Envlron. Sci. Technol. 1985, 19, 322-327
Aylett, B. J. In “Comprehensive Inorganic Chemistry”; Bailar, J. C., Jr.; Emeleus, H. J.; Nyholm, R.; TrotmanDickenson, A. F., Eds.; Pergamon Press: Oxford, 1973. Newell, L. C.; Maxon, R. N.; Filson, M. H. Inorg. Synth. 1939,l , 19-20. Mellor, J. W. “A ComprehensiveTreatise on Inorganic and Theoretical Chemistry: Ra and Ac Families, Be, Mg, Zn, Cd, Hg”; Longmans, Green and Co.: London, 1923; Vol. IV, pp 842-961. Fuchs, L. H.; Nielsen, E. L.; Hubble, B. R. Thermochim. Acta 1978,26, 229-239. Pedram, E.; Hasanain, M. A.; Hines, A. L.; Duvall, J. J. In Situ 1979, 3 (4)) 331-352. Wilson, W. I.; Snyder, R. B.; Johnson, I. Ind. Eng. Chem. Process Des. Dev. 1980, 19, 47-51.
(34) Klusman, R. W.; Matoske, C. P. Environ. Sci. Technol. 1983, 17, 251-256. (35) Spencer, J. N.; Voigt, A. F. J . Phys. Chem. 1968, 72, 464-470.
Received for review December 9, 1983. Revised manuscript received September 26, 1984. Accepted October 18,1984. This research was supported by the Assistant Secretary for Fossil Energy, Office of Oil, Gas and Shale Technology, and by the Assistant Secretary for Environment, Officeof Environmental Compliance and Overview, Environmental Control Technology Division of the U.S. Department of Energy under Contract W-7405-ENG-48. First presentation of this work was at the Eleventh Oil Shale Symposium, Golden, CO, April 12-14,1978.
Groundwater Contamination by Volatile Halogenated Alkanes: Abiotic Formation of Volatile Sulfur Compounds under Anaerobic Conditions Ren6 P. Schwartenbach, Waiter Glger, Christian Schaffner, and Oskar Wanner SWISSFederal Institute for Water Resources and Water Pollution Control (EAWAG), CH-8600 Dubendorf, Switzerland
The investigation of a groundwater contamination caused by a leaking wastewater tank of a chemical plant revealed that in groundwaters, under highly reducing conditions in the presence of hydrogen sulfide, certain volatile bromo- and chloroalkanes may undergo secondorder nucleophilic substitution reactions yielding very persistent and hazardous volatile sulfur-containing com,pounds including dialkyl sulfides. Rate constants determined in the laboratory indicate that these nucleophilic substitution reactions may compete with hydrolysis, even at the low hydrogen sulfide concentrations typically encountered in the aquatic environment. H
Volatile halogenated hydrocarbons (i.e., halogenated alkanes, alkenes, and benzenes are ubiquitous groundwater pollutants (1-5). The major causes of groundwater contamination by such chemicals include leachates from chemical waste dumps (6))spills (7),infiltration of polluted surface waters (8,9), and leaching from the ground surface (e.g., pesticides ( 4 ) ) . Recent studies have shown that volatile halogenated hydrocarbons are rapidly transported in the ground and that many of these compounds are quite resistant to chemical and/or biological transformation under conditions typical for the subsurface (8-12). However, for some volatile halogenated hydrocarbons, chemical reactions (e.g., hydrolysis (13)) and/or biological transformation (9,11,12)may be important. In such cases, the crucial question is whether possibly harmful chemicals are formed which may accumulate in the subsurface. In this paper, we present evidence that in groundwater, in the presence of hydrogen sulfide, certain volatile halogenated alkanes can undergo nucleophilic substitution reactions, leading to the formation of persistent and hazardous sulfur-containing compounds. The data originate from the investigation of a groundwater contamination caused by a leaking wastewater tank of a chemical plant (see also preliminary report in ref 14). We report here the results of a field investigation and of laboratory experimenta conducted to support the hypotheses postulated for the reaction mechanisms responsible for the formation of the sulfur-containing compounds detected in the ground. Case History After the operation of a chemical plant (which manu322
Environ. Sci. Technol., Vol. 19, No. 4, 1985
Table I. Alkyl Halides Which Were Manufactured by the Chemical Plant and Which Were Likely to Have Been Present in the Wastewater compound name methyl iodide ethyl bromide n-propyl bromide isopropyl bromide n-butyl bromide isobutyl bromide sec-butyl bromide n-amyl bromide isoamyl bromide sec-amyl bromide 3-bromopropene 1-bromo-3-chloropropane 1-chloro-2-bromopropane 1,4-dibromobutane
molecular formula
abbreviation
production”
CH31 Me1 CH,CH,Br EtBr CH,CH;CH2Br n-PrBr (CH,),CHB; i-PrBr CHaCHsCHoCHoBr n-BuBr (CH,)~CHCH~B~ i-BuBr CH3CHzCH(CH,)Br sec-BuBr CHSCH2CH2CH2CH2Brn-AmBr (CHS)&HCH2CH2Br i-AmBr CH3CH2CH2CH(CH3)Brsec-AmBr CH2=CHCHzBr BrCHzCHzCH2Cl
I I I I I I I I11 I1 I I I
CH3CHBrCH2Cl
I11
BrCHzCHzCHzCHzBr
I1
“I = major product (>5 tons year-’); I1 = significant amounts produced (>0.5 ton year-’); I11 = minor product (
