Supplementary Information:
Air pollutant mapping with a mobile laboratory
during the BEE-TEX field study
by
Tara I. Yacovitch, Scott C. Herndon, Joseph R. Roscioli, Cody Floerchinger, W. Berk
Knighton, Charles E. Kolb
Most Likely Concentrations
In Table S1 below, a summary of the most likely concentrations of benzene, 1,3butadiene, NO2, toluene, styrene and C2-benzenes (xylenes + ethylbenzene) are reported.
The data is presented as a function of wind direction: results for all data in a given
neighborhood are contrasted with filtered data for only northerly and southerly winds
(All, N, S). Colored bars are overlaid on top of the data and represent the relative
concentrations of each species. The most populated histogram bin (max) is shown beside
the peak of a fit to the entire distribution assuming normally distributed variances,
formally a Gaussian function. The resulting Gaussian width (Gauss Sigma) is also
tabulated. The average of N and S winds is taken, and the resulting Gaussian sigma is
calculated with the formula s = s N2 + s S2 .
Also shown in Table S1 are 1,3-butadiene averages from three sampling sites from
the Texas Commission on Environmental Quality’s (TCEQ) automated gas
chromatograph (GC) network.1 The locations of these sites are shown in the expanded
map of the study region, Figure S1. The GC data is 1 hour data and covers the duration
02/01/2015 to 02/21/2015. Reported values are simple averages and standard deviations.
S1
Table S1. Most likely concentrations of various hazardous air pollutants by neighborhood and
wind direction.
Chemical
Neighborhood Wind Dir
Max
Gauss Peak
Benzene
Manchester
Manchester
Manchester
Harrisburg
Harrisburg
Harrisburg
Galena Park
Galena Park
Galena Park
Clinton Drive a.
Milby Parka.
Ceasar Chavez a.
Manchester
Manchester
Manchester
Harrisburg
Harrisburg
Harrisburg
Galena Park
Galena Park
Galena Park
Clinton Drive a.
Milby Parka.
Ceasar Chavez a.
Manchester
Manchester
Manchester
Harrisburg
Harrisburg
Harrisburg
Galena Park
Galena Park
Galena Park
Manchester
Manchester
Manchester
Harrisburg
Harrisburg
Harrisburg
Galena Park
Galena Park
Galena Park
Clinton Drive a.
Milby Parka.
Ceasar Chavez a.
0.4
0.4
0.2
0.3
0.2
0.3
0.4
0.9
0.45
0.39
0.41
0.33
0.32
0.27
0.39
0.69
0.84
0.71
0.34
0.38
0.34
0.18
0.17
0.18
0.07
0.04
0.11
0.11
0.17
0.10
0.18
0.34
0.49
24.9
26.6
23.2
23.0
21.8
22.4
20.1
28.6
20.1
0.52
0.60
0.48
0.82
0.94
0.60
0.49
0.84
0.48
0.62
0.80
0.66
1,3-butadiene
NO2
Toluene
All
N
S
All
N
S
All
N
S
All
All
All
All
N
S
All
N
S
All
N
S
All
All
All
All
N
S
All
N
S
All
N
S
All
N
S
All
N
S
All
N
S
All
All
All
0.2
0.2
0.2
0.1
0
0.1
0.1
0.1
0.1
26
28
22
24
22
24
18
22
18
0.4
0.6
0.3
0.5
0.5
0.6
0.6
0.9
0.6
Gauss
Sigma
0.17
0.14
0.22
0.12
0.10
0.11
0.53
0.53
0.57
0.42
0.76
0.31
0.10
0.11
0.11
0.08
0.05
0.06
0.10
0.10
0.10
0.52
0.58
1.35
5.7
4.2
8.0
3.5
2.7
2.2
5.3
6.5
5.9
0.20
0.22
0.33
0.47
0.66
0.21
0.29
0.43
0.29
1.00
3.50
1.10
Average of
N and S
0.37
Resulting
Sigma
0.26
0.33
0.15
0.78
0.78
0.17
0.15
0.07
0.08
0.13
0.14
24.93
9.05
22.09
3.45
24.32
8.79
0.54
0.39
0.77
0.69
0.66
0.52
S2
Styrene
C2-benzenes
(xylenes +
ethylbenzene)
Manchester
Manchester
Manchester
Harrisburg
Harrisburg
Harrisburg
Galena Park
Galena Park
Galena Park
Clinton Drive a.
Milby Parka.
Ceasar Chavez a.
Manchester
Manchester
Manchester
Harrisburg
Harrisburg
Harrisburg
Galena Park
Galena Park
Galena Park
Clinton Drive a.
Milby Parka.
Ceasar Chavez a.
All
N
S
All
N
S
All
N
S
All
All
All
All
N
S
All
N
S
All
N
S
All
All
All
0.2
0.2
0.3
0.1
0.1
0.1
0.1
0.2
0.1
0.5
0.6
0.2
0.4
0.7
0.5
0.3
0.7
0.3
0.21
0.16
0.26
0.13
0.13
0.20
0.09
0.16
0.08
0.10
0.17
0.07
0.54
0.64
0.41
0.82
1.14
0.64
0.25
0.73
0.33
0.44
0.61
0.49
0.06
0.07
0.09
0.06
0.05
0.13
0.08
0.09
0.07
0.20
0.48
0.09
0.22
0.18
0.33
0.45
0.96
0.30
0.14
0.37
0.28
0.69
2.10
0.72
0.21
0.12
0.16
0.14
0.12
0.11
0.52
0.37
0.89
1.01
0.53
0.47
a. TCEQ Automatic Gas Chromatographic Sampling Site
S3
Figure S1. Map of the study area. The sampling frequency in each neighborhood is shown as a
color map, with areas with 300 or more data points shown in yellow. Areas with less than 25 data
points are not colored. Blue triangles indicate the position of TCEQ AutoGC locations. White
squares correspond to inventory sources of 1,3-butadiene; white triangles correspond to inventory
sources of benzene.
Representativeness of Data
In Figure S2, the number of data points used in the neighborhood data are shown as a
function of date or time of day. The time wave was geographically binned in 80m x 80m
bins, by neighborhood. Instead of averaging, a histogram of the number of data points vs.
date or time of day was made for each geographic bin. The sum of all histograms in a
given neighborhood was then computed, and plotted.
S4
Figure S2. Histogram plots of the number of data points used in the neighborhood most likely
concentrations as a function of date and time of day. Data from north and south winds (orange
and red bars) are computed separated. Grey shaded areas indicate weekdays. Blue shaded areas
show the relative solar elevation angle in order to show the hours of sunlight.
In the previous section, neighborhood most likely concentrations are tabulated. In
reading this data, it is important to note that data in the Manchester neighborhood is
significantly more representative of the timescale of the study than data in either the
Harrisburg or Galena Park neighborhoods. The Galena Park neighborhood in particular
was visited mostly on 02/03/2015 and 02/20/2015. Weekdays are shaded in grey.
Figure S2 also shows a similar analysis for the proportion of data acquired in 2-hour
increments over the course of 24 hour days. Times are indicated in UTC, and the local
time is UTC – 6 hrs (so 18:00 UTC = noon local). These time-of-day figures show that
the majority of data was collected during daylight hours. The Manchester neighborhood
has data throughout the night, the Harrisburg neighborhood has no overnight
measurements, and the Galena Park neighborhood has some nighttime data.
S5
Temperature is another meteorological parameter of interest because of its potential
to affect tank-flashing emissions. Figure S3 Shows that average temperature of the
binned data indeed varies across the map. This is due to the specific dates and times of
sampling in those specific areas. Overall, south wind data occurred at warmer ambient
temperatures than north wind data. Comparing these temperature maps against the
concentration maps in the following sections does not show a positive correlation. In
other words, for this data set, and within these temperature ranges, increased temperature
does not lead to increased average concentrations. Ambient water concentration varied
between 0.4% and 2% over the course of the campaign, generally following temperature
trends.
Figure S3: Histogram plots of ambient temperature (left) as a function of wind direction. Color
plots show the distribution of temperature over the study region as a function of wind direction.
S6
Concentration Maps
In the maps that follow, the histograms used to determine the most likely
concentration (Gaussian Peak) from Table S1 are shown alongside color maps over each
neighborhood. The concentration maps have bin sizes of 80m x 80m, reflecting the
approximate north-south width of a neighborhood block in Manchester. In order for an
average to be conserved for a given geographic bin, a minimum of 25 data points must be
present. A color map of the bin counts is included (lower right) in order to better
represent the variations in sampling frequency across the neighborhoods. Areas of the
map shown in yellow have 300 or more sample points.
In lieu of taking a simple average of all geographic bins, the frequency of a given
concentration bin is computed (inset histograms, red bars). These 1D histograms then
allow for the determination of the most likely concentration over the neighborhood
region. In order to capture instances of very high concentrations, a single blue bar shows
the accumulated probability of observing any concentrations larger than this bin location.
For most histograms, this concentration is 0.
Two dominant wind directions were present in the Houston ship channel during the
period in question: Northerly and Southerly. These two wind vectors sample entirely
different emission sources, and so the geographic binning was performed after filtering
the 1 Hz measured wind data for both north and south winds. Wind roses show the
dominant wind directions and speeds for the displayed data. The radius of each polar
segment indicates a probability, in intervals of 0.1, while the colors indicate wind speed
bins: red (0-2 m/s), green (2-4 m/s), blue (4-6 m/s) and yellow (6-8 m/s).
S7
Figure S4. Benzene concentration map (North winds)
S8
Figure S5. Benzene concentration map (South winds)
S9
Figure S6. 1,3-Butadiene concentration map (North winds)
S10
Figure S7. 1,3-Butadiene map (South winds)
S11
Figure S8. NO2 map (North winds)
S12
Figure S9. NO2 map (South winds)
S13
Figure S10. Toluene map (North winds)
S14
Figure S11. Toluene map (South winds)
S15
Figure S12. Styrene map (North winds)
S16
Figure S13. Styrene map (South winds)
S17
Figure S14. C2-Benzene map (North winds)
S18
Figure S15. C2-Benzene map (South winds)
S19
High Concentration Events
Figure S16 shows a polar plot of 1,3-butadiene concentration from the Manchester
neighborhood. Two distinct rays of enhanced concentration are observed: at 165 degrees
and again at 20-45 degrees.
Figure S16. 1,3-Butadiene polar plots for the Manchester neighborhood. Geographically binned
1,3-butadiene concentrations are plotted radially (ppb) as a function of binned wind angle
(degrees compass) for the entire campaign. Wind speed is shown as a color scale, with black
denoting 0 m/s, yellow at 4 m/s and above, and all other colors intermediate.
Comparing the direction of the 165 degree ray to Figure 1 of the main paper, we see
that it points at the 1,3-butadiene inventory sources from the Goodyear/TPC plant. The
ray from the northern quadrant points towards the Valero refinery, which directly abuts
the neighborhood. The Valero refinery also notes 1,3-butadiene sources in its reporting
(TCEQ 2006 Special Hourly Inventory2).
S20
References
1.
2.
Texas Commission on Environmental Quality. AutoGC Data by Day by
Parameter. 2015; Hourly Averages. Available at: http://www.tceq.state.tx.us/cgibin/compliance/monops/agc_daily_average.pl. Accessed Aug 25, 2015.
Jolly J. Written Communication: TCEQ 2006 Special Hourly Inventory. Point
sources from facilities included in the 8 county HGB non-attainment area ed.
Houston, TX: Texas Comission on Environmental Quality; 2011.
S21