Hopanoid hydrocarbons in PM 10 from road tunnels in São Paulo, Brazil

Abstract

The fleet of flexible fuel vehicles in Brazil is the largest in the world. To diagnose the contribution of vehicle emissions to atmospheric particulate matter, organic molecular markers, such as hopanes, can be used. However, nothing is known about the particulate matter mass fractions of these tracers in environments exclusively impacted by road emissions. In this study, the hopanoid composition of PM₁₀ inside two tunnels in the São Paulo metropolitan area with very distinct circulating fleets (Jânio Quadros (JQ) and Rodoanel (RA)) was obtained. Higher mean concentrations (82.4 ng m⁻³) and PM₁₀ mass fractions (239 ng mg⁻¹) were obtained in RA, in which the fleet is composed of both light and heavy duty vehicles. The most abundant species were 17α(H),21β(H)-30-norhopane (27.9 ng mg⁻¹ in JQ, 47.9 ng mg⁻¹ in RA) and 17α(H),21β(H)-hopane (32.6 ng mg⁻¹ in JQ, 44.3 ng mg⁻¹ in RA). Diverse concentration ratios were calculated and compared with those of other sources. Overlapping values may preclude the use of these parameters as source assignment tools. Some compounds, such as 18α(H)-22,29,30-trisnorneohopane, 17α(H)-22,29,30-trisnorhopane, 17α(H),21β(H)-30-norhopane, 18α(H)-30-norneohopane, 17α(H),21β(H)-hopane, 17α(H),21β(H)-22S-homohopane and 17α(H),21β(H)-22R-homohopane, were found to be very good predictors of the total concentrations of hopanoids.

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