Environ. Sci. Technoi. 1991, 25, 1249- 126 1
Curtis, G. P.; Roberta, P. V.; Reinhard, M. Water Resour. Res. 1986,22,2059-2067. Crank, J. The Mathematics of Diffusion, 2nd ed.; Oxford University Press: Oxford, U.K., 1975. Brusseau, M. L.; Rao, P. S. C. Chemosphere 1989, 18, 1691-1706. Ball, W. P.; Goltz, M. N.; Roberts, P. V. Environmental Engineering: Proceedings of the 1990Specialty Conference on Environmental Engineering, Arlington, VA; American Society of Civil Engineers: New York, 1990;pp 307-313. Mathews, A. P.;Zayas, I. J . Enuiron. Eng. (N.Y.)1989,115, 41-55. Ruthven, D. M.; Loughlin, K. F. Chem. Eng. Sci. 1971,26, 577-584. Cooney, D. 0.;Adesanya, B. A.; Hines, A. L. Chem. Eng. Sci. 1983,38, 1535-1541. Wu, S.-C.;Gschwend, P. M. Water Resour. Res. 1988,24, 1373-1383. Fong, F. K.; Mulkey, L. A. Water Resour. Res. 1990,26, 843-853.
(52) Reid, R. C.; Prausnitz, J. M.; Poling, B. E. The Properties of Gases and Liquids; McGra.w Hill Book Co.: New York, 1987. (53) Wood, W. W.; Kraemer, T. F.; Hearn, P. P., Jr. Science 1990,247,1569-1572. (54) Frisch, H. L. Polym. Eng. Sci. 1980,20,2-13. (55) Wilke, C. R.; Chang, P. AZChE J . 1955,I , 264-270. (56) Hayduk, W.; Laudie, H. AZChE J . 1974,20,611-615. (57) Nkedi-Kizza,P.; Brusseau, M. L.; Rao, P. S. C.; Hornsby, A. G. Enuiron. Sci. Technol. 1989,23,814-820. Received for review August 14,1990.Revised manuscript received February 22,1991. Accepted March 14,1991.This research was funded by the U.S. Environmental Protection Agency’s Office of Exploratory Research through Grant R813844. The article has not been subjected to EPA review and therefore does not necessarily reflect their views. Additional funding from the American Water Works Association (Abel Wolman Fellowship Fund) and the ARCS Foundation of Northern California is also gratefully acknowledged.
Spatial and Temporal Patterns of Organic Contaminants in Wet Precipitation in Atlantic Canada Guy L. Brun,’ Geoff D. Howell, and Hugh J. O’Nelll
Environment Canada, Conservation and Protection, Inland Waters Directorate, Water Quality Branch, P.O. Box 86 1, Moncton, New Brunswick, E1C 8N6, Canada Wet precipitation samples were collected on a monthly basis from three locations in Atlantic Canada for the period 1980-1989 and analyzed for organochlorine pesticides, total polychlorinated biphenyls (PCBs), chlorinated benzenes, and polynuclear aromatic hydrocarbons (PAHs). The compounds most commonly detected included the pesticide lindane (7-HCH) and its decomposition product aHCH, fluoranthene, benzo[a]pyrene,benzo[b]fluoranthene, benzo[k]fluoranthene, and PCBs. Statistical analysis of a-HCH and y H C H data indicated a significant decrease in concentration of these compounds after 1983, probably the result of curtailing the agricultural use of lindane in North America and on other continents. Seasonal patterns were observed with maximum concentrations/loadings occurring during the spring and fall. Fluoranthene was the dominant PAH compound and was detected in almost every sample. Fluoranthene and other PAHs were shown to follow seasonal patterns, with increasing concentrations during the colder months of the year (December to April). Spatial influences were also observed, indicating both localized and long-range atmospheric source inputs. Abnormally high annual mean concentrations of PCBs ranging between nondetectable levels and 0.220 pg/L were measured during the 1981-1986 period at the Prince Edward Island station. Spatial variations for PCBs in the Atlantic Region were significant and attributed in part to localized source inputs. Seasonal patterns similar to the PAHs were also observed. Concentrations dropped to nondetectable levels after 1984 a t all sites with the exception of a few sporadic observations. Introduction The atmosphere is recognized as an important pathway in the global transport and deposition of anthropogenic organic chemicals. Pollutants originating from various processes such as industrial emissions, energy production/consumption, agricultural/forestry practices, and waste incineration have been shown to disperse in the atmosphere. These chemicals may be transported by air 0013-936X/91/0925-1249$02.50/0
masses and winds over long distances to finally deposit on land and water during precipitation events. Semivolatile organic chemicals are particularly amenable to this type of dispersion mechanism. Hexachlorocyclohexanes (HCHs), polychlorinated biphenyls (PCBs), and polyaromatic hydrocarbons (PAHs), recognized as ubiquitous environmental contaminants, have been found in remote areas thousands of kilometers away from their nearest known sources (1, 2). Studies have recently shown that atmospheric inputs to ombrotrophic peat bogs in North America have closely matched the production, use, and subsequent banning of DDT and PCBs on the continent, an indication that the atmosphere reacts rapidly to such changes (3,4). Similarly, long-range atmospheric transport was proposed as the principle dispersal mechanism accounting for the presence of a-HCH, r-HCH, and PCBs in isolated lakes of southern Labrador in Canada and in snow and air samples from the Canadian and Norwegian Arctic (5-7). Atmospheric deposition has been recognized for well over a decade as a principal pathway for anthropogenic toxic chemicals to the Great Lakes (8, 9). Measurable concentrations of polychlorinated dibenzop-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) were recently observed in arctic ringed seal (10). Atmospheric transport was suggested as a probable pathway. These findings are interesting in the sense that evidence now exists indicating that this extremely toxic group of chemicals could also be dispersing on a global scale (10). PCDDs and PCDFs have been found elsewhere in ambient air and rainwater samples (11,12). Information on the atmospheric deposition of toxic organics in Atlantic Canada is very sparse. With its small population base, the Atlantic Canadian environment is considered relatively pristine with respect to organic chemicals and the effects of industrialization; however, because of the long-range atmospheric transport phenomena there has been mounting concern regarding influxes of toxic organics to the region. Identification of organo-
0 1991 American Chemical Society
Environ. Sci. Technol., Vol. 25, No. 7, 1991
1249
NEW BRUNSWICK
MAINE \
Figure 1. Location of wet precipitation collectors.
chlorine pesticides (OCs) and PCBs was first reported on samples collected through the Canadian Network for Sampling Organics in Precipitation (CANSOC), (13). The network consisted of 12 sites located across the country in rural and semiurban areas and was operational during the period 1977-1980. Data from two Atlantic sites indicated the influx of hexachlorocyclohexanes, PCBs, and traces of other chlorinated pesticides into the region. Following the disbandment of the national network, our regional branch of Environment Canada established three new sites in the region and expanded the analytical protocol to include PAHs and chlorinated benzenes (CBs) in addition to PCBs and OCs. This effort constituted, to the best of our knowledge, a first attempt to establish a precipitation monitoring network for toxic organics in Atlantic Canada. Very few monitoring studies have been documented. A year-round monitoring network was established using specially designed electronically controlled samples for collection of rain and snow during 1986 in the Great Lakes basin (8), permitting more refined estimates of atmospheric loading. On a long-term basis, there are relatively few studies that have reported on the spatial and temporal patterns of organics in precipitation, probably a result of sampling difficulties and relatively high costs associated with this type, of program (8, 14-16). This paper reports on four groups of toxic organic compounds determined in monthly composite samples of rain and snow collected from three sites in Atlantic Canada during the period 1980-1989. Long-term trends, seasonal patterns, and spatial characteristics are discussed.
Methods Sampling. Sampling of wet precipitation was initiated in the fall of 1980 at two sites in Atlantic Canada, namely, Kejimkujik National Park, in Nova Scotia (44’25’59” N, 65O12’00’’ W), and Ellerslie, in Prince Edward Island (46’36’50” N, 63’54’34” W). A third sampler was installed at Jackson, NS (45’35’29” N, 63’50’04” W) in late 1984. 1250 Envlron. lid. Technol., Vol. 25, No. 7, 1991
The sampling stations are shown in Figure 1. The Ellerslie, PEI, site was located on properties belonging to the Federal Department of Fisheries and Oceans (DFO) in an area that would be classed as rural/agricultural. The site was in operation from 1980 until closure of the DFO station in 1986. The Kejimkujik station is in Kejimkujik National Park in proximity to an Environment Canada, Atmospheric Environment Service (AES) CAPMoN (Canadian Air and Precipitation Monitoring Network) station. This site is the most remote from human habitation and is still in operation. The Jackson NS, station is located in a rural area at the DFO Cobequid Fish Hatchery also near a CAPMoN station and was activated in 1984. A second collector was installed at Jackson in 1988, 30 m from the other collector for intersampler comparison purposes. Site selection was critical and based on certain criteria to help ensure the integrity of this long-term monitoring effort. Primarily this meant that personnel had to be available at the sampling site to assume responsibility for tending the collectors, making minor repairs, and reporting any malfunctions. Areas removed from urban influence and industrial activities were given preference. Collectors were installed as far as possible from roads, buildings and other direct human input sources. The CAPMoN sites, for example, conform with a set of objective siting criteria designed to minimize local site influences (17). Each site was further equipped with a precipitation gauge (AES) for recording rainfall. The CAPMoN collectors are used for monitoring long-term major ion precipitation chemistry. Sampling apparatus consisted of modified Sangamo Type-A precipitation collectors (Sangamo Co. Ltd., 215 Laird Dr., Toronto, ON). The modification to the collectors consisted in replacing the PVC buckets with stainless steel buckets for sample collection (13). The buckets were 21 cm X 21 cm X 37 cm deep, providing a total capacity of 16.3 L. Their use eliminated sample cross contamination and interferences that could emanate from exposing the samples to plastic. The Sangamo precipita-
tion collector is a double bucket collector that may be used for both wet and dry deposition sample collection. A moisture senaing grid is used in conjunction with a solidstate control panel to operate the motor-driven cover, which rests over the wet bucket during dry periods. At the onset of a precipitation event, the cover moves over on top of the dry collection bucket until the end of the event at which time the cover moves back over the wet bucket. The sensing grid is heated to ensure prompt closure after an event and to eliminate the effects of fog or dew. On-site personnel instructed on the proper sampling procedures collected the wet precipitation samples on a weekly basis or after a significant event (i.e., >1cm of rain). The samples were carefully transferred to 4-L amber glass bottles precleaned in the laboratory specifically for trace organic sampling. At month end, the aggregated samples were labeled and shipped to the laboratory for analysis. Samples were stored in the interim at 4 "C both at the sampling station and in the laboratory. The sampler buckets were replaced with clean buckets and the used ones shipped to the laboratory for thorough cleaning. The Sangamo sampler and sampling protocol used in the network were designed to conform with equipment and procedures in use by other networks in Canada at the time of inception (13). Extraction. Extractions were performed in glass separatory funnels by shaking 100 mL of hexane for each liter of sample. This process was repeated once and the combined extracts were dried through a column packed with anhydrous sodium sulfate. When necessary, cleanup of extracts was performed by silica gel column fractionation. Extract volume was reduced to a final volume of 5.0 mL with a rotary evaporator. The extract was then divided in half, one portion for gas chromatographic analysis of chlorinated compounds, and the other portion for PAH determination. Hexane was replaced with acetonitrilewater in the PAH fraction for HPLC analysis. Quantitation. The chlorinated compounds were analyzed on Varian 3700 and 6000 gas chromatographs equipped with splitless injectors, capillary columns, nickel-63 electron capture detectors, and chromatography work stations. In mid-1982, glass capillary columns (SCOT) were replaced with fused-silica capillary columns. Sample extracts were analyzed by using a low polarity column such as DB-5 (J&W Scientific, 30 m X 0.25 mm i.d., 0.25 pm fat.)and an intermediate polarity column such as SPB-608 (Supelco, 30 rn X 0.25 mm i.d., 0.25 pm film thickness). Results were reported only if a chromatographic peak confirmed on both columns. For optimal OC and PCB determination, the column oven was programmed at an initial temperature of 190 "C for 2 min, then ramped to 240 "C at a rate of 7 "C/min, and held for 15 min. For CBs, the column oven temperature was increased from 50 to 90 "C at a rate of 25 "C/ min, then to 210 "C at 4 "C/min, and finally to 240 "C at 15 "C/min. The injector and detector temperatures were set at 230 and 320 "C, respectively. The injection volume was 1 pL and helium was used as carrier gas. The instrument conditions given here were modified slightly from time to time to accommodate new columns (i.e,, glass vs fused silica), liquid phases, and varying sample compositions. The instruments were calibrated by injecting working standard solutions at concentrations ranging between 10 and 500 pg/pL, depending on degree of chlorination of the compounds. Response factors were then calculated by using pee.k areas. Sample concentrations were obtained
by applying the respective response factors of standards to peak area measurements from sample chromatograms. Blanks were analyzed concurrently with samples to ascertain purity of solvents/reagents and cleanliness of glassware and apparatus. Detectable responses were subtracted from the sample responses. Original methods are described in greater detail elsewhere (18). PCBs were quantitated against a standard mixture consisting of arochlors 1242, 1254, and 1260 (1:l:l) at a total concentration of 600 pg/pL. Results were reported as total arochlors. Procedures have been described elsewhere (19, 20). PAHs were analyzed by using a Spectra Physics SP 8OOO HPLC (prior to 1988) and a Varian Vista 5500 HPLC system. Both instruments incorporated an automatic sample injector (1O-pL loop), temperature-controlled oven (30 "C), ternary solvent-pumping system, fluorescence detector (Schoeffel970 and Kratos Spectroflow 980, respectively), and a chromatography workstation. Extracts were analyzed on a Perkin-Elmer reverse-phase column (HC-ODS-SIL-X, 10 pm, 0.25 cm i.d. X 25 cm) in conjunction with an RP-8 Spheri-10 precolumn (Brownlee Laboratory). Two columns were used in series on the Vista 5500 instrument to improve peak resolution. Gradient elution was performed starting with a 6040 (acetonitrilewater) mobile phase at 1.0 mL/min, gradually increasing to 100% acetonitrile (convex gradient) at time 20 min and then at a flow rate of 1.5 mL/min from time 21 to 27 min. At the end of the run the instrument was reset to initial conditions to stabilize for 10 min prior to injection of the next sample. The excitation wavelength was set at 280 nm (7-54 filter) with a 370-nm cutoff filter for emission (Spectra Physics 8000). The fluorescence detector on the Vista 5500 HPLC was programmed for automatic excitation wavelength selection during the run: 265 nm initially, 280 nm at 11.5 min, 260 nm at 15 min, and 280 nm at 19.3 min. Working standards ranging between 3 and 30 pg/pL were used for calibration purposes after every fifth or sixth injection. Six PAHs (Table I) listed by the World Health Organization were monitored (21). Procedural blanks were analyzed and treated as described for GC methods. Positive identification of residues was performed on selected samples by gas chromatography-mass spectrometry (GC-MS). Samples collected early in the project (1980) were analyzed by an external laboratory using a Finnigan 4000 series GC-MS system equipped with a splitless injector and SE-30 (30 m) capillary column. The following compounds were screened on selected ion monitoring mode by use of the specified ions: fluoranthene ( m / e 202), PCBs ( m / e 256,292,326,360,3961,and a-HCH ( m / e 109,181,183). A Hewlett-Packard 5790A gas chromatograph-mass selective detector system was also used in this laboratory to confirm the presence of specific PAHs in selected samples. The instrument was equipped with a split-splitless injector (250 "C, purge at 1.5 min) and a 30-m DB-1 fused-silica column (0.25 mm i.d., 0.25 pm film thickness). The temperature program consisted of an initial hcld of 2 min at 60 "C, a ramp at a rate of 25 "C/min to 150 "C with a hold of 2 min, followed by a ramp at 10 "C/min to 250 "C (15-min hold), and finally to 280 "C (6-min hold) at 10 "C/min. Selected ion monitoring mode was performed and only those peaks falling inside a 5% retention time window were considered positive. Method Performance. Samples were analyzed for four groups of organic compounds: OCs, PCBs (as total arochlors), CBs, and PAHs. Individual analytes with limits of detection, mean recoveries from spiked water, and precision of the analytical methods are listed in Table I. Envlron. Scl. Technol., Vol. 25, No. 7, 1991 1251
Table I. Limits of Detection, Recoveries, and Reproducibilities of Analytical Methods
compound
LOD,O pg/L
mean recovery? %
Organochlorine Pesticides a-HCH 0.001 107 (0.050) Y-HCH 0.001 104 (0.054) aldrin 0.001 93.6 (0.056) hcptcichlor 0.001 103 (0.053) heptachlor epoxide 0.001 96.0 (0.056) a-chlordane 0.005 107 (0.049) y-clordane 0.005 99.7 (0.050) a-endosulfan 0.01 101 (0.064) @-endosulfan 0.01 105 (0.101) dieldrin 0.001 102 (0.053) endrin 0.01 110 (0.095) p p’-DDT 0.001 110 (0.135) O,P ’-DDT 0.001 102 (0.094) FI ,JI ’-DDE 0.001 101 (0.051) ~J,~’-DDD 0.001 120 (0.088) p,p’-methoxychlor 0.01 105 (0.175) m rex 0.001 67.7 (0.146) arochlors (total) (1242:1254:1260)
PCBs 0.005
Table 11. Variation of Results in Precipitation Samplesa Taken from Duplicate Collectors at Jackson. NS
3.1 1.6 2.7 4.6 2.2 3.3 2.3 1.1
3.1 2.1 9.5 10.1 4.5 2.0 4.2 9.5 8.3
95.2 (3.15)
5.7
Chlorinated Benzenes 1,3-dichlorobenzene 0.02 70 (0.150) l,4-dichlorobenzene 0.02 76 (0.200) 1,2-dichlorobenzene 0.02 83 (0.150) 1,3,5-trichlorobenzene 0.004 76 (0.025) 1,2,4-trichlorobenzene 0.004 83 (0.040) 1,2,3-trichlorobenzene 0.004 79 (0.015) 1,2,3,5-tetrachlorobenzene 0.002 86 (0,010) 1,2,4,5-tetrachlorobenzene 0.002 86 (0.010) 1,2,3,4-tetrachlorobenzene 0.002 78 (0.010) pentachlorobenzene 0.002 87 (0.005) hexachlorobenzene 0.002 86 (0.005)
13.3 14.5 15.3 8.4 15.1 11.8 9.3 9.3 8.6 4.6 2.3
Polynuclear Aromatic Hydrocarbons fluoranthene 0.004 117 (0.049) 0.002 107 (0.031) benzo[ b ]fluoranthene 0.001 101 (0.021) benzo [k ]fluoranthene benzo [a ]pyrene 0.002 135 (0.021) 71.3 (0.152) benzo[ghi] perylene 0.02 indeno(l,2,3,cd)pyrene 0.02 92.3 (0.150)
9.7 3.4 5.4 5.0 12.5 8.2
“he limits of detection are based on a sample volume of 1.0 L. *Spike concentrations (in parentheses) are in micrograms per liter; n = 10.
The recoveries observed are typical of those obtained from routine spiking of pure water during the batch processing of samples in the laboratory. Although mean recoveries were generally very good for all compounds, CB recoveries tended to be relatively low, ranging between 70% and 87%. This was attributed to losses during the concentration/evaporation procedure of these relatively more volatile compounds. Similarly, higher coefficients of variation were observed for CBs, specifically the dichlorinated and trichlorinated compounds. The precision seems to improve as the degree of volatility decreases. The limits of detection (LODs) reported are based on a fixed sample volume of 1 L and a final extract volume of 5.0 mL. Their determination was performed by observing the minimum concentration required to produce a peak with a signal to noise (S:N) ratio of 2:l (OCs and PCBs) or established as 2 times the standard deviation (PAHs and CBs) from the measurement of analyte standard solutions (n = 10). The LODs should be interpreted with caution and considered only as general indicaton of sensitivity with inherent limitations. The analysis of variable precipitation volumes compromises even more their limited usefulness. As a general rule, for purposes 1252
Envlron. Scl. Technol., Vol. 25, No. 7, 1991
me
CV, % volume a-HCH r-HCH heptachlor a-endosulphan P-endosulphan 1,4-dichlorobenzene fluoranthene benzo[ blfluoranthene benzo[k]fluoranthene benzo [a ]pyrene
4771 (18) 0.0042 (18) 0.0013 (11) 0.0006 (2) 0.0008 (1) 0.0006 (2) 0.13 (2) 0.0081 (15) 0.0018 (9) 0.0015 (5) 0.0014 (6)
4681 (18) 0.0039 (18) 0.0013 (10) 0.0009 (1) 0.0008 (1) 0.0006 (2)
-1.9 -7.1
0.0078 (14) 0.0020 (9) 0.0013 (5) 0.0014 (3)
-3.7
0
50 0 0 11
-13 0
‘Units for all parameters are in micrograms per liter except volume, which is in milliliters. Period of sampling is from October 1987 to June 1989. (XB - f A ) 1 0 0 / f & f~and XB are the means of all collector A and B values, respectively.
of reporting sample values near the LOD, only discernible peaks falling within the correct retention time windows on two different polarity columns and yielding a t least a 2:l (S:N) ratio after blank correction were reported. Table I1 shows the mean concentrations for individual parameters detected in samples from the paired collectors installed a t Jackson for the period October 1987 to June 1989. Close agreement was obtained for most of the compounds except heptachlor. The heptachlor levels were very close to the limit of detection and there were very few positive observations made, which probably accounts for the large variation. The presence of 1,4-dichlorobenzene in two samples from collector A and nondetectable levels in collector B was attributed to laboratory contamination, as dichlorobenzenes were randomly detected in the laboratory blanks. The problem, it was found, emanated from contaminated air in the building. The sample volumes correlated very well, with collector A intercepting approximately 1.9% more than collector B. The collection efficiency of the Sangamo collector compared fairly well when measured against the standard rain gauges. The annual precipitation amounts estimated from sample volumes ranged between 77% and 94% of the standard precipitation gauge measurements. This is analogous with previous findings that amounts of precipitation collected with automated samples of this type tend to be biased low (22).
Results and Discussion Analytical results indicated that polynuclear aromatic hydrocarbons, hexachlorocyclohexane isomers, and polychlorinated biphenyls were present in precipitation on a frequent basis. Heptachlor, a-chlordane, a-endosulfan, @-endosulfan,and aldrin were reported occasionally a t concentrations near the limit of detection. Residues of DDT were detected on only two occasions, both at Ellerslie. For the September 1981 and May 1983 composite samples, levels of 0.004 and 0.001 pg/L, respectively, were reported. Most of the chlorinated benzenes excluding hexachlorobenzene were detected, but only on a sporadic basis. In view of this, discussion of the study will focus on PAHs, HCH isomers, and PCBs. Polynuclear Aromatic Hydrocarbons. Quality assessment in the laboratory is an important element in judging analytical performance and validity of results. Table I11 summarizes the results obtained from an interlaboratory quality control study for PAHs in water using the reported method (23). The concentrations ranged
Table 111. Resultsa of Interlaboratory Quality Control Study for PAHs in Waterb
F
sample no. 1 (blank) 2 3 4 5 6 (blank)
0.006 0.108 0.478 0.560 0.423
NbIF 0.002 0.117 0.547 0.922 0.580
(111) (98.0) (71.7) (86.7)
WkIF
(103) (95.8) (96.8) (102)
ND
ND
WaIP
0.079 (72.3) 0.400 (73.3) 0.674 (74.1) 0.466 (85.3)
0.003 0.082 0.349 0.862 0.396
ND
ND
0.001
ND
ND (106) (89.9) (89.0) (103)
0.097 0.539 0.839 0.531
(82.4) (91.5) (71.3) (90.2)
ND
I
cl
0
'
1
'
:
'
:
'
I
'
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0.113 (108) 0.650 (124) 1.01 (96.4) 0.710 (136)
ND
I, Concentrations expressed in micrograms per liter; values in parentheses represent percent of study design values. 0.24
B[ghi]P
I(l,2,3-cd)Py
* ND, not detected.
t
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Flgure 2. Fiuoranthene concentration in precipitation from three study sites in the Atlantic Region.
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*
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t
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- . - A , - Kejiakujik Jackson
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Flgure 3. Benzo[a Ipyrene concentration in precipitation from three study sites in the Atlantic Region.
between 71.3% and 136% of the design values for the compounds of interest. In-house precision was demonstrated by comparing results of duplicate samples 3 and 5. The deviations ranged between 1.3% for indeno[ 1,2,3-cd]pyrene and 13.1% for benzo[a]pyrene. Sample 1 was a laboratory-purified water blank and sample 6 a groundwater blank. The results for the sample 1 blank indicated the presence of four compounds at concentrations at, or very close to, the limit of detection. Conversely
these PAHs were not detected in the groundwater blank by this laboratory. Considering that approximately half of the 19 laboratories participating in the study obtained similar results, this may suggest that the groundwater blank was cleaner than the laboratory-purified water, especially if the latter was drawn from a source of poor quality water. Steps were taken throughout the study to avoid the possibility of reporting false positives because PAHs deEnviron. Sci. Technoi., Voi. 25, No. 7, 1991
1253
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Figure 4. Benzo[k]fluoranthene concentration in precipitation from three study sites in the Atlantic Region.
t
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t
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t I
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Flgure 5. Benzo[b ]fluoranthene concentratlon in precipltation from three study sites in the Atlantic Region.
tected in precipitation (Figures 2-5) were often very low in concentration and near the LOD. Typical precautions included concurrent analysis and correction for procedural blank responses and maximization of sensitivity by analyzing larger sample volumes in contrast to l-L subsamples, effectively improving the LOD. Specifically, only 4.4% of the 224 samples analyzed were under a volume of 1.0 L. The mean monthly sample volumes over the course of the study for Ellerslie, Kejimkujik, and Jackson were 2.87, 4.43, and 4.01 L, respectively. Figure 6 illustrates the mean monthly precipitation volumes from these sites. The largest variabilities were observed for the month of June a t Jackson and the month of February a t Ellerslie. Line graphs for the concentration of individual PAHs in relation to time of collection a t each of the three sites are presented in Figures 2-5. Figure 2 shows fluoranthene concentrations at Elleslie, Jackson, and Kejimkujik while Figures 3-5 illustrate benzo[a]pyrene, benzo[k]fluoranthene, and benzo[ blfluoranthene concentrations for the same locations. Figure 7 illustrates the loading of total 1254 Envlron. Scl. Technol., Vol. 25, No. 7, 1991
PAHs (sum of six PAHs) observed at each site. The abscissa indicates the period of record for the operation of a given sampling location. These figures indicate without exception that the maxima occur during the colder portion of the year, i.e., November to April. Ordinal ranks of monthly median values for each PAH were used to construct a series of fence diagrams, which are presented in Figure 8. The median concentration for each parameter was calculated on a monthly basis and ranked on a scale of 1 to 12. The vertical bar for each month represents the concentration relative to the other months of the year. This results in a figure that can display patterns and relationships without the confines of varying concentration ranges. These fence diagrams clearly illustrate that regardless of the concentrations detected there is a yearly minimum during the summer months with increasing concentrations during the November to April period for all parameters at all sites. Two other PAHs, indeno(1,2,3-cd)pyrene and benzo[ghi]perylene, were very rarely detected in wet precipitation, but when they were, it was
-
10000
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8000
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tively close between sites. The yearly concentration maxima observed at Ellerslie are due to smaller precipitation amounts collected for the specific sampling periods. The total PAH loading for the period 1980-1986 was found to be 14.5 and 11.5 pgm-2.year-1 at Ellerslie and Kejimkujik, respectively, a difference of approximately 26%. The mass loadings over the entire period of record were estimated at 10.4 and 11.1pgm-2.year-1for Kejimkujik and Jackson, respectively, Fluoranthene accounted for 6573% of the total PAH loading and was the dominating compound within the group. As PAH production is associated with anthropogenic activities such as thermal power generation, home heating, and industry, the distance from potential sources may explain the differing observations (24). Within a 60-km radius there is a greater population density at Ellenlie than at either of the other locations, with the lowest being at the Kejimkujik site. Prevailing westerly winds could influence the Ellerslie site by carrying PAH contaminants from the shoreline communitiesof eastern New Brunswick. Though maximum values varied each year, the interquartile range of observations remained stable and did not indicate any long-term pattern. No relationship between the number of degree days below zero for a given winter and maximum observations could be demonstrated. The Ellerslie and Jackson sites are in areas that would be considered rural/agricultural and rural, and the Kejimkujik site is isolated. It is significant that the seasonal patterns displayed, match urban patterns reported in Switzerland for phenanthrene, pyrene, and benzo[a]pyrene and observations from surface water samples from Lake Zurich (14, 21). Seasonality is expected to be displayed due to differences in precipitation intensity and duration during the year ( I ) . Preferential PAH scavenging by snow could also account for the seasonal patterns. The observations for PAHs are therefore a result of primarily long-range transport at Jackson and Kejimkujik and to some extent localized sourcing at Ellerslie as indicated by the mass loading profiles. Hexachlorocyclohexanes. a-HCH and y H C H were frequently observed in wet precipitation samples and subjected to temporal and spatial analysis. Lindane (yHCH) is not a major use insecticide in either New Brunswick, Nova Scotia, or Prince Edward Island (25).
T
1
T
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2000
1000
0
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Flgure 6. Mean monthly precipitation volumes (ref 1) collected from three sites in the Atlantic Region. Error bars: SD over the course of the data record.
always during the cold months. Eight additional PAHs were added to the parameter list in late 1988, and initial results indicate that a similar seasonal pattern exists. The yearly concentration maxima for fluoranthene recorded in 1982,1984,1985,and 1986 at Ellerslie are 1order of magnitude above those observations recorded at Kejimkujik and Jackson. These variations are not reflected to the same extent by the mass loading profile shown in Figure 7 with the exception of 1982, which is less than a factor of 3 higher. All other loadings data are compara-
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1916
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Flgure 7. Loading of total PAHs from wet precipitation at three study sites in the Atlantic Region. Environ. Sci. Technol., Vol. 25, No. 7, 1991
1215
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Flgure 8. Ordinal rank of monthly median values for four PAHs.
Less than 5 kg of active ingredient was sold in New Brunswick in 1983, 1984, and 1985 (26). Line graphs representing concentrations and loadings for a-HCH and y-HCH at Ellerslie, Jackson, and Kejimkujik are presented in Figure 9. A pattern indicating diminishing concentrations and loadings is observed at Ellerslie and Kejimkujik. The results reported a t both locations are of the same order of magnitude, and the maximum values a t both sites were recorded during the same time period in 1981-1982. The observations recorded a t the Jackson station, which came on line in 1985, are within the same order of magnitude as those a t Ellerslie c 0
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A
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and Kejimkujik. Seasonal patterns with maxima consistently occurring during the spring and fall are observed for the three sites. Fairly good correlations were obtained between HCH concentrations and loadings for the three sites. Rank correlation coefficients of 0.880 and 0.894 were calculated for a-HCH and y-HCH at Ellerslie, 0.870 and 0.799 at Kejimkujik, and 0.684 and 0.654 at Jackson. The high concentrations observed during the 1980-1984 period do not seem to be influenced by smaller precipitation volumes as was the case with PAHs, and this is reflected by similar HCH loading profiles. During the period 1980-1984, when HCHs were at their highest level, average loadings of 15.9 and 19.1 pg.m-2.year-1 for a-HCH and 5.04 and 4.84 pg.m-2.year-1 for y-HCH were estimated for Ellerslie and Kejimkujik, respectively. These estimates are slightly higher than loadings of 10.4 and 3.53 pgm-2-year-1reported for a-HCH and y-HCH in 1983 for Lake Superior (15). During the latter stage of the study period, 1985-1989, when levels had receded, average loadings of 5.24 and 5.50 pgm-2.year-1for a-HCH and 1.53 and 1.58 pgm-2.year-1 for y-HCH were estimated for the Kejimkujik and Jackson sites, respectively. The y-HCH estimates are probably biased slightly high because concentrations reported were close to the LOD and a significant number of results were reported as nondetected. A decrease by factors of approximately 3.6 and 3.2 in average yearly loading is indicated for a-HCH and y-HCH when the two periods for Kejirnkujik are compared. Very little data are available in the literature that can be used for direct comparison. Table IV illustrates annual mean concentrations of a-HCH and y-HCH in precipitation collected from various locations across Canada since 1979. Data from nine other locations extracted from reports by Brooksbank (13) and Strachan (27)are included. Statistical analyses were performed on all data sets except for Kouchibouguac, Lake Superior, and Cree Lake, for which statistical data were unavailable. The means of various data sets were then compared for significant differences by using either a pooled or unpooled t test, preceded by a check for normality and equality of variances by using the F test ( P = 0.05).
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N 0.03
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