Oxidative potential apportionment of atmospheric PM₁: a new approach combining high-sensitive online analysers for chemical composition and offline OP measurement technique

Source apportionment models were widely used to successfully assign highly time-resolved aerosol data to specific emissions and/or atmospheric chemical processes. These techniques are necessary for targeting the sources affecting air quality and for designing effective mitigation strategies. Moreover, evaluation of the toxicity of airborne particulate matter is important since the classically measured particulate matter (PM) concentrations appear insufficient for characterizing the impact on human health. Oxidative potential (OP) measurement has recently been developed to quantify the capability of PM to induce an oxidative imbalance in the lungs. As a result, this measurement unit could be a better proxy than PM mass concentration to represent PM toxicity. In the present study, two source apportionment analyses were performed using positive matrix factorization (PMF) from organic aerosol (OA) mass spectra measured at a 15 min time resolution using a time-of-flight aerosol chemical speciation monitor (ToF-ACSM) and from 19 trace elements measured on an hourly basis using an online metal analyser (Xact 625i). The field measurements were carried out in summer 2018. While it is common to perform PMF studies individually on ACSMs and more recently on Xact datasets, here we used a two-step methodology leading to a complete PM1 source apportionment. The outputs from both OA PMF and Xact PMF, the inorganic species concentrations from the ACSM, and the black carbon (BC) fractions (fossil fuel and wood burning) measured using an Aethalometer (AE33) were gathered into a single dataset and subjected to a combined PMF analysis. Overall, eight factors were identified, each of them corresponding to a more precise source than performing single PMF analyses. The results show that besides the high contribution of secondary ammonium sulfate (28 %) and organic nitrate (19 %), about 50 % of PM1 originated from distinct combustion sources, including emissions from traffic, shipping, industrial activities, cooking, and biomass burning. Simultaneously, PM1 filters were collected during the experimental period on a 4 h sampling basis. On these filters, two acellular OP assays were performed (dithiothreitol; OPDTT and ascorbic acid; OPAA) and an inversion method was applied on factors issued from all PMFs to assess the contribution of the PM sources to the OP. This work highlights the sensitivity of OPAA to industrial and dust resuspension sources and those of OPDTT to secondary ammonium sulfate, shipping, and biomass burning.</p

Computational geometry analysis of dendritic spines by structured illumination microscopy

We are currently short of methods that can extract objective parameters of dendritic spines useful for their categorization. Authors present in this study an automatic analytical pipeline for spine geometry using 3D-structured illumination microscopy, which can effectively extract many geometrical parameters of dendritic spines without bias and automatically categorize spine population based on their morphological feature

Phenomenology of ultrafine particle concentrations and size distribution across urban Europe

The 2017-2019 hourly particle number size distributions (PNSD) from 26 sites in Europe and 1 in the US were evaluated focusing on 16 urban background (UB) and 6 traffic (TR) sites in the framework of Research Infrastructures services reinforcing air quality monitoring capacities in European URBAN & industrial areaS (RI-URBANS) project. The main objective was to describe the phenomenology of urban ultrafine particles (UFP) in Europe with a significant air quality focus. The varying lower size detection limits made it difficult to compare PN concentrations (PNC), particularly PN10-25, from different cities. PNCs follow a TR > UB > Suburban (SUB) order. PNC and Black Carbon (BC) progressively increase from Northern Europe to Southern Europe and from Western to Eastern Europe. At the UB sites, typical traffic rush hour PNC peaks are evident, many also showing midday-morning PNC peaks anti-correlated with BC. These peaks result from increased PN10-25, suggesting significant PNC contributions from nucleation, fumigation and shipping. Site types to be identified by daily and seasonal PNC and BC patterns are: (i) PNC mainly driven by traffic emissions, with marked correlations with BC on different time scales; (ii) marked midday/morning PNC peaks and a seasonal anti-correlation with PNC/BC; (iii) both traffic peaks and midday peaks without marked seasonal patterns. Groups (ii) and (iii) included cities with high insolation. PNC, especially PN25-800, was positively correlated with BC, NO2, CO and PM for several sites. The variable correlation of PNSD with different urban pollutants demonstrates that these do not reflect the variability of UFP in urban environments. Specific monitoring of PNSD is needed if nanoparticles and their associated health impacts are to be assessed. Implementation of the CEN-ACTRIS recommendations for PNSD measurements would provide comparable measurements, and measurements of <10 nm PNC are needed for full evaluation of the health effects of this size fraction

Viscoelastic properties of a plasticised PVC reinforced with cellulose whiskers

International audienc

Metallic Trace Elements Shipping Profile by PM1 Source Apportionment in a Mediterranean PortCity

International audienceShipping emissions in ports can have substantial impacts on air quality and population health in the nearby urbanenvironment. Legislative efforts made in recent years have reduced emissions of some gaseous pollutants but theaerosol chemical composition, in particular metals composition in submicronic fraction, is little documented.More than 30 trace metals have been monitored with two online metals analysers (Xact 625i) in addition to regulatedpollutants (PM2.5, PM10, NOX, O3 and SO2) and ultrafine particle number during two intensive campaigns in Marseille(France) in the summer 2021. Samples were taken simultaneously along the port berths and on the urban backgroundaerosol site MRS-LCP located 2 km from the port. As the second largest city of France, Marseille represents achallenging environment for source apportionment (SA), as it combines multiple anthropogenic sources includingintensive traffic and various industrial activities in addition to shipping.This work presents the SA analysis performed on trace elements using Positive Matrix Factorization (PMF) resolvedwith the multilinear engine approach (SoFi Pro) on both sampling sites.Inside the port area, the half hourly metals measurements allowed to define a “shipping” profile by SA analysis. Thisprofile is dominated by Vanadium (V) and Nickel (Ni) and is associated with ultrafine particles (Dmob<70 nm). On a dailyscale, the profile correlates with ship arrivals and departures.On the background urban site, PMF results from the summer 2019 showed that a shipping factor enriched in V and Nicould be retrieved. The use of the shipping profile determined inside the port area to constrain PMF run allowed tobetter assess the contribution of this source on air quality. In addition, sources profile comparison between summer2019 and 2021 highlights the evolution of shipping emissions following the 0.5% fuels sulfur limit implemented in2020