Monitoring and evaluation of Terni (Central Italy) air quality through spatially resolved analyses

A study of spatial variability of PM10 elemental components was conducted in Terni city (Central Italy), situated in an intramountain depression characterized by the presence of several particulate matter emission sources. The meteorological conditions of Terni basin limit the dispersion and enhance the accumulation of the atmospheric pollutants. Thanks to the utilization of new samplers (Smart Sampler), used for the first time and working in parallel at 23 sampling sites, spatially resolved data were obtained. Localizations of the samplers were chosen in order to evaluate the impact of different local PM10 sources. Chemical composition of the samples was determined in combination with a chemical fractioning procedure, that allowed us to discriminate watersoluble and residual fractions of analyzed elements in which proved to be a valuable approach for increasing selectivity of elements as source tracers. Spatial variability of elements underlined the contribution of local emission sources and the different dispersion capacity of each element. Terni city resulted to be an ideal area to test and validate a new experimental method for the acquisition of spatially resolved data providing the possibility to properly evaluate the spatial variability of PM10 and its chemical components

Evaluation of the Efficiency of Arundo donax L. Leaves as Biomonitors for Atmospheric Element Concentrations in an Urban and Industrial Area of Central Italy

Washed and unwashed Arundo donax L. (A. donax) leaves were analyzed for elements, and results were compared with element concentrations detected in river water and particulate matter (PM) Samples were collected along a river in an urban and industrial hot spot of Central Italy, where element concentrations show relevant spatial gradients both in air and river water. The aim of this study is to identify the role of the two environmental matrices on leaves composition. Element concentrations of washed and unwashed leaves were compared to differentiate between the superficial deposition and the uptake into leaf tissues of elements. Water-soluble and -insoluble element concentrations were measured in PM10 samples collected on membrane filters by using innovative high spatial resolution samplers. The comparison among leaf and atmospheric concentrations of PM10 elements showed a similar trend for Ni, Mo, Cr, Ti, and Fe, which are reliable tracers of the PM10 contribution by steel plant and vehicular traffic. Soluble species appeared to be mainly bounded into leaf tissues, while insoluble species were deposited on their surface. On the other hand, element concentrations detected in washed A. donax leaves were poorly correlated with those measured in river water samples. The obtained results proved that A. donax leaves can be used as reliable biomonitors for the evaluation of the atmospheric concentrations of some PM10 elemental components

Monitoring and Evaluation of Terni (Central Italy) Air Quality through Spatially Resolved Analyses

A study of spatial variability of PM10 elemental components was conducted in Terni city (Central Italy), situated in an intramountain depression characterized by the presence of several particulate matter emission sources. The meteorological conditions of the Terni basin limit the dispersion and enhance the accumulation of atmospheric pollutants. Thanks to the utilization of new smart samplers, used for the first time and working in parallel at 23 sampling sites, spatially resolved data were obtained. Localizations of the samplers were chosen in order to evaluate the impact of different local PM10 sources. Chemical composition of the samples was determined in combination with a chemical fractioning procedure that allowed us to discriminate water-soluble and residual fractions of analyzed elements in which proved to be a valuable approach for increasing selectivity of elements as source tracers. Spatial variability of elements underlined the contribution of local emission sources and the different dispersion capacity of each element. The city of Terni resulted to be an ideal area to test and validate a new experimental method for the acquisition of spatially resolved data providing the possibility to properly evaluate the spatial variability of PM10 and its chemical components

Seasonal variations in the chemical composition of indoor and outdoor PM10 in university classrooms

In the VIEPI project (Integrated evaluation of the exposure to indoor particulate matter) framework, we carried out a 1-year study of the concentration and chemical composition of particulate matter (PM) in a 5 story building in the Sapienza University of Rome (Italy). Each sampling had a duration of 1 month and was carried out indoors and outdoors in six classrooms. The chemical analyses were grouped to obtain information about the main PM sources. Micro-elements in their soluble and insoluble fractions were used to trace additional sources. Indoor PM composition was dominated by soil components and, to a lesser extent, by the organics, which substantially increased when people crowded the sites. The penetration of PM components was regulated by their chemical nature and by the dimensions of the particles in which they were contained. For the first time in crowded indoor environments, three different chemical assays aimed to determine PM redox properties complemented chemical composition measurements. These preliminary tests showed that substantially different redox properties characterised atmospheric particles in indoor and outdoor sites. The innovative characteristics of this study (time duration, number of considered environments) were essential to obtain relevant information about PM composition and sources in indoor academic environments and the occupants’ role

Spatial mapping of PM10 element concentrations in Terni (Central Italy) by using spatially-resolved chemical data

Particulate matter (PM) air pollution represents a major environmental and health issue which largely depends on the type and amount of local emissions in industrial and urban areas. Therefore, the evaluation of the spatial distribution of PM chemical components is fundamental for a reliable identification of emission sources and the assessment of personal exposure. Generally, due to the very high cost of a network based on traditional PM samplers, the dispersion of air pollutants is estimated through mathematical models, which may not be able to properly describe the complexity of PM transport and transformation processes. In the last few years, a new very-low volume and automatic device for PM sampling on membrane filters has been developed and from 12/2016 to 02/2018 it has been employed in a dense (23 sampling sites, about 1 km between the sites) and low-cost monitoring network across Terni, an urban and industrial hot-spot of Central Italy [1,2]. PM10 samples were monthly collected and analyzed for PM mass and water-soluble and insoluble element concentrations by ICP-MS. Principal component analysis was performed on the spatially-resolved chemical data to individuate reliable tracers of the main local PM emission sources: Cu, Sb, Sn, Zr, Bi (insoluble fraction) and Ba (water-soluble fraction) were found to be good tracers of rail network and vehicular traffic; K, Tl, Rb, Cs and Cd (water-soluble fraction) were identified as reliable tracers of biomass burning; Co, Ni, Cr, Nb, Mn, Pb (insoluble fraction) and As, W, Mo, Cr, Zn, Li, Mn, Ga (water-soluble fraction) showed the steel plant role in the emission of PM10. Spatial distribution of the elements was mapped by using ordinary kriging interpolation method [Figure 1]. The new experimental approach was found to be effective for the evaluation of the impact of PM10 emission sources and promises to be powerful for the improvement of PM dispersion models

Spatial Mapping of the Winter and Summer PM10 Element Concentrations in an Urban and Industrial Hot-spot of Central Italy

Particulate matter (PM) air pollution is a serious threat to human health; various epidemiological studies have spotlighted strong correlations between exposure to PM and the onset of cardiovascular and respiratory diseases. Since in urban and industrial areas, PM air pollution largely depends on the type, number and rate of local emissions; the study of the spatial distribution of PM chemical compounds is essential for a reliable identification of emission sources and the assessment of personal exposure. However, due to the very high cost of a network based on traditional PM samplers, ambient air quality assessment and epidemiological studies are usually based on measurements taken at a few sampling points. For these reasons, in the last few years, a self-powered and very-low volume device for PM sampling on membrane filters has been developed with the purpose of allowing spatially-resolved determination of PM chemical compounds. The sampler has been employed from 12/2016 to 02/2018 in a dense (23 sampling sites, about 1 km between the sites) and low-cost monitoring network across Terni, an urban and industrial hot-spot of Central Italy (Massimi et al., 2017, 2019). PM10 samples were monthly collected and chemically characterized for the water-soluble and insoluble fraction of 35 elements (Al, As, B, Ba, Bi, Ca, Cd, Ce, Co, Cr, Cs, Cu, Fe, Ga, K, La, Li, Mg, Mn, Mo, Na, Nb, Ni, Pb, Rb, Sb, Sn, Sr, Ti, Tl, U, V, W, Zn, Zr) by using a chemical fractioning procedure (Canepari et al., 2006a, 2006b). Principal component analysis was performed on the spatially-resolved chemical data to individuate reliable tracers of the main local PM emission sources. Cu, Sb, Sn, Zr, Bi (insoluble fraction) and Ba (water-soluble fraction) were found to be good tracers of rail network and vehicular traffic; K, Tl, Rb, Cs and Cd (water-soluble fraction) were identified as reliable tracers of biomass burning; Co, Ni, Cr, Nb, Mn, Pb (insoluble fraction) and As, W, Mo, Cr, Zn, Li, Mn, Ga (water-soluble fraction) showed the steel plant role in the emission of PM10. Spatial distribution of the elements was mapped by using ordinary kriging interpolation method. The new experimental approach was found to be effective for the evaluation of the impact of PM10 emission sources and promises to be powerful for the optimization and validation of dispersion models through high spatial resolution chemical data and for a more accurate assessment of the population exposure to PM air pollutants

Spatial mapping and dimensional distribution of PM oxidative potential in Terni (Central Italy)

Over the last few decades, numerous studies have showed how the exposure to ambient particulate matter (PM) is associated to negative effects on human health (Pope et al, 2004). Moreover, the evaluation of PM exposure and toxic responses has been focused on the study of mass concentration, chemical composition and dimensional distribution of the particles (Kelly et al, 2012). However, the mechanisms behind the health effects are still not fully understood because of the complexity of PM composition. During the last years, the study of the oxidative potential (OP) has been proposed as a relevant metric related to biological responses to PM exposure (Simonetti et al, 2018a). Oxidative potential (OP) is defined as a measure of the capacity of PM to oxidise target molecules, by generating ROS in environments without living cells. Several acellular assays for testing OP have been developed, such as acid ascorbic (AA), 2,7-dichlorofluorescenin (DCFH) and dithiothreitol (DTT) assay, but anyone has been identified as the most appropriate for interpreting PM oxidative potential results. Therefore, the best solution turned out to be an inter-comparison between the different acellular tests. In fact, the three OP assays have been deemed sensible toward different PM-selected components, coming from various typical urban and industrial emission sources and characterized by very different chemical compositions, which can be associated to different adverse health effects (Simonetti et al, 2018b). In this study we applied the three OP assays (OPAA, OPDTT and OPDCFH) to PM10 samples, previously chemically analysed (Massimi et al, 2017), collected at 23 different sampling sites in Terni (an urban and industrial hot-spot of Central Italy), by using innovative and very-low volume devices for PM sampling on membrane filters (HSRS - High Spatial Resolution Sampler; Fai Instruments, Fonte Nuova, Rome, Italy). The HSRS worked in parallel during a two-month winter monitoring period. The sampling sites have been chosen for spatially representing the main anthropic PM emission sources (i.e. vehicular traffic, rail network, power plant, steel plant, domestic and industrial biomass heating) and the samplers were located in order to cover the study area with around 1 km spatial resolution (Figure 1, upper panel; Massimi et al, 2019). In this study we aimed to assess the spatial variation of the three acellular assays in order to investigate the relationships between the different OP results and the contribution of the local emission sources to the total PM10. To our knowledge, the comparison of the three OP assays applied to PM10 spatially-resolved samples has never been undertaken so far. Furthermore, we applied the three OP assays to size-segregated PM samples collected by a multistage impactor (cut-sizes: 0.18, 0.32, 0.56, 1.0, 1.8, 3.2, 5.6, 10 and 18 μm) at three sampling sites (MA, CA and PR; Figure 1, upper panel), characterized by different strength of the main PM sources, in order to evaluate the different sensitivity of the three acellular assays toward fine and coarse particles. The spatial mapping of the OP values, obtained by using the ordinary kriging interpolation (spherical semivariogram model; ArcGis, ArcMap 10.3.1) are reported in Figure 1. The results showed how OPAA was particularly sensitive toward PM10 coming from the rail network, released by resuspension of particles formed through the abrasion of train brakes. On the contrary, OPDTT, OPDCFH were found to be more related to PM10 coming from industrial sources (steel plant at PR and carpentry at FA) and biomass burning (domestic biomass heating at BR). Finally, size distribution analyses of OP confirmed that OPAA was more sensitive toward coarse particles, mainly released by brake abrasion, while OPDTT and OPDCFH were found to be more sensitive toward fine particles, mainly released by combustion processes such as biomass burning and industrial processes. These results confirmed the different sensitivity of the three OP assays toward PM10 released by the local emission sources

Evaluation of antioxidant properties of particulate matter by DPPH assay

Several acellular methods, defined as oxidative potential (OP) assays, have been developed to assess the particulate matter (PM) oxidative capacity and they are considered as predictors of the ability of dust to generate oxidative stress in living organisms. There is no agreement regarding the most representative assay to measure the OP of PM (Ayres et al., 2008), but methods mostly used on the PM filter extracts are the dithiothreitol (DTT; Cho et al., 2005), the 2′,7′-dichlorofluorescin (DCFH; Hung et al., 2001) and the ascorbic acid (AA; Stoeger et al., 2008) assays. The application of those assays to PM samples collected in field suggests the possible presence of reducing species, naturally present in PM, that compete with oxidizing species, altering OP values. This issue merits to be further investigated. While the use of acellular methods for the assessment of the OP values has been receiving great scientific attention in recent years, there is still a literature gap about acellular assays for identifying reducing species in particulate matter. One of the antioxidant capacity assays, that is currently in use for various matrices, is based on the use of the stable free radical DPPH (2,2-Diphenyl-1-picrylhydrazyl). In this work, this assay was tailored and applied to PM. Both PM2.5/PM10 field samples and dusts produced by specific sources (i.e. brake dust, Saharan dust, road dust, soil dust, coke and certified material NIST1648a) were considered in the work. The effect of the antioxidants on DPPH· radical is estimated according to the procedure described by Chen et al. (2016) with slight modifications. The collected dust and the PM filters are put into 5 ml of DPPH 0.1 mM in ethanol (96%) prepared daily and, then, they are extracted at room temperature for 30 minutes, by shaking the solutions inside glass vials. Then, spectrophotometric measurements are done at 517 nm. The same samples were analysed also for elements, inorganic ions and oxidative potential (AA, DTT and DCFH assays). The comparison between obtained data by OP assays and DPPH assay performed in parallel, allowed us to gain more knowledge on redox properties of PM. The values are interpreted and linked to the chemical composition of the samples. The study of the redox properties of PM may help to deepen the relationship between the composition of PM and its toxicity

Applicazione degli Smart Samplers al monitoraggio ad alta risoluzione spaziale del PM10 nella conca ternana (Italia Centrale)

La città di Terni (Italia Centrale), situata in una depressione intramontana, presenta numerose sorgenti emissive di inquinamento atmosferico come il polo siderurgico (Terni AST), l’impianto di trattamento dei rifiuti (Terni EN.A), il traffico veicolare ed il riscaldamento domestico. La peculiare conformazione geomorfologica della conca ternana limita fortemente la dispersione degli inquinanti emessi, favorendone l’accumulo. Tali fattori rendono questo territorio particolarmente adatto a studi innovativi di mappatura spaziale del particolato atmosferico. Il presente lavoro riguarda lo studio della distribuzione spaziale del PM10 e delle sue componenti elementari nella conca ternana, mediante misure ad elevata risoluzione spaziale. Grazie all’utilizzo di campionatori Smart Sampler, leggeri, low-cost, automatici ed autoalimentati, è stata realizzata nella città di Terni una rete di monitoraggio estesa ed esaustiva, costituita da 25 siti di campionamento da cui sono stati ottenuti dati sperimentali ad elevata risoluzione spaziale (distanza tra i campionatori di circa 1 km) e risoluzione temporale mensile. L’installazione dei campionatori in punti strategici del territorio ha permesso di valutare i contributi al PM10 delle diverse sorgenti emissive locali. Attraverso l’analisi multivariata dei dati ottenuti sono stati individuati gli elementi traccianti di sorgente. L’installazione di campionatori lungo il profilo verticale di un grattacielo del centro urbano di Terni ha inoltre consentito di valutare il gradiente di dispersione altitudinale del PM10 e delle sue componenti elementari. Inoltre, su diversi siti di campionamento è stata valutata l’esposizione degli abitanti al particolato atmosferico in ambienti indoor (come scuole ed abitazioni private) attraverso l’individuazione dei coefficienti di penetrazione delle componenti elementari del PM10. La composizione chimica del PM10 (macro-elementi, micro-elementi, ioni inorganici) è stata determinata attraverso l’applicazione di una procedura analitica che ha permesso di separare la frazione solubile dalla frazione residua di ogni elemento analizzato. Il frazionamento chimico ha consentito di caratterizzare ulteriormente il PM10, di aumentare la selettività di ogni elemento come tracciante di sorgente e di ottenere informazioni sulla mobilità e bioaccessibilità degli elementi. I risultati ottenuti hanno dimostrato una grande variabilità spaziale delle concentrazioni elementari. In particolare le concentrazioni di Ni, Cr, Mn (frazione residua) e Mo (frazione solubile) sono risultate fortemente dipendenti dalla distanza dal polo siderurgico. Sb, Cu e Fe (frazione residua) sono risultati invece correlati al contributo del traffico veicolare e ferroviario. Il Rb si è confermato essere un buon tracciante della combustione di biomasse. Le concentrazioni indoor sono risultate correlate a quelle outdoor con coefficienti di penetrazione fortemente influenzati dalle condizioni climatiche