stagnant TCs triggered persistent downdrafts in its periphery and brought favorable meteorological conditions such as clear sky and warm temperature for photochemistry. TCs also enhances the impact of horizontal and vertical dynamic transport on O3 concentrations. This work provides vital insights into the complex interplay between TCs and surface O3 concentrations, highlighting the need for targeted environmental and air quality management strategies in regions frequently impacted by TCs.

Cross-linked proton exchange membrane covalently bonded with silicotungstic acid for enhanced proton conductivity

Proton exchange membranes with cross-linked structures often showed excellent mechanical and chemical stability, but their water absorption and proton conductivity were restricted. This study reported a convenient and efficient thermal cross-linking reaction of sulfonic acid groups and benzene rings using dimethyl sulfoxide and sulfolane mixed solvents to prepare the membrane. To further illustrate, phenoxyphenyl-attached silicotungstic acid (POP-SiWA) was incorporated in the sulfonated poly(ether ether ketone) membrane and covalently bonded with the polymer by thermal cross-linking reaction. The immobilization ratio for the membranes prepared with 10∼30 wt% POP-SiWA addition was 88.0–63.7%. The modified membranes exhibited high hydrophilicity and improved proton conductivity under hydrated or low relative humidity conditions due to the strong acidity and water-retaining properties of silicotungstic acid. Specifically, the proton conductivity of the modified membrane with 30 wt% POP-SiWA reached 212 mS/cm. It exhibited a fuel cell power density of 629 mW/cm2 at 80 °C and 100% relative humidity, which were 1.90 and 2.67 times higher than the pristine membrane.

Morphology and elemental composition of individual solid dust particles: From different sources to the atmosphere

This study investigates the morphology and elemental composition of individual solid dust particles from various sources (e.g., thermal power plant, domestic coal combustion, building construction dust, wind-blown dust, Asian dust storm, and road related dust) to the atmosphere under high and low relative humidity (RH) conditions in a coastal city of north China by using high-resolution electron microscopes. The results showed that distinct variations between dust particles from thermal power plant and domestic coal combustion, despite both using coal as fuel. Specifically, 88.6% (by number) of thermal power plant particles were spherical, whereas only 2 out of 347 particles from domestic coal combustion exhibited a spherical shape. Furthermore, domestic coal combustion particles showed a higher proportion of Ca-rich particles compared to those from thermal power plant. The wind-blown dust and Asian dust storm particles were mainly “Si + Al” subtype (52.0% v.s. 75.3%) and Si-dominant subtype (16.4% v.s. 11.7%) particles, which were mainly from crustal sources. However, wind-blown dust contained a higher fraction of Ca-rich (11.6%) and Fe-rich (5.3%) particles than Asian dust. The building construction dust particles primarily consisted of irregular Ca-dominant (39.4%) and “Ca + Si” subtype (29.8%) particles. Road related dust were also mainly Si-rich particles (52.9%), likely from re-suspended soil, along with a notable presence of spherical (8.0%) and Fe-rich particles (19.3%), possibly linked to vehicle emissions and brake wear. Additionally, relative number percentage of Na-rich particles and the average weigh ratios of Na in the atmospheric particles were higher than those from all above-mentioned source samples, suggesting that sea-salt related particles might be an important source of the atmospheric dust at the coastal city. The results indicated that Ca-rich particles were significantly modified by S and NaCl particles might lose Cl through heterogeneous reactions under higher RH.

Investigating the impact of extreme weather events and related indicators on cardiometabolic multimorbidity

BackgroundThe impact of weather on human health has been proven, but the impact of extreme weather events on cardiometabolic multimorbidity (CMM) needs to be urgently explored.ObjectivesInvestigating the impact of extreme temperature, relative humidity (RH), and laboratory testing parameters at admission on adverse events in CMM hospitalizations.DesignsTime-stratified case-crossover design.MethodsA distributional lag nonlinear model with a time-stratified case-crossover design was used to explore the nonlinear lagged association between environmental factors and CMM. Subsequently, unbalanced data were processed by 1:2 propensity score matching (PSM) and conditional logistic regression was employed to analyze the association between laboratory indicators and unplanned readmissions for CMM. Finally, the previously identified environmental factors and relevant laboratory indicators were incorporated into different machine learning models to predict the risk of unplanned readmission for CMM.ResultsThere are nonlinear associations and hysteresis effects between temperature, RH and hospital admissions for a variety of CMM. In addition, the risk of admission is higher under low temperature and high RH conditions with the addition of particulate matter (PM, PM2.5 and PM10) and O3_8h. The risk is greater for females and adults aged 65 and older. Compared with first quartile (Q1), the fourth quartile (Q4) had a higher association between serum calcium (HR = 1.3632, 95% CI: 1.0732 ~ 1.7334), serum creatinine (HR = 1.7987, 95% CI: 1.3528 ~ 2.3958), fasting plasma glucose (HR = 1.2579, 95% CI: 1.0839 ~ 1.4770), aspartate aminotransferase/ alanine aminotransferase ratio (HR = 2.3131, 95% CI: 1.9844 ~ 2.6418), alanine aminotransferase (HR = 1.7687, 95% CI: 1.2388 ~ 2.2986), and gamma-glutamyltransferase (HR = 1.4951, 95% CI: 1.2551 ~ 1.7351) were independently and positively associated with unplanned readmission for CMM. However, serum total bilirubin and High-Density Lipoprotein (HDL) showed negative correlations. After incorporating environmental factors and their lagged terms, eXtreme Gradient Boosting (XGBoost) demonstrated a more prominent predictive performance for unplanned readmission of CMM patients, with an average area under the receiver operating characteristic curve (AUC) of 0.767 (95% CI:0.7486 ~ 0.7854).ConclusionsExtreme cold or wet weather is linked to worsened adverse health effects in female patients with CMM and in individuals aged 65 years and older. Moreover, meteorologic factors and environmental pollutants may elevate the likelihood of unplanned readmissions for CMM.

An oxidation flow reactor for simulating and accelerating secondary aerosol formation in aerosol liquid water and cloud droplets

Abstract. Liquid water in cloud droplets and aqueous aerosols serves as an important reaction medium for the formation of secondary aerosol through aqueous-phase reactions (aqSA). Large uncertainties remain in estimates of the production and chemical evolution of aqSA in the dilute solutions found in cloud droplets and the concentrated solutions found in aerosol liquid water, which is partly due to the lack of available measurement tools and techniques. A new oxidation flow reactor (OFR), the Accelerated Production and Processing of Aerosols (APPA) reactor, was developed to measure secondary aerosol formed through gas- and aqueous-phase reactions, both for laboratory gas mixtures containing one or more precursors and for ambient air. For simulating in-cloud processes, ∼ 3.3 µm diameter droplets formed on monodisperse seed particles are introduced into the top of the reactor, and the relative humidity (RH) inside it is controlled to 100 %. Similar measurements made with the RH in the reactor < 100 % provide contrasts for aerosol formation with no liquid water and with varying amounts of aerosol liquid water. The reactor was characterized through a series of experiments and used to form secondary aerosol from known concentrations of an organic precursor and from ambient air. The residence time distributions of both gases and particles are narrow relative to other OFRs and lack the tails at long residence time expected with laminar flow. Initial cloud processing experiments focused on the well-studied oxidation of dissolved SO2 by O3, with the observed growth of seed particles resulting from the added sulfuric acid agreeing well with estimates based on the relevant set of aqueous-phase reactions. The OH exposure (OHexp) for low RH, high RH, and in-cloud conditions was determined experimentally from the loss of SO2 and benzene and simulated from the KinSim chemical kinetics solver with inputs of the measured 254 nm UV intensity profile through the reactor and loss of O3 due to photolysis. The aerosol yield for toluene at high OHexp ranged from 21.4 % at low RH with dry seed particles present in the reactor to 78.1 % with cloud droplets present. Measurement of the composition of the secondary aerosol formed from ambient air using an aerosol mass spectrometer showed that the oxygen-to-carbon ratio (O : C) of the organic component increased with increasing RH (and liquid water content).

Influence of relative humidity on carbon sequestration and crystal morphology of air lime: A sustainable building material

This study investigated the carbon sequestration potential of air lime by carbonation in two different relative humidity conditions. The carbonation rate and amount of carbon dioxide captured were quantified using weight gain and various analytical techniques. Samples cured in high relative humidity showed almost complete carbon capture by sequestering 94.8 % of carbon dioxide from atmospheric air within 56 days, with calcite crystal formation and a high crystallinity index. Similarly, samples cured in low relative humidity conditions showed slightly less carbonation around 83.8 % with different calcium carbonate polymorphs like aragonite and vaterite, along with amorphous calcium carbonate. Results demonstrated that carbonation of lime is a promising technology for carbon capture and utilization in buildings as non-load bearing mortars or plasters and could be used to reduce carbon dioxide levels in the atmosphere.

Characteristics of new particle formation events occurred over the Yellow Sea in Springtime from 2019 to 2022

Characteristics of atmospheric new particle formation (NPF) events were investigated using the data obtained from the ship measurement campaign named Yellow Sea Air Quality (YES-AQ) over the Yellow Sea during the springtime from 2019 to 2022. NPF events occurred 15 times for the valid 128 observation days for the four-year period, and the average and standard deviation formation rate (FR) and growth rate (GR) of the NPF events were 2.38 ± 1.53 cm−3 s−1 and 4.11 ± 2.81 nm h−1, respectively. The FR and GR were close to those in urban regions, implying the unique characteristics of the Yellow Sea. Owing to the NPF events, the number concentrations of total aerosols and nucleation mode particles increased by approximately 7850 and 6002 cm−3, respectively, and those of cloud condensation nuclei at 0.2% and 0.6% supersaturation increased by about 1269 and 3269 cm−3, respectively. The NPF events mostly occurred under the meteorological conditions of low temperature and relative humidity as well as high solar radiation and wind speed. These meteorological conditions appeared predominantly when the air mass originated from the continent north of the Korean Peninsula. The current analyses based on the data measured repeatedly during a specific period each year, which were not well conducted in other maritime NPF studies, highlight the reliability of the presented characteristics of NPF events over the Yellow Sea.

Aerosol influence on cloud macrophysical and microphysical properties over the Tibetan Plateau and its adjacent regions.

This study uses aerosol optical depth (AOD) and cloud properties data to investigate the influence of aerosol on the cloud properties over the Tibetan Plateau and its adjacent regions. The study regions are divided as the western part of the Tibetan Plateau (WTP), the Indo-Gangetic Plain (IGP), and the Sichuan Basin (SCB). All three regions show significant cloud effects under low aerosol loading conditions. In WTP, under low aerosol loading conditions, the effective radius of liquid cloud particles (LREF) decreases with the increase of aerosol loading, while the effective radius of ice cloud particles (IREF) and cloud top height (CTH) increase during the cold season. Increased aerosol loading might inhibit the development of warm rain processes, transporting more cloud droplets above the freezing level and promoting ice cloud development. During the warm season, under low aerosol loading conditions, both the cloud microphysical (LREF and IREF) and macrophysical (cloud top height and cloud fraction) properties increase with the increase of aerosol loading, likely due to higher dust aerosol concentration in this region. In IGP, both LREF and IREF increase with the increase in aerosol loading during the cold season. In SCB, LREF increases with the increase in aerosol loading, while IREF decreases, possibly due to the higher hygroscopic aerosol concentration in the SCB during the cold season. Meteorological conditions also modulate the aerosol-cloud interaction. Under different convective available potential energy (CAPE) and relative humidity (RH) conditions, the influence of aerosol on clouds varies in the three regions. Under low CAPE and RH conditions, the relationship between LREF and aerosol in both the cold and warm seasons is opposite in the WTP: LREF decreases with the increase of aerosol in the cold season, while it increases in the warm season. This discrepancy may be attributed to a difference in the moisture condition between the cold and warm seasons in this region. In general, the influence of aerosols on cloud properties in TP and its adjacent regions is characterized by significant nonlinearity and spatial variability, which is likely related to the differences in aerosol types and meteorological conditions between different regions.

VARIATIONS OF δ18О AND δ2H VALUES OF PRECIPITATION IN MOSCOW FROM 2017 TO 2019

To reveal variations in the iso topic composition of O and H in the atmospheric precipitation in Moscow and the processes influencing the isotope composition, all events of precipitation in 2017-2019 were sampled at the Meteorological Observatory of the Moscow State University: 158 samples in 2017, 119 samples in 2018 and 143 samples in 2019. The study is a prolongation of continuous measurements of the isotope composition of precipitation, started by authors in 2014. The study of the isotope composition of precipitation at the MSU Meteorological Observatory was supported by the IAEA and became a part of the Global Network of Isotopes in Precipitation (GNIP) database. It has been found that the intra-annual variability of the isotop e composition of precipitation has a pronounced seasonality. The most isotopically heavy precipitation falls from May to August, and the most isotop ically light precipitation at December-February, mainly due to seasonal air temperature variations. The ratio of the average monthly δ18O values in precipitation and air temperature for the study period varied from 0.34 to 0.39‰/°C, which is consistent with the previously obtained data for precipitation in Moscow. The δ2H-δ18O ratio in precipitation was clos e to that of the Global Meteoric Water Line, pointing to the equilibrium conditions during precipitation formation. It was established that in the summer months isotopic composition is significantly influenced by undercloud evaporation. The deuterium excess va lues in precipitation are not markedly seasonal; however, lower dexc values (below the 3-year average of 11‰) are typical for the summer months (July-August). It is most likely due to undercloud evaporation in conditions of low relative humidity and high air temperatures. Higher dexc values (above 11‰) prevailed from October to April.

A highly sensitive flexible humidity sensor based on a wafer-level composite material of carbon-quantum-dots@nanofiber clusters

A novel composite material composed of carbon-quantum-dots@nanofiber clusters (CQDs@NFCs) is successfully developed in wafer level, taking it as a sensitive material, a flexible humidity sensor is also developed. Since the composite material is superhydrophilic and contains a super large number of nanopores of different sizes, capillary condensation is able to take place within the composite material at different relative humidity (RH) conditions. Taking advantage of the chemi-physisorption and the capillary condensation, such a sensing material helps to significantly improve sensitivity of the flexible sensor, especially at low RH conditions. Compared with the device adopting only nanofibers as the sensing material, this novel sensor offers a 4.3-time increament in sensitivity within a humidity range of 7%−59% RH, while maintains high sensitivity in the entire humidity range. This heightened sensitivity is crucial for monitoring low-level humidity with high accuracy, making the sensor highly promising for various applications.

Prediction model of asphalt emulsion evaporation rate based on CFD simulation and genetic programming-based symbolic regression

The evaporation rate of asphalt emulsion is critical to the strength development of asphalt emulsion materials. Its value is dependent on environmental factors, i.e. relative humidity, temperature, and wind speed. However, the quantitative relation of evaporation rate with these environmental factors are unclear. To quantificationally study the effect of environmental factors on the water evaporation rate of asphalt emulsion, a computational fluid dynamics (CFD) simulation model of water evaporation is firstly proposed and validated by experiment. Then, wide range of environmental factors are studied in the CFD simulation model, and genetic programming-based symbolic regression is used to train the simulation results of CFD samples. Finally, a relatively accurate prediction equation of the evaporation rate of asphalt emulsion versus environmental factor is proposed, and the sensitivity of the water evaporation rate under the three environmental factors is analyzed. Results show that the evaporation rate can be accurately simulated by CFD. All the three environmental factors can greatly affect the evaporation rate of asphalt emulsion, while their effect on the sensitivity of the water evaporation rate is ranked as: temperature > relative humidity > wind speed. To ensure an acceptable curing period, asphalt emulsion-based materials should be avoided to be paved in the conditions of low temperature and high relative humidity.

Photo-oxidative Crack Propagation in Transition Metal Dichalcogenides.

Monolayered transition-metal dichalcogenides (TMDs) are easily exposed to air, and their crystal quality can often be degraded via oxidation, leading to poor electronic and optical device performance. The degradation becomes more severe in the presence of defects, grain boundaries, and residues. Here, we report crack propagation in pristine TMD monolayers grown by chemical vapor deposition under ambient conditions and light illumination. Under a high relative humidity (RH) of ∼60% and white light illumination, the cracks appear randomly. Photo-oxidative cracks gradually propagated along the grain boundaries of the TMD monolayers. In contrast, under low RH conditions of ∼2%, cracks were scarcely observed. Crack propagation is predominantly attributed to the accumulation of water underneath the TMD monolayers, which is preferentially absorbed by hygroscopic alkali metal-based precursor residues. Crack propagation is further accelerated by the cyclic process of photo-oxidation in a basic medium, leading to localized tensile strain. We also found that such crack propagation is prevented after the removal of alkali metals via the transfer of the sample to other substrates.

Reaction between Criegee Intermediate CH2OO and Isobutyraldehyde: Kinetics and Atmospheric Implications

AbstractIn the present work, we have investigated the 1,3‐cycloaddition reaction of isobutyraldehyde ((CH3)2CHCHO) with the simplest Criegee intermediate CH2OO using the OH laser‐induced fluorescence (LIF) method in a reaction tube. The experiments were conducted at temperatures and pressures ranging from 280 to 338 K and 5 to 150 Torr. We found that the bimolecular rate coefficient of the reaction is temperature‐ and pressure‐dependent. The measured rate coefficients at 100 Torr are (4.93±0.89), (4.46±0.80), (3.99±0.72), (3.56±0.64), (3.34±0.60), (2.98±0.54), (2.78±0.50)×10−12 cm3 molecule−1 s−1 at 280, 288, 298, 308, 318, 328, and 338 K, respectively. A high‐pressure limit rate coefficient of (4.47±0.80)×10−12 cm3 molecule−1 s−1 was obtained at 298 K by fitting the pressure‐dependent rate coefficients according to the Lindemann mechanism. The Arrhenius plot of the temperature‐dependent rate coefficients results in an activation energy of (−1.86±0.33) kcal mol−1 and a preexponential factor of (1.72±0.31)×10−13 cm3 molecule−1 s−1. In the atmosphere, the reaction of CH2OO with isobutyraldehyde may contribute to the sink of CH2OO in regions where isobutyraldehyde emission is intense under low temperature and low relative humidity conditions.

Bunch transpiration is involved in the hastening of grape berry ripening under elevated temperature and low relative humidity conditions

The present study aimed: i) to evaluate the impact of the changes in temperature and relative humidity (RH), projected by the year 2100, on grape ripening, and ii) to assess if bunch transpiration is a key physiological process involved in the advancement in grape development under future climate conditions. Fruit-bearing cuttings of Vitis vinifera L. cv. ‘Tempranillo’ were grown, from fruit set to maturity, in glasshouses under two conditions: 24°C/14°C and 55%/70% RH (day/night) (T) vs 28°C/18°C and 43%/58% RH (T+4). To elucidate the role of bunch transpiration in grape development in a future climate scenario, the bunches of half of the plants in the T+4 glasshouse were sprayed with an antitranspirant (AT+4). T+4 increased bunch transpiration, hastened the ripening process, increasing the rate of total soluble solid (TSS) accumulation and malic acid degradation, and reduced the concentration of total anthocyanins. The application of antitranspirant partially alleviated the effects of combined high temperature and low RH on maturation times, through lower TSS accumulation rates. Berries in AT+4 had the lowest concentrations of anthocyanins and color, likely related to a reduction in light transmittance by the antitranspirant film and to higher anthocyanin degradation due to the longer exposure to elevated temperatures. The results show a negative impact of elevated temperature and low RH on grape composition. The increased bunch transpiration under these conditions played an important role in the changes observed in phenology and sugar accumulation.

Performance analysis of a rotary desiccant wheel using polymer material with high water uptake and low regeneration temperature

Desiccant wheels have been widely used in humidity control, particularly under conditions with ultra-low dew point temperatures. However, traditional desiccants such as silica gel and zeolites are subject to relatively low adsorption capacity and high regeneration temperature. To address these challenges, a type of polymer material with high water uptake and low regeneration temperature is investigated in this paper. Firstly, the adsorption/desorption capacity of this polymer is thoroughly tested. Results reveal that its remarkable equilibrium adsorption capacity and desorption rate coefficients kLDF,de are 350% and 32–64% higher than that of silica gel, respectively. Moreover, its required regeneration temperature is just about 40–70 °C. The performance of the desiccant wheel using this polymer is simulated by a model validated by experiments tests. Parameter analysis demonstrates that the desiccant wheel is suitable for cool and humid conditions, reaching the maximum moisture removal (∆Y) and dehumidification coefficient of performance (DCOP) of 4.0 g kg−1 and 0.66, respectively. Furthermore, the corresponding relationship between other parameters and the optimal rotation speed is discussed in detail. The ωopt is around 18 rph, enabling the attainment of the highest ∆Y. Finally, the performance comparison with a traditional silica gel desiccant wheel is carried out. The results indicate that the polymer one performs 17–53.9% higher in terms of both ∆Y and DCOP than the silica gel counterpart. And the most significant improvement is observed in low relative humidity conditions (45%RH), where ∆Y and DCOP are 1.25–1.53 times that of the silica gel's, highlighting the advantageous utilization of the polymer material.

Standardized agronomic practices for mechanical harvesting of the single-harvest garden pea in India

The field investigations were conducted at Vegetable Research Farm, Department of vegetable Science, Punjab Agricultural University, Ludhiana with the objective to standarize the agronomic practices for mechical harvesting of garden pea. Therefore, effect of different agronomic traits including time of sowing, spacing and sowing method on yield and its attributing traits were studied on single-harvest garden pea. The experiment was laid out in split-plot design with 30 treatments comprising five dates of sowing in main plots and 2 different planting methods (flat and bed) sown at three different spacing in subplots and replicated three times. The bed size was standardized according to front-loading width of the pea combine. Significant interactions were observed between the date of sowing and spacing for a number of pods per plant, green seeds per pod, green pod yield per plant, green pod yield per plot; date of sowing and sowing method for pod length; spacing and sowing method for plant height. However, for all the traits, there was non-significant 3-way interaction. The late sown (20th December) crop resulted in the least number of pods per plant, green seeds per pod, green pod yield per plant and green pod yield per plot which was due to high temperature and low relative humidity conditions at pod development and filling stage. It is concluded that the garden pea cultivar Punjab-89 sown on 5th November at the spacing of 20 × 7.5 cm on beds (bed width of 1.0 m) resulted in significantly highest green pod yield of 12.75 kg/9 m2 in the single harvest. Therefore, the 3 beds of 1 m width can be harvested together with pea combine (because combine has working front width of 3.1 m) results into maximum yield when pea crops is sown on 5th November @ 20 × 7.5 cm spacing.

Microcracking of strawberry fruit cuticles: mechanism and factors

Microscopic cracks in the cuticle (microcracks) are the first symptom of the strawberry fruit disorder ‘water soaking’ in which the fruit surface appears watery, translucent, and pale. Water soaking severely impacts fruit quality. The objective was to investigate the factors and mechanisms of cuticular microcracking in strawberry. Fluorescence microscopy revealed numerous microcracks in the achene depressions, on the rims between depressions and at the bases of trichomes. Microcracks in the achene depressions and on the rims were either parallel or transversely oriented relative to a radius drawn from the rim to the point of attachment of the achene. In the achene depression, the frequency of microcracks with parallel orientation decreased from the calyx end of the fruit, towards the fruit tip, while the frequency of those with transverse orientation remained constant. Most microcracks occurred above the periclinal cell walls of the epidermal cells. The long axes of the epidermal cells were primarily parallel-oriented. Microcracking increased during fruit development. Cuticle mass per fruit remained constant as fruit surface area increased but cuticle thickness decreased. When fruit developed under high relative humidity (RH) conditions, the cuticle had more microcracks than under low RH conditions. Exposing the fruit surface to increasing RHs, increased microcracking, especially above 75% RH. Liquid-phase water on the fruit surface was markedly more effective in inducing microcracking than high vapor-phase water (high RH). The results demonstrate that a combination of surface area growth strain and water exposure is causal in inducing microcracking of the strawberry cuticle.

Significant impact of water-soluble organic matter on hygroscopicity of fine particles under low relative humidity condition

Uncertainties in estimating the hygroscopicity of bulk aerosols under conditions of low relative humidity (RH) or below the deliquescent RH (DRH) of aerosols remain to be significant, mainly due to the presence of water-soluble organic matter (WSOM). To quantify the contributions of WSOM to aerosol hygroscopicity and associated uncertainties, a field campaign was conducted to measure the hygroscopic growth curve (f(RH)) of bulk aerosols online, dominant chemical compositions in PM2.5 online and offline, and size distributions of the dominant chemical compositions offline during the dry and wet seasons of 2019–2020 in urban Guangzhou of south China. Based on the measured f(RH), the hygroscopicity parameter (κ) of bulk aerosols (κ-f(RH)) exhibits a logarithmic increase with increasing RH until RH reaches 69 %. Beyond this threshold, κ-f(RH) increases very slowly with further increase of RH, reaching 0.32 ± 0.04 during the dry season and 0.31 ± 0.05 during the wet season. The κ of WSOM (κ-WSOM) was further estimated to be 0.22 ± 0.03 and 0.13 ± 0.04 in the dry and wet seasons, respectively, when RH > 69 %. WSOM significantly affects κ-f(RH) by retarding the deliquescence process of aerosols and altering the mass ratio of water-soluble inorganic salts (WSIS) to WSOM within the size range of 0.4–0.9 μm, especially under low RH conditions (<60 %). The κ-f(RH) under low RH conditions was revised based on the logarithmic regression equation between RH and the ratio of measured κ-f(RH) to estimated κ-f(RH>69%). f(RH) of WSIS and WSOM were then corrected using the revised κ-f(RH) under low RH conditions, which showed 22–31 % lower values than those produced by the IMPROVE formulas.