Search Results (48)

This study investigates the atmospheric formation and sinks of HONO and HNO₃ and their contribution to secondary PM_2.5 formation in Daejeon (urban) and Iksan (suburban), South Korea. Continuous observations revealed distinct concentration patterns: Iksan exhibited elevated ammonia and nitrate levels associated with agricultural activities and biomass burning, while Daejeon showed higher NOx concentrations driven by traffic and industrial sources. Positive Matrix Factorization (PMF) analysis indicated that secondary formation was the dominant contributor to PM_2.5 at both sites, with biomass burning exerting an additional influence in Iksan. Among observed precursors, HNO₃ showed the highest conversion to aerosol nitrate, highlighting aerosol-phase reactions as its primary sink, followed by dry deposition. Seasonal analysis demonstrated that HONO loss was largely controlled by photolysis in summer. Externally transported aerosols contributed more than locally formed particles at both sites, emphasizing the role of regional background pollution. These findings provide a scientific basis for region-specific air quality strategies that combine local precursor control with the management of long-range transport. Full article

The oxidization of sulfur dioxide (SO₂) occurs in the gas and liquid phase and this oxidation contributes to particulate matter and acid precipitation. The production of sulfate particles is significant because of their impact on climate, precipitation acidification, and human health. In this paper, the focus is on the oxidation of SO₂ and on the possibility of unknown heterogeneous reactions that may occur on sulfate aerosol surfaces. These results are based on the reanalysis of a foundational set of SO₂ laboratory oxidation measurements. The experiments involved two sets of photochemical studies of nitrous acid (HONO), nitrogen oxides (NO_x = NO + NO₂), SO₂, carbon monoxide (CO), and water vapor (H₂O) mixtures made in molecular nitrogen (N₂) with traces of molecular oxygen or in synthetic air. The reanalysis strongly suggests that there are uncharacterized processes for the oxidation of SO₂ that are nearly three times faster than the known gas-phase reactions. The uncharacterized processes may involve sulfate aerosol surface reactions in the presence of nitrogen oxides. If these processes can be included in current atmospheric chemistry models, greater conversion rates of SO₂ to sulfate aerosol will be calculated and this may reduce modeling bias. Full article

The study at the Peggy Guggenheim Collection in Venice highlights critical interactions between indoor air quality, visitor dynamics, and microclimatic conditions, offering insights into preventive conservation of modern artworks. By analyzing pollutants such as ammonia, formaldehyde, and organic acids, alongside visitor density and environmental data, the research identified key patterns and risks. Through three seasonal monitoring campaigns, the concentrations of SO₂ (sulphur dioxide), NO (nitric oxide), NO₂ (nitrogen dioxide), NO_x (nitrogen oxides), HONO (nitrous acid), HNO₃ (nitric acid), O₃ (ozone), NH₃ (ammonia), CH₃COOH (acetic acid), HCOOH (formic acid), and HCHO (formaldehyde) were determined using passive samplers, as well as temperature and relative humidity data loggers. In addition, two specific short-term monitoring campaigns focused on NH₃ were performed to evaluate the influence of visitor presence on indoor concentrations of the above compounds and environmental parameters. NH₃ and HCHO concentrations spiked during high visitor occupancy, with NH₃ levels doubling in crowded periods. Short-term NH₃ campaigns confirmed a direct correlation between visitor numbers and the above indoor concentrations, likely due to human emissions (e.g., sweat, breath) and off-gassing from materials. The indoor/outdoor ratios indicated that several pollutants originated from indoor sources, with ammonia and acetic acid showing the highest indoor concentrations. By measuring the number of visitors and microclimate parameters (temperature and humidity) every 3 s, we were able to precisely estimate the causality and the temporal shift between these quantities, both at small time scale (a few minute delay between peaks) and at medium time scale (daily average conditions due to the continuous inflow and outflow of visitors). Full article

The emissions of reactive nitrogen (Nr) from cropland links the pedosphere and atmosphere, playing a crucial role in the Earth’s nitrogen cycle while significantly impacting regional climate change, air quality, and human health. Among various Nr species, nitrogen oxide (NO) and nitrous acid (HONO) have garnered increasing attention as critical precursors to surface ozone (O₃) formation due to their participation in photochemical reactions. While most studies focus on Nr emissions from soils, the specific contributions of cropland Nr emissions considering planting activities to regional O₃ pollution remain insufficiently investigated. This study applied the enhanced process-based agroecological model (FEST-C*) coupled with the air quality (CMAQ) model to quantify cropland Nr emissions and assess their contributions to regional O₃ formation across China in June 2020. The simulated results indicated that the fertilizer-induced total Nr emission was estimated at 1.26 Tg in China, with NO emissions accounting for 0.66 Tg and HONO emissions for 0.60 Tg. North China was identified as a hotspot for cropland Nr emissions, contributing 43% of the national total. The peak emissions of cropland NO and HONO occurred in June, with emissions of 169 and 192 Gg, respectively. Cropland Nr emissions contributed approximately 8% to the national monthly mean MDA8 O₃ concentration, with localized enhancements exceeding 9% in agricultural hotspots in summer. North China experienced the largest MDA8 O₃ increase, reaching 11.71 μg m⁻³, primarily due to intensive fertilizer application and favorable climatic conditions. Conversely, reductions in nighttime hourly O₃ concentrations were observed in southern North China and northern Southeast China due to the rapid titration of O₃ via NO. In this study, the contributions of cropland Nr emissions to MDA8 O₃ concentrations across different regions of China have been further constrained. Incorporating cropland Nr emissions into the CMAQ model improved simulation accuracy and reduced mean biases in MDA8 O₃ predictions. This study offers a detailed quantification of the contribution of cropland Nr emissions in regional ozone formation across China and highlights the critical need to address cropland NO and HONO emissions in air quality management strategies. Full article

Background/Objectives: The translation of in vitro biomaterial evaluations into successful clinical applications often fails due to discrepancies with in vivo results. Previously, we demonstrated that differences in culture medium conditions influence the bone formation process. This study aimed to investigate the influence of culture media on gene expression during calcification induction in osteoblasts. Methods: Using MC3T3-E1 cells cultured in α Minimum Essential Medium without L-ascorbic acid (αMEM(−)) and Dulbecco’s Modified Eagle Medium (DMEM), we screened gene expression profiles through microarray analysis and validated key findings with quantitative PCR. Additionally, we compared these gene expression patterns with those in primary osteoblasts (POBs) cultured under the same medium conditions. Results: The results revealed distinct gene expression profiles in MC3T3-E1 cells depending on the culture medium, while POBs exhibited minimal differences between media, except for the gene Alpl. In αMEM(−), Alpl expression in POBs was significantly increased approximately 4-fold via calcification stimulation (p < 0.0001). POBs cultured in DMEM showed calcification appearance differing from the αMEM(−) condition, even though no significant increase in Alpl expression via calcification stimulation was observed. Conclusions: Differences in media appear to remarkably impact osteoblast gene expression and mineralization. These findings may help improve biomaterial evaluation when transitioning from in vitro assessments to in vivo evaluations. Moreover, our results suggest the possibility that gene expression differences observed in MC3T3-E1 cells reflect the diverse bone formation processes in vivo. Focusing on these genes could facilitate the development of screening methods for bone formation, supporting future clinical applications in orthopedics. Full article

Background/objectives: Negative symptoms in schizophrenia spectrum disorders are related to impaired social functioning and lower quality of life, making accurate assessment important. To date, most tools for assessing negative symptoms are observational, which can be influenced by the raters’ experience and opinion. Self-rating scales, like the Self-Evaluation of Negative Symptoms (SNS), could complement observer ratings by adding information from the patient’s perspective. Here, we aim to evaluate the psychometric properties of the Dutch translation of the SNS and the relationship between the SNS and functional outcomes. Methods: The SNS was added to the Pharmacotherapy Monitoring Outcome Survey (PHAMOUS)-protocol for adults with a DSM-5 classification of a disorder in the psychosis spectrum. Internal consistency was assessed by Cronbach’s alpha. Confirmatory factor analysis (CFA) was used to evaluate the construct validity of the five subscales of the SNS. Correlational analyses were performed between the SNS and the Positive and Negative Syndrome Scale (PANSS), the Health of Nation Outcomes Scales (HoNOS), the Global Assessment of Functioning (GAF), Functional Remission tool (FR) and the Manchester Short Assessment of Quality of Life (ManSA). Results: A total of 247 patients participated in this study. Internal consistency was good (α = 0.87). CFA confirmed the five-factor structure of the SNS. The SNS was significantly correlated (all p < 0.001) with the PANSS positive (r = 0.31), PANSS negative (r = 0.33), HoNOS (r = 0.37), FR (r = 0.27) and the ManSA (r = −0.40). Conclusions: The Dutch SNS shows good psychometric properties and is related to functional outcomes and quality of life. The SNS can be valuable in complementing current observational-based instruments, and future research may investigate whether the SNS can be used as a standalone measurement tool for the assessment of negative symptoms. Full article

This study focuses on assessing the indoor air quality in a storage room (SR) belonging to Museo Nazionale Scienza e Tecnologia Leonardo da Vinci in Milan (MUST), covering pollutants originating from outdoor sources and emissions from historical plastic objects made from cellulose acetate (CA), cellulose nitrate (CN), and urea–formaldehyde (UF) stored in metal cabinets. The concentrations of SO₂ (sulphur dioxide), NO₂ (nitrogen dioxide), NOx (nitrogen oxides), HONO (nitrous acid), HNO₃ (nitric acid), O₃ (ozone), NH₃ (ammonia), CH₃COOH (acetic acid), and HCOOH (formic acid) were determined. The concentrations of SO₂, O₃, and NOx measured inside the metal cabinets were consistently lower compared to the other sampling sites. This result was expected due to their reactivity and the lack of internal sources. The SR and metal cabinets showed similar concentrations of NO and NO₂, except for CA, where a high NO concentration was detected. The interaction between the CA surfaces and NO₂ altered the distribution of NO and NO₂, leading to a significant increase in NO. The presence of HNO₃ potentially led to the formation of ammonium nitrate, as confirmed by ER-FTIR measurements. High levels of HONO and HNO₃ in CN and NH₃ in the UF indicate object deterioration, while elevated concentrations of CH₃COOH in CA and HCOOH in the SR suggest specific degradation pathways for cellulose acetate and other organic materials, respectively. These results could direct conservators towards the most appropriate practical actions. Full article

Field studies suggest that NO₃⁻ photolysis may play a more significant role than previously thought. In this study, we concurrently measured HONO, NO₂, and NO₂⁻ in situ to gain a deeper understanding of the photogenerated HONO transfer to air and to better constrain the rate constants of NO₃⁻ photolysis. The presence of fatty acids (e.g., nonanoic acid, NA), which are naturally present in the environment, significantly increases the production of photogenerated HONO and NO₂. With an increase in oxygen percentage, the release rate of photoinduced HONO slowed, while the release rate of NO₂ accelerated. The measured $J_{{{NO}_3}^{-}}$ value averaged 1.65 × 10⁻⁵ s⁻¹, which is two orders of magnitude higher than values reported in similar systems. The HONO transfer rate from the solutions increased from 2.3 × 10⁻⁴ s⁻¹ to 5.6 × 10⁻⁴ s⁻¹ as the NA concentration increased from 0.1 to 20 mM. This can be attributed to the accumulation of NO₂⁻ induced by NA at the interface. Within this interfacial region, NO₂⁻ in the solutions becomes more prone to transfer into gaseous HONO, suggesting that photogenerated NO₂⁻ hosted in atmospheric droplets may serve as a temporary reservoir of atmospheric HONO without illumination, influencing the atmospheric oxidizing capacity in the region for hours. Therefore, simultaneous measurements of both gas and particle phase photoproducts are recommended to better constrain the rate constants of NO₃⁻ photolysis, thereby enhancing the accuracy of predicting the photochemical production of HONO in the atmosphere. Full article

This study explores the efficiency and applicability of a HONO collection system that incorporates an ultrasonic nozzle and spray chamber for the measurement of ambient air. The system demonstrates (1) a remarkable efficiency of 97.7% across two serial stages, (2) lower detection limits of 0.15 ppbv for HONO, and (3) an absence of interference from NO₂ or OH radicals. Practical ambient monitoring with the HONO collection system revealed typical diurnal variations in HONO, O₃, and HNO₃ concentrations, aligning with photolysis dynamics. Notably, HONO concentrations peaked at 0.37 ppb during nighttime and decreased to 0.27 ppb by midday. O₃ demonstrated an inverse relationship with HONO, especially during ozone depletion phases, with r² values of 0.94, 0.81, and 0.52 across various intervals. The HONO/NO_x ratio during periods of enhanced HONO suggested the presence of additional formation mechanisms beyond heterogeneous NO_x reactions. Moreover, ozone levels often fell below 20 ppb, indicating a consistent inverse correlation with HONO, thereby reaffirming further mechanisms of HONO formation beyond heterogeneous NO_x reactions. The real-time atmospheric chemical reactions involving HONO, monitored concurrently with O₃ and NO_x, were effectively validated by the HONO collection system employed in this investigation. Full article

The lack of vertical observation of reactive nitrogen oxides in agricultural areas has posed a significant challenge in fully understanding their sources and impacts on atmospheric oxidation. Ground-based multi-axis differential optical absorption spectroscopy (MAX-DOAS) observations were conducted in the agricultural regions of the North China Plain (NCP) during the summer of 2019 to measure the vertical distributions of aerosols, nitrogen dioxide (NO₂), and nitrous acid (HONO). This study aimed at revealing the spatiotemporal distribution, sources, and environmental effects of reactive nitrogen oxides in the NCP agricultural areas. Our findings indicated that the vertical profiles of aerosols and NO₂ exhibited a near-Gaussian distribution, with distinct peak times occurring between 8:00–10:00 and 16:00–18:00. HONO reached its maximum concentration near the surface around 8:00 in the morning and decreased exponentially with altitude. After sunrise, the concentration of HONO rapidly decreased due to photolysis. Additionally, the potential source contribution function (PSCF) was used to evaluate the potential sources of air pollutants. The results indicated that the main potential pollution sources of aerosols were located in the southern part of the Hebei, Shanxi, Shandong, and Jiangsu provinces, while the potential pollution sources of NO₂ were concentrated in the Beijing–Tianjin–Hebei region. At altitudes exceeding 500 m, the heterogeneous reactions of NO₂ on aerosol surfaces were identified as one of the important contributors to the formation of HONO. Furthermore, we discussed the production rate of hydroxyl radicals (OH) from HONO photolysis. It was found that the production rate of OH from HONO photolysis decreased with altitude, with peaks occurring in the morning and late afternoon. This pattern was consistent with the variations in HONO concentration, indicating that HONO was the main contributor to OH production in the agricultural regions of the NCP. This study provides a new perspective on the sources of active nitrogen in agricultural regions and their contribution to atmospheric oxidation capacity from a vertical perspective. Full article

Solar radiation triggers atmospheric nitrous acid (HONO) photolysis, producing OH radicals, thereby accelerating photochemical reactions, leading to severe secondary pollution formation. Missing daytime sources were detected in the extensive HONO budget studies carried out in the past. In the rural North China Plain, some studies attributed those to soil emissions and more recent studies to dew evaporation. To investigate the contributions of these two processes to HONO temporal variations and unknown production rates in rural areas, HONO and related field observations obtained at the Gucheng Agricultural and Ecological Meteorological Station during spring and autumn were thoroughly analyzed. Morning peaks in HONO frequently occurred simultaneously with those of ammonia (NH₃) and water vapor both during spring and autumn, which were mostly caused by dew and guttation water evaporation. In spring, the unknown HONO production rate revealed pronounced afternoon peaks exceeding those in the morning. In autumn, however, the afternoon peak was barely detectable compared to the morning peak. The unknown afternoon HONO production rates were attributed to soil emissions due to their good relationship to soil temperatures, while NH₃ soil emissions were not as distinctive as dew emissions. Overall, the relative daytime contribution of dew emissions was higher during autumn, while soil emissions dominated during spring. Nevertheless, dew emission remained the most dominant contributor to morning time HONO emissions in both seasons, thus being responsible for the initiation of daytime OH radical formation and activation of photochemical reactions, while soil emissions further maintained HONO and associated OH radial formation rates at a high level, especially during spring. Future studies need to thoroughly investigate the influencing factors of dew and soil emissions and establish their relationship to HONO emission rates, form reasonable parameterizations for regional and global models, and improve current underestimations in modeled atmospheric oxidation capacity. Full article

Nitrogen oxides (NO_X) in the atmosphere cause oxidation reactions with photochemical radicals and volatile organic compounds, leading to the accumulation of ozone (O₃). NO_X constitutes a significant portion of the NO_y composition, with nitrous acid (HONO) and nitric acid (HNO₃) following. HONO plays a crucial role in the reaction cycle of NO_X and hydrogen oxides. The majority of HNO₃ reduction mechanisms result from aerosolization through heterogeneous reactions, having adverse effects on humans and plants by increasing secondary aerosol concentrations in the atmosphere. The investigation of the formation and conversion mechanisms of HONO and HNO₃ is important; however, research in this area is currently lacking. In this study, we observed HONO, HNO₃, and their precursor gases were observed in the atmosphere using parallel-plate diffusion scrubber-ion chromatography. A 0-D box model simulated the compositional distribution of NO_y in the atmosphere. The formation reactions and conversion mechanisms of HONO and HNO₃ were quantified using reaction equations and reaction coefficients. Among the various mechanisms, dominant mechanisms were identified, suggesting their importance. According to the calculation results, the produce of HONO was predominantly attributed to heterogeneous reactions, excluding an unknown source. The sink processes were mainly governed by photolysis during daytime and reactions with OH radicals during nighttime. HNO₃ showed dominance in its production from N₂O₅, and in its conversion mechanisms primarily involving aerosolization and deposition. Full article

Soil nitrite (NO₂⁻) is an important reactive intermediate in many nitrogen transformation processes, but it is unstable under acidic conditions and may be lost as gaseous N. The canonical extraction method of soil NO₂⁻ using a potassium chloride (KCl) solution greatly underestimates its concentration. To reflect the concentration more accurately, we optimized the extraction method of soil NO₂⁻ for three agricultural soils differing in soil texture and pH, an alkalic fluvo-aquic soil and acidic Mollisol and Ultisol soils, respectively. Both extractable soil ammonium (NH₄⁺) and nitrate (NO₃⁻) were systematically investigated to optimize the simultaneous extraction of soil inorganic nitrogen. The effects of different extractants (deionized water (DIW), un-buffered 2 mol L⁻¹ KCl, and pH-buffered 2 mol L⁻¹ KCl), shaking time (10 and 30 min), and storage duration of the extracts (stored at −20 °C for 1 day, and at 4 °C for 1, 3, and 6 days) on the determination of soil inorganic nitrogen were investigated. The results showed that the un-buffered KCl extractant significantly underestimated soil NO₂⁻ concentration compared to DIW. The highest recovery of NO₂⁻ was obtained by extracting with DIW at 10 min of shaking for all three soils. Compared with DIW, the concentration of NH₄⁺ and NO₃⁻ in soil extracted from the KCl solution increased significantly. Furthermore, the soil inorganic nitrogen content of extracts stored at 4 °C for one day was closer to the direct measurements of fresh samples than with the other storage methods. Overall, the recommended analysis method for soil NO₂⁻ was extraction by DIW, shaking for 10 min, and filtering with a 0.45 µm filter, while soil NH₄⁺ and NO₃⁻ were extracted with a KCl solution and shaken for 30 min. The extract should be stored at 4 °C and analyzed within 24 h. Our study provides an efficient extraction method for soil NO₂⁻ and supports studies on the biogeochemical nitrogen cycle, e.g., in the investigation of soil nitrous acid (HONO) and nitric oxide (NO) emissions. Full article

Recent research on atmospheric particle formation has shown substantial discrepancies between observed and modeled atmospheric sulfate levels. This is because models mostly consider sulfate originating from $\mathrm{S}{\mathrm{O}}_2$ oxidation by •OH radicals in mechanisms catalyzed by solar radiation while ignoring other pathways of non-radical $\mathrm{S}{\mathrm{O}}_2$ oxidation that would substantially alter atmospheric sulfate levels. Herein, we use high-level quantum chemical calculations based on density functional theory and coupled cluster theory to show that monoethanolamine (MEA), a typical alkanolamine pollutant released from $\mathrm{C}{\mathrm{O}}_2$ capture technology, can facilitate the conversion of atmospheric $\mathrm{S}{\mathrm{O}}_2$ to sulfate in a non$–$•OH$–$radical oxidation mechanism. The initial process is the MEA-induced $\mathrm{S}{\mathrm{O}}_2$ hydrolysis leading to the formation of ${\mathrm{H}\mathrm{O}\mathrm{S}\mathrm{O}}_2^{-}$•${\mathrm{M}\mathrm{E}\mathrm{A}\mathrm{H}}^{+}$. The latter entity is thereafter oxidized by ozone (${\mathrm{O}}_3$) and nitrogen dioxide ($\mathrm{N}{\mathrm{O}}_2$) to form ${\mathrm{H}\mathrm{S}\mathrm{O}}_4^{-}$•${\mathrm{M}\mathrm{E}\mathrm{A}\mathrm{H}}^{+}$, which is an identified stabilizing entity in sulfate-based aerosol formation. Results show that the ${\mathrm{H}\mathrm{O}\mathrm{S}\mathrm{O}}_2^{-}$•${\mathrm{M}\mathrm{E}\mathrm{A}\mathrm{H}}^{+}$ reaction with ${\mathrm{O}}_3$ is kinetically and thermodynamically more feasible than the reaction with ${\mathrm{N}\mathrm{O}}_2$. The presence of an additional water molecule further promotes the ${\mathrm{H}\mathrm{O}\mathrm{S}\mathrm{O}}_2^{-}$•${\mathrm{M}\mathrm{E}\mathrm{A}\mathrm{H}}^{+}$ reaction with ${\mathrm{O}}_3$, which occurs in a barrierless process, while it instead favors HONO formation in the reaction with ${\mathrm{N}\mathrm{O}}_2$. The investigated pathway highlights the potential role alkanolamines may play in $\mathrm{S}{\mathrm{O}}_2$ oxidation to sulfate, especially under conditions that are not favorable for •OH production, thereby providing an alternative sulfate source for aerosol modeling. The studied mechanism is not only relevant to sulfate formation and may effectively compete with reactions with sulfur dioxide and hydroxyl radicals under heavily polluted and highly humid conditions such as haze events, but also an important pathway in MEA removal processes. Full article