Aerodyne aerosol mass spectrometer (AMS) and Aerodyne aerosol chemical speciation monitor (ACSM) mass spectra are widely used to quantify organic aerosol (OA) elemental composition, oxidation state, ...and major environmental sources. The OA CO2 + fragment is among the most important measurements for such analyses. Here, we show that a non-OA CO2 + signal can arise from reactions on the particle vaporizer, ion chamber, or both, induced by thermal decomposition products of inorganic salts. In our tests (eight instruments, n = 29), ammonium nitrate (NH4NO3) causes a median CO2 + interference signal of +3.4% relative to nitrate. This interference is highly variable between instruments and with measurement history (percentiles P 10–90 = +0.4 to +10.2%). Other semi-refractory nitrate salts showed 2–10 times enhanced interference compared to that of NH4NO3, while the ammonium sulfate ((NH4)2SO4) induced interference was 3–10 times lower. Propagation of the CO2 + interference to other ions during standard AMS and ACSM data analysis affects the calculated OA mass, mass spectra, molecular oxygen-to-carbon ratio (O/C), and f 44. The resulting bias may be trivial for most ambient data sets but can be significant for aerosol with higher inorganic fractions (>50%), e.g., for low ambient temperatures, or laboratory experiments. The large variation between instruments makes it imperative to regularly quantify this effect on individual AMS and ACSM systems.
The measurement of elements in PM10 was performed with 1 h time resolution at a rural freeway site during summer 2015 in Switzerland using the Xact1 625 Ambient Metals Monitor. On average the Xact ...elements (without accounting for oxygen and other associated elements) make up about 20 % of the total PM10 mass (14.6 µg m−3). We conducted source apportionment by positive matrix factorisation (PMF) of the
elemental mass measurable by the Xact (i.e. major elements heavier than
Al), defined here as PM10el. Eight different sources were identified in PM10el (elemental PM10) mass driven by the sum of 14 elements (notable elements in brackets): Fireworks-I (K, S, Ba and Cl), Fireworks-II (K), sea salt (Cl), secondary sulfate (S), background dust (Si, Ti), road dust (Ca), non-exhaust traffic-related elements (Fe) and industrial elements (Zn and Pb). The major components were secondary sulfate and non-exhaust traffic-related elements followed by background dust and road dust factors, explaining 21 %, 20 %, 18 % and 16 % of the analysed PM10 elemental mass, respectively, with the factor mass not corrected for oxygen content. Further, there were minor contributions (on the order of a few percent) of sea salt and industrial sources. The regionally influenced secondary sulfate factor showed negligible resuspension, and concentrations were similar throughout the day. The significant loads of the non-exhaust traffic-related and road dust factors with strong diurnal variations highlight the continuing importance of vehicle-related air pollutants at this site. Enhanced control of PMF implemented via the SourceFinder software (SoFi Pro version 6.2, PSI, Switzerland) allowed for a successful apportionment of transient sources such as the two firework factors and sea salt, which remained mixed when analysed by unconstrained PMF.
Particulate matter (PM) pollution is a severe environmental problem in the Beijing–Tianjin–Hebei (BTH) region in North
China. PM studies have been conducted extensively in Beijing, but the
chemical ...composition, sources, and atmospheric processes of PM are still
relatively less known in nearby Tianjin and Hebei. In this study, fine PM
in urban Shijiazhuang (the capital of Hebei Province) was characterized using
an Aerodyne quadrupole aerosol chemical speciation monitor (Q-ACSM) from
11 January to 18 February in 2014. The average mass concentration of
non-refractory submicron PM (diameter <1 µm, NR-PM1) was
178±101 µg m−3, and it was composed of 50 % organic aerosol
(OA), 21 % sulfate, 12 % nitrate, 11 % ammonium, and 6 % chloride.
Using the multilinear engine (ME-2) receptor model, five OA sources were
identified and quantified, including hydrocarbon-like OA from vehicle
emissions (HOA, 13 %), cooking OA (COA, 16 %), biomass burning OA (BBOA,
17 %), coal combustion OA (CCOA, 27 %), and oxygenated OA (OOA, 27 %).
We found that secondary formation contributed substantially to PM in episodic
events, whereas primary emissions were dominant (most significant) on average.
The episodic events with the highest NR-PM1 mass range of
300–360 µg m−3 were comprised of 55 % of secondary species. On the
contrary, a campaign-average low OOA fraction (27 %) in OA indicated the
importance of primary emissions, and a low sulfur oxidation degree
(FSO4) of 0.18 even at RH >90 % hinted at insufficient
oxidation. These results suggested that in Shijiazhuang in wintertime fine PM
was mostly from primary emissions without sufficient atmospheric aging,
indicating opportunities for air quality improvement by mitigating direct
emissions. In addition, secondary inorganic and organic (OOA) species
dominated in pollution events with high-RH conditions, most likely due to
enhanced aqueous-phase chemistry, whereas primary organic aerosol (POA)
dominated in pollution events with low-RH and stagnant conditions. These
results also highlighted the importance of meteorological conditions for PM
pollution in this highly polluted city in North China.
We collected 1 year of aerosol chemical speciation monitor (ACSM) data in
Magadino, a village located in the south of the Swiss Alpine region, one of
Switzerland's most polluted areas. We analysed ...the mass spectra of organic
aerosol (OA) by positive matrix factorisation (PMF) using Source Finder
Professional (SoFi Pro) to retrieve the origins of OA. Therein, we deployed
a rolling algorithm, which is closer to the measurement, to account for the temporal changes in the source
profiles. As the first-ever application
of rolling PMF with multilinear engine (ME-2) analysis on a yearlong dataset that was collected
from a rural site, we resolved two primary OA factors (traffic-related
hydrocarbon-like OA (HOA) and biomass burning OA (BBOA)), one mass-to-charge
ratio (m/z) 58-related OA (58-OA) factor, a less oxidised oxygenated OA
(LO-OOA) factor, and a more oxidised oxygenated OA (MO-OOA) factor. HOA
showed stable contributions to the total OA through the whole year ranging
from 8.1 % to 10.1 %, while the contribution of BBOA showed an apparent
seasonal variation with a range of 8.3 %–27.4 % (highest during winter,
lowest during summer) and a yearly average of 17.1 %. OOA (sum of LO-OOA
and MO-OOA) contributed 71.6 % of the OA mass, varying from 62.5 % (in
winter) to 78 % (in spring and summer). The 58-OA factor mainly contained
nitrogen-related variables which appeared to be pronounced only after
the filament switched. However, since the contribution of this factor was
insignificant (2.1 %), we did not attempt to interpolate its potential
source in this work. The uncertainties (σ) for the modelled OA
factors (i.e. rotational uncertainty and statistical variability in the
sources) varied from ±4 % (58-OA) to a maximum of ±40 %
(LO-OOA). Considering that BBOA and LO-OOA (showing influences of biomass
burning in winter) had significant contributions to the total OA mass, we
suggest reducing and controlling biomass-burning-related residential heating as a mitigation
strategy for better air quality and lower PM levels in this region or
similar locations. In Appendix A, we conduct a head-to-head comparison
between the conventional seasonal PMF analysis and the rolling mechanism. We
find similar or slightly improved results in terms of mass concentrations,
correlations with external tracers, and factor profiles of the constrained
POA factors. The rolling results show smaller scaled residuals and enhanced
correlations between OOA factors and corresponding inorganic salts compared to
those of the seasonal solutions, which was most likely because the rolling
PMF analysis can capture the temporal variations in the oxidation processes
for OOA components. Specifically, the time-dependent factor profiles of
MO-OOA and LO-OOA can well explain the temporal viabilities of two main ions
for OOA factors, m/z 44 (CO2+) and m/z 43 (mostly
C2H3O+). Therefore, this rolling PMF analysis provides a more
realistic source apportionment (SA) solution with time-dependent OA sources.
The rolling results also show good agreement with offline Aerodyne aerosol
mass spectrometer (AMS) SA results from filter samples, except for in winter.
The latter discrepancy is likely because the online measurement can capture
the fast oxidation processes of biomass burning sources, in contrast to the
24 h filter samples. This study demonstrates the strengths of the rolling
mechanism, provides a comprehensive criterion list for ACSM users to
obtain reproducible SA results, and is a role model for similar analyses of
such worldwide available data.
The Xact 625 Ambient Metals Monitor was tested during a 3-week field campaign at the rural, traffic-influenced site Härkingen in Switzerland during the summer of 2015. The field campaign encompassed ...the Swiss National Day fireworks event, providing increased concentrations and unique chemical signatures compared to non-fireworks (or background) periods. The objective was to evaluate the data quality by intercomparison with other independent measurements and test its applicability for aerosol source quantification. The Xact was configured to measure 24 elements in PM10 with 1 h time resolution. Data quality was evaluated for 10 24 h averages of Xact data by intercomparison with 24 h PM10 filter data analysed with ICP-OES for major elements, ICP-MS for trace elements, and gold amalgamation atomic absorption spectrometry for Hg. Ten elements (S, K, Ca, Ti, Mn, Fe, Cu, Zn, Ba, Pb) showed excellent correlation between the compared methods, with r2 values ≥ 0.95. However, the slopes of the regressions between Xact 625 and ICP data varied from 0.97 to 1.8 (average 1.28) and thus indicated generally higher Xact elemental concentrations than ICP for these elements. Possible reasons for these differences are discussed, but further investigations are needed. For the remaining elements no conclusions could be drawn about their quantification for various reasons, mainly detection limit issues. An indirect intercomparison of hourly values was performed for the fireworks peak, which brought good agreement of total masses when the Xact data were corrected with the regressions from the 24 h value intercomparison. The results demonstrate that multi-metal characterization at high-time-resolution capability of Xact is a valuable and practical tool for ambient monitoring.
Zusammenfassung
Beim Jumping-Stump-Phänomen handelt es sich um unwillkürliche, zum Teil sehr schmerzhafte, semirhythmische Spasmen des Amputationsstumpfes mit Bewegungseffekt – also um Myoklonien, ...die in zeitlichem Abstand zur Amputation auftreten und dann persistieren. Eine schwere Gewebsschädigung scheint dafür prädisponierend zu sein. Die Therapie des Jumping-Stump-Syndroms ist schwierig und beinhaltet auch die Anwendung von Botulinumtoxin. Klinisches Bild, Differenzialdiagnostik, pathogenetische Zuordnung und mögliche therapeutische Ansätze werden anhand eines Fallbeispiels dargestellt und diskutiert.
Reactive oxygen species (ROS) are believed to contribute
to the adverse health effects of aerosols. This may happen by inhaled
particle-bound (exogenic) ROS (PB-ROS) or by ROS formed within the
...respiratory tract by certain aerosol components (endogenic ROS). We
investigated the chemical composition of aerosols and their exogenic ROS
content at the two contrasting locations Beijing (China) and Bern
(Switzerland). We apportioned the ambient organic aerosol to different
sources and attributed the observed water-soluble PB-ROS to them. The
oxygenated organic aerosol (OOA, a proxy for secondary organic aerosol, SOA)
explained the highest fraction of the exogenic ROS concentration variance at
both locations. We also characterized primary and secondary aerosol
emissions generated from different biogenic and anthropogenic sources in
smog chamber experiments. The exogenic PB-ROS content in the OOA from these
emission sources was comparable to that in the ambient measurements. Our
results imply that SOA from gaseous precursors of different anthropogenic
emission sources is a crucial source of water-soluble PB-ROS and should be
additionally considered in toxicological and epidemiological studies in an
adequate way besides primary emissions. The importance of PB-ROS may be
connected to the seasonal trends in health effects of PM reported by
epidemiological studies, with elevated incidences of adverse effects in
warmer seasons, which are accompanied by more-intense atmospheric oxidation
processes.
Fine particulate matter (PM) levels and resulting impacts on human health are in the Po Valley (Italy) among the highest in Europe. To build effective PM abatement strategies, it is necessary to ...characterize fine PM chemical composition, sources and atmospheric processes on long timescales (> months), with short time resolution (< day), and with particular emphasis on the predominant organic fraction. Although previous studies have been conducted in this region, none of them addressed all these aspects together. For the first time in the Po Valley, we investigate the chemical composition of nonrefractory submicron PM (NR-PM1) with a time resolution of 30 min at the regional background site of Ispra during 1 full year, using the Aerodyne Aerosol Chemical Speciation Monitor (ACSM) under the most up-to-date and stringent quality assurance protocol. The identification of the main components of the organic fraction is made using the Multilinear-Engine 2 algorithm implemented within the latest version of the SoFi toolkit. In addition, with the aim of a potential implementation of ACSM measurements in European air quality networks as a replacement of traditional filter-based techniques, parallel multiple offline analyses were carried out to assess the performance of the ACSM in the determination of PM chemical species regulated by air quality directives. The annual NR-PM1 level monitored at the study site (14.2 µg m−3) is among the highest in Europe and is even comparable to levels reported in urban areas like New York City and Tokyo. On the annual basis, submicron particles are primarily composed of organic aerosol (OA, 58 % of NR-PM1). This fraction was apportioned into oxygenated OA (OOA, 66 %), hydrocarbon-like OA (HOA, 11 % of OA) and biomass burning OA (BBOA, 23 %). Among the primary sources of OA, biomass burning (23 %) is thus bigger than fossil fuel combustion (11 %). Significant contributions of aged secondary organic aerosol (OOA) are observed throughout the year. The unexpectedly high degree of oxygenation estimated during wintertime is probably due to the contribution of secondary BBOA and the enhancement of aqueous-phase production of OOA during cold months. BBOA and nitrate are the only components of which contributions increase with the NR-PM1 levels. Therefore, biomass burning and NOx emission reductions would be particularly efficient in limiting submicron aerosol pollution events. Abatement strategies conducted during cold seasons appear to be more efficient than annual-based policies. In a broader context, further studies using high-time-resolution analytical techniques on a long-term basis for the characterization of fine aerosol should help better shape our future air quality policies, which constantly need refinement.
Mass spectrometric measurements commonly yield data on hundreds of variables over thousands of points in time. Refining and synthesizing this raw data into chemical information necessitates the use ...of advanced, statistics-based data analytical techniques. In the field of analytical aerosol chemistry, statistical, dimensionality reductive methods have become widespread in the last decade, yet comparable advanced chemometric techniques for data classification and identification remain marginal. Here we present an example of combining data dimensionality reduction (factorization) with exploratory classification (clustering), and show that the results cannot only reproduce and corroborate earlier findings, but also complement and broaden our current perspectives on aerosol chemical classification. We find that applying positive matrix factorization to extract spectral characteristics of the organic component of air pollution plumes, together with an unsupervised clustering algorithm, k-means+ + , for classification, reproduces classical organic aerosol speciation schemes. Applying appropriately chosen metrics for spectral dissimilarity along with optimized data weighting, the source-specific pollution characteristics can be statistically resolved even for spectrally very similar aerosol types, such as different combustion-related anthropogenic aerosol species and atmospheric aerosols with similar degree of oxidation. In addition to the typical oxidation level and source-driven aerosol classification, we were also able to classify and characterize outlier groups that would likely be disregarded in a more conventional analysis. Evaluating solution quality for the classification also provides means to assess the performance of mass spectral similarity metrics and optimize weighting for mass spectral variables. This facilitates algorithm-based evaluation of aerosol spectra, which may prove invaluable for future development of automatic methods for spectra identification and classification. Robust, statistics-based results and data visualizations also provide important clues to a human analyst on the existence and chemical interpretation of data structures. Applying these methods to a test set of data, aerosol mass spectrometric data of organic aerosol from a boreal forest site, yielded five to seven different recurring pollution types from various sources, including traffic, cooking, biomass burning and nearby sawmills. Additionally, three distinct, minor pollution types were discovered and identified as amine-dominated aerosols.
Less than 1 % of patients with Lyme Neuroborreliosis (LNB) present with a cerebrovascular event. Ischaemic strokes occur more commonly than parenchymal or subarachnoid haemorrhages. If cerebral ...vasculitis due to LNB is suspected, antibiotic treatment should be started immediately, which will normally lead to remission. Very rarely progression and recurrent strokes are observed despite sufficient antibiotic therapy, even if steroids are added. Currently there are no guidelines on the adequate treatment of cerebral vasculitis due to LNB which is not responsive to antibiotics and steroids, but in very few reported cases cyclophosphamide led to disease stabilisation. We reviewed the literature regarding cyclophosphamide treatment in these patients and want to share our experience of cyclophosphamide therapy in progressive cerebral vasculitis due to LNB.
We report a 71-year-old female patient with cerebral vasculitis and multiple strokes as a complication of LNB. Progression could only be halted by additional immunosuppressive treatment using cyclophosphamide. However, at that point the patient had already suffered severe ischaemic brain damage. Similarly, in existing case reports cyclophosphamide had been administered only at a time when patients already showed serious neurological deficits.
Cerebral vasculitis in patients with LNB is very rare and normally responds to antibiotic treatment. A minority of patients show disease progression despite antibiotics and steroids. Our case report strengthens the recommendation that in those patients - even if signs of progressive vasculitis are only detectable on imaging and not clinically - cyclophosphamide should be considered without delay to prevent further cerebrovascular events.
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