Table 3.
Changes to 24-h mean particle concentrations associated with variation in the gasoline‐ethanol fuel mix
| Column number: | (1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) |
| Dependent variable: | Nucleation | Aitken | Accumulation | BC | PM2.5 | |||||
| Unit: | dN/dlogDp, cm−3 | dN/dlogDp, cm−3 | dN/dlogDp, cm−3 | µg m−3 | µg m−3 | |||||
| Mean over hour window: | 24-h | 24-h | 24-h | 24-h | 24-h | |||||
| Sample period: | Oct/2010 to | Oct/2010 to | Oct/2010 to | Oct/2010 to | Nov/2008 to | |||||
| May/2011 | May/2011 | May/2011 | Apr/2011 and Oct to Nov/2012 | May/2013 | ||||||
| Number of sampling sites: | 1 | 1 | 1 | 1 | 3 | |||||
| Source: | Own | Own | Own | Own | CETESB | |||||
| Estimation: | 2-step model | 2SLS model | 2-step model | 2SLS model | 2-step model | 2SLS model | 2-step model | 2SLS model | 2-step model | 2SLS model |
| Flex fuel share of Gasoline E20/E25 rises from 30 to 80% | 2,794 ± 1,456 | 2,783 ± 1,433 | 332 ± 818 | 361 ± 818 | 565 ± 785 | 553 ± 806 | 1.1 ± 1.3 | 1.0 ± 1.2 | 0.2 ± 3.9 | −0.2 ± 2.9 |
| Equivalently, share of Ethanol E100 falls from 70 to 20% | ||||||||||
| Control variables (to correct for the influence of other determinants of particles) | ||||||||||
| Site-specific linear trend | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| Quarter-of-year fixed effects | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | – | – |
| Week-of-year fixed effects | – | – | – | – | – | – | – | – | Yes | Yes |
| Day-of-week fixed effects | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| Radiation (+100 W m−2) | −234 ± 664 | −235 ± 607 | 110 ± 386 | 111 ± 361 | 108 ± 259 | 108 ± 226 | 0.0 ± 0.3 | 0.0 ± 0.2 | −0.4 ± 2.2 | −0.3 ± 1.3 |
| Temperature (+1 oC) | −499 ± 234 | −498 ± 211 | −61 ± 119 | −63 ± 105 | 32 ± 100 | 32 ± 91 | 0.1 ± 0.1 | 0.1 ± 0.1 | 1.2 ± 0.5 | 1.2 ± 0.4 |
| Humidity (+10%) | −1,454 ± 699 | −1,453 ± 543 | −715 ± 384 | −718 ± 322 | −97 ± 265 | −96 ± 243 | −0.4 ± 0.2 | −0.4 ± 0.2 | −1.0 ± 1.6 | −1.0 ± 1.2 |
| Wind speed (+1 m s−1) | −569 ± 1,144 | −567 ± 1,046 | −1,910 ± 686 | −1,913 ± 593 | −485 ± 449 | −484 ± 389 | −1.6 ± 0.6 | −1.6 ± 0.5 | −6.5 ± 2.8 | −6.5 ± 2 |
| Other meteorolog. and road traffic conditions (see notes) | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| R 2 | 57.3% | 57.3% | 51.5% | 51.5% | 54.5% | 54.5% | 74.1% | 74.1% | 73.4% | 73.4% |
| Number of observations | 198 | 198 | 198 | 198 | 198 | 198 | 228 | 228 | 511 | 511 |
| Number of regressors | 30 | 30 | 30 | 30 | 30 | 30 | 29 | 29 | 74 | 74 |
| Mean value of dependent variable | 8,755 | 8,755 | 3,320 | 3,320 | 1,494 | 1,494 | 3.3 | 3.3 | 13.8 | 13.8 |
Coefficients and 95% confidence intervals, i.e., point estimate ± 2 standard errors. An observation is a date (columns 1–8) or a date-site pair (columns 9–10). Samples exclude the colder months of June to September and include all days of the week. Radiation, temperature, humidity, and wind speed in the recorded unit. All columns additionally include several wind direction, precipitation, thermal inversion and road traffic congestion indicators. Since the longer sample encompasses 2010, columns 9–10 include site-specific intercepts indicating the opening of the Greater São Paulo beltway’s southern section on March 31, 2010. The effect of raising the gasoline share in the flex fleet is scaled for in-sample variation from 30 to 80%. The corresponding variation in the ethanol share is one minus variation in the gasoline share. Ordinary Least Squares estimates in the odd-numbered columns, with standard errors calculated by bootstrapping (200 samples each): (i) the consumer-level fuel choice data, to account for sampling variation in the predicted gasoline share in a first-step consumer demand model, and (ii) the pollutant-meterology-traffic data in the second-step particle regression, clustering by date. Two-Stage Least Squares estimates in the even-numbered columns, with the median ethanol-to-gasoline price ratio across pumping stations instrumenting for the predicted gasoline share in the particle regression equation