Evaluation and application of biomagnetic monitoring of traffic-derived particulate pollution (original) (raw)
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Atmospheric Environment, 1999
We report here the novel use of rapid and non-destructive magnetic measurements to investigate the spatial and temporal pattern of urban dust loadings on leaves of roadside trees. More than 600 leaves were collected from birch trees and their remanent magnetization (IRM 2) determined and normalized for the leaf area. The results show that this normalised 2-D magnetization is dominantly controlled by the tree's distance to the road. The magnetic analyses enabled detailed mapping of the spatial and temporal variations of vehicle-derived particulates. Higher 2D-magnetizations, indicating higher magnetic dust loadings, were measured for leaves collected adjacent to uphill road sections than for those next to downhill sections. This suggests that vehicle emissions, rather than friction wear or resuspended road dust, are the major source of the roadside magnetic particles. Additional magnetic analyses suggest that the particle size of the magnetic grains dominantly falls in the range classi"ed for airborne particulate matter as PM ((2.5 m), a particle size hazardous to health due to its capacity to be respired deeply into the lungs. Thus, the leaf magnetizations relate directly to release into the atmosphere of harmful vehicle combustion products. For leaves from individual trees, magnetization values fall signi"cantly from high values proximal to the roadside to lower values at the distal side, con"rming the ability of trees to reduce aerosol concentrations in the atmosphere. Magnetic analysis of leaves over days and weeks shows that rainfall produces a net decrease in the leaf magnetic loadings.
Magneto-biomonitoring of intra-urban spatial variations of particulate matter using tree leaves
Environmental geochemistry and …, 2009
Preliminary mineral magnetic results from a pilot project investigating the suitability of roadside tree leaves as depositories of vehicular pollution are presented. Tree leaf surfaces (Lime: Tilia europaea; Sycamore: Acer pseudoplatanus) at four roadside and one woodland location in Wolverhampton, UK, have been monitored (July 2003 to November 2003). Mineral magnetic technologies have revealed spatial variations of particulate pollution concentration throughout the conurbation and data analysis indicates that magnetic concentration parameters are suitable proxies for fine particulate pollution, which are particularly hazardous to health. Site-specific traffic management and associated vehicle behaviour appear to be chiefly responsible for the magnetic concentration differences between sites. Magneto-biomonitoring in this way allows the highresolution spatial mapping of particulate matter (PM) pollution, which may also benefit epidemiology in better assessing exposure to vehicular-derived particulates. Given the speed, measurement sensitivity and non-destructive nature of the technique, it is proposed that this low-cost approach offers some advantages over centralised monitoring stations to monitor urban roadside particulate pollution.
Atmospheric Environment, 2018
Environmental magnetism, and the magnetic leaf signal in particular, is amply investigated and applied as proxy for atmospheric particulate matter pollution. In this study, we investigated the magnetic signal of annual segments of tree branches, and the composition of particles deposited hereon. Branches are, contrary to leaves, available during leaf-off seasons and exposed to air pollution year-round. We examined the intra-and inter-tree variation in saturation isothermal remanent magnetization (SIRM) of branch internodes of London plane (Platanus x acerifolia Willd.) trees in an urban environment. The branch SIRM, normalized by surface area, ranged from 18 to 650 x 10-6 A; the median amounted to 106 x 10-6 A. Most of the branch magnetic signal was attributed to the epidermis or bark, and the presence of metal-containing particles on the branch surfaces was confirmed by SEM-EDX. The location of the trees and the height, depth in the crown and the age of the branches significantly influenced the branch SIRM. The median branch SIRM was up to 135% higher near a busy ring road than in quiet environments (city park and quiet street canyon), and was linked to the presence of Fe-rich particles with co-occurrence of trace metals such as Cr, Cu, Zn and Mn on the branch surface. Within the tree crowns, the branch SIRM generally decreased with increasing height, and was 22% higher in the interior than at the periphery of the crowns. Within the branches, the SIRM increased with each year of exposure, but did not relate to year-to-year variation in particle concentrations due to branch surface changes (epidermis shedding). Our results provide indications that branches can be a valuable alternative for biomagnetic monitoring of particulate pollution, but intra-tree variability in branch SIRM can be substantial due to the branch's location in the tree and branch age. Keywords environmental magnetism, urban trees, air quality, particulate pollution, branch bark Highlights-We measured magnetization (SIRM) of urban-tree branches as proxy for particulate deposition.-Branch SIRM, mainly confined to the bark surface, increases with each year of exposure.-Branch SIRM reveals similar spatial intra-and inter-tree variation patterns as leaf SIRM.-Branches can be a valuable alternative for biomagnetic monitoring with leaves.
Atmospheric Environment, 2012
Motorised traffic generates large numbers of small-sized, magnetisable particulate pollutants in the urban environment. Exposure to these small particles has been associated with adverse effects on human health. Magnetic properties of these particles are, therefore, increasingly used for assessing environmental stress. Biomonitoring of magnetic particles accumulated on leaf surfaces may provide information on the concentration of, and exposure to, atmospheric particles at high spatial resolution. In this study, leaf saturation isothermal remanent magnetisation (SIRM) of three urban tree types (Carpinus betulus and Tilia sp. with hairy and non-hairy leaves) was measured at high spatial resolution in the city of Gent, Belgium, in June and September 2009. We compared leaf SIRM between land use classes with different urban habitat quality. In a multiple regression model, we tried to explain the spatial variability in leaf SIRM by tree species, sampling height, distance to the nearest road and its traffic intensity, tram frequency and a measure for regional traffic emissions (derived from traffic intensity of and the distance to the most important highways around and in the city in the main four wind directions). We found that the leaf SIRM was significantly influenced by tree species, distance to the nearest road and its traffic intensity and tram frequency. The SIRM significantly increased with increasing traffic intensity and tram frequency and by decreasing distance to the nearest road. It is concluded that leaf SIRM is a good bioindicator for monitoring spatial variation of magnetic particles in urban environments.
Monitoring Of Vehicles Derived Particulates Using Magnetic Properties Of Leaves
Environmental Monitoring and Assessment, 2006
Biomonitoring of vehicle-derived particulates is conducted by taking magnetic measurements of roadside tree leaves. Remanent magnetization (IRM300 mT) of more than 400 Delbergia sissoo leaves was determined and IRM300 mT normalized for the leaf area. The normalized 2-D magnetization as shown by results is dominantly controlled by the tree's distance to the road. The spatial and temporal variations of vehicle-derived particulates were mapped using magnetic analysis. 2D-magnetizations values were higher for leaves collected adjacent to major road sections than for those from village road suggesting vehicle emissions, rather than resuspended road dust, as the major cause of magnetic particles of roadside tree leaves. Vehicles derived particulates are responsible for tree leaf magnetism, and the leaf magnetizations values fall significantly from high values proximal to the roadside to lower values at the distal side. This suggests the ability of trees to reduce particulates concentrations in the atmosphere. The rainfall produces a net decrease in the leaf magnetic dust loadings.
Environmental Pollution, 2013
Recently, biomagnetic monitoring of tree leaves has proven to be a good estimator for ambient particulate concentration. This paper investigates the usefulness of biomagnetic leaf monitoring of crown deposited particles to assess the spatial PM distribution inside individual tree crowns and an urban street canyon in Ghent (Belgium). Results demonstrate that biomagnetic monitoring can be used to assess spatial PM variations, even within single tree crowns. SIRM values decrease exponentially with height and azimuthal effects are obtained for wind exposed sides of the street canyon. Edge and canyon trees seem to be exposed differently. As far as we know, this study is the first to present biomagnetic monitoring results of different trees within a single street canyon. The results not only give valuable insights into the spatial distribution of particulate matter inside tree crowns and a street canyon, but also offer a great potential as validation tool for air quality modelling.
Geophysical Journal International, 2008
Elevated levels of airborne particulate matter (PM) are a current problem for air quality in many major metropolitan areas. Many European cities have tightened the PM limits in the air, due to advances in monitoring PM levels. In order to establish guidelines for monitoring and curbing anthropogenic PM output, a better understanding of its origin, composition and diffusion is required. Biomonitoring of magnetic properties of tree leaves has been suggested previously to be a good approach to measure pollution levels in cities both in space and time. We report on a magnetic biomonitoring study of PM in the city of Rome, conducted from 2005 October to December. We collected approximately 180 different sample sets of tree leaves of Quercus ilex, an evergreen oak widely distributed in Rome, at 112 different locations. Specific magnetic susceptibility χ of the leaf is used as a fast, easy and cost-effective proxy to assess levels of primary anthropogenic airborne PM pollution. Highly polluted areas correlate with high traffic areas, with an average susceptibility value of χ = 3.2 × 10 −7 m 3 kg −1 . Low traffic zones are characterized by values more than an order of magnitude lower at χ = 1.4 × 10 −8 m 3 kg −1 , and the background magnetic susceptibility is around χ = 2.6 × 10 −9 m 3 kg −1 . The data show that distance dependence from the source is the most significant factor for the concentration of magnetic PM, and that pollution levels and sources can be reliably delineated by measuring magnetic susceptibility values on tree leaf samples of Q. ilex. A new protocol for magnetic susceptibility measurements is proposed, in order to account for changes due to water evaporation in the leaves as a function of time after collection of the samples. Additional magnetic analyses, such as acquisition of artificial remanences and hysteresis properties, were used to characterize the mineralogy and grain size of the magnetic PM. The results indicate that the population of ferrimagnetic phases have a homogenous composition and grain size throughout the investigated area.
Atmospheric Environment, 2008
Exposure to metal-rich particulate pollution is associated with adverse health outcomes. In particular, lead has recently been shown to be toxic in young children even at low levels previously considered 'safe' (e.g. Koller et al., 2004). Lead poisoning from vehicle pollution has been addressed internationally by removal of leaded petrol but toxic blood lead levels in children continue to be reported in urban areas (Rabito et al., 2004; Mathee et al., 2002), the source possibly resuspended roadside soil, enriched in lead due to previous leaded fuel usage (Young et al., 2002; Filipelli et al., 2005). Here, we use paired geochemical and magnetic analyses of natural biomonitors-kerbside tree leaves-, and of air sample filters, to examine contemporary sources of particulate pollution, and show that co-associated, ultrafine (< 1 m) lead-and iron-rich particles are emitted as vehicle-derived pollutants. Higher and strongly correlated lead, iron and magnetic remanence values were found closer to roads and on the road-proximal rather than road-distal sides of trees. Critically, highest pollutant values occurred on tree leaves next to uphill rather than downhill road lanes. The lead content of the leaf particulates was associated only with sub-micrometre, combustion-derived spherical particles. These results indicate that vehicle exhaust emissions, rather than resuspended soil dust, or tyre, brake or other vehicle wear, are the major source of the lead, iron and magnetic loadings on roadside tree leaves. Analysis of leaves at different heights showed that leaf particulate lead and iron concentrations are highest at ~ 0.3 m (i.e. small child height) and at 1.5-2 m (adult head height) above ground level; monitoring station collectors placed at 3 m height thus significantly underestimate kerbside, near-surface lead concentrations. These results indicate that vulnerable groups, especially young children, continue to be exposed to ultrafine, lead-and iron-rich, vehicle-derived particulates.