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.
Hourly trace element measurements were performed in an urban street canyon and next to an interurban freeway in Switzerland during more than one month each, deploying a rotating drum impactor (RDI) ...and subsequent sample analysis by synchrotron radiation X-ray fluorescence spectrometry (SR-XRF). Antimony and other brake wear associated elements were detected in three particle size ranges (2.5−10, 1−2.5, and 0.1−1 μm). The hourly measurements revealed that the effect of resuspended road dust has to be taken into account for the calculation of vehicle emission factors. Individual values for light and heavy duty vehicles were obtained for stop-and-go traffic in the urban street canyon. Mass based brake wear emissions were predominantly found in the coarse particle fraction. For antimony, determined emission factors were 11 ± 7 and 86 ± 42 μg km−1 vehicle−1 for light and heavy duty vehicles, respectively. Antimony emissions along the interurban freeway with free-flowing traffic were significantly lower. Relative patterns for brake wear related elements were very similar for both considered locations. Beside vehicle type specific brake wear emissions, road dust resuspension was found to be a dominant contributor of antimony in the street canyon.
Measuring the chemical composition of ambient particulate matter in different size classes is a relevant gain in information, which can be used for improved source apportionment. The design and ...implementation of a switching system between a PM10 and a PM2.5 inlet for an Xact 625i ambient metals monitor is presented. First applications in the field reveal its practicability and applicability to determine the PM2.5/PM10 ratio. For example, in Beijing crustal elements such as Si, Ca, or Ti occur mainly in the coarse fraction (ratio < 0.2), whereas combustion related elements such as Se, Pb or As are found mainly in the fine fraction (ratio > 0.8). Simulations of the uncertainty caused by alternating sampling of the two size classes show that the increase of uncertainty is within acceptable limits, depending on the characteristics of the time series. The gain in information outweighs the increase of uncertainty in most cases.
Display omitted
•The system allows for alternating PM10 and PM2.5 sampling with a single instrument.•Alternating sampling in two size classes provides a gain in information on aerosols.•Increase of uncertainty in the measured time series is within acceptable limits.
Delhi, the capital of India, suffers from heavy local emissions as well as regional transport of air pollutants, resulting in severe aerosol loadings. To determine the sources of these pollutants, we ...have quantified the mass concentrations of 26 elements in airborne particles, measured by an online X-ray fluorescence spectrometer with time resolution between 30 min and 1 h. Measurements of PM10 and PM2.5 (particulate matter <10 μm and < 2.5 μm) were conducted during two consecutive winters (2018 and 2019) in Delhi. On average, 26 elements from Al to Pb made up ~25% and ~19% of the total PM10 mass (271 μg m−3 and 300 μg m−3) in 2018 and 2019, respectively. Nine different aerosol sources were identified during both winters using positive matrix factorization (PMF), including dust, non-exhaust, an S-rich factor, two solid fuel combustion (SFC) factors and four industrial/combustion factors related to plume events (Cr-Ni-Mn, Cu-Cd-Pb, Pb-Sn-Se and Cl-Br-Se). All factors were resolved in both size ranges (but varying relative concentrations), comprising the following contributions to the elemental PM10 mass (in % average for 2018 and 2019): Cl-Br-Se (41.5%, 36.9%), dust (27.6%, 28.7%), non-exhaust (16.2%, 13.7%), S-rich (6.9%, 9.2%), SFC1 + SFC2 (4%, 7%), Pb-Sn-Se (2.3%, 1.66%), Cu-Cd-Pb (0.67%, 2.2%) and Cr-Ni-Mn (0.57%, 0.47%). Most of these sources had the highest relative contributions during late night (22:00 local time (LT)) and early morning hours (between 03:00 to 08:00 LT), which is consistent with enhanced emissions into a shallow boundary layer. Modelling of airmass source geography revealed that the Pb-Sn-Se, Cl-Br-Se and SFC2 factors prevailed for northwest winds (Pakistan, Punjab, Haryana and Delhi), while the Cu-Cd-Pb and S-rich factors originated from east (Nepal and Uttar Pradesh) and the Cr-Ni-Mn factor from northeast (Uttar Pradesh). In contrast, SFC1, dust and non-exhaust were not associated with any specific wind direction.
Display omitted
•Quantified highly time-resolved elements in PM10 and PM2.5 in Delhi during winters•Source apportionment was improved combining receptor model and trajectory analysis.•Major PM10 elemental constituents were Cl, S and crustal elements (Si, Ca, Ti, Fe).•Northwest and east were the most influential source regions for various sources.
The international field experiment Pianura Padana Produzione di Ozono (PIPAPO) studying the volatile organic compounds (VOC)/NOx ozone production sensitivity took place in May and June 1998 downwind ...of the metropolitan area of Milan. The project was embedded in the framework of the EUROTRAC‐2 Limitation of Oxidant Production (LOOP) subproject. Several ground stations between the city of Milan and the Alps north of Milan combined with airborne measurements delivered a comprehensive data set suitable for observation‐based analysis and validation of chemical transport models. The special section devoted to the PIPAPO project contains 10 contributions on the characterization of secondary aerosol formation, and radical precursors, and the characterization of ozone production sensitivity based on field measurements and numerical model simulations. In this paper the scientific background and the major objectives of PIPAPO are described. An overview of the field measurement program, the study site, and the meteorological conditions prevailing during the experiment are given. A general conclusion of the combined results is that under typical summer conditions in the Milan area with clear skies, low wind speeds and high temperatures, the transition from VOC‐ to NOx‐sensitive ozone production occurs a few tens of kilometers downwind of the strongest emission sources in the city of Milan.
Characteristics and sources of ambient particle elements in urban Beijing were studied by hourly observations in two size fractions (PM10 and PM2.5) during November and December 2017 using an online ...multi-element analyzer. The reconstructed oxide concentrations of 24 elements (from Al to Pb) comprise an appreciable fraction of PM10 and PM2.5, accounting for 37% and 17%, respectively on average. We demonstrate the benefit of using high-time-resolution chemical speciation data in achieving robust source apportionment of the total elemental PM10 (PM10el) and elemental PM2.5 (PM2.5el) mass using positive matrix factorization (PMF). Biomass burning, coal combustion, secondary sulfate, industry, non-exhaust traffic and dust were identified in both size fractions (with varying relative concentrations), which accounted on average for 4%, 12%, 5%, 2%, 14%, and 63%, respectively to the total PM10el, and 14%, 35%, 21%, 6%, 12% and 12%, respectively to the total PM2.5el. Biomass burning and coal combustion exhibited higher concentrations during haze episodes of the heating season. In contrast, secondary sulfate and industry contributed more to haze episodes during the non-heating season. The fractional contribution of dust was mostly high during clean days, while the fractional non-exhaust traffic emission contribution was similar throughout the measurement period. The non-exhaust traffic emissions contributed locally, while the remaining sources were dominated by neighboring areas. Furthermore, trajectory analysis showed that the origin of the industrial sources roughly agreed with the locations of the main point sources. Overall, this work provides detailed information on the characteristics of the elements during different haze events during heating and non-heating seasons.
Display omitted
•Quantified highly time-resolved elements in PM10 and PM2.5 in Beijing.•Reconstructed oxides concentrations of elements amounted to 37% and 17% of the total PM10 and PM2.5 mass, respectively.•Coal combustion was predominant in haze episodes during the heating season.•Southwestern and southern domains were the most influential source regions.
Kraków is routinely affected by very high air pollution levels, especially during the winter months. Although a lot of effort has been made to characterize ambient aerosol, there is a lack of online ...and long-term measurements of non-refractory aerosol. Our measurements at the AGH University of Science and Technology provide the online long-term chemical composition of ambient submicron particulate matter (PM1) between January 2018 and April 2019. Here we report the chemical characterization of non-refractory submicron aerosol and source apportionment of the organic fraction by positive matrix factorization (PMF). In contrast to other long-term source apportionment studies, we let a small PMF window roll over the dataset instead of performing PMF over the full dataset or on separate seasons. In this way, the seasonal variation in the source profiles can be captured. The uncertainties in the PMF solutions are addressed by the bootstrap resampling strategy and the random a-value approach for constrained factors.We observe clear seasonal patterns in the concentration and composition of PM1, with high concentrations during the winter months and lower concentrations during the summer months. Organics are the dominant species throughout the campaign. Five organic aerosol (OA) factors are resolved, of which three are of a primary nature (hydrocarbon-like OA (HOA), biomass burning OA (BBOA) and coal combustion OA (CCOA)) and two are of a secondary nature (more oxidized oxygenated OA (MO-OOA) and less oxidized oxygenated OA (LO-OOA)). While HOA contributes on average 8.6 % ± 2.3 % throughout the campaign, the solid-fuel-combustion-related BBOA and CCOA show a clear seasonal trend with average contributions of 10.4 % ± 2.7 % and 14.1 %, ±2.1 %, respectively. Not only BBOA but also CCOA is associated with residential heating because of the pronounced yearly cycle where the highest contributions are observed during wintertime. Throughout the campaign, the OOA can be separated into MO-OOA and LO-OOA with average contributions of 38.4 % ± 8.4 % and 28.5 % ± 11.2 %, respectively.
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.
PDF
