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Abstract Urban air quality is strongly affected by the surrounding local traffic and emission compounds such as particulate matter (PM) and heavy metals, which pose a serious health risk globally. These compounds are known to be traffic related, but fairly few studies have focused on point source emissions of traffic flow. In this study we applied magnetic biomonitoring using moss bags (Sphagnum papillosum) to study the point source emissions caused by stop-and-go traffic. Moss bags were placed alternately at traffic light crossings (n = 19) and midway areas between the crossings (n = 29) along four street transects and one separate traffic light crossing in the city of Turku, Finland. Samples were analysed for mass-specific magnetic susceptibility (χ), hysteresis parameters and elemental components. The PM was composed of fine-grained pseudo-single-domain (PSD) magnetite and the concentrations of χ, Cu, Mo and Sb significantly differed between traffic light crossing areas compared to midway areas. The elements Ba, Cu, Fe, Mo, Ni, Pb, Sb and Ti showed moderate to high levels of accumulation and correlated strongly with χ and saturation magnetisation (M S). Our results show that a high volume of stop-and-go traffic is a major source of harmful PM pollution especially along busy main roads. To improve urban air quality and public health we strongly advice the municipal administrations to pay more attention to urban planning and traffic management to reduce stop-and-go traffic and decrease the levels of urban PM pollution. Highlights • Magnetic biomonitoring is an effective and low-cost method to monitor air quality. • Stop-and-go traffic a major source for magnetic particles and heavy metals. • Pollution levels more elevated at traffic light crossings than in midway areas. • Urban planning and traffic management needed to reduce PM from stop-and-go traffic. [ABSTRACT FROM AUTHOR]

Urban areas form a mosaic of microenvironments and structures, such as street canyons that are susceptible to elevated levels of traffic related pollutants. Street canyons are a relevant topic in air quality research and modelling since they are prone to reduced natural ventilation and when exposed to increased traffic emissions, can pose a serious risk to public health. We applied magnetic biomonitoring using moss bags to evaluate the quality of Operational Street Pollution Model (OSPM) and to study vertical distribution of modelled particulate matter (PM), magnetic PM and heavy metal pollution in a street canyon in Turku and Helsinki, Finland. Moss bags were attached on opposite sides of the streets at 3-, 6-, 9- and 12-m heights for 44 days in late autumn. Samples were analysed for mass-specific magnetic susceptibility (χ), hysteresis parameters and elemental components. High χ values and elemental concentrations of Fe, Al, Ti, Zn, Mn, Cu and Ba were found in both street canyons. Compared to measurements with airborne magnetic PM, the OSPM model underestimated the difference in PM concentrations between the opposite street canyon faces and overestimated the dilution of PM concentrations with altitude. In Turku the results between the OSPM model and magnetic measurements were incompatible. We suspect this is due to meteorological model input data from a distant weather station, street canyon features and a high slope angle contributing to non-uniform emissions in the street canyon. We demonstrate that the moss bag technique is a versatile tool to understand the small-scale variations of concentrations in a variety of complex urban environments. • Magnetic biomonitoring effective in evaluating air quality modelling. • Street canyons prone to high magnetic PM concentrations. • PM concentrations show discrepancies between OSPM model and magnetic biomonitoring. • Street canyon characters and winter conditions caused inhomogeneous emissions. [ABSTRACT FROM AUTHOR]

Hydrotalcites containing Ni(II) and Fe(III) was synthesized using co-precipitation method to demonstrate their use as a support material for the homogeneous deposition of Au and Au-Pd nanoparticles via sol-immobilization. Detailed characterization performed by UV–Vis, ATR-FTIR, TGA, Mössbauer spectroscopy, SEM, Cryo-TEM, BET analysis evidenced the structural, morphological and textural properties of the passive support and decoration of nanoparticles on the surface of LDH and evidenced the property to be used as photocatalysts. These materials proved to be efficient photocatalysts for the degradation of environmentally important Orange II dye (OII) as a model pollutant. Different experimental parameters influencing the photocatalytic activity viz., catalyst dosage, initial dye concentration and reusability of the catalyst were studied. Langmuir-Hinshelwood model was used to analyze the kinetics of the photocatalytic process. Heteronuclear Au-Pd nanoparticles immobilized on NiFeCO 3 LDH was found to be the best photocatalyst degrading about 95% of the dye (25 mg/L) after 60 min and this activity remains to be nearly the same after recycling the catalyst. This enhancement in the activity was attributed to the presence of Au-Pd Nps, with specific surface area (80 m 2 /g), and band gap (2.7 eV). Our study shows the prepared photocatalyst anticipates being a promising candidate for other photocatalytic applications. [ABSTRACT FROM AUTHOR]

We report photo-induced colossal magnetoresistive insulator-metal transition (IMT) in Pr 0.6 Ca 0.4 MnO 3 thin films under much reduced applied magnetic field. The colossal effect was studied as a function of film thickness and thus with variable structural properties. Thorough structural, magnetic and magnetotransport characterization under light shows that the highest effect on the transition field can be obtained in the thinnest film (38 nm). However, due to the substrate induced strain of this film the required magnetic field for IMT is quite high. The best crystalline properties of the 110 nm film lead to the lowest IMT field under light and 10 9 % change in resistance at 10 K. With increasing thickness, the film properties start to move more toward the bulk material and, hence, IMT is no more observed under the applied field of 9 T. Our results indicate that for obtaining large photo-induced CMR, the best epitaxial quality of thin films is essential. [ABSTRACT FROM AUTHOR]

Magnetic and photoluminescent properties of nickel-doped ZnSe crystals with impurity concentrations varied by changing the Ni amount in the source material from 0.001 to 0.50 at.% are studied in 5–300 K temperature range. Investigation of magnetic properties shows that Ni impurity in ZnSe forms isolated paramagnetic centers and probability of Ni–Ni pairs formation is negligible due to low Ni concentration in the samples. The contribution of Ni impurity to edge emission and its influence on infra-red emission are discussed. It is found that complete concentration quenching of luminescence within all studied spectral range is observed starting with Ni concentration of 0.50 at.%. [ABSTRACT FROM AUTHOR]