Table 3 Changes to 24-h mean particle concentrations associated with variation in the gasoline‐ethanol fuel mix

From: Reduced ultrafine particle levels in São Paulo’s atmosphere during shifts from gasoline to ethanol use

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

  1. 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
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