An exploratory study of air emissions associated with shale gas development and production in the Barnett Shale

Figures & data

Figure 1. Sampled locations in DFW Metroplex.

Table 1. Equipment and zones of influence

			Equipment within 61 m of Sampling Site				Equipment within 610 m of Sampling Site				Equipment within 1.6 km of Sampling Site
County	Site	Times Sampled	No. of Wells	No. of Tanks	No. of Comp.	No. of Sep.	No. of Wells	No. of Tanks	No. of Comp.	No. of Sep.	No. of Wells	No. of Tanks	No. of Comp.	No. of Sep.
Parker	A	1	0	0	0	0	4	6	9	1	14	18	18	3
	B	1	0	0	0	0	4	6	9	1	14	18	18	3
	C	1	0	0	0	0	0	0	9	1	10	12	18	3
	D	2	0	0	0	0	0	0	0	0	8	6	2	1
	E	1	0	0	0	0	0	0	0	0	8	6	2	1
	F	1	0	0	0	0	0	0	0	0	8	6	2	1
	G	1	0	0	0	0	0	0	0	0	2	4	1	2
	H	1	1	0	0	0	1	0	0	0	1	0	0	0
		9
Tarrant	A	2	0	0	0	0	0	0	0	0	2	2	0	0
	B	2	0	0	0	0	0	0	0	0	2	2	0	0
	C	2	0	0	0	0	0	0	0	0	2	2	0	0
	D	1	1	0	0	0	5	10	3	2	21	40	11	8
	E	1	1	0	0	0	1	0	0	0	3	4	1	1
	F	1	1	0	0	0	1	0	0	0	2	2	1	1
	G	1	1	0	0	0	4	2	1	1	4	4	2	2
		10
Johnson	A	1	0	0	4	2	1	4	4	2	1	4	4	2
	B	1	0	0	4	2	1	4	4	2	1	4	4	2
	C	1	0	0	0	0	1	2	0	0	8	14	4	2
	D	2	0	0	0	0	1	2	0	0	8	14	4	2
	E	1	2	12	2	2	2	12	2	2	5	12	2	2
	F	1	1	2	0	0	1	2	0	0	1	2	0	0
		7
Denton	A	1	0	0	0	0	4	4	9	6	4	4	9	6
	B	1	0	0	0	0	4	4	9	9	4	4	9	6
	C	2	0	0	0	0	0	0	0	0	3	4	9	6
	D	3	0	0	0	0	2	2	6	1	4	4	9	6
	E	1	0	0	0	0	2	2	6	1	4	4	9	6
	F	1	0	0	0	0	2	2	4	6	4	4	9	6
	G	1	0	1	1	1	2	4	5	6	4	4	9	6
	H	1	0	0	0	0	2	0	0	0	2	0	0	0
	I	1	0	0	0	0	2	0	0	0	2	0	0	0
	J	1	0	0	0	0	0	0	0	0	5	6	4	2
	K	1	4	4	1	1	6	6	1	1	24	24	4	6
	L	2	0	0	0	0	2	0	0	0	6	6	0	1
	M	3	0	0	0	0	2	2	0	0	22	14	5	8
	N	1	2	2	0	0	6	0	1	1	12	12	12	4
		20
Somer-ville	A	1	0	0	0	0	0	0	0	0	4	6	2	0
		1
Wise	A	1	2	4	0	0	2	4	0	0	4	8	2	0
	B	1	0	0	0	0	0	0	0	0	4	8	2	0
	C	1	2	4	0	0	2	4	0	0	4	8	2	0
		3
Notes: Comp. = compressors; Sep. = separators.

Table 2. Summary statistics

CAS No.	Chemical	Min (ppbv)	Max (ppbv)	Median (ppbv)	Mean (ppbv)	SD	No. of ND
74828	Methane (ppmv)	1.9	457	2.7	11.99	63.58	1
71432	Benzene	0.6	592	0.89	18.53	83.75	11
67663	Chloroform	0.2	2.58	0.3	0.45	0.46	46
74873	Chloromethane/Methyl chloride	0.25	5.33	0.6	0.68	0.71	17
75718	Dichlorodifluoromethane (F12)	0.25	1.13	0.45	0.48	0.17	9
76142	Dichlorotetrafluoroethane (F114)	0.2	1	0.3	0.36	0.17	47
107062	1,2-Dichloroethane (EDC)	0.2	1	0.3	0.34	0.15	49
75092	Dichloromethane/Methylene chloride	0.2	1	0.3	0.34	0.15	49
100414	Ethylbenzene	0.2	113	0.53	4.42	16.03	23
87683	Hexachlorobutadiene	0.25	2.6	0.7	0.73	0.46	42
100425	Styrene	0.2	43.4	0.37	1.91	6.22	26
79345	1,1,2,2-Tethrachloroethane	0.2	2.06	0.3	0.37	0.28	49
127184	Tetrachloroethene (PCE)	0.2	2.43	0.3	0.33	0.39	47
108883	Toluene/Methylbenzene	0.34	276	2.55	19.45	48.77	3
108678	1,3,5-Trimethylbenzene	0.2	9.95	0.59	1.43	2.12	25
95636	1,2,4-Trimethylbenzene	0.2	60.4	0.4	3.45	10.79	27
120821	1,2,4-Trichlorobenzene	0.28	13.5	0.67	1.12	1.93	10
79016	Trichloroethene (TCE)	0.2	60.9	0.3	1.58	8.48	47
75694	Trichlorofluoromethane (F11)	0.2	1	0.3	0.34	0.15	45
1330207	m- and p-Xylene	0.25	221	1.68	15.69	43.1	7
95476	o-Xylene	0.2	39.4	0.85	3.19	6.7	15
75150	Carbon disulfide	0.7	103	4	11.75	20.5	22
463581	Carbonyl sulfide	0.3	36.7	1.41	4.22	7.1	40
624920	Dimethyl disulfide	0.3	200	1.93	15	31.56	29
20333395	Methyl ethyl disulphide	0.3	145	1.78	11.18	24.27	31
611143	Ethylmethylbenzene	0.3	42.8	1.4	3.15	6.74	47
2179604	Methyl propyl disulfide	0.3	41.6	1.4	2.59	5.71	49
110816	Diethyl disulfide	0.3	32.7	1.5	3.15	5.92	43
53966362	Ethyl, methylethyl disulfide	0.3	46.7	1.4	3.68	8.87	46
3658808	Dimethyl trisulfide	1.2	46.3	1.52	8.02	14.86	37
30453317	Ethyl n-propyl disulfide	0.3	25.2	1.4	2.25	3.48	48
95636	Trimethylbenzene	0.3	366	1.4	15.18	58.39	46
11020214	Undecane	0.3	72	1.4	3.05	9.88	49
2082613	1-Methyl propenylbenzene	0.3	51	1.4	2.63	6.96	49
112403	Dodecane	0.3	29	1.4	2.19	3.91	49
767599	1-methyl-1H Indene	0.3	79	1.4	3.19	10.86	49
768490	2-Methyl propenyl benzene	0.3	95.9	1.4	3.53	13.22	49
103651	Propylbenzene	0.3	23.5	1.4	2.08	3.16	49
25340174	Diethylbenzene	0.3	93.4	1.4	4.14	13.56	48
19876	Methyl-methylethylbenzene/methylcumene	0.3	84.7	1.4	3.31	11.65	48
110189	Tetramethylbenzene	0.3	36.4	1.4	2.76	5.69	48
91203	Napthalene/Trimethylbicyclo[2.2.1]heptane	0.3	30.3	1.4	2.5	4.27	47
109068	Methylpyridine	0.3	210	1.4	5.81	29.18	49
108485	Diemethyl pyridine/Aldrich	0.3	48.2	1.4	2.56	6.43	49
100710	Ethylpyridine	0.3	69.4	1.4	3	9.52	49
78784	2-Methylbutane	0.3	3620	1.4	88.04	507.51	44
109660	Pentane	0.3	198	1.4	7.73	28.59	45
108087	2,4-Dimethylpentane	0.3	50	1.4	2.61	6.82	49
963772	Methyl cyclopentane	0.3	22	1.4	2.4	3.75	48
561764	2-Methylhexane	0.3	35.3	1.4	2.71	5.44	48
565693	2,3-Dimethylpentane	0.3	98	1.4	3.57	13.51	48
589344	3-Methylhexane	0.3	2300	1.4	49.02	321.63	46
108872	Methylcyclohexane	0.3	38	1.4	2.42	5.15	48
540841	2,2,4-Trimethylpentane	0.3	17	1.4	1.95	2.29	49
	C3 Hydrocarbon	0.3	51.4	1.4	5.57	9.7	42
	C4 Hydrocarbon	0.3	137	1.4	6.6	21.61	44
	C5 Hydrocarbon	0.3	6780	1.65	145.24	947.97	28
	C6 Hydrocarbon	0.3	294	1.6	18.06	51.83	30
	C7 Hydrocarbon	0.3	2390	1.5	56.64	333.96	38
	C8 Hydrocarbon	0.3	1420	1.5	39.44	199.78	36
	C9 Hydrocarbon	0.3	761	1.41	19.78	106.43	42
	C10 Hydrocarbon	0.3	191	1.5	11.75	30.7	37
	C11 Hydrocarbon	0.3	53.6	1.4	3.92	9.51	46
	C12 Hydrocarbon	0.3	395	5	23.81	59.1	22
	C13 Hydrocarbon	0.3	231	1.57	10.88	35.03	40
76641	Acetone	0.3	20.7	1.4	2.04	2.81	49
74986	Propane (ppmv)	1	62.9	1.4	2.97	8.65	48
106978	Butane (ppmv)	1	69	1.4	2.95	9.45	48
74840	Ethane (ppmv)	1	34.6	1.4	2.24	4.66	49
75285	Isobutane	0.3	34	1.5	3.95	6.38	38
79925	Camphene	0.3	5.2	1.4	1.65	0.81	49
592574	Cyclohexadiene	0.3	7.1	1.4	1.76	1.1	49
103651	Propynylbenzene	0.3	7.2	1.4	1.74	1.13	49
226666	Diethyl trisulfide	0.3	8.23	1.41	2.14	1.62	43
513359	Methylbutane	0.3	16	1.4	1.93	2.16	49
2511957	Dimethylcyclopropane	0.3	29	1.4	2.19	3.91	49
75832	Dimethylbutane	0.3	15	1.4	1.91	2.03	49
107835	Methylpentane/Isohexane	0.3	199	1.4	6.1	27.79	48
110543	Hexane	0.3	35	1.4	2.46	4.81	48
138863	Limonene	0.3	12.9	1.4	2.14	2.15	47
	Dimethylpentatnone	0.3	42.8	1.4	2.47	5.82	49
	Bromohexene	0.3	5.2	1.4	1.69	0.84	49
3728550	Ethylmethylcyclohexane	0.3	6.1	1.4	1.82	1.15	48
4316658	Trimethylhexene	0.3	11.9	1.4	1.85	1.64	49
1072168	Dimethyloctane	0.3	20.4	1.4	2.02	2.74	49
7785708	1-R-alpha-pinene/2-Pinene/2.6.6Trimethylbichyclo[3.3.1]hept-2-ene	0.3	29	1.4	2.18	3.91	49
496117	Indane	0.3	15.2	1.4	1.9	2.06	49
590738	2,2,-Dimethylhexane	0.3	168	1.4	4.97	23.3	49
251412	Thieno[3,2] thiopene	0.3	56.5	1.5	5.18	10.7	43
78853	Methacrolein	0.3	1710	1.4	35.74	239.18	49
106467	1,4-Dichlorobenzene	0.2	4.43	0.3	0.55	0.66	45
591764	Methylhexane	0.3	25	1.4	2.11	3.66	46
75694	Trichlorofluoromethane	0.3	5.2	1.4	1.64	0.79	49
75456	Difluorochloromethane	0.3	45	1.4	2.51	6.12	48
137631	Tetramethylcyclopentane	0.3	9.24	1.4	1.79	1.33	49
4926787	Ethylmethylcyclohexane	0.3	5.68	1.4	1.78	1.04	48
6069983	Methylmethylethylcyclohexane	0.3	6.17	1.4	1.73	1.01	49
543599	Chloropentane	0.3	5.2	1.4	1.65	0.8	49
592574	1,3-Cyclohexadiene	0.3	5.8	1.4	1.73	0.98	49
60779240	Methyl n-butyl disulfide	0.3	15.5	1.4	1.92	2.1	49
72437640	Propyl n-butyl disulfide	0.3	14.6	1.4	1.9	1.98	49
629196	Dipropyl disulfide	0.3	23.1	1.4	2.07	3.11	49

Table 3. Comparison with other studies

	This Study			Garfield County, Colorado^a		Birmingham, UK^b	Weld County, Colorado^c	State of California^d
Chemical	Max (ppbv)	Median (ppbv)	Mean (ppbv)	Max (ppbv)	Median (ppbv)	Range of Means (ppbv)	Range of Medians (ppbv)	Ambient Average (ppbv)
Methane (ppmv)	457	2.7	11.99				1.81–1.89
Benzene	592	0.89	18.53	4.39	0.30	0.25–0.7	0.02–0.1	4.6
Chloroform	2.58	0.3	0.45					0.006–0.13
Dichloromethane/Methylene chloride	1	0.3	0.34					1.1–2.4
Ethylbenzene	113	0.53	4.42	1.87	0.04
Styrene	43.4	0.37	1.91	0.80	0.035			10
Tetrachloroethene (PCE)	2.43	0.3	0.33					0.71
Toluene/Methylbenzene	276	2.55	19.45	21.0	0.48	0.7–1.9
Trichloroethene (TCE)	60.9	0.3	1.58					0.22
1,3,5-Trimethylbenzene	9.95	0.59	1.43	0.25	0.024
1,2,4-Trimethylbenzene	60.4	0.4	3.45	0.63	0.037
m- and p-Xylene	221	1.68	15.69	2.28	0.20
o-Xylene	39.4	0.85	3.19	0.83	0.05
Propylbenzene	23.5	1.4	2.08	0.14	0.02
Pentane	198	1.4	7.73	21.1	3.09	0.2–0.5	0.01–0.48
Methyl cyclohexane	38	1.4	2.42	5.98	0.92
Propane (ppmv)	62.9	1.4	2.97			0.8–2.8	0.1–3.0
Butane (ppmv)	69	1.4	2.95			0.9–2.8	0.04–1.24
Ethane (ppmv)	34.6	1.4	2.24			2.2–6.3
Isobutane	34	1.5	3.95			0.8
Methylpentane/Isohexane	199	1.4	6.1			0.15–1.1
Hexane	35	1.4	2.46	7.11	1.14	0.1–0.2
Notes: Values are reported by California Air Resources Board for California, except for benzene, which was reported for the South Coast Air Basin of California (Los Angeles metropolitan area).^a McKenzie et al. (2012). ^bHopkins et al. (2005). ^c Petron et al. (2012). ^dSeinfeld and Pandis (1998).

Table 4. Pearson's correlation nonmethane volatile organic compounds

	Benzene	Chloromethane	Dichlorodifluoromethane	Toluene	m- and p- Xylene
Benzene	1.0
Chloromethane	0.0723	1.0
Dichlorodifluoromethane	−0.0791	−0.0999	1.0
Toluene	0.8927	0.1292	−0.1324	1.0
m- and p-Xylene	0.8658	0.0686	−0.1368	0.9543	1.0
C12 hydrocarbon	0.1823	−0.1746	0.2925	0.1744	0.257

Table 5. Correlation of methane to chemical constituents

Chemical	Correlated to Methane
Methane	1.0
3-Methylhexane	0.81
C5 Hydrocarbon	0.68
C9 Hydrocarbon	0.68
2-Methylbutane	0.64
C7 Hydrocarbon	0.55
C8 Hydrocarbon	0.55
Trichlorofluoromethane (F-11)	0.53
Hexachlorobutadiene	0.36
Tetrachloroethene (PCE)	0.35
C4 hydrocarbon	0.34
Methylhexane	0.33
C6 Hydrocarbon	0.33
1,2,4-Trichlorobenzene	0.33
Diethyl trisulfide	0.29
Chloroform	0.29

Table 6. Eigenvalues

	Eigenvalue	% total variance	Cumulative eigenvalue %	Cumulative %
1	8.13	22.57	8.1	22.57
2	6.12	16.99	14.24	39.56
3	3.27	9.07	17.51	48.63
4	2.69	7.47	20.20	56.11
5	1.98	5.49	22.17	61.60
6	1.77	4.92	23.94	66.51
7	1.53	4.26	25.48	70.77
8	1.27	3.52	26.75	74.29
9	1.18	3.28	27.93	77.57
10	1.06	2.94	28.98	80.51

Table 7. Chemicals associated with factor 1

Chemical	Coefficient
o-Xylene	−0.90
Ethylbenzene	−0.87
1,2,4-Trimethylbenzene	−0.82
m- and p-Xylene	−0.81
1,3,5-Trimethylbenzene	−0.80
Toluene	−0.76
Benzene	−0.74

Table 8. Chemicals associated with factor 2

Chemical	Coefficient
Trichlorofluoromethane	0.75
Methane	0.72
C5 hydrocarbons	0.72
C8 hydrocarbons	0.71

Figure 2. PCA sample site scores factor 1:factor 2.

Table 9. ANOVA tests to determine whether factors 1 and 2 are independent of gas well operation phases and equipment

ANOVA Test	Accept Null Hypothesis for Factor 1?	Accept Null Hypothesis for Factor 2?
Flaring	Yes	Yes
Fracking	Yes	Yes
Wells	Yes	Yes
Compressors	No	Yes
Tanks	Yes	Yes

McKenzie , L.M. , Witter , R.Z. , Newman , L.S. and Adgate. , J.L. 2012 . Human health risk assessment of air emissions from development of unconventional natural gas resources . Sci. Total Environ , 424 : 79 – 87 . doi: 10.1016/j.scitotenv.2012.02.018

 PubMed Web of Science ®Google Scholar

Petron , G. , Frost , G. , Miller , B.R. , Hirsch , A.I. , Montzka , S.A. , Karion , A. , Trainer , M. , Sweeney , C. , Andrews. , A.E. , Miller , L. , Kofler , J. , Bar-Ilan , A. , Dlugokencky , E.J. , Patrick , L. , Moore , C.T. Jr. , Tyerson , T.B. , Siso , C. , Kolodzey , W. , Lang , P.M. , Conway , T. , Novelli , P. , Masarie , K. , Hall , B. , Guenther , D. , Ktizis , D. , Miller , J. , Welsh , D. , Wolfe , D. , Neff , W. and Tans , P. 2012 . Hydrocarbon emissions characterization in the Colorado Front Range: A pilot study . J. Geophys. Res , 117: D04304 doi: 10.1029/2011JD016360

 Web of Science ®Google Scholar