Sources of fine organic aerosol. 4. Particulate abrasion products from leaf surfaces of urban plants

Abstract

Green and dead leaves from 62 plant species characteristic of the Los Angeles area were harvested and composited according to the actual leaf mass distribution for that area. To simulate leaf surface abrasion by the wind, the leaf composites were agitated in clean Teflon bags while a purified airstream flowed through. Fine particles (d_p ≤ 2 µm) shed from the leaf surfaces were extracted and analyzed using gas chromatography/mass spectrometry. Organic constituents including n-alkanes, n-alkanoic and n-alkenoic acids, n-alkanols, n-alkanals, terpenoid compounds, and trace amounts of PAH were identified and quantified. n-Alkanes showed similar concentrations in both dead and green leaf surface matter; mono-, sesqui-, and triterpenoids were depleted in dead leaf material while n-alkanoic acids were enriched in dead leaf abrasion products. It is shown that the higher molecular weight n-alkanes (C_(27)-C_(33)), with their pronounced odd/even carbon number predominance, provide a suitable marker compound assemblage for tracing vegetative detritus in the urban atmosphere.