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(38) Berens, A. R. J.-Am. Water Works Assoc. 1985, Nov, 57-64. (39) Vonk, M. W.; Veenendaal, G. Water Supply 1983,2,61-69. (40) Vonk, M. W. Permeation of organic compounds through pipe materials. Report No. 85, KIWA, Nieuwegein, The Netherlands, (in Dutch), 1985. (41) Veenendaal, G.; Verheijen,L. A. H. M.; Vonk, M. W. Effects of soil contaminants and piping materials on drinking water
quality. Report No. 86, KIWA, Nieuwegein, The Netherlands, 1985. Received for review April 7, 1989. Accepted August 24, 1989. We are grateful to the Natural Sciences and Engineering Research Council of Canada and to the Ontario government for financial support.
COMMUNICATIONS Residual Petroleum and Polychlorobiphenyl Oils as Sorptive Phases for Organic Contaminants in Soils Stephen A. Boyd" and Shaobai Sun Department of Crop and Soil Sciences, Michigan State University, East Lansing, Michigan 48824
The organic matter fraction of soils and sediments controls the sorptive uptake of nonionic organic contaminants (NOCs) and pesticides from water (1-3). Mechanistically, natural organic matter appears to function as a partition medium for the dissolution of NOCs (I,2). The uptake of NOCs by soils and sediments can be described by a simple linear equation of the form x j m = KC, where xjm is the solute concentration in soil, C is the equilibrium solute concentration in water, and K is the sorption coefficient. K can be normalized for the fractional organic matter content of soil (fom) to define a new constant KO, = K/fo,. It has been demonstrated that KO, values obtained for a compound on different soils converge to a relatively constant value such that KO, becomes a unique constant characteristic of the compound ( 4 ) . The relative invariance of the soil KO, value demonstrates that the organic matter fraction controls uptake of NOCs by soils, and that organic matter from different soils behaves similarily as a partition medium for NOCs. The established relationship between organic matter content and sorption of NOCs has greatly simplified the predictions of sorption of NOCs by soils and sediments. Once KO, is known for a compound, the K value on any soil or sediment can be estimated simply by knowing f,,. Fate and transport models now routinely use KO, values to assess the leaching potential of organic contaminants and pesticides. In this study, the role of residual petroleum and polychlorobiphenyl (PCB) oils as sorptive phases for organic contaminants in soils was evaluated and compared to that of natural soil organic matter. The soil-water distribution coefficients of pentachlorophenol (PCP), toluene, and 2-chlorobiphenyl in actual field soils contaminated with such anthropogenic organic phases are presented here. The results show that both natural organic matter and residual oil components of these soils act as partition media for organic solutes, with the latter being 10 times more effective as a sorptive phase.
from actual wood-preserving sites in Minnesota and Michigan, respectively, and are contaminated with pentachlorophenol. The MG silt clay sample was obtained by allowing the sand-sized particles to settle out of an aqueous soil slurry. The soil denoted PP is contaminated with Aroclor 1254 as a result of a transformer spill at a Minnesota power plant. The Capac soil is an uncontaminated subsurface soil with a high clay content. Soil Properties. Pentachlorophenol was extracted with methylene chloride and analyzed as described previously (5). The PCB content was measured as described previously (6). Oil and grease content was determined by mixing 20 g of soil, acidified to pH 2 with HC1, and 10 g of MgS04. The sample was extracted with 200 mL of 1,1,2-trichlorotrifluoroethanein a Soxhlet for 20 h. The extract was back-extracted with 0.1 M KCO, (pH 12) to remove PCP and then evaporated. The oil and grease remaining was determined gravimetrically. A 1:2 soilwater mixture was used for pH determination. Organic carbon was determined by measuring COz released from combustion; analysis was by Huffman Laboratories, Inc., Golden, CO. The sample was previously extracted with methylene chloride to remove PCP or PCBs and oiljgrease. Organic carbon (OC) X 1.74 equals organic matter (OM). Particle-size analysis was by the Michigan State University Soil Testing Laboratory. Sorption Isotherms. The MG, MG silt + clay, PP, and UP isotherms were obtained by using [ring-14C]PCP, -toluene, or -2-chlorobiphenyl (from Sigma) and the concentrations plotted are for the 14Ccompound. The Capac isotherm (data not shown) was obtained by adding 5 pL of a [14C]PCP-methanol solution and different volumes of aqueous nonlabeled PCP to soil. Standard batch equilibration isotherms were obtained by mixing from 2 to 10 g of soil, 20 mL of distilled H,O, and various amounts of PCP, toluene, or 2-chlorobiphenyl in screw-top glass centrifuge tubes that were closed with aluminum foil lined caps. After 24 h, aqueous-phase concentrations were measured by liquid scintillation counting.
Materials and Methods
Results and Discussion In studies of PCP sorption by PCP-contaminated soils
Soils. Three soils and a soil particle-size fraction were used in the study. Two soils, designated MG and UP, are
from former wood-preserving sites we observed that the measured PCP distribution coefficients were much higher
Introduction
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Table I. Soil Properties property PCP, ppm organic matter, %
oc
MG
silt
MG clay
+
UP
PP Capac Bt
740
2470
624
0
0
1.81 3.15 0.97 0 7.581
12.51 21.79 7.6 0 7.353
0.29 0.51 0.24 0 5.617
1.25 2.18 0 0.73 8.75
0.40 0.70 0 0 6.668
0.7 33.4 65.9
96.8 2.5 0.7
47 45 8
25 45 30
OM oil/grease, 70 PCB, % PH particle size, % sand (0.05-2.0 mm) 90.3 silt (0.002-0.05 mm) 4.9 clav ( Kow.In fact, a plot of log Kowversus water solubility for various organic compounds shows that 2-chlorobiphenyl falls below the ideal line by -0.7 log unit (11). Thus, the sorptive behavior of residual PCB oils appears similar in nature to that of residual petroleum. However, in the case of sorption of individual PCB congeners by residual PCB oils, nearly ideal solution behavior is observed and KO,will be greater than Kow;the magnitude of this difference will increase for the more heavily chlorinated PCB congeners (11). The resulting effect of residual PCB oils on the soil-water distribution coefficient is dramatic; the K value predicted in the conventional manner, where only soil organic matter is acting as a sorptive phase, is -37, whereas the observed value is 702. These results demonstrate that residual petroleum and PCB oils present in soil act as highly effective partition media for organic contaminants. The presence of these highly sorptive anthropogenic organic phases in soils and sediments will significantly increase the immobilization of organic contaminants and thus strongly influence their environmental fate and behavior. The observed soil-water distribution coefficients of organic contaminants were accurately predicted from the soil organic matter content, the oil content (expressed as oil/grease or PCB content), and the solute Komand Kowvalues. The magnitude of the oil-water partition coefficient makes the residual oil phase a significant sink for organic contaminants in these systems. For accurate prediction of soil-water distribution coefficients in such soils and sediments, the oil compo-
nents, along with the natural organic matter component, must be measured and accounted for individually. The limited effectiveness of soil washing and pump and treat technologies (12, 13) for remediating soils contaminated by petroleum spills and PCBs may be related in part to the sorptive behavior of residual oil components as described here. Acknowledgments
We thank Dr. John Quensen, 111, for the PCB analyses and helpful discussions. Literature Cited (1) Chiou, C. T.; Peters, L. J.; Freed, V. H. Science 1979,206, 831-832. (2) Chiou, C. T.; Porter, P. E.; Schmedding, D. W. Environ. Sci. Technol. 1983, 17, 227-231. (3) Karickhoff, S. W.; Brown, D. S.; Scott, T. A. Water Res. 1979,13,241-248. (4) Chiou, C. T. In Reactions and Movement of Organic Chemicals in Soils;Sawhney, B. L., Brown, K., Eds.; Special Publication No. 22; Soil Science Society of America: Madison, WI, 1989; pp 1-29. (5) Mikesell, M. D.; Boyd, S. A. Environ. Sci. Technol. 1988, 22, 1411-1414. (6) Quensen, J. F., 111; Tiedje, J. M.; Boyd, S. A. Science 1988, 242, 752-754. (7) Cirelli, D. P. In Pentachlorophenol: Chemistry, Pharmacology and Environmental Toxicology;Rao, K. R., Ed.; Plenum: New York, 1978; pp 13-18. (8) Bartha, R. Microb. Ecol. 1986, 12, 155-172. (9) Schellenberg, K.; Leuenberger, C.; Schwarzenbach, R. P. Enuiron. Sci. Technol. 1984, 18, 652-657. (10) Lagas, P. Chemosphere 1988, 17, 205-216. (11) Chiou, C. T.; Schmedding, D. W. Enoiron. Sci. Technol. 1982, 16, 4-10. (12) Mackay, D. M.; Cherry, J. A. Environ. Sci. Technol. 1989, 23,630-636. (13) Bouchard, D. C.; Enfield, C. G.; Piwoni, M. D. In Reactions and Movement of Organic Chemicals in Soils; Sawhney, B. L., Brown, K., Eds.; Special Publication No. 22; Soil Science Society of America: Madison, WI, 1989 pp 349-371. Received for review September 14,1989. Accepted October 30, 1989. Partial support from the US.Environmental Protection Agency un,der Grant R-815750-01-0, BioTrol, Inc., and the Michigan Agricultural Experiment Station.
Ambient Formic Acid in Southern California Air: A Comparison of Two Methods, Fourier Transform Infrared Spectroscopy and Alkaline Trap-Liquid Chromatography with UV Detection Danlel Grosjean,*-t Ernest0 C. Tuazon,t and Eric Fujltag DGA, Inc., 4526 Telephone Road, Suite 205, Ventura, California 93003, Statewide Air Pollution Research Center, University of California, Riverside, Callfornia 92521, and Research Division, California Air Resources Board, P.O. Box 2815, Sacramento, California 95812
Introduction
Formic acid is an ubiquitous component of urban smog. Sources of formic acid in urban air include direct emissions from vehicles (1)and in situ reaction of ozone with olefins (2). Ambient levels of formic acid in southern California air were first measured some 15 years ago by Hanst et al. 'DGA, Inc. f
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f
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(3) using long-path Fourier transform infrared spectroscopy (FTIR). All subsequent studies of formic acid in the Los Angeles area have involved the use of two methods, either FTIR (4-6) or collection on alkaline traps followed by gas chromatography (I), ion chromatography (9, or liquid chromatography analysis with UV detection, ATLC-UV (2,8). The Carbon Species Methods Comparison Study (CSMCS), a multilaboratory air quality study carried out in August 1986 at a southern California smog receptor site
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