Organic compounds in water Determination is essential for management and environmental control
Walter M. Shackelford David M. Cline Environmental Protection Agency Research Triangle Park. N. C. 27711
As the complexity of the chemical makeup of consumer products increases, the problems of containing and treating the wastes of modern society continue to grow. As population growth continues, the need for that most basic of all commodities, clean water, increases. The farm, the factory, and the home all require supplies of clean water, and each, to a varying degree, contributes to the contamination of water with toxic organics.
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To be alert to possible health threats and to protect our ability to recycle our water resources, we must rely on the collection and management of data from the chemical analysis of a wide variety of water sources. To ensure that the data are comprehensive, analytical methods must address the broadest range of compounds possible, and samples should represent a wide range of sources. Such a survey was called for in an ES&T feature article in 1977 ( I ) . Although no survey of the recommended magnitude has been attempted, approximations of the distribution of toxic organic substances in water can be made by bringing together data gathered in studies conducted by the regulatory community and by researchers
working in the field (2-4). Before we can use existing environmental protection resources, we must know the distribution of organic chemicals in water. The allocation of resources to correct such incidents as fish kills, grossly polluted rivers, or the damage caused by toxic waste dump sites is easily justified. More difficult decisions are required in determining what substances will be the object of intensive studies on exposure assessment, treatability, or toxicity. The number of known chemicals involved in manufacturing approaches 60,W;the number of byproducts and degradation products is unknown. To learn about and to control the quality of our water, we must know what kinds of organic
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chemicals are present. Three basic areas are critical for our understanding of the distribution of organics in water: Analysis methods must be comprehensive enough that the broadest range of compounds possible can be detected. Information management systems are needed that can make it possible to evaluate the vast quantities of data that are collected. Statistically valid surveys must be conducted to provide samples that are representative of the environment to be studied.
Analytical survey methods Over the past 10 years, it has been recognized that the scope of organic contaminants found in water is limited only by the analytical techniques used for measurement. The lack of adequate survey methods to detect and identify unknown compounds that are not eluted from the gas chromatograph, for example, precludes the analysis of 80-90% of the total organic carbon that is contained in water samples (1, 4). Most of the unanalyzable portion is composed of humic materials, carbohydrates, and other nontoxic materials from the decomposition of living matter. Until methods are developed to survey those remaining compounds that may be toxic, however, the determination of distributions will be severely limited. There are two broad categories of chemical analysis for those compounds that can be surveyed by available methods (5).Large numbers of samples are analyzed annually for target lists that usually include the priority pollutants or other regulated compounds. This category can be further broken down into those samples that are analyzed by gas chromatography (GC) with nonselective detectors (for example, flame ionization or electron capture) and those that are analyzed by gas chromatography-mass spectrometry (GUMS) with computer-controlled data acquisition and data analysis. A smaller number of samples are analyzed to determine all organic compounds present. GUMS is the analysis tool of choice for this more comprehensive analysis category. Although different sample workup procedures can either increase or decrease the range of compounds considered, the major difference in the two GUMS analyses is in the interpretation and handling of raw data. In a survey, an attempt is made to identify each observed component, generally by computer matching with a library of reference spectra. In target analysis, the same computer matching
takes place, but the reference library usually is limited to the 114 organic priority pollutants. One advantage of the use of computerized GUMS is that a target analysis can later become a survey analysis simply by enlarging the scope of the reference library and rematching (6). In archiving the final results, the difference in data handling is even more pronounced. The results of the analyses of target compounds find their way to one of EPA’s large data bases. The results of survey analyses are stored locally or perhaps published in a study of some small part of the global water environment. Regardless of the significance of such a study, a greater significance can be realized if the data are combined or compared with those of other studies. From such a combination, environmental planners can observe the total state of water quality as opposed to viewing only small pieces of the picture.
Information management Those who observe the data from environmental analysis laboratories realize that the ability to measure pollutants has outstripped the efforts to manage the data. Although the observation of a broad array of anthropogenic chemicals in water is in itself significant, it is necessary to use information management techniques to bring together many observations to highlight numerous significant problems. In addition, finding the intersection of several dimensions of data descriptors, such as concentration, water type, and geographical location for each pollutant, can enhance the importance of each finding. Knowing the frequency of Occurrence and range of concentration for each pollutant within different descriptor groups gives decision makers a basis for comparing exposure threats. EPA used the frequency of occurrence of specific toxic pollutants in water as one factor in determining the chemicals on lists of target compounds for regulating industrial wastewater and drinking water (7, 8). Interest in collecting environmental data for characterizing water began in the early 1970s as an effort to tie together the work of researchers independently studying localized water contamination problems. Although data bases of monitoring data existed at the time, most were of a narrow scope, limited, for example, to pesticides. In 1974 the Commission of the European Communities published a comprehensive list of organic chemical contaminants; it contained almost 300 references (3). In 1976 EPA compiled a computer data base of more than 6000 references to almost 1300 compounds
cited in the literature and in unpublished survey data (2). A review of the literature in 1982 revealed no new comprehensive compilations of survey data after those of the 1970s (4). Three large data bases have been compiled to define the extent of toxic organics found in water. l b o data bases are limited to monitoring data for specific target compounds and give distributions based only on a limited set of pollutants. EPA continutes to invest a considerable effort in building and maintaining a data base of monitoring data called STORET (storage and retrieval) (9). Effort was devoted also to a data base of survey data called WaterDROP (Distribution Register of Organic Pollutants), which is no longer available (10, 11).In addition, the Commission of the European Communities developed a data base composed of 65,000 industrial chemicals (12, 13). The STORET system is a massive collection of environmental data kept on line by EPA for use by environmental officials at all levels of government. Data contained in this program include water quality characteristics such as biological oxygen demand, total organic carbon, dissolved oxygen, specific toxic organic chemicals including pesticides and priority pollutants, and inorganic chemicals. Data are included from a variety of sample matrixes, such as water, sediment, and tissue. Descriptive data include weather conditions, sampling locations, dates, and other qualifiers that are used in mapping contaminated bodies of water. Some 80 million data points are included in STORET, which will be the agency’s repository of water quality data for the foreseeable future. STORET is useful to regulators and for mapping water quality, but it does not allow determination of the distribution of all organic substances in water because input is limited to a specific list of compounds. Although new compounds may be added, reporting by the many field stations that enter data is generally limited to specific regulated compounds. Generalized conclusions about the range and frequency of the occurrence of organics in water cannot be made because any results would be highly skewed from the specific monitoring data. A recent report deals with the use of STORET for determining the distribution and concentration of the 114 organic priority pollutants in the United States. The report also lists pitfalls in data interpretation (14).
European network The European Commission’s ECDIN (Environmental Chemicals Data and Environ. Sci. Technol., Vol. 20, No. 7, 1966
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Information Network) is available worldwide through such networks as EURONET DIANE and TYMNET. The scope of ECDIN is limited to industrial chemicals, but the environmental data included have greater breadth than those in other collections. Not only are environmental monitoring data available, but environmental transport and fate information are offered as well. Both ECDIN and STORET continue to he used because of their demonstrated ability to serve the needs of a diverse community of users. STORET provides mapping capabilities for regulated chemicals and permits a quick determination of the success of the regulation process. ECDIN likewise off& a ready reference to the immediate problems of industrial chemicals. Unforiunately, neither data base can present a comprehensive picture of the toxic chemicals in water because thev are limited to target compounds.
confidence to be put in any value. The analytical method should be included as a descriptor along with geographical information and water type. F i y , the system should permit text searching to aid the user in devising queries.
National water surveys Securing the m u r c e s to carry out a comprehensive survey of all the bodies of water in the United States may never be possible, but there have been nationwide studies of major water categories. Industrial wastewater has been under continuous scrutiny for specific organic compounds, the priority pollutants, since 1977 (7). Drinking water surveys also have been conducted (16). And al-
though most have been l i i t e d to the study of purgeable compounds, as many as 460 componnds were identified in one sample concentrate (17). EPA has done a national survey of ambient waters, f& tissue, and sediment (R. L. Greenspun, unpublished data), as well as specific areas such as the Great Lakes region (18). The programs at landfffl waste sites are beginning to give a picture of leachate content and the hazards to groundwater (19). A g d approximation of a survey of all waters would be possible as a result of l i i g the information gathered in these surveys. The open literature continues to be a source of information on the OCCUI-
WaterDROP WaterDROP, which is no longer carried by any on-line data base management system, was designed by EPA to supply all information necessary to describe the distribution of organic compounds found in water. It was to allow worldwide access to information on a wide range of water t y p , from drinking water to municipal sewage. Before being entered into the system, a distinct confidence rating was given to each entry This was to aid the user in judging the appropriateness of the data for a particular use. The comprehensiveness of WaterDROP depended on the range of compounds reported in each analysis. WaterDROP was an attempt to solve this problem hy including data from open literature reports and mearcb studies that are not normally reached by the STORET reporting network. WaterDROP was designed to run on the Chemical Information System at EPA and the National Institutes of Health. It took advantage of the access offered there to many other data bases, such as the Structure and Nomenclature Search System and TOXLINE. U p dates to the data base stopped in January 1980, and its use declined rapidly thereafter. As recently as 1982, bowever, its use in an environmental emergency was reported (15). It is evident from this discussion of previously created data bases that a number of characteristics could aid in the building of new data bases devoted to determining the distribution of organics in water. The range of entries should not be bounded hy a predetermined set of target compounds. The user should have some measure of the 654
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rence and distribution of organic compounds. A 1982 review in two parts lists 328 references on the Occurrence and fate of organic compounds in water (4, 20). Categories of water include waste dump leachates, rural and urban runoff, municipal and industrial effluents, and drinking water. A series of reviews in the J o u m l of the Ubrer Pollution Control Federation gives a complete picture of the effort to characterize waters of all types in the 1980s (21-25). More than 100 papers are cited between 1983 and 1985 for the general analysis of organics in water. Also included are papers that deal with the fate and transport of organic chemicals.
What the data tell us The failure to reconcile target compound lists with the realities of the environment can cause much effort to be expended looking for compounds that may not be present while possible threats go u~oticed.The results of a nationwide study of wastewater from a wide variety of industries and publicly owned treatment works (F"lWs) illustrates this point (6, 7). In this study, some 4ooo wastewater samples from 40 industrial categories and POTWs were examined for the 114 organic priority pollutants. The analytical method used was GClMS with computer control for identification of the
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priority pollutants. The data acquired for each sample contained information on a l l other organic compounds that were amenable to the sample workup and GC conditions as well as the priority pollutants. Once the data were analyzed for the priority pollutants, they were subjected to computer matching to determine the componnds in each sample that were not priority pollutants. Statistics were compiled on the compounds tentatively identified by matching both a reference spectrum and GC retention data. Silar statistics also were kept for those compounds that did not match any reference spectrum. Confirmation of computer-matched tentative identifications by reanalysis of sample extracts showed that the confidence level for any given match was about 70% (6). Figure 1 shows the relationship between the frequency of occurrence of priority pollutants and the frequency of occurrence of other compounds found in the study. Among the 50 most freqnently occurring compounds overall, only 14 are priority pollutants. For the POTWs, 16 priority pollutants are in the top 50, and the distribution of the top 14 priority pollutants is essentially the same as that for the composite. For two industrial categories-petroleum refining and iron and steel-the distribution of priority pollutants among the other compounds is different. In any industrial category, the range of chemicals found was smaller than the total range of chemicals across all the categories studied. This illustrates two points. First, although there are some priority pollutants that are important in each case, they make up only 25 % of the 50 most frequently occurring Compounds. Second, the profiles of individual industrial categories are different from one another and from the composite of wastewater samples. If the classes of observed compounds are compared with the classes sought in targa analyses, the difference in target compounds and the compounds actually found are more easily seen. Figure 2 shows some of the largest compound classes, in frequency of occurrence and in numbers of class members identified. There are whole classes of observed compounds that contain no priority pollutants. Further examination of the statistics of Occurrence of individual compounds shows that only 1% of the total number of compounds identified account for more than 32% of the total number of compound occurrences. The other side of the coin, however, is that of the total number of discrete compounds identified, 40% account for only 2% of the total number of compound occurEnviron. Sci. Technol., VoI. 20. NO. 7. 1986
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rences. This bears out what was Seen in earlier data bases that contained data on ambient water from surface water, drinking water, and groundwater (2.3) and has also been predicted (26). A similar computer matching study of surface water, sediment, and tissue showed similar profiles (R. L. Greenspun, unpublished data). Better resolution of the statistics can be obtained by taking advantage of information management resources. As was seen in Figure 1, the occurrence of prionly pollutants varies across industrial categories and is very different from the composite. Figure 3 shows all compounds that were identified at least twice matched with their respective industrial categories and weighted such that the uniqueness of a compound’s OCcurrence within an industry and its frequency of occurrence within that industry contribute to the sue of the peak. lhble 1 lists some of the data that were used to develop Figure 3. The 10 compounds with the highest peaks are shown, along with the industries in which they are found. Overall frequency of occurrence and frequency of occurrence in a specific industry are compared in the table and the figure. For example, phenyltridecane is found in industrial wastewater five times in all, but all five occurrences are in the soap and detergent industry. A final example of the distribution of organics involves those compounds that are observed routinely but are not identified because of the lack of reference spectra and, ultimately, the lack of resources for their identification.
In the study of industrial wastewater using packed GC columns, some 3000 spectra were noted to have occurred more than once within short retention times. The apparent frequency-of-occurrence profile generated by this set of compounds shows the same behavior as that of the identified compounds: Most compounds are seen only a few times, and a few compounds are seen many times. This behavior reinforces the point that without the use of information management the implications of the data cannot be appreciated. Looking ahead
If researchers know the distribution of organic compounds in water they are better able to use available resources for environmental protection. The information available from widely used computer data bases consists primarily of the results of target analyses for specific compounds and thus does not give us forewarning of new problems. There are specialized data bases and literature reports that contain survey data, but they are not linked to a generally available system. Examination of representative data bases shows that lists of target compounds do not reflect the whole of organic contaminants in water. These data bases also demonstrate that a few compounds are found very frequently but that most compounds are found in very few samples. Information management can highlight problems in specific areas that are lost in composite data. Recent advances in computer hardware and software systems have brought sophisticated data management capabilities to all levels of environmental scientists and managers. How we make use of these capabilities will determine the efficiency of our response to future environmental problems. Acknowledgment We thank William T. Donaldson of EPA in Athens, Ga.. and Robert Greenspun and T h o m a s Fielding of EPA in Washington.
( 6 ) Shackelford. W. M. ct al. Anal. Chim. A m 1983, 146. 15-17. (7) Keith. L. H.: Tclliard. W. A . Envim,!. Sri. Rchnol. 1979, 13.416-23. (8) Cotruvo. J . A . Environ. Sei. Techno/. 1981, 15. 268-214. (9) STORET User Handbook: Office of Information and Resources Management: EPA: Washington. D.C.. 1982. ( I O ) Garrison, A . W.;Keith. L. H.: Shackelford. W. M. I n Aquaric Polluronrs: Tmnrformation and Binlofirol EBpn.5; Hutzinger, 0 . :Van Lelyveld. I . H.: Zoeternan. B.C.J.. Eds.: Pereaman Press: Amstcrdam. the Netherland;. 1978: pp. 39-68. ( 1 1 ) Carson. B. L. et al. In Advances in the ldenrificnrion ond Analwis of Orpanic Pollulonlr'in Warcr: Keith.L. H:. Ed.: Ann Arbor Science: Ann Arbor, Mich.. 1981: Vol. 2. pp. 497-525. (12) Hushon. J . M . ; Powell. I . : Town. W.G. 1. Chem. lnf Cnmpur. Sci. 1983,23, 38-43. (13) Hushon, J. M. et al. J. Chrm. lnf Cnmpur. Sci. l984,24, 148-52. ( 1 4 ) S t a p l e s , C . A . ; Werner. A . F.: Hoagheem. T. J. Environ. ii,xicxicol. Chon
1985.4, 131-42. ( 1 5 ) Milne. G.W.A. el al. Scimcr 1982, 215.
371-75.
(16) Brass. H. J . et al. In Drinkin8 Wmrr Qunliry Enhoncemenr rhrouph Source pro^
R . B.. Ed.: Ann Arbor Science: Ann Arbor. Mich., 1977: pp. 393416. (17) Coleman. W. E. et al. Environ. Sci. Rchno/. 1981, 14. 576-88. (18) Bahnick, D. A , : Markee. T. P J. G r m Lnkrr Re.?. 1985. ~ 11. ~1 4 3 -.5.. ~~ ~ (19) Rcinhard, M . ; Goodman, N. L.: Barker, J. F. Environ. Sci. Jechnol. 1984. 18. 953I ~ t l i ~ Pojasek. n;
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(20) Bedding. N . D. et al. Sci. iiirol Environ. 1983.26, 255-312. (21) DcWalle. F. B. et al. J. Wirier Pollur. C m r m l Fpd. 1981, 53, 659-74. (22) DeWalle, F. B. et al. 1. Wurer Pollur. Conrrol Fed. 1982.54, 555-76. (23) Adarns. V. D.;Watts. R. I.: Pills. M. E. J . Wirer Pollur. Conrrol Fed. 1983.55, 577-
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(24) Adams. V. D.; Watts, R. I . ; Pills, M. E. J. WUIPT Pollur. Control Fed. 1984, 56. 52244. (25) Adams. V. D.:Watts. R. J.: Pitts, M. E. J. Wnrvr Pnllur. Conrrol Fed. 1985.57, 46393. (26) Schaeffer. D.J.: Jarnardan. K. G. Bull. Enviro,!. Conram Toxirol. 1980, 24, 21 I-
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Before publication, this article was reviewed for suitability as an ES&T feature by Lawrence H. Keith of Radian Corporation, Austin, Tex. 78166: and V. Dean Adams of Tennessee Technological University, Cmkesville, Tenn. 38505. References (1) Donaldson. W. T. Environ. Sci. Rchnol. 1977, 11. 348-51. (2) Shackelford. W. M.: Keith. L. H. "Frequency of Organic Compounds Found in Water." EPAl600-4-76-062: EPA: Washington. D.C.. 1976. ( 3 ) "Listing of Organic Chemicals Found in Water." Europ-Coat Project M b : 2nd ed.: Commission af the European Communities: Brussels. Belgium. 1974. (4) Bedding, N . D. et al. Sci. i i m l Envimn. 1982,ZS. 143-57. ( 5 ) Budde. W. L.: Eichelbergcr. J . W, Anal. Chrm. 1979,51, 567-73 A .
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