Road traffic has been highlighted as a major source of metal emissions in urban areas. Brake linings and tires are known emission sources of particulate matter to air; the aim of the current study was to follow the development of metal emissions from these sources over the period 1995/ 1998-2005, and to compare the emitted metal quantities to other metal emission sources. Stockholm, Sweden was chosen as a study site. The calculations were based on material metal concentrations, traffic volume, particle emission factors, and vehicle sales figures. The results for metal emissions from brake linings/tire tread rubber in 2005 were as follows: Cd 0.061/0.47 kg/year, Cu 3800/5.3 kg/year, Pb 35/3.7 kg/year, Sb 710/0.54 kg/year, and Zn 1000/4200 kg/ year. The calculated Cu and Zn emissions from brake linings were unchanged in 2005 compared to 1998, indicating that brake linings still remain one of the main emission sources for these metals. Further, brake linings are a source of antimony. In contrast, Pb and Cd emissions have decreased to one tenth compared to 1998. The results also showed that tires still are one of the main sources of Zn and Cd emissions in the city.

The increased awareness of traffic as a major diffuse metal emission source emphasizes the need for more detailed information on the various traffic-related sources and how and where the metals are dispersed. In this study, metal emission patterns in the road traffic environment were examined from the perspective of different surrounding factors, e.g. the importance of intersections, deceleration, vehicle speed and traffic density. A total of 148 topsoil samples from 18 south Swedish roads were analysed (using GFAAS) for traffic-emitted metals, i.e. Cd, Cr, Cu, Ni, Pb, Sb and Zn. The roadside topsoil metal concentrations were used to examine correlations between metals and surrounding factors. The studied metals were divided into three groups corresponding to different emission sources: metals from decelerating activities (Cu, Sb and Zn), metals as historical residues from the combustion of petrol (Pb and Cd), and non-source-specific metals (Cr and Ni). It was found that Cu and Sb, despite their rather short history as traffic-emitted metals, have increased more than eightfold in roadside soils compared to background levels. The major source of road traffic related Cu and Sb is brake linings. The significant increase of Cu and Sb in roadside topsoil stresses the need for metal transport studies as well as effect studies of these metals. Metals emitted due to decelerating activities were not correlated to elevated concentrations near road junctions. Emission patterns of traffic-related metals alongside roads are crucial in order to be able to evaluate the optimal localization of storm water treatment ponds.

Today there is consensus concerning the road traffic's role as a metal source. However, there are so far only a few studies which focus on the road side immission patterns regarding distance from roads, and especially in combination with the leachability of heavy metals down the soil profile. In this study, the aim was to analyse concentrations of traffic related metals in road side soils, at different depths and distances from roads, both to analyse the immission patterns as well as to explain the importance of the road construction design of the road side terrain. The BCR sequential extraction procedure was performed to be able to address the environmental risk in terms of metal mobility. Approximately 80 soil samples were analysed for seven metals; antimony (Sb), cadmium (Cd), copper (Cu), chromium (Cr), lead (Pb), nickel (Ni) and zinc (Zn). The results showed that, depending on metal, the total metal concentrations in road side soils have increased 3-16 times compared to regional background during the last decades. Each metal had a limited dispersal distance from the roads as well as down in the soil profile and the road construction significantly affected the metal immission distance. Elevated metal concentrations were mostly found for top soils and down to 10 cm in the soil profiles. The labile fractions counted for more than 40% of the total concentrations for Cd, Cu, Ni, Pb and Zn, indicating a potential mobilization of the metals if the road side soils become disturbed. The present soil metal concentration levels are not alarming, but metals with a high accumulation rate might gradually be an upcoming problem if nothing is done to their emission sources.

Environmental context. Reliable results of chemical analysis are crucial for a proper environmental risk assessment. The recovery of antimony concentrations in environmentally relevant samples is here shown to be most dependent on the extraction method chosen. A reported low antimony concentration in present or historical samples may be misleading for decision-makers. Abstract. Antimony is found in elevated concentrations in the roadside environment, industrial sites and generally in urban areas. An extended use of multielement analysis has produced more concentration data for metals in the environment. However, volatilisation of elements in the digestion step may be a problem as some of the certified and recommended digestion methods are performed in open vessels. The aim of the current study was to focus on wet digestion-derived problems for the analysis of volatile elements, with specific reference to Sb. Both soils and products, namely tyres and brake linings, were sampled. The samples were digested using different methods with variations in temperature, acid mix, and the use of open or closed vessels. For some methods, the recovery was <10%, indicating a need for revision of certified and recommended digestion procedures. For a multielement analysis, a closed vessel method must be used. If the aim is to study only Sb, a wet-digestion method optimised for Sb is the natural choice. This may be valuable to consider when handling environmentally relevant samples such as soils contaminated with Sb from point or diffuse sources.

Environmental context. The global production and use of antimony (Sb) increase together with stocks and emissions, but there are gaps in our knowledge concerning environmental effects. Here, a reconstruction of major Sb flows in an urban area was conducted. The major emission source of Sb identified was wear of brake linings, although other sources may also be of importance, e.g. diffuse emission of flame-retarded goods. Abstract. The present study sets out to analyse the urban metal sources of Sb, by estimating the stock of Sb in use, and to present related flows and emissions in Stockholm, Sweden, in 2005. Antimony was studied with the main methodology of substance flow analysis with existing data, while chemical analysis was used as a complement. No large point sources were found reported to the authorities; hence, the dominating source for Sb is diffuse and originates from goods. The total Sb stock in Stockholm in 2005 was ~430 000 kg (range 110 000–1 700 000 kg) and the total Sb inflow was estimated at 45 000 kg year–1 (range 30 000–67 000 kg). The stock was dominated by flame-retarded goods, cable shielding, glass and accumulators. The Sb emission was estimated at ~720 kg year–1 (range 430–1200 kg year–1). Despite large uncertainties and missing data, the results supported the notion of the importance of brake linings as a source of Sb emissions (710 kg year–1), whereas other goods such as textiles (4.5 kg year–1), tyres (1.4 kg year–1), sinkers, ammunition and polyethylene terephthalate (PET) bottles and packaging were minor sources. However, flame-retarded goods are still poorly quantified and are seen as a potential emission source.