Environ. Sci. Technol. 1992,26, 126-133
Krahn, M. M.; Burrows, D. G.; MacLeod, W. D., Jr.; Malins, D. C. Arch. Enuiron. Contam. Toxicol. 1987, 16, 511. Fedorak, P. M.; Westlake, D. W. S. Can. J. Microbiol. 1981, 22, 432. Fedorak, P. M.; Westlake, D. W. S. Can. J. Microbiol. 1983, 29, 291. Payne, J. R.; Kirstein, B. E.; McNabb, G. D., Jr.; Lambach, J. L.; Redding, R.; Jordan, R. E.; Hom, W.; deoliveira, C.; Smith, G. S.; Baxter, D. M.; Gaegel, R. Multivariate analysis of petroleum weathering in the marine environment-sub arctic. Volume I-Technical results. Environmental assessment of the Alaskan continental shelf. Final reports of principal investigators; U.S. Dept. of Commerce, Washington, DC, 1984. Willey, C.; Iwao, M.; Castle, R. N.; Lee, M. L. Anal. Chem. 1981, 53, 400. Boehm, P. D.; Fiest, D. L.; Elskus, A. Proceedings of the International Symposium on the Amoco Cadiz: Fates and Effecta of the Oil Spill; Centre National pour 1'Exploitation des Oceans; Paris, 1981; p 159. Atlas, R. M.; Boehm, P. D.; Calder, J. A. Estuarine, Coastal Shelf Sei. 1981, 12, 589. Gruger, E. H., Jr.; Schnell, J. V.; Fraser, P. S.; Brown, D. W.; Malins, D. C. Aquat. Toxicol. 1981, 1, 37. Varanasi, U.; Nishimoto, M.; Reichert, W. L.; Eberhart, B.-T. L. Cancer Res. 1986, 46, 3817. Krahn, M. M.; Wigren, C. A.; Pearce, R. W.; Moore, L. K.; Bogar, R. G.; MacLeod, W. D., Jr.; Chan, S.-L.; Brown, D. W. Standard Analytical Procedures of the NOAA National Analytical Facility. New HPLC cleanup and revised extraction procedures for organic contaminants. NOAA Tech. Memo. 1988, NMFS F/NWC-153. Krahn, M. M.; Moore, L. K.; Bogar, R. G.; Wigren, C. A.; Chan, S.-L.; Brown, D. W. J. Chromatogr. 1988,437, 161.
(21) Solbakken, J. E.; Palmork, K. H.; Neppelberg, T.; Scheline, R. R. Acta Pharmacol. Toxicol. 1980, 46, 127. (22) Solbakken, J. E.; Palmork, K. H. Comp.Biochem. Physiol. 1981, 70C, 21. (23) Krahn, M. M.; Moore, L. K.; MacLeod, W. D., Jr. Standard Analytical Procedures of the NOAA National Analytical Facility, 1986 Metabolites of aromatic compounds in fish bile. NOAA Tech. Memo. 1986, NMFS/NWC-102. (24) Zar, J. G. Biostatistical Analysis, 2nd ed.; Prentice Hall: Englewood Cliffs, NJ, 1984; p 261. (25) Hellou, J.; Banoub, J. H.; Payne, J. F. Chemosphere 1986, 15, 787. (26) Krahn, M. M.; Rhodes, L. D.; Myers, M. S.; Moore, L. K.; MacLeod, W. D., Jr.; Malins, D. C. Arch. Enuiron. Contam. Toxicol. 1986, 15, 61. (27) Krahn, M. M. Northwest Fisheries Science Center, unpublished data, 1985. (28) Collier, T. K.; Varanasi, U. Arch. Environ. Contam. Toxicol., in press. (29) Brown, D. W. Northwest Fisheries Science Center, unpublished data, 1990. (30) Stein, J. E.; Hom, T.; Varanasi, U. Mar. Environ. Res. 1984, 13, 97. (31) Varanasi, U.; Stein, J. E. Enuiron. Health Perspect. 1991, 90, 93. (32) Krone, C. A,; Stein, J. E.; Varanasi, U., submitted for publication in Chemosphere.
Received for review June 10,1991. Accepted August 5,1991. This study was funded in part as an ancillary project of Technical Services No. 1, National Resources Damage Assessment. Mention of trade names is for information only and does not constitute endorsement by the U.S. Department of Commerce.
Gas- and Particle-Phase Concentrations of a-Hexachlorocyclohexane, y-Hexachlorocyclohexane, and Hexachlorobenzene in Ontario Air Douglas A. Lane,*,+N. Douglas Johnson,: Mary-Jane J. Hanley,: William H. Schroeder,t and David T. Ordt
Environment Canada, Atmospheric Environment Service, 4905 Dufferin Street, Downsview, Ontario, M3H 5T4, Canada, and Ortech International, 2395 Speakman Drive, Mississauga, Ontario, L5K 1B3, Canada The airborne gas-phase and particle-phase concentrations of a-hexachlorocyclohexane (a-HCH), y-hexachlorocyclohexane (7-HCH), and hexachlorobenzene (HCB) were measured near Turkey Lake (in central Ontario) and at Pt. Petre (on the north shore of Lake Ontario) between the spring of 1987 and the spring of 1989 using a gas and particle (GAP) sampler which employs a multiannular diffusion denuder to trap the vapor-phase constituents. During October 1987 at Turkey Lake, HCB, a-HCH, and y H C H were all exclusively in the vapor phase. At Pt. Petre, during November and March when comparable temperatures prevailed, the vapor-phase components for HCB, a-HCH, and y-HCH were 96.6%, 97.6%, and 100% respectively. The overall method detection limits for HCB, a-HCH and y-HCH were 7, 14, and 15 pg/m3. The a-HCH/y-HCH ratio was always greater than 1.8 and generally between 6 and 10, indicating the detection of technical grade HCH and/or the environmental isomerization of the y form to the a form. Introduction
Long-range atmospheric transport and deposition is often implicated as being the primary mechanism to ex+ EnvironrnentCanada.
Ortech International. 126
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plain the presence of toxic contaminanb in locales remote from known sources. Specific attention has recently focused on the semivolatile organic compounds (SVOCs) such as the chlorinated pesticides, polychlorinated biphenyls (PCBs), polycyclic aromatic compounds (PACs), and other medium to high molecular weight species (1-15). These compounds enter the atmosphere through volatilization during application of pesticides such as lindane, through the disposal of the byproducts from the chemical synthesis of other compounds, and as products of incomplete combustion that occur in sources such as incinerators. SVOCs exist in the atmosphere in the vapor phase, in the solid phase (as adsorbed components of suspended particulate matter), and associated with aerosols. The vapor/particle distribution ratio will strongly influence the residence time of a pollutant in the air and its removal from the atmosphere by wet and dry deposition processes. For those compounds which have an appreciable aqueous solubility, dissolution at the air/water interface (for example, at bodies of water or raindrops) can be expected to occur. The effectiveness of washout will depend upon the aqueous solubility of the individual vapors. Substances which have substantial particle-phase components may be removed primarily by dry deposition of particles, or by washout (16-18). Those compounds which are not removed from the atmosphere by air/water exchange processes and which do not adsorb or absorb to particles may
0013-936X/92/0926-0126$03.00/0
0 1991 American Chemical Society
have substantial atmospheric lifetimes since they will be removed neither by precipitation nor by particle deposition. For such compounds, dry vapor deposition at the earth's surface or atmospheric chemical or photochemical reaction may be the predominant removal mechanisms. A prototype sampling system has been developed (19) to monitor the occurrence and phase distribution in ambient air of three compounds that are designated as priority contaminants in the Great Lakes ecosystem. The gas and particle (GAP) sampler, developed on the principles of an annular diffusion denuder, has been calibrated in the laboratory for its response to a- and y-hexachlorocyclohexane (HCH) and hexachlorobenzene (HCB) at vapor and particle concentrations anticipated to occur in the atmosphere at remote locations (19). The denuder was designed to remove the vapor fraction of SVOCs prior to filtration and a means was provided to account for potential compound "blowoff" from collected particulate matter during sampling. The overall objective of the present study was to measure the airborne vapor and particle concentrations of aand y-HCH and HCB a t the Turkey Lake watershed in central Ontario (approximately 40 km north-northeast of Sault Ste. Marie) and at Pt. Petre on the north shore of Lake Ontario (approximately 180 km east of Toronto). The Turkey Lake sampling site exists in a calibrated watershed area used by a number of research agencies to perform precipitation and water quality studies. At Pt. Petre, a "master" station (intended for research, and development/evaluation of analytical techniques by a number of government agencies) has been established as part of the U.S.-Canada Agreement on Great Lakes Water Quality. Ambient air measurements were made in the early spring, summer, and late fall at Turkey Lake and throughout the winter at Pt. Petre to test the performance of the GAP sampler under a variety of temperature and relative humidity conditions. Experimental Section A detailed report on the design of the GAP sampler and the denuder-coating methods can be found in a previous publication (19). The GAP sampler comprises two individual samplers, which are operated in parallel. In one sampler, air (after passing through a 10-pm size-selective inlet) passes through a multitube, annular, diffusion denuder which has been coated with silicone oil and crushed Tenax. The denuder traps and retains the vapor-phase constituents while allowing the particulate matter to pass through the denuder and to be collected on a particle filter. Downstream of the filter, two cartridges (in series) containing Florisil trap any of the components which might volatilize from the surface of the collected particles, or which might be associated with particles too small to be trapped by the filter. From this sampler, the particlephase component is determined by adding together the amount of each target appearing on the filter and in the adsorbers. In the second sampler (identical to that just described but without a denuder, and which we call the "conventional" sampler), the total atmospheric loading (vapor and particle phases) of the contaminants is determined. The fraction of the component which occurred in the vapor phase is determined by subtracting the denuder sampler result from the conventional sampler result. The annular diffusion denuder can be used either with a modified dichotomous sampler containing filters and attached (Florisil) adsorbers for particle size information (coarse- and fine-particle segregation) or with a single filter/adsorber unit. Although particle size information
is generally desirable, the extremely low concentrations of the target compounds encountered at these two sites necessitated the use of the single filter/ adsorber configuration to maximize the signal to noise response of the target compounds. Prior to each test series, the Tenax coated denuders were heated in a tube furnace at 260 "C for a minimum of 1 2 h while being purged with a 2 L/min flow of prepurified nitrogen gas. The nitrogen gas passed through a bed of Florisil adsorbent and was then heated to 260 "C prior to entering the denuder. After being cooled, the denuders were capped and used within 2 weeks of cleaning. Whatman GF/A glass fiber filters (47-mm diameter) were baked in a muffle furnace at 300 "C for 44 h, then cooled, and stored in plastic cassettes. The filters were conditioned and weighed before and after sampling on a Cahn microbalance, which was located in a room in which the relative humidity was kept below 50% and the temperature was maintained at 22 "C. The filters were conditioned in this room for a minimum of 48 h prior to weighing. During weighing, a zlOPo0source was used to prevent static buildup inside the microbalance. The glass cartridges for the backup adsorbents were cleaned in a 3% detergentldeionized water solution for 24 h and then rinsed with deionized water, distilled-in-glass acetone, and hexane. Florisil (30/60 mesh) was heated in batches at 650 "C in a tube furnace under precleaned Ultra Zero Air for 75 h and then extracted in a Soxhlet extractor with distilled-in-glass hexane for 24 h. After being dried in a vacuum desiccator, the Florisil was transferred to the cartridges (60 g/cartridge and a depth of 8.0 cm). The adsorbent in the cartridges was subsequently eluted with 300 mL of 30% methylene chloride in pesticide grade hexane (MCH) followed by 150 mL of hexane. The cartridges were dried under vacuum and stored in a desiccator at 135 "C until used. No cartridge was stored for more than 2 weeks. For transport, the cartridges were capped and transported in a portable, 12-V cooler maintained at -5 "C. Except for the period of sample collection, the adsorbers were kept in the cooler at -5 "C. Just prior to sampling, the inside surfaces of the 10-pm inlets and other transfer tubes (which contact the air) of the samplers were rinsed with hexane. Sampling Locations. At Turkey Lake, the sampling station was located in a summit clearing in hilly terrain approximately 7 km from the nearest highway and 1.5 km southeast of Little Turkey Lake. The sampling site was serviced by a dirt road and by electrical power from a diesel generator, which was located in a valley approximately 30 m below and 70 m distant from the sampling site. Being remote from all known or suspected anthropogenic sources of SVOCs, concentrations of the target compounds at this location could be considered to be regionally representative in nature. The air samplers were placed on top of a van beside a sampling platform (approximately 4 m by 10 m in size and 1.5 m above the ground) so that the air intake was 5 m above the ground. Meteorological data were obtained from an Environment Canada meteorological tower at the sampling site. During the spring, summer, and fall of 1987, three denuder samplers and two conventional samplers were employed to collect the air samples. After the spring measurements and before the summer measurements of 1987, a 15-cm bed of wood chips was laid down on the last 30 m of the dirt road leading to the site and under and around the sampling platform in an attempt to reduce potential dust reentrainment to the at-
-
-
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127
mosphere from the human activity (attending to the meteorological tower and other samplers on the platform) at the site. The Pt. Petre sampling site is located near the Sandbanks Provincial Park, at a point extending into Lake Ontario, and is away from industrial and other anthropogenic sources. The samplers were placed on a wooden platform approximately 60 m from the shore of Lake Ontario. There were no trees or bushes between the sampling platform and the lake. The site is serviced with electrical power and an Environment Canada meteorological tower. During each sampling period, three sets of (nominally) 46-h triplicate samples were collected. Filters, denuders, and adsorbers were changed every second day. Filter and adsorber field blanks were obtained during each sampling period. Air sampling was controlled at a flow rate of 16.7 L/min (filter face velocity of 26 cm/s) by Tylan mass flow controllers, and the total volume sampled was determined by dry test meters which had been calibrated against a primary (gasometer) standard. Analytical Methods. Upon return of the samples to the laboratory after field exposure, the Florisil adsorbent, still in the glass cartridges, was extracted with three separate 100-mL portions of 30% methylene chloride in pesticide grade hexane. The three portions were collected in a 500-mL Rotovap flask, a 2-mL aliquot of isooctane was added to the flask as a "keeper", and the pooled eluates were concentrated to approximately 2 mL for cleanup. Each filter was extracted in a 125-mLboiling flask with -20 mL of MCH over a period of 12 h, during which the flask was periodically agitated. The extract was transferred to another boiling flask and the flask, still containing the filter, was rinsed several times using a total of -50 mL of MCH. The combined extract and washings were concentrated to 2 mL for cleanup using the same technique as that for the Florisil adsorbents. Sample extract cleanup was carried out on a Florisil column. A glass column (9-mm inside diameter and 20-cm length) was prepared from 8 g of 60-80 mesh Florisil, which had been heat cleaned at 300 "C and deactivated with 2% water. Anhydrous sodium sulfate (1cm) was added to the top of the column, which was then washed with 100 mL of hexane. The sample extract was placed on the top of the column and eluted with 120 mL of MCH (the sample flask was rinsed with several portions of the 120-mLMCH eluent). After elution, the eluent volume was reduced to approximately 10 mL in a rotary evaporator and then transferred to a graduated Vortex tube containing 2 mL of isooctane. The evaporator flask was rinsed with several portions of isooctane, which were also added to the Vortex tube. The volume of eluent was reduced in the Vortex evaporator to just below 2 mL and was subsequently made up to a volume of 2 mL with isooctane. The samples were dispensed into precleaned vials with Teflon-lined silicon septa and alumina caps prior to analysis. A Hewlett-Packard 5890 gas chromatograph, outfitted with an H P 7673A robotic arm autosampler, was used for the analyses of the target components. Injections (4 pL) were split to two capillary columns of different polarity (Ultra 1and Ultra 2; 25 m by 0.31 mm; 0.51-pm-thick film). The different polarities of the column phases resulted in different retention times of the target compounds. If there were a contaminant which interfered with the analysis on one column, it would not likely cause intereference to the same component on the other column. The injector was maintained at 250 "C for the injections while the column temperature was programmed from 90 to 280 "C at a rate 128
Environ. Sci. Technol., Vol. 26, No. 1, 1992
of 3 OC/min. The detector for each column was a 63Ni electron capture detector held at 350 "C. Helium was used as the carrier gas (50 cm/s), and 5% argon in CH4 (60 mL/min) was used as the makeup gas. Quantitation was performed with an H P 5840 GC Chem Station. Calibration standards were run between samples. Results and Discussion In spite of the exhaustive cleaning of the Florisil adsorbents, extraction of blank and sample-containing adsorbents always revealed extraneous components. In most cases, however, the target compounds were easily resolved from these contaminant peaks. When the measured concentrations of the targeted compounds, as revealed by the two-column analytical method, did not agree, it was assumed that the higher result reflected the presence of some interfering component(s). The lower of the two results was considered to be less subject to interference(s) and, therefore, to be the more accurate result. In most cases, the difference between the two columns was not substantial. Differenceswere usually less than 25% and often less than 10%. A series of Florisil adsorbers were spiked with 2.5 ng of each of the target compounds (a level anticipated to be derived from air sampling at regionally representative locations such as the Turkey Lake watershed and at Pt. Petre) in order to determine the efficiency of compound recovery by the analytical methods described above. The mean recovery efficiency (%) and the standard deviation (a) for (n)replicate measurements were as follows: for HCB 102%, u = 4.3%, n = 8; for a-HCH 91%, u = 8.5%, n = 9; and for 7-HCH 97%, B = 9.2%, n = 10. Much of the variation in recoveries can be attributed to the fact that the concentrations of the target compounds used to spike the adsorbers, although close to the amounts anticipated to be collected during a normal air sampling period, were very close to the limits of detection for these compounds. The concentrations of the target compounds reported herein were not corrected for recovery efficiency. Detection limits (DL) were calculated by multiplying the standard deviation of the recovery efficiency (from cartridges spiked with 2.5 ng of each of the three organochlorines) by 3 and normalizing to a standard air sample of 46 m3. Quantitation limits (QL) were similarly calculated by multiplying the standard deviation by 10 and normalizing to the same standard air volume. The resulting DL and QL for each of the target compounds were as follows: for HCB DL = 7 pg/m3, QL = 23 pg/m3; for a-HCH DL = 14 pg/m3, QL = 46 pg/m3; and for y H C H DL = 15 pg/m3, QL = 50 pg/m3. Analysis of the field blanks (Florisil adsorbers and filters taken to the sampling location in the cooler, placed in the sampler housing, and returned to the laboratory in the portable cooler with the field samples) demonstrated a very low contamination level. Background interferences usually represented a contamination level of less than 100 pg/ cartridge and always less than 500 pg/cartridge. For a 46-h sampling period, these values correspond to nominal air concentrations of 2 and 11pg/m3, respectively. The blank measurements for the three targets were, with the odd occurrence for HCB, well below the detection limit. Often, the gas chromatographic trace yielded a flat response at the retention times of the three target compounds. The constituent amounts in the field blanks obtained during a sampling period (three consecutive sets) were averaged, and this value was subtracted from each field measurement taken during the sampling period. The suspended particulate matter concentrations (obtained with 10-pm or, occasionally, 15-pm size-selective
Table I. Suspended Particulate Matter Loadings (pg/m3) for the Turkey Lake Sampling Site
conventional samp 1er
denuder sampler 1 2 3
(I
date 8710518-10 87/05/10-12 87/05/12-14 87107124-26 87107126-28 87107128-30 87/10/20-22 87110122-24 81110124-26
2
1
25' 29'
12 8 14 7 6 13 3 4 6
11 10 12
22b
6'
7 6 14
76
15b
6
4 7
5 6
12 12
14 6 5 13 3 5 6
12 10 15 6 5 12 3 4 C
Conventional sampler 3 was used at Pt. Petre only. A 15 pm inlet head was used on this sampler. All other samplers used 10pm inlets. Filter edges were damaged during removal from holder. Table 11. Suspended Particulate Matter Loadings (pg/m3) for the Pt. Petre Sampling Site
date 8811118-10 88/11/10-12 88111112-14 88111/22-24 88111124-26 88111/26-28 89103115-17 89103117-19 89/03/ 19-21
conventional sampler 1 2 3
denuder sampler 1 2
9 5
9 13
9 5
10
12
8 14 14 10 9
8 14 31
12
18 34
17 6 17 11 17 14
11
11
20 17 16
9 14
8 13
25
10 12
11
4 11 10
11
8 13
3 9 4 10 8 10 15 15 6 12
inlets) are reported in Table I (for Turkey Lake) and in Table I1 (for Pt. Petre). Inhalable particulate matter concentrations ranged from 3 to 34 pg/m3, reflecting the relatively pristine nature of the two sites. The effect of spreading the wood chips on the ground at the Turkey Lake site may be seen in these results. Consistently higher dust loadings were found in the spring with the conventional sampler fitted with the 15-pm inlet than with the sampler fitted with the 10-pm inlet. Differences in dust loadings between these two samplers were negligible after the deposition of the wood chips. In addition, differences in the particle loadings between the conventional sampler using the 10-pm inlet and the denuder samplers, which were also fitted with 10-pm inlets, were, generally, very small. The volatilization of semivolatile organic compounds from the surface of particulate matter that has been collected on filters (sometimes referred to as "blowoff") has been identified in numerous publications (20-29) as a potentially serious problem, especially when a denuder is used ahead of the filter (30).In both the conventional and the denuder samplers, two Florisil adsorbers were used in series, downstream of each filter, to collect any material which might volatilize from the particulate matter and be carried through the filter by the flowing airstream. The second adsorber was used to collect any components which might break through the first adsorber. The adsorbers and filters were analyzed separately to assess the degree of both blowoff and potential adsorber breakthrough. Neither a-HCH nor y H C H was ever detected on the filter of either the conventional or denuder samplers. The "particle-associated" component was detected exclusively in the adsorbers, downstream of the filters. This was not surprising since both the solid-phase and subcooled liq-
uid-phase vapor pressures of a-HCH, 7-HCH, and HCB Pa range are relatively high (31,32),being in the 10 X at a temperature of 20 "C. Only occasionally, was HCB detected on the filter. In most instances, the first adsorber contained the largest fraction of the mass of each of the target species, with only small quantities occurring in the backup cartridge. On a few occasions, there was substantial breakthrough of HCB and a-HCH to the backup adsorber. This was particularly evident during periods of rainfall and high humidity conditions. Under such conditions, the Florisil in the first adsorber may have become partially deactivated by the moist air, displacing the trapped components to the second adsorber. Lindane, however, was much less subject to breakthrough, perhaps due to the fact that it has the lowest Henry's law constant of the three target compounds. Although it was usually found in the adsorbers, HCB was, occasionally, detected on the filter. Since the vapor phase was removed by the denuder and only the particle-associated components reached the filter, the above observation (that the target species were found predominantly in the adsorbers and not on the filters) strongly implies that these three species (and presumably other similar SVOCs) volatilize from the particles with which they were associated after they are trapped on the filter, are reentrained in the airflow, and are subsequently trapped by the adsorbers. Thus, if an accurate vapor to particle partition ratio is to be determined, it would appear to be necessary to trap the vapor-phase components prior to collecting the particle-phase components so that the contaminants which volatilize from the particles will not, inadvertently, be measured as vapor-phase components, thereby positively biasing the vapor-phase yield. The total mass of each of the target organochlorine contaminants, and the vapor-phase component (?&) of the total mass determined, are reported in Tables I11 (Turkey Lake results) and IV (Point Petre results). For each sampling period, the mean value of the replicate measurements is given, followed, in parentheses, by the number of replicate measurements, and the range (if two replicate measurements were made) or the standard deviation (if three replicate measurements were made). Mean values falling between the detection limit and the quantitation limit are indicated in brackets. To avoid discarding data which were just below the detection limit (the so-called "censored" (33,34)data), values of half the detection limit were substituted for these data and were used to calculate the mean values reported in the tables. Although the method of substitution is not the most desirable method for handling censored data (33),it seemed to be the most logical method in view of our very limited data set. Plots of the log of the concentration vs the reciprocal of the temperature produced negative slopes for both a-HCH and y H C H (see Figure 1). Although there is some scatter in the results, it can be seen that the results from Turkey Lake are not significantly different from those obtained at Pt. Petre. The regression equation for a-HCH was log C = -2590/T + 11.49 and that for y H C H was log C = -2130/T + 9.02, where C is the atmospheric loading of the contaminant (pg/m3) and T is temperature (K). The data for r-HCH, especially that from Turkey Lake, are remarkably similar to the data obtained by Hoff et al. (35) for samples collected at Egbert, ON. Hoffs regression equation for yHCH was log C = -3100/T 12.6 and is shown as the dashed line in Figure 1. However, unlike Hoff s results, in which there was no temperatureconcentration correlation for a-HCH, our results indicated a definite temperature-concentration correlation.
+
Environ. Sci. Technol., Vol. 26, No. 1, 1992
129
Table 111. Total Concentration and Vapor-Phase Component for HCB, a-HCH, and yHCH at Turkey Lake
HCB date
av temp, "C
total," pg/m3
8710518-10 87/05/10-12 87105112-14 87107124-26 87107126-28 87107128-30 87110120-22 87110122-24 87110124-26
11.5 9.4 10.0 19.0 17.5 17.9 1.4 0.9 2.0
97 (2, f3) 81 (2, f4) 71 (2, f l ) 79 (2, f12) 91 (2, f 2 ) 26 (2, f3) 76 (2, f5) 68 (2, f8) 75 (2, f 2 )
mean SD
% Vap
92 96 94 94 96 94 100 100 100
CY-HCH total," pgb3 % Vap 285 (2, f25) 270 (2, f20) 310 (2, f10) 475 (2, f5) 450 (2, f40) 330 (2, f110) 200 (2, f10) 210 (2, f0) 180 (2, f20)
96 *3
93 96 92 87 92 90 100 100 100
r-HCH total,",* pgb3 % Vap 88 (2, f12) 80 (2, f l ) 115 (2, f15) [491 (2, f4) 53 (2, f12) [431 (2, f4) 1231 (2, f3) [261 (2, f0) [291 (2, f 2 )
91 93 91 93 77
aly
3 3 3 10 9 8 9 8 6
81
100 100 100
94 f5
92 f8 "The first number in parentheses is the number of replicate measurements taken and the second is the range of the measurements. bThe values in brackets were above the detection limit but below the auantitation limit. ~~
~
~
~~~~~
Table IV. Total Concentration and Vapor-Phase Component for HCB, a-HCH, and yHCH at Pt. Petre
HCB total," pg/m3
date
av temp, "C
8811118-10 88/11/10-12 88111112-14 88111/22-24 88111124-26 88111/26-28 89103115-17 89103117-19 89/03/19-21
11.2
82 (3, f4)
8.0 9.4 1.6 3.9 8.3 -1.4 -4.9 -1.3
74 (3, f13) 81 (3, f17) 39 (3, f10) 58 (3, f14) 82 (3, f11) 87 (3, f10) 57 (2, f3) 79 (3, f13)
mean SD
% Vap
93 96 99 98 92 97 100 96 98 97 f3
CY-HCH total," pg1m3 % Vap 150 (3, f10) 103 (3, f6) 122 (3, 128) 100 (3, f0) 117 (3, 1 6 ) 330 (3, f36) 71 (3, f13) 60 (2, f0) 59 (3, f7)
88 100 100 100
100 94 97 100 100 98 f4
r-HCH total,"*b pgb3 % Vap [I81 (3, 1 5 ) WIc (3, f6) 1WC(3, f9) PI' (3, f0) WIc (3, f6) [I51 (3, f l ) 1121' (3, f7) WI (2, f5) [8Ic (3, fo)
aIy
100 100 100 100 100 100
8 9 8 13 8 20 6
100
2
100
7
100
100
fO
"The first number in parentheses is the number of replicate measurements taken and the second is the range (if two replicates) or the standard deviation (if three replicates) of those measurements. *The values in brackets were above the detection limit but below the quantitation limit. When one or more of the replicate measurements were below the detection limit, the data below the detection limit were assigned values of half the detection limit. These values were then used to determine the means.
The total mass concentration of HCB, like those for a-HCH and y-HCH, showed no difference between the results obtained at Turkey Lake and Pt. Petre (see Figure 1). However, HCB showed virtually no temperature dependence. Throughout the year, the mean concentration of HCB was 73 pg/m3 (a = 20, n = 9). The total (vapor and particle) mass concentrations for a-HCH, y-HCH, and HCB are comparable to those for measurements made in the Arctic, Antarctic, remote continental and marine environments (2-7,16), and the Great Lakes basin (36). The total mass concentrations of these three organochlorines were independent of the total mass of the particulate matter (correlation less than 0.13) at both sampling locations. All three compounds occurred primarily in the vapor phase at both locations. At Turkey Lake (Table 111), the mean value (over the three different seasons during which measurements were taken) for HCB was 96.3 % (standard deviation a = i2.9), for a-HCH was 94.4% (a = *4.5) and for y-HCH was 91.7% (a = *7.9). At Pt. Petre (Table IV), sampling was carried out only during the winter months. Nevertheless, the mean values determined were very similar to those obtained a t Turkey Lake. The mean vaporphase component for HCB was 96.6% (a = i2.6) while those for a-HCH and y-HCH were 97.6% (a = i4.1) and 100% (a = M),respectively. A t Pt. Petre, where there is the greatest volume of data, the amount of each compound in the vapor phase (y-HCH > a-HCH > HCB) agrees with the order that would be predicted, based upon 130
Environ. Sci. Technol., Vol. 26, No. 1, 1992
the solid-phase vapor pressures (not the subcooled liquid-phase vapor pressures) of the three target compounds. Very little information exists in the literature concerning the vapor/particle distribution of a-HCH, y-HCH, and HCB. Specific reports of vapor/particle measurements of a-HCH and HCB have been made by Bidleman and coworkers (6, 16, 31), who collected air samples using a high-volume sampler fitted with an adsorbent (Polyurethane foam, Tenax-GC or XAD-2 resin) downstream of the filter to trap the vapor-phase material. Those investigators determined that the average particle fraction of a-HCH was 0.08% at 20 "C and 0.4% at 0 "C while the average particle fraction of HCB was 0.1% at 20 "C and 0.7% at 0 "C. However, they recognized that the partitioning between the adsorbent-associated material (operationally defined as the "vapor phase") and the filter-associated material (operationally defined as the "particle phase") determined with their sampling system may be overestimated because of the blowoff effect. When the particulate matter is collected prior to the vapor-phase components, it is not possible to deconvolute the actual vapor- and particle-phase components that existed in the atmosphere at the time of collection. Consequently, they were not able to determine the extent to which blowoff might have affected their results. In Tables I11 and IV, the a / y ratio for each HCH isomer is reported for each measurement period. The a/y ratios determined at Turkey Lake were generally between 3 and 10 whereas those at Pt. Petre, with one exception, were
b.
"1
t 2.5
60
HCB
1
I-
x
N
w
HCB
1 c( -HCH
2.0 1.5 0
.
log(C1=(-2590/T)+l 1.49
U
0)
-0
\
2.0
1%--
I
I
I
I
I
9
m .
..
if-HCH
60
x
0 -5 3.4
3.45
3.5
3.55
3.6
3.65
3.7
3.75
1000x~l/T~KIl Figure 1. Logarithm of the total (vapor and particle phase) mass concentration plotted against the reciprocal of the temperature for HCB, a-HCH, and y-HCH. Data are shown for Turkey Lake (B)and for R. Petre (0). The dashed line for y-HCH is the regression line from Hoff et al. (35).
between 6 and 20, suggesting that the air masses arriving at Pt. Petre were more aged with regard to lindane than those arriving at Turkey Lake. Whether the ageing is due to photochemical transformation during long-range transport, as suggested by Malaiyandi and Shah (37), or due to other environmental factors has not been established. Nevertheless, the a / y ratio should increase with distance from the source(s) of lindane or technical HCH mixtures in which the a / y ratio is typically between 3 and 7 (38). Although the vapor-phase component of HCB does not show any discernible temperature dependence, the vapor-phase components of a-HCH and y-HCH apparently do (see Figure 2). However, the relationships were entirely unexpected. From the figure, it can be seen that the vapor-phase component (%) appears to be greater during the cold weather than during the warmer weather. This is contrary to the predictions of Junge (39) that the particle phase should increase during the colder periods of the year and decrease during the warmer periods. At first, it was suspected either that the denuder was failing to trap the vapor-phase components (allowing the target compounds to pass through the denuder and then to be trapped in the adsorbent cartridges and inadvertently to be measured as particle-phase mass, thus elevating the particle-phase component), or that there were some environmental factors which combined to yield a higher particle-phase (lower vapor) component in the summer than in the winter. As demonstrated previously (19) under extensive laboratory-controlled conditions, the denuders were shown to be effective (better than 99%) in trapping vapor-phase components at a continuous temperature of 26 OC and a
=t: 0
5
10
15
20
Temperature I'CI Figure 2. Percent vapor-phase component of HCB, a-HCH, and yHCH for Turkey Lake (W) and Pt. Petre (0)as a function of average sampling temperature.
relative humidity of 82% over a 24-h period for air concentrations ranging from 400 to 1900 pg/m3 for HCB and from 600 to 2000 pg/m3 for 7-HCH. No denuder breakthrough occurred under these concentrations. During the Turkey Lakes field sampling programs, the highest average temperature was 19.0 "C and the maximum hourly temperature experienced was 27 OC. Since the denuders were operating below the temperature conditions simulated in the laboratory, and since the maximum y H C H and HCB concentrations recorded during field measurements (130 and 100 pg/m3, respectively) were considerably lower than those used in the laboratory tests, component breakthrough was considered to be highly unlikely. One possible explanation for the apparent greater fraction of particle-associated material during the hotter (summertime) periods invokes the concept that high relative humidity, resulting in microdroplets of fog, could scavenge the vapor-phase material. The fog droplets would then be measured as particle-phase material. If the relative humidity had affected the measurements, one would expect to see a statistically significant inverse correlation between the relative humidity and the proportion of the material in the vapor phase. In addition, since y-HCH has a greater aqueous solubility than either a-HCH or HCB, the effect ought to be greater for the y H C H than for the other two components. The average relative humidity for the entire sampling period was determined by averaging the 1-h-average relative humidity measurements obtained throughout the sampling period. The maximum hourly average relative humidity occurring during a particular sampling period was also determined. No correlation was observed between the percent vapor-phase component of any of the target compounds and either the average relative humidity (see Figure 3) or the maximum relative humidity observed during the sampling periods. It thus appears that relative Environ. Sci. Technol., Vol. 26,
No. 1, 1992 131
"1
60
HCB
I
1
$-?
a-HCH, y H C H , and HCB for which the vapor-phase component is not enhanced by volatilization (blowoff)from the particle phase. The results suggest that the vaporphase component of a-HCH, r-HCH, and HCB is marginally lower (by a few percent) than those reported by Bidleman (6, 13, 31). Relative humidity does not appear to have any significant effect upon the vapor/particle distribution of a-HCH, y-HCH, and HCB in the atmosphere, nor does it appear to have any effect upon the collection efficiency of the GAP sampler. Acknowledgments
60
We thank Dr. L. Reynolds and I. Bowen for performing the chemical analyses.
i
Registry No. HCB, 118-74-1; a-HCH, 319-84-6; y-HCH, 5889-9.
Literature Cited 100 80
Y-HCH 6o
t
30
1 40
50 60 70 80 Average Relative Humidity (%)
90
Figure 3. Percent vapor-phase component of HCB, a-HCH, and yHCH for Turkey Lake (M) and R. Petre (0) as a function of the average relative humidity.
humidity has neither an adverse effect upon the operation of the GAP sampler nor a significant effect upon the vapor/particle partition of HCB and CY- and 7-HCH in the atmosphere. Other possible explanations for this evident trend are, however, possible. For example, in the summer, the components may have been associated with very small particles or aerosols. Differences in airborne particle composition between seasons could also affect the relationship. Confidence that the GAP samplers were not suffering vapor-phase breakthrough, and the lack of correlation of the vapor-phase components with relative humidity, have left us without a satisfactory explanation for this apparent inverse correlation of vapor-phase component with temperature. Experimental error and method variability do not entirely account for this observation. However, the data set is very limited. A summer sampling program has just been completed at Pt. Petre and preliminary data suggest that this observation may, indeed, be real. Further field measurements will likely be required to resolve this conundrum. HCB, unlike the HCH isomers, showed no obvious variation in the vapor/particle partition with the time of year (or temperature). HCB has a lower vapor pressure than either of the HCH isomers and was found, at both locations, to exist approximately 96.5% in the vapor phase regardless of temperature or time of year. This would suggest that the sources of HCB and the HCH isomers are quite different. Conclusions
The vapor- and particle-phase components of HCB, a-HCH, and 7-HCH have been determined at two locations in Ontario using the GAP sampler. These are the first reported vapor- and particle-phase measurements for 132
Environ. Sci. Technol., Vol. 26, No. 1, 1992
A Perspective of the Problem of Hazardous Substances in the Great Lakes Basin Ecosystem-Appendix-Background Reports. Report to the International Joint Commission, Great Lakes Science Advisory Board, Windsor, ON, Canada, 1980. Atlas, E. L.; Giam, C. S. Science (Washington D.C.) 1981, 211, 163. Bidleman, T. F.; Leonard, R. Atmos. Enuiron. 1983, 16, 1099. Tanabe, S.; Hidaka, H.; Tatsukawa, R. Chemosphere 1983, 12, 277. Oehme, M.; Ottar, B. Geochem.Res. Lett. 1984,11,1133. Bidleman, T. F.; Wideqvist, U.; Jansson, B.; Soderlund, R. Atmos. Enuiron. 1987, 21, 641. Pacyna, J. M.; Oehme, M. Atmos. Enuiron. 1988,22,243. Swain, W. R. J . Great Lakes Res. 1978, 4, 398. Eisenreich, S. J.; Looney, B. B.; Thornton, J. D. Enuiron. Sci. Technol. 1981, 15, 30. Voldner, E. C.; Schroeder, W. H. Atmos. Enuiron. 1989,23, 1949. Czuczwa, J. M.; Hites, R. A. Enuiron. Sci. Technol. 1986, 20, 195. Lockerbie, D. M.; Clair, T. A. Bull. Enuiron. Contam. Toxicol. 1988, 41, 625. Swackhamer, D. L.; McVeety, B. D.; Hites, R. A. Enuiron. Sci. Technol. 1988, 22, 664. Gregor, D. J.; Gummer, W. D. Enuiron. Sci. Technol. 1989, 23, 561. Bidleman, T. F.; Patton, G. W.; Walla, M. D.; Hargrave, B. T.; Vaas, W. P.; Erickson, P.; Fowler, B.; Scott, V.; Gregor, D. J. Arctic 1989, 42, 307. Bidleman, T. F.; Billings, W. N.; Foreman, W. T. Enuiron. Sci. Technol. 1986, 20, 1038. Duinker, J. C.; Bouchertall, F. Enuiron. Sci. Technol. 1989, 23, 57. Atlas, E.; Giam, C. S. Water,Air, Soil Pollut. 1988,38, 19. Lane, D. A.; Johnson, N. D.; Barton, S. C.; Thomas, G. H. S.; Schroeder, W. H. Enuiron. Sei. Technol. 1988,22,941. Commins, B. T. Natl. Cancer Inst., Monogr. 1962,9,225. Pupp, C.; Lao, R. C.; Murray, J. J.; Pottie, R. F. Atmos. Enuiron. 1974, 8 , 915. Cautreels, W.; Van Cauwenberghe, K. Atmos. Enuiron. 1978, 12, 1133. Handa, T.; Kato, Y.; Yamamura, T.; Ishii, T.; Suda, K. Enuiron. Sei. Technol. 1980, 14, 416. Kbnig, J.; Funcke, W.; Balfanz, E.; Grosch, B.; Pott, F. Atmos. Environ. 1980, 14, 609. Thrane, K. E.; Mikalsen, A. Atmos. Enuiron. 1981,15,909. Galasyn, J. F.; Hornig, J. F.; Soderberg, R. H. J. Air Pollut. Control. Assoc. 1984, 34, 57. Nikolaou, K.; Masclet, P.; Mouvier, G. Sei. Total Enuiron. 1984, 36, 383. Van Vaeck, L.; Van Cauwenberghe, K. Atmos. Enuiron. 1984, 18, 323.
Environ. Sci. Technol. 1992,26, 133-138
Lewis, R. G. In Proceedings of the EPAIAPCA Symposium on Measurement of Toxic Air Pollutants; EPA Report No. 60019-86-013, APCA Publication VIP-7; 1986; pp 134-141. Zhang, X.; McMurry, P. H. Environ. Sci. Technol. 1991, 25, 456. Bidleman, T. F.; Foreman, W. T. In Sources and Fates of Aquatic Pollutants; Hites, R. A., Eisenreich, S. J., Eds.; Advances in Chemistry Series 216; American Chemical Society: Washington DC, 1987; pp 27-56. Mackay, D.; Shiu, W. Y. J. Chem. Ref. Data 1981,10,1175. Helsel, D. R. Environ. Sci. Technol. 1990, 24, 1767. Newman, M. C.; Dixon, P. M. Am. Enuiron. Lab. 1990,2(2), 26.
(35) Hoff, R. M.; Muir, D. C. G.; Grift, N. P. Submitted to
Environ. Sci. Technol. (36) Rapaport, R. A.; Eisenreich, S. J. Environ. Sci. Technol. 1988, 22, 931. (37) Malaiyandi, M.; Shah, S. M. J.Environ. Sci. Health A 1984, 19, 887. (38) Hargrave, B. T.; Vass, W. P.; Erickson, P. E.; Fowler, B. R. Tellus 1988,40B, 480. (39) Junge, C. E. Adv. Environ. Sci. Technol. 1977, 8, 7.
Received for review October 10, 1990. Revised manuscript received April 3, 1991. Accepted July 25, 1991.
Determination of Sugars in Unconcentrated Seawater and Other Natural Waters by Liquid Chromatography and Pulsed Amperometric Detection Kenneth Mopper, Chrlstopher A. Schultz, Llonel Chevolot,t Clalre Germah,$ Rene Revuelta,s and Rodger Dawsong Chemistry Department, Washington State University, Pullman, Washington 99 164-4630
Reducing and nonreducing sugars, including sugar alcohols, were determined in seawater and other natural waters without preconcentration steps required in past studies. Sugars were separated by anion-exchange chromatography at pH >11 followed by detection by triplepulsed amperometry. Prior to injection, seawater samples were rapidly desalted either by use of a mixed bed of anion- and cation-exchange resins in carbonate and hydrogen forms, respectively, or by use of cation-exchange resin in silver form, to remove chloride, followed by precipitation of sulfate as the barium salt. Concentrations of individual sugars in seawater samples were usually 11followed by electrochemical detection in oxidative pulsed amperometric mode (17-20), Natural water samples, including seawater, were injected directly after a simple desalting step. Sugars in seawater could be detected down to 2-10 nM (or 0.4-0.8 pmol per injection) without preconcentration steps that limited previous studies. Experimental Section Reagents and Standards. All solutions and HPLC mobile phases were prepared with fresh deionized water from a Millipore Q water system equipped with an Organex activated carbon attachment (Millipore, Milford, MA). HPLC mobile phases were made by diluting a lowcarbonate sodium hydroxide solution (50% wjw; Fisher, Pittsburgh, PA). A barium hydroxide solution (0.3 M; Fisher) was used for precipitation of sulfate in samples. All other chemicals were of reagent grade. Analytical grade ion-exchangeresins were obtained from Biorad (Richmond, CA) and were converted to the desired forms in accordance with Biorad's recommended procedures. Sugar standards were obtained from Sigma (St. Louis, MO) and Aldrich (Milwaukee, WI) as the purest available grades. Standard sugar stock solutions, 1-10 mM, were prepared in 20% aqueous acetonitrile (HPLC grade, Burdick, and Jackson, Muskegon, MI). The stocks were stable for at least 2 months if stored refrigerated in tightly stoppered bottles.
0 1991 American Chemical Society
Environ. Sci. Technol., Vol. 26, No. 1, 1992
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