Chamber Studies Research Articles

A chamber study of catalytic oxidation of SO2 by Mn2+/Fe3+ in aerosol water

The catalytic oxidation of SO2 by metal ions in aerosol water may be one of the important sources of sulfate in the atmospheric environment. In order to better understand the catalytic oxidation in aerosol water, a series of experiments were carried out in a smog chamber system under the conditions of relatively low concentrations of SO2 with Mn2+/Fe3+ as catalysts in NaNO3 aerosol water. In the Mn2+-catalytic oxidation process, the reaction rate (R) in aerosol water is expressed as R = 2.0 × 104 [Mn2+][S(IV)]1.3 at the initial pH range 4–5, which is about 2 orders of magnitude higher than that in bulk water. When the pH of aerosol water and relative humidity (RH) are high, the catalytic oxidation of SO2 by Mn2+ in aerosol water is probably an important source of sulfate. In the Fe3+-catalytic oxidation process, the reaction rate is significantly lower than that of Mn2+-catalytic oxidation, and the rate hardly exceeds 2 orders of magnitude larger than that in bulk water. The role of synergistic catalysis between Fe3+ and Mn2+ for oxidation of SO2 in aerosol water is very limited.

Development and application of a low-cost vaporizer for rapid, quantitative, in situ addition of organic gases and particles to an environmental chamber

Environmental chamber studies are widely employed to investigate atmospheric chemistry and aerosol formation. However, the large surface area-to-volume ratio of a chamber leads to effects that need to be accounted for in order to apply the results of chamber studies to the ambient atmosphere. These include, but are not limited to, gas-wall partitioning and particle deposition to walls, both of which can impact quantification of reaction products. Here, a low-cost vaporizer was developed to provide a means to rapidly create well-characterized organic vapors and aerosol particles inside the chamber. This in situ approach eliminates the losses to surfaces that can occur when organic gases or particles are created in a device outside the chamber and then transported inside through tubing, thus providing a simple means for achieving quantitative addition. Thermally stable volatile organic compounds can be added to the chamber within ∼1 min, which allows for accurate measurements of gas-wall partitioning timescales and equilibrium using gas chromatography. The vaporizer can also be used to create low-volatility organic aerosol particles with a mean diameter of ∼150 nm and selectable mass concentration as low as 5 µg m−3 via homogeneous nucleation within a few minutes. Such an aerosol can be used to calibrate or evaluate the performance of instruments such as the scanning mobility particle sizer in laboratory and field studies.Copyright © 2020 American Association for Aerosol Research

Native and non-native trees can find compatible mycorrhizal partners in each other’s dominated areas

Biological invasions have historically been addressed mostly from an aboveground perspective, so little is known about the impacts of belowground invasions. We studied the impact of belowground invasions on growth of native tree species and test the possibility of novel interactions between native and non-native hosts and native and non-native belowground symbionts. We combined field and growth chamber studies. With a growth chamber bioassay we compared growth and root colonization percentage of native Nothofagus and non-native invasive pine species, both highly dependent on ectomycorrhizal fungi (EMF), growing in pine invaded and non-invaded soils from native Nothofagus forest. We evaluated the identity of EMF species associated with both hosts in the different soil sources from the bioassay and we performed an in situ root sampling in the field. We found that both hosts grew equally well in both soil sources in terms of biomass, with high percent of root colonization, and no cross-host colonization of symbiotic EMF except for one species of Sistotrema found on both hosts. Soil where invasive hosts are absent is already conditioned by the presence of non-native invasive EMF. Native trees may be able to remain in the invaded area due to the presence of native EMF. The presence of native hosts is not hindering the invasion of non-native hosts and the presence of native belowground fungal mutualists seems not to hinder the spread of their non-native counterparts.

Application of Computational Fluid Dynamic Simulation for the Study of Heat Stress and Heat Strain - A Review

The study on heat stress and heat strain has been conducted since early 20th century. However, in the current years, it attracts an increase of attention around the world mainly due to the global climate change issues. Traditionally, there are two main approaches in the study of heat stress and heat strain which are the climatic chamber studies and the field studies. But, with the recent development in the computational fluid dynamic (CFD) simulation, the researchers shift toward this approach as a new method for the study of heat stress and heat strain. Climatic chamber can be simulated with various environmental parameters such as air flow and heat transfer while a manikin is used to identify the effects of these parameters. In this study, recent developments of the CFD simulation for the study of heat stress and heat strain for indoor environment are reviewed while their methodology and results are compared. The discussions that will be presented in this work will focus on the various CFD techniques and its significance as a new method for the study of heat stress and heat strain.

Polyamines and ethylene metabolism during cold acclimation in zoysiagrass (Zoysia Japonica Steud.)

Zoysiagrass (Zoysia japonica Steud.) is a warm-season turfgrass species well adapted for lawns and golf courses in transition zone and other regions with warm climates; however, it losses color and goes into dormancy in late fall and winter. The physiological mechanisms of cold acclimation (CA) have not been well understood. This growth chamber study was designed to investigate changes in leaf polyamines (PAs) and activities of selected enzymes, and ethylene production in response to CA. Leaf chlorophyll content and photosynthesis rate declined and cell membrane electrolyte leakage and malondialdehyde increased during CA. Putrescine (Put) and spermidine declined and then increased after 10 days during CA. Ethylene increases after 15 days of CA. Put biosynthesis enzymes (arginine decarboxylase, ADC, ornithine decarboxylase, ODC, s-adenosylmethionine decarboxylase), and diamine oxidases and polyamine oxidase activities increased in response to CA, except for ADC which increased after 10 days of CA. Accumulation of O2- and H2O2 in leaf tissue was observed during CA. These results suggest that PAs and ethylene are involved in CA in zoysiagrass.

Characterization of rice cultivar response to florpyrauxifen-benzyl

AbstractMany factors such as environment, herbicide rate, growth stage at application, and days between sequential applications can influence the response of a crop to herbicides. Florpyrauxifen-benzyl is a new broad-spectrum, POST herbicide that was commercialized for use in U.S. rice production in 2018. Field experiments were conducted in 2018 at the Pine Tree Research Station (PTRS) near Colt, AR, and the Rice Research and Extension Center (RREC), near Stuttgart, AR, to evaluate crop injury and yield response of three rice cultivars to sequential applications of florpyrauxifen-benzyl. Greenhouse and growth chamber experiments were conducted at the Altheimer Laboratory in Fayetteville, AR, to evaluate cultivar responses when florpyrauxifen-benzyl was applied at 30 or 60 g ae ha−1 to rice exposed to different temperature regimes or at various growth stages. Three rice cultivars were used in all experiments: long-grain variety ‘CL111’, medium-grain variety ‘CL272’, and long-grain hybrid cultivar ‘CLXL745’. CL111 exhibited sufficient tolerance to florpyrauxifen-benzyl with only 10% visible injury and no effect on yield. CL272 showed 15% injury 3 wk after the second application in the field experiment when applications were made 14 d apart. Additionally, 12% injury was observed in greenhouse studies when florpyrauxifen-benzyl was applied at 30 g ae ha−1, averaged over various growth stages at application. Florpyrauxifen-benzyl did not reduce the yield of CL272 in field experiments, indicating that CL272 can recover from florpyrauxifen-benzyl injury. As much as 64% injury was observed for CLXL745 at 3 wk after application (WAA) when sequential herbicide applications were made 4 d apart. High levels of injury occurred in the growth chamber and greenhouse studies for this cultivar as well. Sequential applications of florpyrauxifen-benzyl reduced yields of CLXL745 in nearly all treatments. Data from these experiments suggest that CL272 and CLXL745 are sensitive to sequential applications of florpyrauxifen-benzyl. Growers must follow the prescribed guidelines for using florpyrauxifen-benzyl in these cultivars and others like it.

Between-cow variation in the components of feed efficiency

A meta-analysis based on an individual-cow data set was conducted to investigate between-cow variations in the components and measurements of feed efficiency (FE) and to explore the associations among these components. Data were taken from 31 chamber studies, consisting of a total of 841 cow/period observations. The experimental diets were based on grass or corn silages, fresh grass, or a mixture of fresh grass and straw, with cereal grains or by-products as energy supplements, and soybean or canola meal as protein supplements. The average forage-to-concentrate ratio across all diets on a dry matter basis was 56:44. Variance component and repeatability estimates of FE measurements and components were determined using diet, period, and cow within experiment as random effects in mixed procedures of SAS (SAS Institute Inc., Cary, NC). The between-cow coefficient of variation (CV) in gross energy intake (GE; CV = 0.10) and milk energy (El) output as a proportion of GE (El/GE; CV = 0.084) were the largest among all component traits. Similarly, the highest repeatability estimates (≥0.50) were observed for these 2 components. However, the between-cow CV in digestibility (DE/GE), metabolizability [metabolizable energy (ME)/GE], methane yield (CH4E/GE), proportional urinary energy output (UE/GE), and heat production (HP/GE), as well as the efficiency of ME use for lactation (kl), were rather small. The least repeatable component of FE was UE/GE. For FE measurements, the between-cow CV in residual energy-corrected milk (RECM) was larger than for residual feed intake (RFI), suggesting a greater possibility for genetic gain in RECM than in RFI. A high DE/GE was associated with increased CH4E/GE (r = 0.24), HP/GE (r = 0.12), ME/GE (r = 0. 91), energy balance as a proportion of GE (EB/GE; r = 0.35), and kl (r = 0.10). However, no correlation between DE/GE and GE intake or UE/GE was observed. Increased proportional milk energy adjusted to zero energy balance (El(0)/GE) was associated with increases in DE/GE, ME/GE, EB/GE, and kl but decreases in UE/GE, CH4E/GE, and HP/GE, with no effect on GE intake. In conclusion, several mechanisms are involved in the observed differences in FE among dairy cows, and reducing CH4E yield (CH4E/GE) may inadvertently result in reduced GE digestibility. However, the selection of dairy cows with improved energy utilization efficiencies offers an effective approach to lower enteric CH4 emissions.

Kinetics of the Gas Phase Reactions of the Criegee Intermediate CH2OO with O3 and IO.

The kinetics of the gas phase reactions of the Criegee intermediate CH2OO with O3 and IO have been studied at 296 K and 300 Torr through simultaneous measurements of CH2OO, the CH2OO precursor (CH2I2), O3, and IO using flash photolysis of CH2I2/O2/O3/N2 mixtures at 248 nm coupled to time-resolved broadband UV absorption spectroscopy. Experiments were performed under pseudo-first-order conditions with respect to O3, with the rate coefficients for reactions of CH2OO with O3 and IO obtained by fitting to the observed decays of CH2OO using a model constrained to the measured concentrations of IO. Fits were performed globally, with the ratio between the initial concentration of O3 and the average concentration of IO varying in the range 30-700, and gave kCH2OO+O3 = (3.6 ± 0.8) × 10-13 cm3 molecule-1 s-1 and kCH2OO+IO = (7.6 ± 1.4) × 10-11 cm3 molecule-1 s-1 (where the errors are at the 2σ level). The magnitude of kCH2OO+O3 has a significant effect on the steady state concentration of CH2OO in chamber studies. Atmospheric implications of the results are discussed.

Early-life malnutrition causes gastrointestinal dysmotility that is sexually dimorphic.

Slow gastrointestinal (GI) transit occurs in moderate-to-severe malnutrition. Mechanisms underlying malnutrition-associated dysmotility remain unknown, partially due to lack of animal models. This study sought to characterize GI dysmotility in mouse models of malnutrition. Neonatal mice were malnourished by timed maternal separation. Alternatively, low-protein, low-fat diet was administered to dams, with malnourished neonates tested at two weeks or weaned to the same chow and tested as young adults. We determined total GI transit time by carmine red gavage, colonic motility by rectal bead latency, and both gastric emptying and small bowel motility with fluorescein isothiocyanate-conjugated dextran. We assessed histology with light microscopy, ex vivo contractility and permeability with force-transduction and Ussing chamber studies, and gut microbiota composition by 16S rDNA sequencing. Both models of neonatal malnutrition and young adult malnourished males but not females exhibited moderate growth faltering, stunting, and grossly abnormal stomachs. Progression of fluorescent dye was impaired in both neonatal models of malnutrition, whereas gastric emptying was delayed only in maternally separated pups and malnourished young adult females. Malnourished young adult males but not females had atrophic GI mucosa, exaggerated intestinal contractile responses, and increased gut barrier permeability. These sex-specific abnormalities were associated with altered gut microbial communities. Multiple models of early-life malnutrition exhibit delayed upper GI transit. Malnutrition affects young adult males more profoundly than females. These models will facilitate future studies to identify mechanisms underlying malnutrition-induced pathophysiology and sex-specific regulatory effects.

Pilot deep RNA sequencing of worker blood samples from Singapore printing industry for occupational risk assessment

Several engineered nanomaterials (ENMs) are used in toner-based printing equipment (TPE) including laser printers and photocopiers to improve toner performance. High concentration of airborne nanoparticles due to TPE emissions has been documented in copy centers and chamber studies. Recent animal inhalation studies by our group suggested exposure to laser printer-emitted nanoparticles (PEPs) increased cardiovascular risk by impairing ventricular performance and inducing hypertension and arrhythmia, consistent with global transcriptomic and metabolomic profiling results. There has been no genome-wide transcriptomic analysis of workers exposed to TPE emissions to systematically assess the occupational exposure health risks. In this pilot study, deep RNA sequencing of blood samples of workers in two printing companies in Singapore was performed. The genome-scale analysis of the blood samples from TPE exposed workers revealed perturbed transcriptional activities related to inflammatory and immune responses, metabolism, cardiovascular impairment, neurological diseases, oxidative stress, physical morphogenesis/deformation, and cancer, when compared with the control peers (office workers). Many of these disease risks associated with particle inhalation exposures in such work environments were consistent with the observation from the PEPs rat inhalation studies. In particular, the cell adhesion molecules (CAMs) was a top significantly perturbed pathway in blood samples from exposed workers compared with the office workers in both companies. The protein expression of sICAM was verified in plasma of exposed workers, showing a positive correlation with daily average nanoparticle concentration in indoor air measured in these two companies. Larger scale genomic and molecular epidemiology studies in copier operators are warranted in order to assess potential risks from such particulate matter exposures.

Development and characterisation of ibuprofen-loaded nanoemulsion with enhanced oral bioavailability

Lipophilic compounds constitute a majority of therapeutics in the pipeline of drug discovery. Despite possessing enhanced efficacy and permeability, some of these drugs suffer poor solubility necessitating the need of a suitable drug delivery system. Nanoemulsion is a drug delivery system that provides enhanced solubility for poorly soluble drugs in an attempt to improve the oral bioavailability. The purpose of this study is to develop a nanoemulsion system using ibuprofen as a model drug in order to investigate the potential of this colloidal system to enhance the absorption of poorly water-soluble drugs. Ibuprofen loaded-nanoemulsion with different drug concentrations (1.5, 3 and 6% w/w) were formulated from olive oil, sucrose ester L-1695 and glycerol using D-phase emulsification technique. A pseudoternary phase diagram was utilised to identify the optimal excipient composition to formulate the nanoemulsion system. In vitro diffusion chamber studies using rodent intestinal linings highlighted improved absorption profile when ibuprofen was delivered as nanoemulsion in comparison to microemulsions and drug-in-oil systems. This was further corroborated by in vivo studies using rat model that highlighted a two-fold increase in ibuprofen absorption when the drug was administered as a nanoemulsion relative to drug-in-oil system. On the other hand, when ibuprofen was administered as microemulsions, only a 1.5-fold increase in absorption was observed relative to drug-in-oil system. Thus, this study highlights the potential of using nanoemulsion as a drug delivery system to enhance the oral bioavailability of hydrophobic drugs.

Experimental determination of indoor air concentration of 5-chloro-2-methylisothiazol-3(2H)-one/ 2-methylisothiazol-3(2H)-one (CMIT/MIT) emitted by the use of humidifier disinfectant.

A mixture of 5-chloro-2-methylisothiazol-3(2H)-one/2-methylisothiazol-3(2H)-one (CMIT/MIT) had been used as an active ingredient in humidifier disinfectants (HDs). Owing to its high reactivity, the atmospheric concentration of CMIT/MIT, following its use in HD, would be lower than expected assuming that it is removed by ventilation only. In order to evaluate the exposure concentration of CMIT/MIT used as an HD, room-scale chamber studies were conducted under plausible use of three different HD doses at air change rates (ACR) of 0.3, 0.5, and 1.0 h−1. Atmospheric CMIT/MIT was sampled using two serial impingers containing deionized water after the attainment of steady state. Water samples in which CMIT/MIT was dissolved were concentrated using a cosolvent evaporation method with efficiencies of 35.5 and 77.9% for CMIT and MIT, respectively. The estimated air concentration, assuming that all the CMIT/MIT is absorbed in deionized water, increased linearly with increasing emission rate, but was independent of the ACR. This indicates that the removal rate of CMIT/MIT via chemical reactions is more than the removal rate by ventilation. Further investigations on homogeneous and heterogeneous chemical reactions of CMIT/MIT under ambient conditions are necessary to understand the actual exposure concentration of the mixture in HD.

Optimization of a Portable Adenosine Triphosphate Bioluminescence Assay Coupled with a Receiver Operating Characteristic Model to Assess Bioaerosol Concentrations on Site.

Rapid monitoring of the microbial content in indoor air is an important issue. In this study, we develop a method for applying a Coriolis sampler coupled with a portable ATP luminometer for characterization of the collection efficiency of bioaerosol samplers and then test this approach in field applications. The biological collection efficiencies of the Coriolis sampler and a BioSampler for collecting four different types of bioaerosols, including Escherichia coli, Staphylococcus aureus, Candida famata and endospores of Bacillus subtilis, were compared in a chamber study. The results showed that the ATP assay may indicate the four microbes’ viability, and that their defined viabilities were positively correlated with their culturability. In addition, the optimal sampling conditions of the Coriolis sampler were a 200 L/min flow rate and a sampling time of 30 min. Under these conditions, there was no significant difference in sampling performance between the BioSampler and Coriolis sampler. In field applications, the best ATP benchmark that corresponded to culturable levels of < 500 CFU/m3 was 287 RLUs (sensitivity: 100%; specificity: 80%) for bacteria and 370 RLUs (sensitivity: 79%; specificity: 82%) for fungi according to receiver operating characteristic curve analysis. Consequently, an ATP criterion is recommended for indicating whether the corresponding airborne culturable concentrations of microbes meet those of published guidelines.

The effects of energy metabolism variables on feed efficiency in respiration chamber studies with lactating dairy cows

The objective of the present study was to investigate factors related to variation in feed efficiency (FE) among cows. Data included 841 cow/period observations from 31 energy metabolism studies assembled across 3 research stations. The cows were categorized into low-, medium-, and high-FE groups according to residual feed intake (RFI), residual energy-corrected milk (RECM), and feed conversion efficiency (FCE). Mixed model regression was conducted to identify differences among the efficiency groups in animal and energy metabolism traits. Partial regression coefficients of both RFI and RECM agreed with published energy requirements more closely than cofficients derived from production experiments. Within RFI groups, efficient (Low-RFI) cows ate less, had a higher digestibility, produced less methane (CH4) and heat, and had a higher efficiency of metabolizable energy (ME) utilization for milk production. High-RECM (most efficient) cows produced 6.0 kg/d more of energy-corrected milk (ECM) than their Low-RECM (least efficient) contemporaries at the same feed intake. They had a higher digestibility, produced less CH4 and heat, and had a higher efficiency of ME utilization for milk production. The contributions of improved digestibility, reduced CH4, and reduced urinary energy losses to increased ME intake at the same feed intake were 84, 12, and 4%, respectively. For both RFI and RECM analysis, increased metabolizability contributed to approximately 35% improved FE, with the remaining 65% attributed to the greater efficiency of utilization of ME. The analysis within RECM groups suggested that the difference in ME utilization was mainly due to the higher maintenance requirement of Low-RECM cows compared with Medium- and High-RECM cows, whereas the difference between Medium- and High-RECM cows resulted mainly from the higher efficiency of ME utilization for milk production in High-RECM cows. The main difference within FCE (ECM/DMI) categories was a greater (8.2 kg/d) ECM yield at the expense of mobilization in High-FCE cows compared with Low-FCE cows. Methane intensity (CH4/ECM) was lower for efficient cows than for inefficient cows. The results indicated that RFI and RECM are different traits. We concluded that there is considerable variation in FE among cows that is not related to dilution of maintenance requirement or nutrient partitioning. Improving FE is a sustainable approach to reduce CH4 production per unit of product, and at the same time improve the economics of milk production.

Modeling microbial growth in carpet dust exposed to diurnal variations in relative humidity using the "Time-of-Wetness" framework.

Resuspension of microbes in floor dust and subsequent inhalation by human occupants is an important source of human microbial exposure. Microbes in carpet dust grow at elevated levels of relative humidity, but rates of this growth are not well established, especially under changing conditions. The goal of this study was to model fungal growth in carpet dust based on indoor diurnal variations in relative humidity utilizing the time‐of‐wetness framework. A chamber study was conducted on carpet and dust collected from 19 homes in Ohio, USA and exposed to varying moisture conditions of 50%, 85%, and 100% relative humidity. Fungal growth followed the two activation regime model, while bacterial growth could not be evaluated using the framework. Collection site was a stronger driver of species composition (P = 0.001, R 2 = 0.461) than moisture conditions (P = 0.001, R 2 = 0.021). Maximum moisture condition was associated with species composition within some individual sites (P = 0.001‐0.02, R 2 = 0.1‐0.33). Aspergillus, Penicillium, and Wallemia were common fungal genera found among samples at elevated moisture conditions. These findings can inform future studies of associations between dampness/mold in homes and health outcomes and allow for prediction of microbial growth in the indoor environment.

Aggressiveness of Fusarium species causing head blight on wheat plants determined in detached leaf and seedling in vitro assays

Fusarium head blight (FHB) is a serious disease of wheat. In vitro assays for reliable prediction of the head blight reaction in whole plant was investigated. The capacity of 16 fungal isolates of four FHB species to cause disease on individual plant organs was evaluated in vitro. Six quantitative components related to detached leaf and seedling assays were analyzed in six durum and bread wheat cultivars with known resistance. Differences in inoculated treatment were observed on young plant parts relative to water controls, indicating that these FHB species were found to be suitable for the differential expression of all tested quantitative components. There was a wide variation in aggressiveness among the 16 FHB isolates for latent period (LP) in detached leaf assay. Nevertheless, the other five components: incubation period and lesion length of detached leaf assay, percentage of infected seedlings (of foliar-spraying and pin-point inoculations) and lesion length (of clip-dipping inoculation) did not distinguish isolates. Significant correlation was found for the aggressiveness measured by LP of 16 FHB isolates and the previous pathogenic component ratings generated in vitro and in growth chamber and field study. These results suggest that LP predicts aggressiveness occurring at the earliest and latest wheat development stages during FHB infection. To our best knowledge, this is the primary in-depth report combining six different quantitative components delivered from two distinct in vitro assays to quantify aggressiveness in FHB species complex. Our data also highlighted, for the first time, the utility of LP for rapid and early determination of aggressiveness in FHB-wheat pathosystem.

Characterization of a new smog chamber for evaluating SAPRC gas-phase chemical mechanism

A new state-of-the-art indoor smog chamber facility (CAPS-ZJU) has been constructed and characterized at Zhejiang University, which is designed for chemical mechanism evaluation under well-controlled conditions. A series of characterization experiments were performed to validate the well-established experimental protocols, including temperature variation pattern, light spectrum and equivalent intensity (JNO2), injection and mixing performance, as well as gases and particle wall loss. In addition, based on some characterization experiments, the auxiliary wall mechanism has been setup and examined. Fifty chamber experiments were performed across a broad range of experimental scenarios, and we demonstrated the ability to utilize these chamber data for evaluating SAPRC chemical mechanism. It was found that the SAPRC-11 can well predict the O3 formation and NO oxidation for almost all propene runs, with 6 hr Δ(O3 – NO) model error of –3% ± 7%, while the final O3 was underestimated by ~20% for isoprene experiments. As for toluene and p-xylene experiments, it was confirmed that SAPRC-11 has significant improvement on aromatic chemistry than earlier version of SAPRC-07, although the aromatic decay rate was still underestimated to some extent. The model sensitivity test has been carried out, and the most sensitive parameters identified are the initial concentrations of reactants and the light intensity as well as HONO offgasing rate and O3 wall loss rate. All of which demonstrated that CAPS-ZJU smog chamber could derive high quality experimental data, and could provide insights on chamber studies and chemical mechanism development.

Determination of fusarium crown rot resistance in wheat to Fusarium culmorum and Fusarium pseudogramineaum using real time PCR

Wheat varieties from Turkey, Australia and the Pacific Northwest of the US were screened for resistance to Fusarium crown rot (Fusarium pseudograminearum and Fusarium culmorum) in inoculated growth chamber studies. Fungal DNA was also quantified from the lower stems (crowns) of seedlings using quantitative PCR and crown rot scores were correlated with DNA results. There were significant differences among the varieties for crown rot severity index (p = 0.0265), crown rot score (p = 0.0003), disease index on leaf sheaths (leaf sheath score) (p = 0.0013), lesion length (p = 0.0200), and plant height (p < 0.0001). The crown rot score and plant height measurements also showed that the isolate of F. culmorum was more virulent than the isolate of F. pseudograminearum. The correlations were strongest between crown rot score and DNA levels at the second harvest, and much stronger with the isolate of F. culmorum compared to the isolate of F. pseudograminearum. Some susceptible varieties such as Seri had both a high disease score and high quantities of DNA, with both F. culmorum and F. pseudograminearum. On the other hand, varieties such as Matt, Sunco and Otis showed intermediate to high crown rot scores in response to F. culmorum, but much lower levels of DNA than Seri. 2–49, Burbot-6 and CT000161, in response to F. culmorum, showed low levels of disease and low levels of DNA. In conclusion, there were examples of varieties that were resistant and tolerant (low levels of DNA and disease), resistant and intolerant (low quantities of DNA, but higher levels of disease) and susceptible and intolerant (high quantities of DNA and disease). Quantitative PCR in combination with classical phenotyping of resistance to Fusarium crown rot may provide a tool for distinguishing resistance and tolerance in breeding efforts.

Molecular Characterization of Organosulfates in Highly Polluted Atmosphere Using Ultra‐High‐Resolution Mass Spectrometry

AbstractOrganosulfates (OSs) have recently been observed to be a potentially important constituent of secondary organic aerosol (SOA); however, their molecular characterization in highly polluted atmospheres has not been probed in detail. This study thoroughly presents the characterization of OSs in polluted air and demonstrates their seasonal and diurnal variations, formation mechanisms, and contributions to organic aerosol. Atmospheric PM2.5 samples were collected from an urban Shanghai site across the winter and summer of 2017. OSs were characterized by ultra‐high‐performance liquid chromatography (UHPLC) coupled with Orbitrap mass spectrometry (MS). Based on exact mass formulae in conjunction with previous chamber studies, hundreds of sulfur‐containing compounds were tentatively identified as OSs. The number and abundance of OSs increased significantly during pollution episodes. The OSs in the clean aerosol samples were dominant in biogenic products, whereas the OSs in the polluted winter samples had distinctive anthropogenic characteristics. Aromatics and long‐chain alkanes from anthropogenic emissions might be their precursors. By using synthesized standards, the total concentrations of 14 quantified OSs ranged 21.6–161 ng m−3 in summer and 5.85–84.3 ng m−3 in winter, respectively. Among these OSs, glycolic acid sulfate was the most abundant species (1.13–122 ng m−3). Further analysis of their seasonal and diurnal variations suggests possible contributions from multiple formation mechanisms, including acid‐catalyzed and NO3‐initiated oxidation reactions. Our results highlight that increased anthropogenic pollutant emissions (e.g., NOx and SO2) can significantly enhance the SOA burden in biogenically influenced urban areas.

Smog chamber study of the effects of NOx and NH3 on the formation of secondary organic aerosols and optical properties from photo-oxidation of toluene

Secondary organic aerosols (SOAs) have been receiving significant attention because of their significant impacts on air quality and human health. In this study, the influences of nitrogen oxides (NOx) and ammonia (NH3) on SOA formation from photooxidation of toluene was investigated in the Shanghai university smog chamber. The chemical and physical characteristics of gas-phase products and SOAs from toluene photo-oxidation were characterized using laboratory-developed single photon ionization time-of-flight mass spectrometry, single particle aerosol mass spectrometry, and cavity ring-down aerosol extinction albedo spectroscopy instruments. It was observed that increasing the initial nitrogen oxides ([NOx]0) under low-[NOx]0 conditions enhanced the SOA yield, while increasing [NOx]0 under high-[NOx]0 conditions suppressed the SOA yield. After adding NH3, the number concentration, average SOA diameter, and extinction and scattering coefficients showed an immediate and rapid increase due to the formation of significant amounts of condensable ammonium nitrate and nitrogen-containing (NOC) compounds. Moreover, a simplified reaction mechanism for the photooxidation of toluene initiated by the hydroxyl radical (OH) was believed to follow two reaction channels: minor H abstraction, and major OH addition, which continuously induced the subsequent reactions. The results of this study presented rapid analytical method for the joint use of a smog chamber with on-line analytical instruments to immediately characterize the effects of SOA formation, which will help in understanding the new particle formation and particle growth, and thus provides a new insight for in-depth understanding of the haze pollution in China.