Characterization of trace metals from different particle sizes, sources and contamination identifications for a mixed site in Taiwan

Abstract

Ambient air particulates (PM1, PM2,5, PM10, PM18, and total suspended particulates (TSP)), trace metals (Al, As, Cr, Cu, Cd, Zn, Ni, Pb, Mn, and Hg(p)) their concentrations, their dry deposition, and their sources from Dec. 2017 to May 2018 at Luliao Taichung City Junior High School (24°14′37.9″N 120°34′00.3″E) were studied. The site is a mixed site that is surrounded by traffic, and urban and commercial activities. The sources of ambient air particulates were identified by back-trajectories analysis. The trace metal concentrations in PM1, PM2.5, and PM10 were compared with those in other countries in the years 2003–2018. The level of contamination by these trace metals at this mixed site was evaluated using a contamination factor (CF) and degree of contamination (CD). The results indicated that the average concentrations of all particles were highest in January (winter season) and the average concentrations of TSP, PM18, PM10, PM2.5, and PM1 followed the order Jan. 2018 > Dec. 2017 > Apr. 2018 > Mar. 2018. The concentration of trace metals followed the order Al > Cu > Fe > Cr > Mn > Ni > As > Pb > Zn > Cd > Hg(p) in both TSP and dry deposits. Al had the highest mean concentration in PM18, PM10, PM2.5, and PM1 while Hg(p) had the lowest concentration in PM18, PM10, PM2.5, and PM1. Interestingly, elements As and Cr had higher mean concentrations in PM1 at the studied site than in the other countries of interest during the years from 2003 to 2018. C F and C D values for all trace metals revealed low degree of contamination at this mixed sampling site. The C D values for all trace metals in particle of sizes 1 to 18 μm all exceeded those calculated for TSP and dry deposits. The C D values increased with particle size from 1 μm to 18 μm.