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photoactive substances similar to picloram. It may be directly employed to examine all experimental depths with vertical mixing, including the limiting cases of very shallow and very deep systems. The framework can be employed to alter and minimize the number of experiments necessary to quantitize the photodegradation process. As an illustration, experiments with variations in depth can be eliminated. Further, direct solar intensity measurements should accompany the experiments. Direct extinction coefficient measurements a t the appropriate wavelength can be obtained, thus reducing the need to carry out several experiments at different locations and initial concentrations. For distilled water and ocean water, these data appear to be available. A set of measurements of the extinction coefficients a t appropriate wavelengths in several natural waters could be used to calculate the degradation rates associated with direct photodecomposition in the natural environment.
CCiOBES
Figure 4. Variation of solar radiation for Western Lake Erie ( 3 )
radiation measurements and their wide variation in the Great Lakes region are illustrated in Figure 4 ( 5 ) .The present study employed estimates of the monthly mean value for the solar radiation parameter which were 5-year averages and not for the study period. The experimental setup tends to average variations in solar radiation. This is fortunate from the standpoint that applications to the natural environment can be made employing broad averages of solar radiation. The framework that has been developed was employed to analyze experimental data collected employing a wide range of experimental conditions. Specifically, the numerical values for the coefficients K, and KO were obtained employing solution depths of 0.292 and 3.65 m with 4 hlday of light exposure in August and September (625-575 ly over the day). The numerical coefficients were then employed to analyze data for solution depths as low as 0.046 m and exposure to daily sunlight during July and March (daily solar radiation averages 725 and 500 ly). The framework therefore has correlated data obtained over a wide range of experimental conditions. Equation 4 is a general solution for low concentrations of
A framework that can be employed to analyze first order photodecomposition in aqueous solutions has been developed. The framework has been tested and adequately represents experiment data. I t can be employed to develop and evaluate experimental designs. Consideration can be given to use of the framework in developing projections of the concentration profiles of materials in the natural environment.
Literature Cited (1) Hvdroscience Research Reo.. Proiect No. HYDRID-02. “Photodlcomposition in Water”, Nov. 19?6. (2) Hedlund, R. T., Youngson, C. R., “The Rate of Photodecomposition of Picloram in Aqueous Systems”, “Fate of Organic Pesticides in the Aquatic Environment: Advances in Chemistry Series III”, American Chemical Society, U’ashington, D.C., p p 159-72, 1972. (3) Hydroscience Rep., prepared for California Dept. of Water Resources, “Western Delta and Suisun Bay Phytoplankton Model Verifications and Projections”, Oct. 1974. (4) Hirt, R. C., Schmitt, R. G., Searle, N. D., Sullivan, A. P., J . Opt. Soc. Am., 50 (7), 796-813 (1960). ( 5 ) Hydroscience Rep., prepared for Great Lakes Basin Commission, “Limnological Systems Analysis of the Great Lakes-Phase I”, Mar. 1973.
Received for revleu’ August 8, 1977. Accepted May 22, 1978. Work funded under Hydroscience, Inc., Research Project No. HYDRID92
Use of Benzaldehyde as a Selective Solvent for Sulfuric Acid: Interferences by Sulfate and Sulfite Salts Delbert J. Eatough’, Steven Iratt, John Ryder, and Lee D. Hansen Department of Chemistry, Thermochemical Institute, Brigham Young University, Provo, Utah 84602
Benzaldehyde has been proposed as a selective solvent for the analysis of H2S04in aerosols. Earlier work has shown that sodium and ammonium salts are not extracted in benzaldehyde. Benzaldehyde extractable sulfate and sulfite compounds in smelter flue dust samples that contain a wider variety of metal salts are studied. The results indicate that bivalent metal bisulfate salts and some sulfite salts (from samples 1276
Environmental Science & Technology
which extract with water to give a basic solution) are extracted with benzaldehyde. If the benzaldehyde contains benzoic acid, significant quantities of bivalent metal sulfate salts are also extracted, presumably due to the formation of benzoate salts and sulfuric acid in the extraction solution. Benzaldehyde thus appears to not be a selective solvent for &So4 if the aerosols analyzed contain bivalent metal sulfate compounds. 0013-936X/78/0912-1276$01 .OO/O @ 1978 American Chemical Society
_
_
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Table I. Composition of Flue Dustsa sample
PH
*
so:-
=
so:-
Cad
Fed
Cud
2nd
0.54f0.06 Copper-1 0.31 f 0.01 Copper-2 0.15 f 0.02 Lead-3 1.44 f 0.05 Lead-4 2.77 f 0.16 Lead-5 See refs. 20and 23. The pH resulting from extraction of -1-mg sample with 1 mL H20. Concentration of SO;- and SO:4.2f0.1 4.4 f 0.0 3.8 f 0.0 7.2 f 0.2 8 . 9 f 0.9
0.13f0.01 1.47f0.06 0.17 f 0.06 0.12 f 0.04 2.5 f 0.4 0.2 f 0.1 0.00 f 0.00 0.30 f 0.02 0.16 f 0.04 1.21 f 0.14
0 . 2 9 f 0 . 1 2 3 . 0 4 f 0 . 1 0 3.4 f 0 . 4 0.19 f 0.04 2.06 f 0.03 1.01 f 0.19 0.21 f 0.04 0.77 f 0.04 0.05 f 0.01 0.05 f 0.03 0.36 f 0.04 0.03 f 0.01 1.6 f 0.4 0.97 f 0.10 0.46 f 0.09
Pb
O.llf0.02 0.23 f 0.01 2.3 f 0.3 2.9 f 0.5 1.00 f 0.07
ASd
0.57f0.05 6.9 f 0.3 0.8 f 0.3 0.12 f 0.04 0.22 f 0.03
extractable in 0.1 M HCI, 2 5 mM
FeCI3, pnol/mg of sample. Total concentration of element, pmol/mg of sample.
Presently, there is much interest in the various effects of
SO, in the environment. Of particular concern is the role of SOz, H2S04,and related particulate emissions in the causation of adverse environmental effects. Sulfur dioxide and acidic aerosol sulfates have been implicated as the cause of a variety of adverse health effects because 'of their abundance in emissions ( 1 , 2 ) .The increase in the acidity of rainfall in the northeastern United States and parts of northern Europe during the past few decades has been attributed to sulfuric acid (34).Studies have generally failed to identify the specific sulfur-containing species (i.e., HzS03, H2S04, HSO,, etc.) responsible for observed acidity. This failure arises in part from the lack of quantitative analytical methods for the determination of specific species in a complex aerosol. The need to establish correlations between specific species and the observed effects of aerosols is critical. Although total amounts of sulfate in particulate samples can be quantitatively determined, methods available to characterize the specific sulfate species present often leave much to be desired. A t present, the most widely used techniques for identification of acid sulfate species in particulate matter involve the semiquantitative measurement of neutral and acid sulfate aerosols by nephelometric ( 7 , 8 )and infrared (9) techniques and the extraction of H2S04 from collected samples with organic solvents (10, 1I). A technique based on trapping H2S04 as an adduct of perimidylammonium bromide and determining H2S04by a ring oven (12) or volatilization ( 1 3 ) procedure has been reported. This method, however, is not specific for HzS04 due to positive interferences from other nonvolatile acids and possible negative interferences from basic substances. Several investigators ( 23-15) have developed instruments to monitor H2S04 by heating the collection filter to separate the H2S04 from other particulates. These techniques, however, have not been proved to be selective on actual samples. The various techniques for total H2S04 characterization of particulate samples have been discussed (16, 17). In particular, the disadvantages of a simple acid-base titration in determining the free sulfur acid in aqueous extractions have been enumerated (18, 19).The results of these investigations suggest that aqueous techniques may not be satisfactory. Clearly, a nonaqueous extraction technique for the selective extraction of HzS04, HSO,, and H2SO:3 in the presence of other sulfate salts is needed. A number of organic solvents that may be suitable for isolating atmospheric sulfuric acid have been investigated by Tanner and associates ( I O , 11, 17). These include methanol, ethanol, 2-propanol, tert- amyl alcohol, tert- butyl alcohol, p -dioxane, methyl isobutyl ketone, and benzaldehyde. The results of this survey indicate that benzaldehyde is a suitable solvent for the extraction of H2SO4 in the presence of Na2S04, NaHS04, (NH&S04, or NH4HS04. However, the solubility of other salts, specifically bivalent metal sulfates and sulfites, and the possible effect of impurities arising from benzaldehyde oxidation were not studied. We report here the results of a study of benzaldehyde extractable sulfate and sulfite species present in flue dust samples from copper and lead smelters. Bivalent metal sulfate
salts can be extracted from these samples by benzaldehyde. The type and quantity of salts extracted are markedly affected by the presence of benzoic acid in the benzaldehyde. Benzaldehyde is found to be useful as a selective solvent for H2S04 only if the levels of benzoic acid in the solvent are kept low and/or the possible presence of bivalent metal salts in the extraction solvent is checked.
Experimental Procedure Reagent grade benzaldehyde (Eastman) was further purified by vacuum distillation. Before distillation the apparatus was thoroughly flushed with argon, the chamber was evacuated, and the benzaldehyde distilled. Following distillation, the benzaldehyde was stored in an argon-filled vessel which was sealed to prevent entry of air or light. The stored benzaldehyde was used as quickly as possible following its preparation. Benzaldehyde extractable species in flue dust samples collected from two primary copper and three primary lead smelters were determined. A portion (-10 mg) of each flue dust sample was weighed and transferred to a Vacutainer tube. The tube was flushed with argon and from 6 to 10 mL of benzaldehyde reagent was injected into the tube. Each tube was then placed in an ultrasonic bath for -15 min. Following this, each sample was centrifuged, and an aliquot was transferred to a separate test tube. A 10-mL quantity of either H20 or a 0.1 M HC1,2.5-mM FeC13 solution was then injected into the aliquot. The resulting liquids were thoroughly mixed, and the benzaldehyde was separated from the aqueous phase by gravity for -3 h at room temperature. A 2.25-mL portion of the counter-extractant aqueous phase was analyzed for strong acid species and benzoic acid using a microtitration calorimeter containing a micro pH electrode and for sulfate by acidifying to 0.1 M HC1 and determining sulfate calorimetrically by precipitation with BaC12. The equipment and experimental procedures for these analyses have been described (20,21).The HCl, FeC1:I solutions were analyzed for S(1V) species and sulfate calorimetrically by a previously described procedure (21). Elemental content of the aqueous solutions was determined by analysis by proton induced x-ray emission, PIXE (22). Blank determinations were made on all solutions treated as above, except that the flue dust was absent. All work was done in an argon atmosphere. Results Total concentrations of sulfite, sulfate, and metals in the flue dust samples as well as the pH resulting from extraction of 1 mg of sample with 1 mL of H20 have been previously reported (20, 23) and are summarized in Table I. The quantity and type of sulfate salts extracted by the benzaldehyde depended on the concentration of benzoic acid impurity present in the benzaldehyde. Strong acid, sulfate, and metal ions fQund in extractions where the benzoic acid concentrations in the benzaldehyde were
