Polycyclic aromatic hydrocarbons and their oxygenated derivatives in urban aerosol: levels, chemical profiles, and contribution to PM2.5 oxidative potential

The concentrations of polycyclic aromatic hydrocarbons (PAHs) and quinones, a subgroup of oxygenated PAHs (oxy-PAHs), were measured in PM_2.5 samples collected during warm (May-June 2019) and cold (February-March 2020) seasons in the city of Bologna, Italy. Total PAHs concentration was nearly double in winter (6.58 ± 1.03 ng m^-3) compared with spring (3.16 ± 0.53 ng m^-3), following the trend of the PM_2.5 mass concentration. Molecular diagnostic ratios suggested that, together with traffic, biomass burning was the dominant emission source contributing to the peaks of concentration of PM_2.5 registered in the cold season. Quinone level was constant in both seasons, being 1.44 ± 0.24 ng m^-3, that may be related to the increased secondary formation during warm season, as confirmed by the higher Σoxy-PAHs/ΣPAHs ratio in spring than in winter. The oxidative potential (OP) of the PM_2.5 samples was assessed using acellular dithiothreitol (DTT) and ascorbic acid (AA) assays. The obtained responses showed a strong seasonality, with higher volume-normalized (OP_V) values in winter than in spring, i.e., OP_V^DTT: 0.32 ± 0.15 nmol min^-1 m^-3 vs. 0.08 ± 0.03 nmol min^-1 m^-3 and OP_V^AA: 0.72 ± 0.36 nmol min^-1 m^-3 vs. 0.28 ± 0.21 nmol min^-1 m^-3. Both OP_V^DTT and OP_V^AA responses were significantly associated with total PAHs, as a general descriptor of redox-active PAH derivatives, associated with co-emission from burning sources or secondary atmospheric oxidation of parent PAHs. Otherwise, only winter OP_V^DTT responses showed a significant correlation with total Ʃoxy-PAHs concentration.

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

Solvent extraction of PM_2.5 samples collected on the filter is a preliminary step for assessing the PM_2.5 oxidative potential (OP) using cell-free assays, as the dithiothreitol (DTT) and the ascorbic acid (AA) assays. In this study, we evaluated the effect of the solvent choice by extracting ambient PM_2.5 samples with different solvents: methanol, as organic solvent, and two aqueous buffers, i.e., phosphate buffer (PB) and Gamble's solution (G), as a lung fluid surrogate solution. Both the measured volume-based OP_V^DTT and OP_V^AA responses varied for the different extraction methods, since methanol extraction generated the lowest values and phosphate buffer the highest. Although all the tested solvents produced intercorrelated OP_V^DTT values, the phosphate buffer resulted the most useful for OP^DTT assessment, as it provided the most sensible measure (nearly double values) compared with other extractions. The association of the measured OP_V values with PM chemical composition suggested that oxidative properties of the investigated PM_2.5 samples depend on both transition metals and quinones, as also supported by additional experimental measurements on standard solutions of redox-active species.

Historical Changes in Seasonal Aerosol Acidity in the Po Valley (Italy) as Inferred from Fog Water and Aerosol Measurements

Acidity profoundly affects almost every aspect that shapes the composition of ambient particles and their environmental impact. Thermodynamic analysis of gas-particle composition datasets offers robust estimates of acidity, but they are not available for long periods of time. Fog composition datasets, however, are available for many decades; we develop a thermodynamic analysis to estimate the ammonia in equilibrium with fog water and to infer the pre-fog aerosol pH starting from fog chemical composition and pH. The acidity values from the new method agree with the results of thermodynamic analysis of the available gas-particle composition data. Applying the new method to historical (25 years) fog water composition at the rural station of San Pietro Capofiume (SPC) in the Po Valley (Italy) suggests that the aerosol has been mildly acidic, with its pH decreasing by 0.5-1.5 pH units over the last decades. The observed pH of the fog water also increased 1 unit over the same period. Analysis of the simulated aerosol pH reveals that the aerosol acidity trend is driven by a decrease in aerosol precursor concentrations, and changes in temperature and relative humidity. Currently, NO_x controls would be most effective for PM_2.5 reduction in the Po valley both during summer and winter. In the future, however, seasonal transitions to the NH₃-sensitive region may occur, meaning that the NH₃ reduction policy may become increasingly necessary.

Source-related components of fine particulate matter and risk of adverse birth outcomes in Northern Italy

BACKGROUND/AIM

The aim of the present study was to assess the association between PM_2.5, its sources, and preterm birth (PTB), low birth weight (LBW), and small for gestational age (SGA) in a large open residential cohort (Supersito Project in the Emilia-Romagna Region - Northern Italy).

METHODS

We collected 2012-2014 pregnancy and childbirth data from Birth Assistance Certificates and selected the pregnancies of interest. PTBs (gestational age < 37 weeks), LBW (weight < 2500 g), and SGA (newborns weighing ≤ 10th age and pregnancy week-specific percentile) were considered. Three-year measurements of daily concentrations and constituents of PM_2.5 were available at four sites and were analyzed through a source apportionment approach identifying 6 sources (traffic, biomass burning, oil combustion, anthropogenic mix, and two secondary factors). Exposure to PM_2.5 and sources was calculated at address level. Using logistic regression models, associations between exposure and outcomes were derived, applying single-pollutant and two-pollutant models, to verify the independent effect of each source.

RESULTS

The study included 23,708 neonates born to 23,415 women, among whom 1,311 PTB, 424 LBW, and 1,354 SGA occurred. PTB was the only outcome associated with PM_2.5 mass (OR 1.03, 95% CI 1.002-1.058 per 1 μg/m³). Traffic, oil combustion and secondary sulfates and organics showed independent effects on PTB. Exposure to secondary nitrates was associated with a lower risk of PTB. There was no association between LBW or SGA and source-specific PM_2.5 components or the residual PM_2.5 related to all other sources.

CONCLUSION

This study found an association between PTB and PM_2.5. Traffic, secondary sulfates, and organic and oil combustion were the sources with most consistent association.

Hong-Ou-Mandel interference between independent III-V on silicon waveguide integrated lasers

The versatility of silicon photonic integrated circuits has led to a widespread usage of this platform for quantum information-based applications, including quantum key distribution (QKD). However, the integration of simple high-repetition-rate photon sources is yet to be achieved. The use of weak-coherent pulses (WCPs) could represent a viable solution. For example, measurement device independent QKD (MDI-QKD) envisions the use of WCPs to distill a secret key immune to detector side channel attacks at large distances. Thus, the integration of III-V lasers on silicon waveguides is an interesting prospect for quantum photonics. Here we report the experimental observation of Hong-Ou-Mandel interference with 46±2% visibility between WCPs generated by two independent III-V on silicon waveguide integrated lasers. This quantum interference effect is at the heart of many applications, including MDI-QKD. This Letter represents a substantial first step towards an implementation of MDI-QKD fully integrated in silicon and could be beneficial for other applications such as standard QKD and novel quantum communication protocols.

Higher health effects of ambient particles during the warm season: The role of infiltration factors

A large number of studies have shown much higher health effects of particulate matter (PM) during the warm compared to the cold season. In this paper we present the results of an experimental study carried out in an unoccupied test apartment with the aim of understanding the reasons behind the seasonal variations of the health effects due to ambient PM_2.5 exposure. Measurements included indoor and outdoor PM_2.5 mass and chemical composition as well as particle size distribution of ultrafine particles. Monitoring campaigns were carried out during summer and winter following a ventilation protocol developed to replicate typical occupant behaviour according to a questionnaire-based survey. Our findings showed that seasonal variation of the relationship between ambient and indoor mass concentrations cannot entirely explain the apparent difference in PM toxicity between seasons and size distribution and chemical composition of particles were identified as other possible causes of changes in the apparent PM toxicity. A marked decrease of ultrafine particles (<100 nm) passing from outdoors to indoors was observed during winter; this resulted in higher indoor exposure to nanoparticles (<50 nm) during summer. With regards to the chemical composition, a pooled analysis showed infiltration factors of chemical species similar to that obtained for PM_2.5 mass with values increasing from 0.73 during winter to 0.90 during summer and few deviations from the pooled estimates. In particular, significantly lower infiltration factors and sink effect were found for nitrates and ammonium during winter. In addition, a marked increase in the contribution of indoor and outdoor sulfates to the total mass was observed during summer.

Vertical variation of PM2.5 mass and chemical composition, particle size distribution, NO2, and BTEX at a high rise building

Substantial efforts have been made in recent years to investigate the horizontal variability of air pollutants at regional and urban scales and epidemiological studies have taken advantage of resulting improvements in exposure assessment. On the contrary, only a few studies have investigated the vertical variability and their results are not consistent. In this study, a field experiment has been conducted to evaluate the variation of concentrations of different particle metrics and gaseous pollutants on the basis of floor height at a high rise building. Two 15-day monitoring campaigns were conducted in the urban area of Bologna, Northern Italy, one of the most polluted areas in Europe. Measurements sites were operated simultaneously at 2, 15, 26, 44 and 65 m a.g.l. Several particulate matter metrics including PM_2.5 mass and chemical composition, particle number concentration and size distribution were measured. Time integrated measurement of NO₂ and BTEX were also included in the monitoring campaigns. Measurements showed relevant vertical gradients for most traffic related pollutants. A monotonic gradient of PM_2.5 was found with ground-to-top differences of 4% during the warm period and 11% during the cold period. Larger gradients were found for UFP (∼30% during both seasons) with a substantial loss of particles from ground to top in the sub-50 nm size range. The largest drops in concentrations for chemical components were found for Elemental Carbon (-27%), iron (-11%) and tin (-36%) during winter. The ground-to-top decline of concentrations for NO₂ and benzene during winter was equal to 74% and 35%, respectively. In conclusion, our findings emphasize the need to include vertical variations of urban air pollutants when evaluating population exposure and associated health effects, especially in relation to some traffic related pollutants and particle metrics.

Is particulate air pollution at the front door a good proxy of residential exposure?

The most advanced epidemiological studies on health effects of air pollution assign exposure to individuals based on residential outdoor concentrations of air pollutants measured or estimated at the front-door. In order to assess to what extent this approach could cause misclassification, indoor measurements were carried out in unoccupied rooms at the front and back of a building which fronted onto a major urban road. Simultaneous measurements were also carried out at adjacent outdoor locations to the front and rear of the building. Two 15-day monitoring campaigns were conducted in the period June-December 2013 in a building located in the urban area of Bologna, Italy. Particulate matter metrics including PM2.5 mass and chemical composition, particle number concentration and size distribution were measured. Both outdoor and indoor concentrations at the front of the building substantially exceeded those at the rear. The highest front/back ratio was found for ultrafine particles with outdoor concentration at the front door 3.4 times higher than at the rear. A weak influence on front/back ratios was found for wind direction. Particle size distribution showed a substantial loss of particles within the sub-50 nm size range between the front and rear of the building and a further loss of this size range in the indoor data. The chemical speciation data showed relevant reductions for most constituents between the front and the rear, especially for traffic related elements such as Elemental Carbon, Iron, Manganese and Tin. The main conclusion of the study is that gradients in concentrations between the front and rear, both outside and inside the building, are relevant and comparable to those measured between buildings located in high and low traffic areas. These findings show high potential for misclassification in the epidemiological studies that assign exposure based on particle concentrations estimated or measured at subjects' home addresses.

Characteristics and major sources of carbonaceous aerosols in PM2.5 in Emilia Romagna Region (Northern Italy) from four-year observations

The concentrations of organic and elemental carbon in PM2.5 aerosol samples were measured in two sites of Emilia Romagna (Po Valley, Northern Italy) in eight campaigns during different seasons from 2011 to 2014. Strong seasonality was observed with the highest OC concentrations during the cold periods (≈ 5.5 μg m(-3)) and the lowest in the warm months (≈ 2.7 μg m(-3)) as well as with higher EC levels in fall/winter (≈ 1.4 μg m(-3)) in comparison with spring/summer (≈ 0.6 μg m(-3)). Concerning spatial variability, there were no statistically significant difference (p<0.05) between OC concentrations at the two sampling sites in each campaign, while the EC values were nearly twofold higher levels at the urban site than those at the rural one. Specific molecular markers were investigated to attempt the basic apportionment of OC by discriminating between the main emission sources of primary OC, such as fossil fuels burning - including traffic vehicle emission - residential wood burning, and bio-aerosol released from plants and microorganisms, and the atmospheric photo-oxidation processes generating OCsec. The investigated markers were low-molecular-weight carboxylic acids - to describe the contribution of secondary organic aerosol - anhydrosugars - to quantify primary emissions from biomass burning - bio-sugars - to qualitatively estimate biogenic sources - and Polycyclic Aromatic Hydrocarbons - to differentiate among different combustion emissions. Using the levoglucosan tracer method, contribution of wood smoke to atmospheric OC concentration was computed. Wood burning accounts for 33% of OC in fall/winter and for 3% in spring/summer. A clear seasonal trend is also observed for the impact of secondary processes with higher contribution in the warm seasons (≈ 63%) in comparison with that in colder months (≈ 33%), that is consistent with enhanced solar radiation in spring/summer.

Seasonal variation and source estimation of organic compounds in urban aerosol of Augsburg, Germany

This study reports a general assessment of the organic composition of the PM(2.5) samples collected in the city of Augsburg, Germany in a summer (August-September 2007) and a winter (February-March 2008) campaign of 36 and 30 days, respectively. The samples were directly submitted to in-situ derivatisation thermal desorption gas chromatography coupled with time of flight mass spectrometry (IDTD-GC-TOFMS) to simultaneously determine the concentrations of many classes of molecular markers, such as n-alkanes, iso- and anteiso-alkanes, polycyclic aromatic hydrocarbons (PAHs), oxidized PAHs, n-alkanoic acids, alcohols, saccharides and others. The PCA analysis of the data identified the contributions of three emission sources, i.e., combustion sources, including fossil fuel emissions and biomass burning, vegetative detritus, and oxidized PAHs. The PM chemical composition shows seasonal trend: winter is characterized by high contribution of petroleum/wood combustion while the vegetative component and atmospheric photochemical reactions are predominant in the hot season.

2D autocovariance function for comprehensive analysis of two-way GC-MS data matrix: application to environmental samples

This paper describes a signal processing method for comprehensive analysis of the large data set generated by hyphenated GC-MS technique. It is based on the study of the 2D autocovariance function (2D-EACVF) computed on the raw GC-MS data matrix, extending the procedure previously developed for 1D to 2D signals. It appears specifically promising for GC-MS investigation, in particular to single out ordered patterns in complex data: such patterns can be simply identified by visual inspection from deterministic peaks in the 2D-EACVF plot. A case of order along the retention time axis (x=t(R)) is represented by a horizontal sequence of peaks, located at the same interdistance Δt(R)=b(x), e.g., b(x) is the CH(2) retention time increment between subsequent terms of an homologous series. The order along the fragment mass axis (y=m/z) contains information on analyte fragmentation patterns. Deterministic peaks appear in the 2D-EACVF plot at Δm/z values corresponding to the most abundant ion fragments - dominating fragments in MS spectrum - or to ions generated by repetitive loss of the same ion fragment, i.e., Δm/z=14 amu produced by the [CH(2)]() group loss in n-alkanes. Method applicability was tested by processing GC-MS data of organic extracts of atmospheric aerosol samples: attention is focused on identifying and characterizing homologous series of organics, i.e., n-alkanes and n-alkanoic acids, since they are considered molecular tracers able to track the origin and fate of different organics in the environment.

Copper(II) coordination outside the tandem repeat region of an unstructured domain of chicken prion protein

Combined potentiometric, calorimetric and spectroscopic methods were used to investigate the Cu(2+) binding ability and coordination behaviour of some peptide fragments related to the neurotoxic region of chicken Prion Protein. The systems studied were the following protein fragments: chPrP(106-114), chPrP(119-126), chPrP(108-127), chPrP(105-127) and chPrP(105-133).The complex formation always starts around pH 4 with the coordination of an imidazole nitrogen, followed by the deprotonation and binding of amide nitrogens from the peptidic backbone. At neutral pH, the {N(im), 3N(-)} binding mode is the preferred one. The amide nitrogens participating in the binding to the Cu(2+) ion derive from residues from the N-terminus side, with the formation of a six-membered chelate ring with the imidazolic side chain.Comparison of thermodynamic data for the two histydyl binding domains (around His-110 and His-124), clearly indicates that the closest to the hexarepeat domain (His-110) has the highest ability to bind Cu(2+) ions, although both of them have the same coordination mode. Conversely, in the case of the human neurotoxic peptide region, between the two binding sites, located at His-96 and His-111, the farthest from the tandem repeat region is the strongest one. Finally, thermodynamic data show that chicken peptide is a distinctly better ligand for coordination of copper ions with respect to the human fragment.