The determinations of inorganic elements in nano, submicron and micron airborne particulates in Taiwan area

Abstract

This study proposed a novel method for determining inorganic elements in nano (0.030~0.108μm), submicron (0.108~1.000μm) and micron (1.000~9.970μm) airborne particulates collected by electrical low pressure impactor (ELPI) using laser ablation- inductively coupled plasma-mass spectrometry (LA-ICP-MS). Different grid laser patterns have been performed to completely ablate the airborne particulates collected on the filter. It was found that a 213nm laser with 100% laser energy and 1.5mm defocus distance, at 10Hz repetition rate and 8 seconds dwell time can ablate the real sample spots appropriately. Laboratory-made standard filter samples were prepared by dropping liquid standard solution on the filter to simulate samples collected by ELPI. The limits of detection ranged from 0.002ng for Cd to 1.062 ng for Si. The mean relative standard deviation (RSD) for five replicates of standard filter ranged from 3 to 18%. The proposed analytical method was applied to determine elemental concentrations of nano, submicron, and micron particles collected from the surrounding of Central Taiwan Science Park (CTSP). Total of 19 major and minor elements, including Na, Mg, Al, Si, K, Ca, Fe, Ti, V, Cr, Mn, Ni, Cu, Zn, As, Sr, Cd, Ba and Pb were determined in this work. The results showed that nearby CTSP was possibly responsible for As and Si in fine particles (＜1μm). High contents of K and Zn in fine particles were strongly associated with the emission from incinerator. The Pb contents in fine particles were mainly from road traffic, while the Cr, V, Mn, Ni, Cu and Cd in fine particles might be emitted from the traditional industries. Otherwise, to understand the chemical composition of suspended particles generated by rocket firecrackers or fireworks, a case study during Yanshuei Fireworks was also performed by the proposed method. The elemental concentrations in aerosol samples (0.03~9.97μm) collected by ELPI after the fireworks were about 1.9~20 times higher than those of normal days. Comparison of particle mass size distributions for each analyte element showed that the concentrations of K, V, Cr, Mn, Cu, Zn, As, Sr, Cd, Ba and Pb increased significantly in the submicron size range after the fireworks.