Concentration and composition variations of metals in the outdoor PM10 of elementary schools during river dust episodes

Aeolian river dust can seriously affect the air quality in central Taiwan. The main purpose of this study was to assess the concentration variations of PM₁₀ and metals at different elementary schools during river dust episodes. River dust samples were taken from eight sites in the main bare soil areas of the Choshui River. PM₁₀ aerosols from four elementary schools in Yulin County were collected by means of high-volume samplers. Fifteen elements (Fe, Al, Ca, Mg, Mn, Zn, Ti, Ni, V, Cr, As, Pb, Cu, Co, and Cd) in the river dust and PM₁₀ were analyzed in this study. The coefficients of divergence (CDs) were obtained by comparing the metal compositions in PM₁₀ aerosols at the four schools on the sampling days with the mean metal contents in the river soil samples as reference. The CD values showed that metal compositions in the aerosols at high-exposure sites during river dust episodes were similar to those compositions in the river dust. The concentrations of PM₁₀ at the high-exposure schools during river dust episodes were much higher than those during non-river-dust episodes. This study also indicated that at the high-exposure sites, both the PM₁₀ and metal concentrations were higher than at the low-exposure and control sites, not only during the river dust episodes, but also after the river dust episodes. The concentrations of toxic metals (Ni, Cr, As, and Cd) at the high-exposure sites were about 11.3 times higher during the river dust episodes (189 ng/m³) than during non-river-dust episodes (16.7 ng/m³) and about 8.9 times higher during the same periods at the control site (21.3 ng/m³).