Availability and Bioaccessibility of Metals in Fine Particles of Some Urban Soils F. Madrid Æ M. Biasioli Æ F. Ajmone-Marsan Received: 27 July 2007 / Accepted: 5 November 2007 / Published online: 5 December 2007 Ó Springer Science+Business Media, LLC 2007 Abstract Metals in urban soils might be transferred to humans via ingestion, dermal contact, or breathing, espe- cially to children due to the ‘‘hand to mouth’’ activity during outdoor activities in playground and recreational areas. This involuntary soil ingestion depends on soil adherence to skin; it is known that the adhesion process tends to exclude particles greater than 50 lm, so the fraction below this diameter would be the most dangerous for health. The aim of this work was to study the ‘‘avail- ability’’, estimated by the EDTA extraction, and ‘‘oral bioaccessibility’’, estimated by the Simple Bioaccessibility Extraction Test (SBET), of several metals in urban soils of two European cities (Sevilla and Torino), as related to the soil particle size distribution. Torino and Sevilla showed different levels of metal contents, availability, and bioac- cessibility. In Torino, the finer particles showed metal enrichment of Cu, Zn, and, to a lesser extent, Pb, whereas in Sevilla, all of the studied metals showed this enrichment compared to the whole soils. The whole soil cannot be used as a good general indicator of the bioaccessibility of metals in the finest fractions of the soil. Metal availability was higher in the clay fraction ( \ 2 lm) than in other fractions or whole soils in both cities, and principal component analysis shows that availability is especially due to this fraction. In contrast, Cu and Pb bioaccessibility in the clay fraction seems to be slightly lower than, or comparable to, all of the other fractions and the whole soil. Bioaccessi- bility of Cr and Ni is clearly greater in the coarser fractions of Sevilla than those of Torino, despite the considerably greater total contents of both metals in the latter city. Adsorbed metal forms are assumed to be preferentially responsible for metals released by EDTA. A different ori- gin is attributed to bioaccessible metal forms. Anthropic influence seems more important in determining metal availability and bioaccessibility in urban soils of both cities than the different geological or industrial characteristics. Keywords Urban soils Á EDTA extraction Á SBET extraction Á Fine particles Introduction The interest in the characteristics of urban soils has increased greatly in the last two decades, and soils of cities all over the world have been studied. Some examples are Sevilla, Spain (Madrid et al. 2002, 2004), Torino, Italy (Biasioli et al. 2006, 2007), New Orleans, Louisiana, USA (Mielke et al. 1999), Beijing, China (Chen et al. 2005), Gaborone, Bostwana (Zhai et al. 2003), Sydney, Australia (Walter et al. 2005), and so forth. A review has been recently published (Wong et al. 2006) focusing on the uniqueness of urban environments. Urban soil properties are influenced by anthropogenic activities, and several kinds of pollutant are present in the soils of inner-city areas at higher concentrations than they are usually found in outer parts of the city or rural areas (Biasioli et al. 2006; Mielke et al. 1983)—for example, metals, polycyclic aro- matic hydrocarbons (PAHs), chlororganic compounds, and radionuclides. The sources of these pollutants are daily F. Madrid (&) Instituto de Recursos Naturales y Agrobiologı ´a de Sevilla (CSIC), Apartado 1052, Sevilla 41080, Spain e-mail: fmadrid@irnase.csic.es M. Biasioli Á F. Ajmone-Marsan DI.VA.P.R.A., Chimica Agraria, Universita ` di Torino, Via Leonardo da Vinci, 44, 10095 Grugliasco, Torino, Italy 123 Arch Environ Contam Toxicol (2008) 55:21–32 DOI 10.1007/s00244-007-9086-1