Spectral Intensity Bioaerosol Sensor (SIBS): an instrument for spectrally resolved fluorescence detection of single particles in real time

Primary biological aerosol particles (PBAPs) in the atmosphere are highly relevant for the Earth system, climate, and public health. The analysis of PBAPs, however, remains challenging due to their high diversity and large spatiotemporal variability. For real-time PBAP analysis, light-induced fluorescence (LIF) instruments have been developed and widely used in laboratory and ambient studies. The interpretation of fluorescence data from these instruments, however, is often limited by a lack of spectroscopic information. This study introduces an instrument – the Spectral Intensity Bioaerosol Sensor (SIBS; Droplet Measurement Technologies (DMT), Longmont, CO, USA) – that resolves fluorescence spectra for single particles and thus promises to expand the scope of fluorescent PBAP quantification and classification. The SIBS shares key design components with the latest versions of the Wideband Integrated Bioaerosol Sensor (WIBS) and the findings presented here are also relevant for the widely deployed WIBS-4A and WIBS-NEO as well as other LIF instruments. The key features of the SIBS and the findings of this study can be summarized as follows. Particle sizing yields reproducible linear responses for particles in the range of 300&thinsp;nm to 20&thinsp;µm. The lower sizing limit is significantly smaller than for earlier commercial LIF instruments (e.g., WIBS-4A and the Ultraviolet Aerodynamic Particle Sizer; UV-APS), expanding the analytical scope into the accumulation-mode size range. Fluorescence spectra are recorded for two excitation wavelengths (λex=285 and 370&thinsp;nm) and a wide range of emission wavelengths (λmean=302–721&thinsp;nm) with a resolution of 16 detection channels, which is higher than for most other commercially available LIF bioaerosol sensors. Fluorescence spectra obtained for 16 reference compounds confirm that the SIBS provides sufficient spectral resolution to distinguish major modes of molecular fluorescence. For example, the SIBS resolves the spectral difference between bacteriochlorophyll and chlorophyll a and b. A spectral correction of the instrument-specific detector response is essential to use the full fluorescence emission range. Asymmetry factor (AF) data were assessed and were found to provide only limited analytical information. In test measurements with ambient air, the SIBS worked reliably and yielded characteristically different spectra for single particles in the coarse mode with an overall fluorescent particle fraction of ∼4&thinsp;% (3σ threshold), which is consistent with earlier studies in comparable environments.</ul

Illustration of microphysical processes in Amazonian deep convective clouds in the gamma phase space: introduction and potential applications

The behavior of tropical clouds remains a major open scientific question, resulting in poor representation by models. One challenge is to realistically reproduce cloud droplet size distributions (DSDs) and their evolution over time and space. Many applications, not limited to models, use the gamma function to represent DSDs. However, even though the statistical characteristics of the gamma parameters have been widely studied, there is almost no study dedicated to understanding the phase space of this function and the associated physics. This phase space can be defined by the three parameters that define the DSD intercept, shape, and curvature. Gamma phase space may provide a common framework for parameterizations and intercomparisons. Here, we introduce the phase space approach and its characteristics, focusing on warm-phase microphysical cloud properties and the transition to the mixed-phase layer. We show that trajectories in this phase space can represent DSD evolution and can be related to growth processes. Condensational and collisional growth may be interpreted as pseudo-forces that induce displacements in opposite directions within the phase space. The actually observed movements in the phase space are a result of the combination of such pseudo-forces. Additionally, aerosol effects can be evaluated given their significant impact on DSDs. The DSDs associated with liquid droplets that favor cloud glaciation can be delimited in the phase space, which can help models to adequately predict the transition to the mixed phase. We also consider possible ways to constrain the DSD in two-moment bulk microphysics schemes, in which the relative dispersion parameter of the DSD can play a significant role. Overall, the gamma phase space approach can be an invaluable tool for studying cloud microphysical evolution and can be readily applied in many scenarios that rely on gamma DSDs

Aircraft-based observations of isoprene-epoxydiol-derived secondary organic aerosol (IEPOX-SOA) in the tropical upper troposphere over the Amazon region

During the ACRIDICON-CHUVA field project (September-October 2014;based in Manaus, Brazil) aircraft-based in situ measurements of aerosol chemical composition were conducted in the tropical troposphere over the Amazon using the High Altitude and Long Range Research Aircraft (HALO), covering altitudes from the boundary layer (BL) height up to 14.4 km. The submicron non-refractory aerosol was characterized by flash-vaporization/electron impact-ionization aerosol particle mass spectrometry. The results show that significant secondary organic aerosol (SOA) formation by isoprene oxidation products occurs in the upper troposphere (UT), leading to increased organic aerosol mass concentrations above 10 km altitude. The median organic mass concentrations in the UT above 10 km range between 1.0 and 2.5 mu g m(-3) (referring to standard temperature and pressure;STP) with interquartile ranges of 0.6 to 3.2 mu g m(-3) (STP), representing 78 % of the total submicron non-refractory aerosol particle mass. The presence of isoprene-epoxydiol-derived secondary organic aerosol (IEPOX-SOA) was confirmed by marker peaks in the mass spectra. We estimate the contribution of IEPOX-SOA to the total organic aerosol in the UT to be about 20 %. After isoprene emission from vegetation, oxidation processes occur at low altitudes and/or during transport to higher altitudes, which may lead to the formation of IEPOX (one oxidation product of isoprene). Reactive uptake or condensation of IEPOX on preexisting particles leads to IEPDX-SOA formation and subsequently increasing organic mass in the UT. This organic mass increase was accompanied by an increase in the nitrate mass concentrations, most likely due to NOx production by lightning. Analysis of the ion ratio of NO+ to NO2+ indicated that nitrate in the UT exists mainly in the form of organic nitrate. IEPOX-SOA and organic nitrates are coincident with each other, indicating that IEPDX-SOA forms in the UT either on acidic nitrate particles forming organic nitrates derived from IEPDX or on already neutralized organic nitrate aerosol particles

Prognostic model to predict postoperative acute kidney injury in patients undergoing major gastrointestinal surgery based on a national prospective observational cohort study.

Background: Acute illness, existing co-morbidities and surgical stress response can all contribute to postoperative acute kidney injury (AKI) in patients undergoing major gastrointestinal surgery. The aim of this study was prospectively to develop a pragmatic prognostic model to stratify patients according to risk of developing AKI after major gastrointestinal surgery. Methods: This prospective multicentre cohort study included consecutive adults undergoing elective or emergency gastrointestinal resection, liver resection or stoma reversal in 2-week blocks over a continuous 3-month period. The primary outcome was the rate of AKI within 7 days of surgery. Bootstrap stability was used to select clinically plausible risk factors into the model. Internal model validation was carried out by bootstrap validation. Results: A total of 4544 patients were included across 173 centres in the UK and Ireland. The overall rate of AKI was 14·2 per cent (646 of 4544) and the 30-day mortality rate was 1·8 per cent (84 of 4544). Stage 1 AKI was significantly associated with 30-day mortality (unadjusted odds ratio 7·61, 95 per cent c.i. 4·49 to 12·90; P < 0·001), with increasing odds of death with each AKI stage. Six variables were selected for inclusion in the prognostic model: age, sex, ASA grade, preoperative estimated glomerular filtration rate, planned open surgery and preoperative use of either an angiotensin-converting enzyme inhibitor or an angiotensin receptor blocker. Internal validation demonstrated good model discrimination (c-statistic 0·65). Discussion: Following major gastrointestinal surgery, AKI occurred in one in seven patients. This preoperative prognostic model identified patients at high risk of postoperative AKI. Validation in an independent data set is required to ensure generalizability

Association between peri-operative angiotensin-converting enzyme inhibitors and angiotensin-2 receptor blockers and acute kidney injury in major elective non-cardiac surgery: a multicentre, prospective cohort study

The peri-operative use of angiotensin-converting enzyme inhibitors or angiotensin-2 receptor blockers is thought to be associated with an increased risk of postoperative acute kidney injury. To reduce this risk, these agents are commonly withheld during the peri-operative period. This study aimed to investigate if withholding angiotensin-converting enzyme inhibitors or angiotensin-2 receptor blockers peri-operatively reduces the risk of acute kidney injury following major non-cardiac surgery. Patients undergoing elective major surgery on the gastrointestinal tract and/or the liver were eligible for inclusion in this prospective study. The primary outcome was the development of acute kidney injury within seven days of operation. Adjusted multi-level models were used to account for centre-level effects and propensity score matching was used to reduce the effects of selection bias between treatment groups. A total of 949 patients were included from 160 centres across the UK and Republic of Ireland. From this population, 573 (60.4%) patients had their angiotensin-converting enzyme inhibitors or angiotensin-2 receptor blockers withheld during the peri-operative period. One hundred and seventy-five (18.4%) patients developed acute kidney injury; there was no difference in the incidence of acute kidney injury between patients who had their angiotensin-converting enzyme inhibitors or angiotensin-2 receptor blockers continued or withheld (107 (18.7%) vs. 68 (18.1%), respectively; p = 0.914). Following propensity matching, withholding angiotensin-converting enzyme inhibitors or angiotensin-2 receptor blockers did not demonstrate a protective effect against the development of postoperative acute kidney injury (OR (95%CI) 0.89 (0.58–1.34); p = 0.567)

Vergleich von Fensterlüftungssystemen und anderen Lüftungs- bzw. Luftreinigungsansätzen gegen die Aerosolübertragung von COVID-19 und für erhöhte Luftqualität in Klassenräumen (Version 1.0)

Diese Studie vergleicht die Wirksamkeit verschiedener Lösungsansätze für infektionsschutz­gerechte Lüftung bzw. Luftreinigung zur Eindämmung der COVID-19-Pandemie und zur Erhöhung der Luftqualität in Klassenräumen. Wir zeigen, dass Fensterlüften ergänzt durch einfache technische Hilfsmittel sehr gut und effizient für die Aufrechterhaltung guter Luftqualität und den Infektionsschutz gegen Aerosolübertragung von SARS-CoV-2 eingesetzt werden kann - auch im Vergleich zu konventionellen raumlufttechnischen Anlagen sowie zu filter- oder UV-strahlungsbasierten Luftreinigungsgeräten. Besonders wirksam ist eine Verdrängungslüftung (Quelllüftung) mit bodennaher Frischluftzufuhr durch Fenster und verteilter Abluftabsaugung über potentiell infektiösen Personen. Bei geringen Temperaturdifferenzen und geringen Windgeschwindig­keiten, d.h., speziell im Sommer, ist Fensterlüften unterstützt durch Ventilatoren deutlich effektiver als freies Fensterlüften. In Schulklassen, wo viele Personen auf engem Raum zusammenkommen und Wärme sowie Feuchte abgeben, bringt eine Behandlung der stets nötigen Zuluft zwecks Rückgewinnung von Wärme oder Feuchte nach unseren Ergebnissen weder bezüglich der Primärenergie noch bezüglich der Raumfeuchte wesentliche Vorteile. Eine einfache Zufuhr von Frischluft durch Fenster nach dem Quellluft-Prinzip erscheint deutlich sinnvoller als eine Behandlung der Zuluft mit technischen Komponenten, die hygienische Probleme bereiten können und einen erhöhten Wartungsaufwand verursachen. Insgesamt zeigt der Vergleich, dass Fensterlüften mit einfachen technischen Hilfsmitteln wie Ventilatoren und Abzugshauben nicht nur kostengünstig und leicht realisierbar ist, sondern auch besonders effektiv in der Luftreinhaltung und gegen die Aerosolübertragung von Infektions­krankheiten wie COVID-19 oder Influenza. Um zur Eindämmung der aktuellen Pandemie sowie allgemein zur Verbesserung der Luftqualität in Schulklassen beizutragen, empfehlen wir den Einbau und Betrieb solcher Fensterlüftungssysteme in allen Klassenräumen, die nicht bereits mit ähnlich wirksamen Hilfsmitteln ausgestattet sind. Aus unserer Sicht sollte es mit relativ geringem Aufwand und in kurzer Zeit machbar sein, alle Klassenräume mit einem geeigneten Abluftventilator auszustatten. Um die COVID-19-Pandemie möglichst schnell und wirksam einzudämmen, sollte der Abluftventilator nach Möglichkeit mit einer verteilten Abluftabsaugung kombiniert werden. Nach der Pandemie kann die verteilte Absaugung nach Bedarf weiter genutzt werden – z.B. in schlecht lüftbaren Räumen und bei Grippewellen – oder flexibel abgebaut bzw. modifiziert werden, was aufgrund der geringen Kosten und der modularen Bauweise leicht möglich ist. Unabhängig von der verteilten Absaugung bieten ventilator­gestützte Fensterlüftungssysteme mit geringem Aufwand zuverlässige Abhilfe für seit langem bestehende Innraumluftqualitätsprobleme in Schulen

Vergleich verschiedener Lüftungsmethoden gegen die Aerosolübertragung von COVID-19 und für erhöhte Luftqualität in Klassenräumen: Fensterlüften, Abluftventilatoren, Raumlufttechnik und Luftreiniger (Version 2.0)

Diese Studie vergleicht die Wirksamkeit verschiedener Lösungsansätze für infektionsschutzgerechte Lüftung bzw. Luftreinigung zur Eindämmung der COVID-19-Pandemie und zur Erhöhung der Luftqualität in Klassenräumen. Wir zeigen, dass Fensterlüften ergänzt durch einfache technische Hilfsmittel sehr gut und effizient für die Aufrechterhaltung guter Luftqualität und den Infektionsschutz gegen Aerosolübertragung von SARS-CoV-2 eingesetzt werden kann - auch im Vergleich zu konventionellen raumlufttechnischen Anlagen sowie zu filter- oder UV-strahlungsbasierten Luftreinigern. Besonders wirksam ist eine Verdrängungslüftung (Quelllüftung) mit bodennaher Frischluftzufuhr durch Fenster und verteilter Abluftabsaugung über potentiell infektiösen Personen. Speziell bei warmen Wetterlagen ist Fensterlüften unterstützt durch Ventilatoren deutlich effektiver als freies Fensterlüften. Kohlendioxid-Monitore sollten eingesetzt werden, um die Raumluftqualität zu messen und ein dauerhaftes Überschreiten des CO2-Leitwerts von 1000 ppm zu vermeiden. Im Vergleich zu Luftreinigern sind Lüftungsmethoden mit Frischluftzufuhr effizienter und nachhaltiger; zudem kann ihre Wirkung mittels CO2-Monitor besser kontrolliert werden. Der Einsatz von Luftreinigern erscheint nur dort zweckmäßig, wo ausreichende Frischluftzufuhr nicht möglich ist. Raumlufttechnik (RLT) mit Wärmerückgewinnung (WRG) und Feuchterückgewinnung bringt unter mittleren deutschen Klimabedingungen kaum Vorteile für den Primärenergiebedarf und die Raumfeuchte in Schulklassen. Wärmetauscher und sonstige technische Komponenten für die Rückgewinnung verursachen hohen Stromverbrauch und Wartungsaufwand, und sie können zu hygienischen Problemen führen. Der Einsatz von RLT/WRG erscheint nur dort zweckmäßig, wo Frischluft in ausreichender Qualität und Menge nicht durch Fenster zugeführt und durch vorhandene Heizungsanlagen angemessen temperiert werden kann, beispielsweise bei starker Schadstoff- und Lärmbelastung der Umgebung oder in thermischen Extremlagen (z.B. an sehr verkehrsreichen Straßen oder in Bergregionen). Insgesamt zeigt der Vergleich, dass Fensterlüften mit einfachen technischen Hilfsmitteln wie Ventilatoren, Abzugshauben und CO2-Monitoren nicht nur kostengünstig und leicht realisierbar ist, sondern auch besonders effektiv in der Luftreinhaltung und gegen die Aerosolübertragung von Infektionskrankheiten wie COVID-19 oder Influenza. Daher empfehlen wir den Einbau und Betrieb von Ventilator-Fensterlüftungssystemen in allen Klassenräumen, die nicht bereits mit ähnlich wirksamen Hilfsmitteln ausgestattet sind. Abluftventilatoren und weitere Komponenten können mit geringem Aufwand kurzfristig installiert werden. Nach der Pandemie können die Fensterlüftungssysteme flexibel und modular weiter genutzt werden. Sie bieten zuverlässige Abhilfe für seit langem bestehende Innraumluftqualitätsprobleme in Schulen – energiesparend, ressourcenschonend und klimafreundlich

Investigation of gaseous and particulate emissions from various marine vessel types measured on the banks of the Elbe in Northern Germany

Measurements of the ambient aerosol, various trace gases and meteorological quantities using a mobile laboratory (MoLa) were performed on the banks of the Lower Elbe in an emission control area (ECA) which is passed by numerous private and commercial marine vessels reaching and leaving the port of Hamburg, Germany. From 25–29 April 2011 a total of 178 vessels were probed at a distance of about 0.8–1.2 km with high temporal resolution. 139 ship emission plumes were of sufficient quality to be analyzed further and to determine emission factors (EFs). Concentrations of aerosol number and mass as well as polycyclic aromatic hydrocarbons (PAH) and black carbon were measured in PM1 and size distribution instruments covered the diameter range from 6 nm up to 32 μm. The chemical composition of the non-refractory submicron aerosol was measured by means of an Aerosol Mass Spectrometer (Aerodyne HR-ToF-AMS). Gas phase species analyzers monitored various trace gases (O3, SO2, NO, NO2, CO2) in the air and a weather station provided wind, precipitation, solar radiation data and other quantities. Together with ship information for each vessel obtained from Automatic Identification System (AIS) broadcasts a detailed characterization of the individual ship types and of features affecting gas and particulate emissions is provided. Particle number EFs (average 2.6e+16 # kg&minus;1) and PM1 mass EFs (average 2.4 g kg&minus;1) tend to increase with the fuel sulfur content. Observed PM1 composition of the vessel emissions was dominated by organic matter (72%), sulfate (22%) and black carbon (6%) while PAHs only account for 0.2% of the submicron aerosol mass. Measurements of gaseous components showed an increase of SO2 (average EF: 7.7 g kg&minus;1) and NOx (average EF: 53 g kg&minus;1) while O3 decreased when a ship plume reached the sampling site. The particle number size distributions of the vessels are generally characterized by a bimodal size distribution, with the nucleation mode in the 10–20 nm diameter range and a combustion aerosol mode centered at about 35 nm while particles extgreater 1 μm were not found. "High particle number emitters" are characterized by a dominant nucleation mode. By contrast, increased particle concentrations around 150 nm primarily occurred for "high black carbon emitters". Classifying the vessels according to their gross tonnage shows a decrease of the number, black carbon and PAH EFs while EFs of SO2, NO, NO2, NOx, AMS species (particulate organics, sulfate) and PM1 mass concentration increase with increasing gross tonnages

Quantitative single-particle analysis with the Aerodyne aerosol mass spectrometer: development of a new classification algorithm and its application to field data

Single-particle mass spectrometry has proven a valuable tool for gaining information on the mixing state of aerosol particles. With the Aerodyne aerosol mass spectrometer (AMS) equipped with a light-scattering probe, nonrefractory components of submicron particles with diameters larger than about 300 nm can even be quantified on a single-particle basis. Here, we present a new method for the analysis of AMS single-particle mass spectra. The developed algorithm classifies the particles according to their components (e. g. sulphate, nitrate, different types of organics) and simultaneously provides quantitative information about the composition of the single particles. This classification algorithm was validated by applying it to data acquired in laboratory experiments with particles of known composition, and applied to field data acquired during the MEGAPOLI summer campaign (July 2009) in Paris. As shown, it is not only possible to directly measure the mixing state of atmospheric particles, but also to directly observe repartitioning of semi-volatile species between gas and particle phase during the course of the day