ASSESSMENT OF LONG-TERM SPATIAL VARIATION OF HEAVY METALS AND POLYCYCLIC AROMATIC HYDROCARBONS IN URBAN AREAS OF BASEL

Abstract

Background:Most existing studies relied on measurements of particulate chemical constituents such as metals and polycyclic aromatic hydrocarbons (PAHs) at a few locations only. Assessment of long-term spatial variation of exposure to these hazardous air pollutants (HAP) within urban area thus poses a primary challenge. This study presents a new cost-effective and maintenance-free approach to monitor HAPs using moss as biomonitors. Aims: Primary aims were to assess the within-city spatial variation of heavy metals and PAHs and their determinants in Basel and compare them against corresponding standard gravimetric PM10 (particulate matter mass <10mm diameter) based methods. Methods: We conducted 2-week as well as 2-month monitoring of heavy metals and PAHs using moss bags (Hylocomium splendens) at 20 residential outdoor locations in Basel in spring and summer 2011. Concurrently, PM10 was also measured at the same locations. Collected moss and PM10 samples were analyzed for 13 heavy metals and 12 PAHs (>4-ring) using standard ICP-SFMS and GC-MS methods, respectively. Comparisons between seasons, different exposure windows and the two methods are made. Univariate as well as multivariate linear regressions are performed to find the determinants of spatial variation of these HAPs. Results: Long-term moss samples (2-month) have an order of magnitude higher levels than biweekly samples for heavy metals (435+ 370 vs 58.1+37.9 micrg/kg moss) as well as PAHs (23.6+27.4 vs 4.9+2.2 micrg/kg moss); biweekly spring samples were higher than summer for most metals and PAHs. Sn, Sb, Mo, Ni showed a highly correlated cluster (R>0.95) implying their common origin from traffic sources. All PAHs and Sb, Ni and Mo are higher at traffic impacted sites than urban background sites. Comparison of these HAPs between moss and PM10 as well as their spatial determinants is currently underway. Conclusions: Our first results suggest traffic as the main driver of hazardous air pollutants’ variability in Basel.