A new method to retrieve the real part of the equivalent refractive index of atmospheric aerosols

This document is the Accepted Manuscript version of the following article: S. Vratolis, et al, ‘A new method to retrieve the real part of the equivalent refractive index of atmospheric aerosols’, Journal of Aerosol Science, Vol. 117: 54-62, March 2018. Under embargo until 29 December 2019. The final, published version is available online at DOI: https://doi.org/10.1016/j.jaerosci.2017.12.013.In the context of the international experimental campaign Hygroscopic Aerosols to Cloud Droplets (HygrA-CD, 15 May to 22 June 2014), dry aerosol size distributions were measured at Demokritos station (DEM) using a Scanning Mobility Particle Sizer (SMPS) in the size range from 10 to 550 nm (electrical mobility diameter), and an Optical Particle Counter (OPC model Grimm 107 operating at the laser wavelength of 660 nm) to acquire the particle size distribution in the size range of 250 nm to 2.5 μm optical diameter. This work describes a method that was developed to align size distributions in the overlapping range of the SMPS and the OPC, thus allowing us to retrieve the real part of the aerosol equivalent refractive index (ERI). The objective is to show that size distribution data acquired at in situ measurement stations can provide an insight to the physical and chemical properties of aerosol particles, leading to better understanding of aerosol impact on human health and earth radiative balance. The resulting ERI could be used in radiative transfer models to assess aerosol forcing direct effect, as well as an index of aerosol chemical composition. To validate the method, a series of calibration experiments were performed using compounds with known refractive index (RI). This led to a corrected version of the ERI values, (ERICOR). The ERICOR values were subsequently compared to model estimates of RI values, based on measured PM2.5 chemical composition, and to aerosol RI retrieved values by inverted lidar measurements on selected days.Peer reviewe

Quantitative assessment of the variability in chemical profiles from source apportionment analysis of PM10 and PM2.5 at different sites within a large metropolitan area

The study aims to assess the differences between the chemical profiles of the major anthropogenic and natural PM sources in two areas with different levels of urbanization and traffic density within the same urban agglomeration. A traffic site and an urban background site in the Athens Metropolitan Area have been selected for this comparison. For both sites, eight sources were identified, with seven of them being common for the two sites (Mineral Dust, non-Exhaust Emissions, Exhaust Emissions, Heavy Oil Combustion, Sulfates & Organics, Sea Salt and Biomass Burning) and one, site-specific (Nitrates for the traffic site and Aged Sea Salt for the urban background site). The similarity between the source profiles was quantified using two statistical analysis tools, Pearson correlation (PC) and Standardized Identity Distance (SID). According to Pearson coefficients five out of the eight source profiles present high (PC > 0.8) correlation (Mineral Dust, Biomass Burning, Sea Salt, Sulfates and Heavy Oil Combustion), one presented moderate (0.8 > PC > 0.6) correlation (Exhaust) and two low/no (PC < 0.6) correlation (non-Exhaust, Nitrates/Aged Sea Salt). The source profiles that appear to be more correlated are those of sources that are not expected to have high spatial variability because there are either natural/secondary and thus have a regional character or are emitted outside the urban agglomeration and are transported to both sites. According to SID four out of the eight sources have high statistical correlation (SID < 1) in the two sites (Mineral Dust, Sea salt, Sulfates, Heavy Oil Combustion). Biomass Burning was found to be the source that yielded different results from the two methodologies. The careful examination of the source profile of that source revealed the reason for this discrepancy. SID takes all the species of the profile equally into account, while PC might be disproportionally affected by a few numbers of species with very high concentrations. It is suggested, based on the findings of this work, that the combined use of both tools can lead the users to a thorough evaluation of the similarity of source profiles. This work is, to the best of our knowledge, the first time a study is focused on the quantitative comparison of the source profiles for sites inside the same urban agglomeration using statistical indicators.The study was supported by “CALIBRA/EYIE” (MIS 5002799) and “PANhellenic infrastructure for Atmospheric Composition and climatE change” (MIS 5021516) implemented under the Action “Reinforcement of the Research and Innovation Infrastructure”, funded by the Operational Programme “Competitiveness, Entrepreneurship and Innovation” (NSRF 2014–2020) and co-financed by Greece and the European Union (European Regional Development Fund). Collection and chemical analysis of samples were supported by LIFE + AIRUSE EU project (ENV/ES/584). Partial support was also received by H2020 ERAPLANET/SMURBS ERANET GA No 689443.Peer reviewe

Combined organic and inorganic source apportionment on yearlong ToF-ACSM dataset at a suburban station in Athens

The current improvements in aerosol mass spectrometers in resolution and sensitivity, and the analytical tools for mass spectra deconvolution, have enabled the in-depth analysis of ambient organic aerosol (OA) properties. Although OA constitutes a major fraction of ambient aerosol, its properties are determined to a great extent by the mixing characteristics of both organic and inorganic components of ambient aerosol. This work applies a new methodology to a year-long ACSM dataset to assess the sources of organic and total non-refractory species in the Athens background aerosol and provides insights into the interactions between organic and inorganic species. The use of innovative tools for applying positive matrix factorization (PMF, rolling window) enables the study of the temporal variability of the contribution of these sources and seasonal changes in their composition. The mass spectra of both organic and inorganic aerosol were obtained by a time-of-flight aerosol mass spectrometer (ToF-ACSM) for PMF analysis. The results revealed five factors when organic aerosol was analysed separately. Three of them were primary OA factors: hydrocarbon-like organic aerosol (HOA), cooking-related organic aerosol (COA) and biomass burning organic aerosol (BBOA). The remaining two were secondary, less and more oxidized oxygenated organic aerosol (LO-OOA and MO-OOA respectively). The relative contributions of these factors were HOA 15 %, COA 18 %, BBOA 9 %, MO-OOA 34 % and LO-OOA 24 % (yearly averaged). When a combined organic and inorganic aerosol matrix was analysed, two additional factors were identified that were mainly composed of ammonium sulfate (83.5 %) and ammonium nitrate (73 %). Moreover, two secondary factors were resolved, containing both organics and inorganics and were named more (MOA) and less oxidized aerosol (LOA). The relative contributions on a yearly average of these factors were HOA 7 %, COA 9 %, BBOA 3 %, ammonium nitrate 3 %, ammonium sulfate 28 %, MOA 24 % and LOA 26 %

A new method for the quantification of ambient particulate-matter emission fluxes

An inversion method has been developed in order to quantify the emission fluxes of certain aerosol pollution sources across a wide region in the Northern Hemisphere, mainly in Europe and western Asia. The data employed are the aerosol contribution factors deducted by positive matrix factorization (PMF) on a PM2.5 chemical composition dataset from 16 European and Asian cities for the period 2014 to 2016. The spatial resolution of the method corresponds to the geographic grid cell size of the Lagrangian particle dispersion model (Flexible Particle Dispersion Model, FLEXPART, 1∘ × 1∘) which was utilized for the air mass backward simulations. The area covered is also related to the location of the 16 cities under study. Species with an aerodynamic geometric mean diameter of 400 nm and 3.1 µm and a geometric standard deviation of 1.6 and 2.25, respectively, were used to model the secondary sulfate and dust aerosol transport. Potential source contribution function (PSCF) analysis and generalized Tikhonov regularization were applied so as to acquire potential source areas and quantify their emission fluxes. A significant source area for secondary sulfate on the east of the Caspian Sea is indicated, when data from all stations are used. The maximum emission flux in that area is as high as 10 × 10−12 kg m−2 s−1. When Vilnius, Dushanbe, and Kurchatov data were excluded, the areas with the highest emission fluxes were the western and central Balkans and southern Poland. The results display many similarities to the SO2 emission maps provided by the OMI-HTAP (Ozone Monitoring Instrument-Hemispheric Transport Air Pollution) and ECLIPSE (Evaluating the Climate and Air Quality Impacts of Short-Lived Pollutants) databases. For dust aerosol, measurements from Athens, Belgrade, Debrecen, Lisbon, Tirana, and Zagreb are utilized. The west Sahara region is indicated as the most important source area, and its contribution is quantified, with a maximum of 17.6 × 10−12 kg m−2 s−1. When we apply the emission fluxes from every geographic grid cell (1∘ × 1∘) for secondary sulfate aerosol deducted with the new method to air masses originating from Vilnius, a useful approximation to the measured values is achieved.</p

Comparison and complementary use of in situ and remote sensing aerosol measurements in the Athens Metropolitan Area

© 2020 Elsevier Ltd. All rights reserved. This manuscript is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International Licence http://creativecommons.org/licenses/by-nc-nd/4.0/.In the summer of 2014 in situ and remote sensing instruments were deployed in Athens, in order to study the concentration, physical properties, and chemical composition of aerosols. In this manuscript we aim to combine the measurements of collocated in situ and remote sensing instruments by comparison and complementary use, in order to increase the accuracy of predictions concerning climate change and human health. We also develop a new method in order to select days when a direct comparison on in situ and remote sensing instruments is possible. On selected days that displayed significant turbulence up to approximately 1000 m above ground level (agl), we acquired the aerosol extinction or scattering coefficient by in situ instruments using three approaches. In the first approach the aerosol extinction coefficient was acquired by adding a Nephelometer scattering coefficient in ambient conditions and an Aethalometer absorption coefficient. The correlation between the in situ and remote sensing instruments was good (coefficient of determination R2 equal to 0.69). In the second approach we acquired the aerosol refractive index by fitting dry Nephelometer and Aethalometer measurements with Mie algorithm calculations of the scattering and absorption coefficients for the size distribution up to a maximum diameter of 1000 nm obtained by in situ instruments. The correlation in this case was relatively good (R2 equal to 0.56). Our next step was to compare the extinction coefficient acquired by remote sensing instruments to the scattering coefficient calculated by Mie algorithm using the size distribution up to a maximum diameter of 1000 nm and the equivalent refractive index (ERICOR), which is acquired by the comparison of the size distributions obtained by a Scanning Mobility Particle Sizer (SMPS) and an Optical Particle Counter (OPC). The agreement between the in situ and remote sensing instruments in this case was not satisfactory (R2 equal to 0.35). The last comparison for the selected days was between the aerosol extinction Ångström exponent acquired by in situ and remote sensing instruments. The correlation was not satisfactory (R2 equal to 0.4), probably due to differences in the number size distributions present in the air volumes measured by in situ and remote sensing instruments. We also present a day that a Saharan dust event occurred in Athens in order to demonstrate the information we obtain through the synergy of in situ and remote sensing instruments on how regional aerosol is added to local aerosol, especially during pollution events due to long range transport.Peer reviewe

Evaluation of receptor and chemical transport models for PM10 source apportionment

In this study, the performance of two types of source apportionment models was evaluated by assessing the results provided by 40 different groups in the framework of an intercomparison organised by FAIRMODE WG3 (Forum for air quality modelling in Europe, Working Group 3). The evaluation was based on two performance indicators: z-scores and the root mean square error weighted by the reference uncertainty (RMSEu), with pre-established acceptability criteria. By involving models based on completely different and independent input data, such as receptor models (RMs) and chemical transport models (CTMs), the intercomparison provided a unique opportunity for their cross-validation. In addition, comparing the CTM chemical profiles with those measured directly at the source contributed to corroborate the consistency of the tested model results. The most commonly used RM was the US EPA- PMF version 5. RMs showed very good performance for the overall dataset (91% of z-scores accepted) while more difficulties were observed with the source contribution time series (72% of RMSEu accepted). Industrial activities proved to be the most difficult sources to be quantified by RMs, with high variability in the estimated contributions. In the CTMs, the sum of computed source contributions was lower than the measured gravimetric PM10 mass concentrations. The performance tests pointed out the differences between the two CTM approaches used for source apportionment in this study: brute force (or emission reduction impact) and tagged species methods. The sources meeting the z-score and RMSEu acceptability criteria tests were 50% and 86%, respectively. The CTM source contributions to PM10 were in the majority of cases lower than the RM averages for the corresponding source. The CTMs and RMs source contributions for the overall dataset were more comparable (83% of the z-scores accepted) than their time series (successful RMSEu in the range 25% - 34%). The comparability between CTMs and RMs varied depending on the source: traffic/exhaust and industry were the source categories with the best results in the RMSEu tests while the most critical ones were soil dust and road dust. The differences between RMs and CTMs source reconstructions confirmed the importance of cross validating the results of these two families of models

AIRUSE-LIFE+:A harmonized PM speciation and source apportionment in five southern European cities

The AIRUSE-LIFE+ project aims at characterizing similarities and heterogeneities in particulate matter (PM) sources and contributions in urban areas from southern Europe. Once the main PMx sources are identified, AIRUSE aims at developing and testing the efficiency of specific and non-specific measures to improve urban air quality. This article reports the results of the source apportionment of PM₁₀ and PM_2.5 conducted at three urban background sites (Barcelona, Florence and Milan, BCN-UB, FI-UB and MLN-UB), one suburban background site (Athens, ATH-SUB) and one traffic site (Porto, POR-TR). After collecting 1047 PM₁₀ and 1116 PM_2.5 24 h samples during 12 months (from January 2013 on) simultaneously at the five cities, these were analysed for the contents of OC, EC, anions, cations, major and trace elements and levoglucosan. The USEPA PMF5 receptor model was applied to these data sets in a harmonized way for each city. <br><br> The sum of vehicle exhaust (VEX) and non-exhaust (NEX) contributes between 3.9 and 10.8 µg m⁻³ (16–32 %) to PM₁₀ and 2.3 and 9.4 µg m⁻³ (15–36 %) to PM_2.5, although a fraction of secondary nitrate is also traffic-related but could not be estimated. Important contributions arise from secondary particles (nitrate, sulfate and organics) in PM_2.5 (37–82 %) but also in PM₁₀ (40–71 %), mostly at background sites, revealing the importance of abating gaseous precursors in designing air quality plans. <br><br> Biomass burning (BB) contributions vary widely, from 14–24 % of PM₁₀ in POR-TR, MLN-UB and FI-UB, 7 % in ATH-SUB, to  &lt;  2 % in BCN-UB. In PM_2.5, BB is the second most important source in MLN-UB (21 %) and in POR-TR (18 %), the third one in FI-UB (21 %) and ATH-SUB (11 %), but is again negligible (&lt; 2 %) in BCN-UB. This large variability among cities is mostly due to the degree of penetration of biomass for residential heating. In Barcelona natural gas is very well supplied across the city and is used as fuel in 96 % of homes, while in other cities, PM levels increase on an annual basis by 1–9 µg m⁻³ due to biomass burning influence. Other significant sources are the following. <br><br> &ndash; Local dust, 7–12 % of PM₁₀ at SUB and UB sites and 19 % at the TR site, revealing a contribution from road dust resuspension. In PM_2.5 percentages decrease to 2–7 % at SUB-UB sites and 15 % at the TR site. <br><br> &ndash; Industry, mainly metallurgy, contributing 4–11 % of PM₁₀ (5–12 % in PM_2.5), but only at BCN-UB, POR-TR and MLN-UB. No clear impact of industrial emissions was found in FI-UB and ATH-SUB. <br><br> &ndash; Natural contributions from sea salt (13 % of PM₁₀ in POR-TR, but only 2–7 % in the other cities) and Saharan dust (14 % in ATH-SUB, but less than 4 % in the other cities). <br><br> During high pollution days, the largest sources (i.e. excluding secondary aerosol factors) of PM₁₀ and PM_2.5 are VEX + NEX in BCN-UB (27–22 %) and POR-TR (31–33 %), BB in FI-UB (30–33 %) and MLN-UB (35–26 %) and Saharan dust in ATH-SUB (52–45 %). During those days, there are also quite important industrial contributions in BCN-UB (17–18 %) and local dust in POR-TR (28–20 %)

Results of the first European Source Apportionment intercomparison for Receptor and Chemical Transport Models

In this study, the performance of the source apportionment model applications were evaluated by comparing the model results provided by 44 participants adopting a methodology based on performance indicators: z-scores and RMSEu, with pre-established acceptability criteria. Involving models based on completely different and independent input data, such as receptor models (RMs) and chemical transport models (CTMs), provided a unique opportunity to cross-validate them. In addition, comparing the modelled source chemical profiles, with those measured directly at the source contributed to corroborate the chemical profile of the tested model results. The most used RM was EPA- PMF5. RMs showed very good performance for the overall dataset (91% of z-scores accepted) and more difficulties are observed with SCE time series (72% of RMSEu accepted). Industry resulted the most problematic source for RMs due to the high variability among participants. Also the results obtained with CTMs were quite comparable to their ensemble reference using all models for the overall average (>92% of successful z-scores) while the comparability of the time series is more problematic (between 58% and 77% of the candidates’ RMSEu are accepted). In the CTM models a gap was observed between the sum of source contributions and the gravimetric PM10 mass likely due to PM underestimation in the base case. Interestingly, when only the tagged species CTM results were used in the reference, the differences between the two CTM approaches (brute force and tagged species) were evident. In this case the percentage of candidates passing the z-score and RMSEu tests were only 50% and 86%, respectively. CTMs showed good comparability with RMs for the overall dataset (83% of the z-scores accepted), more differences were observed when dealing with the time series of the single source categories. In this case the share of successful RMSEu was in the range 25% - 34%.JRC.C.5-Air and Climat

Orthotopic bladder substitution after radical cystectomy: 5 years of experience with a novel personal modification of the ileal S pouch

Purpose: We report a 5-year experience with 52 patients who underwent radical cystoprostatectomy for bladder cancer and orthotopic bladder substitution using a novel personal modification of the S pouch. Materials and Methods: From September 1995 to December 1999, 52 men 36 to 72 years old (mean age 63) underwent bladder substitution with an S pouch. They were followed until September 2000. The pouch was constructed with a 36 cm. segment of ileum with the whole length used for the reservoir. The ureters were directly anastomosed with one above the other in the mid segment of the pouch without any antireflux procedure. Complications were documented and classified as early or up Do 3 months postoperatively and late, and further subdivided by the relationship to neobladder construction. Continence and voiding pattern were evaluated by personal interview and neobladder function was urodynamically assessed. Mean followup in our patients was 30 months. Results: The most, common of the 5 early and 9 late neobladder related complications were persistent urine leakage and reflux, respectively. There was no reflux greater than grade III in the 4 patients with reflux (5 refluxing ureters) and no functional disorders. We observed 12 early and 5 late complications unrelated to the neobladder. Open reoperation was required in 5 cases. Good or satisfactory daytime and nighttime continence was reported by 95% and 88% of our patients, respectively. By year 1 postoperatively 91% of our patients voided at an interval of 3 to 5 hours during the day. Mean maximum neobladder capacity was 672 mi. and mean post-void residual was 30 mi. by year 3 postoperatively. Two patients required self-catheterization once daily and mild hyperchloremia without acidosis developed in 2. Conclusions: The advantages of our modified S pouch are technical simplicity, substantially shorter operative time and decreased bowel length required. It is associated with an acceptable complication rate and functional parameters with subsequent patient satisfaction and good quality of life