Review of PM Oxidative Potential Measured with Acellular Assays in Urban and Rural Sites across Italy

Abstract

This work is an overview of the oxidative potential (OP) values up to date measured in Italy, with the aim to provide a picture of the spatial and seasonal variability of OP in the various geographical areas across Italy. The summarized works used the common acellular assays-based dithiothreitol (OP DTT ), ascorbic acid (OP AA ), glutathione (OP GSH ), and 2 ,7 -dichlorodfluorescein (OP DCFH ) assays. The paper describes the association of OP responses with PM chemical composition, the sensitivity of various acellular OP assays to PM components and emission sources, and PM size distribution of the measured OP values. Our synthesis indicates that crustal and transition metals (e.g., Fe, Ni, Cu, Cr, Mn, Zn, and V), secondary ions and carbonaceous components (elemental carbon, EC, organic carbon, OC and water soluble carbon, WSOC) show significant correlations with OP across different urban and rural areas and size ranges. These chemical species are mainly associated with various PM sources, including residual/fuel oil combustion, traffic emissions, and secondary organic aerosol formation. Although the OP assays are sensitive to the same redox-active species, they differ in the association with PM chemical components. The DDT assay is mainly sensitive to the organic compounds that are mostly accumulated in the fine PM fraction, i.e., tracers of burning sources, and redox active organics associated with other markers of photochemical aging. In contrast, OP AA and OP GSH were mostly responsive to metals, mainly those related to non-exhaust traffic emissions (Cu, Zn, Cr, Fe, Ni, Mn, Sn, Cd, Pb), that are mainly accumulated in the coarse PM. Among the investigated sites, our synthesis shows larger OP values in Trentino region and the Po Valley, that may be explained by the high density of anthropogenic sources, and the orographic and meteorological characteristics, that favor the pollutants accumulation and aerosol photo-oxidative aging. ). The acellular version of the 2 ,7 -dichlorodfluorescein (DCFH) assay uses the enzymatic production of the fluorescent probe largely used for the evaluation of oxidative stress in living cells.The present work summarizes the PM oxidative properties up to date measured in Italy using OP acellular assays, with the aim of giving a general insight of PM OP across the Italian territory, that has not been reported yet, in spite of the increasing number of OP measurements carried out in Europe [6,[19][20][21][22]. In addition, the study reviews the association described in previous studies between OP from different assays with several inorganic ad organic components, that effect PM oxidative properties, i.e., metals, ions, and carbonaceous components. The aim is to give a picture of the spatial and seasonal variability of different contributions to OP in the various geographical areas across Italy. The relevance of such an investigation is based on the large variability in the chemical composition of different PM size fractions in various locations across Italy, as a consequence of the stron...

Effect of filter extraction solvents on the measurement of the oxidative potential of airborne PM2.5

“…On the contrary, the measured OP AA responses, both volume-and mass-related values, do not show any significant difference between the two sites (Tables S1-S3). This is consistent with several literature papers reporting that the AA assay reactivity is less dependent on PM mass concentration as well as on chemical composition than the DTT response (Bates et al 2019;Calas et al 2018;Fang et al 2016;Hedayat et al 2014;Janssen et al 2015;Perrone et al 2019;Pietrogrande et al 2019a;Visentin et al 2016).…”

“…Aqueous solution extraction Water-based extractions were performed for 15 min in an ultrasonic bath using 10 mL of phosphate buffer or Gamble's solution, following the procedure previously used by Authors that has been found to guarantee a good extraction efficiency ≥ 90% (Pietrogrande et al 2019a;Visentin et al 2016). The extracts were then filtered on a regenerate cellulose syringe filter (13 mm, 0.22 μm, Kinesis) to remove the suspended solid particles.…”

“…The study was performed on 32 real environmental PM 2.5 samples from urban and rural sites in the Po Valley (Northern Italy) in spring 2018, as well as on individual standard compounds, chosen for either their known reactivity to the DTT and AA assays or their abundance in atmospheric aerosol, i.e, metals and quinones (Charrier and Anastasio 2015;Fang et al 2016;Fujitani et al 2017;Pietrogrande et al 2019a;Verma et al 2015;Tuet et al 2017).…”

The impact of stay-home policies during Coronavirus-19 pandemic on the chemical and toxicological characteristics of ambient PM2.5 in the metropolitan area of Milan, Italy

“…Earlier studies across the Po Valley have shown that PM oxidative potential is influenced by the concentrations of metals (e.g., Cr, Mn, Fe, Ni, Cu) and carbonaceous species (e.g., OC, EC) ( Hakimzadeh et al, 2020 ; Longhin et al, 2020 ; Pietrogrande et al, 2019 ; Visentin et al, 2016 ). These species are mainly associated with road traffic, domestic biomass burning, oil combustion, and SOA across Italy ( Larsen et al, 2012 ; Pietrogrande et al, 2019 ); however, it has been shown that the oxidative potential of PM in the Po Valley region, and in particular in the Milan metropolitan area, is elevated due to the high density of anthropogenic emission sources in conjunction with specific stable atmospheric conditions, favoring the accumulation and aging of particles in the atmosphere ( Perrone et al, 2016 , Perrone et al, 2010 ; Pietrogrande et al, 2019 ). Fig.…”

Application of DPPH Assay for Assessment of Particulate Matter Reducing Properties

“…The combined application of DPPH and conventional OP assays could then permit, in the future, to gain more knowledge about the reaction and/or competition between oxidative and reducing processes.health impacts than ordinarily used PM mass concentrations [9]. In this context, many acellular assays were developed to measure oxidative potential in order to gain a proxy of this PM capability [10]. There is still no agreement regarding the most representative assay to determine oxidative potential [11], but most commonly used acellular tests include the ascorbic acid (AA) [12] and dithiothreitol (DTT) [13] assays which consist of mimicking the consumption of a physiological and a surrogate antioxidant, respectively, and 2 ,7 -dichlorofluorescin (DCFH) by which particle-bound ROS are determined [14].…”