Dust, Measurement of Trace Elements in
Authors: Barratt Rod 
Published: September 2006

Dust is a source of contamination of land, water and the atmosphere, and is of special concern owing to its trace metal content. There is a significant body of literature describing the use of deposited dusts as indicators of environmental pollution, particularly by trace metals. While several authors have identified the need for standardized guidelines on sampling techniques and on analytical procedures, few have addressed the problems in sufficient depth to produce such guidelines. Since some of the early papers on this topic, more is known about the chemical nature of dusts and the association of certain metals with components of the matrix. This information provides useful guidance on analytical techniques and methods for dissolution of samples.

In the analysis of trace elements in dusts, a prerequisite is to prepare a solution for analysis. A variety of methods have been used to digest dust samples for determination of trace metals, and this can make it difficult to compare the results from different studies. Whether total or available metal content is determined is just one uncertainty needing resolution. Time requirements range from 15 min to 24 h, and this is another variability that may make results incomparable, while the great amounts of acids and long digestion times may result in contamination. For over 20 years, microwave ovens have found increasing use and have been used to digest various kinds of samples, such as rocks, sediments, ores, soils, coal, fly ash, water, sludge and biological and botanical samples. This article describes the efficiency of various acids for the digestion of dust, both by traditional methods and using a microwave oven. The latter technique offers an advantageous route for the digestion of dust samples in preparation for trace metal analysis. Speed and good recovery coupled with less risk of contamination through the limited amounts of reagents required combine to make this an excellent choice in the suite of techniques for environmental analysis.

General reviews of analytical methods demonstrate the dominance of atomic absorption methods for the analysis of trace metals such as lead and cadmium in a variety of samples. This pattern is generally found for work on metals in dusts, with flame atomic absorption predominating for Pb, Cd, Zn, Ni and Cu. Other techniques have included neutron activation (NA) and inductively coupled plasma atomic emission spectroscopy (ICPAES). Polarography in the form of differential‐pulse anodic stripping voltammetry (DPASV) is suitable for the simultaneous determination of trace quantities of Pb and Cd in dust. The method gives good reproducibility and has the added advantages of being relatively cheap, quick and simple. Interferences and means for overcoming their effects will be outlined. The aim of analysis of dusts is to represent environmental quality. This necessitates appropriate presentation of the data from the analysis, and some issues relating to this will be outlined.

Dusts will always present a potential route of contamination by trace metals and organic substances and the need for future work in this area will not diminish. Only by the application of good quality control, the use of reference materials and reliable techniques and an understanding of the significance of the results can confidence be placed in a useful approach to environmental quality assessment.