Atmospheric Chemistry Research Articles

Large, Negative Atmospheric Carbon Monoxide Clumped Isotope Values Result From Kinetic Isotope Fractionation, Tracing OH• Reactivity

AbstractBecause of its global abundance and reactivity with hydroxyl radicals (OH•), tropospheric carbon monoxide indirectly impacts the lifetimes of other OH•‐reactive gases, in particular methane and reactive hydrocarbons. The origin and chemistry of atmospheric CO have been studied using stable isotopes. Both 13CO and C18O undergo isotopic fractionation during its main chemical loss reaction, CO + OH•. The kinetic isotope effect (KIE) for 13CO is mass dependent, with a value of ∼5‰; 12CO reacts faster than 13CO with OH. Whereas C18O + OH• exhibits an inversely mass dependent KIE ∼−10‰. We hypothesize these KIEs result in a relative depletion of 13C18O, a CO clumped isotope. To test this, we collected CO from air samples on Long Island, NY, and discovered a −3 to −8‰ difference in the clumped isotope ratio, Δ31, relative to a random distribution of 13C and 18O in CO. A clear negative trend between [CO] and Δ31 is driven by two factors: (a) the atmospheric addition of CO from either a primary or secondary source with a Δ31 of ∼0‰ and (b) the continuing reaction of CO with OH•, leaving the remaining CO pool relatively depleted in 13C18O. This is analogous to the mechanism that determines CO Δ17O values. This study is among the first to show clumped isotope fractionation resulting from atmospheric chemistry and not thermal equilibration, which may inform the identification of clumped isotope KIEs in other atmospheric trace gases. These first Δ31 observations motivate future experimental and observational studies targeted at characterizing the clumped isotopes of CO sources, background CO, and experimentally fractionated CO.

Синтез 5-амино-3-арил-1H-пиразол-4-карбонитрилов на основе гидразинов или бензгидразидов в условиях ультразвуковой активации

Pyrazoles containing amino and carbonitrile groups have a wide range of biological activities, including antimicrobial, antiinflammatory, antitumor, antioxidant, and are used to create pesticides and dyes. Also, these compounds are synthons for the preparation of various polyheterocyclic compounds. New potentially biologically active 5-amino-3-aryl-1H-pyrazole-4-carbonitriles containing pharmacophoric substituents have been obtained via three-component condensation reactions of malonic dinitrile with substituted aromatic aldehydes and benzhydrazides or hydrazines. This work considers the limits of applicability of hydrazines and hydrazides as weak nucleophiles in similar processes. The described target compounds have been synthesized using the «green chemistry» approach under ultrasonic activation in water or a mixture of water and isopropyl alcohol in the presence of triethylamine as base catalyst. The applicability of this environmentally friendly, economical and efficient approach for the synthesis of nitrogen-unsubstituted (7, 8) and N-aryl- (4, 6) or N-aroyl-substituted (1–3) pyrazole-4-carbonitriles has been demonstrated. The target pyrazole-4-carbonitrile (2) is formed and Schiff base (2’) is released as a by-product in the reaction of the weak binucleophile 3-nitrobenzhydrazide with 4-benzyloxy-3-methoxybenzaldehyde and malonic dinitrile. Step-by-step syntheses have shown that the initial reaction of a three-component interaction can be either croton condensation or the formation of a Schiff base. In any case, during subsequent heterocyclization, unstable substituted pyrazolines are formed, which aromatize to the target pyrazoles in the presence of atmospheric oxygen under synthesis conditions. The composition and structure of the products have been confirmed by elemental analysis, NMR 1H, 13C spectroscopy, HSQC, and HMBC heteronuclear correlations.

Reliable plasmonic biosensing with atmospheric pressure dielectric barrier discharge oxygen plasma treated polydimethylsiloxane microfluidic channels

Polydimethylsiloxane (PDMS) has emerged as a popular choice of material for many microfluidic and flexible sensing devices despite its inherent hydrophobic nature. Here, we report on the use of atmospheric pressure dielectric barrier discharge (APDBD) oxygen (O2) plasma in the development of hydrophilic and protein repulsive PDMS microchannels for plasmonic sensing application. The effect of plasma treatment on the wettability, surface energy and hydrophilicity retention capacity of PDMS was determined using contact angle measurements. The PDMS sample exposed to low-power DBD O2 plasma for 6 min demonstrated lowest contact angle of 35.15˚, surface energy of 62.83 mN/m and hydrophilicity retention capacity of more than 50 days in Phosphate Buffered Saline (PBS). The treatment of PDMS with plasma induces surface hydrophilicity due to the introduction of polar functional groups as evinced by Fourier Transform Infrared (FTIR) analysis without compromising the bulk structure and optical properties of PDMS which were confirmed by X-Ray Diffraction (XRD) and Ultraviolet-visible (UV-Vis) Spectroscopic measurements. The plasma treated PDMS was used in the construction of a microfluidic Surface Plasmon Resonance (SPR) biosensor which demonstrated very low detection limits of 7.13 ng/ml, 5.91 ng/ml and 1.47 ng/ml and high sensitivities of 16.8˚/(µg/ml), 13.5˚/(µg/ml) and 16.65˚/(µg/ml) against anti-Human Immunoglobulin-G protein raised in mouse, goat and rabbit respectively. The obtained results infer that APDBD O2 plasma is a promising technique to render PDMS hydrophilic suited for reliable microfluidic based plasmonic biosensing applications.

Disentangling the effects of meteorology and emissions from anthropogenic and biogenic sources on the increased surface ozone in Eastern China

China's Clean Air Actions have substantially improved ambient PM2.5 air quality since 2013. However, ozone (O3) pollution in urban areas has worsened in recent years, particularly in the eastern region. The formation of O3 in these high emission areas is highly complex and regulated by numerous factors. Utilizing the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem), this study conducted a comprehensive analysis through nine sensitivity experiments for the years 2013 and 2017, aimed at disentangling the relative contributions of major factors (e.g., meteorological factors, anthropogenic emissions, biogenic emissions, and aerosol feedback mechanisms) to the observed O3 concentration trends in Jiangsu, a developed region of China with increasing trend of O3 level. Our findings indicate a pronounced increase in mean daily maximum 8-h average (MDA8) O3 levels in the economically vibrant southern Jiangsu, contrasted with a decrease in the less developed northern regions. The study identifies anthropogenic emissions change as the primary driver of O3 variations, with significant impacts also attributed to meteorological conditions and aerosol feedback effects, while biogenic emission shifts play a lesser role. In terms of meteorological factors, we discovered that the alteration in meteorological thermal factors (enhanced solar radiation and temperatures) in 2017, compared to 2013, exerted a more pronounced influence on the formation of O3 than the change in thermally driven dynamic factors (boundary layer height and wind speed). Moreover, the study observes a shift in O3 formation sensitivity from VOC-sensitive to transitional or NOX-sensitive regimes, signifying a notable transformation in the regional atmospheric chemistry conducive to O3 generation. Aerosol feedback effects, through complex pathways including photolysis rate alterations and modifications in the vertical O3 distribution, further compound the challenge of mitigating O3 levels. Our research underscores the necessity for adaptive, region-specific strategies to mitigate O3 pollution, providing potential insights for policymakers to formulate effective control measures.

Catalyst-Free Oxidation of Styrene to Styrene Oxide Using Circulating Microdroplets in an Oxygen Atmosphere.

Water microdroplets possess unique interfacial properties that enable chemical reactions to occur spontaneously and increase the reaction rate by orders of magnitude. In this study, water containing styrene (SY) was cyclically sprayed into the air to form microdroplets with an average diameter of 6.7 μm. These microdroplets allowed SY to be oxidized into styrene oxide (SO) without catalysts. No oxidation products of SY were observed in the bulk solution under the same conditions, while in microdroplet reactions 4.2% conversion of SY with approximately 3.1 mM SO was detected. Compared with the traditional spraying microdroplet method, the oxidation product concentration was enhanced by 1000 times. Experiments proved that an aerobic environment boosts SY oxidation, leading to a proposed dual-path hydrogen peroxide (H2O2) oxidation mechanism at the droplet interface. This was confirmed by density functional theory calculations (DFT). Furthermore, in the presence of additional ultrasound, the SY oxidation process initiated by water droplets can be further enhanced, and 7.0% conversion of SY with approximately 5.2 mM SO was detected. The cyclic spraying method greatly enhanced the oxidation product concentration, showing the potential for large scale chemical production using microdroplets.

Anthropic-Induced Variability of Greenhouse Gasses and Aerosols at the WMO/GAW Coastal Site of Lamezia Terme (Calabria, Southern Italy): Towards a New Method to Assess the Weekly Distribution of Gathered Data

The key to a sustainable future is the reduction in humankind’s impact on natural systems via the development of new technologies and the improvement in source apportionment. Although days, years and seasons are arbitrarily set, their mechanisms are based on natural cycles driven by Earth’s orbital periods. This is not the case for weeks, which are a pure anthropic category and are known from the literature to influence emission cycles and atmospheric chemistry. For the first time since it started data gathering operations, CO (carbon monoxide), CO2 (carbon dioxide), CH4 (methane) and eBC (equivalent black carbon) values detected by the Lamezia Terme WMO/GAW station in Calabria, Southern Italy, have been evaluated via a two-pronged approach accounting for weekly variations in absolute concentrations, as well as the number of hourly averages exceeding select thresholds. The analyses were performed on seven continuous years of measurements from 2016 to 2022. The results demonstrate that the analyzed GHGs (greenhouse gasses) and aerosols respond differently to weekly cycles throughout the seasons, and these findings provide completely new insights into source apportionment characterization. Moreover, the results have been combined into a new parameter: the hereby defined WDWO (Weighed Distribution of Weekly Outbreaks) normalizes weekly trends in CO, CO2, CH4 and eBC on an absolute scale, with the scope of providing regulators and researchers alike with a new tool meant to better evaluate anthropogenic pollution and mitigate its effects on the environment and human health.

Emissions of gaseous nitrous acid (HONO) from diesel trucks: Insights from real-driving emission experiments

Nitrous acid (HONO) serves as a substantial contributor in the atmospheric chemistry of hydroxyl radicals (·OH). Despite its significance, the primary sources of atmospheric HONO, particularly diesel truck emissions, have not been thoroughly examined. This study investigated the factors influencing HONO emissions via on-road exhaust emission tests using a self-developed portable measurement system. The findings show that the HONO emissions measured during on-road testing are higher than those measured during chassis dynamometer testing, highlighting the need for on-road tests to capture HONO emissions. Emission standards and truck types greatly influence HONO emission factors (EFs), with stricter regulations leading to lower emissions. The average fuel consumption-based EFs for light-duty diesel trucks ranged from 0.93 g/kg for China III to 0.08 g/kg for China VI. For medium-duty diesel trucks, the EFs decrease from 1.43 g/kg for China III to 0.19 g/kg for China V. Moreover, the vehicle-specific power demonstrated a stronger correlation with HONO emissions. This research showed that HONO emissions were significantly higher without or before the optimal operation of the SCR device, and the device notably reduced HONO emissions. Future research should focus on the impact of various exhaust after-treatment systems and explore HONO conversion mechanisms.

Carbonyl Compounds Regulate Atmospheric Oxidation Capacity and Particulate Sulfur Chemistry in the Coastal Atmosphere.

Carbonyl compounds play a crucial role in the formation of ozone (O3) and secondary aerosols, with recent studies particularly highlighting formaldehyde (HCHO) as a significant contributor to the missing particulate sulfur. However, evaluations based on field observations are limited, especially in clean marine environments. Utilizing observation data from a coastal mountain site in May 2021 in Qingdao, northern China, we reveal the important regulating effect of carbonyls in atmospheric oxidation capacity and particulate sulfur chemistry using detailed chemical box models. Photolysis of gaseous carbonyls accounted for >90% and >60% of the primary sources of HO2 and RO2, respectively, contributing 38% of net O3 production. Notably, HCHO alone constituted 80% of the primary HO2 and 15% of net O3 production. Using a multiphase model with updated HCHO-related chemistry, we determine that HCHO chemistry can account for up to 30% of total particulate sulfur (the sum of hydroxymethanesulfonate and sulfate) and address more than one-third of the simulated sulfate gap. The emission-based multiphase model indicates that the HCHO-related pathway remains significant and can account for 20% of the particulate sulfur under clean marine conditions. These findings underscore the importance of carbonyls, particularly HCHO, in regulating the atmospheric oxidation capacity and particulate sulfur chemistry in the marine atmosphere, urging further laboratory studies on chemical kinetics and field measurements of particle-phase carbonyls.

An innovative soil mesocosm system for studying the effect of soil moisture and background NO on soil surface C and N trace gas fluxes

Nitric oxide (NO) is a key substance in atmospheric chemistry, influencing the formation and destruction of tropospheric ozone and the atmosphere's oxidizing capacity. It also affects the physiological functions of organisms. NO is produced, consumed, and emitted by soils, the effects of soil NO concentrations on microbial C and N cycling and associated trace gas fluxes remain largely unclear. This study describes a new automated 12-chamber soil mesocosm system that dynamically changes incoming airflow composition. It was used to investigate how varying NO concentrations affect soil microbial C and N cycling and associated trace gas fluxes under different moisture conditions (30% and 50% WFPS). Based on detection limits for NO, NO2, N2O, and CH4 fluxes of < 0.5 µg N or C m−2 h−1 and for CO2 fluxes of < 1.2 mg C m−2 h−1, we found that soil CO2, CH4, NO, NO2, and N2O were significantly affected by different soil moisture levels. After 17 days cumulative fluxes at 50% WFPS increased by 40, 400, and 500% for CO2, N2O, and CH4, respectively, when compared to 30% WFPS. However, cumulative fluxes for NO, and NO2, decreased by 70, and 40%, respectively, at 50% WFPS when compared to 30% WFPS. Different NO concentrations tended to decrease soil C and N fluxes by about 10–20%. However, with the observed variability among individual soil mesocosms and minor fluxes change. In conclusion, the developed system effectively investigates how and to what extent soil NO concentrations affect soil processes and potential plant–microbe interactions in the rhizosphere.

Diversity of ammonia sources in Tianjin: nitrogen isotope analyses and simulations of aerosol ammonium

Environmental context Atmospheric particulate NH4+, primarily produced from the reaction of NH3 and acids, is an important component of PM2.5. In this study, nitrogen stable isotope analyses and an atmospheric chemistry model were used to estimate the contribution of major NH3 sources to particulate NH4+ in Tianjin, a megacity in North China Plain (NCP). Our research has implications for investigations of NH3 emission sources and relevant pollution control in Tianjin and NCP. Rationale The North China Plain (NCP) has been identified as an NH3 emission hotspot. Source apportionment of NH3 is a prerequisite for controlling NH3 or NH4+ pollution. Nitrogen stable isotope (δ15N) analysis is a promising method for NH3 source apportionment but its accuracy is still in question. Methodology In this study, daytime and nighttime PM2.5 samples were collected from two sites in Tianjin, NCP, in autumn. Concentrations and δ15N of particulate NH4+ were then measured. Nitrogen stable isotope analyses and isotope mixing model (MixSIAR), and an atmospheric chemistry model (WRF-CMAQ-ISAM) were used to estimate the sources of NH3 in Tianjin. Results Results from the MixSIAR and WRF-CMAQ-ISAM models suggested that all the sources including livestock breeding, N-fertiliser application, fossil fuels, NH3 slip (especially from traffic), human waste and biomass burning (mostly from bioapplication) were non-negligible to NH3 and NH4+ in Tianjin. This high complexity is due to significant agricultural and industrial production and residential life in Tianjin and the surrounding regions. Our results indicate all NH3 sources need to be considered if we want to reduce NH4+ pollution in Tianjin in autumn.

Rapid cycling and emission of volatile sulfur compounds in the eastern Indian Ocean: Impact of runoff inputs and implications for balancing atmospheric carbonyl sulfide budget

Volatile sulfur compounds, such as dimethyl sulfide (DMS), carbonyl sulfide (OCS), and carbon disulfide (CS2), significantly influence atmospheric chemistry and climate change. Despite the oceans being an important source of these sulfides, the limited understanding of their biogeochemical cycles in seawater introduces considerable uncertainties in quantifying their oceanic emissions and assessing atmospheric OCS budgets. To address this issue, we conducted a comprehensive field survey in the tropical eastern Indian Ocean (EIO) to examine the spatial distributions, source-sink dynamics, and sea-air exchange fluxes of marine DMS, OCS, and CS2. Our study indicates that nutrients, organic matter, and freshwater input from terrestrial runoff significantly affect most of the source-sink processes of these sulfides in the Bay of Bengal and even the tropical EIO. The resulting sulfide accumulation in seawater combined with high wind speeds establishes the tropical EIO as a considerable direct and indirect atmospheric OCS source. These insights underscore the potentially critical role of marine environments influenced by runoff in contributing to the atmospheric OCS budget. However, by integrating these results with previous field surveys, we believe that actual OCS emissions from tropical oceans exceed some bottom-up box-model simulations, yet fall significantly below those predicted by top-down models, still insufficient to bridge the atmospheric OCS source gap. Our detailed examination of source-sink dynamics offers deeper insights into the marine sulfur cycle and has potential implications for refining future box-models, thus mitigating uncertainties in estimating marine sulfur emissions.

Rapid Detection of Trace Organic Amines in Seawater: An Innovative Approach Using Photoelectron-Induced Chemical Ionization TOFMS with Online Derivatization and Dynamic Purging-Release Techniques.

Organic amines (OAs) have gained substantial interest in atmospheric chemistry due to their distinctive acid-base neutralization characteristics for secondary organic aerosols and new particle formation. To address the need for sensitive and online analysis of OAs, including dimethylamine (DMA), diethylamine (DEA), trimethylamine (TMA), and triethylamine (TEA), in seawater, a home-built photoelectron-induced chemical ionization TOFMS, coupled with online derivatization and dynamic purge-release apparatus, has been developed. Sodium hypochlorite is used to derivatize high-solubility DMA and DEA, substituting hydrogen atoms with chlorine atoms to obtain more volatile derivatives, [DMA-H + Cl] and [DEA-H + Cl]. Sodium carbonate is used to reduce the solubility of the OAs in solution to enhance detection sensitivity. Microbubbles generated from 250 to 300 mL/min of zero air at the gas-liquid interface efficiently transfer dissolved OAs into the gas phase. Water vapor in the purged gas is ionized by photoelectrons to form (H2O)n·H+, which ionizes OAs and their derivatives to produce characteristic ions [OAs + H]+ or [OAs-H + Cl]·H+ characteristic ion. After optimizing the experimental conditions, the limits of quantification (S/N = 10) of the four OAs including DMA, DEA, TMA, and TEA can be as low as 1.1 0.68, 0.85, and 0.49 nmol/L, respectively within a 5 min analysis time, using only 5 mL of seawater sample. This method enhances sensitivity by over 5-fold and reduces analysis time to 21.7%, respectively, compared with conventional methods. Subsequently, this method was successfully applied to quantify 15 seawater samples from 5 typical marine environments, which demonstrates its practicability and reliability for analysis of trace amines in seawater.

Effect of cloud chemistry on seasonal variations of sulfate and its precursors in China

Cloud chemistry is of paramount importance in the secondary production of atmospheric aerosols, influencing the spatial-temporal distribution of gases and aerosols in the atmosphere. Using WRF/CUACE (China Meteorological Administration Unified Atmospheric Chemistry Environment), this study assesses the seasonal impacts of cloud chemistry on the concentrations of SO2, sulfate, as well as two oxidizers, H2O2 and O3, in the most east-central areas of China, including four key pollution zones (the North China Plain (NCP), the Yangtze River Delta (YRD), the Pearl River Delta (PRD), and the Sichuan Basin (SCB)). Near the surface, H2O2-oxidation was the dominant pathway for cloud chemistry in four key pollution zones in four seasons. H2O2 consumption is most pronounced in summer, especially in the SCB and NCP, while O3 consumption peaks in autumn, particularly in the PRD and southeastern coastal areas. While at higher altitudes, oxidation by O3 and H2O2 is compatible with the cloud chemistry process. Near the surface, cloud chemistry consumes SO2 ranging from approximately 0.1 ppb–5.0 ppb, resulting in the generation of about 6.0–25.0 μg m−3 of sulfate. Higher SO2 reduction and sulfate increase are in both summer and winter, especially for the SCB and NCP in summer, and the SCB in winter. Vertically, the cloud chemistry process primarily concentrates its influence on SO2 and sulfate concentrations below 5 km, particularly within the turbulent zone of the troposphere below 2 km in all the four pollution zones and four seasons. The most notable seasonal variation occurs in the NCP compared to other zones. This study also shows that cloud chemistry effectively improves the seasonal simulation accuracy of SO2 and sulfate, resulting in improved correlation and a notable reduction in RMSE.

Quantification of persulfidation on specific proteins: are we nearly there yet?

Hydrogen sulfide (H2S) played a pivotal role in the early evolution of life on Earth before the predominance of atmospheric oxygen. The legacy of a persistent role for H2S in life's processes recently emerged through its discovery in modern biochemistry as an endogenous cellular signalling modulator involved in numerous biological processes. One major mechanism through which H2S signals is protein cysteine persulfidation, an oxidative post-translational modification. In recent years, chemoproteomic technologies have been developed to allow the global scanning of protein persulfidation targets in mammalian cells and tissues, providing a powerful tool to elucidate the broader impact of altered H2S in organismal physiological health and human disease states. While hundreds of proteins were confirmed to be persulfidated by global persulfidome methodologies, the targeting of specific proteins of interest and the investigation of further mechanistic studies are still underdeveloped due to a lack of stringent specificity of the methods and the inherent instability of persulfides. This review provides an overview of the processes of endogenous H2S production, oxidation, and signalling and highlights the application and limitations of current persulfidation labelling approaches for investigation of this important evolutionarily conserved biological switch for protein function.

Highly efficient recovery of lithium from spent ternary NCM cathode materials via a selective chlorination method

The recovery of lithium from spent lithium-ion batteries (LIBs) is an important approach to solve the global shortage of lithium resource. Considering the difference in stability of various metal element chlorides in Ni-Co-Mn ternary (NCM) cathode materials, lithium element was selectively and high-efficiently extracted from spent ternary NCM cathode material by ammonium chloride roasting in oxygen atmosphere followed by water leaching. The effects of roasting temperature, roasting time, and NH4Cl dosage on lithium leaching efficiency and selectivity were systematically investigated. In addition, the conversion mechanism during chloride roasting was discussed in detail in conjunction with thermodynamic analysis as well as structural and compositional characterizations. After roasting with NH4Cl in oxygen atmosphere at 600°C, the spent NCM cathode material was thoroughly decomposed and converted into mixture of LiCl, NiO, and MnCo2O4. Due to the high aqueous solubility of LiCl, more than 95 % of the lithium in the mixture was leached in ∼30 minutes at room temperature, and Li2CO3 with a purity of 99.40 % can be obtained in the subsequent recovery process. This simple and efficient method can be generally useful for the recovery of a wide range of spent cathode materials and provide inspiration for the lithium recovery process of spent LIBs.

Kinetic Study of OH Radical Reactions with Cyclopentenone Derivatives.

We investigated the reactions of the hydroxyl radical (OH) with cyclopentenone derivatives and cyclopentanone in a quasi-static reaction cell at 4 Torr across a 300-500 K temperature range. The OH radicals were generated using pulsed laser photolysis of hydrogen peroxide vapors, and the ketone reactants were introduced in excess. The relative concentrations of the radicals were monitored as a function of reaction time using laser-induced fluorescence. At room temperature, the reaction rate coefficients were measured to be 1.2(±0.1) × 10-11 cm3 s-1 for reaction with 2-cyclopenten-1-one (R1); 1.7(±0.2) × 10-11 cm3 s-1 for reaction with 2-methyl-2-cyclopenten-1-one (R2); and 4.4(±0. 7) × 10-12 cm3 s-1 for reaction with 3-methyl-2-cyclopenten-1-one (R3). Over the experimental temperature range, the rate coefficients can be fitted with the modified Arrhenius expressions k1(T) = 1.2 × 10-11 (T/300)0.26 exp (6.7 kJ mol-1/R {1/T - 1/300}) cm3 s-1, k2(T) = 1.7 × 10-11 (T/300)6.4 exp (27.6 kJ mol-1/R {1/T - 1/300}) cm3 s-1, k3(T) = 4.4 × 10-12 (T/300)17.8 exp (57.8 kJ mol-1/R {1/T - 1/300}) cm3 s-1. In the cases of 2-cyclopenten-1-one and 2-methyl-2-cyclopenten-1-one, the temperature dependence of the rate coefficients is similar to that calculated or measured for noncyclic conjugated ketones. We also found that the reaction with 3-methyl-2-cyclopenten-1-one was slower, with rate coefficients similar to those measured for the reaction with the saturated cyclic ketone cyclopentanone. To discuss the experimental data, we use potential energy surfaces (PES) calculated at the CCSD(T)/cc-pVTZ//M06-2X/6-311+G** level of theory. RRKM-based Master equation calculations were also performed to infer the most likely reaction products over a wide range of temperatures and pressures. We suggest that both abstraction and addition mechanisms contribute to the overall OH removal, forming radical products stabilized by resonance. We also discuss the relevance for combustion and atmospheric chemistry.

Melanin and Light.

Melanin is responsible, in Nature, for photoprotection, for this reason it is expected to be poorly photoreactive. However, the photo-reactivity of melanin and related materials is well documented. Here we discuss some relevant recent examples to demonstrate that, indeed, the actual mechanism of interaction of melanin with light is complex and still not completely understood. Photochemical and photothermal processes are involved, giving a contribution that strongly depends on light wavelength and intensity. Moreover, some interesting experiments demonstrated that photochemical reactivity of melanin related compounds is likely to be indirect, in the sense that the effect of light is to increase the number of radical species rather than creating photoreactive excited state. These suggestions open-up new perspectives in the interpretation of the role of melanin in photoprotection and in the design of new melanin based photoactive materials for energy conversion, environmental remediation, and nanomedicine. Further complication is given by the role of atmospheric oxygen and humidity in the photoinduced processes. Beside this complexity of behavior makes it difficult a systematic understanding of the interaction of melanin with light, it surely strongly contributes to make the properties of melanin and related materials unique.

Thermal Decomposition of Hematite Ore Fines in Air

Thermal decomposition of hematite plays an important role during pelletization and the iron fine‐based smelting processes such as HIsarna and flash shaft smelter. The temperature at which pure hematite decomposition occurs depends on the partial pressure of oxygen in the gaseous atmosphere. In the air, that is, at = 0.21, the hematite decomposes at 1386 °C. In the present work, for an ore of a given composition, the effect of gangue on the thermal decomposition of hematite is experimentally determined using thermogravimetric analysis (TGA). A decomposition temperature of 1320 °C is found in the platinum crucible after analyzing the TGA curve. Thermodynamic calculations have been carried out using FactSage8.1 to investigate the effect of gangue on the stability of hematite. Thermodynamics calculations confirm that the hematite present in the ore decomposes at a lower temperature with the increase in the gangue content. Additionally, if gangue content can affect the temperature at which dissociation of hematite occurs, it is expected that the crucible material can also affect the dissociation. Interestingly most of the reported TGA experiments are performed either in alumina crucibles or it was not reported in the literature. Therefore, the effect of crucible materials, namely alumina and platinum, is also investigated.

Monthly Characteristics and Source–Receptor Relationships of Anthropogenic Total Nitrate in Northeast Asia

The complex nonlinear characteristics of atmospheric chemistry necessitate the development of new methods for calculating source–receptor (S–R) relationships for secondary air pollutants. In this study, the monthly characteristics and S–R relationships of anthropogenic total nitrate (i.e., the sum of N from nitric acid, inorganic nitrate, and peroxyacetyl nitrate) in Northeast Asia were simulated and analyzed. The Community Multiscale Air Quality (CMAQ), Fifth-Generation NCAR/Penn State Mesoscale (MM5), and Sparse Matrix Operator Kernel Emissions (SMOKE) models were employed for air quality modeling, meteorological fields, and emissions processing, respectively. The study area encompassed Republic of Korea, Japan, and most of China. Five source/receptor regions were defined to derive the S–R relationships: three in China, one in Republic of Korea, and one in Japan. To produce data for the calculation of the S–R relationship, several experiments were conducted with a 20% reduction in NOx emission sources. As a result of the S–R relationships, China was rarely impacted by the other two countries. The total depositions in other countries were significantly dominated by China (i.e., 43.5% and 40.7% in Republic of Korea and Japan, respectively, and up to 82.3% in December for Republic of Korea).

PSIV-24 Evaluation of different colostrum feeding volumes on serum immunoglobulin G concentration and metabolic profiles of calves in high altitude area

Abstract Qinghai-Tibet Plateau is the highest plateau in the world, reputed as “the roof of the world” and “the world’s third pole”. Its ecological environment is characterized by low atmospheric oxygen pressure, cold, and limited feed supplies. This study aimed to investigate the serum immunoglobulin G (IgG) concentration and metabolic profiles of calves in high altitude area (3,650 m) fed different volumes of colostrum [8, 12, or 15% of birth body weight (BW)] using untargeted metabolomics strategies. Neonatal Holstein hybrid heifer calves (n = 44) were randomly divided into 1 of the 3 colostrum feeding amounts: 8% of birth BW (Low volume, L), 12% of birth BW (Middle volume, M), and 15% of birth BW (High volume, H) in colostrum. To safeguard the efficiency of colostrum intake, the colostrum was fed to calves within 0.5 h and 6 h after birth. The serum samples at 24 h after birth were collected for IgG concentration determination by indirect enzyme-linked immunosorbent assay (ELISA) and for LC-MS/MS metabonomic analysis. As the volumes of colostrum increased, there was a linearly increased in the serum IgG concentration (P &amp;lt; 0.01). Differential metabolites were selected according to the following 3 conditions: minimum fold change (FC) &amp;gt; 2, P-value &amp;lt; 0.01 in single-dimensional statistical analysis, and variable importance in projection (VIP) &amp;gt; 1 in the OPLS-DA model. Multivariate statistical analyses were performed to visualize differences among groups. Based on the screening criteria, a total of 3 differential metabolites (22 alpha-Hydroxy-campesterol, N-Myristoyl Histidine, and Calcitetrol) were detected between L and M, of which all differential metabolites were down-regulated. Six differential metabolites were detected between M and H, of which PC[P-18:1(11Z)/18:1(12Z)-2OH(9,10)] was up-regulated and 5 differential metabolites including 1-arachidonoyl-2-hydroxy-sn-glycero-3-phosphate, propanoyl phosphate, ascorbic acid 6-palmitate, 20-hydroxyecdysone, and 6’’’-deamino-6’’’-hydroxyparomomycin II were down-regulated. There were 28 differed metabolites (including leucyl-tryptophan, calcitetrol, 3’’-Oxoribostamycin) between L and H, of which 9 differential metabolites were up-regulated and 19 differential metabolites were down-regulated (Figure 1). Based on KEGG metabolic enrichment pathway analysis and pathway topology analysis, porphyrin metabolism was identified as the most impacted pathway between L and H (Figure 2). In conclusion, increasing colostrum volumes significantly increased serum IgG concentrations at 24 h after birth, favoring the success of the transfer of passive immunity. Alterations in serum metabolome of calves in the Qinghai-Tibet Plateau fed different volumes of colostrum were successfully revealed by untargeted metabolomics. The role of the identified differential metabolites and enriched pathway in the transfer of passive immunity in calves at high altitude deserves further investigation. Keywords: calf, colostrum volumes, high altitude area