Synchrotron Radiation Induced X-ray Fluorescence Research Articles

Element Changes Occurring in Brain Point at the White Matter Abnormalities in Rats Exposed to the Ketogenic Diet During Prenatal Life.

A large number of clinical studies demonstrate that the ketogenic diet (KD) may be an effective approach to the reduction of epileptic seizures in children and adults. Such dietary therapy could also help pregnant women with epilepsy, especially since most antiseizure drugs have teratogenic action. However, there is a lack of medical data, considering the safety of using KD during gestation for the progeny. Therefore, we examined the influence of KD used prenatally in rats on the elemental composition of the selected brain regions in their offspring. For this purpose, synchrotron radiation-induced X-ray fluorescence (SR-XRF) microscopy was utilized, and elements such as P, S, K, Ca, Fe, and Zn were determined. Moreover, to verify whether the possible effects of KD are temporary or long-term, different stages of animal postnatal development were taken into account in our experiment. The obtained results confirmed the great applicability of SR-XRF microscopy to track the element changes occurring in the brain during postnatal development as well as those induced by prenatal exposure to the high-fat diet. The topographic analysis of the brains taken from offspring of mothers fed with KD during pregnancy and appropriate control individuals showed a potential influence of such dietary treatment on the brain levels of elements such as P and S. In the oldest progeny, a significant reduction of the surface of brain areas characterized by an increased P and S content, which histologically/morphologically correspond to white matter structures, was noticed. In turn, quantitative elemental analysis showed significantly decreased levels of Fe in the striatum and white matter of 30-day-old rats exposed prenatally to KD. This effect was temporary and was not noticed in adult animals. The observed abnormalities may be related to the changes in the accumulation of sphingomyelin and sulfatides and may testify about disturbances in the structure and integrity of the myelin, present in the white matter.

Synchrotron induced X-ray fluorescence spectroscopy reveals heavy metal translocation in sludge amended soil-plant systems: assessment of ecological and health risks.

The use of composted sludge from sewage treatment plants as a soil amendment is a common practice of recycling nutrients like organic carbon, nitrogen, and phosphorus. The sewage generated in larger cities of developing countries is often contaminated with various heavy metals (HMs) that ultimately end up in composted sludge. Thus, using such composted sludge is likely to pose ecological and human health risks. Hence, the knowledge of HM translocation in sludge-soil-plant systems is of vital importance. The present study was aimed at investigating the HM translocation in sludge-soil-plant system. The HM translocation was measured using synchrotron radiation-induced x-ray fluorescence spectrometry and atomic absorption spectroscopic techniques. The results indicated high HM mobility (up to 2628.5mgkg-1) from sludge to spinach plant. The metal accumulation (mgkg-1) ranged in the order-Fe (950.55-2628.5) > Zn (20.11-172.13) > Cu (13.86-136.17) > Mn (2.13-34.67) > Cd (0.11-31.17) > Pb (1.50-30.16) > Co (0.18-9.85) As (0.02-7.80) > Cr (0.01-5.69). This observed accumulation depended on the volume of sewage being treated in the sewage treatment plant (STP) and varied in the order control < (8 MLD Bhagwanpur, STP 1) < (80 MLD Dinapur, STP2) < (140 MLD Dinapur, STP3) hence the HM load coming into STPs. The metal transfer factor, bioconcentration factor, and translocation factor values also correlated with the abundance of Fe, Cu, Pb, Cd, and Zn in spinach root and shoot compartments. The carcinogenic risk for heavy metal carcinogens like As, Cd, Cr, and Pb revealed children being more prone to cancer upon spinach consumption. Hence, it is necessary to assess the heavy metals present in the sludge prior to its application in agricultural fields.

Synchrotron Radiation Induced X-Ray Fluorescence for Identification of Light Elements in Plants

Synchrotron Radiation Induced X-Ray Fluorescence for Identification of Light Elements in Plants

Analysis of serum trace elemental content in pre-post chemotherapy breast cancer patients using synchrotron radiation based X-ray fluorescence

Synchrotron Radiation induced X-ray Fluorescence (SRXRF), accelerator based analytical technique, was used to analyze the trace elemental content in the serum of pre-post chemotherapy undergoing breast cancer patients (BCPs) and healthy controls (HCs). SRXRF measurements were carried out on beamline-16 (Microprobe X-fluorescence beamline), Indus synchrotron light source, Raja Ramanna center for Advanced Technology (RRCAT), Indore, India. Validation of SRXRF experimental set-up used in the current work was done by using National Institute of Standards and Technology (NIST) standard reference material bovine liver (1577c) and International Atomic Energy Agency (IAEA) reference material-animal blood (A-13) in the same conditions as that of the studied serum samples. Results show the presence of thirteen trace elements (TEs) K, Ca, Cr, Mn, Fe, Co, Ni, Cu, Zn, Se, Br, Rb, and Pb in both the groups of BCPs and HCs. Concentrations of TEs K, Ca, Cr, Fe, Cu, Br, and Pb were noticed to be higher in pre-chemotherapy BCPs when compared with HCs while content of TEs Mn, Co, Ni, Zn, Se, and Rb were decreased in pre-chemotherapy BCPs. Furthermore, it was observed that the elevated levels of some TEs decreased after chemotherapy. Observed changes in levels of TEs in pre-post chemotherapy BCPs may play an essential role in carcinogenesis and these TEs may be useful to prepare trace-metal based drugs to treat the BCPs and to improve their survival rates.

A combined X-ray fluorescence and infrared microspectroscopy study for new insights into elemental-biomolecular obesity-induced changes in rat brain structures

The objective of our research was to determine the brain changes at the molecular and elemental levels typical of early-stage obesity. Therefore a combined approach using Fourier transform infrared micro-spectroscopy (FTIR-MS) and synchrotron radiation induced X-ray fluorescence (SRXRF) was introduced to evaluate some brain macromolecular and elemental parameters in high-calorie diet (HCD)- induced obese rats (OB, n = 6) and in their lean counterparts (L, n = 6). A HCD was found to alter the lipid- and protein- related structure and elemental composition of the certain brain areas important for energy homeostasis. The increased lipid unsaturation in the frontal cortex and ventral tegmental area, the increased fatty acyl chain length in the lateral hypothalamus and substantia nigra as well as the decreased both protein α helix to protein β- sheet ratio and the percentage fraction of β-turns and β-sheets in the nucleus accumbens were revealed in the OB group reflecting obesity-related brain biomolecular aberrations. In addition, the certain brain elements including P, K and Ca were found to differentiate the lean and obese groups at the best extent. We can conclude that HCD-induced obesity triggers lipid- and protein- related structural changes as well as elemental redistribution within various brain structures important for energy homeostasis. In addition, an approach applying combined X-ray and infrared spectroscopy was shown to be a reliable tool for identifying elemental-biomolecular rat brain changes for better understanding the interplay between the chemical and structural processes involved in appetite control.

Correlative nano-imaging of metals and proteins in primary neurons by synchrotron X-ray fluorescence and STED super resolution microscopy: Experimental validation

BackgroundIt is becoming increasingly clear that biological metals such as iron, copper or zinc are involved in synaptic functions, and in particular in the mechanisms of synaptogenesis and subsequent plasticity. Understanding the role of metals on synaptic functions is a difficult challenge due to the very low concentration of these elements in neurons and to the submicrometer size of synaptic compartments. New methodTo address this challenge we have developed a correlative nano-imaging approach combining metal and protein detection. First, stimulated emission depletion (STED) microscopy, a super resolution optical microscopy technique, is applied to locate fluorescently labeled proteins. Then, synchrotron radiation induced X-ray fluorescence (SXRF) is performed on the same regions of interest, e.g. synaptic compartments. ResultsWe present here the principle scheme that allows this correlative nano-imaging and its experimental validation. We applied this correlative nano-imaging to the study of the physiological distribution of metals in synaptic compartments of primary rat hippocampal neurons. We thus compared the nanometric distribution of metals with that of synaptic proteins, such as PSD95 or cytoskeleton proteins. Comparison with existing method(s)Compared to correlative imaging approaches currently used to characterize synaptic structures, such as electron microscopy correlated with optical fluorescence, our approach allows for ultra-sensitive detection of trace metals using highly focused synchrotron radiation beams. ConclusionWe provide proof-of-principle for correlative imaging of metals and proteins at the synaptic scale and discuss the present limitations and future developments in this area.

Distribution, structure, and mineralization of calcified cartilage remnants in hard antlers

Antlers are paired deciduous bony cranial appendages of deer that undergo a regular cycle of growth, death and casting, and constitute the most rapidly growing bones in mammals. Antler growth occurs in an appositional mode and involves a modified form of endochondral ossification. In endochondral bones, calcified cartilage is typically a transient tissue that is eventually completely replaced by bone tissue. We studied the distribution and characteristics of calcified cartilage in hard antlers from three deer species (Capreolus capreolus, Cervus elaphus, Dama dama), i.e., in antlers from which the skin (velvet) had been shed. Remnants of calcified cartilage were regularly present as part of the trabecular framework in the late formed, distal antler portions in all three species, whereas this tissue was largely or completely missing in the more proximal antler portions. The presence of calcified cartilage remnants in the distal antler portions is attributed to the limited antler lifespan of only a few months, which is also the reason for the virtual lack of bone remodeling in antlers. The calcified cartilage matrix was more highly mineralized than the antler bone matrix. Mineralized deposits were observed in some chondrocyte lacunae and occasionally also in osteocyte lacunae, a phenomenon that has not previously been reported in antlers. Using synchrotron radiation-induced X-ray fluorescence (SR-XRF) mapping, we further demonstrated increased zinc concentrations in cement lines, along the inner borders of incompletely formed primary osteons, along the walls of partly or completely mineral-occluded chondrocyte and osteocyte lacunae, and in intralacunar mineralized deposits. The present study demonstrates that antlers are a promising model for studying the mineralization of cartilage and bone matrices and the formation of mineralized deposits in chondrocyte and osteocyte lacunae.

Nickel particles are present in Crohn's disease tissue and exacerbate intestinal inflammation in IBD susceptible mice

Crohn's disease is an inflammatory disease of the gut caused by a complex interplay among genetic, microbial, and environmental factors. The intestinal tract is constantly exposed to metals and other trace elements ingested as food. Synchrotron radiation-induced X-ray fluorescence spectroscopy and X-ray absorption fine structure analysis revealed the deposition of nickel particles within Crohn's disease tissue specimens. After nickel particle stimulation, THP-1 cells showed filopodia formation and autophagic vacuoles containing lipid bodies. Nickel particles precipitated colitis in mice bearing mutations of the IBD susceptibility protein A20/TNFAIP3. Nickel particles also exacerbated dextran sulfate sodium-induced colitis in mice harboring myeloid cell-specific Atg5 deficiency. These findings illustrate that nickel particle ingestion may worsen Crohn's disease by perturbing autophagic processes in the intestine, providing new insights into environmental factors in Crohn's disease pathogenesis.

Machine learning based quantification of synchrotron radiation-induced x-ray fluorescence measurements—a case study

In this work, we describe the use of artificial neural networks (ANNs) for the quantification of x-ray fluorescence measurements. The training data were generated using Monte Carlo simulation, which avoided the use of adapted reference materials. The extension of the available dataset by means of an ANN to generate additional data was demonstrated. Particular emphasis was put on the comparability of simulated and experimental data and how the influence of deviations can be reduced. The search for the optimal hyperparameter, manual and automatic, is also described. For the presented case, we were able to train a network with a mean absolute error of 0.1 weight percent for the synthetic data and 0.7 weight percent for a set of experimental data obtained with certified reference materials.

Influence of copper element distribution and speciation on the color of Chinese underglaze copper-red porcelain in the Yuan dynasty

A shard of Chinese underglaze copper-red porcelain from the Yuan dynasty (AD 1271–1368) made in the Jingdezhen kiln was measured by synchrotron radiation-induced X-ray fluorescence mapping and X-ray absorption near-edge spectroscopy to investigate the influence of copper element distribution and speciation on the color of porcelain. In black-colored region, copper accumulates at the interface between the body and glaze layers with metallic copper particles as the main speciation. In contrast, Cu is irregularly distributed in the red-colored region with multi-valence speciation. The differences in Cu distribution and speciation in black- and red-colored regions indicate that they are the main factors influencing the different colors of copper-red underglaze porcelain.

HOUTTUYNIA (HOUTTUYNIA CORDATA THUNB.) – NEW VEGETABLE AND MEDICINAL CROP FOR RUSSIA (MORPHOLOGICAL FEATURES AND BIOCHEMICAL COMPOSITION)

Taking into account the importance of Hauttuynia cordata as a vegetable and medicinal plant in the South-East Asia, and the possibility of its cultivation in a temperate climate, the morphological and biochemical features of the plants belonging to ‘common’ and ‘variegated’ forms were studied in conditions of a greenhouse. We used a peat as a sub-strate for growing plants. The content of macroand microelements in rhizomes and leaves was estimated with use of the synchrotron radiation induced X-ray fluorescence analysis (SR-XRF). During three months of cultivation, the total phytomass of ‘common form’ increased from 4.7 ± 0.84 g to 30.3 ± 8.00 g, i.е. in 6.4 times, while in rhizomes it reached 51-56% out of the total phytomass. The size of the leaves of ‘variegated form’ was 15 29% less, as com-pared with the ‘usual form’. The height of the plants was 25.9 ± 0.98 cm in the ‘usual’ and 29.0 ± 0.62 cm in the ‘variegated’ form, the length and width of the leaf blade were 6.6 ± 0.26 x 5.9 ± 0.25 and 4.70 ± 5.00 x 4.90 ± 5.50 cm, respectively. Plants of the ‘common’ form formed api-cal, elongated, dense, ctenopod spine inflorescence with flowers lacking perianth, with three stamens and 3-4 fused carpal forms forming syncarpous gynoecium. ‘Variegated’ form did not form any inflorescences. H.cordata leaves con-tain 35, 6 mg% ascorbic acid, rhizomes ‒ 14.2 mg%. Leaves of H.cordata mainly accumulated Mn, Fe and Cu, and the roots ‒ Fe, Co, Cu and Zn. It is necessary to carry out the further study on new promising functional food.

Spectroscopic Approaches to Tracking Metal-based Drugs in Cells and Tissue.

Metal-based drugs with novel targets and modes of action are increasingly being developed as alternatives to classical platinum(ii) chemotherapeutics. Imaging methods in tumour cells and tissues offer valuable insights into the behaviour of these novel complexes; however, mapping the distribution of metal ions and complexes within cellular environments remains challenging. The advantages and limitations of three modes of imaging: synchrotron radiation-induced X-ray fluorescence, mass spectrometry, and fluorescence microscopy are discussed in this review, with particular emphasis on their use in imaging ruthenium-based drugs.

Determination of main rock-forming elements, strontium and zirconium by X-ray fl uorescence analysis for the geochemical characterization of bottom sediments

Quantitative X-ray fluorescence determination of major rock-forming oxides (Na 2 O, MgO, Al 2 O 3 , SiO 2 , P 2 O 5 , K 2 O, CaO, TiO 2 , MnO and Fe 2 O 3 ) and some microelements (Sr and Zr) was performed in the samples of 143 cm-long sediment core of Lake Baunt (Buryat Republic) by the wavelength-dispersive X-ray fluorescence analysis on the S8 Tiger spectrometer. Calibration curves were obtained by measuring the certified reference materials of the sedimentary rocks. Both analyzed and reference samples were prepared as glass beads by fusion of 110 mg of sample with1.1 g of lithium metaborate. We have used 110 mg mass to ensure the formation of beads with appropriate 10 to 12 mm size across to be measured by the spectrometer with8 mm mask. Rh Kα Compton line was used as a background standard for Sr and Zr determination. The repeatability did not exceed the allowable standard deviation for a wide range of concentrations. Results of major rock-forming oxides determination were compared with the data of spectrophotometry and flame photometry techniques, results of Sr and Zr determination were compared with the data of synchrotron radiation excited X-ray fluorescence technique. All results of the X-ray fluorescence analysis were accepted as satisfactory. Quantitative analysis of each centimeter of Lake Baunt sediment core allowed building first reconstructions of the local environment during the last 7000 years with unique resolution of about 100 years. Keywords: wavelength-dispersive X-ray fluorescence analysis, synchrotron radiation induced X-ray fluorescence analysis, sediments, paleoclimate (Russian) DOI: http://dx.doi.org/10.15826/analitika.2017.21.1.003 A.A. Amosova, V.M. Chubarov,E.V. Kaneva, Iu.N. Markova Vinogradov Institute of Geochemistry, Siberian Branch of Russian Academy of Sciences, ul. Favorsky , 1A, Irkutsk , 664033, Russian Federation

Synchrotron Radiation-Induced X-Ray Fluorescence (SRXRF) Analyses Of The Bernstorf Gold

The gold finds from Bernstorf, in the Freising district of Bavaria, were discovered in 1998, in the area of a Bronze Age settlement. First analyses with X-ray fluorescence (XRF) revealed gold of an unusually high purity grade, which was explained by the use of cementation techniques. A newer analysis with laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) indicated an even higher purity. The analytical results were the starting point of an ongoing discussion. In this study, we re-analysed 11 gold samples with synchrotron radiation–induced X-ray fluorescence at the BAMline at BESSY. In a thorough analysis, different excitation and detection conditions were applied to confirm or disprove the previous results. It was shown that the purity of the gold from the specimen is higher than 99.9%. The main impurities are silver in a range between 20 and 200 μg g−1 and copper between 1 and 10 μg g−1. The results are in very good agreement with the LA–ICP–MS measurements and provide basic information for discussions about provenance, processing techniques or considerations of authenticity.

Forefoot diseases in art

Silverpoint drawings from the Renaissance are among the most precious and rarest treasures of graphical art. Our research group is particularly interested in the analysis of silverpoint drawings by Albrecht Dürer (1471–1528). A very sensitive and non-destructive analytical method, either spatially resolved synchrotron-radiation induced X-ray fluorescence (SY-XRF) or proton-induced X-ray emission (PIXE), is needed to determine the chemical composition of the very faint silver marks on such drawings. Dürer drawings from the collection of the Albertina, Vienna, were analyzed to amend existing data on Dürer drawings. For this purpose an external-beam PIXE setup was installed at the Vienna Environmental Research Accelerator (VERA). It allows to analyze a spot of ∼0.15 mm on the object in air with 3 MeV protons, and to detect the emitted X-rays that are characteristic for the chemical composition with very good sensitivity and without harming the precious objects. After successful measurements on artificial test samples, four original silverpoint drawings were investigated: two portraits from Albrecht Dürer’s very early period (self-portrait and portrait of his father) and two drawings from Dürer’s sketch book of his travel to the Netherlands 1520/21.

Size segregation behavior of heavy metals in superfine pulverized coal using synchrotron radiation-induced X-ray fluorescence

The emissions of heavy metals during coal utilization exert severe adverse impacts on the public health and ecosystems, which has attracted widespread attention throughout the world. The determination of the chemical forms plays a key role in the study of the heavy-metal partitioning behavior. However, due to the complex nature of coal, researchers haven’t reached a unanimous agreement on the modes of occurrence, association, distribution, and concentration information of these elements. In this paper, a direct, non-destructive, and single-particle analytical method, i.e., synchrotron radiation-induced X-ray fluorescence spectrometry (SR-XRF), was utilized to study the micro-scale characteristics of heavy metals in coal. The forms of occurrence, spatial distribution, and associations of several concerned elements were visually inspected from μ-XRF maps. Besides, the size dependence characteristics of elemental composition, spatial distribution, and speciation in raw coal particles were featured. Finally, the detected elements were categorized into three groups according to their different affinities and size-segregated behavior. The size effects on the distribution patterns of the elements in coal particles were summarized.

Does titanium in ionic form display a tissue-specific distribution?

Most studies have focused on the biodistribution of titanium(IV) oxide as nanoparticles or crystals in organism. But several reports suggested that titanium is released from implant in ionic form. Therefore, gaining insight into toxicokinetics of Ti ions will give valuable information, which may be useful when assessing the health risks of long-term exposure to titanium alloy implants in patients. A micro synchrotron radiation-induced X-ray fluorescence (µ-SRXRF) was utilized to investigate the titanium distribution in the liver, spleen and kidneys of rats following single intravenous or 30-days oral administration of metal (6 mg Ti/b.w.) in ionic form. Titanium was mainly retained in kidneys after both intravenous and oral dosing, and also its compartmentalization in this organ was observed. Titanium in the liver was non-uniformly distributed—metal accumulated in single aggregates, and some of them were also enriched in calcium. Correlation analysis showed that metal did not displace essential elements, and in liver titanium strongly correlated with calcium. Two-dimensional maps of Ti distribution show that the location of the element is characteristic for the route of administration and time of exposure. We demonstrated that µ-SRXRF can provide information on the distribution of titanium in internal structures of whole organs, which helps in enhancing our understanding of the mechanism of ionic titanium accumulation in the body. This is significant due to the popularity of titanium implants and the potential release of metal ions from them to the organism.

The Nature of Iron Deposits Differs between Symptomatic and Asymptomatic Carotid Atherosclerotic Plaques.

Iron within atherosclerotic plaque has been implicated as a catalyst of oxidative stress that causes progression of plaque, and plaque rupture. Iron is believed to accumulate within plaque by incorporation of erythrocytes following plaque rupture and hemorrhage. There is only indirect evidence to support this hypothesis. Plaque specimens were obtained from ten symptomatic and fifteen asymptomatic patients undergoing carotid endarterectomy at a single institution. Plaques were sectioned for study using synchrotron radiation induced X-ray fluorescence the study the distribution of zinc, calcium and iron. Histologic staining was carried out with Prussian Blue, and immunohistochemical staining was done to localize macrophages with CD68. Data were compared against patient clinical variables. Ten symptomatic (15 ± 10 days between index symptoms and surgery) and fifteen asymptomatic carotid plaques were studied. Zinc and calcium co-localized in mineralized areas of symptomatic and asymptomatic plaque. Iron was identified away from zinc and calcium in both symptomatic and asymptomatic plaques. Within the symptomatic plaques, iron was found within the thrombus associated with plaque rupture and hemorrhage. It did not stain with Prussian Blue, but was found in association with CD68 positive macrophages. In symptomatic plaques, the abundance of iron showed an association with the source patient’s LDL cholesterol (R2 = 0.39, Significance F = 0.05). Iron in asymptomatic plaque was present as hemosiderin/ferritin that stained positive with Prussian Blue, and was observed in association with CD68 positive macrophages. Iron in acutely symptomatic plaques is found within thrombus, in the presence of macrophages. The abundance of iron in symptomatic plaques is associated with the source patient’s LDL cholesterol. Within asymptomatic plaques, iron is found in association with macrophages, as hemosiderin/ferritin.

On the distribution of uranium in hair: Non-destructive analysis using synchrotron radiation induced X-ray fluorescence microprobe techniques

In the present study the distribution of uranium in single human hair shafts has been evaluated using two synchrotron radiation (SR) based micro X-ray fluorescence techniques; SR μ-XRF and confocal SR μ-XRF. The hair shafts originated from persons that have been exposed to elevated uranium concentrations. Two different groups have been studied, i) workers at a nuclear fuel fabrication factory, exposed mainly by inhalation and ii) owners of drilled bedrock wells exposed by ingestion of water. The measurements were carried out on the FLUO beamline at the synchrotron radiation facility ANKA, Karlsruhe. The experiment was optimized to detect U with a beam size of 6.8μm×3μm beam focus allowing detection down to ppb levels of U in 10s (SR μ-XRF setup) and 70s (SR confocal μ-XRF setup) measurements. It was found that the uranium was present in a 10–15μm peripheral layer of the hair shafts for both groups studied. Furthermore, potential external hair contamination was studied by scanning of unwashed hair shafts from the workers. Sites of very high uranium signal were identified as particles containing uranium. Such particles, were also seen in complementary analyses using variable pressure electron microscope coupled with energy dispersive X-ray analyzer (ESEM–EDX). However, the particles were not visible in washed hair shafts.These findings can further increase the understanding of uranium excretion in hair and its potential use as a biomonitor.

Kerb and urban increment of highly time-resolved trace elements in PM&amp;lt;sub&amp;gt;10&amp;lt;/sub&amp;gt;, PM&amp;lt;sub&amp;gt;2.5&amp;lt;/sub&amp;gt; and PM&amp;lt;sub&amp;gt;1.0&amp;lt;/sub&amp;gt; winter aerosol in London during ClearfLo 2012

Abstract. Ambient concentrations of trace elements with 2 h time resolution were measured in PM10–2.5, PM2.5–1.0 and PM1.0–0.3 size ranges at kerbside, urban background and rural sites in London during winter 2012. Samples were collected using rotating drum impactors (RDIs) and subsequently analysed with synchrotron radiation-induced X-ray fluorescence spectrometry (SR-XRF). Quantification of kerb and urban increments (defined as kerb-to-urban and urban-to-rural concentration ratios, respectively), and assessment of diurnal and weekly variability provided insight into sources governing urban air quality and the effects of urban micro-environments on human exposure. Traffic-related elements yielded the highest kerb increments, with values in the range of 10.4 to 16.6 for SW winds (3.3–6.9 for NE) observed for elements influenced by brake wear (e.g. Cu, Sb, Ba) and 5.7 to 8.2 for SW (2.6–3.0 for NE) for other traffic-related processes (e.g. Cr, Fe, Zn). Kerb increments for these elements were highest in the PM10–2.5 mass fraction, roughly twice that of the PM1.0–0.3 fraction. These elements also showed the highest urban increments (~ 3.0), although no difference was observed between brake wear and other traffic-related elements. All elements influenced by traffic exhibited higher concentrations during morning and evening rush hours, and on weekdays compared to weekends, with the strongest trends observed at the kerbside site, and additionally enhanced by winds coming directly from the road, consistent with street canyon effects. Elements related to mineral dust (e.g. Al, Si, Ca, Sr) showed significant influences from traffic-induced resuspension, as evidenced by moderate kerb (3.4–5.4 for SW, 1.7–2.3 for NE) and urban (~ 2) increments and increased concentrations during peak traffic flow. Elements related to regional transport showed no significant enhancement at kerb or urban sites, with the exception of PM10–2.5 sea salt (factor of up to 2), which may be influenced by traffic-induced resuspension of sea and/or road salt. Heavy-duty vehicles appeared to have a larger effect than passenger vehicles on the concentrations of all elements influenced by resuspension (including sea salt) and wearing processes. Trace element concentrations in London were influenced by both local and regional sources, with coarse and intermediate fractions dominated by traffic-induced resuspension and wearing processes and fine particles influenced by regional transport.