Concentration distributions of dissolved Sb(III) and Sb(V) species in size-classified inhalable airborne particulate matter

In order to obtain more accurate assessments of global contamination by potentially toxic antimony (Sb) and the toxicological effects of Sb on ecosystems, speciation analysis of inorganic Sb species in size-classified airborne particulate matter (APM) was performed. Thirteen fractions of size-classified APM (with aerodynamic diameters: D-p < 0.06, 0.06-0.12, 0.12-0.20, 0.20-0.30, 0.30-0.50, 0.50-0.70, 0.70-1.2, 1.2-2.1, 2.1-3.6, 3.6-5.2, 5.2-7.9, 7.9-11, and >11 mu m) were collected on a filter by using a multistage cascade impactor sampler. Speciation analysis of inorganic Sb(III) and Sb(V) was performed by using HPLC-ICP-MS. Portions of sample-loaded filters were sonicated with 30 mmol l(-1) citric acid under purified N-2 in order to avoid the oxidation of Sb(III) to Sb(V) during the extraction process. Sb(III) and Sb(V) were separated on a PRP-X100 anion exchange column using a mixture of 10 mmol l(-1) EDTA and 1 mmol l(-1) phthalic acid (pH 4.5) as a mobile phase, and they were subsequently detected by ICP-MS. The size distributions of the total Sb concentration exhibit a bimodal profile in which peaks corresponded to fine (0.50-0.70 mu m) and coarse (3.6-5.2 mu m) fractions. The speciation analysis demonstrated for the first time that Sb(III), which is the more toxic form, is dominated by coarse fractions whereas Sb(V) is distributed in both the fine and coarse fractions. The presented high-resolution size distributions of inorganic Sb species will provide helpful information in discussing both health risks by inhalation exposure to Sb and the extent of the effects of emission sources by atmospheric circulation.