Photodegradation of mutagens in solvent-refined coal liquids

Abstract

SUMMARYThe purpose of this investigation was to evaluate any changes in the chemical composition and microbial mutagenicities of two representative solventrefined coal (SRC) liquids as a function of exposure time to sunlight and air. This information was desired to assess potential health hazards arising from ground spills of these liquids during production, transport and use. Results of microbial mutagenicity assays using Salmonella typhimurium TA98, conducted after exposure, showed that the mutagenicities of both an SRC-II fuel oil blend and an SRC-1 process solvent decreased continuously with exposure time to air and that the decrease was accelerated by simultaneous exposure to simulated sunlight. The liquids were exposed as thin layers supported on surfaces of glass, paper, clay or aluminum; but the type of support had little effect on the results. The contrast between these results and the reported increases of mutagenesis in organisms exposed simultaneously to coal liquids and nearultraviolet light suggested that short-lived mutagenic intermediates, e.g., organic free radicals, were formed in the liquids during exposure to light.The highest activities of microbial mutagenicity in the SRC liquids were found in fractions rich in amino polycyclic aromatic hydrocarbons (amino PAH). After a 36-hour exposure of the fuel oil blend to air in the dark, the mutagenicity of its amine-rich fraction was reduced by 65%; whereas a 36-hour exposure in the light reduced the mutagenicity of this fraction by 92%. Similar rates of reduction in mutagenicity were achieved in exposures of the process solvent. The mutagenicities of other chemical fractions remained low during exposure. Analyses showed that most of the amine components of both liquids contained less than four aromatic rings and that their concentrations generally decreased with exposure time. These results indicate that the microbial mutagenicities of the two SRC liquids may be expected to gradually decrease if they are spilled out of doors, with the rate of decrease dependent on their access to air and sunlight. However, one cannot be sure that all of the potential health hazards of these materials are reduced by such exposures si nee the _i. typhimurium TA98 test system has been reported to be relatively insensitive to potential mutagens in fractions of SRC liquids rich in neutral aromatic compounds.Electron spin resonance (ESR) measurements on the liquids showed free radical concentrations on the order of 5xlo 16 unpaired spins per gram before exposure. In darkness, this concentration decreased continuously during exposure to air, paralleling the decrease in mutagenicities of the samples. In simulated sunlight, the concentration of paramagnetic species rapidly increased within the first few minutes of illumination and then decreased with continued exposure. This behavior suggested that organic free radicals were the major paramagnetic species, although charge-transfer complexes may have also been present. The ESR spectra were not sufficiently resolved to identi...

Decommissioning samples from the Ft. Lewis, WA, solvent refined coal pilot plant: chemical analysis and biological testing

“…(The 14,000-ppm concentration of 6-aminochrysene [6-AC] in sample #2515-012-03 is believed to be a large contaminant that carried into this fraction.) These reductions in amino-PAH concentrations are consistent with the results of laboratory studies by Kalkwarf et. al.…”

“…The amino-PAH have been previously identified as the most mutagenic compounds found in coal-deri ved materials (Wilson et al, 1980;Guerin et al, 1980). The data are also in agreement with that of WCW1-319A aRepresents solvent-soluble portions, as previously described Kalkwarf et al (1984), Wright and Weimer (1984) and , who demonstrated that exposure of coal liquids to air and/or sunlight eliminated or greatly reduced the microbial mutagenicity of the materials. The data from these workers, along with the data for these three samples, would suggest that any of the site samples that had been exposed to environmental conditions would likely have low mutagenic activity as a result of the decreased amino-PAH content.…”

“…The amino-PAH concentrations in these sediment samples are markedly lower than the corresponding concentrations in the SRC-Il HO material (data given in Table 21) but higher than in the several environmental site samples that were analyzed. The sediments, because of their dark, anoxic environment, appeared to preserve the amino-PAH for longer than might be predicted based on the previously cited laboratory investigations (Kalkwarf et al, 1984;Wright and Weimer, 1984). ., ,o "' ' ' "'""'"'"'"'"'"'"0 J)-"'"'"'"'"''-''-' "'-"' u-o OJ~ ou:::•-.…”