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<strong>Transactions</strong> of the VŠB - Technical university of OstravaSafety Engineering SeriesVol. VI, No. 2, 2011p. 17 - 26SCREENING OF PLATINUM GROUP METALS FROM AUTOMOBILECATALYSTS IN SOILS OF OSTRAVA CITYLucie SIKOROVÁ 1 , Marcela ŠUCMANOVÁ 2 , Pavel DANIHELKA 3Research articleAbstract:Key words:Automobile catalysts are sources of platinum group metals (PGM) emissions into theenvironment. Since their introduction, the increase of PGM concentrations in differentenvironmental matrices has been observed. This, together with the information abouttoxicity of Pt, Pd and Rh, raises concerns about possible health risks. To obtain input dataon potential exposure to PGM, soil sampling methodology was developed and screeningof PGM in soils was provided in the city of Ostrava at locations with different trafficload, including sites with potential exposure of children. The screening indicates that inimmediate proximity to high traffic, increased Pt, Pd and Rh concentrations are observed.Soil contamination, Platinum group metals, Automobile catalysts, Ostrava.IntroductionIn the Czech Republic, automobile catalysts withplatinum group metals (PGM) were introduced asa compulsory component of every new passengercar due to stricter emission limits EURO in 1993. In2009, the number of vehicles equipped with catalystscomprised around 4 million of the total 6 millioncars, with passenger cars and vans representing 90 %of all vehicles equipped with catalysts (CDV, 2010).An automobile catalyst is a unit installed intothe exhaust system of a car to reduce the productionof gaseous pollutants, such as carbon monoxide,hydrocarbons and nitrogen oxides, by theirtransformation into harmless components - carbondioxide, water vapor, and nitrogen gas. The exhaustgases purification takes place as a consequence ofoxidation-reduction reactions, which are facilitatedby the combination of heat with the platinum metals- platinum (Pt), palladium (Pd) and rhodium (Rh)- contained in this device. (Bliefert, 1994; AECC,2011).Currently, three way catalysts (TWCs) are mostlyused (see Fig. 1). TWCs consist of a steel or ceramiccarrier with a honeycomb structure, which is coatedwith a highly porous layer, the so called washcoat,made of aluminium oxide, which is resistant to hightemperatures and to repeated temperature changes aswell. A catalytic layer, consisting of finely dispersedplatinum metals, is fixed on the washcoat surface.(Bliefert, 1994; AECC, 2011).Fig. 1 Automobile catalyst (BOSAL CR, 2009)There is no dispute that the application ofautomobile catalysts has an enormous contributionto environmental protection. However, the catalystspresent the main source of environmental pollutionby platinum metals. During the car operation, thecatalyst surface is chemically and physically stressedby fast changing oxidative-reductive conditions,high temperature and mechanical abrasion, thus,producing the emission of PGM primarily tothe air with consequent contamination of otherenvironmental matrices (Ravindra et al., 2004).Apart from automobile catalysts, additionalmajor uses of PGM are in the glass, chemical,electrical, electronics and petroleum industries,the manufacture of jewelry, in medicine as cancertreatment drugs, and in dentistry as alloys. However,automobile catalysts are considered the mostimportant source of environmental burden by PGM.(Ravindra et al., 2004; Wiseman and Zereini, 2009).1VŠB - Technical University of Ostrava, Faculty of Safety Engineering and Energy Research Center, Ostrava,Czech Republic, lucie.sikorova@vsb.cz2TraceLab, spol. s. r. o., Kroměříž, Czech Republic, TraceLab@seznam.cz3VŠB - Technical University of Ostrava, Faculty of Safety Engineering, Ostrava, Czech Republic, pavel.danihelka@vsb.cz17
<strong>Transactions</strong> of the VŠB - Technical university of OstravaSafety Engineering SeriesVol. VI, No. 2, 2011p. 17 - 26Platinum group elements are released by catalyststogether with exhaust gases mostly in the formof finely dispersed metal nanoparticles adsorbedon larger aluminium dioxide particles from the“washcoat” with emission rates of ng.km -1 (König etal., 1992; Moldovan et al. 1999; Artelt et al., 1999;Palacios et al., 2000; Moldovan et al., 2002). Theamount and rate of PGM emission depend on manyfactors, such as driving conditions (i.e. the speed ofa car, and the exhaust gases temperature), the type ofthe engine, the type and age of the catalyst (Artelt etal., 1999; Moldovan et al., 2002).Great attention has been paid to the researchof accumulation and distribution of PGM in theenvironment during the last 10 years. Many studies(e.g. Zereini et al., 2001; Cinti et al., 2002; Gómezet al., 2002; Leśniewska et al., 2004; Pan et al.,2009) have pointed out the significant increase ofthese precious metals in various environmentalcompartments. Cinti et al. (2002), for example,recorded 6-fold enhancement in the Pt levels ofsoil in 2001 in comparison with 1992. Zereini et al.(2001) observed an enhancement in the Pt and Pdlevels in air over a 10-year period - Pt concentrationshave increased 46-times and concentrations of Pdwere 27-fold higher in 1998 than in 1988. Withrespect to the monitoring of PGM accumulationduring the automobile catalyst usage, soil is themost commonly monitored matrice. A review ofselected studies focused on PGM determinationin soils is presented in Tab. 1. A comparison ofresults obtained in presented studies is not possibledue to different locations, sampling conditions andanalytical methods. However, following conclusionscan be deduced:• At sites exposed to traffic, PGM concentrationsexceed the natural background levels,• PGM concentrations decrease with the increasingdistance from the road and with the increasingdepth of sampling,• PGM concentrations are in a strong correlationwith traffic intensities.The increase of PGM concentrations inthe environment raises concerns over possiblehealth risks. Platinum metals, especially solublePt compounds, are well known from workingenvironment as substances with the ability to causesensitization (Marhold, 1980; Nordberg et al., 2007).Certain Pt compounds exhibit toxic, carcinogenicand mutagenic effects (Nordberg et al., 2007).Metallic Pd is a dermal sensitizer causing contactdermatitis (Kielhorn et al., 2002). Since there isa little knowledge in the area of transformation,behavior, speciation and bioavailability of PGM inthe environment and living organisms, it is difficultto make any conclusions with regard to health risksfrom environmental exposure to these metals. Thus,substances with uncertain hazards are released intothe environment.A review of recent knowledge with regard to theissue of environmental burden by the platinum groupmetals from transportation and related health riskswas discussed in detail in Chemické listy journal(Sikorová et al., 2011).A screening of PGM concentrations in soils iscurrently provided in the area of Ostrava city. Theattention is focused on urban sites with traffic loadand on urban sites with traffic load and the presenceof child population. The reason why sites withchildren are considered is that child population isat high risk of exposure to harmful substances fromcontaminated soils (SZÚ, 2000 - 2007).The aims of this contribution are to present a soilsampling methodology to determine platinum metalsfrom automobile catalysts in the area of Ostrava cityincluding the partial results, and to discuss someproblematic aspects of environmental monitoring ofthese ultratrace elements.Materials and methodsSampling sitesSampling sites were divided into three groups -sites with traffic load and the presence of children,locations with traffic load and without the presenceof children, and finally sampling sites without trafficload and with the presence of children, so calledbackground sites.Kindergarten playgrounds, sports grounds andother playgrounds in residential areas and parks(their lists are not maintained) were considered siteswith traffic load and the presence of child population.Lists of kindergartens and sports grounds andcartograms of traffic load from 2009 were obtainedfrom the Ostrava City Authority. Traffic intensitiesgained from the cartograms were supplementedwith nation-wide traffic census data from 2011.Kindergartens and sports grounds were reflected to anOstrava city map with a road and motorway networkin the program ArcGIS. For a field reconnaissance,kindergartens and sports grounds up to 200 m awayfrom roads with traffic intensities ≥ 5 001 vehiclesper day (vpd) were chosen - see Fig. 2. In total, 30kindergartens and 18 sports grounds were selected.During field reconnaissance, other playgrounds inresidential areas and parks were seeked out.18
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