Partitioning of heavy metals over different chemical fraction in street dust of Murcia (Spain) as a basis for risk assessment

Dust samples were collected from urban, suburban, industrial, highways, and natural sites from the vicinity of Murcia City, Spain. Chemical and physical properties were determined as well as the partitioning of the heavy metals Cu, Pb, Zn and Cd over exchangeable pools, association with carbonates, oxides, organic complexes and a residual phase. The results showed differences in the concentrations and percentages of the metals extracted from the five chemical phases among the dusts studied. These were attributed to the sources of metals, total metal concentration, dust physical and chemical properties, and the specific affinity of some metals for some solid phases. Metal distribution in the different phases was found to depend on each land use. Pb found to mainly reside in the residual phase from natural area; while Pb was mainly bound to Fe and Mn oxides in industrial dust. In dust from the urban and industrial sites Cu was equally distributed over Fe and Mn oxides and the residual phase, while in highway dust it mainly resided in the organic fraction. Zn mainly resided in the residual phase in dust from the urban and natural site, while in dust from the suburban site a large proportion of Zn was bound to Fe and Mn oxides. Cd was mainly associated to Fe and Mn oxides in dust from the urban site. Zn was the most mobile metal; Cu was the least mobile metal, while Cd and Pb showed medium risks of being mobilized. (C) 2014 Elsevier B. V. All rights reserved.