Environ. Sci. Technol. 1906, 20 508-5 14 I
(29) Schnitzer, M.; Kahn, S. U. “Humic Substances in the Environment”; Marcel Dekker: New York, 1972. (30) McBain, M. E. L.; Hutchinson, E. “Solubilization and
Related Phenomena”;Academic Press: New York, 1955. (31) Elworthy, P. E.; Florence, A. T.; McFarlane, C. B. “Solubilizationby Surface Active Agents”;Chapman and Hall: London, 1968. (32) Tanford, C. “The Hydrophobic Effect”;Wiley: New York, 1973. (33) Nagarajan, R.; Ruckenstein, E. In ‘‘Surfactants in Solution”;
Mittal, K. L., Lindman, B., Eds.; Plenum: New York and London, 1984; Vol. 2, pp 923-947. (34) Moroi, Y.; Sato, K.; Noma, H.; Matuura, R. In “Surfactants in Solution”;Mittal, K. L., Lindman, B., Eds.; Plenum: New York and London, 1984; Vol. 2, pp 963-979. (35) Mackay, D.; Bobra, A.; Shiu, W. Y.; Yalkowsky, S. H. Chemosphere 1980, 9, 701.
(36) Chiou, C. T.; Schmedding, D. W.; Manes, M. Enuiron. Sei. Technol. 1982, 16, 4. (37) Buffle, J.;Deladoey, P.; Haerdi, W. Anal. Chim. Acta 1978, 101, 339. (38) Underdown, A. W.; Langford, C. H.; Gamble, D. S. Anal. Chem. 1981,53, 2139. (39) Thurman, E. M.; Wershaw, R. L.; Malcolm, R. L.; Pinckney, D. J. Org. Geochem. 1982,4, 27. (40) Aiken, G. R. E O S , Trans. Am. Geophys. Union, 1984,
65(45),951. (41) Means, J. C.; Wijayaratne, R. Science (Washington, D.C.) 1982, 215, 968.
Received for review August 8,1985. Accepted November 22,1985. A n y use of trade names is for descriptive purposes only and does not constitute endorsement by t h e U.S. Geological Survey.
Depth Profiles for Hydrocarbons and Polycyclic Aromatic Hydrocarbons in Soil beneath Waste Disposal Pits from Natural Gas Production G. A. Eiceman,” B. Davanl, and J. Ingram Department of Chemistry, New Mexico State University, Las Cruces, New Mexico 88003
Soil samples were obtained at four depths from 0 to 121 cm below unlined earthen waste pits associated with production, processing, and distribution of natural gas in the San Juan basin of northwest New Mexico. Sample extracts were analyzed by using capillary gas chromatography and gas chromatography/mass spectrometry for polycyclic aromatic hydrocarbons (PAH) to characterize potential for contamination of shallow groundwater. All soils contained complex mixtures of over 60-100 resolved hydrocarbons with carbons numbering from 10 to 45. Extracts were prefractionated for PAH quantification, due to complexity and concentration of interfering hydrocarbons. Over 30 PAH and alkylated PAH at total concentrations of 30-683 mg/kg were detected in soil samples. While concentration profiles for two-ring PAH showed a 20-fold decrease with depth at the produced water pit, less striking reductions were seen with the same compounds at the dehydrator and pipeline drip pits. Moreover, threeand four-ring PAH showed no appreciable variation with depth in any pit. Contamination of shallow groundwater a t depths of 1-2 m in flood plains of river valleys in New Mexico from wastes in unlined earthen pits is possible and likely.
Introduction Throughout production, processing, and distribution of natural gas, aqueous and hydrocarbon wastes can be generated in large volumes (1-3). Such wastes include brine (or produced) water from in-field separators, blow-down liquids from wellheads, condensate from inside pipelines, fluids from regeneration of dehydration and sweetening units, and discharge water from hydrostatic testing (DWHT) of pipelines. A common practice nationwide for disposal of these wastes is use of either surface impoundment pits, for containing wastes, or reinjection procedures. In northwest New Mexico and elsewhere in the U S . Southwest, earthen waste pits are constructed often 508
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without a clay or synthetic lining that retards movement of wastes into nearby soil and shallow groundwater. Since natural gas wells and associated waste pits are often found in flood plains of river valleys in New Mexico, and since groundwater can be found a t depths as shallow as 1.8 m in the same areas, mobility of organic compounds from waste pits through these soils should be known for prediction of impact on groundwater quality. However, suitable models and supporting studies on mobility of hydrocarbons and polycycic aromatic hydrocarbons (PAH) in complex aqueous mixtures through these soils are unavailable. Wastes that are generated during natural gas production are highly complex mixtures of hydrocarbons and PAH. For example, in samples of produced water from wells located in the San Juan basin of northwest New Mexico, concentrations of hydrocarbons in the aqueous portion of wastes were 200 pg/L to 235 mg/L while in the same produced waters over 50 PAH were found at total concentrations of 130 pg/L to 25 mg/L (1). Volatile organic compounds were also present in these wastes, and benzene was detected at 10-50 mg/L in the same produced water. Volumes of these wastes can be large; in New Mexico in 1982, over 24 billion liters of water were generated from 31 172 natural gas wells ( 4 ) . Some of these wastes are stored in unlined earthen waste (brine) pits in northwest New Mexico and elsewhere. Condensation of hydrocarbon impurities with molecular weights greater than hexane in pipelines leads to formation of liquids that result in reduced efficiency of gas flow (5). Such condensate is usually removed from pipelines in geographically low regions, and liquids are placed in earthen waste (drip) pits. These wastes can also be released to the environment in discharge water from hydrostatic testing of pipelines (2, 6). Few records are available to assess the total volume of either DWHT or condensate drippings, but the problem can be severe, as demonstrated in an exteme event where about 6000 L/day of condensate
00 13-936X/86/0920-0508$0 1.50/0 0 1986 American Chemical Society
PIPELINE
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PIPELINE D R I P P I T
PIT
DEPTH 3
i
I 00a
20an
3000
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Figure 1. Chromatograms from GC-FID analysis of hexane extracts for soil samples from a natural gas pipeline drip pit. Depths were (1) 0-30, (2) 30-60, (3) 60-90, and (4)90-120 cm. Attenuation was the amps full scale. same in every chromatograms at 16 X
were removed from a pipeline a t Chalmers Station near Detroit (5). Virtually no information is available on the composition of wastes in these drip pits and on potential for impact on shallow groundwater. Moreover, no information on the composition of wastes from regeneration of in-field dehydrators/sweeteners is generally available. While volatilization, adsorption, photodecomposition, and biodegradation have all been identified as possible mechanisms for environmental loss of hydrocarbons and PAH (7-9), these compounds have been found in surface soils from dry earthen brine pits (IO). The presence of these compounds in the surface soil represented a certain (but unknown) longevity and showed that complete loss of hydrocarbons did not occur rapidly through these mechanisms for loss or decomposition. Seepage of inorganic wastes from earthen brine pits has been shown to be extensive in Utah (11)and may portend possible migration of hazardous and toxic organic compounds from similar pits through soil and into shallow groundwater. Objectives for this study included (1) measurement of vertical (depth) profiles for hydrocarbons (including PAH)
DEPTH V
I
I 000
2000
3000
R E T E N T I O N INDEX
Flgure 2. Chromatograms from GC-FID analysis of PAH fraction from same samples shown in Figure 1. Attenuation was the same in every chromatogram at 4 X lo-'' amps full scale.
with carbon numbers from 10 to 45 in soils below earthen waste pits from three stages of gas production and distribution and (2) evaluation of soil depth profiles in terms of threat to groundwater quality from these waste pits. The three pits for produced water, dehydrator wastes, and pipeline condensate were selected for characterization. Experimental Section
Sample Collection. Soil samples were obtained on Jan 1, 1985, at sites in the Farmington Glade of northwest New Environ. Sci. Technol., Vol. 20, No. 5, 1986 509
Mexico. Ambient air temperature ranged from -5 to +5 "C while soil temperature was from 0 to 4 "C at 8-cm depth. Identical procedures were used in collection of soils a t each of three waste pits. A dry waste pit, usually 1to 1.9 m deep, was entered, and five locations were selected for sampling. The locations were chosen randomly from throughout the entire pit. Samples of soil from each location a t one depth within a pit were collected and composited in glass wide-mouth jars with screw caps. Samples were taken by using a core sampler (Soiltest, Evanston, IL), which had a collection head with a capacity of about 80 mL over a distance of 24 cm. After collection of soil at one depth, each location was resampled a t a greater depth. Between collection of samples at separate depths, the collection head was scraped to remove residual soil. Since the collection head was forced through 6-10 cm of fresh (unsampled) soil and since residue amounted to less than 2% by weight of the final sample, no additional cleaning of the collection head was employed. The depths were (1)0-30, (2) 30-60, (3) 60-90, and (4) 90-120 cm. These depths were measured from the bottom of the dry pit, and as much as 1.9 m should be added to provide a measure of depth to the surface of nearby terrain. Altogether, four sets of composited samples were collected for each pit corresponding to depths 1-4. The drip pit was a 3 m X 3 m earthen pit located roughly 6.4 km north from 63rd street into the Farmington Glade on Chokecherry Canyon Road. No designations on location, apart from a nearby pipeline with company logo, were found. The produced water pit and the dehydrator pit were from the same gas well a t a location of Section 23, T30N R13W. This site was roughly 3.2 km south of the drip pit. Samples were stored on ice during transport to the laboratory. Samples were then air dried for 48 h a t 25 "C before extraction, thoroughly homogenized in a large mortar and pestle, and placed on a ball mill for 30 min. Extraction and Treatment of Samples. All the samples were extracted, treated, and analyzed by using the same procedures. Fifty grams of dried soil was placed in a medium-porosity glass-fitted extraction thimble for extraction in a Soxhlet apparatus. Each sample was extracted with 200 mL of n-hexane (HPLC grade, Fisher Scientific Co., Fair Lawn, NJ) for 48 h (10). The extracts were filtered through glass columns containing 10 g of anhydrous Na2S04,condensed a t -40 OC to about 2 mL on a rotary evaporator, and further reduced to 1 mL with a gentle stream of nitrogen gas. The aliphatics and PAH were separated in,o two fractions on the basis of a class separation method using neutral alumina adsorption chromatography (13). This procedure was slightly modified in that the solidified extracts were liquified by placing the vial in a water bath at 30-40 "C, and then extracts were directly transferred to a 9 mm i.d. glass column containing 9 g of neutral alumina. The column was eluted with 30 mL of n-hexane and 50 mL of benzene (pesticide grade, Fisher Scientific Co., Fair Lawn, NJ) to collect the aliphatic hydrocarbons and PAH, respectively. The two fractions were concentrated to approximately 2 mL on a rotary evaporator and further reduced to 1 mL with nitrogen gas. All fractions were then analyzed under the same conditions by using gas chromatography (GC) with a flame ionization detector (FID). However, only benzene fractions were analyzed by selected ion monitoring (SIM) using gas chromatography/mass spectrometry (GC/MS) for PAH determinations. A mixture of deuterated PAH was added to the extracts as an internal standard to correct for losses in prefractionation and sample handling. Initial extraction of soil for PAH was considered exhaustive (10). Procedure and soil blanks were used to ensure no con510
Environ. Sci. Technol., Vol. 20, No. 5, 1986
PROCEDURE BLRNK
1808
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DEPTH 1
3800 R E i E N i l O N INDEX
Figure 3. Chromatograms from GC-FID analysis of PAH fraction for soil samples from a produced water pit, dehydrator waste pit, and a procedure blank. Attenuation was the same in each chromatogram and was 4 X lo-'* amps full scale.
tamination from the solvents, glassware, or presence of artifacts in the soil nearby the pits. No contamination from procedures or soil was detected. A mixture of PAH (naphthalene, biphenyl, fluorene, anthracene, and pyrene) with a Kovats Retention Index Standard (C10-C34)was made at three concentrations, prefractionated, and analyzed under identical conditions with those for the sample extracts to further verify efficiency of prefractionation methods. Initially, 3 X 100 and 5 X 100 mL nitromethane solvent extractions were used for removal of the alkanes from PAH. However, this procedure was unsuccessful (as inefficient separation was observed) and was replaced with the alumina column technique. Instrumentation. A Hewlett-Packard Model 5880A GC was equipped with FID, automated splitless injector, and a DB-5, 10 m long X 0.25 cm i.d. fused silica capillary column. Conditions for analysis of all samples were the following: initial temperature 30 "C; program rate 6 OC/min; final temperature 260 OC; final time 5 min; injector port temperature 250 "C; FID temperature 270 OC; carrier gas nitrogen at 30 cm/s average linear velocity; time for splitless injection 1.5 min; chart speed 0.5 cm; area reject 10. A Hewlett-Packard Model 5995A GC/MS was equipped with jet separator, Model 5885M disk drive, Model 7225B X-Y plotter, automated spitless injection port, and a 10-m DB-5 fused silica capillary column.
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Chromatographic conditions were identical for SIM, scanning GC/MS, and GC-FID analysis. Mass spectrometer conditions for scanning analyses were the following: lower mass 45 amu; upper mass 600 amu; scan speed 690 amu/s; delay between scans 0.1 min; electron multiplier voltage 1400; MS detection threshold 10 linear counts. Mass spectrometer conditions for SIM analyses were the following: electron multiplier voltage 1600 V; SIM window size 0.2 amu; integrate sensitivity 0.05; area threshold 10; smoothing factor 1; selected polycyclic and alkylated polycyclic aromatic hydrocarbons with ions chosen for SIM analyses have been given (2). Sample volumes in GC and GC/MS analyses were 0.5-2 pL delivered by using Model 701N 10-pL syringe (Hamilton Co., Las Vegas, NV).
Conditions other than these will be noted as necessary.
Results and Discussion Gas Chromatographic Analysis. Results from GCFID analysis of soil extracts from the pipeline drip pit a t four depths are shown as chromatograms in Figure 1. Depths 1-4 correspond to values given in the experimental section. A complex mixture of over 60 major resolved components with carbon numbers between 10 and 45 was found at each depth. The regular spacing, peak shape, and comparison to retention times for the Kovats standard were consistent with the presence of alkanes as the major components as later confirmed in GC/MS analyses. In addition, the base-line shape was consistent with a large Environ. Sci. Technol., Vol. 20, No. 5, 1986
511
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mass of unresolved hydrocarbons. In both the carbon number range and sample complexity, these mixtures strongly resembled condensate inside consumer distribution pipelines ( 3 ) and the nonaqueous phase in a brine waste pit (1). Since pipeline drip pits are positioned physically between wellheads and the consumer distribution lines, similarities in samples from each stage might be expected. Chromatographic profiles for soil at depths below these waste pits shown were remarkable as shown in Figure 2. At each depth, a similar chromatographic pattern was obtained across the range of carbon numbers, even with the high molecular weight components from C,, to C45. A slight attenuation of the total unresolved mass was seen between depth 1and other depths, but no change was seen with this mass between depths 3 and 4, suggesting 512
Environ. Sci. Technol., Vol. 20, No. 5, 1986
some type of loss or attenuation for hydrocarbon mass. A dramatic increase in the abundance of components at carbons ranges from 10 to 20 a t depth 4 was especially striking. Thus, while hydrocarbons of this size are often described as having strong adsorption (7) to lipophilic organic matter in soil and should be relatively immobile, the zones of earth under this pit clearly have been saturated and little, if any, significant attenuation of mobility for these compounds is evident from these results. Similar results in terms of carbon range, base-line patterns, and depth profiles were also seen with the produced water and pit and the dehydrator pit. Preliminary survey of these extracts using GC/MS with SIM methods for PAH content showed major interference from saturated and unsaturated alkanes, which precluded
Table I. Concentrations (pglkg)" of PAHb in Soils NA C1-NA C2-NA BP CIBP C2-BP FL C1-FL CzFL AN CLAN C2-AN PY C1-PY total, depth (128.l)e (142.1) (156.1) (154.1) (168.1) (182.1) (166.1) (180.1) (194.1) (178.1) (192.1) (706.1) (202.1) (216.1) mg/kg
2 3 4
31000 NDd 18000 6200
320000 320000 53000 7300 260000 300000 260000 280000
1600 910 1500 1500
3900 1400 2900 3200
2500 1500 2400 2400
Pipeline Drip Pit 760 800 530 600 800 780 760 820
600 490 620 670
600 470 650 670
580 450 620 690
420 340 500 490
210 190 270 240
210 190 260 230
683 617 589 557
1
ND
2 3 4
ND ND ND
68000 270000 130000 260000 3400 24000 3000 37000
1200 1500 330 380
1700 1400 290 300
2600 1900 890 880
Produced Water Pit 1400 1300 850 850 420 510 460 540
690 530 470 500
600 470 650 660
640 470 450 500
340 470 340 380
190 330 190 214
190 190 190 190
349 399 132 45
1 2 3 4
ND ND ND ND
27000 4500 13000 11000
1700 2400 1800 1800
1400 1800 1300 1800
310 200 310 280
Dehydrator Pit 280 270 340 330 340 340 360 380
260 330 330 360
260 310 310 340
260 310 310 340
240 310 310 340
290 190 190 210
1
22000 24000 13000 13000
54 35 31 30
"Data only satisfactory to two significant figures. bPAH: NA = naphthalene, BP = biphenyl, FL = fluorene, AN = anthracene, and PY = pyrene. SIM ion. ND, not determined.
reliable quantification. A rapid column prefractionation scheme ( I O , 12) was used to isolate the PAH, and results from GC-FID analysis of these isolated fractions for the drip pit samples are shown in Figure 1. Since all experimental instrumental conditions were unchanged, chromatograms within Figure 2 may be compared directly to those in Figure 1 at the same depths. The efficiency for removal of hydrocarbons from the PAH, based on compression of hydrocarbon content in samples before and after prefractionation, was 90-99%. However, GC-FID profiles still showed a complex mixture of components in the PAH fraction. Although a few alkanes were evident in chromatograms from depths 2 and 3, the general hydrocarbon pattern was minor if present at all in the PAH fractions. For pipeline drip pit samples as shown in Figure 2, some attenuation with depth was evident, particularly at bottom depths 3 and 4, on the basis of GC-FID results. However, a more specific means for quantification of individual PAH compounds was needed. Although the pits chosen and the pipeline were related only by a common gas field origin and were not connected, results for the produced water pit and for the dehydrator pit were similar to, but not identical with, those for the drip pit. As shown in Figure 3, the PAH fraction for these other pits showed similar complexity to the drip pit samples. The procedure blank was clean for both total extractable hydrocarbon analysis as well as for analysis of PAH fractions. Selected Ion Monitoring for PAH. Results from GC/MS analysis using SIM techniques for PAH fractions of soil extracts are shown in Figures 4 and 5 and in Table I. In Figures 4 and 5, SIM plots for all depths from the pipeline drip pit are shown for 14 PAH and alkylated PAH. While the bottom plot was for the base peak in alkanes, ( m / z 57.1 amu) the ion mass in other SIM plots corresponded to the molecular ion for the appropriate PAH. Major peaks in SIM plots matched known retention times for internal standards. Exceptions were for naphthalene, where two components at a 18-min retention time were major peaks, and for biphenyl, where a set of barely resolved components with retention times near 20 min was present at relatively high concentrations. Otherwise, no major interferences were seen or were of any consequence in these SIM analyses. The presence of these PAH in the soils is also consistent with prior studies where PAH were found in natural gas (31, pipeline condensate (3),produced water ( I ) , and surface soils near waste pits ( I O ) .
Environmental Impact. Concentration values for individual PAH in soils are listed in Table I for each pit at every depth, and the results are shown graphically in Figure 6. The total concentrations of PAH a t various depths for pits were 557-683 mg/kg for pipeline drip pit, 45-399 mg/kg for the produced water pit, and 30-54 mg/kg for the dehydrator pit. In general, total concentrations decreased slightly with increasing depth with the most dramatic reduction occurring a t the produced water pit which receives a large aqueous loading compared to dehydration or drip pits. This pattern seemed especially pronounced for the two-ring PAH such as naphthalenes and biphenyls, which actually predominate and skew the total PAH values as shown in Figure 6. For example, the concentration of methylnaphthalene in the produced water pit decreased by 20-fold from 68 mg/kg at depth 1 to 3 mg/kg at depth 4. In the same pit, dimethylnaphthalene decreased from 270 mg/kg at depth 1to 37 mg/kg at depth 4. However, similar patterns were not observed with threeand four-ring PAH and were not even consistent in all waste pits, despite the same sandy soil. In the pipeline drip pit, changes in concentrations for naphthalenes and biphenyls were irregular a t best. While the fluorenes, anthracenes, and pyrenes were largely unabated as a function of depth, in contrast, concentrations for naphthalenes and biphenyls were reduced in the dehydrator pit. Since these samples come from highly complex systems and represent only single points on the time scale, few general conclusions on mobility and fate of PAH in soils may be made. However, of the four major mechanisms for attenuation of hydrocarbons in soils (namely, volatilization from soil, adsorption, biodegradation, and photodecomposition), results here showed that PAH survived in these soils and migrated through what likely was saturated soil. Since groundwater in flood plains in New Mexico can be within 1-2 m from land surface and since this depth profile with these wastes extended from 2 to 3 m from the land surface, contamination of groundwater in such regions is possible. While the presence of these PAH in soils a t depths of 2-3 m and in shallow groundwater may not have much consequence on the basis of conventional toxicity, recent results on phototoxicity of PAH with fish (13), shrimp (241, and other organisms (25) portend serious complications for a total aquatic environment should groundwater move into surface waters. These PAH give toxic responses only a t extremely high concentrations of Environ. Sci. Technol., Vol. 20, No. 5, 1986
513
exposed to light. Although New Mexico has over 31 000 gas wells that are generating produced water, not all wells have unlined earthen pits, and not all pits are located in shallow groundwater areas. Moreover, in this report contamination of an aquifer has not been demonstrated, and only mobility of PAH and large hydrocarbons through soils common to northwest New Mexico has been verified. However, pipeline drip pits, which along with produced water pits can be threats to water quality, have not been cited in a recent state survey of impoundment pits (16) and should be included in future descriptions of industrial waste sites in New Mexico and nationwide. PIPELINE D R ’ F P I T
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(1) Davani, B.; Dodson, J.; Gardea, J.; Eiceman, G. A. Znt. J . Environ. Anal. Chem. 1985,20, 205. (2) Eiceman, G. A.; Davani, B.; Dodson, J. A. Znt. J. Environ. Anal. Chem. 1984,19, 27. (3) Eiceman, G. A.; Davani, B.; Wilcox, M. E.; Gardea, J. L.; Dodson, J. A. Environ. Sei. Technol. 1985, 19, 603. (4) Records from Oil Conservation Division, Department of Energy and Minerals, State of New Mexico, Courtesy of Oscar Simpson and J. Ramey. ( 5 ) Bergman, D. F.; Tek, M. R.; Katz, D. L. “Retrograde Condensation in Natural Gas Pipelines”. American Gas Association, 1975, Project PR 26-69, final report to Pipeline Research Committee. (6) Eiceman, G. A.; Leasure, C. S.; Baker, B. D. Znt. J. Environ. Anal. Chem. 1983,16, 149. (7) Sims, R. C.; Overcash, M. R. Residue Rev. 1983, 88. (8) Pettyjohn, W. A.; Hounslow, A. W. Ground Water Monit. Rev. 1983, 3, 341-347. (9) Newsom, M. J. Ground Water Monitor. Rev. 1985,5, 29. (10) Davani, B.; Ingram, J.; Gardea, J.; Eiceman, G. A. Water, Air, Soil Pollut., in press. (11) Baker, F. G.; Brendecke, C. M. Ground Water 1983, 21, 317-324. (12) Later, D. W.; Lee, M. L.; Bartle, K. D.; Kong, R. C.; Vassilaros, D. L. Anal. Chem. 1981, 53, 1612. (13) Bowling, J. W.; Laversee, G. J.; Landrum, P. F.; Griesy, J. P. Aquat. Toxicol. 1983, 3, 79. (14) Morgan, D. D.; Warshawsky, D. Photochem. Photobiol. 1977, 25, 39. (15) Kagan, J.; Kagan, P. A.; Buhse, H. E., Jr. J. Chem. Ecol. 1984, 10, 1115. (16) McQuillan, D. M. “Organic Water Contaminations in New Mexico, An Assessment of Known and Potential Problems”. Health and Environment Department, State of New Mexico, Santa Fe, NM, April 1984, Report EID/GWH-84/3.
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Flgure 6. Depth profiles for PAH in soils collected at three waste pits and natural gas production. Compounds are (a) pyrenes, (b) anthracenes, (c) fluorenes, (d) biphenyls, and (e) naphthalenes.
over 10 mg/L but were found to be lethal to fish, frogs, and insects at low microgram per liter concentrations when
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Received for review June 10,1985. Accepted November 25,1985. This work was supported by New Mexico Water Resources Research Institute and the Environmental Improvement Division of the Department of Health and Environment, State of New Mexico.
