Environ. Sci. Technol. 1992, 26, 138-144
(26) Mopper, K.; Kieber, D. J. Deep-sea Res., in press. (27) Manahan, D. T.; Shilling, F. M.; Welborn, J. R.; Colwell, S. J. Antarct. J . US.,in press.
Received for review March 13,1991. Revised manuscript received July 11,1991. Accepted July 24,1991. This work was supported
by grants from NSFs Chemical Oceanography Program to K.M. (OcE87-10786)and R.D. (OCE89-23063) and from ONR's Advanced Research Initiative on marine aggregates (N00014-9151171 to K.M). L.C. gratefully acknowledges NATO for support of his participation in this study. C.G. thanks the L.S.G.M., Universitd Perpignan, France, and the Ministdre de la Recherche et de la Technologie Francais for financial support.
Chemical Speciation of Nickel in Airborne Dusts: Analytical Method and Results of an Interlaboratory Test Program Vladimir J. Zatka,*Vt J. Stuart Warner,$and David Maskeryg
Inco Limited, J. Roy Gordon Research Laboratory, Sheridan Park, Mississauga, Ontario, Canada L5K 129 H Analytical knowledge, qualitative and quantitative, of
the various nickel species present in the airborne dusts of nickel-producing and nickel-using workplaces is required for the assessment of nickel-related health hazards. A wet-chemical procedure is described which apportions the airborne nickel species into four categories: water soluble, "sulfidic", metallic, and "oxidic". The sample is leached in a sequence with ammonium citrate, hydrogen peroxideammonium citrate, and brominemethanol, each of which selectively dissolves a number of related nickel species. Each leach solution and the insoluble residue from the third leach are then analyzed for nickel. The underlying chemistry of each leaching step is discussed, and its selectivity and completeness is evaluated. Since real workplace samples usually contain a limited number of species which are linked to the feeds and processes used and the final products, this 4-fold categorization is generally adequate to speciate the sample. The suitability of various filter materials for sampling airborne dusts for the purpose of speciation is examined. Problems caused by natural alkalinity of glass fiber filters are discussed. The results of an international interlaboratory test program of this nickel speciation method are reported.
Introduction In the past, an increased incidence of respiratory cancer was associated with certain obsolete nickel-refining operations (1-3). The form(s) of nickel that may have been responsible for this risk have not been identified. This led some researchers and regulators to hypothesize that all forms of nickel should be considered as potential carcinogens. In contrast, extensive epidemiological studies have shown no nickel-related risk of cancer in the nickel-using industries (4-10) or in the great majority of occupations in the nickel-producing industry (11-14). Furthermore, numerous laboratory experiments have indicated significant differences in the carcinogenic potential of different nickel compounds (e.g., ref 15). Thus, assessment of health risks in the nickel industry requires the ability to distinguish quantitatively between the different species of nickel in airborne dust. In response to this need, Inco Limited has developed and tested selective leaches that discriminate between four groups of nickel species commonly found in nickel-producing and -using workplaces. +Present address: 483 Caesar Ave., Oakville, ON, Canada L6J 321. *Presentaddress: Inco Limited, P.O. Box 44, Royal Trust Tower, Toronto-Dominion Centre, Toronto, ON, Canada M5K 1N4. §Present address: Inco Limited, Central Process Technology, Copper Cliff, ON, Canada POM 1NO. 138
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No universal analytical technique capable of identifying as well as quantifying all nickel species present in airborne dust samples is known. Dust samples may be collected in relatively large quantities on high-volume filters or in minute amounts on personal sampling filters. Researchers are currently investigating both instrumental and wetchemical analytical methods. Instrumental approaches, such as laser microprobe mass spectrometry (LAMMS) (16) or extended X-ray absorption fine structure (EXAFS) and related X-ray absorption near-edge structure (XANES) spectroscopies (17), focus on characteristics of atoms, less often molecules, while examining very small areas of the sample to the depth of only a few micrometers. This limitation can cause problems during calibration and speciation as minute amounts of airborne dust often are not distributed uniformly on collection filters. Intraparticle heterogeneity and encapsulation phenomena, common in industrial dusts, are further sources of difficulty whenever analytical examination is restricted to only a small number of dust particles. Last, but not least, few laboratories have access to the sophisticated instruments and to researchers with the experience needed to correctly interpret results. Physical electromagnetic separation of metallic nickel from water-soluble nickel salts and insoluble nickel oxides was described recently (18,19). By its nature, such a method is limited to samples consisting of discrete homogeneous particles which allow a clean physical separation of magnetic metallic5 from nonmagnetic oxides. Phase encapsulation and/or the presence in the sample of magnetic nickel-bearing spinels would make the method not applicable. The present paper describes a wet-chemical speciation method which exploits the differences in chemical properties of the various nickel phases found in dusts in nickel-producing and -using workplaces. Such an approach may lack the specificity of an instrumental method as it can only differentiate among groups of similarly reacting nickel compounds rather than individual species. However, the chemical speciation (20) has an overriding advantage in that it can be utilized by less sophisticated moderately equipped chemical laboratories. Furthermore, chemical methods use a larger portion or all of the dust on the filter, so nonuniform deposition or intraparticlephase variability is not a problem. On the other hand, wet-chemical speciation, which is a form of phase analysis, is seldom as simple and accurate as conventional chemical determinations of total elemental contents. This is especially true in the analysis of personal sampling filters with total dust deposits of 99% removal of all aromatic solutes was achieved at 787 krad (7.87 kGy, [OH'] 2.2 X M) with influent concentrations of each of the solutes approximately 1pM, whereas in the secondary wastewater) solute removal was 91-96% for similar initial concentrations. At an initial solute concentration of approximately 20 bM, for each of the four aromatic solutes, the removal increased in absolute concentration but the percent removal in both waters decreased. Reaction byproducts identified were phenols and various carbonyl compounds. The carbonyl compounds include glyoxal and other as yet unidentified aldehydes. The product distribution is consistent with hydroxyl radical (OH') addition and continued oxidation of intermediate byproducts.
Introduction As a result of increased urbanization and industrialization, groundwaters have become contaminated with anthropogenic organic compounds. Many of these compounds persist for considerable periods in the subsurface environment. One such group of compounds which has attracted special interest, because of their occurrence in wastewater) groundwater, and surface water, is the aromatic hydrocarbons, specifically,benzene, toluene, and the xylenes (BTXs) (1). The prevalence of these compounds in the environment is due to their high production and use worldwide (2-4). In particular, these compounds are important constituents of gasoline and other commercial fuels, having an aromatic content of up to 45% (5). Known mechanisms of transport to the environment include inadvertent dumping, leaking underground storage tanks, landfill leachate, and reentry into the hydrosphere in rain (6). As a result of their widespread occurrence) considerable research is being conducted on processes for re144
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moving these compounds from contaminated environments. Several methods have been proposed and/or are currently used to remove hazardous chemicals from contaminated waters, for example, carbon adsorption (7-12), oxidation using ozone (13,14), and aeration stripping (15-19). All of the above processes have been and are being used. However) considerable research is being conducted to optimize these processes, as well as to explore innovative treatments for the removal and destruction of solutes from contaminated environments. This paper describes one such innovative treatment process, currently being tested in Miami, FL.
High-Energy Electron Irradiation High-energy electron accelerators have been used for years in industry for the cross-linking of polyethylene, the polymerization of lubricants, and the vulcanization of rubber. The number of applications has grown to include treatment for food preservation and the sterilization of medical instruments (20). One of the most promising uses for this evolving technology is for the treatment of hazardous wastes prior to discharge to the environment, or as a remediation technique for already contaminated waters. Although early studies with high-energy electrons showed the process to be effective for the disinfection of wastewater sludges (21-24), only limited studies were conducted with respect to the removal of toxic organic chemicals from aqueous-based systems (25-31). The conceptual basis for the use of high-energy electrons for the treatment of toxic organic compounds was presented in 1975 (32) followed by a direct comparison to the ozone process (33). However, the application of these concepts, as it relates to high-energy electron irradiation, was not explored in any detail. More recently) the use of highenergy radiation for the treatment of wastewater has been reviewed (34), attesting to the renewed interest in exploiting this technology for the treatment of industrial) municipal, and agricultural wastewater.
00 13-936X/92/0926-0144$03.00/0
0 1991 American Chemical Society
