Assessment of metal concentrations in atmospheric particles from Burnaby Lake, British Columbia, Canada

Trace metals were assessed in atmospheric particulates at Burnaby Lake, in the greater Vancouver area of British Columbia to assess concentrations, pa rticle size distributions and deposition rates to an urban watershed. Week- long samples were collected over a period of 18 weeks in 1995 using a 13 st age low pressure impactor (LPI). Samples were analysed using inductively co upled plasma atomic emission spectroscopy (ICP). Aluminum, boron, calcium, iron, magnesium, manganese, sodium and strontium had a similar time series pattern and particle size distribution. For these metals, maximum concentra tions occurred during weeks of low precipitation and exhibited a large peak in mid June. Their particle size distribution was mostly dominated by a la rge peak between 1.7-18.4 mum with a secondary peak at < 0.08 mum. Metal co ncentrations were generally one to three orders of magnitude higher than th ose measured in a rural location 100 km away from Burnaby Lake but similar to those measured in urban Taipei, Taiwan. Concentrations of the highly tox ic metals, arsenic, cadmium and lead were within current air quality guidel ines, however boron exceeded the Ontario Ministry of Environment ambient ai r quality standard in two of the 16 samples. Deposition velocities ranged b etween 0.22 and 13 cm s(-1) with the largest values corresponding to the co arse particle mode. Mean deposition rates ranged between 4.0 mug m(-2) d(-1 ) and 650 mg m(-2) d(-1). Depending on the metal, yearly loadings to the wa tershed ranged from 90 kg to several thousand tonnes. Calcium, aluminum, bo ron and magnesium had the highest metal loadings to the watershed. Manganes e also had relatively high loadings, a reflection of the high traffic densi ty in the area. The relatively high metal deposition rates indicate that me tal contribution from atmospheric sources may represent a significant porti on of the total metal load to the Burnaby Lake watershed. Crown Copyright ( C) 2001 Published by Elsevier Science Ltd. All rights reserved.