Anthropogenic platinum group element (Pt, Pd and Rh) concentrations in road dusts and roadside soils from Perth, Western Australia

The emission of platinum group elements (PGE) from automobile catalytic converters has led to rapid increases in Pt, Pd and Rh concentrations in roadside media. This article represents the first detailed study to assess PGE levels in road dusts and roadside soils in Australia. Road dust and roadside soil samples were analysed by ICP-MS following microwave digestion and cation exchange. All samples show elevation of PGE above average upper crust values, with maximum values of 420 ng g(-1) Pt, 440 ng g(-1) Pd and 91 ng g(-1) Rh. PGE ratios in road dusts and soils are consistent with known catalytic converter compositions and while Pt and Rh abundances are comparable with European studies, Pd levels are substantially higher in Australian samples. PGE in these samples are not correlated with Pb, though positive correlations with Ce, Cu and Y are evident. No straightforward relationship between traffic volume and PGE abundance is evident and factors such as driving style, topography, road drainage and potentially climate exert considerable influences.     

PGEs and other traffic-related elements in roadside soils from São Paulo, Brazil

The distribution of platinum, palladium, and rhodium in soils adjacent to a major road in S?o Paulo, Brazil, is presented. Sampling was made at four sites with varying traffic volumes and driving styles (stop/start vs. constant speed). High-resolution inductively coupled plasma mass spectrometry (HR-ICP-MS) with NiS fire assay collection and Te coprecipitation was used as analytical procedure. The platinum group element (PGE) pattern distribution in the analyzed roadside soil was similar to that of other traffic-related elements such as Zn and Cu, characterized by a strong decrease of the PGE content with increasing distance from the traffic lane. The results indicate that the PGE concentrations in roadside soil are directly influenced by traffic conditions and distance, which characterize their catalytic converter origin. Pt, Pd, and Rh contents range between 0.3 and 17 ng g(-1), 1.1 and 58 ng g(-1), and 0.07 and 8.2 ng g(-1) respectively. Lower levels of Pt and lower Pt/Pd ratios in relation to similar studies in other countries were observed due to the different Pt/Pd ratios in Brazilian automobile catalytic converters. This is the first study to assess traffic-derived Pt, Pd, and Rh deposition in Brazil.     

Platinum-group elements in sewage sludge and incinerator ash in the United Kingdom: Assessment of PGE sources and mobility in cities

Platinum-group element (PGE) concentrations in sewage sludge and incinerator ash compared with average PGE concentrations in road dust show a common pattern, characterized by a negative Rh anomaly. This similarity, found at 9 UK incinerators, suggests that there is a universal characteristic PGE pattern produced by common processes of dispersal of Pt, Pd and Rh derived from automobile catalytic converters.Ninety-one sewage sludge and incinerator ash samples from the sewage treatment facilities in Sheffield, Birmingham and 7 other UK cities were analyzed for PGE. The highest concentrations are 602 ppb Pt and 710 ppb Pd with lower maximum concentrations of 65 ppb Rh, 100 ppb Ru, 33 ppb Ir and 12 ppb Os. Ash from incinerated sewage was found to have higher PGE concentrations compared to the original sludge and the PGE ratios are preserved during incineration.Rh is more mobilized and dispersed than the other PGE as it is transported from roads into the drainage system and into sewage. Pt/Pd ratios of 1.0 in road dust and 0.9 in sewage and incinerator ash suggest that Pd is more mobile than Pt during dispersal. PGE abundances in stored incinerator ash of varying ages appear to have been affected by the variation in use of Pt, Pd and Rh in catalytic converters due to variation in their market prices.Concentrations of Os, Ir and Ru in ashes are greater in Sheffield and London than all the other city sites and may be derived from point industrial sources.     

Accumulating characteristics of platinum group elements (PGE) in urban environments, China

The three-way catalytic converters [mainly using platinum, palladium and rhodium of platinum group elements (PGE)] have been widely used to reduce the pollution arising from vehicular traffic. Since the late 1990s, the Chinese government has implemented measures for new vehicles, equipped with the three-way catalytic converters in metropolitan cities. However, the PGE spreading on environments has not been strongly concerned in developing countries. This study investigated the accumulation characteristics of PGE in urban environments in China. A few samples from India were also analyzed and compared with those from China. The collected soil, aerosol and plant samples were determined for PGE by inductively coupled plasma-mass spectrometry (ICP-MS) after nickel sulphide fire assay preconcentration. The results have shown higher PGE contents in the samples from the cities where vehicles were fitted with autocatalysts for longer time periods. The highest values are 160 ng/g for Pt, 107 ng/g for Pd and 34.5 ng/g for Rh in Hong Kong soils, whereas the lowest values are 2.59 ng/g for Pt, 1.31 ng/g for Pd and 0.40 ng/g for Rh in Kolkata soils. In Beijing and Guangzhou aerosol samples, the PGE concentrations are 6.22 to 24.3 pg/m³ for Pt and 1.16 to 8.60 pg/m³ for Rh and 7.68 to 12.2 pg/m³ for Pt and 2.15 to 5.15 pg/m³ for Rh, respectively. The levels of PGE abundances in the urban environments of China have been significantly elevated with increasing number of vehicles equipped with autocatalysts.     

Association of 210Po(210Pb), 239+240Pu and 241Am with different mineral fractions of a beach sand at Seascale, Cumbria, UK

Automotive catalytic converters, in which Pt, Pd and Rh (platinum-group elements; PGEs) are the active components for eliminating several noxious components from exhaust fumes, have become the main source of environmental urban pollution by PGEs. This work reports on the catalyst morphology through changes in catalyst surface by scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX) and laser-induced breakdown spectrometry (LIBS) from fresh to aged catalytic converters. The distribution of these elements in the fresh catalysts analysed (Pt-Pd-Rh gasoline catalyst) is not uniform and occurs mainly in a longitudinal direction. This heterogeneity seems to be greater for Pt and Pd. PGEs released by the catalysts, fresh and aged 30,000 km, were studied in parallel. Whole raw exhaust fumes from four catalysts of three different types were also examined. Two of these were gasoline catalysts (Pt-Pd Rh and Pd-Rh) and the other two were diesel catalysts (Pt). Samples were collected following the 91,441 EUDC driving cycle for light-duty vehicle testing. The results show that at 0 km the samples collected first have the highest content of particulate PGEs and although the general tendency is for the release to decrease with increasing number of samples taken, exceptions are frequent. At 30,000 km the released PGEs in gasoline and diesel catalysts decreased significantly. For fresh gasoline catalysts the mean of the total amount released was approximately 100, 250 and 50 ng km(-1) for Pt, Pd and Rh, respectively. In diesel catalysts the Pt release varied in the range 400-800 ng km-1. After ageing the catalysts up to 30,000 km, the gasoline catalysts released amounts of Pt between 6 and 8 ng km(-1), Pd between 12 and 16 ng km(-1) and Rh between 3 and 12 ng km(-1). In diesel catalysts the Pt release varied in the range 108-150 ng km(-1). The soluble portion of PGEs in the HNO3 collector solution represented less than 5% of the total amount for fresh catalysts. For 30,000 km the total amount of soluble PGEs released was similar or slightly higher than for 0 km.     

Dispersal and accumulation of Pt, Pd and Rh derived from a roundabout in Sheffield (UK): From stream to tidal estuary

The Coisley Hill roundabout, a typical urban source for PGE in stream sediments, has anomalously high values of up to 408 ppb Pt, 444 ppb Pd and 113 ppb Rh in road dust, up to 416 ppb Pt and 278 ppb Pd in gulley sediment and up to 606 ppb Pt and 1050 ppb Pd in verge soil. For samples collected at the same time, the road dust values are much higher than in sediments in the Shire Brook stream, that drains the roundabout, with values of 3-64 ppb Pt, 4-57 ppb Pd and up to 7 ppb Rh. Downstream sediments from rivers Rother and Don have lower values of 2-35 ppb Pt, 2-14 ppb Pd and up to 3 ppb Rh. The Humber estuary values are low with 6-8 ppb Pt, 5-8 ppb Pd and 1-2 ppb Rh. Pt/Pd increases down catchment with Coisley Hill 0.8, Shire Brook 1.0, Trent and Don 1.5 and the Humber estuary 2.0. Pt/Rh and Pd/Rh also increase downstream. Precious metals are generally dispersed away from their vehicle catalytic source and Pd is dispersed more than Pt and Rh but Pt and Pd are re-concentrated in acid mine drainage in the Shire Brook, with concentrations varying with stream flow. Pt and Pd values are slightly elevated at the tidal limit and in mud deposited when the river is in spate. On Coisley Hill, values of 133 ppb Pt and 230 ppb Pd occur in dust from a new road surface (two weeks old when sampled). These are similar to those on much older road surfaces suggesting that Pt and Pd collect and disperse rapidly from roads. Au is low in road dust and higher values in conurbations suggest the presence of more Au sources in urban rather than in rural areas. Au values are not diluted downstream as much as PGE suggesting different processes of dispersion and sedimentation.     

Bioaccumulation of palladium, platinum and rhodium from urban particulates and sediments by the freshwater isopod Asellus aquaticus.

The three-way catalytic converters introduced to oxidize and reduce gaseous automobile emissions represent a source of platinum group elements (PGEs), in particular platinum, palladium and rhodium, to the urban environment. Abrasion of automobile exhausts leads to an increase of the concentration of PGEs in environmental matrices such as vegetation, soil and water bodies. The bioaccumulation of Pd, Pt and Rh by the freshwater isopod Asellus aquaticus was studied in natural ecosystems and under laboratory conditions. Owing to the low concentration level (ng g(-1)) of PGEs in the animals studied. analyses were performed with a quadrupole inductively coupled plasma mass spectrometry (ICP-MS) and hafnium, copper, yttrium, rubidium, strontium and lead were monitored for spectral interference correction. Asellus aquaticus collected in an urban river showed a content (mean +/- s) of 155.4 +/- 73.4, 38.0 +/- 34.6, and 17.9 +/- 12.2 ng g(-1) (dry weight) for Pd, Pt and Rh, respectively. The exposure of Asellus aquaticus to PGE standard solutions for a period of 24h give bioaccumulation factors of Bf: 150, 85, and 7 for Pd, Pt and Rh, respectively. Exposure of Asellus aquaticus to environmental samples for different exposure periods demonstrated that PGE bioaccumulation is time dependent. and shows a higher accumulation for the materials with a higher PGE content. While all three elements have the same uptake rate for exposure to catalyst materials, for exposure to environmental materials they havc a different uptake rate which can be attributed to transformations of the PGE species in the environment.     

Autocatalyst-derived platinum, palladium and rhodium (PGE) in infiltration basin and wetland sediments receiving urban runoff

The emission of platinum group elements (PGE) from automobile catalytic converters has led to rapid increases in Pt, Pd and Rh concentrations in roadside media. Significant quantities of the PGE may enter and accumulate in fluvial systems via road runoff. This paper examines the occurrence and spatial distribution of autocatalyst-derived PGE in surface sediments of infiltration basin and wetland sediments receiving road-runoff in Perth, Western Australia. Samples were analysed by ICP-MS following microwave digestion and cation exchange. PGE concentrations ranged between 1.5-17.2 Rh, 5.4-61.2 Pd and 9.0-103.8 ng g(-1) Pt. The highest levels of PGE were generally found at basin topographic low points and these concentrations were found to be strongly related to the area of road surface drained and the traffic volume. PGE ratios in infiltration basin and wetland sediments were within the typical range of catalytic converter compositions. However, comparisons of PGE ratios between parent road dusts and infiltration basin sediments revealed a systematic shift in Pt/Pd ratios, suggesting that PGE fractionation can occur during transport through the drainage system and that a small portion of Pd in road dust may be solubilised under natural conditions.     

A further discussion of the factors controlling the distribution of Pt, Pd, Rh and Au in road dust, gullies, road sweeper and gully flusher sediment in the city of Sheffield, UK

Forty paired road dust and gully sediments from the city of Sheffield in NE England show that high platinum, palladium and rhodium concentrations derived from catalytic converters depend on proximity to both roundabouts rather than traffic lights and to topographic lows. Road dust outside schools and control samples, further away on the same road, show that Pt, Pd and Rh concentrations are dependant on passing traffic flow rather than numbers of stopping vehicles. Highest values of Pt + Pd in road dust are 852 ppb and 694 ppb in gullies. Rh has maximum values of 113 ppb in road dust and 49 ppb in gullies. Pt and Pd values of a few ppb to just over 100 ppb occur in road dust where traffic does not stop, on roads away from junctions. Pt, Pd, Rh and Au are all picked up by road sweepers and gully flushers both with maximum values of just over 100 ppb Pt and Pd. High Au values (maximum 610 ppb in a road dust) were located on pavements, in suburbs, outside schools and in road sweepers collecting in residential areas rather than on high traffic flow roads. Stratification of Pt and Pd in gullies was not observed whereas a high Au value was recorded at the bottom of a gully suggesting gravity concentration for Au. Anomalous Pd grades of 1050 ppb in road dust from a school entrance and 2040 ppb in a street sweeper sample were recorded. These high Pd- and Au-bearing samples do not have anomalous Pt or Rh values and may be sourced from jewellery or dental fillings. However, most samples have consistent Pt/Pd ratios of about 1 and Pt/Rh values of 4 to 5 indicating a catalytic converter source. Pt and Pd are concentrated in road dust at levels well above background in all the samples, including on high and low traffic flow roads.     

The distribution of automobile catalysts-cast platinum, palladium and rhodium in soils adjacent to roads and their uptake by grass

The introduction of automobile catalysts has raised environmental concern, as this pollution control technology is also an emission source for the platinum group elements (PGE). The main aim of this study was to assess the concentrations of Pt, Pd, Rh and Au in soil and grass herbage collected adjacent to 5 roads. Soil and grass samples were collected from 4 fixed distances (0, 1, 2 and 5 m) from the road edge at each site. PGE and Au were determined by ICP-MS in all samples after acid digestion. The maximum soil Pt, Rh and Pd concentrations were measured at the road perimeters. Averaged across the sites, the Pt and Rh concentrations of 15.9+/-7.5 microg Pt kg(-1) and 22.40+/-4.73 microg Rh kg(-1) at 0-m distance decreased to 2.04+/-1.7 microg Pt kg(-1) and 3.51+/-1.96 microg Rh kg(-1), respectively at 5-m away from the roads. Pd concentrations were much higher than Pt or Rh, ranging from 120.8+/-12.0 microg Pd kg(-1) (0-m) to 84.2+/-10.9 microg Pd kg(-1) (5-m), possibly due to differences in its use, emission and/or soil chemistry. Au showed little or no change with distance from the roads. However, the average Au concentration of 18.98+/-0.98 microg Au kg(-1) provides clear evidence of some input possibly due to attrition of automobile electronics. No straightforward influence of traffic flow rates on PGE distribution was found. A combination of dispersal impeding local features and slow moving and stop-and-start traffic conditions or fast moving traffic with flat open spaces may have offset the expected impacts. Rh and Pt soil concentration accounted for 66% and 34% (P<0.01) of the variability observed, respectively in their plant concentrations. Grass Pd and Au concentrations had no relationship with their respective soil concentrations.     

Increase of platinum group element concentrations in soils and airborne dust in an urban area in Germany

Since 1993, all new cars sold in the European Union had to be fitted with catalytic converters. Undoubtedly, these measures brought about a great progress concerning traffic emission controls. However, this technology also led to new emissions. A rapid accumulation of the catalytic active noble metals Pt, Pd, and Rh in the environment was observed and concern arose about potential environmental and health risks. This work aimed at a contribution to a monitoring of platinum group element (PGE) emission and accumulation by comparing analytical data, all generated in 1999 and in 2005 in an urban area in Germany. Oriented at the 1999 sampling strategy, soil and airborne dust samples were taken in 2005 at the same sampling sites located mainly close to heavily used roads in the region of Braunschweig. For the enrichment of the analytes, conditioned soil samples as well as loaded glass fiber filters from air sampling were transferred to the nickel sulphide fire assay. For analyses, the ICP-MS technique was applied. High Pt, Pd, and Rh concentrations were detected especially in top soil layers (0-2 cm) directly at the roadsides or on center strips. At one road outside the city, where traffic moved with a constant speed of about 80 km/h, maximum concentrations in soil were found to be 50.4 microg/kg for Pt, 43.3 microg/kg for Pd, and 10.7 microg/kg for Rh. PGE concentrations were the highest close to that road and exponentially declined with growing distance. At a second road, where vehicles run with a constant speed of 50 km/h, the highest concentrations were detected in the center strip soil: 88.9 microg/kg (Pt), 77.8 microg/kg (Pd), and 17.6 microg/kg (Rh). At a third crowded street in the centre of Braunschweig with stop and go traffic, the highest soil concentrations were determined, namely 261 microg/kg for Pt, 124 microg/kg for Pd and 38.9 microg/kg for Rh. The sampling of airborne dust at this roadside revealed for Pt 159 pg/m(3) air or 1730 microg/kg dust, for Pd 37.8 pg/m(3) air or 410 microg/kg dust, and for Rh 10.0 pg/m(3) air or 110 microg/kg dust. A comparison of analytical results of 2005 with those of 1999 revealed a distinct increase of PGE concentrations in soils closely along heavy traffic roads by a factor of 2.1 to 8.9; once even a factor of 15 was determined. The findings also document, that especially Pt and Rh concentrations were elevated in airborne dust.     

Bioaccumulation of platinum group elements and characterization of their species in Lolium multiflorum by size-exclusion chromatography coupled with ICP-MS

The bioaccumulation of Pt, Pd and Rh by grass grown hydroponically with nutrient solutions containing these ions at elevated (38.7 mg l(-1) Pt, 21.7 mg l(-1) Pd and 7.1 mg l(-1) Rh) and medium (3.6 mg l(-1) Pt, 4.4 mg l(-1) Pd and 0.5 mg l(-1) Rh) concentrations was studied by using inductively coupled plasma sector field mass spectrometry (ICP-SFMS). The highest bioaccumulation factors were obtained for Pd and Rh in roots and for Pt in leaves. The obtained results showed that most of the studied metals were accumulated in roots, and only a small fraction was really metabolised and transported to leaves. The multi-element capability of ICP-SFMS has been exploited to study the metabolism of platinum group elements (PGEs) in cultivated plants. The species of studied metals were extracted from roots and leaves and separated into two mass fractions by ultra-filtration. The low molecular mass (<10 kDa) fractions of the root and the leaf extracts were investigated by size-exclusion chromatography (SEC) coupled on-line to ICP-SFMS. The presence of Ca, Cu, S and C in the same fractions as Pt, Pd and Rh may indicate the interaction of PGEs with phytochelatins and carbohydrates.     

Platinum and rhodium distribution in airborne particulate matter and road dust

In this work the platinum and rhodium content in the atmosphere of Madrid was monitored for 1 year at seven different sites. Samples were taken with medium volume PM-10 collectors (< 10 microm) for 48 h and analysed by ICP-MS. The Pt and Rh content was dependent on the sampling site, ranging from < 0.1 to 57.1 and < 0.2 to 12.2 pg m(-3) with a medium value of 12.8 and 3.3 pg m(-3), respectively. These results show that the Pt and Rh content in airborne samples depends on the traffic density per day and also on medium driving speed. Road dust < 63 microm was analysed at the same time and at the same location. The Pt and Rh content at the six sites analysed was in the 31-2252 and 11-182 ng g(-1) range with an average of 317 and 74 ng g(-1), respectively. The average Pt/Rh ratio obtained was 4.3. similar to that obtained for airborne particles (4.0), and agrees with that of the more commonly used gasoline car catalyst [J.J. Mooney, Encyclopaedia of Chemical Technology (1996) 982]. Platinum distribution as a function of particle size in airborne particulate matter was also studied, by sampling with two high-volume sample collectors, a five-stage WRAC (from 10 to 65.3 microm and total) and a seven-stages PM-10) cascade impactor (from 9 to < 0.39 microm). Platinum is associated with a wide range of particle diameters. Due to the ultratrace level of Pt in airborne samples, its distribution in the atmosphere could not be considered as homogeneous. No trend could be established in Pt distribution in the different fractions, except that in most cases the highest value of Pt was obtained in the < 0.39-microm fraction. The Pt content was usually high in airborne samples when the Pb, Ce, Zr and Hf content was also high, thus confirming that the source of these pollutants is from traffic.     

Palladium and platinum concentration in soils from the Napoli metropolitan area,Italy: possible effects of catalytic exhausts

Soils from the Napoli metropolitan area (Italy) were evaluated for Pt and Pd concentrations. One hundred and ninety-five (195) samples were collected from residual soils and non-residual soils from flower-beds in a 120 km(2) area on a 0.5 km grid in the downtown-urbanized area and on 1 km grid in suburban zones. The soils <100 mesh size fraction (150 microm) was analyzed for Pt, Pd and 37 other elements by ICP-ES and ICP-MS after aqua regia digestion. Pt and Pd contents range between <2 and 52 microg/kg and between <10 and 110 microg/kg, respectively. A large number of samples from the metropolitan area were characterized by anomalous values for Pt (>6 microg/kg) and Pd (>17 microg/kg). Non-residual soils from flower-beds are located mainly in the urbanized downtown areas subject to heavy traffic and have higher Pt and Pd contents than residual soils from suburban areas. Geochemical maps show a strong correlation between roads with major traffic flow and high Pt and Pd concentrations. In addition, data from most of the downtown flower-beds fall within the three-way catalytic converters (TWC) field identified by [Ely JC, et al. Environ Sci Technol; 35:3816-3822]. This suggests that emissions of abraded fragments from vehicle exhausts may be the source of the high values and geographic distributions of Pd and especially Pt in urban soils of Napoli. Catalytic converters (Pt/Pd/Rh) have been mandatory for gasoline-powered vehicles in Europe since 1993. Italy permitted the use of non-catalytic motor until January, 2002. This is responsible for the high values for both Pt and Pd in the non-residual soils of the urban areas of Napoli.     

Distribution of platinum group elements and other traffic related elements among different plants along some highways in Germany

Using ICP-MS and ICP-AES platinum group elements (Pt, Pd, Rh, Ru and Ir) and Ce, La, Nd, Pb and Zr have been determined in street dust, Taraxacum officinale (dandelion), Plantago lanceolata (plantain), Lolium multiflorum (annual ryegrass), Rhytidiadelphus squarrosus (moss) and Vascellum pratense (mushrooms) collected along highways and streets in Germany during 1999. Among the plants Taraxacum officinale (dandelion) reflects most adequately the pollution with the investigated elements matching the results from street dust. A strong positive correlation between all elements determined in the plants is established. Transfer factor for Pt between soil and plants has been determined in an agricultural experiment ranging between 0.004 and 0.008 for two types of soils.     

A pilot study on the content and the release of Ni and other allergenic metals from cheap earrings available on the Italian market

The capability of alloys used in cheap jewellery to release metal ions on contact with the skin causing allergic contact dermatitis (ACD) is generally acknowledged. To reduce the diffusion of the Ni-induced ACD the Council Directive 94/27/EC [Council Directive 94/27/EC of 30 June 1994. Official Journal L 188, 22/07/1994, 1.] limited the total Ni content in alloys and its release rate in artificial sweat. In this work, three different aspects were explored: i) the frequency of skin sensitization to Ni-containing earrings in patients before and after the introduction of the Directive's limit; ii) metal composition of alloys by X-ray analysis; iii) metal leaching in artificial sweat followed by Sector Field Inductively Coupled Plasma Mass Spectrometry (SF-ICP-MS) quantification. Well-known allergenic metals, as Ni, Cr and Co, and possible emergent allergens, as Al, Ag, Au, Cd, Cu, Fe, Ir, Mn, Pb, Pd, Pt, Rh, Sn, V and Zn, were studied. Results showed that the frequency of allergy due to earrings did not decrease after the introduction of the Ni limit: in 1994 and in 2005 patients positive to Ni patch tests were 54.3% and 53.5%, respectively. The earring components analyzed were Fe-based or alloys of Cu/Zn or Fe/Cr/Ni, plated with a thin film of precious metal (Ag, Au) which, in several cases, was combined with a Ni layer beneath. Five out of 10 items were not in compliance with the Ni Directive 94/27/EC having a total Ni content >0.05%. In three cases the release of Ni concentrations was higher than the safe sensitizing limit given by the above mentioned Regulation (i.e., <0.5 microg/cm(2)/week). The release of Cu and Zn was very variable among the different pieces (Cu: 0.134-30.9 microg/cm(2)/week; Zn: 0.141-160 microg/cm(2)/week); two objects released high amounts of Fe (358 and 586 microg/cm(2)/week) and one released considerable Mn (21 microg/cm(2)/week). Lead was released from 70% of the objects, while Ag, Al, Cd, Co, Cr and Sn from ca. 30% of the items and concentrations of these elements were well below 0.5 microg/cm(2)/week. Vanadium was released by only one item whereas Au, Ir, Pd, Pt and Rh were never leached.     

The estimation of the bioavailabilities of platinum, palladium and rhodium in vehicle exhaust catalysts and road dusts using a physiologically based extraction test

Platinum group element (PGE) levels in the environment have increased following the introduction of vehicle exhaust catalysts (VECs). In order to evaluate the potential pathways of PGEs from VECs into humans, a physiologically based extraction test (PBET) was used to study the uptake of PGEs by the human digestive tract. The PBET assay was implemented in two phases, to first simulate the passage of ingested soil through the acid conditions of the stomach before it enters the near neutral conditions of the small intestine. The results showed that Pt, Pd and Rh did not undergo precipitation reaction when passing from the acid environment of the stomach to the neutral environment of the small intestine. The greatest fractions of bioavailable PGEs (up to 68%) were observed in road dust samples, possibly due to the presence of mobile PGE species formed in the roadside environment. Higher percentages of Pd and Rh were bioavailable than Pt, probably due to the differences in their mobilities and tendencies to form soluble complexes. Pt showed the highest absolute bioavailability however, due to its greater concentration in environmental samples. The solubilization of PGEs in the human digestive tract could involve the formation of PGE-chloride complexes, with perhaps increased health-hazard issues because of the known toxic and allergenic effects of these species.     

Platinum and palladium variations through the urban environment: evidence from 11 sample types from Sheffield, UK

Platinum (Pt) and Palladium (Pd) concentrations have been analysed in 194 samples from within the city of Sheffield in the UK. The samples were taken from road dust, gully pots (also known as drains), soils, a motorway drainage pipe, rivers, lakes, sewage sludge, incinerator ash, incinerator ash in landfill, street cleansers and gully cleansers. The introduction of Pt- and Pd-bearing automobile catalysts, has been cited as the cause of a rise in the concentration of urban Pt and Pd accumulations. Geochemical analyses for the different sample types are used here to show how the Pt and Pd accumulate in different urban environments as they are transported from their catalytic source. Initially Pt and Pd collect in road dust and gully pots at values of up to 450 ppb although most analyses for both elements are around 100 ppb. The four roadside soils analysed, have a great range in values, the highest with a value of over 600 ppb Pt and 1000 ppb Pd. Then the fate of the Pt and Pd is either to be removed by gully flushers and road sweepers (which contain around half the concentration of that in road dust) or to be washed from the roads, through the gully pots, into either the river or urban drainage systems. Due to the addition of terrestrial sediments, river samples contain much reduced values of Pt and Pd, at approximately an order of magnitude lower than in road dust. Similarly, sewage sludge contains Pt and Pd values which are lower than road dust. However, the Pt and Pd analyses are much higher in incinerated sewage (with many samples over 150 ppb for both metals), probably due to the loss of the mass of other material during the incineration process. Weathered incinerator ash in landfill has lower values of Pt and Pd than fresh ash from the incinerator. Although the range in values of Pt and Pd is similar for road dust and gully pot sediments their modal values tell a different story. The mode for Pt is very similar for both road dust and gully pot sediments, at around 100 ppb, whereas there is a drop of 50 ppb in the mode for Pd in the gully pots (from 80 ppb to around 40 ppb). Given that gully pot sediment is derived from road dust, it is suggested that in gully pots, Pd is preferentially mobilized over Pt. Furthermore, a comparison of the modal values of Pt and Pd in river sediments suggests that this process continues into the natural drainage system of the city.     

Monitoring Pt and Rh in urban aerosols from Buenos Aires, Argentina

Vehicular traffic is the main source of platinum group elements (PGEs) in highly populated urban areas like Buenos Aires where a traffic density of 1,500,000 vehicles day(-1) (corresponding to 7,500 vehicles km(-2)) is estimated. Since there is no information on the levels of PGEs in Buenos Aires, a pilot study was undertaken to ascertain the amount of two major PGEs, namely Pt and Rh, in the atmosphere of this city. To this end, 49 samples of PM-10 particulate matter were collected during 7 days in seven representative sampling sites located downtown Buenos Aires and spread over an area of about 30 km(2). The collection of particulate matter was performed on ash-free glass-fiber filters using high volume samplers with PM-10 sampling heads. Filters loaded with the particulate matter were subjected to microwave (MW)-assisted acid digestion using a combination of HNO(3), HF and HClO(4). The resulting solutions were evaporated and then diluted with 0.1 mol l(-1) HCl. Analyses were performed by sector field inductively coupled plasma-mass spectrometry (SF-ICP-MS) and special attention was paid to the control of mass interferences. Statistical analysis was performed on the experimental data obtained for the element concentrations taking also into account local meteorological data for the monitored period. The highest concentrations of Pt and Rh were detected at two sites (Hospital Alemán and Casa Rapallini) located in streets with traffic consisting mostly of passenger cars. The Pt content (in pg m(-3)) in airborne particulate matter was found to vary from 2.3 to 47.7, with a mean value of 12.9+/-7, and that of Rh from 0.3 to 16.8, with a mean value of 3.9+/-2.8. These concentrations are by far below the levels for which adverse health effects might be expected to occur, i.e., around 100 ng m(-3). On the other hand, monitoring of PGEs should be carried out in a systematic fashion to detect possible dramatic increases from today's levels.     

Evaluation of the health risk of platinum group metals emitted from automotive catalytic converters

A health risk assessment of platinum (Pt) emitted from automotive catalytic converters is presented. Following a stepwise approach, the relevant literature is discussed in order to characterize Pt emissions as well as the toxic potential of Pt and its compounds. In an exposure assessment, ambient Pt concentrations in air are predicted to range from approximately 4 pg/m3 (street canyon, typical conditions) up to approximately 112 pg/m3 (express motorway, severe conditions). These values agree well with the few measured concentrations, which are also in the low pg/m3 range. Pt is emitted from catalytic converters in very small amounts (ng/km range), mainly in the (0)-oxidation state (elemental Pt). The nanocrystalline Pt particles are attached to microm-sized aluminum oxide particles. Whether free ultrafine Pt particles may be emitted and result in biological effects has not been studied sufficiently. Hence, risk assessment can only be based on the respiratory sensitizing potential of halogenated Pt salts. The presence of such compounds in automotive Pt emissions cannot definitely be excluded. From recent occupational studies conducted in catalytic converter production, a conservative no-effect level (NOEL) of 1.5 ng/m3 can be derived for the sensitizing effect of halogenated Pt salts. In a (reasonable) worst case approach, it is assumed that such compounds comprise 1% (0.1%) of the total Pt emissions. Applying a safety factor of 10 to account for interindividual variability, a guidance value of 15 (150) ng/m3 is derived for catalyst-borne Pt. The exposure to Pt in ambient air as measured or predicted is at least two orders of magnitude below this guidance range. Rhodium is also contained in automotive catalysts, palladium has increasingly substituted Pt, and iridium-based catalysts have recently been introduced. Although the database on these platinum group metals is rather small, there is no evidence that they pose a health risk to the general population.