Trace Metal Composition of Ambient PM2.5 and PM10 and Their Spatiotemporal Variation Near a Major Highway in an Alpine Valley in Switzerland

Abstract

PP-31-147 Background/Aims: We have conducted a pediatric asthma panel study in a community located in an Alpine valley in Switzerland to examine highway exhaust exposure and its effects on respiratory health. One of our objectives is to examine the spatial and seasonal distribution of ambient particulate matter (PM) and NOx, and thereby develop spatial models for residential outdoor PM exposure. This paper focuses on the trace metal composition and their spatiotemporal distribution in the Alpine valley in Switzerland. Methods: Two fixed (one near highway and the other background) and 4 other mobile locations were monitored for daily PM10, particle number concentrations, and NOx in Erstfeld, Switzerland during November 2007–June 2009. The mobile locations measured for 1 month each in the 4 seasons. In addition, 2-week integrated measurements of PM10, PM2.5, and NO2 were also obtained outside 9 children's homes in 3 different seasons. PM filters were analyzed for elemental and organic carbon using TOR-IMPROVE protocol and 48 trace metals using XRF. Results: Mean daily total metal levels (± Standard Deviation) were 3.2 ± 2.7 μg/m3 for a total of 547 daily measurements, which were about 21% of the average PM10 levels. The impact of local biomass combustion (with K as tracer) is consistently higher in winter, regardless of sampling locations. The dominant contribution of highway exhaust and break wear (Cu, Zn, Sb, Ba) is observed at the nearest location (55 m away) from the highway. Contrary to PM mass, which is significantly elevated in winter, crustal and resuspended road dust components (Al, Si, Ca) are observed higher in summer both in home outdoor PM10 and PM2.5 samples. Significant impact of road salt (Na, Cl) use in winter is also noticed in PM10 (but not in PM2.5) samples. Conclusion: These first results indicate significant contribution of highway traffic and local biomass burning on the PM exposure in the community.