A risk assessment study of heavy metals in ambient air by WD-XRF spectrometry using aerosol-generated filter standards

A risk assessment study of the air quality in the surrounding of roads covered with slags coming from the non-ferrous metal industry was performed. A monitoring campaign was carried out at three locations in Flanders by collecting the PM10 fraction and the total suspended particulates (TSP) of the airborne dust particles, entrapping heavy metals, on membrane filters. The heavy metal concentration on the dust filters was determined by wavelength-dispersive x-ray fluorescence (WD-XRF) spectrometry. The XRF calibration curves were set up with filter standards prepared in the laboratory using an aerosol-generated loading system. The acquired WD-XRF results were confirmed by inductively coupled plasma atomic emission spectrometric (ICP-AES) measurements after acid digestion on a selected number of filters. Electron probe microanalysis (EPMA) confirmed that aerosol-loaded filter standards and dust filters with a concentration level of the analyzed element below 3300 ng cm(-2) were homogeneously distributed. Dust filters with higher concentrations, and especially filters loaded with the TSP fraction, reflected an inhomogeneous distribution of the analyzed element on the filter. The WD-XRF analytical results acquired in the monitoring campaign revealed that the concentration of Pb on the dust filters never exceeded the immission standard (yearly average) of 2000 ng m(-3). It can be stated that the impact on human health is limited and can still be reduced by covering the polluted roads with a layer of asphalt. Further evaluation of soil and water samples from the nearby surroundings reveals that the heavy metal content in the slags makes an important contribution to environmental pollution, especially the contamination of groundwater. Copyright (C) 2003 John Wiley Sons, Ltd.