Antimony derived from brake linings in roadside soils, road run-off, and affected streams

• Applicant: Professor Dr. Tim Mansfeldt
• Subject Area: Hydrogeology, Hydrology, Limnology, Urban Water Management, Water Chemistry, Integrated Water Resources Management ; Soil Sciences ; Physical Geography
• Term: from 2015 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 270959057

Antimony (Sb) and its compounds are considered as a pollutant of high priority interest by national and international environmental authorities (e.g., WHO, US E.P.A., Council of the European Communities) as they have carcinogenic potential. Nevertheless, this semimetal is added to friction material in brake linings and released into the environment due to abrasion during the braking process. The objectives of this proposal are (i) to yield detailed information about the spatial distribution patterns of total Sb in thoroughly characterized roadside soils, and (ii) to provide an improved understanding of Sb's mobility and speciation (tri- versus pentavalent Sb) and its spatial distribution patterns in those. Besides the determination of total Sb by microwave digestion using strong mineral acids, a sequential extraction procedure will be applied to assess the mobility and bioavailability of Sb. The procedure includes the determination of the weak acid-soluble, reducible, oxidizable, and residual fractions. To determine Sb(III) and Sb(V), a reliable quantitative extraction of Sb from the sample matrix must be applied without any degradation or transformation of its species, but still with representative extraction efficiency. We will apply and adjust already tested extraction methods to a wider range and variation of soil samples in order to develop a less matrix-dependent procedure. Moreover, the (iii) speciation and size fractionation of Sb in road run-off, and (iv) the effects of discharged road run-off on the speciation and size fractionation of Sb in a drainage stream will be investigated. Variations in water quality parameter such as pH, ionic strength, redox potential, temperature, and dissolved oxygen have an influence on metal speciation in aquatic systems. We will study these effects by conducting speciation and size fractionation in both road run-offs during rain events, and long-term variations in a drainage system downstream of an outlet of road run-off. Size fractionation will provide more information about binding forms of Sb in aquatic systems. It is known that Sb mainly remains in the low molecular mass (LMM) fraction. This is of great concern, as LMM species are believed to be more bioavailable than particle-associated species. Nevertheless, both analytical approaches have never been conducted in roadside run-off and its affected drainage system. All these objectives share a common purpose: to provide a better understanding of how brake-lining-derived Sb is present in roadside soils and related drainage systems. Distribution of Sb species in environmental samples is crucial for the evaluation of toxic effects, since Sb toxicity depends on its oxidation state.

• DFG Programme: Research Grants