Mobility assessment and validation of toxic elements in tunnel dust samples--subway and road using sequential chemical extraction and ICP-OES/GF AAS measurements.

The modified BCR three step sequential extraction procedure has been applied to homogenized urban dust samples collected in sedimentation chambers of two Prague tunnels (road, Letna, subway, and station Museum), and to SRM 1648 urban particulate matter (NIST) to validate the applicability of the procedure. Analyte concentrations in the fourth step were calculated from the total content of analytes determined and verified before, in case of the SRM 1648 certified values have been utilized. Concentrations of chosen elements As, Cd, Cr, Mn, Ni, Pb, Zn (Cu, Fe) in each fraction were measured by ICP-OES and GF AAS (arsenic determination) methods. The work has been focused on (i) levels investigation of toxic elements in dust samples and their distribution following a three-stage sequential extraction procedure, (ii) finding differences between two tunnel samples utilizing the estimation of mobility of trace elements, some macro-component comparisons and main mineralogical phases determinations by XRD analysis, (iii) validation of the proposed procedure using SRM 1648 Urban Particulate Matter (NIST) and comparative data obtained by a capillary electrophoresis (CE) method.