1、American Petroleum Institute EFFECTS OF SAMPLING AND ON THE MEASUREMENT OF OF INTRINSIC BIOREMEDIATION: LABORATORY AND FIELD STUDIES ANALYTICAL PROCEDURES GEOCHEMICAL INDICATORS Health and Environmentai Sciences Department Publication Number 4657 November 1997 American Petroleum P Institute American
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10、API/PETRO PUBL 4b57-ENGL 1997 0732290 Ob04524 02T = Effects of Sampling and Analytical Procedures on the Measurement of Geochemical Indicators of Intrinsic Bioremediation: Laboratory and Field Studies Health and Environmental Sciences Department API PUBLICATION NUMBER 4657 PREPARED UNDER CONTRACT BY
11、: CH2M-H ILL ST. LOUIS, MO 63102 10 SOUTH BROADWAY NOVEMBER 1997 American Petroleum I Institute - STD.API/PETRO PUBL 4b57-ENGL I1997 = 0732290 ObO?l525 Tbb FOREWORD API PUBLICATIONS NECESSARILY ADDRESS PROBLEMS OF A GENERAL NATURE. WITH RESPECT TO PARTICULAR CIRCUMSTANCES, LOCAL, STATE, AND FEDERAL
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15、publisher Contact the publisher; API Publishing Services, 1220 L Street, N. W, Wmhington, D.C. 20005. Copyright Q 1997 American Petroleum Institute . 111 STD-APIIPETRO PUBL 4b57-ENGL 1997 m 0732290 Ob0452b 9T2 m ACKNOWLEDGMENTS THE FOLLOWING PEOPLE ARE RECOGNIZED FOR THEIR CONTRIBUTIONS OF TIME AND
16、EXPERTISE DURING THIS STUDY AND IN THE PREPARATION OF THIS REPORT - Bruce Bauman, Health and Environmental Sciences Department Roger Cl 2) elevated levels of bicarbonate, methane, and ferrous iron; and 3) geochemical conditions that are in dramatic disequilibrium with the atmosphere. Based on theore
17、tical considerations, one would anticipate that the geochemistry of a groundwater sample from a geochemically reduced zone would be altered by sampling techniques that involve contact between the groundwater and the atmosphere. Such alterations in concentrations of dissolved oxygen, ferrous iron, an
18、d methane were confirmed in the project through both the laboratory and field studies. COWARTSON OF SAMPLING METHODS In the laboratory study, samples of known geochemical composition were collected from a sealed tank by three sampling methods: 1) a micropurging sampling method with a low flow submer
19、sible pump, 2) a variation of the micropurging sampling techniques with a peristaltic pump, and 3) a bailer. All sampling techniques resulted in some introduction of DO, and some loss of methane and ferrous iron. The micropurging method with the submersible pump consistently introduced the least bia
20、s. The most bias was introduced with the bailer. To further compare the effects of sampling methods, groundwater samples were collected from multiple wells at two different field sites. Wells were sampled using the micropurging method ES- 1 STDmAPIIPETRO PUBL Yb57-ENGL 1997 m 0732290 ObOY533 032 m w
21、ith a low flow submersible pump, and were then sampled with bailers. Results generally were consistent with the laboratory studies, particularly with respect to the greater loss of ferrous iron and methane with the bailer method. A limited amount of field work was done to evaluate data collection me
22、thods involving no purging of monitoring wells. For wells in zones geochemically affected by hydrocarbon releases, downhole DO probe measurements on unpurged monitoring wells often yield DO readings that are higher than the DO of formation groundwater. Of the sampling methods examined, the no purgin
23、g method resulted in the greatest loss of iron and methane from groundwater in geochemically reduced zones. COMPARISON OF ANALYTICAL METHODS During the field studies, a comparison of field and commercial laboratory analytical methods for nitrate, sulfate, iron, and alkalinity was made. Field methods
24、 are of interest because the rapid sample analyses reduce the potential for changes in composition during shipment and storage, and allow for “real time” data evaluation in the field. Generally, there was fairly good correlation among data produced using the two methods, suggesting that field method
25、s are generally viable alternatives to use of a commercial laboratory. CONCLUSIONS While certain groundwater sampling techniques can alter the samples geochemistry, these changes may or may not significantly affect data interpretation. Groundwater in hydrocarbon bearing zones often has a geochemistr
26、y radically different than background groundwater as a result of naturally occurring hydrocarbon biodegradation. These general shifts in geochemistry can be readily detected using conventional groundwater monitoring and sampling techniques. If the objective is simply to provide geochemical evidence
27、of hydrocarbon biodegradation activity, then any of the groundwater monitoring and sampling techniques examined in this study generally will suffice, as long as they are consistently applied across a particular site. It is typically the differences among multiple measurements at a site that are impo
28、rtant. If, on the other hand, the geochemical data are used in quantitative projections of plume migration (e.g., input parameters in BIOPLUME IIi modeling), the potential biases in geochemical data ES-2 STD*API/PETRO PUBL 4657-ENGL 1997 W 0732290 Ob04534 T79 W introduced through sample collection s
29、hould be considered in scoping data collection activities. The potential for sampling methodology to significantly affect a quantitative intrinsic bioremediation evaluation will be highest on sites where the dominant biodegradation mechanisms are aerobic respiration, iron reduction, and/or methanoge
30、nesis. in summary, there are several groundwater sampling and analytical methods that may be appropriate for measuring geochemical indicators of intrinsic bioremediation. The methods vary in accuracy, level of effort, and cost. The choice of the best method for a given application should be based on
31、 project-specific and site-specific considerations, particularly the specific manner in which the data are to be used. A companion document (CH2M HILL, 1997) provides guidance on the selection and use of field sampling and analytical methods for measuring geochemical indicators of intrinsic bioremed
32、iation. ES -3 STDaAPIlPETRO PUBL 4b57-ENGL L997 W 0732290 Ob04535 905 Section 1 INTRODUCTION This report, sponsored by the American Petroleum Institute (MI), presents the results of laboratory and field studies on field methods for the measurement of geochemical indicators of intrinsic bioremediatio
33、n. Intrinsic bioremediation is a risk management strategy that relies on naturally occumng biodegradation for mitigation of the potential risks posed by subsurface contaminants. Various technical articles and protocols offer guidance on the groundwater parameters and properties that should be measur
34、ed to characterize intrinsic bioremediation of petroleum hydrocarbons. These include dissolved oxygen (DO), nitrate, sulfate, ferrous iron, methane, carbon dioxide, alkalinity, oxidationheduction potential (OW), pH, conductivity, and temperature. Measurement of these parameters is being performed at
35、 an increasing number of petroleum hydrocarbon sites. However, there is a lack of guidance on appropriate sampling and analytical procedures to ensure that these measurements generate quality data. This lack of guidance is cause for concern because the extent to which intrinsic bioremediation is ult
36、imately embraced will depend, to a large degree, on the valid characterization of site conditions. The project consisted of a laboratory study, which allowed comparison of sampling methods under controlled conditions, as well as field studies, which allowed verification of laboratory results on samp
37、ling methods under actual.field conditions. The field studies also incorporated a comparison of commercial laboratory and field analytical methods. Field analytical methods are of interest because their use makes possible rapid sample analyses, thus reducing the potential for changes in the composit
38、ion of the sample during sample shipment and storage, and allowing for “real time” data evaluation in the field. Based on these studies, a companion document (CH2M HILL, 1997) was prepared to provide guidance on the selection and use of field sampling and analytical methods for measuring geochemical
39、 indicators of intrinsic bioremediation. 1-1 STD.API/PETRO PUBL 4657-ENGL 1997 0732290 O604536 841 The primary objective of this report is to document and discuss the findings of the laboratory and field studies. This report should not be interpreted as providing endorsement of a particular sampling
40、 or analytical method. Guidance on the selection and use of sampling and analytical methods used to support intrinsic bioremediation site characterizations is presented in the companion document (CH2M HILL, 1997). Site data on indicators of intrinsic bioremediation can be used in a variety of ways,
41、ranging from very qualitative uses (e.g., comparison to background data) to very quantitative uses (e.g., input parameters to numerical fate and transport models). The ultimate data use dictates the data quality objectives. The data quality obtained through the various sampling and analytical method
42、s, and effects on data use, are discussed in this report. This report should not be interpreted as providing endorsement of any particular data use. The field studies described in this report were conducted at petroleum hydrocarbon sites, and the report focuses on applications of intrinsic bioremedi
43、ation at petroleum hydrocarbon sites. However, the observations and findings presented will generally be applicable to any site where biodegradable organic constituents exist. 1-2 Section 2 BACKGROUND Microbial metabolism of petroleum hydrocarbons has predictable geochemical consequences (Wilson et
44、al., 1994). For example, respiration of hydrocarbons may result in the loss of oxygen, nitrate, and sulfate, and the production of ferrous iron. Petroleum hydrocarbons may also be biodegraded through an anaerobic process that results in the production of methane (i.e., methanogenesis). Measuring the
45、 trends in the distribution and concentration of these and other parameters can be used qualitatively to establish hydrocarbon biodegradation activity. Data on the spatial distribution of these parameters, together with hydrogeologic and stoichiometric data, are also sometimes used to support quanti
46、tative estimation of contaminant biodegradation rates and projection of plume migration. These uses of geochemical data will be valid only to the extent that these parameters are representative of geochemical conditions in the groundwater system sampled. Key considerations in the collection of repre
47、sentative geochemical data are outlined below. GEOCHEMICAL CONSIDERATIONS In recent years, it has become widely recognized that microorganisms can have profound effects on groundwater quality (Chapelle, 1993). This is particularly true where large masses of biodegradable organic compounds (e.g., pet
48、roleum hydrocarbons) are present in the vadose and groundwater zones. Hydrocarbon biodegradation involves microbiologically mediated oxidation coupled with reduction of an electron acceptor through the biological process of respiration. The reduction of highly oxidized electron acceptors (e.g., DO)
49、results in an overall decrease in the oxidizing potential of the groundwater. Once species with the highest oxidizing potential are exhausted, the next most highly oxidized electron acceptor is reduced. This process continues and the oxidizing potential of the groundwater system is progressively reduced. A general sequence of electron acceptor utilization and lowering of the oxidizing potential of the groundwater is as follows: 2- 1 - STD.API/PETRO PUBL 4657-ENGL 1997 m 0732290 Ob04538 bL4 m 1. Consumption of D
