Chemical Fractionation in Environmental Studies of Potentially Toxic Particulate-Bound Elements in Urban Air: A Critical Review

Abstract

In recent years, studies of heavy metal air pollution have increasingly gone beyond determining total concentrations of individual toxic metals. Chemical fractionation of potentially toxic elements in airborne particles is becoming an important part of these studies. This review covers the articles that have been published over the last three decades. Attention was paid to the issue of atmospheric aerosol sampling, sample pretreatment, sequential extraction schemes and conditions of individual extractions. Geochemical forms of metals occurring in the air in urban areas were considered in detail. Based on the data sets from chemical fractionation of particulate matter samples by three sequential extraction procedures (SEPs)-Fernández Espinosa, BCR and Chester's-the compilation of the chemical distribution patterns of As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn was prepared. The human health risk posed by these toxic and/or carcinogenic elements via inhalation of atmospheric particles was estimated for two categories of polluted urban areas: the commonly encountered pollution level and the high pollution level.

Keywords: PM; chemical fractionation; ecological risk; heavy metals; inhalation health risk; potentially toxic elements; sequential extraction; trace elements; urban air.

Figure 1

Sequential extraction procedures used for chemical fractionation of potentially toxic elements in airborne particles.

Figure 2

Analytical techniques used for the determination of metallic and metalloid elements in digests and extract solutions of APM samples.

Figure 3

Average operational speciation of selected PTEs in the urban air worldwide.

Figure 4

Comparison of the average operational speciation of cadmium and zinc in atmospheric particulate matter.

Figure 5

Mean proportion of water-soluble fractions of PTEs in the urban air classified as follows: CEPL—commonly encountered pollution level; HPL—high pollution level.