Estimating the probability of occurrence of African dust outbreaks over regions of the western Mediterranean basin from thermodynamic atmospheric parameters

Desert dust is currently recognized as a health risk factor. Therefore, the World Health Organization (WHO) is actively promoting the establishment of early warning systems for sand and dust storms. This study introduces a methodology to estimate the probability of African dust outbreaks occurring in eight different regions of the Iberian Peninsula and the Balearic Islands. In each region, a multilinear regression model was developed to calculate daily probabilities of dust events using three thermodynamic variables (geopotential thickness in the 1000-500 hPa layer, mean potential temperature between 925 and 700 hPa, and temperature anomalies at 850 hPa) as assessment parameters. All days with African dust transport over each study region were identified in the period 2001-2021 using a proven procedure. This information was then utilized to establish a functional relationship between the values of the thermodynamic parameters and the probability of African dust outbreaks occurring. The validation of this methodology involved comparing the daily probabilities of dust events generated by the models in 2001-2021 with the daily African dust contributions to PM10 regional background levels in each region. On average, daily dust contributions increased proportionally with the increase in daily probabilities, reaching zero for days with low probabilities. Furthermore, a well-defined seasonal evolution of probability values was observed in all regions, with the highest values in the summer months and the lowest in the winter period, ensuring the physical relevance of the models' results. Finally, upward trends were observed in all regions for the three thermodynamic parameters over 1940-2021. Thus, the probability of dust events development also increased in this period. It demonstrates that the aggravation of warm conditions in southern Europe in the last decades, have modified the frequency of North-African dust outbreaks over the western Mediterranean basin.

Air quality and characterization of synoptic circulation weather patterns in a South American city from Argentina

The potential cause-effect relationship between synoptic meteorological conditions and levels of criteria air pollutants, including CO, NO2, O3, PM10, PM2.5 and SO2, in Bahia Blanca, Argentina, was assessed for the period of 2018-2019. Daily back-trajectories and global meteorological data fields were employed to characterize the primary transport paths of air masses reaching the study site, and to identify the synoptic meteorological patterns responsible for these atmospheric circulations. Time series of surface-level meteorological parameters and midday mixing layer height were collected to examine the impact of the synoptic meteorological patterns on local meteorology. Furthermore, the NAAPS global aerosol model was utilized to identify days when contributions from long-range transport processes, such as dust and/or biomass burning smoke, impacted air quality. By applying this methodology, it was determined that the air masses coming from the N, NW and W regions significantly contributed to increased mean concentrations of coarse particles in this area through long-range transport events involving dust and smoke. Indeed, the high average levels of PM10 recorded in 2018-2019 (annual mean values of 47 and 52 μg/m3, respectively) represent the main air quality concern in Bahía Blanca. Moreover, PM10, PM2.5 and NO2 emissions should be reduced in order to meet recommended air quality guidelines. On the other hand, the results from this study suggest that the sources and meteorological processes leading to the increase in the concentrations of CO and SO2 have a local-regional origin, although these air pollutants did not reach high values probably as a consequence of the strong wind speed registered in this region during any synoptic meteorological pattern.

Influence of synoptic meteorology on airborne allergenic pollen and spores in an urban environment in Northeastern Iberian Peninsula

The influence of the most frequent patterns of synoptic circulation on the dynamics of airborne pollen/spores recorded at the Barcelona Aerobiological Station (BCN) was analysed. Six pollen types (Platanus, Cupressaceae, Olea, Poaceae, Urticaceae and Amaranthaceae), and one fungal spore (Alternaria) were selected for their high allergenic effect in sensitive people. Six synoptic meteorological patterns were identified through cluster analysis of sea level pressure fields as the main responsible of the weather conditions in the Iberian Peninsula. The local meteorological conditions in Barcelona associated with each one of the synoptic types were also stablished. Different statistical methods were applied to analyse possible relationships between concentrations and timing of the recorded aerobiological particles and specific synoptic types. The study, focused in the 19-year period 2001-2019, shows that one of the scenarios, frequent in winter and linked to high stability and air-mass blockage, registered the highest mean and median values for Platanus and Cupressaceae, but it was not very relevant for the other taxa. It was also this scenario that turned out to be the most influent on the pollination timing showing a significant influence on the start occurrence of Urticaceae flowering and on the peak date of Platanus. On the other hand, the most frequent synoptic type in the period, relevant in spring and summer, was linked to sporadic episodes of levels considered to be of high risk of allergy to Platanus, Poaceae, and Urticaceae pollen, and Alternaria fungal spore. This synoptic pattern, characterized by the presence of the Azores anticyclone and the Atlantic low located in the north of the United Kingdom, was associated with high temperatures, low relative humidity and moderate winds from the NW in Barcelona. The identification of an interaction between synoptic meteorology and pollen/spore dynamics will allow better abatement measures, reducing adverse health effects on sensitive population.

Ti(III) Catalysts for CO2/Epoxide Copolymerization at Unusual Ambient Pressure Conditions

Titanium compounds in low oxidation states are highly reducing species and hence powerful tools for the functionalization of small molecules. However, their potential has not yet been fully realized because harnessing these highly reactive complexes for productive reactivity is generally challenging. Advancing this field, herein we provide a detailed route for the formation of titanium(III) orthophenylendiamido (PDA) species using [LiBHEt3] as a reducing agent. Initially, the corresponding lithium PDA compounds [Li2(ArPDA)(thf)3] (Ar = 2,4,6-trimethylphenyl (MesPDA), 2,6-diisopropylphenyl (iPrPDA)) are combined with [TiCl4(thf)2] to form the heterobimetallic complexes [{TiCl(ArPDA)}(μ-ArPDA){Li(thf)n}] (n = 1, Ar = iPr 3 and n = 2, Ar = Mes 4). Compound 4 evolves to species [Ti(MesPDA)2] (6) via thermal treatment. In contrast, the transformation of 3 into [Ti(iPrPDA)2] (5) only occurs in the presence of [LiNMe2], through a lithium-assisted process, as revealed by density functional theory (DFT). Finally, the Ti(IV) compounds 3-6 react with [LiBHEt3] to give rise to the Ti(III) species [Li(thf)4][Ti(ArPDA)2] (Ar = iPr 8, Mes 9). These low-valent compounds in combination with [PPN]Cl (PPN = bis(triphenylphosphine)iminium) are proved to be highly selective catalysts for the copolymerization of CO2 and cyclohexene epoxide. Reactions occur at 1 bar pressure with activity/selectivity levels similar to Salen-Cr(III) compounds.

Exact decompositions of the total KS-DFT exchange-correlation energy into one- and two-center terms

In the so-called Interacting Quantum Atoms (IQA) approach, the molecular energy is numerically decomposed as a sum of atomic and diatomic contributions. While proper formulations have been put forward for both Hartree-Fock and post-Hartree-Fock wavefunctions, this is not the case for the Kohn-Sham density functional theory (KS-DFT). In this work, we critically analyze the performance of two fully additive approaches for the IQA decomposition of the KS-DFT energy, namely, the one from Francisco et al., which uses atomic scaling factors, and that from Salvador and Mayer based upon the bond order density (SM-IQA). Atomic and diatomic exchange-correlation (xc) energy components are obtained for a molecular test set comprising different bond types and multiplicities and along the reaction coordinate of a Diels-Alder reaction. Both methodologies behave similarly for all systems considered. In general, the SM-IQA diatomic xc components are less negative than the Hartree-Fock ones, which is in good agreement with the known effect of electron correlation upon (most) covalent bonds. In addition, a new general scheme to minimize the numerical error of the sum of two-electron energy contributions (i.e., Coulomb and exact exchange) in the framework of overlapping atoms is described in detail.

Merging the Energy Decomposition Analysis with the Interacting Quantum Atoms Approach

Energy decomposition analysis (EDA) is a well-established approach to dissect the interaction energy into chemically sound components. Despite the inherent requirement of reference states has been a long-standing object of debate, the direct relation with the molecular orbital analysis helps in building up predictive models. The alternative molecular energy decomposition schemes that decompose the total energy into atomic and diatomic contributions, such as the interacting quantum atoms (IQA), has no external reference requirements and also the intra- and intermolecular interactions are treated on equal footing. However, a connection with heuristic chemical models are limited, bringing about a somewhat narrower predictive power. While efforts to reconcile the bonding picture obtained by both methodologies have been discussed in the past, a synergic combination of them has not been tackled yet. Herein, we present the use of IQA decomposition of the individual terms arising from the EDA in the context of intermolecular interactions, henceforth EDA-IQA. The method is applied to a molecular set covering a wide range of interaction types, including hydrogen bonding, charge-dipole, π-π and halogen interactions. We find that the electrostatic energy from EDA, entirely seen as intermolecular, leads to meaningful and non-negligible intra-fragment contributions upon IQA decomposition, originated from charge penetration. EDA-IQA also affords the decomposition of the Pauli repulsion term into intra- and inter-fragment contributions. The intra-fragment term is destabilizing, particularly for the moieties that are net acceptors of charge, while the inter-fragment Pauli term is actually stabilizing. In the case of the orbital interaction term, the sign and magnitude of the intra-fragment contribution at equilibrium geometries is largely driven by the amount of charge transfer, while the inter-fragment contribution is clearly stabilizing. EDA-IQA terms show a smooth behavior along the intermolecular dissociation path of selected systems. The new EDA-IQA methodology provides a richer energy decomposition scheme that aims at bridging the gap between the two main distinct real-space and Hilbert-space methodologies. Via this approach, the partitioning can be used directionally on all the EDA terms aiding in identifying the causal effects on geometries and/or reactivity.

Does Serial Femtosecond Crystallography Depict State-Specific Catalytic Intermediates of the Oxygen-Evolving Complex?

Recent advances in serial femtosecond crystallography (SFX) of photosystem II (PSII), enabled by X-ray free electron lasers (XFEL), provided the first geometric models of distinct intermediates in the catalytic S-state cycle of the oxygen-evolving complex (OEC). These models are obtained by flash-advancing the OEC from the dark-stable state (S₁) to more oxidized intermediates (S₂ and S₃), eventually cycling back to the most reduced S₀. However, the interpretation of these models is controversial because geometric parameters within the Mn₄CaO₅ cluster of the OEC do not exactly match those expected from coordination chemistry for the spectroscopically verified manganese oxidation states of the distinct S-state intermediates. Here we focus on the first catalytic transition, S₁ → S₂, which represents a one-electron oxidation of the OEC. Combining geometric and electronic structure criteria, including a novel effective oxidation state approach, we analyze existing 1-flash (1F) SFX-XFEL crystallographic models that should depict the S₂ state of the OEC. We show that the 1F/S₂ equivalence is not obvious, because the Mn oxidation states and total unpaired electron counts encoded in these models are not fully consistent with those of a pure S₂ state and with the nature of the S₁ → S₂ transition. Furthermore, the oxidation state definition in two-flashed (2F) structural models is practically impossible to elucidate. Our results advise caution in the extraction of electronic structure information solely from the literal interpretation of crystallographic models and call for re-evaluation of structural and mechanistic interpretations that presume exact correspondence of such models to specific catalytic intermediates of the OEC.

Force Decomposition Analysis: A Method to Decompose Intermolecular Forces into Physically Relevant Component Contributions

Computational quantum chemistry can be more than just numerical experiments when methods are specifically adapted to investigate chemical concepts. One important example is the development of energy decomposition analysis (EDA) to reveal the physical driving forces behind intermolecular interactions. In EDA, typically the interaction energy from a good-quality density functional theory (DFT) calculation is decomposed into multiple additive components that unveil permanent and induced electrostatics, Pauli repulsion, dispersion, and charge-transfer contributions to noncovalent interactions. Herein, we formulate, implement, and investigate decomposing the forces associated with intermolecular interactions into the same components. The resulting force decomposition analysis (FDA) is potentially useful as a complement to the EDA to understand chemistry, while also providing far more information than an EDA for data analysis purposes such as training physics-based force fields. We apply the FDA based on absolutely localized molecular orbitals (ALMOs) to analyze interactions of water with sodium and chloride ions as well as in the water dimer. We also analyze the forces responsible for geometric changes in carbon dioxide upon adsorption onto (and activation by) gold and silver anions. We also investigate how the force components of an EDA-based force field for water clusters, namely MB-UCB, compare to those from force decomposition analysis.

Cage-size effects on the encapsulation of P2 by fullerenes

The classic pnictogen dichotomy stands for the great contrast between triply bonding very stable N₂ molecules and its heavier congeners, which appear as dimers or oligomers. A banner example involves phosphorus as it occurs in nature as P₄ instead of P₂ , given its weak π-bonds or strong σ-bonds. The P₂ synthetic value has brought Lewis bases and metal coordination stabilization strategies. Herein, we discuss the unrealized encapsulation alternative using the well-known fullerenes' capability to form endohedral and stabilize otherwise unstable molecules. We chose the most stable fullerene structures from C_n (n = 50, 60, 70, 80) and experimentally relevant from C_n (n = 90 and 100) to computationally study the thermodynamics and the geometrical consequences of encapsulating P₂ inside the fullerene cages. Given the size differences between P₂ and P₄ , we show that the fullerenes C₇₀ -C₁₀₀ are suitable cages to side exclude P₄ and host only one molecule of P₂ with an intact triple bond. The thermodynamic analysis indicates that the process is favorable, overcoming the dimerization energy. Additionally, we have evaluated the host-guest interaction to explain the origins of their stability using energy decomposition analysis.

Reply to the 'Comment on "The oxidation state in low-valent beryllium and magnesium compounds"' by S. Pan and G. Frenking, Chem. Sci., 2022, , DOI: 10.1039/D2SC04231B

A recent article by Pan and Frenking challenges our assignment of the oxidation state of low valent group 2 compounds. With this reply, we show that our assignment of Be(+2) and Mg(+2) oxidation states in Be(cAAC^Dip)₂ and Mg(cAAC^Dip)₂ is fully consistent with our data. Some of the arguments exposed by Pan and Frenking were based on visual inspection of our figures, rather than a thorough numerical analysis. We discuss with numerical proof that some of the statements made by the authors concerning our reported data are erroneous. In addition, we provide further evidence that the criterion of the lowest orbital interaction energy in the energy decomposition analysis (EDA) method is unsuitable as a general tool to assess the valence state of the fragments. Other indicators based on natural orbitals for chemical valence (NOCV) deliver a more reliable bonding picture. We also emphasize the importance of using stable wavefunctions for any kind of analysis, including EDA.

Csp2-H Amination Reactions Mediated by Metastable Pseudo-Oh Masked Aryl-CoIII-nitrene Species

Cobalt-catalyzed C–H amination via M-nitrenoid species is spiking the interest of the research community. Understanding this process at a molecular level is a challenging task, and here we report a well-defined macrocyclic system featuring a pseudo-O_h aryl-Co^III species that reacts with aliphatic azides to effect intramolecular C_sp2–N bond formation. Strikingly, a putative aryl-Co=NR nitrenoid intermediate species is formed and is rapidly trapped by a carboxylate ligand to form a carboxylate masked-nitrene, which functions as a shortcut to stabilize and guide the reaction to productive intramolecular C_sp2–N bond formation. On one hand, several intermediate species featuring the C_sp2–N bond formed have been isolated and structurally characterized, and the essential role of the carboxylate ligand has been proven. Complementarily, a thorough density functional theory study of the C_sp2–N bond formation mechanism explains at the molecular level the key role of the carboxylate-masked nitrene species, which is essential to tame the metastability of the putative aryl-Co^III=NR nitrene species to effectively yield the C_sp2–N products. The solid molecular mechanistic scheme determined for the C_sp2–N bond forming reaction is fully supported by both experimental and computation complementary studies.

A well-defined pseudo-O_h aryl-Co^III species reacts with aliphatic azides to effect intramolecular C_sp2−N bond formation via a carboxylate masked-Co^III-nitrene, which serves as a shortcut to guide the reaction to productive C_sp2−N bond formation.

The oxidation state in low-valent beryllium and magnesium compounds

Low-valent group 2 (E = Be and Mg) stabilized compounds have been long synthetically pursued. Here we discuss the electronic structure of a series of Lewis base-stabilized Be and Mg compounds. Despite the accepted zero(0) oxidation state nature of the group 2 elements of some recent experimentally accomplished species, the analysis of multireference wavefunctions provides compelling evidence for a strong diradical character with an oxidation state of +2. Thus, we elaborate on the distinction between a description as a donor-acceptor interaction L(0) ⇆ E(0) ⇄ L(0) and the internally oxidized situation, better interpreted as a diradical L(-1) → E(+2) ← L(-1) species. The experimentally accomplished examples rely on the strengthened bonds by increasing the π-acidity of the ligand; avoiding this interaction could lead to an unprecedented low-oxidation state.

Oxidation State Localized Orbitals: A Method for Assigning Oxidation States Using Optimally Fragment-Localized Orbitals and a Fragment Orbital Localization Index

Oxidation states represent the ionic distribution of charge in a molecule and are significant in tracking redox reactions and understanding chemical bonding. While effective algorithms already exist based on formal Lewis structures as well as using localized orbitals, they exhibit differences in challenging cases where effects such as redox noninnocence are at play. Given a density functional theory (DFT) calculation with chosen total charge and spin multiplicity, this work reports a new approach to obtaining fragment-localized orbitals that is termed oxidation state localized orbitals (OSLO), together with an algorithm for assigning the oxidation state using the OSLOs and an associated fragment orbital localization index (FOLI). Evaluating the FOLI requires fragment populations, and for this purpose a new version of the intrinsic atomic orbital (IAO) scheme is introduced in which the IAOs are evaluated using a reference minimal basis formed from on-the-fly superposition of atomic density (IAO-AutoSAD) calculations in the target basis set and at the target level of theory. The OSLO algorithm is applied to a range of challenging cases including high valent metal oxide complexes, redox noninnocent NO and dithiolate transition metal complexes, a range of carbene-containing TM complexes, and other examples including the potentially inverted ligand field in [Cu(CF₃)₄]^-. Across this range of cases, OSLO produces generally satisfactory results. Furthermore, in borderline cases, the OSLOs and associated FOLI values provide direct evidence of the emergence of covalent interactions between fragments that nicely complements existing approaches.

Accurate 57Fe Mössbauer Parameters from General Gaussian Basis Sets

The prediction of isomer shifts in ⁵⁷Fe Mossbauer spectra is typically achieved by building calibration lines using the values of the density at the nuclear position. Using Slater-type orbital basis or large and specific Gaussian-type orbital basis has been thus far mandatory to achieve accurate predictions with density functional theory methods. In this work, we show that replacing the value of the density at the nucleus by the density integrated in a sphere of radius 0.06 au centered on the Fe nuclei yields excellent calibration lines (r² = 0.976) with a high predictive power (q² = 0.975, MAE = 0.055 mm·s^–1) while using the conventional def2-TZVP basis set and X-ray geometrical parameters. Our data set comprises 69 ⁵⁷Fe-containing compounds and 103 signals. We also find B3LYP performing significantly better than the PW91 functional.

Diagnosis of Lofgren’s Syndrome and the Role of Ultrasound

We report the case of a 32-year-old woman presenting to the emergency department with ankle edema and arthralgia. Only later in the follow-up period, she developed erythema nodosum. The study revealed bilateral hilar and mediastinal lymphadenopathy and biopsy demonstrated non-caseating granulomas consistent with a diagnosis of Lofgren’s syndrome. Patients often do not present with all signs and symptoms, which delays the correct diagnosis. This case reinforces the need to use diagnostic methods, particularly non-invasive ones, such as ultrasound (US), in such cases. US of the lower extremity swelling could have helped the diagnosis, even without demonstrating effusion.

Unveiling the Electronic Structure of the Bi(+1)/Bi(+3) Redox Couple on NCN and NNN Pincer Complexes

Low-valent group 15 compounds stabilized by pincer ligands have gained particular interest, given their direct access to fine-tune their reactivity by the coordination pattern. Recently, bismuth has been employed in a variety of catalytic transformations by taking advantage of the (+1/+3) redox couple. In this work, we present a detailed quantum–chemical study on the electronic structure of bismuth pincer complexes from two different families, namely, bis(ketimine)phenyl (NCN) and triamide bismuthinidene (NNN). The use of the so-called effective oxidation state analysis allows the unambiguous assignation of the bismuth oxidation state. In contrast to previous studies, our calculations suggest a Bi(+1) assignation for NCN pincer ligands, while Bi(+3) character is found for NNN pincer complexes. Notably, regardless of its oxidation state, the central bismuth atom disposes of up to two lone pairs for coordinating Lewis acids, as indicated by very high first and second proton affinity values. Besides, the Bi–NNN systems can also accommodate two Lewis base ligands, indicating also ambiphilic behavior. The effective fragment orbital analysis of Bi and the ligand allows monitoring of the intricate electron flow of these processes, revealing the noninnocent nature of the NNN ligand, in contrast with the NCN one. By the dissection of the electron density into effective fragment orbitals, we are able to quantify and rationalize the Lewis base/acid character.

Effective oxidation state analysis sheds light on the electronic structure of chemical systems. The oxidation state of bismuthinidene pincer complexes can be assigned as Bi(+1) or Bi(+3) depending on the nature of the ligands. Despite this assignation, the reactivity pattern as Lewis base or acid is similar. The occupation of the effective fragment orbitals gives a straightforward method to quantify the reactivity.

Learning from the COVID-19 lockdown in berlin: Observations and modelling to support understanding policies to reduce NO2

Urban air pollution is a substantial threat to human health. Traffic emissions remain a large contributor to air pollution in urban areas. The mobility restrictions put in place in response to the COVID-19 pandemic provided a large-scale real-world experiment that allows for the evaluation of changes in traffic emissions and the corresponding changes in air quality. Here we use observational data, as well as modelling, to analyse changes in nitrogen dioxide, ozone, and particulate matter resulting from the COVID-19 restrictions at the height of the lockdown period in Spring of 2020. Accounting for the influence of meteorology on air quality, we found that reduction of ca. 30-50 % in traffic counts, dominated by changes in passenger cars, corresponded to reductions in median observed nitrogen dioxide concentrations of ca. 40 % (traffic and urban background locations) and a ca. 22 % increase in ozone (urban background locations) during weekdays. Lesser reductions in nitrogen dioxide concentrations were observed at urban background stations at weekends, and no change in ozone was observed. The modelled reductions in median nitrogen dioxide at urban background locations were smaller than the observed reductions and the change was not significant. The model results showed no significant change in ozone on weekdays or weekends. The lack of a simulated weekday/weekend effect is consistent with previous work suggesting that NOx emissions from traffic could be significantly underestimated in European cities by models. These results indicate the potential for improvements in air quality due to policies for reducing traffic, along with the scale of reductions that would be needed to result in meaningful changes in air quality if a transition to sustainable mobility is to be seriously considered. They also confirm once more the highly relevant role of traffic for air quality in urban areas.

Bent and Linear {CoNO}8 Entities: Structure and Bonding in a Prototypic Class of Nitrosyls

Among the isoelectronic ligands CN^-, CO, and NO⁺, an oblique bonding to the metal is well-established for the nitrosyl ligand, with M-N-O angles down to ≈120°. In the last decades, the nitrosyl community got into the habit of addressing a bent-bonded nitrosyl ligand as ¹NO^-. Thus, because various redox forms of a nitrosyl ligand seem to exist, the ligand is considered to be "noninnocent" because of the obvious ambiguity of an oxidation state (OS) assignment of the ligand and metal. Among the bent-bonded species, the low-spin {CoNO}⁸ class is prototypic. From this class, some 20 new nitrosyl compounds, the X-ray structure determinations of which comply with strict quality criteria, were analyzed with respect to the OS issue. As a result, the effective OS method shows a low-spin d⁸ Co^I-NO⁺ couple instead of a negative OS of the ligand at the BP86/def2-TZVP (+D3, +CPCM with infinite permittivity) level of theory. The same holds for some new members of the linear subclass of {CoNO}⁸ compounds. For all compounds, a largely invariable "real" charge of ≈ -0.3 e was obtained from population analyses. All of these electron-rich d⁸ species strive to manage Pauli repulsion between the metal electrons and the lone pair at the nitrosyl's nitrogen atom, with the bending of the CoNO unit as the most frequent escape.

Secukinumab on Refractory Lupus Nephritis

Lupus nephritis (LN) is the most frequent severe organ manifestation of systemic lupus erythematosus (SLE). About 30% of patients are refractory to treatment. The authors report a case of treatment of LN with interleukin-17-targeted therapy, demonstrating its possible benefit, after reports of T helper 17 cell involvement in SLE pathogenesis.

We present the case of a childbearing age woman with SLE, who developed refractory LN despite all the indicated therapeutic options. During follow up, infection with human papillomavirus was detected, a possible trigger, and the following management was based on this discovery. We currently know that cytokines play a major role in tissue damage and interleukin-17 (IL-17) seems to be a fundamental key in SLE and LN, having shown its expression in renal glomeruli and urinary sediment. Thus, it was decided to start treatment with an anti-IL-17A antibody, secukinumab. After starting secukinumab, clinical and biological features improved and complete renal response was achieved.

The Impact of SARS-CoV-2 Viral Load on the Mortality of Hospitalized Patients: A Retrospective Analysis

Introduction

Coronavirus disease 2019 (COVID-19) has emerged worldwide since December 2019. The standard method for diagnosis is via nucleic acid amplification testing, usually with a reverse-transcription polymerase chain reaction (RT-PCR). Hospitalized infected individuals may require ventilation and may have higher mortality rates. We aim to evaluate the clinical impact of nasopharyngeal viral load on these outcomes.

Materials and methods

We conducted a retrospective cohort study of patients hospitalized with COVID-19 from 17 March 2020 to 1 June 2020 at a tertiary care hospital. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral load was assessed using cycle threshold (Ct) values from an RT-PCR assay applied to nasopharyngeal swab samples. We compared the clinical characteristics of survivors vs. non-survivors and assessed whether the viral load was independently associated with in-hospital 30-day mortality.

Results

We evaluated 197 patients. Thirty-day mortality was verified in 71 (36%) subjects. In the adjusted effects model, only the E-gene Ct value [odd ratio (OR) .873; confidence interval (CI) 95% .769-.992; p .037], age, the number of days of symptoms before admission, lactate dehydrogenase (LDH), and the oxygen saturation (SatO₂)-to-fraction of inspired oxygen (FiO₂) ratio remained significantly associated with 30-day mortality. There was no identified association between the viral loads and disease severity, the need for ventilation, or length of stay.

Discussion

Our results are, in part, concordant with previous papers. One possible limitation to our study is the fact that possibly included disproportionately more patients with poorer outcomes since hospitalization was required. Therefore, further research is required.

Conclusion

SARS-CoV-2 viral load on admission may be an independent predictor of 30-day mortality among hospitalized patients with COVID-19. Providing this information to clinicians could potentially be used to guide risk stratification. 

Primary stapedotomy: Influence of prosthesis diameter on hearing outcome

OBJECTIVES

To evaluate the success rate of primary stapedotomy and to investigate the influence of prosthesis diameter on hearing outcome.

MATERIAL AND METHODS

Retrospective medical chart review of 125 cases who underwent primary small fenestra stapedotomy, from January 2001 to December 2018. The study population was divided in two groups based on Teflon prosthesis diameter - .6mm (60%, N=75) and .4mm (40%, N=50). Pre- and postoperative (≥12 months) air-conduction (AC), bone conduction (BC) and air-bone gap (ABG) thresholds were compared.

RESULTS

Postoperative ABG≤10dB and ≤20dB was achieved by 65.7% and 90% of the patients. A functional hearing (PTA-AC≤30dB) was achieved by 59.2% of patients. Sensorineural hearing loss (SNHL, worsening in BC-PTA>10dB) was identified in 7.2% of patients. Comparison of the .6mm- and .4mm-groups, revealed no differences regarding improvements in AC-PTA (22.4 vs. 20.7dB, p=.56), BC-PTA (3.4 vs. 2.3dB, p=.54) and ABG-PTA (19.1 vs. 18.4dB, p=.77). Hearing outcome evaluation identified similar postoperative success rate (.6mm, 79.7% vs. .4mm, 62%, p=.336) and comparable functional hearing (.6mm, 64% vs. .4mm, 52%; p=.197). The incidence of postoperative SNHL was similar between the two pistons (.6m, 5.3% vs. .4mm, 10%, p=.481).

CONCLUSION

Primary small fenestra stapedotomy is an effective and safe procedure. A postoperative ABG within 10dB was achieved in 67.2% of patients and there was a reduced incidence of sensorineural hearing loss. Hearing outcome was not influenced by diameter of the selected prosthesis. Postoperative bone conduction hearing thresholds did not differ between the groups, which revealed no significant inner ear trauma caused by the larger piston. Although we did not find evidence to suggest one piston over the other, our results showed a trend toward better results with the larger prosthesis.

Clinical Features and Prognostic Factors of 245 Portuguese Patients Hospitalized With COVID-19

Introduction Since the declaration of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic in March 2020, Portugal was considered a role model with regards to the first COVID-19 wave. However, a third wave started in 2021 started, turning the country into the worst in the world regarding new infections and death rate per capita in the last weeks of January 2021. No significant data regarding the country's first wave of hospitalized patients have been published. Those data may help understand the differences over time regarding patients and the clinical approach to them. Herein, we present data of COVID-19 patients hospitalized at the main tertiary hospital of the second-most affected county at the time and identify risk factors associated with disease progression and outcomes. Materials and methods We performed a prospective observational study of patients admitted with COVID-19 to a central hospital between March 20 and June 1, 2020. The primary endpoint of this study was 30-day mortality or the need for ventilatory support and the secondary outcomes were both outcomes individually. Results 245 patients were included, with a median age of 79 years, 52% males. Hypertension (n = 172) and dyslipidemia (n = 114) were the most frequent comorbidities. Half of the patients (n = 121) were treated with hydroxychloroquine. The primary outcome occurred in 114 patients; mortality at 30 days was 35%. Age (OR 1.05; 1.02-1.07) and active cancer (OR 3.89; 1.43-10.57) were associated with the primary outcome, with dyslipidemia being protective (OR 0.46; 0.25-0.80). Treatment with hydroxychloroquine or lopinavir/ritonavir was not associated with the main outcome. Patients who had been symptomatic for more than 7 days had lower mortality (OR 0.23; 0.09-0.63). Discussion In the present study, age and cancer were associated with higher mortality, as noted in prior articles. The population had a higher median age than reported in previous studies, which may explain the increased mortality. The protective association of dyslipidemia was not previously described. This association was not related to statin intake. Conclusion The reported high mortality of COVID-19 is rarely seen in other infectious diseases. Our elderly population probably reflects more reliably the incidence of COVID-19 in European countries with constricted age pyramids.

Origin-Independent Decomposition of the Static Polarizability

Real-space analysis tools afford additive and transferable contributions of atoms to molecular properties. In the case of the molecular (hyper)polarizabilities, the atomic contributions that have been derived so far include a charge-transfer term that is origin-dependent. In this letter, we present the first genuinely origin-independent energy-based (OIEB) methodology for the decomposition of the static (hyper)polarizabilities that benefits from real-space molecular energy decomposition schemes, focusing on the static polarizability and showing that extension to static hyperpolarizabilities is straightforward. The numerical realization of the OIEB method shows the expected origin independence, atomic additivity, and transferability of atomic and functional group polarizability tensors. Furthermore, the OIEB atomic (fragment) polarizability tensors are symmetric by definition.

Idiopathic sudden sensorineural hearing loss: Effectiveness of salvage treatment with low-dose intratympanic dexamethasone

Objectives

To evaluate hearing outcome of salvage treatment with intratympanic steroids (ITS) in idiopathic sudden sensorineural hearing loss (ISSNHL) refractory to initial systemic steroid (SS) therapy.

Material and methods

A retrospective medical chart review was conducted on 54 consecutive patients with ISSNHL refractory to SS. Salvage treatment with a low dose intratympanic dexamethasone (4 mg/ml) was offered after one week of primary treatment. Patients were divided into two groups: 25 patients accepted ITS (treatment group) and 29 patients did not undergo additional treatment (control group). A pure tone average (PTA) gain of at least 10 dB was considered hearing improvement.

Results

Hearing improvement rate was higher in ITS group compared to control group (40% vs. 13.8%, p = 0.035). A mean PTA improvement of 8.6 ± 9.8 dB was observed in the ITS group and, whereas the control group had an average hearing gain of 0.7 ± 2 dB (p < 0.001). Audiometric analysis revealed a significant hearing gain in ITS group at all tested frequencies compared to control group (p < 0.05). Analysis of the selected variables, identified intratympanic steroid treatment as the only independent prognostic factor for hearing improvement (OR = 4.2, 95% CI: 1.1-15.7; p = 0.04).

Conclusion

Intratympanic low dose dexamethasone is effective in patients with incomplete hearing recovery after primary systemic steroid treatment.

Adult-onset Woakes' syndrome: a rare entity

Woakes' syndrome (WS) is a rare entity, defined as severe recalcitrant nasal polyposis with consecutive deformity of the nasal pyramid. WS occurs mainly in childhood and its aetiology remains unclear. We report a case of a 68-year old woman, with aspirin-exacerbated respiratory disease, who presented with recurrent nasal polyposis and progressive broadening of the nasal dorsum. CT scan revealed extensive bilateral nasal polyposis and diffuse osteitis, with anterior ethmoidal calcified lesions. The patient underwent revision endoscopic sinus surgery and nasal pyramid deformity was successfully managed without osteotomies.

Determinants of the Need for Tracheostomy in Neurocritical Patients

Background: Given the difficulties in predicting the need for prolonged intubation and the timing of tracheostomy, the stroke-related early tracheostomy score (SETscore) was developed, and this tool has demonstrated moderate accuracy in predicting intensive care unit (ICU) length of stay (LoS), ventilation duration, and need for tracheostomy. We aim to assess the usefulness of SETscore in a more heterogeneous population that includes trauma patients to whom this score has not yet been applied.

Material and Methods: A retrospective consecutive analysis of all neurocritical patients who were admitted to our medical-surgical ICU between 2016 and 2018 and who required endotracheal intubation within 48 h of admission was performed in this study. Clinicodemographic data, as well as tracheostomy timing, imaging results, and SETscore were evaluated.

Results: The medical records of 732 neurocritical patients were reviewed, but only 493 patients were included, 68 of whom were tracheostomized (TR). These TR patients presented longer LoS and ventilation and antibiotic duration, lower Glasgow Coma Scale (GCS) score at admission, and more respiratory comorbidities. Severity scores, including SETscore, were higher in the TR group. A SETscore of >10 demonstrated 92.6% sensitivity and 79.1% specificity in predicting the need for tracheostomy. The majority of patients were tracheostomized after the seventh day of ICU admission. No significant differences in SETscore as well as in severity scores, age, and gender were observed between the early and late TR groups. However, the need for tracheostomy was significantly associated with lower ICU death rate even after controlling for GCS at admission, gender, age, and duration of invasive mechanical ventilation.

Conclusion: SETscore can be applied to a heterogeneous population. However, more data and prospective analyses are needed to validate their clinical usefulness on a daily basis. Nevertheless, the present data are expected to contribute to the management of neurocritical patients, particularly in the setting of ICUs managing a broad spectrum of critically ill patients.

Beyond the Classical Electron-Sharing and Dative Bond Picture: Case of the Spin-Polarized Bond

Chemical bonds are traditionally assigned as electron-sharing or donor-acceptor/dative. External criteria such as the nature of the dissociation process, energy partitioning schemes, or quantum chemical topology are invoked to assess the bonding situation. However, for systems with marked multi-reference character, this binary categorization might not be precise enough to render the bonding properties. A third scenario can be foreseen: spin polarized bonds. To illustrate this, the case of a NaBH₃ ^- cluster is presented. According to the analysis NaBH₃ ^- exhibits a strong diradical character and cannot be classified as either electron-sharing or a dative bond. Elaborated upon are the common problems of popular bonding descriptions. Additionally, a simple model, based on the bond order and local spin indicators, which discriminates between all three bonding situations, is provided.

Impact of mixing layer height variations on air pollutant concentrations and health in a European urban area: Madrid (Spain), a case study

The occurrence of local high-pollution episodes in densely populated urban areas, which have huge fleets of vehicles, is currently one of the most worrying problems associated with air pollution worldwide. Such episodes are produced under specific meteorological conditions, which favour the sudden increase of levels of air pollutants. This study has investigated the influence of the mixing layer height (MLH) on the concentration levels of atmospheric pollutants and daily mortality in Madrid, Spain, during the period 2011-2014. It may help to understand the causes and impact of local high-pollution episodes. MLH at midday over Madrid was daily estimated from meteorological radio soundings. Then, days with different MLH over this urban area were characterized by meteorological parameters registered at different levels of an instrumented tower and by composite sea level pressure maps, representing the associated synoptic meteorological scenarios. Next, statistically significant associations between MLH and levels of PM₁₀, PM_2.5, NO, NO₂, CO and ultra-fine particles number concentrations registered at representative monitoring stations were evaluated. Finally, associations between all-natural cause daily mortality in Madrid, MLH, and air pollutants were estimated using conditional Poisson regression models. The reduction of MLH to values below 482 m above-ground level under strong atmospheric stagnation conditions was accompanied by a statistically significant increase in levels of NO, NO₂, CO, PM_2.5 and ultra-fine particle number concentrations at urban-traffic and suburban monitoring sites. The decrease of the MLH was also associated to a linear increase of the daily number of exceedances of the UE NO₂ hourly limit value (200 μg/m³) and levels of air pollutants at hotspot urban-traffic monitoring stations. Also, a statistically significant association of the MLH with all-natural cause daily mortality was obtained. When the MLH increased by 830 m, the risk of mortality decreased by 2.5% the same day and by 3.3% the next day, when African dust episodic days were excluded. They were also higher in absolute terms than the increases in risk of mortality that were determined for the exposition to any other air pollutant. Our results suggest that when the prediction models foresee values of MLH below 482 m above-ground level in Madrid, the evolution of high-contamination episodes will be very favourable. Therefore, short-term policy measures will have to be implemented to reduce NO, NO₂, CO, PM_2.5 and ultra-fine particle emissions from anthropogenic sources in this southern European urban location.

Laryngeal oncocytic cystadenoma mimicking a combined laryngomucocele

Laryngeal oncocytic cystadenomas are rare benign tumours lined by oncocytic epithelium and arising from the salivary glands; they usually present as a supraglottic mass. Oncocytic changes are very uncommon in the larynx and occur mainly in ventricles and false vocal cords, where seromucinous glands predominate. The authors present the case of a 62-year-old woman who reported a 6-month history of hoarseness associated with a soft and non-compressible upper left side neck swelling. Transnasal fiberoptic laryngoscopy revealed a left submucosal supraglottic mass involving the false vocal fold and the vallecula, partially obstructing the airway. CT scan showed a homogeneous isodense cystic lesion centred at the left laryngeal ventricle, with extension through the thyrohyoid membrane. The patient was successfully managed by a lateral thyrotomy approach. Histopathological examination of the specimen revealed a papillary oncocytic cystadenoma and excluded malignancy. There was no evidence of recurrence after 9 months of follow-up.

The vitamin D receptor Taq I polymorphism is associated with reduced VDR and increased PDIA3 protein levels in human intestinal fibroblasts

The synonymous single nucleotide polymorphism (SNP) rs731236, located in the vitamin D receptor (VDR) gene (Taq I) has been associated with both decreased levels of the protein in peripheral blood mononuclear cells and a fibrosis-related complication in Crohn´s disease (CD). Interactions between VDR and a protein-disulfide isomerase-associated 3 (PDIA3) in the regulation of extracellular matrix have been reported and we aim to analyze the relevance of the VDR genotypes and the effects of Vitamin D (VD) in the expression of VDR, PDIA3 and proliferation of intestinal fibroblasts. Human intestinal fibroblasts were isolated from the non-affected surgical resections of colorectal patients and classified according to the VDR genotype. In some cases, cells were transfected with specific PDIA3 siRNA. Basal and VD-stimulated expression of VDR, PDIA3 and Collagen 1A1 (COL1A1) as well as fibroblast migration/proliferation were analyzed. Our data show that intestinal fibroblasts homozygous for the C allele in the VDR gene exhibited lower VDR protein levels and higher proliferation than cells homozygous for the T allele. VD increased VDR and attenuated the accelerated proliferation of CC fibroblasts. The diminished VDR level detected in CC cells was associated with increased levels of both PDIA3 and COL1A1 expression and the transient silencing of PDIA3 significantly reduced COL1A1 expression. We conclude that intestinal fibroblasts homozygous for the C allele in the VDR gene exhibited: reduced VDR protein levels, increased proliferation and increased PDIA3/COL1A1 expression. Treatment with VD increased VDR and attenuated proliferation of these cells.

Type I Tympanoplasty: surgical success and prognostic factors

OBJECTIVES

To evaluate success rate of type I tympanoplasty in adults and to investigate the importance of selected prognostic factors on graft uptake.

MATERIAL AND METHODS

Retrospective medical chart review of 155 patients who underwent Type I Tympanoplasty, in our department, from January 2013 to December 2017. Graft uptake rate was evaluated and the effects of prognostic factors on surgical outcome such as sex, smoking and otological surgery history, status of the contralateral ear, size and location of the perforation, middle ear mucosa status, surgical approach and graft material. Preoperative and postoperative audiometric data were collected, and the functional success was determined.

RESULTS

The overall surgical anatomical success rate was 75%. Analysis of the selected variables, identified as independent prognostic factors of anatomical unsuccess (95% CI): smoking (OR=3.29, p<.01), middle ear tympanosclerosis (OR=2.96; p=.04). Perforations above 50% of the tympanic membrane area had a borderline effect on graft uptake (p=.05). There was a significative improvement in the average air conduction thresholds of 7.44dB and an ABG closure rate at 10dB and 20dB was achieved in 47% and 84.5%, respectively. Patients who received temporalis fascia graft had similar hearing gain compared to patients who underwent cartilage tympanoplasty (7.7 vs. 7.3dB, p=.79).

CONCLUSION

Type I tympanoplasty is an effective and safe procedure with a high anatomical success rate in the treatment of mucosal COM. Poorer outcomes were found in patients with smoking habits, in those with tympanosclerosis of middle ear mucosa and in larger perforations. These prognostic factors should be considered in surgical planning and patients should be advised to quit smoking. Tympanoplasty with cartilage graft had a hearing outcome comparable to temporalis fascia graft and should be considered in high-risk patients.

Not Guilty on Every Count: The "Non-Innocent" Nitrosyl Ligand in the Framework of IUPAC's Oxidation-State Formalism

Nitrosyl-metal bonding relies on the two interactions between the pair of N-O-π* and two of the metal's d orbitals. These (back)bonds are largely covalent, which makes their allocation in the course of an oxidation-state determination ambiguous. However, apart from M-N-O-angle or net-charge considerations, IUPAC's "ionic approximation" is a useful tool to reliably classify nitrosyl metal complexes in an orbital-centered approach.

Characterization of organic aerosol at a rural site influenced by olive waste biomass burning

Biomass burning is a major air pollution problem all around the world. However, the identification and quantification of its contribution to ambient aerosol levels is a difficult task due to the generalized lack of observations of molecular markers. This paper presents the results of a yearlong study of organic constituents of the atmospheric aerosol at a rural site in southern Spain (Villanueva del Arzobispo, Jaén). Sampling was performed for PM₁₀ and PM_2.5, and a total of 116 and 115 samples, respectively, were collected and analyzed by GC/MS, quantifying 77 organic compounds. Higher levels of organic pollutants were recorded from November to March, coinciding with the cold season when domestic combustion is a common practice in rural areas. This jointly with adverse meteorological conditions, e.g. strong atmospheric stability, produced severe pollution episodes with high PM_x ambient levels. High daily concentrations of tracers were reached, up to 26 ng m^-3 for B(a)P and 6065 ng m^-3 for levoglucosan in PM_2.5, supporting that biomass burning is a major source of pollution at rural areas. A multivariate statistical study based on factor and cluster analysis, was applied to the data set with the aim to distinguish sources of organic compounds. The main resulting sources were related with biomass combustion, secondary organic aerosol (SOA), biogenic emissions, lubricating oil and soil organic components. A preliminary organic source profile for olive wastes burning was evaluated, based on cluster results, showing anhydrosacharides and xylitol are the main emitted compounds, accounting for more than 85% of the quantified compounds. Other source compounds were fatty acids, diacids, aliphatics, sugars, sugar alcohols, PAHs and quinones.

P0765RHEUMATOID ARTHRITIS AND CHRONIC KIDNEY DISEASE: DOES INFLAMMATION SAY IT ALL?

Background and Aims

Rheumatoid arthritis (RA) increase risk of developing chronic kidney disease (CKD), but it is unknow which risk factors contributes to CKD in this population. This study aims to determine predictors for the development of CKD in RA patients.

Method

A retrospective study was conducted in 106 patients with RA followed at a sub-specialized internal medicine appointment between January 2007 and December 2017. RA was defined according to the American College of Rheumatology criteria and CKD was defined as an estimated glomerular filtration rate less than 60mL/min/ 1.73m2 or presence of abnormalities of urinary sediment for 3 months.

Results

The mean age was 61 ± 12.83 years, and 67.9% (n=72) were female. The prevalence of CKD was 20.8% (n=22). Renal disease had multifactorial etiology in 20 patients, and one case of ANCA negative glomerulonephritis and other of diabetic nephropathy. Individuals with RA and CKD were older, presented more cardiovascular disease, diabetes and hypertension. There was no statistically significant association between gender and the presence of CKD (p = 0.131). Age (p = 0.031) and diabetes (p = 0.031) were independent risk factors for development of CKD in RA patients. RA duration in patients with CKD (8, 4-13) was not statistically different from RA duration in non-CKD patients (7.50, 4,75 – 12,25), (p=0.890).

Conclusion

Patients with RA and CKD had higher incidence of cardiovascular events, diabetes and hypertension which are a major cause of mortality and morbidity in this group. The presence of diabetes mellitus that often arise as an adverse effect of drugs used in the treatment of RA, significantly increased the risk of developing CKD. Otherwise, RA duration didn’t represent a risk factor for developing CKD. Thus, it is important to control diabetes, particularly glucocorticoid-induced diabetes to prevent development of CKD in AR patients.

Saharan dust intrusions in the Iberian Peninsula: Predominant synoptic conditions

The Iberian Peninsula (IP) is recurrently affected by dust transport from the Sahara Desert and from the semi-arid Sahel regions. African dust is one of the most important sources of particulate matter in the southern Mediterranean. Therefore, it is vital to understand the underlying processes that lead to episodes of air pollution associated to the occurrence of dust intrusions. This work proposes to make an extended characterization of the preferential circulation weather patterns associated to the onset of dust events affecting the IP between 2006 and 2016. Saharan dust intrusions were analysed and an automatic objective classification procedure was used to classify circulation weather patterns associated to dust events. The spatial distribution of intrusion episodes is not homogeneous throughout the IP, occurring less frequently at northern and northwestern locations than at central and southern sites. Moreover, days with Saharan dust intrusions were more frequent in summer months, and more probable to occur under regimes with a southerly component. Finally, two extreme events with high concentration of particulate matter were analysed relatively to their life-cycle and particle trajectories. The distinct extreme episodes can be associated to different synoptic situations. However, and despite different large-scale configurations, a south or south-easterly component over the region is responsible for the establishment of a dust transport from the Saharan region towards Iberia, and thus leading to the intrusion onset. These results were supported by the calculation of back-trajectories which allowed to source apportioning the particles' origin, through a clear trajectory of air parcels originating from northern Africa in both events. The proposed framework can be useful to the prediction of dust and air pollution events based on the forecast of circulation weather patterns, as the results show that these events across the IP are mainly induced by specific patterns.

WNT2b Activates Epithelial-mesenchymal Transition Through FZD4: Relevance in Penetrating Crohn´s Disease

BACKGROUND AND AIMS

Epithelial-mesenchymal transition [EMT] has been related to fibrosis and fistula formation, common complications associated with Crohn´s disease [CD]. The WNT signalling pathway mediates EMT, and specific WNT/FZD interactions have been related to the activation of this process in several diseases. We aim to analyse the relevance of EMT and WNT ligands and receptors in the penetrating behaviour of CD.

METHODS

Intestinal surgical resections were obtained from control and CD patients with a stenotic or penetrating behaviour. Fibrosis was determined by the histological analysis of collagen deposition and EMT by confocal microscopy. The expression of WNT ligands, inhibitors, and FZD receptors was analysed by RT-PCR, WB, IH, and IF studies. The effects of WNT2b and the role of FZD4 in EMT were analysed in HT29 epithelial cells.

RESULTS

Fibrosis and expression of EMT markers were detected in samples from CD patients irrespective of the clinical behaviour. However, an increased colocalisation of E-CADHERIN and VIMENTIN, an increased number of cells expressing WNT2b, and a higher expression of FZD4 and WNT2b/FZD4 interaction, were detected in intestinal tissue from the penetrating compared with the stenotic CD behaviour. WNT2b induced EMT in HT29 cells through FZD4 activation.

CONCLUSIONS

An increased EMT, associated with increased WNT2b/FZD4 interaction, was detected in intestinal tissue from CD patients with a penetrating behaviour. WNT2b, through FZD4 activation, induces EMT in vitro which points to a novel pharmacological target to prevent intestinal penetrating complications of CD.

A new tuned range-separated density functional for the accurate calculation of second hyperpolarizabilities

Among the nine functionals benchmarked, the most accurate γ are obtained by Tα-LC-BLYP, reducing about half the errors of LC-BLYP.

African dust and air quality over Spain: Is it only dust that matters?

The 2001-2016 contribution of African dust outbreaks to ambient regional background PM10 and PM2.5 levels over Spain, as well as changes induced in the PMx composition over NE Spain in 2009-2016, were investigated. A clear decrease in PMx dust contributions from the Canary Islands to N Iberia was found. A parallel increase in the PM2.5/PM10 ratio (30% in the Canary Islands to 57% in NW Iberia) was evidenced, probably due to size segregation and the larger relative contribution of the local PMx with increasing distance from Africa. PM1-10 and PM2.5-10 measured in Barcelona during African dust outbreaks (ADOs) were 43-46% higher compared to non-ADO days. The continental background contribution prevailed in terms of both PM1-10 and PM2.5-10 during ADO days (62 and 69%, respectively, and 31 and 27% for non-ADO days). The relative contributions of Al₂O₃/Fe₂O₃/CaO to PMx fraction showed that Al₂O₃ is a suitable tracer for African dust in our context; while CaO at the urban site is clearly affected by local resuspension, construction and road dust, and Fe₂O₃ by dust from vehicle brake discs. The results also provide evidence that PM increases during ADOs are caused not only by the mineral dust load, but by an increased accumulation of locally emitted or co-transported anthropogenic pollutants as compared with non-ADO days. Possible causes for this accumulation are discussed. We recommend that further epidemiological studies should explore independently the potential effects of mineral dust and the anthropogenic PM during ADOs, because, at least over SW Europe, not only mineral dust affects the air quality during African dust episodes.