An upgraded monitor for aerosols and gases in ambient air (MARGA) was applied for one year at the Central European TROPOS research site Melpitz investigating the gas- and particle-phase partitioning ...of formic, acetic, propionic, butyric, glycolic, pyruvic, oxalic, malonic, succinic, malic, and methanesulfonic acid (MSA). Gas- and PM10 particle-phase mean concentrations were 12–445 and 7–31 ng m–3 for monocarboxylic acids (MCAs), between 0.6–8 and 4–31 ng m–3 for dicarboxylic acids (DCAs), and 2 and 31 ng m–3 for MSA, respectively. Assuming full dissolution in nonideal aerosol solutions, empirical noneffective Henry’s law constants (H emp) were calculated and compared with literature values (H lit). Mean H emp were 4.5 × 109–2.2 × 1010 mol L–1 atm–1 for MCAs, 3.6 × 1010–7.5 × 1011 mol L–1 atm–1 for DCAs, and 7.5 × 107 mol L–1 atm–1 for MSA and, thus, factors of 5.1 × 103–9.1 × 105 and 2.5–20.3 higher than their corresponding H lit for MCAs and DCAs, respectively, and 9.0 × 10–5 lower than H lit,MSA. Data analyses and thermodynamic calculations implicate that the formation of chemical association complexes and organic salts inhibits the partitioning of organic acids toward the gas phase and, thus, at least partly explains higher H emp values for both MCAs and summertime DCAs. Low H emp,MSA are unexpected because of the high MSA solubility and are reported here for the first time. Overall, processes responsible for the observed stronger partitioning of carboxylic acids toward the particle phase need to be accounted for in complex multiphase chemistry models affecting the contribution of organic acids to secondary organic aerosol mass, their chemical processing, and lifetime.
A new method has been developed to combine back trajectory statistics with a detailed land cover analysis. It provides numeric proxies for the residence times of sampled air masses above certain land ...cover classes (marine, natural vegetation, agricultural lands, urban areas, and bare areas), as well as further meteorological parameters (mean trajectory length, solar radiation along trajectory, and local height of the boundary mixing layer). The method has been implemented into a GIS-enabled database system to allow for an efficient processing of large datasets with low computational demands. A principal component analysis was performed on a dataset including the modelled residence times, the modelled meteorological parameters, some measured meteorological parameters (wind speed and temperature), and the concentrations of 10 particle constituents (inorganic ions and organic and elemental carbon) in 5 particle size ranges for 29 winter- and summertime samples at an urban background site in Leipzig, Germany. Six principal components could be extracted which together explained about 80% of the total variance in the dataset. The factors could be attributed to the influence of meteorology to continental background pollution, secondary formation processes in polluted air masses, wood burning, aged sea-salt, local traffic, and long-range transported crustal material. The modelled residence times and the meteorological parameters were generally consistent with the existing knowledge of specific particle sources and thereby facilitated and strengthened the interpretation of the factors. Moreover, they allowed for a clear distinction between continental background pollution and secondary formation processes, which has not been possible in previous source apportionment studies. The results demonstrate that the combined usage of back trajectory, land cover, and meteorological data by the presented method yields valuable additional information on the history of sampled air masses, which can improve the quality of source apportionment of atmospheric aerosol constituents.
Methanesulfonic acid (MSA) has been widely used as a proxy for marine biogenic sources, but it is still a challenge to provide an accurate MSA mass concentration with high time resolution. This study ...offers an improved MSA quantification method using high resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). Particularly, the method was validated based on an excellent agreement with parallel offline measurements (slope = 0.88, R 2 = 0.89). This comparison is much better than those using previously reported methods, resulting in underestimations of 31–54% of MSA concentration. With this new method, MSA mass concentrations were obtained during 4 North/South Atlantic cruises in spring and autumn of 2011 and 2012. The seasonal and spatial variation of the particulate MSA mass concentration as well as the MSA to non-sea-salt sulfate ratio (MSA:nssSO4) over the North/South Atlantic Ocean were determined for the first time. Seasonal variation of the MSA mass concentration was observed, with higher values in spring (0.03 μg m–3) than in autumn (0.01 μg m–3). The investigation of MSA:nssSO4 suggests a ubiquitous and significant influence of anthropogenic sources on aerosols in the marine boundary layer.
Size-resolved trace metal concentrations at four sites in Leipzig (Germany) and its surrounding were assessed between the winter of 2013 and the summer of 2015. The measurements were performed in ...parallel at; traffic dominated (Leipzig – Mitte, LMI), traffic and residential dominated (Eisenbahnstrasse, EIB), urban background (TROPOS, TRO) and regional background (Melpitz, MEL) sites. In total, 19 trace metals, i.e. K, Ca, Ti, Mn, Fe, Cu, Zn, As, Se, Ba, V, Pb, Ni, Cr, Sr, Sn, Sb, Co and Rb were analysed using total reflection x-ray fluorescence (TXRF). The major metals were Fe, K and Ca with concentrations ranging between; 31–440 ng/m3, 42–153 ng/m3 and 24–322 ng/m3, respectively, while the trace metals with the lowest concentrations were Co, Rb and Se with concentrations of; < 0.3 ng/m3, <0.5 ng/m3 and 0.5–0.7 ng/m3, respectively. PM10 trace metal concentrations during easterly air mass inflow especially at the background sites were in average 70% higher in the winter and 30% higher in the summer in comparison to westerly air mass inflow.
Traffic at LMI contributed to about 75% of Cr, Ba, Cu, Sb, Sn, Ca, Co, Mn, Fe and Ti concentrations while regional activities contributed to more than 70% of K, Rb, Pb, Se, As and V concentrations. Traffic dominated trace metals were often observed in the coarse mode while the regional background dominated trace metals were often observed in the fine mode. Trace metal sources were related to crustal matter and road dust re-suspension for metals such as Ca, Fe, Co, Sr, and Ti, brake and tire wear (Cu, Sb, Ba, Fe, Zn, Pb), biomass burning (K, Rb), oil and coal combustion (V, Zn, As, Pb). Crustal matter contributed 5–12% in winter and 8–19% in summer of the PM10 mass. Using Cu and Zn as markers for brake and tire wear, respectively, the estimated brake and tire wear contributions to the PM10 mass were 0.1–0.8% and 1.7–2.9%, respectively. The higher contributions were observed at the traffic sites while the lower contributions were observed at the regional background site. In total, non-exhaust emissions could account for about 10–22% of the PM10 mass in the summer and about 7–15% of the PM10 mass in the winter.
•Size-resolved trace metal levels were assessed at traffic, urban and regional sites.•Sources were traffic, crustal matter, biomass burning and coal combustion.•Cu and Zn were used as markers to estimate brake and tire wear, respectively.•Brake and tire wear contributed up to 0.8% and 2.9%, respectively, to the PM10 mass.•Non-exhaust emissions contributed up to 22% (summer) and 15% (winter) to PM10.
Atmospheric particles and droplets contain numerous organic substances, some of which form complexes with metal ions, significantly affecting bulk physicochemical properties and chemical reactivity. ...However, the detection and identification of complexing agents and their corresponding metal complexes remains an analytical challenge. In this study, we developed an LC/HRMS nontarget screening (NTS) approach which allows the selective detection of complexing agents in aerosol particle extracts and rainwater. To achieve this, a T-junction is installed between the LC outlet and the ion source, and a FeCl3 solution is added for postcolumn complexation. The resulting mass spectra are screened for the three characteristic iron(III)-complexes M – H + FeCl3−, M – 2H + FeCl2−, and M – 3H + FeCl− with mass differences (Δm/z) between the complexing agent and the iron complex of 160.8416, 124.8648, and 89.8959, respectively. Up to 29 di- or tricarboxylic acids were identified as complexing agents in aerosol particle samples from two different sites (Melpitz, Germany, and Wangdu, China) at concentrations as low as 50 nM. Thirteen complexing agents were detected even in measurements without postcolumn iron addition from complexation with background Fe3+ traces from the analytical system. At least for the highest concentrated complexing agents, the proposed screening approach can thus be exploited in a NTS approach without any device modification. Besides carboxylic acids, 4-nitrophenol and 4-nitrocatechol were identified as further complexing agents, demonstrating the applicability of the approach to other matrices and to a range of different complexing agents.
Trans-boundary PM10 transport into eastern Germany was quantified by comparing mean PM10 concentrations during western and eastern air mass inflow under similar meteorological conditions and ...calculating an “increment East” as a proxy for the trans-boundary PM10 fraction. Data of 10 measurement stations located in Berlin, Brandenburg, Mecklenburg-Western Pomerania and Saxony were used for winter 2016/17 and revealed trans-boundary PM10 increments of 0–30 μg m−3 on average, depending on meteorological conditions. On average over all days with positive increments, trans-boundary transport contributed 13 μg m−3 or 44% to the total PM10 concentration in the regional background. During pollution periods with elevated PM10 concentrations of >30 μg m−3 at rural background sites, this contribution lied between 44 and 62%, while it decreased to about 20% for moderate PM10 concentrations between 20 and 30 μg m−3 and was negligible for PM10 concentrations <20 μg m−3. Based on its chemical composition, PM10 was apportioned to 6–7 different sources by positive matrix factorisation (PMF) receptor modelling. It was found that typically >80% of the trans-boundary PM10 fraction imported from eastern neighbouring countries can be explained by combustion emissions and formation of secondary particle mass, i.e. ammonium sulfate and organic matter, with the latter typically exceeding the contributions from combustion. Source contributions of these two PMF factors within the increment East were correlated, indicating combustion-related emissions of SO2 and volatile organic compounds leading to the observed secondary trans-boundary PM10 mass. Higher increment East values for cold than for warm days imply emissions from domestic heating in eastern European countries, presumably from the combustion of solid fuels such as wood and coal, as the dominant source for trans-boundary PM10 in eastern Germany. A case study for a traffic-impacted pollution hotspot in the city of Berlin showed an average contribution of about 30% from trans-boundary transport, while regional background, urban background and local traffic emissions explained about 40, 10, and 20% of PM10 mass concentrations during days with eastern air mass inflow where the increment East approach could be applied together with the incremental Lenschow approach. The results of this study reinforce the need of PM10 mitigation measures at different spatial scales, ranging from municipal to international levels.
Display omitted
•Observations and receptor modelling were used to study trans-boundary PM10.•Trans-boundary PM10 from eastern Europe was quantified to range from 0 to 30 μg m−3•Its contribution was 44–62% of total PM10 during pollution periods at rural sites.•Main source was combustion emissions, likely from solid fuels for domestic heating.
Atmospheric ultrafine particles (UFP) are high in number but low in mass. Because of the ability to reach deeply into the lungs UFP can influence human health. Chemical analysis of UFP is to some ...extent possible after sampling by means of low pressure impactors. Main component classes of compounds in UFP are organic and elemental carbon and the water soluble ions ammonium, sulfate and nitrate. Single organic compounds such as polycyclic aromatic compounds, alkanes or levoglucosan can also be measured. Primary emissions of traffic and stationary combustion processes are one and secondary formation in the atmosphere from gaseous precursors is another major source. Organic matter and elemental carbon contribute up to 75 % to the mass of UFP. Parallel sampling at three locations, influenced by different emissions, helped to identify sources of particles.
Ultrafine particles (UFP) can be easily counted but chemical analysis poses a challenge for atmospheric chemistry. Constituents and sources can be identified by parallel sampling at different sites. Traffic, wood burning and secondary atmospheric formation are important sources. Carbonaceous material dominates UFP with up to 75 % of mass.
A capillary electrophoresis/electrospray ionisation mass spectrometry (CE/ESI-MS) method was developed for the determination of 38 organic acids in atmospheric particles and cloud water. The target ...analytes include many functionalised carboxylic acids, such as carboxylic acids with additional oxo-, hydroxy- or nitro-groups. These compounds are of large interest as their determination might give new insights into the atmospheric multiphase chemistry. OASIS HLB sorbent material (Waters) was used to extract and enrich polar carboxylic acids from aqueous solutions with recoveries greater than 80% for most analytes. Relative standard deviations in the range of 4–20% for peak areas (
n
=
5), including the SPE step, and 0.2–0.5% (
n
=
8) for migration times were found. The limits of detection (S/N
=
3) ranged from 0.005 to 0.6
μmol
l
−1 for an ion-trap mass spectrometer and from 0.0004 to 0.08
μmol
l
−1 for a time-of-flight mass spectrometer. These detection limits translate into atmospheric concentrations in the low pg
m
−3 range based on the experimental conditions in this study. Severe matrix effects were observed for real samples, arising from complex co-extracted organic material. However, using the method of standard addition, most of the analytes could successfully be quantified in samples of ambient particles and cloud water with concentrations in the low ng
m
−3 to high pg
m
−3 range. These results demonstrate the suitability of the proposed method for the determination of a wide range of polar carboxylic acids at low concentrations in complex samples of different atmospheric phases.
To study the complex compound mixture in atmospheric aerosol particles often referred to as “humic-like substances” (HULIS), a recently developed 2D fractionation method combining size-exclusion ...chromatography and reversed-phase liquid chromatography was applied to a set of 55 aerosol particle samples from five different sampling locations. The resulting heat maps, showing the 2D molecular weight versus polarity space, revealed a distinct seasonal and regional variability in the composition of solid-phase extracted water-soluble organic carbon (WSOC). Different sources were assigned to specific areas of the heat maps based on correlations with atmospheric markers. Biomass burning and secondary organic aerosol formation were found to be the most important sources, both assigned to the largest areas of the heat maps with up to 77 and 69% contribution to the total solid-phase extracted WSOC mass of individual sample clusters, respectively. Coal combustion (14–24%), traffic and industry (4–9%), and soil-derived fulvic acids (5–10%), all assigned to smaller areas of the heat maps, were identified as additional sources. Comparison with the 2D heat map of Suwannee River fulvic acids (SRFAs), a commonly used HULIS surrogate, revealed that only 37–55% of the solid-phase-extracted WSOC occupied similar areas in the molecular weight versus polarity space as SRFA. It is, therefore, suggested that only this fraction might qualify as real atmospheric “HULIS”, while for the broad compound mixture obtained after solid-phase extraction (SPE), denominations like SPE-WSOC or WSOCSPE seem more appropriate.
PDF
