Environ. Sci. Technol. 1985, 19, 842-849
Bioconcentration Factors of Some Halogenated Organics for Rainbow Trout: Limitations in Their Use for Prediction of Environmental Residues Barry G. Oliver*-t and Arthur J. Nllml~ Environmental Contaminants Division, National Water Research Institute, and Great Lakes Fisheries Research Branch, Canada Centre for Inland Waters, Burlington, Ontario, Canada L7R 4A6
The bioconcentration factors, BCF’s, for 34 chlorinated and brominated chemicals in rainbow trout have been determined by the steady-state approach by using chemical water concentrations in the nanogram per liter range. In addition, for 13 chemicals with a known half-life in trout, BCF’s were also estimated by using the kinetic approach. The two methods gave comparable results for compounds with short half-lives in the fish but significantly different results for longer half-life chemicals. The BCF’s have been shown to correlate well with octanol/water partition coefficients, KO,,for many of the study compounds. But the BCF’s of high molecular weight compounds and compounds metabolized by the fish did not correlate with KO,. The laboratory-derived BCF’s were compared to fieldderived BCF’s for Lake Ontario rainbow trout. This comparison showed that predictions based on laboratory BCF’s were useful for chemicals with short half-lives in fish but were much too low for long half-life chemicals, where contaminated food is the major chemical source.
Introduction The bioconcentration and bioaccumulation of organochlorine compounds by fish are problems in many aquatic systems. In the Great Lakes, particularly in Lake Ontario, many game fish are unsuitable for human consumption because they contain high concentrations of organochlorine insecticides and PCB’s (I,2). Detrimental effects of organochlorine compounds have also been observed in Lake Ontario populations of fish eating birds such as the herring gull (3). Contaminant residues in fish are a result of direct uptake of the chemicals from water ( 4 ) and uptake from consumption of contaminated food (5). Even though the concentration of most chlorinated organics in water bodies is low, usually in the nanogram per liter range (6, 7), because of the large volume of water processed by the gills (10-1000 L/day depending of fish size) (8), significant concentrations of contaminants can be accumulated by this route. The bioconcentration of chemicals from water by algae, zooplankton, etc. can lead to food chain accumulation in fish at the top of the pelagic food chain (5). The uptake of chemicals by macroinvertebrates such as oligochaete worms from contaminated sediments and detritus (9) can lead to food chain accumulation in fish at the top of the benthic food chain (5). The tendency of a chemical to bioconcentrate has been shown to be strongly related to its lipophilicity. Octanol is the most commonly used lipid surrogate, and most bioconcentration measurements have been shown to correlate well with octanol/water partition coefficients (4, 10-12). Since lipophilic compounds are usually more hydrophobic or water insoluble, bioconcentration has also been shown to be inversely related to the chemical’s water solubility (13, 14). However, correlations between bioconcentration and physical properties are poor for very large molecules of high molecular weight (15,16)and for t National Water Research Institute. t
Great Lakes Fisheries Research Branch.
842
chemicals that are readily metabolized by fish (17, 18). In this paper we report on the bioconcentration factors, BCF’s, of 34 chlorinated and brominated compounds in rainbow trout from water at chemical concentrations in the nanogram per liter range. Chemicals having a wide range of physical and chemical properties were studied in order to obtain a better understanding of the bioconcentration process. The fish were exposed to a constant concentration of chemicals in flow-through tanks for a period of 96 days. Periodic samples were taken, and it was expected from previous work ( 4 ) that many of the chemicals would reach a steady-state concentration in the fish during the study. Because half-life data for several of the chemicals were available from other studies, we were also able to derive BCF’s using the kinetic approach (15,19, 20) for some of the compounds. The usual BCF correlation with octanol/water partition was performed, and an attempt was made to use the laboratory-derived BCF’s to predict residue levels in field rainbow trout from Lake Ontario for chemicals which were detected in the lake.
Experimental Section A list of the study chemicals and their abbreviations, octanol/water partition coefficients (and source), and parachors (surface tension corrected molar volume) are shown in Table I. Details of the fish exposure procedures have already been published (4). Briefly, 200 g of rainbow trout (Salmo gairdneri) was exposed to chemicals in the nanogram per liter concentration range in 1 X 1 X 0.5 m self-cleaning fiberglass tanks (6 L/min flow) at 15 “C. Thirty-two fish were placed in each of three tanks, and two fish were removed from each tank at the start of the exposure period. Six fish from each tank were sampled after exposures of 7,21,35,50,75, and 96 days. Water samples from all tanks were collected for analysis weekly. Compounds 1-18 were spiked into tank 1at low concentrations and into tank 2 at about 10 times the tank 1 concentrations. Tank 3 contained compounds 19-34. Concentrations of the chemicals in the fish were corrected for initial contamination by subtracting concentrations in the six control fish. Tank 1and tank 2 fish were used as controls for tank 3 fish and tank 3 fish as controls for tank 1and tank 2 fish to correct for chemical uptake from food over the study. These concentration corrections were minimal compared to the measured chemical uptake from the water. Our detailed analysis procedures for water and fish have already been published (21,22). Briefly, 4-L water samples were extracted with 75 mL of hexane, and after suitable concentration by evaporation, the extract was cleaned up in a silica gel column impregnated with 40% HzS04. Whole fish samples (15 g homogenized) were Soxhlet extracted with acetone/hexane after drying with Na2S04,the acetone was removed by water extraction, bulk lipids were eliminated by direct treatment with concentrated H2S04, and the extract was finally polished on a 40% H2S04silica gel column. Samples were quantified on dual capillary columns (OV1 and SE54) with electron capture detectors. Spiking studies on all study compounds from water and
Environ. Sci. Technol., Vol. 19,No. 9, 1985 0013-936X/85/0919-0842$01.50/0
Published 1985 by the American Chemlcal Society
Table I. Study Compound Abbreviations, Octanol/Water Partition Coefficients (Source), and Parachor” compound
abbreviation
1 1,4-dichlorobenzene 1,4-DCB 2 2,4-dichlorobenzo2,4-DCBTF trifluoride 3 1,2,4-trichlorobenzene 1,2,4-TCB 2,4,5-TCT 4 2,4,5-trichlorotoluene 5 1,2,3,4-tetrachloro1,2,3,4-TeCB benzene 6 1,3,5-tribromobenzene 1,3,5-TBB 7 2,3,4-trichloroanisole 2,3,4-TCA 8 2,3,5,6-tetrachloronitro- 2,3,5,6-TCNB benzene 9 2,3,5,6-tetrachloro-p2,3,5,6-TCPX xylene 10 2,3,4,5-tetrachloronitro- 2,3,4,5-TCNB benzene 11 a-hexachlorocycloa-BHC hexane 12 pentachloroanisole PCA 13 1,2,4,5-tetrabromo1,2,4,5-TeBB benzene 14 y-hexachlorocyclolindane hexane 15 pentachloronitrobenzene PCNB 16 y-chlordane y-chlor 17 a-chlordane a-chlor 18 2,2-bis(p-chlorophenyl)- p,p’-DDE 1,l-dichloroethylene
log K ,
parachor
compound
abbreviation log KO, parachor
3.4 (36) 4.4 (29)b
290 360
19 2,5-dichlorobiphenyl 20 2,3,4,5,6-pentachlorotoluene
PCB 9 PCT
5.2 (42) 6.2 (29)b
480 440
4.0 (37) 4.8 (29)b 4.5 (38)
330 370 360
21 2,3-dichlorobiphenyl 22 3,5-dichlorobiphenyl 23 2,5,2’-trichlorobiphenyl
PCB 5 PCB 14 PCB 18
5.2 (42) 5.2 (42) 5.6 (43)
480 480 520
4.5 (39) 4.2 (29)b 3.9 (30)
360 380 420
24 2,5,2’,5’-tetrachlorobiphenyl
PCB 52 5.8 (43) 25 1,2,3,4-tetrachloronaphthalene 1,2,3,4-TeCN 5.5 (30) PCB 40 5.8 (43) 26 2,3,2’,3’-tetrachlorobiphenyl
560 470 560
6.2 (29)b
440
27 octachlorostyrene
3.9 (30)
420
3.8 (40)
ocs
6.2 (11)
510
28 2,4,6,2’,4’,6’-hexachlorobiphenyl PCB 155
6.7 (13)
630
480
29 2,4,5,2’,5’-pentachlorobiphenyl PCB 101
6.1 (13)
600
5.7 (29)b 5.1 (39)
460 420
30 pentabromotoluene 31 pentabromoethylbenzene
PBT PBEB
7.0 (29)b 7.5 (29)b
510
3.7 (40)
480
32 hexabromobenzene
HBB
7.3 (29Ib
520
5.4 (30) 6.0 (11) 6.0 (11) 5.7 (41)
460 640 640 610
33 mirex 34 octachloronaphthalene
Mirex OCN
6.9 (11) 6.5 (30)
750 630
550
Calculated bv the method of Quavle (44). Calculated bv the a method of Hansch and Leo (29).
fish were performed, and recoveries from both matrices were satisfactory 280%. The reproducibility of the methods on replicate samples was *lo%. In order to provide comparative data from the field, 10 adult rainbow trout were captured during their spawining migration in the Ganaraska River, a tributary of Lake Ontario. The average weight of the fish was 3 kg, and the average lipid content was 8%. Large volume samples (200 L) of Lake Ontario water were collected at a depth of 10 m in the lake epilimnion in Oct 1983 in eight widely dispersed offshore sites covering the entire lake surface. Although the sampling was limited, the results should provide a fair estimate of the concentration of chemicals in the lake. The samples were extracted on station with 8 L of dichloromethane by using a specially designed liquid-liquid extractor consisting of a 200-L stainless steel barrel and pump (23). At the time of collection 1,3,5tribromobenzene, 1,2,4,5-tetrabromobenzene,2,3,4,5tetrachlorobiphenyl, and octachloronaphthalene were spiked into the drum and subsequently carried through the entire extraction. The recoveries of these chemicals, which were not present in the lake water, were approximately 50% with losses due mainly to volatilization during the Snyder condenser evaporation of the large solvent volume and not due to extraction inefficiency. The data have been corrected to take into account the recovery of the surrogate spikes. A more detailed description of the procedures and results from these and other lake samples will be published separately. The same cleanup and capillary quantification procedures were used in this part of the work. Because of the high purity dichloromethane used in the study, minimal solvent blanks were observed for most study compounds. The classical equation describing the uptake and elimination of chemicals by fish is where C, and Cw are the chemical concentration in fish and water and kl and k2 are the uptake and elimination rate constants, respectively. If it is assumed that 1 g of
fish is equivalent to 1 mL of water, then the units of kl and k2 are in day-l. At steady state dCF/dt = 0, and the bioconcentration- factor, BCF, is The BCF can thus be estimated by measuring the chemical concentration in fish at steady state after exposing the fish for the appropriate length of time to a constant chemical concentration in the water. In the kinetic approach the rate constants kl and k2 are estimated in separate experiments. If Cw is constant, eq 1can be integrated to yield (3) The rate k , is usually estimated by dosing the fish with chemical through exposure to contaminated either water or food and then placing it in clean water and measuring the depuration rate of the chemical: (4) where TlIzis the half-life of the chemical in the fish. In a separate experiment the uptake of the chemical from water is studied. A plot of CF vs. 1 - e-k2t should be a straight line with slope equal to klCw/k2. Since Cw and k2 are known, kl can be estimated.
Results and Discussion Measurements of the bioconcentration factors for the 34 study compounds by the steady-state approach are shown in Tables II-IV. Two additional compounds, hexachlorocyclopentadieneand decachlorodiphenyl ether, were also tested at water concentration 7 and 2.7 ng/L, respectively, but were not detected in the fish. Some of the compounds had previously been tested by us in two similar experiments (4, 24). These compounds were included in this study to measure the consistency of the data and also to obtain more information on the concentration dependence of the BCF’s ( 4 ) . Data from this study are compared to earlier BCF data from our laboratory in Table V. Good agreement is seen between the studies, and this Environ. Sci. Technol., Vol. 19,No. 9, 1985 843
Table 11. Bioconcentration Factors [Chemical Concentration in Fish (ng/kg Wet Weight)/Chemical Concentration in Water (ng/L)] for Chemicals 1-18 at Lowest Concentration (Tank 1) water concn, ng /L
BCF x 10-3
compound
mean f SD
range
day 7
day 21
day 35
day 50
day 75
day 96
mean
1,CDCB 2,4-DCBTF 1,2,4-TCB 2,4,5-TCT 1,2,3,4-TeCB 1,3,5-TBB 2,3,4-TCA 2,3,5,6-TCNB 2,3,5,6-TCPX 2,3,4,5-TCNB a-BHC PCA 1,2,4,5-TeBB 1ind ane PCNB y-chlor a-chlor p,p'-DDE fish weight, g lipid, 70
81 f 22 26 f 7.4 6.3 f 1.7 5.1 f 1.6 3.0 f 0.9 2.2 f 0.8 10 f 3 2.0 f 0.7 1.8 f 1.0 1.0 f 0.4 3.6 f 0.9 0.9 f 0.3 2.0 f 1.2 3.7 f 0.7 1.4 f 0.5 1.4 f 0.6 1.2 f 0.4 1.3 f 0.7
57-110 18-36 4.6-8.3 3.4-6.7 2.1-4.1 1.3-2.9 6.7-14 1.1-2.8 0.7-3.3 0.6-1.6 2.3-4.7 0.5-1.3 0.7-3.9 2.2-5.0 0.9-1.9 0.8-2.1 0.8-1.7 0.5-2.3
0.51 f 0.15" 1.6 f 0.62" 1.5 f 0.25" 3.5 f 0.68 2.6 f 0.36 1.8 f 0.43 1.3 f 0.24" 1.0 f 0.27" NDb ND 0.94 f 0.20 3.1 f 0.50 0.88 f 0.21 0.77 f 0.16" 0.38 f 0.10" 2.0 f 0.43 3.7 f 0.75 2.2 f 0.62 226 f 38 6.3 f 2.5
0.39 f 0.07" 2.1 f 0.48" 1.9 f 0.34" 6.9 f 1.7" 5.0 f 1.0' 6.2 f 1.3 1.5 f 0.24" 1.6 f 0.61" ND ND 1.3 f 0.24" 8.3 f 1.4 2.6 f 0.65" 1.1 f 0.21" 0.38 f 0.21' 5.8 f 1.2 7.5 f 1.6 3.9 f 1.3 220 f 41 5.0 f 1.0
1.0 f 0.21" 3.6 f 0.75" 5.2 f 0.44" 9.7 f 1.7" 8.6 f 1.8" 12 f 2.3" 2.2 f 0.50" 2.4 f 0.76" ND ND 2.4 f 0.59" 16 f 3.5" 4.8 f 1.4" 2.1 f 0.51" ND 11 f 2.6 14 f 2.5 8.7 f 3.4 202 f 26 7.7 f 2.2
0.53 f 0.18" 3.3 f 1.5" 2.2 f 0.58" 8.2 f 2.2" 6.9 f 2.0" 9.4 f 2.8" 1.8 f 0.48" 2.1 f 0.65" ND ND 1.8 f 0.66" 14 f 2.9" 4.6 f 2.1" 1.4 f 0.43" 0.65 f 0.47" 9.3 f 2.2 11 f 2.6 7.3 f 3.9 202 f 35 6.9 f 2.5
0.22 f 0.06" 1.2 f 0.43" 1.4 f 0.40" 5.7 f 1.9" 5.0 f 1.4" 6.7 f 0.52" 0.91 f 0.19' 0.89 f 0.28" ND ND 1.1 f 0.28" 12 f 2.4" 2.6 f 1.0" 0.77 f 0.22" ND 12 f 3.0 14 f 3.3 8.2 f 3.2 258 f 57 6.9 f 1.7
0.43 f 0.14" 2.4 f 1.0" 1.8 f 0.60" 7.4 f 2.7" 5.9 f 2.3" 9.3 f 3.9" 1.8 f 0.57" 1.9 f 0.83" ND ND 1.6 f 0.59 17 f 7.1" 3.9 & 1.8" 1.2 f 0.48" 0.95 f 0.53" 15 f 6.8 16 f 7.0 9.9 f 5.8 312 f 49 7.3 f 1.5
0.51 f 0.26 2.4 f 0.94 2.3 f 1.4 7.6 f 1.5 6.3 f 1.5 9.4 f 2.2 1.6 f 0.45 1.6 f 0.60 ND ND 1.6 f 0.50 15 f 2.2 3.7 f 1.1 1.2 f 0.5 0.59 f 0.27 15c 16' 9.9c
Values used for calculation of mean. bNot detected. Hiehest value (not eauilibrated). ~
~~
Table 111. Bioconcentration Factors for Chemicals 1-18 at Highest Concentration (Tank 2)
BCF x 10-3
water concn, ng J L compound
mean f SD
range
day 7
day 21
1,4-DCB 2,4-DCBTF 1,2,4-TCB 2,4,5-TCT 1,2,3,4-TeCB 1,3,5-TBB 2,3,4-TCA 2,3,5,6-TCNB 2,3,5,6-TCPX 2,3,4,5-TCNB wBHC PCA 1,2,4,5-TeBB lindane PCNB y-chlor a-chlor p,p'-DDE fish weight, g lipid, %
73 f 20 210 f 62 5.9 f 2.0 49 f 25 3.3 f 1.4 20 f 10 66 f 19 14 f 5.7 12 f 7.3 9.0 f 3.5 22 f 5.4 10 f 6.2 17 f 11 26 f 5.5 14 f 8.5 17 f 10 13 f 8.2 13 f 7.9
44-95 91-270 2.7-8.4 29-81 1.8-4.5 9-32 48-87 8-20 5-23 4-13 16-28 4-18 5-34 19-32 5-25 7-32 6-26 5-24
0.82 f 0.24" 1.6 f 0.68 2.0 f 1.1 3.3 f 1.3 3.1 f 1.4 3.4 f 1.5 1.4 f 0.52 1.0 f 0.39 NDb ND 0.94 f 0.36 3.9 f 1.5 2.5 f 1.0 0.88 f 0.31 ND 1.8 f 0.89 2.3 f 1.1 1.8 f 1.0 175 f 45 5.3 f 1.8
0.86 0.17" 4.9 f 0.93" 4.0 f 0.60" 7.4 f 0.91" 8.6 f 1.0" 9.3 f 1.3" 2.6 f 0.24" 2.7 f 0.39" 1.1 f 0.37 0.07 f 0.03" 2.8 f 0.31" 9.0 f 1.1 4.2 f 0.71 291 f 0.23" 0.35 f 0.12" 5.2 f 1.1 5.9 f 1.1 3.7 f 0.70 183 f 39 7.1 f 1.1
Values used for calculation of mean.
*
Environ.
Sci. Technol.,
day 50
day 75
day 96
mean
1.1 f 0.27" 3.6 f 0.33" 5.6 f 0.84" 11 i 2.3" 9.9 f 2.3" 16 f 3.4" 2.5 f 0.63" 2.6 f 0.89" 3.7 f 0.78" 0.10 f 0.03" 2.3 0.56" 20 f 2.5" 6.5 f 0.82" 2.1 f 0.61" 0.35 f 0.08" 13 f 1.2 13 f 1.1 8.3 f 0.83 284 f 54 7.0 f 1.3
0.59 f 0.10" 3.2 f 0.87" 2.3 f 0.48" 6.8 f 1.3" 6.8 f 1.3" 10 f 2.4" 1.6 f 0.25" 1.2 f 0.34" 2.3 f 0.72" 0.05 f 0.01" 2.0 f 0.39" 15 f 2.6" 4.5 f 1.0" 1.7 f 0.28" 0.09 f 0.04" 1 2 f 1.5 13 f 1.8 8.2 f 0.86 262 f 63 6.7 f 1.0
0.55 f 0.10" 3.5 f 0.87" 2.4 f 0.48" 9.1 f 1.3" 7.2 f 1.3" 14 f 3.6" 2.4 f 0.41" 2.5 f 0.64" 5.4 f 1.1" 0.11 f 0.02" 2.7 f 0.56" 24 f 5.4" 8.2 f 3.3" 2.1 f 0.44" 0.41 f 0.12" 20 f 4.6 22 f 3.9 14 f 1.4 288 f 57 8.0 f 1.8
0.89 f 0.32 3.9 f 0.70 3.7 f 1.4 8.5 f 1.7 8.1 f 1.2 12 f 3.0 2.3 f 0.40 2.2 f 0.64 3.8 f 1.6 0.08 f 0.03 2.4 f 0.36 20 f 4.5 6.4 f 1.9 2.0 f 0.18 0.26 f 0.15 2OC 22c 14c
*
Not detected. CHighestvalue (not eauilibrated).
shows the reproducibility of the experimental approach. The data also give more credence to the idea that chemicals can be tested in groups at low concentrations, instead of individually, with minimal impact on the results. This approach greatly reduces the time and cost of the experiment. As in our previous study ( 4 ) , exposure to higher doses of chemicals yields somewhat higher BCF's. The BCF's in tank 2 (Table 111)averaged about 1.5 times those in tank 1 (Table 11). For most chemicals, fish exposure levels in tank 2 were approximately 10 times that of tank 1, and final total residue levels in the fish were 3.1 ppm in tank 2 and 0.29 ppm in tank 1. The three chlorobenzenes were spiked into both tanks at about the same concentration (1,4-DCB, 81 and 73 ng/L; 1,2,4-TCB, 6.3 and 5.9 ng/L; 1,2,3,4-TeCB,3.0 and 3.3 ng/L), but the BCF's were higher for all three CB's in tank 2. The rate of uptake of the CBs was about the same in both tanks. Thus, the rate of elimination of the CB's from the tank 2 fish, containing 844
day 35 1.4 f 0.29" 4.4 f 1.1" 4.4 f 1.4" 8.0 f 2.3" 8.1 f 2.6" 9.8 f 3.2" 2.2 f 0.80" 1.8 f 0.76" 1.7 f 0.96 ND 2.1 f 0.75" 11 f 3.1" 4.1 f 1.0" 1.9 f 0.66" 0.11 f 0.05" 6.8 f 1.8 7.5 f 1.9 5.0 f 1.5 277 f 51 7.9 f 1.4
Vol. 19, No. 9, 1985
the higher chemical residue concentration, must have been somewhat slower than for the fish in tank 1. The concentration dependence of BCF's is not particularly large when compared to differences in BCF's due to chemical properties. But, since concentration effects do exist, experiments should be conducted at as close to environmental concentrations as practicable so that the data can be better applied to field samples. From a statistical analysis of the data in Tables 11-IV, it is usually possible to ascertain whether chemicals have reached a steady-state concentration in the fish. The shorter the chemical's half-life in the fish, the more rapidly the equilibrium concentration in the fish is established. For example, by use of eq 3, chemicals with half-lives of 22 days or less will reach 95% of their steady-state concentration over the 96-day study period. Thus, it should be possible to obtain an equilibrium BCF for such chemicals during this experiment. Most of the chemicals in Tables I1 and I11 with the exception of a-and y-chlor and
Table IV. Bioconcentration Factors for Compounds 19-34 (Tank 3) compound PCB 9 PCT PCB 5 PCB 14 PCB 18 PCB 52 1,2,3,4-TeCN PCB 40
ocs
PCB 155 PCB 101 PBT PBEB HBB mirex OCN fish weight, g lipid, %
BCF x 10-3
water concn, ng/L mean f SD range 15 f 4.1 2.1 f 0.5 7.9 f 2.4 16 f 3.6 16 f 3.6 12 f 1.9 5.6 f 1.0 13 f 2.0 4.8 f 0.7 17 f 2.3 15 f 2.1 4.8 f 0.8 8.3 f 1.3 0.61 f 0.1 4.1 f 1.0 13 f 2.6
8-20 1.6-2.8 4-11 11-20 12-22 10-15 4.3-7.0 9-16 3.4-5.3 12-18 11-18 3.5-5.9 5.7-10 0.5-0.8 2.7-5.4 8-17
" Values used to calculate mean.
day 7
day 21
day 35
day 50
day 75
day 96
mean
2.4 f 1.7 2.4 f 1.7 2.8 f 1.9 2.4 f 1.7 2.7 f 2.0 3.1 f 1.9 2.1 f 1.3 2.3 f 1.4 0.81 f 0.55 0.61 f 0.34 1.6 i 0.98 0.17 f 0.12 0.20 f 0.08 ND' 0.06 f 0.01 0.06 f 0.06 205 f 28 6.6 f 1.0
3.7 f 2.0 4.9 f 1.5 6.8 f 2.0 4.0 f 0.73 6.5 f 1.9 6.3 f 1.9 3.7 f 1.2 5.6 f 1.7 2.0 f 0.64 1.3 f 0.37 3.5 f 1.1 0.17 f 0.09 0.24 f 0.07 0.97 f 0.28" ND 0.12 f 0.05 199 f 37 6.6 f 1.3
8.0 f 1.9" 6.5 f 1.7" 8.9 f 2.2 5.6 f 1.7" 9.4 f 2.2 10 f 1.4 5.3 f 1.8" 10 f 2.8 3.6 f 0.93 2.4 f 0.59 6.1 f 1.6 0.26 f 0.14" 0.35 i 0.11" 1.2 f 0.30" 0.34 f 0.07 0.27 f 0.10" 191 f 37 7.9 f 3.1
10 f 2.0" 6.9 f 1.6" 11 f 2.3" 6.1 f 1.5" 12 f 2.4 13 f 2.1 5.3 i 1.5" 13 f 3.6 5.1 f 1.2 3.3 f 0.61 8.5 f 2.0 0.31 f 0.16" 0.37 f 0.18" 0.83 0.28" 0.42 f 0.06" 0.28 f 0.06" 223 f 31 7.8 f 1.3
13 f 1.6" 7.3 f 1.22 13 f 1.6" 6.7 f 1.0" 17 f 2.3 18 f 2.2 5.0 f 1.0" 17 f 1.7 8.1 f 1.2 4.8 f 0.67 13 f 2.0 0.22 f 0.10" 0.27 f 0.23" 0.90 f 0.32" 0.56 f 0.07 0.42 f 0.13" 278 f 28 6.6 f 1.7
8.0 f 8.0" 6.3 f 2.5" 12 f 6.3" 5.4 f 2.0" 17 f 7.7 18 f 5.7 4.6 f 1.9" 17 f 6.6" 8.1 f 3.4 4.8 f 1.8 14 f 5.9 0.29 f 0.13" 0.33 f 0.14" 1.4 f 0.58R 0.74 f 0.42 0.34 f 0.18" 341 f 52 8.2 f 1.4
10 f 2.4 6.8 f 0.44 13 f 0.71 6.1 f 0.65 17b 18b 5.1 f 0.33 17b 8.1b 4.8b 14b 0.27 f 0.04 0.33 f 0.04 1.1 f 0.24 0.74b 0.33 f 0.07
Highest value (not equilibrated).
'*
Not detected.
Table V. Comparison of BCF'S from This Study with Earlier Data from O u r Laboratory" BCF
compound 1,4-DCB 1,2,4-TCB 1,2,3,4-TeCB 2,4,5-TCT 1,3,5-TBB 1,2,4,5-TeBB 2,3,4-TCA
BCF
lon3for this study
X
0.51 f 0.26 (81) 2.3 f 1.4 (6.3) 6.3 f 1.5 (3.0) 7.6 f 1.5 (5.1) 9.4 f 2.2 (2.2) 3.7 f 1.1 (2.0) 1.8 f 0.57 (10)
0.89 f 0.32 (73) 3.7 f 1.4 (5.9) 8.1 f 1.2 (3.3) 8.5 i 1.7 (49) 12 f 3.0 (20) 8.2d (17) 2.3 f 0.40 (66)
X
0.67 f 0.18 (28)b 1.3 f 0.32 (3.2)b 5.2 f 0.50 (1.4)b 4.8 f 0.28 (0.1)' 5.0 f 0.40 (0.3)c 6.3d (O.l)c 0.92 f 0.10 (0.9)c
for earlier studies 0.72 f 0.13 (670)b 3.2 f 0.54 (52)b 12 f 1.5 (26)b
"Water concentration (ng/L) in parentheses. bFrom ref 4. cFrom ref 24. dHiahest value. Table VI. Half-Lives, Uptake, and Elimination Rate Constants and a Comparison of Kinetic and Static BCF's for Some PCB's and Pesticides compound
(source), days
k2 x lo2, day-'
PCB 9 PCB 5 PCB 14 PCB 18 PCB 52 PCB 40 PCB 155 PCB 101 p,p'-DDE lindane y-chlor a-chlor mirex
85 (25) 61 (25) 15 (25) 190 (25) 500 (25) 107 (25) >lo00 (25) >lo00 (25) 340 (45) 11 (46) 33 (47) 60 (47) >lo00 (26)
0.82 1.1 4.6 0.37 0.14 0.65 86 >250 81 2.1 16 28 >12
steady-state
BCF x 10-3 (cF/cw) 10 13 6.1 17 18 17 4.8 14 -12"
1.6" 18" 19" 0.74
"Average for tank 1 and tank 2 fish.
p,p'-DDE fall into this category. However, chemicals that have longer half-lives in trout will not attain a steady-state concentration over the study period. For example, the following percentages of steady-state concentration will be reached after 96 days for chemicals having the following half-lives: 40 days, 81%; 60 days, 67%; 80 days, 56%; 100 days, 49%; 200 days, 28%; 300 days, 20%; 500 days, 12%; 1000 days, 6%. Chemicals such as a- and y-chlor, p,p'DDE, and most of the chemicals in Table IV fall into this category. The BCF's can be found for chemicals of known half-life by using the kinetic approach from the data in Tables 11-IV. Half-life data and source, uptake and elimination rate constants, and kinetic and steady-state BCF's are tabulated for the PCB's and some pesticides in Table VI. The half-lives used for calculation must be corrected
for growth dilution. For compunds with short half-lives in fish such as PCB 14, lindane, and y-chlor, excellent agreement between kinetic and steady-state BCF's are evident. As expected, the longer the chemicals' half-life the larger the discrepancy between the two BCF's. These results clearly show that the steady-state BCF procedure is not reliable for chemicals that are eliminated slowly by fish. An examination of the data in Table IV shows that a steady chemical concentration in the fish has apparently been attained for most of the chemicals. But, the application of the kinetic approach shows that this is probably incorrect and that continuing exposure would likely lead to further bioconcentration. The reason for apparent plateauing of the concentrations for several of the longer Environ. Sci. Technol., Vol. 19, No. 9, 1985
845
104
“I
0
d
io4
h
Q
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10
,
I
/ ! I (
half-life PCB’s (Table IV) is not known but may be due to fluctuations in PCB water concentrations. Spacie and Hamelink (15) observed that the uptake rate constant, k l , was fairly constant for a wide range of chemicals. The lower chlorinated PCB’s in Table VI are seen to have relatively constant kl’s. A decrease in kl is PCB 101, with observed for 2,4,5,2’,5’-pentachlorobiphenyl, a more substantial drop in uptake for 2,4,6,2’,4’,6’-hexachlorobiphenyl, PCB 155. This decrease in uptake rate, which is likely due to increasing molecular size and weight, begins to occur at molecular weights greater than ~ 3 0 and 0 parachors >500. The uptake rate constant for mirex (M, 546, parachor 750) is only 3% that of the lower chlorinated PCB’s. OCN also appears to have a very low kl, close to that of mirex, and decachlorodiphenyl ether, an even larger, heavier molecule, was not detected in any of the fish. It appears that these large molecules are not efficiently transferred across the gill membranes even though they can be assimilated by fish from food (25, 26). The steady-state BCF’s for most of the compounds in Table I1 (low dose) and for some of the compounds in Table IV together with the kinetic BCF’s for the rest’of the compounds from Table VI are plotted vs. KO,in Figure 1. From the resulting scattergram there appears to be no correlation between the two parameters (linear correlation coefficient, rz = 0.02). Considering only the uppermost 16 compounds in the plot (compounds 1-8,11, 14,18,19,21, 23, 24, and 26), the following equation for the line shown in the figure can be derived: log BCF = -0.56 + 0.96 log KO, n = 16, r* = 0.95 (5) 846
Environ. Sci. Technol., Vol. 19, No. 9, 1985
1 ,
This equation is in excellent agreement with our earlier published equations for chlorinated aromatics ( 4 , 2 4 ) and has a slope near 1 in agreement with the equation of Mackay (12). Several reasons can be advanced to explain why about half of the study compounds have much lower BCF’s than would be predicted from their octanol/water partition coefficient. Compounds 28,29, and 33 (PCB 155, PCB 101, and mirex) were excluded from the analysis because only minimum BCF’s could be calculated for these compounds (Table VI). As demonstrated earlier, chemicals with long half-lives in fish (>22 day) would not be expected to reach equilibrium concentrations in the fish over the 96-day study period. The kinetic approach was used for compounds with known half-lives, but this information was not available for all compounds. OCS, PCT, and 1,2,4,5-TeBB would be expected to have long half-lives in trout so BCF’s from this study are probably too low for these substances. Southworth et al. (17,18) demonstrated that observed BCF’s for polycyclic aromatic compounds metabolized by fish are much lower than predicted from their Kow. For metabolized compounds the bioconcentration process is described by the equation dC,/dt = IzlCw - (h, + IZM)CF
(6)
where kM is the metabolic elimination coefficient. The observed BCF [kl/ (k2+ k M ) ] would be lower than the BCF based solely on physical uptake and elimination of the chemicals ( k l / k z ) . The larger the metabolic elimination rate, kM, the lower the BCF will be from the predicted value based on KO, (eq 5 ) . Pentachloronitrobenzene (15,
Table VII. Comparison of Field BCF’s for Lake Ontario Rainbow Trout and Laboratory-Derived BCF’s for Some Study Compounds Detected in the Lake
compound 1,2,4-TCB 1,2,3,4-TeCB wBHC lindane PCT
ocs
PCB 18 PCB 52 PCB 40 PCB 101 PCB 153 y-chlor a-chlor p,p’-DDE mirex
laboratory BCF x 10-3
Lake OntarioQ concn, ng/L
predicted residue concn, ngJg
measuredb residue concn, ngJg
1.3 5.2 1.6 1.2 6.8 24OC 81 200 49 2ooc 74OC 16 28 81 I,200”
0.5 f 0.2 0.13 f 0.07 1.5 f 0.2 0.3 f 0.1 0.03 f 0.01 0.02 f 0.01 0.02 f 0.01 0.03 f 0.01 0.02 f 0.01 0.02 f 0.01 0.03 f 0.01 0.02 f 0.01 0.03 f 0.01 0.03 f 0.01 0.008 f 0.003
0.7 0.7 2.4 0.4 0.2 4.6 1.8 6.2 1.1 3.8 19 0.3 0.8 2.3 9.0
0.6 f 0.3 1.0 f 0.4 1.1 f 0.4 0.3 f 0.1 0.7 f 0.3 2.6 f 14 13 f 5 60 f 28 5.6 f 2.7 160 f 87 250 f 130 1.3 f 0.3 38 f 23 510 f 180 110 f 68
field BCF X 1.2 7.7 0.7 1.0 23 1400 590 1900 240 8400 10000 76 1400 18000 15000
Mean concentration for eight offshore sites. *Mean concentration for 10 rainbow trout from Lake Ontario.
PCNB) is known to be rapidly metabolized by fish (27) so the BCF for this compound is well below the eq 5 line. Interestingly, the BCF for 2,3,4,5-TCNB also plots well below the line so this compound appears to be rapidly metabolized by the fish, whereas ita isomer 2,3,5,6-TCNB coincides with the eq 5 line so it does not appear to be readily metabolized. Fish metabolism of 3,5-dichlorobiphenyl (22, PCB 14) may also be the reason this compound plots below the line. This PCB has a much lower half-life in trout than the other two dichlorobiphenyls studied (25). Another reason for deviation from eq 5 may be incorrect or imprecise KoW)s. For example, for y- and a-chlordane we have used a KO, of lo6 which was estimated from high-pressure liquid chromatography retention time (11). Sanborn et al. (28) reported a KO,value of 600 for chlordane. The true value is likely somewhere between these two estimates. Since there were no experimental KO, values for some compounds, we estimated the KO, by Hansch and Leo’s ?r method (29). Kaiser (30)has shown that this method tends to overestimate the KO,for highly chlorinated aromatics. PCA has a short half-life in fish (6 days) (31)and so should equilibrate over the study, but the KO,used for this compound was calculated by the Hansch and Leo method and, therefore, may be too high. Several study compounds (OCN, mirex, PBT, PBEB, and HBB) have a large molecular size (parachlors > 500) and a high molecular weight (>400). The uptake rate of these compounds from water by the fish was low. Some resistance or restriction to transfer across the gill membrane seems to be present. Skea et al. (26)has shown that the half-life of mirex in fish is very long, and Zitko and Carson (32)showed that the half-life of PBT was between 32 and 83 days for Atlantic salmon. From these observations it appears likely that the half-lives for all these compounds in fish should be long so one would expect to see slowly increasing residue concentrations in the trout over the course of the study. This does occur for mirex, but the other four compounds appear to reach a steady concentration in the fish. There does not seem to be any simple explanation for the extremely low BCF’s of these compounds. It is probable that their BCF’s are controlled more by resistance of transfer across the gills rather than by simple exchange partitioning. Compounds 1,2,3,4-TeCN and 2,3,5,6-TCPX also fall well below the eq 5 line. 2,3,5,6-TCPX is not even detected in the fish at the lower exposure concentration so its behavior seems unusual. It is possible that these compounds
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field BCF/ lab BCF 0.9 1.5 0.5 0.8 3.4 5.7 7.3 9.7 5.0 42 14 4.8 50 220 12
Calculated by using eq 5.
are metabolized by the fish. The above discussion and Figure 1show that great care must be exercised in estimating BCF’s of chemicals solely from their physical or chemical properties such as KO,. Relationships such as eq 5 only work for compounds that are not metabolized and for which accurate partition coefficientsare known. They cannot be used for large, high molecular weight compounds. Few studies have assessed the utility of laboratory-derived BCF’s for environmental predictions. Earlier ( 4 ) we successfully used BCF’s to predict residue concentrations in Lake Ontario rainbow trout for the rapidly equilibrated, lower chlorinated benzenes. But, laboratory BCF’s severely underestimated the field residue concentrations of hexachlorobenzene a compound with a long half-life (-200 days) (33)in fish (4). A similar attempt to use laboratory BCF’s to predict Lake Ontario rainbow trout residue for 15 of the study compounds which were detected in Lake Ontario water is shown in Table VII. Equation 5 and the chemical’s KO,were used for estimating the BCF for OCS, PCB 101, mirex, and PCB 153 because neither the kinetic nor steady-state approach yielded a satisfactory BCF. PCB 153 (2,4,5,2’,4’,5’-hexachlorobiphenyl)was included in Table VI1 instead of PCB 155 because these compounds should have similar properties and because only PCB 153 was detected in Lake Ontario water. With the exception of a-BHC all the chemicals are present at concentrations below 1ng/L. A 200 000-fold concentration of the sample (200 L 1 mL) enabled us to easily detect these compounds in the concentration range observed. Hassett and Yin (34) have reported mirex in Lake Ontario near Oswego, NY, at concentrations between 0.004 and 0.015 ng/L in good agreement with our observations. Our estimates for total PCBs for Lake Ontario, 0.4-0.9 ng/L, are in the same range as those reported by Eisenreich et al. (7) for Lake Superior. An examination of Table VI1 shows that the predicted and measured residue levels of 1,2,4-TCBand 1,2,3,4-TeCB are in good agreement. These compounds have a short half-life in fish (35)so rapid equilibration occurs between the chemical concentration ih the fish and in the water. The major factor governing residue levels for these compounds appears to be the chemical concentration in the water. Similar behavior is observed for a-BHC and lindane with good agreement between field and laboratory BCF’s. For compounds with long half-lives in the fish, the use of laboratory BCF’s (kinetic or steady state) severely un-
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Environ. Sci. Technol., Vol. 19, No. 9, 1985
847
derestimates the field residue levels in the trout. The field BCF’s are from 3 to 220 times larger than the laboratory BCF’s. The residues in the fish are much higher for these chemicals than could possibly result from bioconcentration from water. This is a clear indication that water is not the primary route of fish exposure for these chemicals: consumption of contaminated food is apparently the major chemical source. These high-field BCF’s indicate that the rate of uptake of the chemicals by the fish exceeds its ability to eliminate the chemical. Residue levels in the fish likely continue to increase with fish age. An equilibrium between fish chemical concentration and water chemical concentration is probably never reached for these chemicals. The difference between field and laboratory BCF is particularly striking for p,p’-DDE. Since p,p’-DDE results primarily from the metabolish of p,p ’-DDT, the field BCF could be recalculated by using the formula Cp,p’-DDE + p,p’-DDT (fish)/Cp,p’-DDE + p,p’-DDT (H,O). By use of this formula, the field BCF would be 14000000 (535/(38 X still 170 times the laboratory BCF. The importance of food chain accumulation for Great Lakes trout has been previously reported by several investigators (5, 48,49). For example, Thomann and Connolly (49) demonstrated that more than 99% of PCB’s in Lake Michigan lake trout came from food. The data in Table VI1 clearly show the serious limitations of using laboratory BCF’s for prediction of environmental concentrations in field fish populations. For compounds such as PCB’s and some pesticides a better approach may be to measure the contaminant concentrations in the major food sources of the fish, to estimate rates of food consumption, and to determine the chemical’s half-life in the fish.
Acknowledgments We thank Karen Nicol and Vincent Palazzo for their technical assistance and the Technical Operations Division, NWRI, for collection of the water samples. Registry No. 1,106-46-7; 2,320-60-5; 3,120-82-1; 4,6639-30-1; 5, 634-66-2; 6,626-39-1; 7, 54135-80-7;8,117-18-0;9,877-10-1; 10, 879-39-0; 11, 319-84-6; 12, 1825-21-4;13,636-28-2; 14,58-89-9;15, 82-68-8; 16, 5566-34-7; 17, 5103-71-9; 18, 72-55-9; 19, 34883-39-1; 20, 877-11-2; 21, 16605-91-7; 22, 34883-41-5; 23, 37680-65-2; 24, 35693-99-3; 25, 20020-02-4; 26, 38444-93-8; 27, 29082-74-4; 28, 33979-03-2; 29, 37680-73-2; 30,87-83-2; 31, 85-22-3; 32, 87-82-1; 33, 2385-85-5; 34, 2234-13-1.
Literature Cited (1) “Guide to Eating Ontario Sport Fish. Southern Ontario Great Lakes 1984-85”; Ontario Ministry of the Environment: Toronto, Canada, 1984. (2) Whittle, D. M.; Fitzsimons, J. D. J . Great Lakes Res. 1983, 9, 295. (3) Gilbertson, M. Chemosphere 1983, 12, 357. (4) Oliver, B. G.; Niimi, A. J. Environ. Sci. Technol. 1983,17, 287. (5) Borgmann, U.; Whittle, D. M. Can. J . Fish. Aquat. Sci. 1983, 40, 328. (6) Oliver, B. G.; Nicol, K. D. Environ. Sci. Technol. 1982,16, 532. (7) Eisenreich, S. J.; Capel, P. D.; Looney, B. B. In “Physical Behavior of PCB’s in the Great Lakes”; Mackay, D.; Paterson, s.;Eisenreich, s. J.; Simmons, M. s.,Eds.; Ann Arbor Science: Ann Arbor, MI, 1983; pp 181-211. (8) McKim, J. M.; Heath, E. M. Toxicol.App. Pharmacol. 1983, 68, 177. (9) Oliver, B. G. Can. J. Fish. Aquat. Sci. 1984, 41, 878. 848
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(10) Neely, W. B.; Branson, D. R.; Blau, G. E. Environ. Sci. Technol. 1974, 8 , 1113. (11) Veith, G. D.; DeFoe, D. L.; Bergstedt, B. U. J . Fish Res. Board Can. 1979,36, 1040. (12) Mackay, D. Environ. Sci. Technol. 1982, 16, 274. (13) Chiou, C. T.; Freed, V. H.; Schmedding, D. W.; Kohnert, R. L. Environ. Sci. Technol. 1977, 11, 475. (14) Kenaga, E. E.; Goring, C. A. I. In “Aquatic Toxicology”; Eaton, J. G.; Parrish, P. R.; Hendricks, A. C., Eds.; American (15) (16) (17) (18) (19) (20) (21) (22) (23)
(24) (25) (26) (27) (28) (29)
(30) (31)
(32) (33) (34) (35) (36) (37) (38) (39) (40) (41) (42) (43) (44) (45)
Society for Testing and Materials: Philadelphia, PA, 1980; ASTM S T P 707, pp 78-115. Spacie, A.; Hamelink, J. L. Environ. Toxicol. Chem. 1982, 1, 309. Bruggeman, W. A,; Opperhuizen, A.; Wijbenga, A.; Hutzinger, 0. Toxicol. Environ. Chem. 1984, 7, 173. Southworth, G. R; Keffer, C. C.; Beauchamp, J. J. Enuiron. Sci. Technol. 1980, 14, 1529. Southworth, G. R.; Keffer, C. C.; Beauchamp, J. J. Arch. Enuiron. Contam. Toxicol. 1981, 10, 561. Neely, W. B. Enuiron. Sci. Technol. 1979, 13, 1506. Banerjee, S.; Sugatt, R. H.; O’Grady, D. P. Environ. Sci. Technol. 1984, 18, 79. Oliver, B. G.; Bothen, K. D. Anal. Chem. 1980,52, 2066. Oliver, B. G.; Nicol, K. D. Chromatographia 1982,16,336. McCrea, R. C. “Development of an Aqueous Phase Liquid-Liquid Extractor”, Ontario Region, Water Quality Branch, Burlington, Ontario, 1982, Interim Report, Inland Waters Directorate. Oliver, B. G.; Niimi, A. J. Environ. Toxicol. Chem. 1984, 3, 271. Niimi, A. J.; Oliver, B. G. Can. J. Fish Aquat. Sci. 1983, 40, 1388. Skea, J. C.; Simonin, H. J.; Jackling, S.; Symula, J. Bull. Enuiron. Contam. Toxicol. 1981, 27, 79. Bahig, M. E.; Kraus, A,; Klein, W.; Korte, F. Chemosphere 1981, 10, 319. Sanborn, J. R.; Metcalf, R. L.; Bruce, W. N.; Lu, P. Y. Environ. Entomol. 1976, 5, 533. Hansch, C.; Leo, A. “Substituent Constants for Correlation Analysis in Chemistry and Biology”; Wiley: New York, 1979. Kaiser, K. L. E. Chemosphere 1983, 12, 1159. Lech, J. J.; Glickman, A. H.; Statham, C. N. In “Pentachlorophenol Chemistry, Pharmacology and Environmental Toxicology”; Rao, K. R., Ed.; Plenum Press: New York, 1978; pp 107-114. Zitko, V.; Carson, W. G. Chemosphere 1977, 6, 293. Niimi, A. J.; Cho, C. Y. Can. J . Fish. Aquat. Sci. 1981,38, 1350. Hassett, J. P.; Yin, C. Q. presented at the 27th Conference on Great Lakes Research, St. Catharines, Ontario, 1984. Konemann, H.; Van Leeuwen, K. Chemosphere 1980.9,3. Banerjee, S.; Yalkowsky, S. H.; Valvani, S. C. Environ. Sci. Technol. 1980,14, 1227. Chiou, C. T.; Schmedling, D. W. Environ. Sci. Technol. 1982, 16, 4. Konemann, H.; Zelle, R.; Busser, F.; Hammers, W. E. J . Chromatogr, 1979, 178, 559. Wataral, H.; Tanaka, M.; Suzuki, N. Anal. Chem. 1982,54, 702. Kurihara, N.; Uchida, M.; Fujita, T.; Nakajima, M. Pestic. Biochem. Physiol. 1973, 2, 383. O’Brien, R. D. In “Environmental Dynamics of Pesticides”; Hague, R.; Freed, V. H., Eds.; Plenum Press: New York, 1974, pp 331-342. Bruggeman, W. A.; Van Der Steen, J.; Hutzinger, 0. J . Chromatogr. 1982,238, 335. Chiou, C. T. Environ. Sci. Technol. 1985, 19, 57. Quayle, 0. R. Chem. Rev. 1953, 53, 439. Hesselberg, R. J.; Nicholson, L. W. J . Environ. Qual. 1981, 10, 315.
Environ. Sci. Technol. 1985, 19,849-854
Tooby, T. E.; Durbin, F. J. Environ. Pollut. 1975, 8, 79. Roberta, J. R.; DeFreitas, A. S. W.; Gidney, M. A. J. J . Fish Res. Board Can. 1977, 34, 89. Niimi, A. J.; Cho, C. Y. Can. J. Fish. Aquat. Sei. 1981,38, 1350.
(49) Thomann, R. V.; Connolly, J. P. Environ. Sci. Technol. 1984, 18, 65.
Received for review October 25, 1984. Revised manuscript received March 18, 1985. Accepted April 4, 1985.
The Production of Organic Nitrates from Hydroxyl and Nitrate Radical Reaction with Propylene P. 6. Shepson," E. 0. Edney, T. E. Klelndlenst, J. H. Plttman, and G. R. Namle
Northrop Services, 1nc.-Environmental Sciences, Research Triangle Park, North Carolina 27709
L. T. Cupltt Atmospheric Sciences Research Laboratory, U S . Environmental Protection Agency, Research Triangle Park, North Carolina 277 11 Measurements of the gas-phase production rates of a-(nitrooxy)acetone, propylene glycol dinitrate (PGDN), 2-hydroxypropyl nitrate (ZHPN), and 2-(nitrooxy)propyl alcohol (2-NPA) in a C3H6/NZO5/airdark reaction and a C3H6/N0,/air irradiation are reported. The probable operative reaction mechanisms are discussed, and the branching ratios for peroxy radical reaction with NO via ROz + NO RONOZvs. ROz + NO RO + NO2 are estimated for CH3CH(OO)CHz0Hand CH3CH(OH)CH 2 0 0 radicals.
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Introduction Recently there has been increased interest in the reactions of the nitrate (NO,) radical with olefins. It has been shown (1) that these reactions can be important nighttime removal processes for this class of hydrocarbon. In addition, we have recently determined that organic nitrates might represent a significant contribution to the observed mutagenic activity of irradiated hydrocarbon/oxides of nitrogen (HC/NO,) mixtures (2). It is therefore of importance to determine the rate constants and reaction mechanisms for those chemical reactions occurring in urban atmospheres that lead to the production of organic nitrates. In the case of propylene (C3H6),its reaction with NO, has been reported to produce propylene glycol dinitrate (PGDN) in significant yields (3). It is desirable to know the yield of PGDN from irradiated C,H6/N0, mixtures under atmospheric conditions since PGDN is a toxic compound ( 4 , 5). The NO3 radical is produced from reaction 1 and is in O3+ NOz NO, + Oz (1)
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NO3 + NO2 (+M) + NzO5 (+M)
(2, -2)
equilibrium with N206when NO2 is present (reactions 2, -2). The reaction of N205 with C3H6has been shown to produce large yields of PGDN (6); however, the Nz05 concentrations in this case were fairly high (-29 ppm), and the PGDN yield probably depends on the Oz/N02 ratio. We have, therefore, conducted smog chamber investigations of the C3H6/N2O5reaction and of the irradiated C3H6/N0, system at low parts per million reaction levels to better establish the reaction mechanism and yields for the production of organic nitrates,
Experimental Section Experiments were conducted in a 22.7-m3Teflon smog chamber constructed of a 7.5 m long cylindrical Teflon bag 0013-936X/85/09 19-0849$01.50/0
connected on each end to 1.96 m diameter aluminum end plates coated with fluorocarbon paint. The C3H6/N2o5 experiment was conducted first by filling the chamber to 0.68 ppm of ozone (0,) by using a Welsbach Model T408 0, generator supplied with hospital-grade oxygen (MG Scientific). The chamber was then brought to 1.60 ppm of NO2 by adding the appropriate volume of a 1.06% mixture of NO2 in Nz (MG Scientific). This should therefore yield 0.68 ppm of Nz05,with 0.24 ppm of excess NOz. The reaction chamber C3H6concentration was then quickly brought to 1.85 ppm by adding a small volume of a 2.08% mixture of C3H6in N2 (MG Scientific). Halfway through this experiment, NO was added at 1.2 ppm by injecting a sample from a 1.0% mixture of NO in N2 (MG Scientific). Clean air (dry) was produced by using an AADCO clean air generator supplied with compressed air from a Quincy Model 325-15 air compressor. Dilution air at 14 L/min was maintained with a Teledyne HastingsRaydist Model NAHL-5P mass flow controller. The C3H6/N0, irradiation was conducted by similarly bringing the chamber to 0.82 ppm of C3H6,0.20 ppm of NOz, and 0.50 ppm of NO. The air for the C3H6/N0, irradiation only was humidified by using a Sonimist Model 600-L ultrasonic spray nozzle. Irradiation of the reactor was provided with 180 GE F-40blacklight bulbs and 36 sunlamps. As a check on the mechanism (see Results and Discussion) a separate set of experiments was conducted in 50-L Teflon bags. In these experiments CH,ONO was irradiated in the presence of 3 ppm of C3H6, 1ppm of NO, and either -0.5 or -11 ppm of NOz. The contents were then analyzed for 2-hydrokypropyl nitrate (2-HPN) and 2(nitrooxy)propyl alcohol (2-NPA) as described below. CH30N0 is used in these experiments as a source of OH radicals. It was prepared according to the procedure of Taylor et al. (7). Propylene was measured by using a Varian Model 1400 gas chromatograph (GC) containing a stainless steel column packed with 80/100 mesh Porapak QS, operated at an N2 flow rate of 20 cm3/min and a column temperature of 130 "C. Injection was performed by using a solenoidactuated Seizcor six-port valve, switched on and off with a Chrontrol Model CD timer. Calibrations were performed by preparing samples of 1 ppm of C3H6in air in Teflon bags with pure C3H6(MG Scientific). NO and NO, were measured by using a Monitor Labs Model 8440 nitrogen oxide analyzer calibrated with a certified standard of NO in Nz (MG Scientific). Ozone was measured by using a Bendix Model 8002 0, analyzer calibrated with a Dasibi
0 1985 American Chemical Society
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Environ. Sci. Technol., Vol. 19, No. 9, 1985 849
