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Migration of Polychlorinated Biphenyls in Soil Induced by Percolating Water by E. S. Tuckeii, W. J. Litschci, and W. M. Mees Monsanto Company BOO N. Lindbergh Boulevard St. Louis, Mo. 63166 The thermal and chemical stability of the polychlori nated biphenyls (PCBs) are clearly responsible for their widespread use in the electrical industry. Un fortunately, many of the environmental concerns about PCBs are attributable to the same properties. Where fire resistance and efficient transmission of electri cal energy are important, PCBs are the preferred di electrical fluid. In fact, the U.S. Government's Interdepartmental Task Force on PCBs, PCBs IN THE ENVIRONMENT (1972), concluded that for closed systems such as transformers and capacitors there are no suit able replacement products for PCBs, Consistent with these conclusions, Monsanto introduced a new PCB product, Aroclor* 1016, containing substantially less of the degradation resistant higher chlorinated iso mers, restricted the sales to use in closed systems, and set up a high temperature incinerator for disposal of used fluids. While incineration is an acceptable solution to the disposal of used fluids, it is not feasible for many reasons at this point in time for disposal of PCB impregnated material from transformers and capacitors. The objective of this study was to produce data which would help evaluate the suitability of landfill dis posal of Aroclor 1016 impregnated capacitors. Of prime concern was the rate at which percolating ground water might leach Aroclor 1016 from various types of soils. Experimental The experimental procedure employed consisted of per colating water through a column packed with soil coated with Aroclor 1016 and then monitoring the ef fluent water for PCBs. The set up used is shown schematically in Figure 1, The soil columns employed are approximately 3" in diameter by 12" in height and were dry packed in layers. Each soil layer being 3" * Registered trademark of Monsanto Company 86 Bulletin of Environmental Contamination & Toxicology, Vol. IS. No. I fc 1975 by Sptinger-Verlai New York Inc. DSW 025271 STLCOPCB4009227 thick - first uncoated soil, followed by soil coated with 2.St (w/w) of AtocIot 1016, and finally another layer of uncoated soil. An acetone solution of Aroclor 1016 was used to coat the air dried soil, fol lowed by removal of the acetone in a rotary evaporator Three different types of soils were used in this study. The characteristics of each are shown in Table I. TABLE I COMPOSITION OF SOILS USED IN STUDY Soil Norfolk Sandy Loam Ray Silty Loam Drummer Silty Clay Loam % Sand % Silt % Clay % Organic Carbon 82.5 11.0 5.5 1.0 6.2 83.2 9.6 1.0 2.8 55.U 35.8 6.0 The intent was to simulate the various soil types which could be encountered at different landfill sites The soils and the procedure employed have been used to evaluate the soil mobility of agricultural chemicals. Distilled water was fed from the reservoir at a con stant pressure to each soil column. The flow rates were observed to increase the first few days, and then decrease and level out. Apparently, after the wetting phase some channeling occurs until the soil becomes compressed in the column. This effect was most pronounced with the silty soils. The average flow rates in liters/day for Norfolk Sandy Loam, Ray Silty Loam and Drummer Silty Clay were 0.26, 0.53 and 0.32, respectively. The effluent water from the soil column was in turn passed through a polyurethane foam column which quan titatively absorbs PCBs, GESSER (1971). Sampling was carried out on a periodic basis by interchanging a new polyurethane foam column for the old column. In this manner, the effluent could be continuously monitored. The PCBs were recovered from the polyurethane by elution with 20 ml of acetone followed by 100 ml of B8 DSW 025273 nanograde hexane and collected in a 250 ml separatory funnel. The aqueous phase was discarded and the hex ane layer was filtered through anhydrous sodium sul fate into a Kunderna-Danish evaporative concentrator. The hexane concentrate was transferred to an aluminat column and eluted with 125 ml of hexane. The hexane eluent was concentrated in a Kunderna-Danish evapora tive concentrator and analyzed using a gas chromato graph equipped with an electron capture detector. The conditions for the gas chromatographic analysis were as follows: Instrument: Hewlett-Packard Model 5753A Gas Chromatograph (N[--63 Electron Capture Detector) Column: 2H x 1| mm ^ XE-60 silicone on 80/100 Mesh Chromosorb W High Performance - Glass Injection Port Temperature: Column Temperature: Detector Temperature: Carrier Gas: Purge Gas: Pulse Internal: 220C 170C Isothermal 300C Hellum, 60 ml/mln. 10% Methane/Argon, 50 psec 120 ml/mtn. Results and Discussion The polyurethane foam columns were changed and analyzed on days 5, 10, 17, 24, 31, 39, 52, 98 and 185. Table II summarizes the levels of PCBs found in the column effluents. Breakthrough of the PCBs in the effluent water was re lated to the clay content of the soil. The soils con taining higher levels of clay retained the PCBs. The order in which breakthrough occurred as a function of effluent volume was Norfolk Sandy Loam followed by Ray Silty Loam and finally Drummer Silty Clay Loam t Alumina, chromatographic grade, 80/200 mesh, heated at 400C for 4 hours and deactivated with 5% (w/w) distilled wat.'r. 30g of alumina packed into a glass chromatographic column 25 cm x 20 mm O.D. topped with 2 cm of anhydrous sodium sul fate and washed with 75 ml of nanograde hexane before ad dition of sample. TABLE II PCBs FOUND IN PERCOLATING WATER Norfolk Sandy Loam Total Effluent ppb Volume (O PCBs Ray Silty Loam Total Effluent ppb Volume ($,) PCBs Drummer Silty Clay Loam Total Effluent ppb Volume il) PCBs 1.3-8.1 ND 2.7-18.1) ND 1.6-9.9 ND 10.1 ND 20.7 65 12.5 ND 13.5 23 27.6 92 16.6 ND 25.5 63 51-9 153 31.1) ND 1)8.1 63 $8.1 136 59.2 ND ND None detected, <1 ppb (none observed). This is in agreement with recent work, HAQUE (1974), demonstrating that clay has a high affinity for PCBs. Experimentally, the water solubility of Aroclor 1016 has not been determined; however, it is estimated to be in the range of 225-250 ppb. This estimate is based on the fact that Aroclor 1016 contains more of the less chlorinated, more water soluble isomers than does Aroclor 1242 which has a water solubility of 200 ppb. In all cases, the concentration of PCBs in the effluent water was less than the estimated solubility of Aroclor 1016 in water. The electron capture chromatograms shown in Figure 2 detail the isomer distribution of the PCBs observed in the effluent water. Aroclor 1242, the product formerly sold for use in capacitors, is shown at the top. The Aroclor 1016 which was coated on the soil is shown next, followed by the PCBs leached from the soils, and finally a less chlorinated member of the Aroclor series, Aroclor 1221, which was used as a standard for quantitation. The number above each peak indicates the dominant chlorobiphenyl in that peak. A comparison of the Aroclor 1242 and Aroclor 1016 chromatograms illustrates the reduction of the penta and higher chlorobiphenyls achieved in the man ufacture of Aroclor 1016. 90 DSW 025275 STLCOPCB4009230 STLCOPCB4009231 The isomer distribution of the PCBs in the effluent water is the result of differences in the water solubility and adsorption characteristics of the isomers in Aroclor 1016. It is evident that only the less chlorinated, more biodegradable PCBs, AHMED and FOCHT (1973a,b), TUCKER (1972), similar to Aroclor 1221, were leached from the soil. A degradation rate for Aroclor 1221 of 73 + 21% has been observed in semi-continuous activated sludge tests at feed levels of 1 and S mgs/24 hours, TUCKER (1972). Conclusions The results of this study clearly demonstrate that PCBs are not readily leached from soil by percolating water. In the worst case, less than 0.05% of the total Aroclor 1016 available (25,000 ppm) was leached from the soil during the entire four-month duration of these experiments. During this period of time approximately 50-100 liters of water were passed through the three soil columns, an amount of water roughly equivalent to 50-100 ft. of rainfall, assuming no run off. The ease of leaching Aroclor 1016 from the different types of soils was in the following order: Norfolk Sandy Loam>Ray Silty Loam>Drummer Silty Clay Loam. Additionally, it was observed that only the less chlor inated, more degradable homologs were leached from the soils. The results of this study support the conclusion drawn by the Michigan Water Resources Commission that land fills are only a minor source of PCB environmental contamination, HESSE (1971). Acknowledgements The authors wish to thank Dr. W. A. Darlington for pro viding the soils and his valuable assistance through out the study. References AHMED, M. and FOCHT, D. D,: Bull, of Environ. Contam. Toxicol. 10^, 70 (1973a). 92 DSW 025277 STLCOPCB4009232 wmm AHMED, M. and FOCHT, D, D.; Can. J. Microbiol, 19, 47 (1973b). GESSER, H. D. et al: Analytical Letters 12^, 883 (1971). HAQUE, R. et al: Environ. Sci. and Tech. 8_, 139 (1974). HESSE, J. L.: Summary of the Michigan Water Resources Commission PCB Monitoring Efforts (1971). PCBs in the ENVIRONMENT: National Technical Informa tion Service, U.S. Department of Commerce, Springfield, Virginia 221S1. HCOM-72-10419. TUCKER, E. S.: Monsanto Report, Assessment of the Biological Persistence of PCBs, presented to U.S. Government Interdepartmental Task Force on PCBs, Washington, D.C., May IS, 1972, STLCOPCB4009233