Hygroscopic properties of ultrafine aerosol particles in the boreal forest: diurnal variation, solubility and the influence of sulfuric acid

International audienceThe hygroscopic growth of aerosol particles present in a boreal forest was measured at a relative humidity of 88%. Simultaneously the gas phase concentration of sulfuric acid, a very hygroscopic compound, was monitored. The focus was mainly on days with new particle formation by nucleation. The measured hygroscopic growth factors (GF) correlated positively with the gaseous phase sulfuric acid concentrations. The smaller the particles, the stronger the correlation, with r=0.20 for 50 nm and r=0.50 for 10 nm particles. The increase in GF due to condensing sulfuric acid is expected to be larger for particles with initially smaller masses. During new particle formation, the changes in solubility of the new particles were calculated during their growth to Aitken mode sizes. As the modal diameter increased, the solubility of the particles decreased. This indicated that the initial particle growth was due to more hygroscopic compounds, whereas the later growth during the evening and night was mainly caused by less hygroscopic or even hydrophobic compounds. For all the measured sizes, a diurnal variation in GF was observed both during days with and without particle formation. The GF was lowest at around midnight, with a mean value of 1.12?1.24 depending on particle size and if new particle formation occurred during the day, and increased to 1.25?1.34 around noon. This can be tentatively explained by day- and nighttime gas-phase chemistry; different vapors will be present depending on the time of day, and through condensation these compounds will alter the hygroscopic properties of the particles in different ways

Why formation rate of 3 nm particles depends linearly on sulphuric acid concentration?

International audienceAccording to atmospheric observations new particle formation seems to be a function of sulphuric acid concentration to the power from one to two. The nucleation theorem then predicts that the critical cluster contains one to two sulphuric acid molecules. However, existing nucleation theories predicts that the power is more (or equal) than 2. Here we present an activation theory, which can explain the observed slope. In cluster activation the clusters containing one sulphuric acid molecule will activate for further growth due to heterogeneous nucleation, heterogeneous chemical reactions including polymerization or activation of soluble clusters. In the activation process organic vapours are typically needed as condensing agents

Describing voluntarily reported fluid therapy incidents in the care of critically ill patients: Identifying, and learning from, points of risk at the national level

Background:Fluid therapy is a common intervention in critically ill patients. Fluid therapy errors may cause harm to patients. Thus, understanding of reported fluid therapy incidents is required in order to learn from them and develop protective measures, including utilizing expertise of pharmacists and technology to improve patient safety at the national level. Objectives:To describe fluid therapy incidents voluntarily reported in intensive care and high dependency units (ICUs) to a national incident reporting system, by investigating the error types,fluid products, consequences to patients and actions taken to alleviate them, and to identify at which phase of the medication process the incidents had occurred and had been detected. Methods:Medication related voluntarily reported incident (n= 7623) reports were obtained from all ICUs in2007–2017. Incidents concerning fluid therapy (n= 2201) were selected. The retrospective analysis utilized categorized data and narrative descriptions of the incidents. The results were expressed as frequencies and percentages. Results:Most voluntarily reported incidents had occurred during the dispensing/preparing phase(n= 1306, 59%) of the medication process: a point of risk. Most incidents (n= 1975, 90%) had reached the patient and passed through many phases in the medication process and nursing shift change checks before detection. One third of the errors (n=596,30%) were reported to have caused consequences to patients. One quarter (n= 492, 25%) of the errors were reported to have required an additional procedure to alleviate or monitor the consequences. Conclusions:Utilizing national incident report data enabled identifying systemic points of risk in the medication process and learning to improve patient safety. To prevent similar incidents, initial interventions should focus on the dispensing/preparing phase before implementing active medication identification procedures at each phase of the medication process and nursing shift changes. Strengthening clinical pharmacy services, utilizing technology, co-ordinated by IV Fluid Coordinators and Medication Safety Officers, could improve patient safety in the ICUs.Peer reviewe

Reminding staff of diligence during the medication process is not enough to ensure safety : Learning from wrong fluid product selection incidents in the care of critically ill patients

Background and objectives: Wrong fluid product selection may cause harm to patients. This study aimed to describe voluntarily reported wrong fluid product selection incidents, including their consequences, the reported latent conditions and active failures leading to these and the suggested safeguards to prevent their occurrence, and to compare the suggested and literature-based safeguards to improve the fluid therapy safety within the intensive care (ICU) environment. Methods: All voluntarily and anonymously reported wrong fluid product selection incidents in all Finnish ICUs during 2007–2017 were reviewed. The incident reports included categorized data that were analyzed quantitatively, and narratives that were analyzed qualitatively, using content analysis. The results were reported as frequencies and percentages and described by using Reason's model of human error. Results: Over the eleven years, one wrong fluid product selection incident was reported every six days (n=663; 584 errors, 79 near misses); most were reported to have occurred during the dispensing/preparing phase (92%). Of the 584 reported selection errors, a quarter (26%) was reported to have caused consequences to patients, and one third (35%) to have required corrective or monitoring actions. The main reported latent conditions to the incidents were Working environment and resources (e.g. workload and time pressure) (29%), Similar-looking and -sounding names or shared features of the product containers (i.e. the LASA phenomenon) (28%) and Working methods (22%); and the main reported active failures were a lack of concentration, or forgetfulness (26%). Some usable suggestions of safeguards were made, e.g. optimizing fluid storage (15%) or utilizing checking practices (21%). While requiring accuracy, i.e. reminding staff of diligence and to be more attentive to detail during the whole medication process, was emphasized in most reports (71%), involving manufacturers in redesigning labels of fluid products, utilizing technology and strengthening pharmacy services are advocated existing literature. Conclusions: Wrong fluid product selection incidents with various latent conditions and active failures were reported more than once a week. To minimize the serious LASA phenomenon,multi-professional collaboration, coordinated international discussion and agreements of solutions with manufacturers, regulators and end-users, are needed. However, work is also needed to reduce the other latent factors, such as Working environment and resources as well as cognitive biases in daily work that may contribute to the occurrence of LASA related errors.Peer reviewe

Connections between atmospheric sulphuric acid and new particle formation during QUEST III–IV campaigns in Heidelberg and Hyytiälä

This study investigates the connections between atmospheric sulphuric acid and new particle formation during QUEST III and BACCI/QUEST IV campaigns. The campaigns have been conducted in Heidelberg (2004) and Hyytiälä (2005), the first representing a polluted site surrounded by deciduous forest, and the second a rural site in a boreal forest environment. We have studied the role of sulphuric acid in particle formation and growth by determining 1) the power-law dependencies between sulphuric acid ([H₂SO₄]), and particle concentrations (<I>N</I>_3&ndash;6) or formation rates at 1 nm and 3 nm (<I>J</i>₁ and <I>J</I>₃); 2) the time delays between [H₂SO₄] and <I>N</I>_3&ndash;6 or <I>J</I>₃, and the growth rates for 1&ndash;3 nm particles; 3) the empirical nucleation coefficients <I>A</I> and <I>K</I> in relations <I>J</I>₁=<I>A</I>[H₂SO₄] and <I>J</I>₁=<I>K</I>[H₂SO₄]², respectively; 4) theoretical predictions for <I>J</I>₁ and <I>J</I>₃ for the days when no significant particle formation is observed, based on the observed sulphuric acid concentrations and condensation sinks. In both environments, <I>N</I>_3&ndash;6 or <I>J</I>₃ and [H₂SO₄] were linked via a power-law relation with exponents typically ranging from 1 to 2. The result suggests that the cluster activation theory and kinetic nucleation have the potential to explain the observed particle formation. However, some differences between the sites existed: The nucleation coefficients were about an order of magnitude greater in Heidelberg than in Hyytiälä conditions. The time lags between <I>J</I>₃ and [H₂SO₄] were consistently lower than the corresponding delays between <I>N</I>_3&ndash;6 and [H₂SO₄]. The exponents in the <I>J</I>₃&#x221D;[H₂SO₄ ]^n_J3-connection were consistently higher than or equal to the exponents in the relation <I>N</I>_3&ndash;6&#x221D;[H₂SO₄ ]^n_N36. In the <I>J</I>₁ values, no significant differences were found between the observed rates on particle formation event days and the predictions on non-event days. The <I>J</I>₃ values predicted by the cluster activation or kinetic nucleation hypotheses, on the other hand, were considerably lower on non-event days than the rates observed on particle formation event days. This study provides clear evidence implying that the main process limiting the observable particle formation is the competition between the growth of the freshly formed particles and their loss by scavenging, rather than the initial particle production by nucleation of sulphuric acid. In general, it can be concluded that the simple models based on sulphuric acid concentrations and particle formation by cluster activation or kinetic nucleation can predict the occurence of atmospheric particle formation and growth well, if the particle scavenging is accurately accounted for

Modeling the compositional instability in wurtzite Ga1-x InxN

The paper deals with multiscale modeling of the minor component ordering in wurtzite Ga1−xInxN (x<0.5) alloys. The treatment combines the total-energy density-functional calculations of the metal atom interaction parameters and the atomistic description of the alloy decomposition using lattice kinetic Monte Carlo. It is demonstrated that the phase decomposition patterns in wurzite GaInN are very sensitive to the interplay of metal atom interactions at several interatomic distances (at least to the fourth nearest neighbors) on the cation sublattice. Variation of the metal interaction energies within reasonable limits resulted in pronouncedly different relaxation patterns (linear or wall ordering of In and Ga atoms along c-axis, planar ordering parallel to basal plane, spinodal decomposition). The high sensitivity of the GaInN decomposition to relatively small variations of the metal interaction energies could be the main reason for the experimentally observed versatility of the alloy decomposition patterns and their sensitivity to the particular experimental conditions.Peer reviewe

Technical note: Analytical formulae for the critical supersaturations and droplet diameters of CCN containing insoluble material

International audienceIn this paper, we consider the cloud drop activation of aerosol particles consisting of water soluble material and an insoluble core. Based on the Köhler theory, we derive analytical equations for the critical diameters and supersaturations of such particles. We demonstrate the use of the equations by comparing the critical supersaturations of particles composed of ammonium sulfate and insoluble substances with those of model organic particles with varying molecular sizes

On the hygroscopic growth of ammoniated sulfate particles of non-stoichiometric composition

International audienceThe hygroscopic growth of ammoniated sulfate particles was studied by measurements and model calculations for particles with varying ammonium-to-sulfate ratio. In the measurements, the ammonium-to-sulfate ratio was adjusted by using mixtures of ammonium sulfate and ammonium bisulfate in generating the solid particles. The hygroscopic growth was measured using a tandem differential mobility analyzer. The measurements were simulated using a thermodynamical equilibrium model. The calculations indicated that the solid phases in particle with ammonium-to-sulfate ratio between 1.5?2, were ammonium sulfate and letovicite. Both in the calculations and in the experiments the hygroscopic growth was initiated at relative humidities less than the theoretical deliquescence relative humidity of these particles. This indicates that the particles were multi-phase particles including solids and liquids. The equilibrium model yielded a satisfactory prediction of the hygroscopic growth of particles generated from a solution with 1:1 mass ratio between dissolved ammonium sulfate and ammonium bisulfate. However, for particles with 3:1 and 10:1 mass ratios, the model predictions overestimated the growth at relative humidities between about 60% and the point of complete deliquescence (close to 80% RH). In contrast, a model, in which letovicite was allowed to dissolve only after complete dissolution of ammonium sulfate, reproduced the observations well. This indicates that the dry particles had a letovicite core surrounded by an ammonium sulfate shell

The influence of nitric acid on the cloud processing of aerosol particles

International audienceIn this paper we present simulations of the effect of nitric acid (HNO3) on cloud processing of aerosol particles. Sulfuric acid (H2SO4) production and incloud coagulation are both affected by condensed nitric acid as nitric acid increases the number of cloud droplets, which will lead to smaller mean size and higher total surface area of droplets. As a result of increased cloud droplet number concentration (CDNC), the incloud coagulation rate is enhanced by a factor of 1?1.3, so that the number of interstitial particles reduces faster. In addition, sulfuric acid production occurs in smaller particles and so the cloud processed aerosol size distribution is dependent on the HNO3 concentration. This affects both radiative properties of aerosol particles and the formation of cloud droplets during a sequence of cloud formation-evaporation events. It is shown that although the condensation of HNO3 increases the number of cloud droplets during the single updraft, it is possible that presence of HNO3 can actually decrease the cloud droplet number concentration after several cloud cycles when also H2SO4 production is taken into account

Transposition and time-warp invariant algorithm for detecting repeated patterns in polyphonic music

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