Concentration and source origin of lanthanoids in the Canadian atmospheric particulate matter: a case study

摘要

Ambient PM_2.5 and PM_2.5–10 samples collected at selected urban and rural sites within the Canadian National Air Pollution Surveillance (NAPS) PM_2.5 Speciation Program were analyzed for lanthanoids and other elements. The average concentrations of total lanthanoids (calculated as sum of concentrations of all elements) in PM_2.5 ranged from 0.059 to 0.334 ng m−3. These concentrations were two times lower than in PM_2.5–10 samples and generally lower than values reported for industrial and urban areas around the world. The highest concentrations of lanthanoids were found in PM_2.5 samples collected at the Halifax NS site, located near a petroleum refining complex. In addition, La/Ce and La/Sm ratios at this site were significantly higher than their natural values. Increased La–enrichment factors were also found in Wallaceburg ON, which is located in a rural area, about 50 km downwind of two major petrochemical complexes. The results of this study demonstrate that La–enrichment factors are reliable tracers of emissions from oil refining industry.