Environ. Sci. Technoi. 1904, 18, 721-723
These comparisons are for commercial fish only and do not include the sport fish such as trout and salmon which generally have high levels of many organochlorine contaminants including TCDD along with a high lipid content: NYS (2) has the most complete information on these species. These levels and frequencies by species appear valid for Lake Ontario and the Saginaw Bay region of Lake Huron. Substantial data from NYS (2) and more limited sampling from HPB (3, II), OME (3), and Stalling et al. (5) point to a lower level and incidence for Lake Erie, Michigan, and Superior and possibly other parts of Lake Huron. The data (6) from Michigan rivers, however, are puzzling. Even though substantial levels (many over 100 ppt) were found in carp and some white suckers in rivers flowing into Saginaw Bay, a lower incidence but still high levels were found in other Michigan rivers. The origin and occurrence of these positive values remains unexplained. A further observation in finding TCDD levels in fish appears to be one of size. Zabik et al. (12) found a positive correlation between PCB level and size (length and/or weight) for carp from Lake Huron. Some species of adult fish with high levels of 2,3,7,8-TCDD also have a large size (e.g., channel catfish and carp), and many with a small adult size (less than 250-300 cm) have little or no dioxin contamination. This trend is particularly evident for the related Ictalurus species where brown bullhead has a lower TCDD contamination than the larger channel catfish. Moreover, related information from NYS and OME from such large sport species as trout (brown, rainbow, and lake) and salmon (Atlantic, Coho, and Chinook) tends to support this classification of TCDD level by fish size. This work is the f i s t report using validated methodology to document that 2,3,7,8-TCDD is a relatively commonly occurring contaminant of Lake Ontario commercial fish (about one-fifth of the 62 samples contained levels over 10 ppt). Certain species such as channel catfish, American eels, and rainbow smelts had the highest levels, and these were associated with a high PCB and lipid content of the fish. Comparison of dioxin data from several laboratories shows highest concentrations in channel catfish and carp from Lake Ontario and a part of Lake Huron with indications that other areas of Great Lakes have lesser amounts.
Acknowledgments We are indebted to Luz Panopio for sample extraction and purification, to Barry Kennedy for the determination of the lipid values, and to P. Calway, formerly of Fisheries and Oceans Canada, for the PCB results. Registry No. TCDD, 1746-01-6.
Literature Cited (1) Harless, R. L.; Oswald, E. 0.;Lewis, R. G.; Dupuy, A. E.; McDaniel, D. D.; Hai, H. Chemosphere 1982,11,193-198. (2) O’Keefe, P.; Meyer, C.; Hilker, D.; Aldous, K.; Jelus-Tyror, B.; Dillon, K.; Donnelly, R.; Horn, E.; Sloan, R. Chemosphere 1983,12,325-332. (3) National Research Council Canada ”Polychlorinated Dibenzo-p-dioxins: Criteria for Their Effects on Man and His Environment”; NRCC: Ottawa, Canada, 1981;NRCC No. 18574,pp 169-187. (4) Schneider, F.,Food and Drug Administration, Detroit, MI, personal communication, 1983. (5) Stalling, D. L.; Smith, L. M.; Petty, J. D.; Hogan, J. W.; Johnson, J. L.; Rappe, C.; Buser, H. R. In “Human and Environmental Risks of Chlorinated Dioxins and Related Compounds“; Tucker, R. E.; Young, A. L.; Gray, A. P., Eds.; Plenum Press: New York, 1983;pp 221-240. (6) Kaczmar, S. W.; Zabik, M. .; D’Itri, F. M. “Abstracts of Papers”, 186th National Meeting of the American Chemical Society, Washington, DC, Aug 1983;American Chemical Society: Washington, DC, 1983;Paper No. 30. (7) Gilman, A. P.; Fox, G. A.; Peakall, D. B.; Teeple, S. M.; Caroll, T. R.; Haymes, G. T. J. Wild. Manage. 1977,41, 458-468. (8) Ryan, J. J.; Pilon, J. C.; Conacher, H. B. S.; Firestone, D. J. Assoc. Off. Anal. Chem. 1982,66, 700-707. (9) Ryan, J. J.; Pilon, J. C. J. Chromatogr. 1980,197,171-180. (10) Schmitt, C. J.; Ludke, J. L.; Walsh, D. F. Pestic. Monit. J. 1981,14,136-206. (11) Ryan, J. J., Lau, P.-Y.; Pilon, J. C.; Lewis, D. In “Chlorinated Dioxins and Dibenzofurans in the Total Environment”; Choudhary, G.; Keith, L. H.; Rappe, C., Eds.; Buttenvorths: Boston, 1983;pp 87-97. (12) Zabik, M.; Menill, C.; Zabik, M. J. Bull. Environ. Contamin. Toricol. 1982,28,592-598. Received for review May 13,1983.Revised manuscript received February 1, 1984. Accepted March 14,1984.
Improved Liquid Feed System for the Berglund-Liu Vibrating Orifice Monodisperse Aerosol Generator Edward B. Barr,’ Robert L. Carpenter, and George J. Newton Inhalation Toxicology Research Institute, Lovelace Biomedical and Environmental Research Institute, Albuquerque, New Mexico 87 185
rn An improved liquid feed system for the Berglund-Liu vibrating orifice monodisperse aerosol generator (VOMAG) is described. The feed system employs a positive-displacement pump and pulse dampener to provide an accurate solution feed rate to the VOMAG. Advantages over the syringe pump feed system are reduced orifice clogging, elimination of leaks, increased ease of operation, continuous flow-rate range, and large solution reservoir for increased run times. Solution feed rate to the VOMAG using this feed system was reproducible to &2%. The system was low cost and required only a simple calibration.
Introduction The Berglund-Liu vibrating orifice monodisperse aerosol generator (VOMAG) is a commercially available instrument (Model 3050, Thermo Systems, Inc., St. Paul, MN) 0013-936X/84/0918-0721.$01.50/0
that can produce highly monodisperse aerosols in the size range 0.5-15 bm. Berglund and Liu (1) employed the vibrating orifice (2,3)to generate particles of a known size with an accuracy of 2 % Figure 1shows the major components of the generator. Liquid is fed to the generator at a controlled rate and forced through a small orifice mechanically coupled to a piezoelectric ceramic crystal. The crystal is vibrated at a known frequency by applying an ac voltage to the crystal, and vibration is transmitted to the orifice. The liquid jet formed by forcing solution through the orifice breaks up into uniform droplets for a given range of frequencies. The size of the droplet can be calculated by using the equation
0 1984 American Chemical Society
.
Environ. Sci. Technol., Vol. 18, No. 9, 1984
721
A Si S E M B L Y \
SIGNAL GENERATOR
INLET
1
DISPERSION AIR
DILUTION AIR
+MAIN
OUTPUT
G L S s E
VALVE
FILTER
1
=
e
A
Figure 3. Schematic of posltive dlsplacement pump head depictlng motion of the piston.
U Flgure 1. Schematic Showing major components of the Berglund-LJu vibrating orifice monodisperse aerosol generator.
3001
SOLUTION RESERVOIR
n
3-WAY VALVE
1 rnl CALIBRATION
PIPET
UU
W
c a a
n
B
0
it 100
PDP MOTOR AND
9
DRAIN V A L V E
PULSE DAMPENER
1
Flgure 2. Schematic showing major components of the modified liquid feed system.
where Dd = droplet diameter (cm), Q = liquid flow rate (cm3/s), and f = applied frequency (Hz). The liquid feed system is a major component of the VOMAG. As supplied, it consists of a syringe pump that forces liquid through a membrane filter into the aerosol generator at a controlled rate. However, in VOMAG use we have encountered several problems related to the syringe pump type feed system: (1)the small orifice often clogs, (2) the liquid syringe leaks around the plunger at an indeterminant rate, (3) generation run time is limited by the size of the syringe (this is critical for the 5-pm orifice, which requires that a 5-mL syringe be used with the syringe pump to obtain proper flow),and (4) discrete flow-rate settings of the syringe pump limit operating ranges. A liquid feed system has been designed that uses a positive displacement pump (PDP), resulting in reduced orifice clogging, leak-free operating, increased run time, and continuous liquid flow-rate range.
Methods Liquid Feed System. The major components of the modified liquid feed system are shown in Figure 2. They are the liquid reservoir, the PDP and pump head, the pulse dampener, and the in-line filter. 722
Environ. Sci. Technol., Voi. 18, No. 9, 1984
I
10
I
1
20
30
I
40
50
MICROMETER SETTING (mils)
Figure 4. Flow calibration of positive displacement pump with ’/&. diameter piston showlng setting vs. volumetric flow rate.
The liquid reservoir is a 30-mL or larger glass syringe connected to a three-way valve that delivers solution to the pump by gravity feed and from a 1-mL pipet. This provides a simple method for calculation of pump flow rate. The positive displacement pump (Model RP-SY, Fluid Metering, Inc., Oyster Bay, NY) is a highly accurate fluid pump with a reproducible metering accuracy of less than 2 %. Figure 3 shows details of the pump head with l/e-in. diameter piston. As the piston rotates, it reciprocates in synchronous motion such that there is one pressure stroke and one suction stroke for each piston revolution. A flat on the piston connects the input and output ports alternately with the piston chamber for each suction and pressure stroke. Varying the length of the stroke changes the volumetric output. The angle between the piston drive arm and the motor drive controls the stroke length and hence the volumetric output. The angle can be precisely set by using a micrometer. The pump produces a pulsed output that must be dampened with a diaphragm-type pressure regulator (Fluid Metering, Inc., Oyster Bay, NY). This provides steady flow to the Berglund-Liu generator. The in-line filter removes solution impurities that may clog the orifice. Calibration. Calibration of the positive displacement pump flow system uses a simple technique employing a 1-mL pipet. The pipet is filled with solution, and with the pump at a selected micrometer setting, the time required
Environ. Scl. Technol. 19a4, 18, 723-726
to empty the pipet is recorded. Flow rate is equal to the pipet volume (1 mL) divided by time (min). Figure 4 shows the calibration curve for flow rate vs. micrometer setting.
Results and Discussion The positive displacement pump feed system was employed with the VOMAG to generate oleic acid aerosols. Operation of the feed system showed reproducibility of flow rate for a given setting of f2.2% or less. The stability of the liquid jet for the operating range indicated that the aerosol produced was highly monodisperse (I). Start up of the Berglund-Liu generator is much easier with the PDP feed system than with the syringe pump feed system. This is due to the much higher operating pressure (up to 100 psig) of the positive displacement pump. Higher operating pressure has also reduced orifice clogging, especially for 5- and 10-pm orifices. Generation time of the VOMAG was increased with the positive displacement pump feed system because of the 30-mL solution reservoir. Continuous generation of up to 8 h has been accomplished, and longer generation times are feasible. The range of flow rates with the positive displacement pump feed system is continuous from 0 to over 1mL/min. This is critical for selecting the optimum flow rate for a given orifice. For example, when a 5 p m orifice is used with the syringe pump feed system, the flow rate can be stepped up from 0.039 to 0.051 mL/min. The optimum flow rate for the 5-pm orifice was between these flow rates. At the 0.039 mL/min flow rate, the orifice would not operate
without clogging within a few minutes. A t the 0.051 mL/min flow rate, the syringe pump would build up too much pressure and disengage from the syringe. The flow rate with the positive displacement pump feed system has been varied from 0.045 to 0.071 mL/min without problems.
Conclusions The PDP feed system has been used to improve the operation of the Berglund-Liu aerosol generator. The modified feed system has reduced clogging of the orifices, provided longer generation time, and provided a wider range of solution flow rates. The positive displacement pump is inexpensive, makes it simple to calibrate flow rates, and can be easily installed in the VOMAG system. Acknowledgments We gratefully acknowledge the assistance of Y. S. Cheng, J. A. Pickrell, J. H. Diel, and H. C. Yeh for technical review of the manuscript and E. E. Goff for illustrations.
Literature Cited (1) Berglund, R. N.; Liu, B. Y. H. Enuiron. Sci. Technol. 1973, 7, 147-153. (2) Wedding, J. B. Enuiron. Sci. Technol. 1975, 9, 673-674.
(3) Wedding, J. B.; Stukel, J. J. Enuiron. Sci. Technol. 1974, 8, 456-457.
Received for review October 11, 1983. Accepted April 2, 1984. This research was performed under US.Department of Energy Contract DE-ACOI- 76EV01013.
Seasonal Variations in Ambient Atmospheric 1.evels of Formaldehyde and Acetaldehyde Roger L. Tanner' and Zhaokun Meng'
Environmental Chemistry Division, Department of Applied Science, Brookhaven National Laboratory, Upton, New York 11973
rn A simple technique is described for determining ambient atmospheric levels of formaldehyde and acetaldehyde by using impinger collection in acidified 2,Cdinitrophenylhydrazine/acetonitrile solution and direct high-pressure liquid chromatography with UV absorbance detection of the corresponding phenylhydrazone solution on reversedphase columns. A limit of detection of -1 ppb for l-h impinger collections is obtained. Data from a coastal NE U.S.site show no discernible diurnal trends, but strong seasonal variations in the levels of both aldehydes are observed, with summer maxima and winter minima. Formaldehyde/acetaldehyde ratios are relatively high (>4) in winter and spring and low (
